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Title: Discoveries and Inventions of the Nineteenth Century
Author: Routledge, Robert
Language: English
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Copyright Status: Not copyrighted in the United States. If you live elsewhere check the laws of your country before downloading this ebook. See comments about copyright issues at end of book.

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[Illustration:

  PLATE I.

  THE GREAT WHEEL IN ACTION.
]



                       DISCOVERIES AND INVENTIONS

                                 OF THE

                           NINETEENTH CENTURY


              Who saw what ferns and palms were pressed
              Under the tumbling mountain’s breast,
              In the safe herbal of the coal?
              But when the quarried means were piled,
              All is waste and worthless, till
              Arrives the wise selecting Will,
              And, out of slime and chaos, Wit
              Draws the threads of fair and fit.
              Then temples rose, and towns, and marts,
              The shop of toil, the hall of arts;
              Then flew the sail across the seas
              To feed the North from tropic trees;
              The storm-wind wove, the torrent span,
              Where they were bid the rivers ran;
              New slaves fulfilled the poet’s dream,
              Galvanic wire, strong-shouldered steam.

                                                  EMERSON.



                       DISCOVERIES AND INVENTIONS
                                 OF THE
                           NINETEENTH CENTURY


                                   BY

                        ROBERT ROUTLEDGE, B.Sc.,
 SOMETIME ASSISTANT EXAMINER IN CHEMISTRY AND IN NATURAL PHILOSOPHY TO
                        THE UNIVERSITY OF LONDON


                           THIRTEENTH EDITION
             REVISED AND PARTLY RE-WRITTEN, WITH ADDITIONS


          CONTAINING FOUR HUNDRED AND FIFTY-SIX ILLUSTRATIONS


                                 LONDON
                   GEORGE ROUTLEDGE AND SONS, LIMITED
                         BROADWAY, LUDGATE HILL
                                  1900



                                PREFACE.


In the following pages an attempt has been made to present a popular
account of remarkable discoveries and inventions which distinguish the
XIXth century. They distinguish it not merely in comparison with any
previous century, but in comparison with all the centuries that have
preceded, in regard to far-reaching intellectual acquisitions, and to
material achievements, which together have profoundly affected our ways
of thinking and our habits of life. In the latter, the enormously
increased facilities of locomotion and international communication due
to railways and steam navigation have wrought the greatest changes.
These inventions depending primarily upon that of the steam engine, this
first claims our notice, although properly assignable to a period
preceding our era by a few years. Again, much of our material
advancement is connected with improvements in the manufacture of iron
and its applications in the form of steel, which have been especially
the work of the last half of the century. So great has been the progress
in this department, that for the present edition it has been found
necessary to re-write altogether the article devoted to it. Our social
conditions have also been greatly modified by the celerity of verbal
intercourse afforded by the telegraph and the telephone, and these
inventions have received appropriate notice in this work. In every
branch of science also we have reason to be proud of the discoveries our
era can claim, for they vastly excel in number and are not inferior in
range to those of all the ages taken together. From so large a field,
selection was of course necessary; and the instances selected have been
those which appeared to some extent typical, or those which seemed to
have the most direct bearing on the general advance of our time. The
topics comprise chiefly those great applications of mechanical
engineering and arts, and of physical and chemical science, in which
every intelligent person feels concerned; while some articles are
devoted to certain purely scientific discoveries that have excited
general interest.

The author has aimed at giving a concise but clear description of the
several subjects; and that without assuming on the part of the reader
any knowledge not usually possessed by young persons of either sex who
have received an ordinary education. The design has been to treat the
subjects as familiarly as might be consistent with a desire to impart
real information; while the popular character of the book has not been
considered a reason for regarding accuracy as unnecessary. On the
contrary, pains have been taken to consult the best authorities; and it
is only because the sources of information to which the author is under
obligation are so many, that he cannot acknowledge them in detail.

The present edition has been revised throughout, and such changes have
been made as were required to bring the matter into accordance with the
progress that has taken place since this book was first published in
1876. But details given in the former editions have at the same time
been retained where they served to indicate the successive stages of
improvement. It would, for example, be impossible in a section on steam
navigation, to omit some notice of the _Great Eastern_, and therefore
the drawings and the account of the construction of that remarkable ship
that appeared in the first edition, have been left with but slight
alterations in the present volume, although the vessel has since been
broken up. On the other hand, two sections are devoted to projects which
the XIXth century has not seen realised; but the XXth century will in
all probability shortly witness the completion of one or other of the
great canal schemes; and if the first submarine tunnel is destined not
to be one connecting England with the Continent, it will be one uniting
Great Britain with her sister isle.

      1899.

                  *       *       *       *       *

For permission to make use of illustrations in this volume the author’s
and publishers’ thanks are due to the several proprietors of _The
Graphic_ (for Plates I., XI., and XII.)—of _The Engineer_ (for sketch
design of the Great Wheel, map and views of the Tower Bridge)—of _The
Scientific American_ (map of North Sea Canal); also to Mr. Walter B.
Basset (for Plate V.)—to “The Cassier Magazine Company” (for Edison’s
Kinetographic Theatre and the Hotchkiss Gun)—to “The Century Company”
(for portrait of M. Tesla, from a photograph by Sarony)—to “The
Incandescent Gas Light Company” (for cuts of burners, etc.)—to _The
Engineering Magazine_, and _The Engineering News_, both of New York—to
the Remington Company—to Mr. W. W. Greener, of Birmingham (for cuts of
rifles, etc., from his comprehensive book on “The Gun”)—to _The
Photogram_, Limited—to the Proprietors of _Nature_—to the Linotype
Company—and to Captains Hadcock and Lloyd (for illustrations of modern
artillery from their great work on the subject).



                               CONTENTS.


                                                                    PAGE

 INTRODUCTION                                                          1

 STEAM ENGINES                                                         3
     THE LOCOMOTIVE                                                   14
     PORTABLE ENGINES                                                 24
     THE STEAM HAMMER                                                 25

 IRON                                                                 29
     IRON IN ARCHITECTURE                                             72
     BIG WHEELS                                                       81

 TOOLS                                                                85
     THE BLANCHARD LATHE                                              96
     SAWING MACHINES                                                  98

 RAILWAYS                                                            101
     THE METROPOLITAN RAILWAYS                                       114
     THE PACIFIC RAILWAY                                             116
     INCLINED RAILWAYS                                               125

 STEAM NAVIGATION                                                    129
     RIVER AND LAKE STEAMBOATS OF AMERICA                            144

 SHIPS OF WAR                                                        149

 FIRE-ARMS                                                           169
     THE MILITARY RIFLE                                              178
     RIFLED CANNON                                                   190
     MACHINE GUNS                                                    218

 TORPEDOES                                                           227

 SHIP CANALS                                                         249
     THE SUEZ CANAL                                                  251
     THE MANCHESTER SHIP CANAL                                       262
     THE NORTH SEA CANAL                                             271
     THE PANAMA AND NICARAGUA CANAL PROJECTS                         272

 IRON BRIDGES                                                        276
     GIRDER BRIDGES                                                  280
     SUSPENSION BRIDGES                                              284
     CANTILEVER BRIDGES                                              291
     THE TOWER BRIDGE, LONDON                                        297
     THE GREAT BROOKLYN BRIDGE                                       303

 PRINTING MACHINES                                                   305
     LETTERPRESS PRINTING                                            306
     PATTERN PRINTING                                                321

 HYDRAULIC POWER                                                     324

 PNEUMATIC DISPATCH                                                  340

 ROCK BORING                                                         349
     THE MONT CENIS TUNNEL                                           351
     ROCK-DRILLING MACHINES                                          355
     THE CHANNEL TUNNEL                                              364
     THE ST. GOTHARD RAILWAY                                         371

 LIGHT                                                               380
     SOME PHENOMENA OF LIGHT                                         382
     VELOCITY OF LIGHT                                               384
     REFLECTION OF LIGHT                                             388
     REFRACTION                                                      397
     DOUBLE REFRACTION AND POLARISATION                              399
     CAUSE OF LIGHT AND COLOUR                                       408

 THE SPECTROSCOPE                                                    416
     CELESTIAL CHEMISTRY AND PHYSICS                                 436

 ROENTGEN’S X RAYS                                                   445

 SIGHT                                                               452
     THE EYE                                                         454
     VISUAL IMPRESSIONS                                              468

 ELECTRICITY                                                         481
     ELEMENTARY PHENOMENA OF ELECTRICITY AND MAGNETISM               483
     THEORY OF ELECTRICITY                                           487
     ELECTRIC INDUCTION                                              488
     DYNAMICAL ELECTRICITY                                           490
     INDUCED CURRENTS                                                502
     MAGNETO-ELECTRICITY                                             507
     THE GRAMME MAGNETO-ELECTRIC MACHINE                             511
     ELECTRIC LIGHTING AND ELECTRIC POWER                            519
     THE NEW ELECTRICITY                                             538

 THE ELECTRIC TELEGRAPH                                              547
     TELEGRAPHIC INSTRUMENTS                                         553
     TELEGRAPHIC LINES                                               572
     THE TELEPHONE                                                   581

 LIGHTHOUSES                                                         593

 PHOTOGRAPHY                                                         607
     PHOTOGRAPHY IN COLOURS                                          630

 PRINTING PROCESSES                                                  632
     STEREOTYPING                                                    632
     LITHOGRAPHY                                                     636
     OTHER PROCESSES                                                 640
     THE LINOTYPE MACHINE                                            645

 RECORDING INSTRUMENTS                                               653
     THE PHONOGRAPH                                                  665

 AQUARIA                                                             675
     THE CRYSTAL PALACE AQUARIUM                                     677
     THE BRIGHTON AQUARIUM                                           682

 GOLD AND DIAMONDS                                                   687
     GOLD                                                            687
     DIAMONDS                                                        696

 NEW METALS                                                          714

 INDIA-RUBBER AND GUTTA-PERCHA                                       724
     INDIA-RUBBER                                                    724
     GUTTA-PERCHA                                                    728

 ANÆSTHETICS                                                         731

 EXPLOSIVES                                                          740

 MINERAL COMBUSTIBLES                                                751
     COAL                                                            751
     PETROLEUM                                                       757
     PARAFFIN                                                        761

 COAL-GAS                                                            764

 COAL-TAR COLOURS                                                    781

 THE GREATEST DISCOVERY OF THE AGE                                   801

 NOTES                                                               811

 INDEX                                                               813



                         LIST OF ILLUSTRATIONS.


           FIG.                                                     PAGE

                Heading—Rain, Steam, and Speed (after Turner)          1

             1. Portrait of James Watt                                 3

             2. Newcomen’s Steam Engine                                4

             3. Watt’s Double-action Steam Engine                      5

             4. Governor and Throttle-Valve                            6

          4_a_. Watt’s Parallel Motion                                 8

             5. Slide Valve                                            9

             6. Section of Gifford’s Injector                         11

             7. Bourdon’s Pressure Gauge                              12

             8. Steam Generator                                       13

             9. Section of Locomotive                                 15

            10. Stephenson’s Link Motion                              17

         10_a_. G. N. R. Express Passenger Locomotive                 19

         10_b_. Joy’s Valve Gear                                      20

            11. Locomotive after Explosion                            22

            12. Hancock’s Steam Omnibus                               22

            13. Nasmyth’s Steam Hammer                                27

            14. Merryweather’s Steam Fire-Engine                      28

            15. A Foundry                                             29

            16. Aerolite in the British Museum                        31

            17. Blast Furnace                                         41

            18. Section and Plan of Blast Furnace (obsolete type)     42

            19. Section of a Reverberatory Furnace                    45

            20. Fibrous Fracture of Wrought Iron                      47

            21. Cup and Cone                                          49

            22. Section of Blast Furnace                              51

            23. Experiments at Baxter House                           58

            24. Bessemer Converter                                    63

            25. Model of Bessemer Steel Apparatus                     65

            26. Section of Regenerative Stoves and Open Hearth        68

         26_a_. Rolling Mill                                          71

         26_b_. The Eiffel Tower in course of construction            73

         26_c_. The Eiffel Tower                                      75

         26_d_. St. Paul Building, N. Y.                              77

         26_e_. Manhattan Insurance Co.’s Building in course of       79
                  erection

         26_f_. Manhattan Insurance Co.’s Building nearly completed   80

         26_g_. Original Design for the Great Wheel                   82

            27. Portrait of Sir Joseph Whitworth                      85

            28. Whitworth’s Screw Dies and Tap                        86

            29. Screw-cutting Lathe                                   87

            30. Whitworth’s Measuring Machine                         89

            31. Whitworth’s Drilling Machine                          91

            32. Whitworth’s Planing Machine                           93

            33. Pair of Whitworth’s Planes or Surface Plates          94

            34. Interior of Engineer’s Workshop                       95

            35. Blanchard Lathe                                       96

            36. Vertical Saw                                          98

            37. Circular Saw                                          99

            38. Pit-Saw                                              100

            39. Box Tunnel                                           101

            40. Coal-pit, Salop                                      102

            41. Sankey Viaduct                                       103

            42. Rails and Cramp-gauge                                104

            43. Fish-plate                                           105

            44. Section of Rails and Fish-plates                     106

            45. Conical Wheels                                       107

            46. Centrifugal Force                                    107

            47. Points                                               108

            48. Signal Box on North London Railway                   109

            49. Post Office Railway Van                              111

            50. Gower Street Station, Metropolitan Railway           115

            51. Map of the Route of Pacific Railway                  117

            52. Trestle Bridge                                       118

            53. American Canyon                                      119

            54. “Cape Horn”                                          121

            55. Snow Plough                                          122

            56. First Steam Railroad Train in America                123

            57. Railway Embankment                                   124

         57_a_. Train ascending the Rigi                             126

         57_b_. At the summit of the Rigi                            127

            58. The _Great Eastern_ at Anchor                        129

            59. Casting Cylinder of a Marine Steam Engine            131

            60. Screw Propeller                                      132

            61. Section of _Great Eastern_ Amidships                 134

            62. The _Great Eastern_ in course of construction        135

            63. The _Great Eastern_ ready for launching              136

            64. Comparative sizes of Steamships                      137

            65. The ss. _City of Rome_                               138

            66. The _Castalia_ in Dover Harbour                      140

            67. The same—End View                                    141

            68. Bessemer Steamer                                     142

         68_a_. A Whaleback Steamer, No. 85, built at West           146
                  Superior, Wisconsin

            69. H.M.S. _Devastation_ in Queenstown Harbour           149

            70. Section of H.M.S. _Hercules_                         151

            71. Section of H.M.S. _Inconstant_                       153

            72. Section, Elevation and Plan of Turret of H.M.S.      154
                  _Captain_

            73. H.M.S. _Captain_                                     155

            74. Diagram of H.M.S. _Captain_                          158

            75. Ditto                                                159

            76. H.M.S. _Glatton_                                     162

            77. H.M.S. _Thunderer_                                   163

            78. The _König Wilhelm_                                  165

         78_a_. The _Victoria_ leaving Newcastle-on-Tyne             166

         78_b_. Firing at Floating Battery                           168

            79. Krupp’s Works at Essen, Prussia                      169

            80. Trajectory of a Projectile                           174

            81. Diagram for Trajectory of a Projectile               176

            82. Muzzle-loading Musket and Rifles (obsolete           179
                  patterns)

            83. The Minié Bullet                                     181

            84. Greener’s Expanding Bullet                           182

            85. The Chassepot Rifle—Section of the Breech            183

            86. Section of the Martini-Henry Lock                    185

            87. The Martini-Henry Rifle                              186

            88. The Mannlicher Magazine Rifle                        188

            89. The Magazine and Breech of the Mannlicher Rifle      189

            90. 32–pounder, 1807                                     191

            91. Whitworth Rifling and Projectile                     193

            92. 600–pounder Muzzle-loading Armstrong Gun             194

            93. 35–ton Fraser Gun                                    195

            94. Section of 9–in. Fraser Gun                          196

            95. Millwall Shield after being battered with Heavy      200
                  Shot—Front View

            96. Rear View of the Millwall Shield                     200

            97. Comparative Sizes of 35 and 81–ton Guns              201

            98. Diagram of Velocities and Pressures                  205

            99. Elswick 4·7–in. Q. F. Gun on Pivot Mounting          207

           100. The Moncrieff Gun raised and ready for firing        209

           101. Moncrieff Gun lowered for loading                    209

           102. 68–ton Gun on Elswick Hydro-Pneumatic Mounting       211

           103. Mallet’s Mortar                                      213

           104. 32–pounder Krupp Siege Gun, with Breech-piece open   214

           105. The Citadel of Strasburg after the Prussian          215
                  Bombardment

        105_a_. The Shrapnel and Segment Shells                      217

        105_b_. The Gatling Gun—Rear View                            219

        105_c_. The Gatling Gun—Front View                           221

        105_d_. The Montigny Mitrailleur                             222

        105_e_. A Hotchkiss Gun                                      224

           106. Harvey’s Torpedo.—Working the Brakes                 227

           107. Submerged Torpedo                                    228

           108. Mode of Firing Torpedo                               230

           109. Explosion of Whitehead’s Torpedo                     231

           110. Effect of the Explosion of Whitehead’s Torpedo       232

           111. Experiment with a Torpedo charged with 10 lbs. Gun   233
                  Cotton

           112. Explosion of Torpedo containing 67 lbs. Gun Cotton   234

           113. Explosion of 432 lbs. Gun Cotton in 37 ft. Water     235

           114. The same in 27 ft. Water                             235

           115. Section of Priming Case and Exploding Bolt           236

           116. Harvey’s Torpedo                                     237

           117. The same                                             238

           118. The same                                             239

           119. Official Trial of “Harvey’s Sea Torpedo”             239

           120. Model of Submarine Guns                              240

           121. The Warner Experiment off Brighton                   241

           122. Portrait of M. Lesseps                               249

           123. The Sand-Glass                                       253

           124. A Group of Egyptian Fellahs and their Wives          254

           125. Dredges and Elevators at Work                        255

           126. Map of the Suez Canal                                256

           127. Port Saïd, the Mediterranean Entrance to the Suez    257
                  Canal

           128. Bird’s-eye View of Port Saïd                         258

           129. One of the Breakwaters at Port Saïd                  259

           130. Lake Timsah and Ismaïlia                             259

           131. Railway Station at Ismaïlia                          260

           132. The Viceroy of Egypt cutting Embankment              261

           133. Map of the Manchester Ship Canal, Western Portion    263

           134. Map of the Manchester Ship Canal, Eastern Portion    263

           135. A Cutting for the Manchester Ship Canal              265

           136. Blasting Rocks for the Manchester Ship Canal         266

           137. Manchester Ship Canal Works, Runcorn                 267

        137_a_. The French Steam Navvy                               268

        137_b_. The English Steam Navvy                              269

        137_c_. Sketch Map of the North Sea Canal                    271

           138. Britannia Bridge, Menai Straits                      276

           139. Diagram showing Strains                              278

           140. Ditto                                                279

           141. Girder                                               279

           142. Ditto                                                279

           143. Ditto                                                280

           144. Section of a Tube of the Britannia Bridge            281

           145. Albert Bridge, Saltash                               283

           146. Clifton Suspension Bridge, near Bristol              285

           147. Section of Shaft                                     286

        147_a_. Clifton Suspension Bridge, Niagara                   288

        147_b_. Living Model of the Cantilever Principle             291

        147_c_. Principal Dimensions of the Forth Bridge             294

        147_d_. Map of the Tower Bridge and its Approaches           299

        147_e_. The Tower Bridge                                     301

        147_f_. Sketch                                               302

           148. Newspaper Printing-Room                              305

           149. Inking Balls                                         306

           150. Inking Roller                                        306

           151. Diagram of Single Machine                            308

           152. Diagram of Perfecting Machine                        309

           153. Cowper’s Double Cylinder Machine                     309

           154. Tapes of Cowper’s Machine                            310

           155. Hopkinson and Cope’s Perfecting Machine              311

           156. Section of Casting Apparatus                         314

           157. Diagram of the Walter Press                          315

           158. Hoe’s Type Revolving Cylinder Machine                317

           159. Hoe’s “Railway” Machine                              319

           160. Napier’s Platen Machine                              320

           161. Roller for Printing Wall-Papers                      322

           162. Machine for Printing Paper-Hangings                  323

           163. Chain Testing Machine                                324

           164. Pascal’s Principle                                   325

           165. Collar of Hydraulic Cylinder                         326

           166. Hydraulic Press                                      327

           167. Section of Hydraulic Lift Graving Dock               331

           168. Section of Column                                    332

           169. Sir W. Armstrong’s Hydraulic Crane                   335

           170. Raising Tubes of Britannia Bridge                    336

           171. Press for Raising the Tubes                          337

           172. Head of Link-Bars                                    338

           173. Apparatus to Prove Transmission of Pressure          339

           174. Pneumatic Tubes and Carriages                        340

           175. Diagram of Tubes, &c.                                342

           176. Sending and Receiving Apparatus                      343

           177. Section of Receiving Apparatus                       344

           178. Sommeiller Boring Machines                           349

           179. Transit by Diligence over Mont Cenis                 353

           180. Burleigh Rock Drill on Tripod                        356

           181. The same on Movable Column                           358

           182. The same Mounted on Carriage                         359

           183. Diamond Drill Crown                                  360

           184. Diamond Drill Machinery                              363

           185. Chart of the Channel Tunnel                          367

           186. Section of the Channel Tunnel                        368

           187. View of Dover                                        369

        187_a_. Map of the St. Gothard Railway                       372

        187_b_. The Uppermost Bridge over the Maïenreuss             375

        187_c_. The Bridges over the Maïenreuss, near Wasen          377

        187_d_. Windings of the Line near Wasen                      378

           188. Contrasts of Light                                   380

           189. Rays                                                 382

           190. Diagram                                              383

           191. Telescopic Appearance of Jupiter and Satellites      384

           192. Diagram                                              386

 193, 194, 195. Diagrams                                             388

           196. Diagram                                              389

           197. Polemoscope                                          390

           198. Apparatus for Ghost Illusion                         391

        198_a_. The Ghost Illusion                                   393

           199. Illusion produced by Mirrors                         394

           200. A Stage Illusion                                     395

           201. View of Venice—Reflections                           396

           202. Refraction                                           397

           203. Diagram                                              398

      204, 205. Diagrams of Crystals                                 400

           206. Diagram                                              401

           207. Diagram                                              403

           208. Diagram                                              404

           209. Polariscope                                          406

           210. Section showing Polarisation                         407

           211. Iceland Spar, showing Double Refraction              407

           212. Diagram                                              408

           213. Diagram                                              410

           214. Diagram                                              412

           215. Portrait of Professor Kirchhoff                      416

           216. Diagram                                              417

           217. Newton’s Experiment                                  418

           218. Bunsen’s Burner on Stand                             421

           219. Spectroscope with one Prism                          423

           220. Miniature Spectroscope                               426

           221. The Gassiot Spectroscope                             427

           222. Browning’s Automatic Adjustment of Prisms            429

           223. Apparatus for Spark Spectra                          430

           224. The Sorby-Browning Micro-Spectroscope                433

           225. Section of Micro-Spectroscope, with Micrometer       434

           226. Diagram                                              435

           227. Section of Micro-Spectroscope                        436

           228. Solar Eclipse, 1869                                  439

           229. The Planet Saturn                                    441

           230. Solar Prominences, No. 1                             442

           231. Ditto, No. 2                                         443

           232. Section of Amateur Star Spectroscope                 444

        232_a_. X. Ray Photo of Living Hand, Exposure 4 minutes      446

        232_b_. Skiagraph of a Hand by Dr. Roentgen                  448

        232_c_. Metal objects photographed through Calico and sheet  450
                  of Aluminium

        232_d_. Skiagraph of Layers of various substances            451

           233. Portrait of Professor Helmholtz                      452

           234. Vertical Section of the Eye                          454

           235. Section of Retina                                    456

           236. Diagram                                              457

           237. Muscles of Eyes                                      459

           238. Diagram                                              461

           239. Diagram                                              464

           240. Diagram                                              465

           241. Ruete’s Ophthalmoscope                               466

           242. Diagram                                              467

           243. Wheatstone’s Reflecting Stereoscope                  469

           244. Diagram                                              470

           245. Diagram                                              471

           246. The Telestereoscope                                  473

           247. Lines                                                475

      248, 249. Diagrams                                             476

      250, 251. Diagrams                                             477

        251_a_. Edison’s Kinetographic Theatre                       479

           252. Portrait of Sir W. Thomson                           481

           253. A simple Electroscope                                485

           254. The Gold-leaf Electroscope                           489

           255. The Leyden Jar                                       490

           256. A Voltaic Element                                    491

           257. Ampère’s Rule                                        492

           258. Galvanometer                                         493

           259. Daniell’s Cell and Battery                           495

           260. Grove’s Cell and Battery                             495

           261. Wire Ignited by Electricity                          496

           262. Duboscq’s Electric Lantern and Regulator             497

           263. Decomposition of Water                               498

           264. Electro-plating                                      499

           265. A Current producing a Magnet                         500

           266. An Electro-magnet                                    501

           267. Ruhmkorff’s Coil                                     503

           268. Discharge through Rarefied Air                       504

        268_a_. Large Induction Coil at the Old Polytechnic          505
                  Institution, London

           269. Appearance of Spark on Looking-glass                 507

           270. Magneto-electric Spark                               508

           271. A Magnet producing a Current                         509

           272. Clarke’s Magneto-electric Machine                    509

           273. Magneto-electric Light                               510

           274. Diagram                                              511

           275. Gramme Machine                                       512

           276. Insulated Coils                                      513

           277. Hand Gramme Machine                                  513

           278. Gramme Machine, with eight Vertical Electro-Magnets  516

           279. Gramme Machine, with Horizontal Electro-magnets      517

           280. Gramme Machine                                       519

        280_a_. The Alliance Machine                                 520

        280_b_. Wilde’s Machine                                      521

        280_c_. Siemens’ Dynamo                                      522

        280_d_. The Brush Dynamo                                     523

        280_e_. Siemens’ Regulator                                   524

        280_f_. Jablochkoff Candle                                   525

        280_g_. Electric Lamp                                        526

        280_h_. Incandescent Lamp                                    529

        280_i_. Poles with Single Arms for Suburban Roads.—The       533
                  Ontario Beach Railway, Rochester, N.Y.

        280_j_. The Glynde Telepherage Line, on the system of the    534
                  late Fleeming Jenkin

        280_k_. Diagrams                                             540

        280_l_. The Tesla Oscillator                                 542

        280_m_. M. Nikola Tesla                                      543

           281. Portrait of Professor Morse                          547

           282. Double-Needle Instrument                             554

           283. Electro-magnetic Bells                               555

           284. Portable Single-Needle Instrument                    556

           285. Connections of Telegraph Line                        558

           286. Morse Recording Telegraph                            559

           287. Morse Transmitting Key                               561

           288. Morse Transmitting Plate                             562

           289. Step-by-step Movement                                567

           290. Froment’s Dials                                      567

           291. Wheatstone’s Universal Dial Telegraph                568

           292. Mirror Galvanometer                                  571

           293. Telegraph Post and Insulators                        573

           294. Ditto                                                573

           295. Wire Circuit                                         574

           296. Wire and Earth Circuit                               574

           297. Submarine Cable                                      575

           298. Making Wire for Atlantic Cable                       577

           299. Instrument Room at Valentia                          578

           300. Breaking of the Cable                                579

           301. Atlantic Telegraph Cable, 1866                       580

           302. Diagram                                              580

        302_a_. Reiss’s Musical Telephone                            584

        302_b_. Bell’s Musical Telephone                             585

        302_c_. Superposition of Currents                            587

        302_d_. Bell’s Speaking Telephone                            588

        302_e_. Hughes’s Microphone                                  591

                Lighthouse (heading)                                 593

           303. Eddystone Lighthouse                                 594

           304. Eddystone in a Storm                                 595

           305. Revolving Light Apparatus                            601

           306. Stephenson’s Holophotal Light                        604

           307. Camera                                               607

           308. Camera and Slide                                     615

           309. Folding Camera                                       616

           310. Lenses                                               617

           311. Bath                                                 619

        311_a_. The Roll-Slide                                       622

           312. Portrait of Aloysius Senefelder                      632

           313. Press for Stereotyping by Clay Process               633

        313_a_. The Linotype Machine                                 645

        313_b_. A Matrix                                             646

        313_c_. Diagram of Movements                                 647

        313_d_. A Line of Matrices                                   648

        313_e_. A finished Line entering galley                      649

        313_f_. The Melting Pot and Mould Wheel                      650

        313_g_. The Finished Line                                    651

        313_h_. Lines assembled into a “Form”                        651

        313_i_. Matrices dropping into Magazine                      652

           314. Recording Anemometer                                 653

           315. Registration of Height of Barometer and Thermometer  655

           316. Electric Chronograph                                 657

           317. Negretti’s Deep-Sea Thermometer                      661

           318. Ditto, General Arrangement                           662

           319. Atmospheric Recording Instrument                     663

        319_a_. Traces of Vibrations of a Tuning-Fork                667

        319_b_. Phonautographic Tracings of Different Vowel Sounds   667

        319_c_. Diagram                                              668

        319_d_. Phases of Sound Waves                                668

        319_e_. Edison’s Original Phonograph                         670

        319_f_. Diagrammatic Section of Phonograph                   671

        319_g_. The Graphophone                                      672

        319_h_. Edison’s Perfected Phonograph                        674

           320. Domestic Aquarium                                    675

           321. The Opelet                                           679

           322. Viviparous Blenny                                    680

           323. The Lancelet                                         681

           324. Sea-Horses                                           683

           325. Proteus anguinus                                     684

           326. Mud-Fish                                             685

           327. The Axolotl                                          686

           328. Sorting, Washing, and Digging at the South African   687
                  Diamond Fields

           329. Gold Miner’s Camp                                    689

           330. Gold in Rocks                                        690

           331. “Cradle” for Gold-washing                            690

           332. Pniel, from Jardine’s Hotel                          702

           333. Sifting at the “Dry Diggings”                        703

           334. Vaal River, from Spence Kopje                        704

        334_a_. Sketch Section of the Kimberley Diamond Mine         709

           335. Portrait of Sir Humphrey Davy                        714

           336. Apparatus                                            717

           337. Portrait of Mr. Thomas Hancock                       724

           338. Portrait of Sir James Young Simpson, M.D.            731

           339. Railway Cutting                                      740

           340. View on the Tyne                                     751

           341. Fossil Trees in a Railway Cutting                    752

           342. Impression of Leaf in Coal Measures                  753

           343. Possible Aspect of the Forests of the Coal Age       754

           344. The Fireside                                         756

           345. View on Hyde and Egbert’s Farm, Oil Creek            761

           346. View of City of London Gas-Works                     764

           347. Section of Gas-making Apparatus                      765

           348. The Retort                                           767

        348_a_. Retort House of the Imperial Gas-Works               768

           349. The Gas Governor                                     770

           350. Bunsen’s Burner                                      772

           351. Faraday’s Ventilating Gas-Burner                     773

        351_a_. Diagram                                              778

        351_b_. Diagram                                              778

        351_c_. Diagram                                              779

        351_d_. Diagram                                              779

        351_e_. Diagram                                              780

           352. Apparatus for making Magenta                         781

           353. Iron Pots for making Nitro-Benzol                    784

           354. Section of Apparatus for making Nitro-Benzol         785

           355. Apparatus for making Aniline                         786

           356. Section of Hollow Spindle                            787

           357. Portrait of J. Prescott Joule, F.R.S.                801



                            LIST OF PLATES.


                                PLATE I.
                                                                 TO FACE

 THE GREAT WHEEL IN ACTION                                  _Title page_

                                PLATE II.

 NORTH-EASTERN RAILWAY LOCOMOTIVE                                     18

                               PLATE III.

 THE GREAT STEAM HAMMER, ROYAL GUN FACTORY, WOOLWICH                  28

                                PLATE IV.

 THE AMERICAN TRACT SOCIETY BUILDING                                  76

                                PLATE V.

 GENERAL VIEW OF THE GREAT WHEEL AT EARL’S COURT                      84

                                PLATE VI.

 MOUNT WASHINGTON INCLINED TRACK                                     124

                               PLATE VII.

 PIKE’S PEAK RAILROAD, ROCKY MOUNTAINS                               128

                               PLATE VIII.

 THE “CLERMONT” FROM A CONTEMPORARY DRAWING                          130

                                PLATE IX.

 THE “MARY POWELL”                                                   144

                                PLATE X.

 THE “NEW YORK”                                                      148

                                PLATE XI.

 H.M.S. “THE TERRIBLE”                                               168

                               PLATE XII.

 THE 110–TON ARMSTRONG GUN                                           202

                               PLATE XIII.

 THE FORTH BRIDGE                                                    292

                               PLATE XIV.

 THE TOWER BRIDGE IN COURSE OF CONSTRUCTION                          298

                                PLATE XV.

 THE BROOKLYN BRIDGE                                                 304

                               PLATE XVI.

 THE NORTH MOUTH OF THE GREAT TUNNEL, ST. GOTHARD RAILWAY            374

                               PLATE XVII.

 SPECTRA (Coloured Plate)                                            422

[Illustration:

  _Wind, Steam, and Speed_ (after TURNER).
]



                             INTRODUCTION.


Only by knowledge of Nature’s laws can man subjugate her powers and
appropriate her materials for his own purposes. The whole history of
arts and inventions is a continued comment on this text; and since the
knowledge can be obtained only by observation of Nature, it follows that
Science, which is the exact and orderly summing-up of the results of
such observation, must powerfully contribute to the well-being and
progress of mankind.

Some of the services which have been rendered by science in promoting
human welfare are thus enumerated by an eloquent writer: “It has
lengthened life; it has mitigated pain; it has extinguished diseases; it
has increased the fertility of the soil; it has given new securities to
the mariner; it has furnished new arms to the warrior; it has spanned
great rivers and estuaries with bridges of form unknown to our fathers;
it has guided the thunderbolt innocuously from heaven to earth; it has
lighted up the night with the splendour of the day; it has extended the
range of the human vision; it has multiplied the power of the human
muscles; it has accelerated motion; it has annihilated distance; it has
facilitated intercourse, correspondence, all friendly offices, all
dispatch of business; it has enabled man to descend to the depths of the
sea, to soar into the air, to penetrate securely into the noxious
recesses of the earth, to traverse the land in cars which whirl along
without horses, to cross the ocean in ships which run ten knots an hour
against the wind. These are but a part of its fruits, and of its
first-fruits; for it is a philosophy which never rests, which has never
attained, which is never perfect. Its law is progress. A point which
yesterday was invisible is its goal to-day, and will be its
starting-point tomorrow.”—(MACAULAY).

Thus every new invention, every triumph of engineering skill, is the
embodiment of some scientific idea; and experience has proved that
discoveries in science, however remote from the interests of every-day
life they may at first appear, ultimately confer unforeseen and
incalculable benefits on mankind. There is also a reciprocal action
between science and its application to the useful purposes of life; for
while no advance is ever made in any branch of science which does not
sooner or later give rise to a corresponding improvement in practical
art, so on the other hand every advance made in practical art furnishes
the best illustration of scientific principles.

The enormous material advantages which this age possesses, the cheapness
of production that has placed comforts, elegancies, and refinements
unknown to our fathers within the reach of the humblest, are traceable
in a high degree to the arrangement called the “division of labour,” by
which it is found more advantageous for each man to devote himself to
one kind of work only; to the steam engine and its numerous
applications; to increased knowledge of the properties of metals, and of
the methods of extracting them from their ores; to the use of powerful
and accurate tools; and to the modern plan of manufacturing articles by
processes of copying, instead of fashioning everything anew by manual
labour. Little more than a century ago everything was slowly and
imperfectly made by the tedious toil of the workman’s hand; but now
marvellously perfect results of ingenious manufacture are in every-day
use, scattered far and wide, so that their very commonness almost
prevents us from viewing them with the attention and admiration they
deserve. Machinery, actuated by the forces of nature, now performs with
ease and certainty work that was formerly the drudgery of thousands.
Every natural agent has been pressed into man’s service: the winds, the
waters, fire, gravity, electricity, light itself.

But so much have these things become in the present day matters of
course, that it is difficult for one who has not witnessed the
revolution produced by such applications of science to realize their
full importance. Let the young reader who wishes to understand why the
present epoch is worthy of admiration as a stage in the progress of
mankind, address himself to some intelligent person old enough to
remember the century in its teens; let him inquire what wonderful
changes in the aspect of things have been comprised within the
experience of a single lifetime, and let him ask what has brought about
these changes. He will be told of the railway, and the steam-ship, and
the telegraph, and the great guns, and the mighty ships of war—

              “The armaments which thunderstrike the walls
              Of rock-built cities, bidding nations quake,
              And monarchs tremble in their capitals.”

He will be told of a machine more potent in shaping the destinies of our
race than warlike engines—the steam printing-press. He may hear of a
chemistry which effects endless and marvellous transformations; which
from dirt and dross extracts fragrant essences and dyes of resplendent
hue. He may hear something of a wonderful instrument which can make a
faint beam of light, reaching us after a journey of a thousand years,
unfold its tale and reveal the secrets of the stars. Of these and of
other inventions and discoveries which distinguish the present age it is
the purpose of this work to give some account.

[Illustration: JAMES WATT]



                             STEAM ENGINES.


To track the steps which led up to the invention of the Steam Engine,
and fully describe the improvements by which the genius of the
illustrious Watt perfected it at least in principle, are not subjects
falling within the province of this work, which deals only with the
discoveries and inventions of the present century. But as it does enter
into our province to describe some of the more recent developments of
Watt’s invention, it may be desirable to give the reader an idea of his
engine, of which all the more recent applications of steam are
modifications, with improvements of detail rather than of principle.

Watt took up the engine in the condition in which it was left by
Newcomen; and what that was may be seen in Fig. 2, which represents
Newcomen’s atmospheric engine—the first practically useful engine in
which a piston moving in a cylinder was employed. In the cut, the lower
part of the cylinder, _c_, is removed, or supposed to be broken off, in
order that the piston, _h_, and the openings of the pipes, _d_, _e_,
_f_, connected with the cylinder, may be exhibited. The steam was
admitted beneath the piston by the attendant turning the cock _k_, and
as the elastic force of the steam was only equal to the pressure of the
atmosphere, it was not employed to raise the piston, but merely filled
the cylinder, the ascent of the piston being caused by the weight
attached to the other side of the beam, which at the same time sent down
the pump-rod, _m_; and when this was at its lowest position, the piston
was nearly at the top of the cylinder, which was open. The attendant
then cut off the communication with the boiler by closing the cock, _k_,
at the same time opening another cock which allowed a jet of cold water
from the cistern, _g_, to flow through the opening, _d_, into the
cylinder. The steam which filled the cylinder was, by contact with the
cold fluid, instantly condensed into water; and as the liquefied steam
would take up little more than a two-thousandth part of the space it
occupied in the gaseous state, it followed that a vacuum was produced
within the cylinder; and the weight of the atmosphere acting on the top
of the piston, having no longer the elastic force of the steam to
counteract it, forced the piston down, and thus raised the pump-bucket
attached to the rod, _m_. The water which entered the cylinder from the
cistern, together with that produced by the condensation of the steam,
flowed out of the cylinder by the opening, _f_, the pipe from which was
conducted downwards, and terminated under water, the surface of which
was at least 34 ft. below the level of the cylinder; for the atmospheric
pressure would cause the cylinder to be filled with water had the height
been less. The improvements which Watt, reasoning from scientific
principles, was enabled to effect on the rude engine of Newcomen, are
well expressed by himself in the specification of his patent of 1769. It
will be observed that the machine was formerly called the “fire engine.”

[Illustration:

  FIG. 2.—_Newcomen’s Steam Engine._
]

[Illustration:

  FIG. 3.—_Watt’s Double-action Steam Engine._
]

“My method of lessening the consumption of steam, and consequently
fuel, in fire engines, consists of the following principles:—_First._
That vessel in which the powers of steam are to be employed to work
the engine (which is called the cylinder in common fire engines, and
which I call the steam-vessel), must, during the whole time the engine
is at work, be kept as hot as the steam that enters it; first, by
enclosing it in a case of wood, or any other materials that transmit
heat slowly; secondly, by surrounding it with steam or other heated
bodies; and thirdly, by suffering neither water nor any other
substance colder than the steam to enter or touch it during that
time.—_Secondly._ In engines that are to be worked either wholly or
partially by condensation of steam, the steam is to be condensed in
vessels distinct from the steam-vessels or cylinders, although
occasionally communicating with them,—these vessels I call condensers;
and whilst the engines are working, these condensers ought to be kept
at least as cold as the air in the neighbourhood of the engines by the
application of water or other cold bodies.—_Thirdly._ Whatever air or
other elastic vapour is not condensed by the cold of the condenser,
and may impede the working of the engine, is to be drawn out of the
steam-vessels or condensers by means of pumps, wrought by the engines
themselves or otherwise.—_Fourthly._ I intend in many cases to employ
the expansive force of steam to press on the pistons, or whatever may
be used instead of them, in the same manner in which the pressure of
the atmosphere is now employed in common fire engines. In cases where
cold water cannot be had in plenty, the engines may be wrought by this
force of steam only, by discharging the steam into the air after it
has done its office.—_Lastly._ Instead of using water to render the
pistons and other parts of the engines air- and steam-tight, I employ
oils, wax, resinous bodies, fat of animals, quicksilver, and other
metals in their fluid state.”

[Illustration:

  FIG. 4.—_Governor and Throttle-Valve._
]

From the engraving we give of Watt’s double-action steam engine, Fig. 3,
and the following description, the reader will realize the high degree
of perfection to which the steam engine was brought by Watt. The steam
is conveyed to the cylinder through a pipe, B, the supply being
regulated by the throttle-valve, acted on by rods connected with the
governor, D, which has a rotary motion. This apparatus is designed to
regulate the admission of steam in such a manner that the speed of the
engine shall be nearly uniform; and the mode in which this is
accomplished may be seen in Fig. 4, where D D is a vertical axis
carrying the pulley, _d_, which receives a rotary motion from the
driving-shaft of the engine, by a band not shown in the figures. Near
the top of the axis, at _e_, two bent rods work on a pin, crossing each
other in the same manner as the blades of a pair of scissors. The two
heavy balls are attached to the lower arms of these levers, which move
in slits through the curved guides intended to keep them always in the
same vertical plane as the axis, D D. The upper arms are jointed at _f
f_ to rods hinged at _h h_ to a ring not attached to the axis, but
allowing it to revolve freely within it. To this ring at F is fastened
one end of the lever connected with the throttle-valve in a manner
sufficiently obvious from the cut. The position represented is that
assumed by the apparatus when the engine is in motion, the disc-valve,
_z_, being partly open. If from any cause the velocity of the engine
increases, the balls diverge from increased centrifugal force, and the
effect is to draw down the ring at F, and, through the system of levers,
to turn the disc in the direction of the arrows, and diminish the supply
of steam. If, on the other hand, the speed of the engine is checked, the
balls fall towards the axis, and the valve is opened wider, admitting
steam more freely, and so restoring its former speed to the engine. On
one side of the cylinder are two hollow boxes, E E, Fig. 3,
communicating with the cylinder by an opening near the middle of the
box. Each of these steam-chests is divided into three compartments by
conical valves attached to rods connected with the lever, H. These
valves are so arranged that when the upper part of the cylinder is in
communication with the boiler, the lower part is open to the condenser,
I, and _vice versâ_. The top of the cylinder is covered, and the
piston-rod passes through an air and steam-tight hole in it; freedom of
motion, with the necessary close fitting, being attained by making the
piston-rod pass through a _stuffing-box_, where it is closely surrounded
with greased tow. The piston is also packed, so that, while it can slide
freely up and down in the cylinder, it divides the latter into two
steam-tight chambers. In an engine of this kind, the elastic force of
the steam acts alternately on the upper and lower surfaces of the
piston; and the condenser, by removing the steam which has performed its
office, leaves a nearly empty space before the piston, in which it
advances with little or no resistance. On the rod which works the
air-pump, two pins are placed, so as to move the lever, H, up and down
through a certain space, when one pin is near its highest and the other
near its lowest position, and thus the valves are opened and closed when
the piston reaches the termination of its stroke. In the condenser, I, a
stream of cold water is constantly playing, the flow being regulated by
the handle, _f_. The steam, in condensing, heats the cold water, adding
to its bulk, and at the same time the air, which is always contained in
water, is disengaged, owing to the heat and the reduced pressure. Hence
it is necessary to pump out both the air and the water by the pump, J,
which is worked by the beam of the engine. In his engines Watt adopted
the heavy fly-wheel, which tends to equalize the movement, and render
insensible the effects of those variations in the driving power and in
the resistance which always occur. In the action of the engine itself
there are two positions of the piston, namely, where it is changing its
direction, in which there is no force whatever communicated to the
piston-rod by the steam. These positions are known as the “dead points,”
and in a rotatory engine occur twice in each revolution. The resistance
also is liable to great variations. Suppose, for example, that the
engine is employed to move the shears by which thick plates of iron are
cut. When a plate has been cut, the resistance is removed, and the speed
of the engine increases; but this increase, instead of taking place by a
sudden start, takes place gradually, the power of the engine being in
the meantime absorbed in imparting increased velocity to the fly-wheel.
When another plate is put between the shears, the power which the
fly-wheel has gathered up is given out in the slight diminution of its
speed occasioned by the increased resistance. But for the fly-wheel,
such changes of velocity would take place with great suddenness, and the
shocks and strains thereby caused would soon injure the machine. This
expedient, in conjunction with that admirable contrivance, the
“governor,” renders it possible to set the same engine at one moment to
forge an anchor, and at the next to shape a needle. One of the most
ingenious of Watt’s improvements is what is termed the “parallel
motion,” consisting of a system of jointed rods connecting the head of
the piston-rod, R, with the end of the oscillating beam. As, during the
motion of the engine, the former moves in a straight line, while the
latter describes a circle, it would be impossible to connect them
directly. Watt accomplished this by hinging rods together in form of a
parallelogram, in such a manner that, while three of the angles describe
circles, the fourth moves in nearly a straight line. Watt was himself
surprised at the regularity of the action. “When I saw it work for the
first time, I felt truly all the pleasure of novelty, _as if I was
examining the invention of another man_.”

[Illustration:

  A B is half the beam, A being the main centre; B E, the main links,
    connecting the piston-rod, F, with the end of the beam; G D, the
    air-pump links, from the centre of which the air-pump-rod is
    suspended; C D moves about the fixed centre, C, while D E is movable
    about the centre D, itself moving in an arc, of which C is the
    centre. The dotted lines show the position of the links and bars
    when the beam is at its highest position.

  FIG. 4_a_.—_Watt’s Parallel Motion._
]

Many improvements in the details and fittings of almost every part of
the steam engine have been effected since Watt’s time. For example, the
opening and closing of the passages for the steam to enter and leave the
cylinder is commonly effected by means of the slide-valve (Fig. 5). The
steam first enters a box, in which are three holes placed one above the
other in the face of the box opposite to the pipe by which the steam
enters. The uppermost hole is in communication with the upper part of
the cylinder, and the lowest with the lower part. The middle opening
leads to the condenser, or to the pipe by which the steam escapes into
the air. A piece of metal, which may be compared to a box without a lid,
slides over the three holes with its open side towards them, and its
size is such that it can put the middle opening in communication with
either the uppermost or the lowest opening, at the same time giving free
passage for the steam into the cylinder by leaving the third opening
uncovered. In A, Fig. 5, the valve is admitting steam below the piston,
which is moving upwards, the steam which had before propelled it
downwards now having free exit. When the piston has arrived at the top
of the cylinder, the slide is pushed down by the rod connecting it with
the eccentric into the position represented at B, and then the opposite
movement takes place. The slide-valve is not moved, like the old pot-lid
valves, against the pressure of the steam, and has other advantages,
amongst which may be named the readiness with which a slight
modification renders it available for using the steam “_expansively_.”
This expansive working was one of Watt’s inventions, but has been more
largely applied in recent times. In this plan, when the piston has
performed a part of its stroke, the steam is shut off, and the piston is
then urged on by the expansive force of the steam enclosed in the
cylinder. Of course as the steam expands its pressure decreases; but as
the same quantity of steam performs a much larger amount of work when
used expansively, this plan of cutting off the steam is attended with
great economy. It is usually effected by the modification of the
slide-valve, shown at C, Fig. 5, where the faces of the slides are made
of much greater width than the openings. This excess of width is called
the “_lap_,” and by properly adjusting it, the opening into the cylinder
may be kept closed during the interval required, so that the steam is
not allowed to enter the cylinder after a certain length of the stroke
has been performed. The slide-valve is moved by an arrangement termed
the eccentric. A circular disc of metal is carried on the shaft of the
engine, and revolves with it. The axis of the shaft does not, however,
run through the centre of the disc, but towards one side. The disc is
surrounded by a ring, to which it is not attached, but is capable of
turning round within it. The ring forms part of a triangular frame to
which is attached one arm of a lever that communicates the motion to the
rod bearing the slide. Expansive working is often employed in
conjunction with _superheated steam_, that is, steam heated out of
contact with water, after it has been formed, so as to raise its
temperature beyond that merely necessary to maintain it in the state of
steam, and to confer upon it the properties of a perfect gas. Experience
has proved that an increased efficiency is thus obtained.

[Illustration:

  FIG. 5.—_Slide Valve._
]

The actual power of a steam engine is ascertained by an instrument
called the Indicator, which registers the amount of pressure exerted by
the steam on the face of the piston in every part of its motion. The
indicator consists simply of a very small cylinder, in which works a
piston, very accurately made, so as to move up and down with very little
friction. The piston is attached to a strong spiral spring, so that when
the steam is admitted into the cylinder of the indicator the spring is
compressed, and its elasticity resists the pressure of the steam, which
tends to force the piston up. When the pressure of steam below the
piston of the indicator is equal to that of the atmosphere, the spring
is neither compressed nor extended; but when the steam-pressure falls
below that of the atmosphere, as it does while the steam is being
condensed, then the atmospheric pressure forces down the piston of the
indicator until it is balanced by the tension of the now stretched
spring. The extension or compression of the spring thus measures the
difference between the pressure of the atmosphere and that of the steam
in the cylinder of the engine, with which the cylinder of the indicator
freely communicates.

From the piston-rod of the indicator a pencil projects horizontally, and
its point presses against a sheet of paper wound on a drum, which moves
about a vertical axis. This drum is made to move backwards and forwards
through a part of a revolution, so that its motion may exactly
correspond with that of the piston in the cylinder of the steam engine.
Thus, if the piston of the indicator were to remain stationary, a level
line would be traced on the paper by the movement of the drum; and if
the latter did not move, but the steam were admitted to the indicator,
the pencil would mark an upright straight line on the paper. The actual
result is that a figure bounded by curved lines is traced on the paper,
and the curve accurately represents the pressure of the steam at every
point of the piston’s motion. The position of the point of the pencil
which corresponds with each pound of pressure per square inch is found
by trial by the maker of the instrument, who attaches a scale to show
what pressures of steam are indicated.

If the pressure per square inch is known, it is plain that by
multiplying that pressure by the number of square inches in the area of
the piston of the engine, the total pressure on the piston can be found.
The pressure does not rise instantly when the steam is first admitted,
nor does it fall quite abruptly when the steam is cut off and
communication opened with the condenser. When the steam is worked
expansively, the pressure falls gradually from the time the steam is
shut off. Now, the amount of work done by any force is reckoned by the
pressure it exerts multiplied into the space through which that pressure
is exerted. Therefore the work done by the steam is known by multiplying
the pressure in pounds on the whole surface of the piston into the
length in feet of the piston’s motion through which that pressure is
exerted. The trace of the pencil on the paper—_i.e._, the _indicator
diagram_—shows the pressures, and also the length of the piston’s path
through which each pressure is exerted, and therefore it is not
difficult to calculate the actual work which is done by the steam at
every stroke of the engine. If this be multiplied by the number of
strokes per minute, and the product divided by 33,000, we obtain what is
termed the _indicated horse-power_ of the engine. The work done per
minute is divided by 33,000, because that number is taken to represent
the work that a horse can do in a minute: that is, the average work done
in one minute by a horse would be equal to the raising of the weight of
1,000 lbs. thirty-three feet high, or the raising of thirty-three pounds
1,000 feet high. The number, 33,000, as expressing the work that could
be done by a horse in one minute, was fixed on by Watt, but more recent
experiments have shown that he over-estimated the power of horses, and
that we should have to reduce this number by about one-third if we
desire to express the actual average working power of a horse. But the
power of engines having come to be expressed by stating the horse-power
on Watt’s standard, engineers have kept to the original number, which
is, however, to be considered as a merely artificial unit or term of
comparison between one engine and another; for the power of a horse to
perform work will vary with the mode in which its strength is exerted.
The source of the power which does the work in the steam engine is the
combustion of the coal in the furnace under the boiler. The amount of
work a steam engine will do depends not only on the quantity of steam
which is generated in a given time, but also upon the pressure, and
therefore the temperature at which the steam is formed.

[Illustration:

  FIG. 6.—_Section of Giffard’s Injector._
]

The water constantly evaporating in the boiler of a steam engine is
usually renewed by forcing water into the boiler against the pressure of
the steam by means of a small pump worked by the engine. In the
engraving of Watt’s engine this pump is shown at M. But recently the
feed-pump has been to a great extent superseded by a singular apparatus
invented by M. Giffard, and known as Giffard’s Injector. In this a jet
of steam from the boiler itself supplies the means of propelling a
stream of water directly into the boiler. Fig. 6 is a section of this
interesting apparatus through its centre, and it clearly shows the
manner in which the current of steam is made to operate on the jet of
water. The steam from the boiler passes through the pipe A and into the
tube B through the holes. The nozzle of this tube is of a conical shape,
and its centre is occupied by a rod pointed to fit into the conical
nozzle, and provided with a screw at the other end, so that the opening
can be regulated by turning the handle, C. At D the jet of steam comes
in contact with the water which feeds the boiler, the arrangement being
such that the steam is driven into the centre of the stream of water
which enters by the pipe E, and is propelled by the steam jet through
another cone, F, issuing with such force from the orifice of the latter
that it is carried forward through the small opening at G into the
chamber H. Here the water presses on the valve K, which it raises
against the pressure of the steam and enters the boiler. The water
issuing from the cone, F, actually traverses an open space which is
exposed to the air, and where the fluid may be seen rushing into the
boiler as a clear jet, except a few beads of steam which may be carried
forward in the centre, the rest of the steam having been condensed by
the cold water. The steam, of course, rushes from the cone, B D, with
enormous velocity, which is partly communicated to the water. The pipe,
L, is for the water which overflows in starting the apparatus, until the
pressure in H becomes great enough to open the valve. The supplies of
water and of steam have to be adjusted according to the conditions of
pressure in the boiler, and according to the temperature of the
feed-water. It is found that when the feed-water is at a temperature
above 120° Fahrenheit, the injector will not work: the condensation of
the steam is therefore necessary to the result. For, as the steam is
continually condensed by the cold water, it rushes from D with the same
velocity as into a vacuum, and the water is urged on by a momentum due
to this velocity. We must observe, moreover, that the net result of the
operation is a lessening of the pressure in the boiler; for the entrance
of the feed-water produces a fall of temperature in the boiler, and the
bulk of steam expended is fourteen times the bulk of the water injected:
thus, although the apparatus before actual trial would not appear likely
to produce the required result, the effect is no more paradoxical than
in the case of the feed-pump. The injector has been greatly improved by
Mr. Gresham, who has contrived to make some of the adjustments
self-acting, and his form of the apparatus is now largely used in this
country. The injector is applicable to stationary, locomotive, or marine
engines.

Steam boilers are now always provided with one of _Bourdon’s_ gauges,
for indicating the pressure of the steam. The construction of the
instrument will easily be understood by an examination of Fig. 7. The
gauge is screwed into some part of the boiler, where it can always be
seen by the person in charge. The stop-cock A communicates with the
curved metallic tube C, which is the essential part of the contrivance.
This tube is of the flattened form shown at D, having its greatest
breadth perpendicular to the plane in which the tube is curved, and it
is closed at the end E, where it is attached to the rod F, so that any
movement of E causes the axle carrying the index-finger, F, to turn, and
the index then moves along the graduated arc. The connection is
sometimes made by wheelwork, instead of by the simple plan shown in the
figure. The front plate is represented as partly broken away, in order
to show the internal arrangement, which, of course, is not visible in
the real instrument, where only the index-finger and graduated scale are
seen, protected by a glass plate.

[Illustration:

  FIG. 7.—_Bourdon’s Pressure Gauge._
]

When a curved tube of the shape here described is subjected to a greater
pressure on the inside than on the outside, it tends to become
straighter, and the end E moves outward; but when the pressure is
removed, the tube resumes its former shape. The graduations on the scale
are made by marking the position of the index when known pressures are
applied. The amounts of pressure, when the gauges are being graduated,
are known by the compression produced in air contained in another
apparatus. Gauges constructed on Bourdon’s principle are applied to
other purposes, and can be made strong enough to measure very great
pressures, such as several thousand pounds on the square inch; they may
also be made so delicate as to measure variations of pressure below that
of the atmosphere. The simplicity and small size of these gauges, and
the readiness with which they can be attached, render them most
convenient instruments wherever the pressure of a gas or liquid is
required to be known.

[Illustration:

  FIG. 8.—_Steam Generator._
]

A point to which great attention has been directed of late years is the
construction of a boiler which shall secure the greatest possible
economy in fuel. Of the total heat which the fuel placed in the furnace
is capable of supplying by its combustion, part may be wasted by an
incomplete burning of the fuel, producing cinders or smoke or unburnt
gases, another part is always lost by radiation and conduction, and a
third portion is carried off by the hot gases that escape from the
boiler-flues. Many contrivances have been adopted to diminish as much as
possible this waste of heat, and so obtain the greatest possible
proportion of available steam power from a given weight of fuel. Boilers
wholly or partially formed of tubes have recently been much in favour.
An arrangement for quickly generating and superheating steam is shown in
Fig. 8, in connection with a high-pressure engine.

Steam engines are constructed in a great variety of forms, adapted to
the purposes for which they are intended. Distinctions are made
according as the engine is fitted with a condenser or not. When steam of
a low pressure is employed, the engine always has a condenser, and as in
this way a larger quantity of work is obtainable for a given weight of
fuel, all marine engines—and all stationary engines, where there is an
abundant supply of water and the size is not objectionable—are provided
with condensers. High-pressure steam may be used with condensing
engines, but is generally employed in non-condensing engines only, as in
locomotives and agricultural engines, the steam being allowed to escape
into the air when it has driven the piston to the end of the stroke. In
such engines the beam is commonly dispensed with, the head of the
piston-rod moving between guides and driving the crank directly by means
of a connecting-rod. The axis of the cylinder may be either vertical,
horizontal, or inclined. A plan often adopted in marine engines, by
which space is saved, consists in jointing the piston-rod directly to
the crank, and suspending the cylinder on trunnions near the middle of
its length. The trunnions are hollow, and are connected by steam-tight
joints, one with the steam-pipe from the boiler, and the other with the
eduction-pipe. Such engines have fewer parts than any others; they are
lighter for the same strength, and are easily repaired. The trunnion
joints are easily packed, so that no leakage takes place, and yet there
is so little friction that a man can with one hand move a very large
cylinder, whereas in another form of marine engine, known as the
side-lever engine, constructed with oscillating beams, the friction is
often very great.


                           _THE LOCOMOTIVE._

The first locomotive came into practical use in 1804. Twenty years
before, Watt had patented—but had not constructed—a locomotive engine,
the application of steam to drive carriages having first been suggested
by Robinson in 1759. The first locomotives were very imperfect, and
could draw loads only by means of toothed driving-wheels, which engaged
teeth in rack-work rails. The teeth were very liable to break off, and
the rails to be torn up by the pull of the engine. In 1813, the
important discovery was made that such aids are unnecessary, for it was
found that the “bite” of a smooth wheel upon a smooth rail was
sufficient for all ordinary purposes of traction. But for this
discovery, the locomotive might never have emerged from the humble duty
of slowly dragging coal-laden waggons along the tramways of obscure
collieries. The progress of the locomotive in the path of improvement
was, however, slow, until about 1825, when George Stephenson applied the
blast-pipe, and a few years later adopted the tubular boiler. These are
the capital improvements which, at the famous trial of locomotives, on
the 6th of October, 1829, enabled Stephenson’s “Rocket” to win the prize
offered by the directors of the Liverpool and Manchester Railway. The
“Rocket” weighed 4½ tons, and at the trial drew a load of tenders and
carriages weighing 12¾ tons. Its average speed was 14 miles an hour, and
its greatest, 29 miles an hour. This engine, the parent of the powerful
locomotives of the present day, may now be seen in the Patent Museum at
South Kensington. Since 1829, numberless variations and improvements
have been made in the details of the locomotive. In weight, dimensions,
tractive power and speed, the later locomotives vastly surpass the
earlier types.

[Illustration:

  FIG. 9.—_Section of Locomotive_ (A.D. 1837).
]

Fig. 9 represents the section of a locomotive constructed _c._ 1837. The
boiler is cylindrical; and at one end is placed the fire-box, partly
enclosed in the cylindrical boiler, and surrounded on all sides by the
water, except where the furnace door is placed, and at the bottom, where
the fuel is heaped up on bars which permit the cinders to drop out. At
the other end of the boiler, a space beneath the chimney called the
smoke-box is connected with the fire-box by a great number of brass
pipes, open at both ends, firmly fixed in the end plates of the boiler.
These tubes are from 1¼ in. to 2 in. in diameter, and are very
numerous—usually about one hundred and eighty, but sometimes nearly
double that number. They therefore present a large heating surface to
the water, which stands at a level high enough to cover them all and the
top of the fire-box. The boiler of the locomotive is not exposed to the
air, which would, if allowed to come in contact with it, carry off a
large amount of heat. The outer surface is therefore protected from this
cooling effect by covering it with a substance which does not permit the
heat to readily pass through it. Nothing is found to answer better than
felt; and the boiler is accordingly covered with a thick layer of this
substance, over which is placed a layer of strips of wood ¾ in. thick,
and the whole is surrounded with thin sheet iron. It is this sheet iron
alone that is visible on the outside. The level of the water in the
boiler is indicated by a gauge, which is merely a very strong glass
tube; and the water carried in the tender is forced in as required, by a
pump (not shown in the Fig.). The steam leaves the boiler from the upper
part of the _steam-dome_, A, where it enters the pipe, B; the object
being to prevent water from passing over with the steam into the pipe.
The steam passes through the _regulator_, C, which can be closed or
opened to any extent required by the handle, D, and rushes along the
pipe, E, which is wholly within the boiler, but divides into two
branches when it reaches the smoke-box, in order to conduct the steam to
the cylinders. Of these there are two, one on each side, each having a
slide-valve, by means of which the steam is admitted before and behind
the pistons alternately, and escapes through the blast-pipe, F, up the
chimney, G, increasing the draught of the fire by drawing the flame
through the longitudinal tubes in proportion to the rush of steam; and
thus the rate of consumption of fuel adjusts itself to the work the
engine is performing, even when the loads and speeds are very different.
Though the plane of section passing through the centre of boiler would
not cut the cylinders, one of them is shown in section. H is the piston;
K the connecting-rod jointed to the crank, L, the latter being formed by
forging the axle with four rectangular angles, thus, __¦¯¯¦__; and the
crank bendings for the two cylinders are placed in planes at right
angles to each other, so that when one is at the “dead point,” the other
is in a position to receive the full power of the piston. There are two
safety valves, one at M, the other at N; the latter being shut up so
that it cannot be tampered with.

Locomotives are fitted with an ingenious apparatus for reversing the
engines, which was first adopted by the younger Stephenson, and is known
as the “link motion.” The same arrangement is employed in other engines
in which the direction of rotation has to be changed; and it serves
another important purpose, namely, to provide a means by which steam may
be employed expansively at pleasure. The link motion is represented in
Fig. 10, where A, B, are two eccentrics oppositely placed on the
driving-shaft, and their rods joined to the ends of the curved bar or
link, C D. A slit extends nearly the whole length of this bar, and in it
works the stud E, forming part of the lever, F, G, movable about the
fixed joint, G, and having its extremity, F, jointed to the rod H, that
moves the slide-valve. The weight of the link and the eccentric rods is
counterpoised with a weight, K, attached to the lever, I K, which turns
on the fixed centre, L. This lever forms one piece with another lever, L
M, with which it may be turned by pulling the handle of O P, connected
with it through the system of jointed rods. When the link is lowered, as
shown in the figure, the slide-valve rod will follow the movement of the
eccentric, B, while the backward and forward movement of the other
eccentric will only be communicated to the end of C, and will scarcely
affect the position of the stud E at all. By drawing the link up to its
highest position, the motion due to eccentric A only will be
communicated to the slide-valve rod, which will therefore be drawn back
at the part of the revolution where before it was pushed forward, and
_vice versâ_; hence the engine will be reversed. When the link is so
placed that the stud is exactly in the centre, the slide-valve will
receive no motion, and remain in its middle position, consequently the
engine is stopped. By keeping the link nearer or farther from its
central position, the throw of the slide-valve will be shorter or
longer, and the steam will be shut off from entering the cylinder when a
smaller or larger portion of the stroke has been performed.

[Illustration:

  FIG. 10.—_Stephenson’s Link Motion._
]

Although Fig. 9 represents with sufficient clearness all the essential
parts of a locomotive, it should be observed that as actually
constructed for use on the different lines of railway the machine is
greatly modified in the arrangement and proportions of its parts. A
greater number of adjuncts and subsidiary appliances are also provided
for the more effective and convenient working of the engine, and for
giving control over the movement of the train, and these, in fact,
conduce much to the greater economy and safety with which trains are now
run. As the circumstances and conditions under which railways are worked
vary much in different parts of the world, the locomotive has to be
designed to meet the requirements of each case, and its general
appearance, details and dimensions are accordingly much diversified.
From among the many types of recent locomotives we select for
illustration and a short description the form of express passenger
engine that has lately been designed by Mr. T. W. Worsdell, the engineer
of the North Eastern Railway, and this will give the opportunity of
noticing some of the newest improvements, which are embodied in this
engine. See Plate II.

The plan of causing the steam to work expansively has already been
mentioned on pages 8 and 9, as used by cutting off the steam when part
of the stroke of the piston has been made. Another mode by which the
expansive principle has long been made use of in stationary and marine
engines is to allow the steam from the boiler to enter first a smaller
cylinder and from that, at the end of the stroke, to pass into a larger
one in which, as it expands, it exercises a diminished pressure. This
arrangement has been called the compound or double-cylinder engine, and
was known to possess certain advantages where high pressure steam was
made use of. Indeed, in marine engines the principle of “triple
expansion” is now quite commonly adopted—that is, the steam passes
successively into three cylinders of successively greater diameter. Mr.
Webb, the locomotive engineer of the London and North Western Railway,
appears to have been the first to make the “compounding” system a
practical success as applied to the locomotive. In Mr. Webb’s
arrangement there are three cylinders, two smaller ones for the
high-pressure steam from the boiler, and between these a single large
low-pressure cylinder which receives the steam that has done its work
from both the smaller cylinders. In Mr. Worsdell’s engine the original
and simpler locomotive construction of two cylinders has been adhered
to, and thus the general plan of the engine is unchanged except in the
larger size of the low-pressure cylinder. In the present engine the
stroke is 24 in.; the high-pressure cylinder has its internal diameter
20 in. and the low-pressure cylinder a diameter of 28 in. The
boiler-shell is made of steel, the fire-box is of copper, and there are
203 brass tubes, 1¾ in. diameter and 10 ft. 11 in. long, connecting the
fire-box with the smoke-box. The frame, and indeed most parts of the
engine, are also made of steel. The driving-wheels, which here are a
single pair, have a diameter of 7 ft. 7¼ in. The total “wheel-base” is
nearly 21 ft., and it will be observed that the forepart of the engine
is supported on a four-wheeled _bogie_. The _bogie_ is capable of a
certain amount of horizontal motion by turning round a swivel, but this
movement is controlled by springs, so that, notwithstanding the length
of the frame, the engine is enabled to take curves with great facility,
while its motion is perfectly steady even at the highest speeds. The
working pressure of the steam in the boiler is 170 lbs. on the square
inch. The steam which leaves the high-pressure cylinder is conveyed to
the low-pressure cylinder by a pipe that is led round the inside of the
smoke-box, and thus enters the larger cylinder after taking up heat that
would otherwise be wasted, so that its elastic force is fully
maintained. This circumstance, no doubt, contributes to the very marked
economy of fuel that has been effected by the compound engines. How
great the economy is found in the working will be seen by the following
results, which are taken from the actual records. The same train was
taken over the same rails in ordinary quick passenger traffic for
several journeys which, as performed in the same time by the compound
engine and by another otherwise similar non-compound engine, required
for the compound, 25,254 lbs. of coal; for the non-compound, 32,104
lbs.; or, the consumption of coal by the former was 28 lbs. per mile; by
the latter, 36 lbs. per mile. This represents a saving of about 21 per
cent. of the fuel. As the steam enters the high-pressure cylinder first,
it would not be possible to start the engine if it had stopped at one of
the “dead-points” on that side, without a special arrangement for
admitting the steam directly to the other cylinder in such cases. This,
of course, is required only for the first stroke, and Mr. Worsdell and
M. von Borries have contrived for this purpose an ingenious valve,
brought into operation when required by a touch from the engineer, and
then immediately adjusting itself automatically, so as to restore the
steam connections to their normal condition.

[Illustration:

  PLATE II.

  NORTH EASTERN RAILWAY LOCOMOTIVE.
]

[Illustration:

  FIG. 10_a_.—_G.N.R. Express Passenger Locomotive._
]

Another type of the high-speed passenger engines used for express trains
on several of the great English railways is well represented by one of
the Great Northern Company’s locomotives, as depicted in Fig. 10_a_. In
this there are a single pair of driving wheels of very large diameter,
namely, 8 ft. 2 in., so that each complete movement of the pistons will
carry the engine forwards a length of nearly 26 ft. There are outside
cylinders, and therefore the driving axle is straight, and the leading
wheels are in two pairs, mounted on a _bogie_ which is capable of a
certain amount of independent horizontal rotation.

The Stephenson’s link motion, described on page 17, has lately been
often supplanted by another arrangement known as Joy’s valve gear, which
leaves the crank axle unencumbered with eccentrics, and, as taking up
less space, is generally now preferred for locomotives and also for
marine engines. Its principle is very simple, and will be readily
understood from the diagram in Fig. 10_b_, where _c_ is the spindle of
the slide-valves as in Fig. 5, but capable, we shall now suppose, of a
horizontal movement only. Jointed to it at D is a rod D E attached to a
block at E, which can move only within a slot in the strong bar E F in a
circular segment, the centre of which is at D. The bar we suppose for
the moment to be immovable, and disposed symmetrically to C D. Now let
an alternate up and down motion along the circular segment be given to
block E, and the effect will be to leave the centre, D, unchanged in
position, and, therefore, in that case the valve will not be moved at
all. Now this reciprocating movement is given to the block E by a system
of levers (not here shown), jointed to the connecting-rod (K, Fig. 9) in
such a manner that the rod D E is compelled to follow the movement of
the connecting-rod, but the end E must always travel in the circular
segment. We have hitherto supposed this segmental piece to be fixed, but
the engineer has the power of so turning it as to tilt either the upper
or lower part towards D. If, for instance, the guiding segment is fixed
as at II, the block in rising will push in the valve-spindle, and in
descending draw it out, as the length of the rod D E is invariable. But
if the guides be turned over so as to bring F nearer D than E, the same
movement of the block will give the reverse motions to the
valve-spindle.

[Illustration:

  FIG. 10_b_.—_Joy’s Valve Gear._
]

From the great rapidity with which the machinery of the locomotive
moves, the different parts require to be carefully balanced in order to
prevent dangerous oscillations. For example, the centrifugal force of
the massive cranks, etc., is balanced by inserting between the spokes of
the driving wheels certain counterpoises, the weights and positions of
which are finally adjusted by trial. The engine is suspended by chains
and set in motion, and a pencil attached to one corner of the frame
marks on a horizontal card the form of the oscillation, usually by an
oval figure. When the diameter of this figure is reduced to about 1/16
inch, the adjustment is considered complete.

The power of a locomotive, of course, depends on the pressure of the
steam and the size of the cylinder, &c.; but a very much lower limit
than is imposed by these conditions is set to the power of the engine to
draw loads by the adhesion between the driving wheels and the rails. By
the term “adhesion,” which is commonly used in this case, nothing more
is really meant than the friction between surfaces of iron. When the
resistance of the load drawn is greater than this friction, the wheels
turn round and slip on the rails without advancing. The adhesion depends
upon the pressure between the surfaces, and upon their condition. It is
greater in proportion as the weight supported by the driving-wheels is
greater, and when the rails are clean and dry it is equal to from 15 to
20 per cent. of that part of the weight of the engine which rests on the
driving-wheels; but when the rails are moist, or, as it is called,
“greasy,” the tractive power may be only 5 per cent. of the weight;
about one-tenth may be taken as an average. Suppose that 30 tons of the
weight of a locomotive are supported by the driving-wheels, that
locomotive could not be employed to drag a train of which the resistance
would cause a greater pull upon the coupling-links of the tender than
they would be subject to if they were used to suspend a weight of 3
tons. The number of pairs of wheels in a locomotive varies from two to
five; most commonly there are three pairs; and one, two, or all, are
driven by the engine, the wheels being coupled accordingly; very often
two pairs are coupled.

The pressure at which the steam is used in the locomotive is sometimes
very considerable. A pressure equal to 180 lbs. on each square inch of
the surface of the boiler is quite usual. The greater economy obtained
by the employment of high-pressure steam acting expansively in the
cylinder, points to the probability of much higher pressures being
adopted. There is practically no limit but the power of the materials to
resist enormous strains, and there is no reason, in the nature of
things, why steam of even 500 lbs. per square inch should not be
employed, if it were found otherwise desirable. It need hardly be said
that locomotives are invariably constructed of the very best materials,
and with workmanship of the most perfect kind. The boilers are always
tested, by hydraulic pressure, to several times the amount of the
highest pressure the steam is required to have, and great care is
bestowed upon the construction of the safety-valves, so that the steam
may blow off when the due amount of pressure is exceeded. The explosion
of a locomotive is, considering the number of engines in constant use, a
very rare occurrence, and is probably in all cases owing to the sudden
generation of a large quantity of steam, and not to an excessive
pressure produced gradually. Among the causes capable of producing
explosive generation of steam may be mentioned the deposition of a hard
crust of stony matter, derived from the water; this crust allows the
boiler to be over-heated, and if water should then find its way into
contact with the heated metal, a large quantity of steam will be
abruptly generated. Or should the water in the boiler become too low,
parts of the boiler may become so heated that on the admission of fresh
water it would be suddenly converted into steam. When an explosion does
take place, the enormous force of the agent we are dealing with when we
bottle up steam in an iron vessel, is shown by the effects produced.
Fig. 11 is from a photograph taken from an exploded locomotive, where we
may see how the thick plates of iron have been torn like paper, and the
tubes, rods, and levers of the engine twisted in inextricable confusion.

[Illustration:

  FIG. 11.—_Locomotive after Explosion._
]

[Illustration:

  FIG. 12.—_Hancock’s Steam Omnibus._
]

Locomotive engines for propelling carriages on common roads were
invented many years ago, by Gurney, Anderson, Scott Russell, Hancock,
and others. One designed by Hancock is represented in Fig. 12. Such
engines do not appear to have found much favour, though the idea has
been successfully realized in the traction engines lately introduced.
Probably the application of steam power to the propulsion of vehicles
along common roads fell into neglect on account of the superior
advantages of railways, but the common road locomotive is at present
receiving some attention. In the tramways which are now laid along the
main roads in most large cities we see one-half of the problem solved.
It is not so much mechanical difficulties that stand in the way of this
economical system of locomotion, as the prejudices and interests which
have always to be overcome before the world can profit by new
inventions. The engines can be made noiseless, emitting no visible steam
or smoke, and they are under more perfect control than horses. But
vestries and parochial authorities offer such objections as that horses
would be frightened in the streets, if the engine made a noise; and if
it did not, people would be liable to be run over, and the horses be as
much startled as in the other case. But horses would soon become
accustomed to the sight of a carriage moving without equine aid, however
startling the matter might appear to them at first; and the objection
urged against the noiseless engines might be alleged against wooden
pavements, india-rubber tires, and many other improvements. It is highly
probable that in the course of a few years the general adoption of
steam-propelled vehicles will displace horses, at least upon tramways.
The slowness with which inventions of undeniable utility and of proved
advantage come into general use may be illustrated by the fact of some
great English towns and centres of engineering industry not having made
a single tramway until, in all the populous cities of the United States,
and in almost every European capital, tramways had been in successful
operation for many years. [1890.]

Some time has elapsed since the foregoing paragraph was written for an
earlier edition of this work, and during that period there has been an
advance in both practice and opinion; so that now it has become highly
probable that before the century ends a great change may be witnessed in
our modes of locomotion, even on ordinary roads. Already every town of
importance throughout the United Kingdom has been provided with
excellent tramways, along which, in not a few instances, horseless
vehicles roll smoothly, to the great convenience of the general public,
while not one of the difficulties and dangers to general street traffic
has been experienced that were so confidently predicted by those who
were unable to perceive that an innovation might be an improvement. The
now universally-popular bicycle has been continually receiving
improvements, of which there appears to be no end, and as the machine
and all the contrivances connected with it are so familiar to everyone,
there is no need here to do more than to refer to them, because they
have led the way to great improvements in ordinary carriages.

The steam-propelled vehicle for common roads has just been mentioned as
an invention belonging to the first half of the century, and the reasons
it did not find favour have been alluded to. There exists in the United
Kingdom a law concerning horseless carriages travelling on highways,
which was passed to apply to traction engines, and enacts that other
than horse vehicles are not to go along a road at a greater speed than
four miles an hour, and only two miles an hour through a town, and
moreover they are to be preceded by a man bearing a red flag, etc. But a
bill has been introduced (1895) into the legislature to amend this law,
and permit the British people to use on their common roads such light
self-propelled carriages as are becoming popular in France, as may be
seen from the following account:—

On Tuesday, 11th June, 1895, a race was started from Versailles to
Bordeaux and back, a distance of 727 miles or more for the double
journey. The first prize was the substantial sum of 40,000 francs
(£1,600), to which was attached the condition of the carriage seating
four persons, and other prizes were also to be awarded to various kinds
of automatic vehicles. No fewer than sixty-six vehicles were entered for
competition, and these were variously supplied with motive power from
steam, electricity, or petroleum spirit. The starting place was
Versailles at 12·9 p.m., and at 10·32 on Wednesday morning MM. Panhard &
Levassor’s petroleum carriage arrived at Bordeaux, whence, after a stop
of only four minutes, the return journey was begun, but shortly
afterward an accident caused a delay of one hour, but the carriage made
the whole distance at the average of 14·9 miles per hour. In this and
three other carriages belonging to the same firm, the propeller was the
Daimler motor. Though this carriage was the first to accomplish the trip
it received only the second prize, the condition of seating _four_
persons not having been complied with. The first prize fell to a
four-seated vehicle by Les Fils de Peugeot Frères, a firm who carried
off besides the third and fourth prizes. These carriages were also
driven by so-called petroleum motors. These motors are really gas
engines on the principle to be presently mentioned, but the gas is
produced by the vapourisation of a volatile constituent of petroleum
(benzoline). The Daimler motor is a compact combination of two cylinders
connected with a chamber containing the explosive mixture of gas and
air. The pistons perform their in and out strokes simultaneously, but
their working strokes alternately.


                          _PORTABLE ENGINES._

The application of steam power to agricultural operations has led to the
construction of engines specially adapted by their simplicity and
portability for the end in view. The movable agricultural engines have,
like the locomotives, a fire-box nearly surrounded by the water, and
horizontal tubes, and are set on wheels, so that they may be drawn by
horses from place to place. There is usually one cylinder placed
horizontally on the top of the boiler; and the piston-rod, working in
guides, is, as in the old locomotive, attached by a connecting-rod to
the crank of a shaft, which carries a fly-wheel, eccentrics, and pulleys
for belts to communicate the motion to the machines. Engines of this
kind are also much used by contractors, for hoisting stones, mixing
mortar, &c. These engines are made with endless diversities of details,
though in most such simplicity of arrangement is secured, that a
labourer of ordinary intelligence may, after a little instruction, be
trusted with the charge of the engine; while their economy of fuel,
efficiency, and cheapness are not exceeded in any other class of steam
engine.

Besides the steam engines already described or alluded to, there are
many interesting forms of the direct application of steam power. There
are, for example, the steam roller and the steam fire-engine. The former
is a kind of heavy locomotive, moving on ponderous rollers, which
support the greater part of the weight of the engine. When this machine
is made to pass slowly over roads newly laid with broken stones, a few
repetitions of the process suffice to crush down the stones and
consolidate the materials, so as at once to form a smooth road. Steam
power is applied to the fire engine, not to propel it through the
streets, but to work the pumps which force up the water. The boilers of
these engines are so arranged that in a few minutes a pressure of steam
can be obtained sufficient to throw an effective jet of water. The cut
at the end of this chapter represents a very efficient engine of this
kind, which will throw a jet 200 feet high, delivering 1,100 gallons of
water per minute. It has two steam cylinders and two pumps, each making
a stroke of two feet. These are placed horizontally, the pumps and the
air reservoir occupying the front part of the engine, while the vertical
boiler is placed behind. The steam cylinders, which are partly hid in
the cut by the iron frame of the engine, are not attached to the boiler,
which by this arrangement is saved from injurious strains produced by
the action of the moving parts of the mechanism. There are seats for
eight firemen, underneath which is a space where the hose is carried. A
first-class steam fire-engine of this kind, completely fitted, costs
upwards of £1,300.

A cheap and very convenient prime mover has lately come into use, which
has certain advantages over even the steam engine. Where a moderate or a
very small power is required, especially where it is used only at
intervals, the _gas engine_ is found to be more convenient. It is small
and compact, no boiler or furnace is required, and it can be started at
any moment. As now made, it works smoothly and without noise. The piston
is impelled, not by the expansive force of steam, but by that of heated
air, the heat being generated by the explosion of a mixture of common
coal gas and air within the cylinder itself. Thus a series of small
explosions has the same effect as the admissions of steam through a
valve. A due quantity of gas and air is introduced into the cylinder,
and is ignited by the momentary opening of a communication with a
lighted gas jet outside. But the machine is provided with a regulator or
governor, which so acts on the valve mechanism that this communication
is made at each stroke only when the speed of rotation falls below a
certain assigned limit, and thus the number of the explosions is less
than the number of strokes, unless its work absorbs the machine’s whole
energy, which, according to the size of the engine, may be from that of
a child up to 30–horse power.


                          _THE STEAM HAMMER._

Before the invention of the steam hammer, large forge hammers had been
in use actuated by steam, but in an indirect manner, the hammer having
been lifted by cams and other expedients, which rendered the apparatus
cumbersome, costly, and very wasteful of power, on account of the
indirect way in which the original source of the force, namely, the
pressure of the steam, had to reach its point of application by giving
the blow to the hammer. Not only did the necessary mechanism for
communicating the force in this roundabout manner interfere with the
space necessary for the proper handling of the article to be forged, but
the range of the fall of the hammer being only about 18 in., caused a
very rapid decrease in the energy of the blow when only a very
moderate-sized piece of iron was introduced. For example, a piece of
iron 9 in. in diameter reduced the fall of the mass forming the hammer
to one-half, and the work it could accomplish was diminished in like
proportion. Besides, as the hammer was attached to a lever working on a
centre, the striking face of the hammer was parallel to the anvil only
at one particular point of its fall; and again, as the hammer was always
necessarily raised to the same height at each stroke, there was
absolutely no means of controlling the force of the blow. When we
reflect on the fact that the rectilinear motion of the piston in the
cylinder of the engine had first to be converted into a rotary one, by
beams, connecting-rod, crank, &c., and then this rotary movement
transformed into a lifting one by the intervention of wheels, shafts,
cams, &c., while all that is required in the hammer is a straight
up-and-down movement, the wonder is that such an indirect and cumbersome
application of power should have for so many years been contentedly
used. But in November, 1839, Mr. Nasmyth, an eminent engineer of
Manchester, received a letter from a correspondent, informing him of the
difficulty he had found in carrying out an order received for the
forging of a shaft for the paddle-wheels of a steamer, which shaft was
required to be 3 ft. in diameter. There was in all England no forge
hammer capable of executing such a piece of work. This caused Mr.
Nasmyth to reflect on the construction of forge hammers, and in _a few
minutes_ he had formed the conception of the steam hammer. He
immediately sketched the design, and soon afterward the steam hammer was
a _fait accompli_, for Mr. Nasmyth had one at once executed and erected
at his works, where he invited all concerned to come and witness its
performances. Will it be believed that four years elapsed before this
admirable application of steam power found employment outside the walls
of Mr. Nasmyth’s workshops? After a time he succeeded in making those
best able to profit by such an invention aware of the new power—for such
it has practically proved itself, having done more to revolutionize the
manufacture of iron than any other inventions that can be named, except,
perhaps, those of Cort and Bessemer. The usual prejudice attending the
introduction of any new machine, however obvious its advantages are
afterward admitted to be, at length cleared away, and the steam hammer
is from henceforth an absolute necessity in every engineering workshop,
and scarcely less so for some of the early stages of the process of
manufacturing crude wrought iron. Whether blows of enormous energy or
gentle taps are required, or strokes of every gradation and in any
order, the steam hammer is ready to supply them.

[Illustration:

  FIG. 13.—_Nasmyth’s Steam Hammer._
]

A steam hammer of the smaller kind is represented in Fig. 13. The
general mode of action will easily be understood. The steam is admitted
below the piston, which is thus raised to any required height within the
limits of the stroke. When the communication with the boiler is shut off
and the steam below the piston is allowed to escape, the piston, with
the mass of iron forming the hammer attached to the piston-rod, falls by
its own weight. This weight, in the large steam hammers, amounts to
several tons; and the force of the blow will depend jointly upon the
weight of the hammer, and upon the height from which it is allowed to
fall. The steam is admitted and allowed to escape by valves, moved by a
lever under the control of a workman. By allowing the hammer to be
raised to a greater or less height, and by regulating the escape of the
steam from beneath the piston, the operator has it in his power to vary
the force of the blow. Men who are accustomed to work the valves can do
this with great nicety. They sometimes exhibit their perfect control
over the machine by cracking a nut on the anvil of a huge hammer; or a
watch having been placed—face upwards—upon the anvil, and a moistened
wafer laid on the glass, a practised operator will bring down the
ponderous mass with such exactitude and delicacy that it will pick up
the wafer, and the watch-glass will not even be cracked. The steam
hammer has recently been improved in several ways, and its power has
been more than doubled, by causing the steam, during the descent, to
enter above the piston and add its pressure to the force of gravity.
Probably one of the most powerful steam hammers ever constructed is that
recently erected at the Royal Gun Factory at Woolwich, for the purpose
of forging great guns for the British Navy. It has been made by Nasmyth
& Co., and is in shape similar to their other steam hammers. Its height
is upwards of 50 ft., and it is surrounded with furnaces and powerful
cranes, carrying the huge iron tongs that are to grasp the glowing
masses. The hammer descends not merely with its own weight of 30 tons;
steam is injected behind the falling piston, which is thus driven down
with vastly enhanced rapidity and impulse. Of the lower portion of this
stupendous forge, nothing is visible but a flat table of iron—the
anvil—level with the floor of the foundry. But more wonderful, perhaps,
than anything seen aboveground, is the extraordinarily solid foundation
beneath. Huge tablets of foot-thick castings alternate with concrete and
enormous baulks of timber, and, lower down, beds of concrete, and piles
driven deep into the solid earth, form a support for the uppermost
plate, upon which the giant delivers his terrible stroke. Less than this
would render it unsafe to work the hammer to its full power. As the
monster works—soberly and obediently though he does it—the solid soil
trembles, and everything movable shivers, far and near, as, with a
scream of the steam, our ‘hammer of Thor’ came thundering down, mashing
the hot iron into shape as easily as if it were crimson dough, squirting
jets of scarlet and yellow yeast. The head of the hammer, which of
course works vertically, is detachable, so that if the monster breaks
his steel fist upon coil or anvil, another can be quickly supplied.
These huge heads alone are as big as a sugar-hogshead, and come down
upon the hot iron with an energy of more than a thousand foot-tons. By
the courteous permission of Major E. Maitland, Superintendent of the
Royal Gun Factories, we are enabled to present our readers with the view
of the monster hammer which forms the Plate III.

Mr. Condie, in his form of steam hammer, utilizes the mass of the
cylinder itself to serve as the hammer. The piston-rod is hollow, and
forms a pipe, through which the steam is admitted and discharged, and
the piston is stationary, the cylinder moving instead—between vertical
guides. A hammer face is attached to the bottom of the cylinder by a
kind of dovetail socket, so that if the striking surface becomes injured
in any way, another can easily be substituted. The massive framework
which supports the moving parts of Condie’s hammer has its supports
placed very far apart, so as to leave ample space for the handling of
large forgings.

[Illustration:

  FIG. 14.—_Merryweather’s Steam Fire-Engine._
]

[Illustration:

  PLATE III.

  THE GREAT STEAM HAMMER, ROYAL GUN FACTORY, WOOLWICH.
]

[Illustration:

  FIG. 15.—_A Foundry._
]



                                 IRON.


“Iron and coal,” it has been well said, “are kings of the earth”; and
this is true to such an extent that there is scarcely an invention
claiming the reader’s attention in this book but what involves the
indispensable use of these materials. Again, in their production on the
large scale it will be seen that there is a mutual dependence, and that
this is made possible only by means of the invention we have begun with;
for without the steam engine the deep coal mines could not have the
water pumped out of them,—it was indeed for this very purpose that the
steam engine was originally contrived,—nor could the coal be efficiently
raised without steam power. Before the steam engine came into use iron
could not be produced or worked to anything like the extent attained
even in the middle of the nineteenth century, for only by steam power
could the blast be made effective and the rolling mill do its work. On
the other hand, the steam engine required iron for its own construction,
and this at once caused a notable increase in the demand for the metal.
Once more, the engine itself supplies no force; for without the fuel
which raises steam from the water in the boiler it is motionless and
powerless, and that fuel is practically _coal_. In consequence of thus
providing power, and also of supplying a requisite for the production of
iron, coal has acquired supreme industrial importance, so that all our
great trades and places of densest population are situated in or near
coal-fields. But what we have further to say about coal may be
conveniently deferred to a subsequent article, while we proceed to treat
of iron, and of the contrivances in which it plays an essential part.

Iron has also been called “the mainspring of civilization,” and the
significance of the phrase is obvious enough when we consider the
enormous number and infinite variety of the things that are made of it:
the sword and the ploughshare; all our weapons of war and all our
implements of peace; the slender needle and the girders that span wide
rivers; the delicate hair-spring of the tiny watch and the most
tenacious of cables; the common utensils of domestic life and the huge
battle-ships of our fleets; the smoothest roads, the loftiest towers,
the most spacious pleasure palaces. Such extensive applications of iron
for purposes so diverse have been rendered possible only by the greater
facility and cheapness of production, together with the better knowledge
of the properties of the substance and increased skill in its treatment,
that have particularly distinguished our century. Apart again from the
constructive uses of iron, it enters essentially into another class of
inventions of which the age is justly proud, namely, those which utilize
electricity in the production of light, mechanical power, and chemical
action; for it is on a quality possessed by iron, and by _iron alone_,
that the generation of current by the electric dynamo ultimately
depends. This peculiar property of iron, which was first announced by
Arago in 1820, and has since proved so fertile in practical
applications, is that a bar of the metal can, under suitable conditions,
be instantly converted into the most powerful of magnets, and as quickly
demagnetized. What these conditions are will be explained when we come
to treat of electricity.

[Illustration:

  FIG. 16.—_Aerolite in the British Museum._
]

Besides the unique property of iron just referred to, and its
superlative utility in arts and industries, there are other
circumstances that give a peculiar interest to this metal. It is the
chief constituent of many minerals, and traces or small quantities are
found in most of the materials that make up the crust of the earth; it
is present also in the organic kingdoms, being especially notable in the
blood of vertebrate (_back-boned_) animals, of which it is an essential
component. Notwithstanding its wide diffusion, iron is not found
_native_, that is, as _metal_, but has to be extracted from its _ores_,
which are usually dull stony-looking substances, as unlike the metal as
can be conceived. In this respect it differs from gold, which is not met
in any other than the metallic state, in the form of _nuggets_, minute
crystals or branching filaments, and from metals such as silver, copper,
and a few others which also are occasionally found native. It is true
that rarely small quantities of metallic iron have been met with in the
form of minute grains disseminated in volcanic rocks; but in contrast
with the practical absence of metallic iron from terrestrial accessible
materials is the fact that masses of iron, sometimes of nearly pure
metal, occasionally descend upon the earth from interplanetary space.
These are _aerolites_, of which there are several varieties, some
consisting only of crystalline minerals without any metallic iron,
others of a mixture of minerals and metals, but the most common are of
iron, always alloyed with a small quantity of nickel, and usually
containing also traces more or less of a few other metals and known
chemical elements. The iron in some specimens has been found to amount
to 93 per cent. of the whole. These _aerolites_, or _meteorites_, as
they are also called, are of irregular shape and vary greatly in size,
which however is sometimes very considerable: one found in South America
was calculated to weigh 14 tons, another discovered in Mexico, 20 tons.
There is in the British Museum a good specimen of an iron meteorite,
which is represented in Fig. 16, where it will be observed that a
portion has been cut off to form a plane surface, which when polished
and etched by an acid, reveals a crystalline structure quite peculiar
and distinctive, so that such meteorites can be recognized with
certainty, even if they did not possess surface characters which are
easily observed and identified when once a specimen has been examined.
The fall of meteorites to the surface of the earth is comparatively
rare, but it has been witnessed by even scientific observers; as when
Gassendi, the French astronomer, saw in Provence the fall of a meteorite
weighing 59 lbs. In the _Transactions of the Royal Society_ for 1802 may
be found a detailed account of an instance in England of the fall which
took place in Yorkshire, on the 13th December 1795, of a stone 56 lbs.
in weight. Aerolites become ignited or incandescent by reason of the
great velocity with which they pass through the atmosphere, whereby the
air in front of them is condensed and heated, the heat often being
sufficient to liquefy or even vaporize the solid matter. The so-called
shooting stars are with good reason believed to be nothing but such
incandescent aerolites, and the aerolites themselves are regarded as
small asteroids, or scattered planetary dust, portions of which
occasionally coming within the sphere of the earth’s attraction are
drawn to its surface. Meteoric iron is too rare to be of any value as a
source of iron, but certain specimens have been found in which the metal
was malleable and of excellent quality. From such meteorites the natives
of India and other places have, it is said, sometimes forged weapons of
wonderful temper and keenness, and we may well imagine that when such
weapons have been made from iron that had actually been observed to fall
from the sky, they would be regarded as endowed with magical powers, so
that we may perhaps ascribe to such circumstances the origin of some of
the legends about enchanted swords, etc. It is significant also that in
some Egyptian inscriptions of the very highest antiquity, the word
indicating iron has for its literal meaning _stone of the sky_.

But as nature has hardly provided man with the _metal_ iron, he has been
obliged to find the art of extracting it from substances which are
utterly unlike the metal itself. In this case, as in many others, the
art has been discovered and practised ages before any scientific
knowledge of the nature of the processes employed had been acquired. The
idea prevails that there are such difficulties in extracting this metal;
that elaborate and complex appliances, not unlike those in use in modern
times, were requisite for the purpose; and therefore that the use of
iron is compatible only with a somewhat late period in man’s history,
and implies a comparatively advanced stage of civilization. Now there
undoubtedly are facts which tend to confirm this view; for instance, the
Spaniards who first colonized North America found the natives perfectly
familiar with the use of copper, but without any acquaintance with iron,
although the region abounded with the finest ferruginous minerals; and,
again, the archæologists who have examined the relics of ancient
civilizations and of pre-historic peoples about the shores of the
Mediterranean, find in the earliest of these relics weapons and
implements of rudely chipped stones, followed later by the use of
better-shaped and polished stones; hence the periods represented by
these, they have respectively designated by the terms _palæolithic_ and
_neolithic_—the old and the new stone ages. At some later time the stone
of these implements was gradually replaced by _bronze_, which is a
mixture of copper and tin, while as yet iron does not occur in any form
among the remains. In the latest layers, however, articles of iron are
found, and it is inferred that this metal came into use only after
bronze had been known for an indefinite period; hence these later
pre-historic periods have come to be respectively called _the bronze
age_ and _the iron age_. No doubt this succession really occurred in the
localities where the observations were made, but it would not be
justifiable to assume that the same was the case in every part of the
world, for much would depend on such circumstances as the presence or
absence of the essential minerals. We may also set against the supposed
difficulty of obtaining iron from the ores, the still greater complexity
of the methods required for the production of copper and of tin. Besides
this is the fact that the ores of tin are found but in very few places
in the world, and of these only the Cornwall mines, so well known in
ancient times, would be likely to furnish a supply to the places where
pre-historic bronzes are found; this implies that navigation and
commerce must have already made considerable progress. On the other
hand, iron has been produced and worked for untold ages by the negro
races all over Central Africa, and the method of treating the ore has no
doubt been that which is there still practised by certain scarcely
civilized tribes, and it is as simple as any metallurgical operation can
possibly be, requiring merely a hole dug in a clay bank, wherein the
fuel and minerals are piled up, and the mere wind supplies sufficient
blast to urge the fire to the needful temperature, or air is blown in
from rude bellows made of a pair of skins alternately raised and
compressed. These very primitive furnaces have in some places developed
into permanent clay structures, seven or eight feet in height. The
natives of Central Africa have therefore long known the method of
extracting iron, as well as of forging and casting it.

The nature and value of what has been done during the century in the
treatment of iron would not be intelligible without some description of
the ordinary processes of extracting the metal from the ores; and a
scientific understanding of these implies some acquaintance with
chemistry. Not because metallurgy has been developed from chemistry, for
the fact is rather the reverse; indeed, as we have seen, the art of
extracting iron from its ores was practised ages before chemistry as a
science was dreamt of. Although we may assume that many of our readers
have sufficient knowledge of chemistry to attach distinct ideas to such
few chemical terms as we shall have occasion to use, yet it may be of
advantage to others to have some preliminary notes of the character of
the chemical actions, and of some properties of the substances that will
have to be referred to. It is certainly the case that people in general,
and even people very well informed in other subjects, have but the
vaguest notions of the nature of chemical actions, and of the meaning of
the terms belonging to that science. For example, one of our most
popular and justly esteemed writers, treating of the very subject of
iron extraction, calls the ore a _matrix_, thereby implying that the
iron as metal is disseminated in detached fragments throughout the mass,
which is a conception inconsistent with the facts. The reader will be in
a more advantageous position for understanding the relation of the ores
of iron to the metal, if he will follow in imagination, or still better
in reality, a few observations and experiments like the following—of
which, however, he is recommended not to attempt the chemical part
unless he is himself practically familiar with the performance of
chemical operations, or can obtain the personal assistance of someone
who is. Taking, say, a few common iron nails, let him note some obvious
properties they possess: they have weight—are hard and tough so that
they cannot be crushed in a mortar—are opaque to light—if a smooth
surface be produced on any part, it will show that peculiar shiny
appearance which is called metallic lustre, in this case without any
decided colour—they are not dissolved by water as sugar or salt is—and
are attracted by a magnet. If several of the nails be heated to bright
redness they may be hammered on an anvil into one mass, and this may be
flattened out into a thin plate, or it may be shaped into a slender rod
and then drawn out into wire; or otherwise the nails may be converted
into the small fragments called iron filings. In these several forms the
nails, as nails, will have ceased to exist; but the material of which
they were formed will remain unchanged, and each and every part of it
however large or small will continue to exhibit all the properties noted
above as belonging to the substance of the nails, which in the cases
supposed has undergone merely _physical_ change of shape. Treating our
nails in yet another way, we may proceed to subject them to a _chemical_
change, by an experiment very simple in itself, but involving certain
precautions, by neglect of which the tyro in chemical operations would
incur some personal risks; these might however be obviated by using only
very small quantities of the materials (a mere pinch of iron filings and
a few drops of sulphuric acid), when the results would still be
sufficiently observable. A few of the iron nails having been placed in a
flask of thin glass, we pour upon them a mixture of oil of vitriol
(sulphuric acid) and water, which has previously been prepared by
gradually adding 1 measure of the acid to 5 measures of water. The
action that takes place is greatly accelerated by heat, and indeed the
contents should be heated to boiling by standing the flask on a layer of
fine sand spread on an iron plate and gently heated from below. The
nails will soon disappear, being completely dissolved by the acid
liquid, and the turbid solution should be filtered through filtering
paper as rapidly as possible and while still hot. This turbid and dirty
looking condition is due to foreign matters in the nails, for these
never consist of _pure_ iron. The filtered liquid is set aside to cool
in a closed vessel, in which after a time will be found a deposit of
crystals of a pale bluish-green colour. The liquor above these having
been poured off, the crystals are to be rinsed with a very small
quantity of _cold_ water, and then dried between folds of
blotting-paper, after which they are ready for examination. The quantity
of the diluted acid put into the flask should have a certain proportion
to the weight of the nails; about 5 _fluid ounces_ to 1 ounce of iron
will be found convenient, for if less is used the nails will not be
entirely dissolved, and an excess will tend to keep the crystals in
solution instead of depositing them when cold. The nails—as such—will
now have passed out of existence: can we say that the iron that formed
them exists in the crystals? Certainly not as the _metal_ iron, for
every property of the metal will have disappeared. The crystals are
brittle, can be crushed in a mortar—they are translucent—they show no
metallic lustre, but only glassy surfaces—they are readily dissolved by
water—they are not attracted by a magnet. The most powerful lens will
fail to show the least particle of iron in them; they have in their
properties no assignable relation to the metal of the nails, but are
matter of quite another sort; and be it noted that this entire
_otherness_ is the special and characteristic sign of _chemical change_.
So complete is the transformation in the case we have been considering
that it would never have been said that iron was contained in these
crystals, but rather that the metal had for ever passed out of
existence, but for one circumstance; and that is, that by subjecting the
crystals to certain processes of _chemical analysis_ we can again obtain
from them the iron in metallic state. Nay more, we should find the
weight of metal so obtained to be exactly equal to that of the pure iron
dissolved from the original nails, supposing of course that we operated
upon the whole of the crystalline matter so produced. The inference
therefore is that although every property of the iron appeared to be
absent from the crystals, the iron entering in them retained there its
original weight, and the correct statement of the change would be, that
in the crystals the iron had lost all its original properties SAVE ONE,
namely, its weight, or gravitating force, if we choose to call it so, a
property belonging to it in common with every material substance.
Chemical analysis can also separate from the crystals their other
constituents and weigh them apart—so much water and so much sulphuric
acid—and when to these weights that of the iron is added, the sum
exactly makes up the weight of the crystals.

A still simpler experiment, which may be performed by anyone with the
greatest ease, may serve as a further illustration of the profound
nature of the change in the properties of bodies brought about by
chemical combination, and it will also serve as the occasion of
directing attention to a remarkable circumstance that invariably
characterizes such changes, and one that should always be present in our
minds when we are considering them. A yard of flat _magnesium_ wire can
be bought for a few pence, and after its metallic character has been
observed in the silvery lustre disclosed by scraping the dull white
surface, a few inches is to be held vertically by a pair of tongs, or by
inserting one extremity in a cleft at the end of a stick, then the lower
part is brought into contact with a candle or gas flame. The metal will
instantly burn with a dazzlingly brilliant light, and some white smoke
(really fine white solid particles) will float into the air; but if a
plate be held under the burning metal, some of the smoke will settle
upon it, together with white fragments that have preserved some shape of
the metallic ribbon, but which a touch will reduce into a fine white
powder, identical with the well-known domestic medicine called “calcined
magnesia”—a substance totally different from the _metal magnesium_. The
reader will scarcely require to be told that in this burning the metal
is entering into combination with the oxygen of the air—by which that
invisible gas somehow becomes fixed in these solid white particles, so
entirely unlike itself. But this experiment might be so arranged that
the quantities of magnesium and oxygen entering into the magnesia could
be weighed. For this purpose special appliances would be required in
order to ensure complete combustion of the metal, for in the experiment
as just described some small particles are liable to be shielded from
the oxygen by a covering of magnesia, and the arrangement would have to
be such that the _whole_ of the white powder could be gathered up and
weighed. In the absence of such appliances, and of a delicate balance,
together with the skill requisite for their use, the reader must for the
time be contented to take our word for what would be the result. In
every experiment the magnesia would be found heavier than the metal
burned in the proportion of 5 to 3; in other words, magnesia always
contains (so the phrase runs) 3 parts of magnesium combined with 2 of
oxygen: never more nor less. A definite proportion between the weights
of the constituent substances characterizes every chemical combination,
and when this is once determined in a single sample of the compound, it
is determined for every portion of the same, wherever found or however
produced. But each compound has its own particular proportion, that is,
the quantitative relations are different for each. For example, the two
constituents of water, hydrogen and oxygen, are combined in the ratio of
1 to 8, etc.; and oxygen combines with metals in a ratio different in
each case. Then occasionally the same ratio of constituents occurs in
compounds of different composition. The elementary student is apt to
suppose that this is _because_ of the _law_ which he finds stated,
probably in almost the first page of his text-book: “Every compound
contains its elements in definite and invariable proportions”; and even
well-educated people entertain the idea of the fact being “governed by”
or “obeying” the law just quoted,—a misconception arising from the other
use of the word “law,” as signifying an enactment. The real case however
is the converse; namely, that a multitude of facts like that above
stated have governed the law, and caused it to be what it is—the general
statement of many observed facts.

We have assumed that the reader’s chemical knowledge had already made
him aware that in every case of ordinary combustion the oxygen of the
atmosphere is in the act of entering into combination with the burning
body: as with the magnesium, so with a coal fire, a gas flame, or a
burning candle; only in these last cases the products of the combustion
pass away invisibly. The candle by burning disappears from sight, but
its matter is not lost, and as in the case of magnesium, the compounds
it forms weigh more than the unburnt candle. The experiment is commonly
shown in courses of elementary lectures on chemistry, of so burning a
candle that the invisible products are retained in the apparatus,
instead of being dissipated in the atmosphere, and the increase of
weight of the burnt candle over the original one is demonstrated by the
balance. Important as is the part played by oxygen in all chemical
actions on the earth, the composition of the atmosphere was not
understood until the end of the eighteenth century, and it was well on
into the nineteenth before the quantities of its constituents were
accurately determined. Now everyone knows that air is mainly made up of
a _mixture_ of the two gases _oxygen_ and _nitrogen_. A _mixture_ of two
or more things is very different from a chemical _combination_ of them;
for in the former each ingredient retains its own properties. (See _Air_
in Index.) Nitrogen being an inert gas that takes no part in combustion,
or in the ordinary chemical actions of the air, acts therein simply as a
diluent of the oxygen. It is necessary in relation to our present
subject to bear this in mind, as well as the relative quantities of the
two gases in air. For our immediate purpose we may neglect the minor
constituents of air—such as watery vapour, carbonic acid, etc., of which
the total weight does not exceed one hundredth part of the whole—and
consider air as a mixture of 23 parts by weight of oxygen with 77 of
nitrogen, or calculated in volumes, 21 measures of oxygen with 79 of
nitrogen. Compounds of oxygen with nearly every one of the other seventy
or more chemical elements are known, and these compounds, which are
called _oxides_, are arranged by chemists under five or six classes,
forming as they do _basic radicles_, _acid radicles_, _saline oxides_,
etc. With some of these compounds belonging to different classes, we
must make acquaintance after noticing the elementary substance with
which the oxygen is united.

We begin with _carbon_, which forms the chief constituent of all our
combustibles. Some specimens of graphite, plumbago, or “blacklead”
consist of almost pure carbon (98 per cent.), and some varieties of wood
charcoal exceptionally contain 96 per cent.; but in ordinary charcoal
the percentage is much less. Coal, the most familiar of our solid fuels,
varies greatly in composition, carbon being the predominating
constituent, in amount from 57 to 93 per cent. Coke, another fuel much
used in metallurgical operations, is made by heating coal without access
of air, when a large quantity of gaseous substances is expelled. Coke
burns with an intense and steady heat without emitting any visible
smoke, but it does not ignite as readily as coal. Carbon forms two
different compounds with oxygen: both are invisible gases, but they
differ in the proportions of the constituents, and present different
properties. When carbon (coal, coke, or charcoal) is completely burnt,
that is, with an abundant supply of air, the product is _carbonic acid_
gas, in which 3 parts of carbon are combined with 8 of oxygen: when, on
the other hand, the carbon is burnt with a sufficiently restricted
access of air, the result is _carbonic oxide_ gas, in which 3 parts of
carbon are united with only 4 of oxygen. The reader will here observe
that the former contains just twice as much oxygen as the latter for the
same quantity of carbon. This fact and numberless others like it are
expressed or summed up by another _law_ of chemical combination which
states that when two elements combine in several different proportions
these are invariably such that the ratios in the several compounds will
be found to have exact and simple numerical relations; that is, such as
may, when reduced to their lowest terms, be expressed by the simple
integers 1, 2, 3, etc., as 1 : 2, 3 : 2; ... 8 : 9, etc. It comes to the
same thing if we compare together the weights A and A´ which are united
in each compound with any one identical weight of B, giving of course
the ratio A : B ÷ A´ : B. For instance, in the case just given, of
carbon and oxygen, 3 : 4 ÷ 3 : 8 = 2 : 1. This, which is simply stating
the facts, is called the _law of multiple proportions_. On a later page
will be found another illustration (see Index, _Nitrogen and Oxygen
Compounds_), and its expression in terms of the _atomic theory_, which
goes behind the facts (so to speak), but is extremely useful by
comprehending many other groups of facts in chemistry and in other
sciences. Carbonic acid gas is of course incombustible, but carbonic
oxide gas burns by uniting with the additional proportion of oxygen and
becoming carbonic acid. On the other hand, carbonic acid gas passing
over red-hot coals takes up from them the additional proportion of
carbon, and is, we may say, _unburnt_ into carbonic oxide. When we see a
pale blue flame flickering over the bright embers in a fire grate, it is
carbonic oxide burning back again by taking more oxygen from the air
above the coals. Carbonic oxide combines directly with two or three of
the metals, as, for instance, it forms a volatile compound with nickel,
at a certain temperature, and this is decomposed again at a higher
temperature. The like takes place with iron, although in very small
quantities, but the observation throws some light on the processes of
reduction. Carbonic oxide is neither acid nor basic, but carbonic acid
is an acid oxide, and as such unites with oxides of the basic class to
form another range of compounds. Thus, for example, the oxide of the
metal _calcium_ is quicklime, which is strongly basic, and this directly
combines with carbonic acid, forming a _neutral_ substance called in
systematic chemistry _calcium carbonate_, or more commonly but less
correctly, carbonate of lime, familiar to everyone in the compact state
as limestone, and marble, and in a more or less pulverent condition as
chalk. When any of these is heated to redness, carbonic acid is expelled
and quicklime remains. Like most oxides, quicklime forms a compound with
water, the combination being attended with the extrication of much heat,
the compact quicklime swelling and crumbling into _slaked lime_. The
chemist’s term for a compound of a _basic_ oxide with water is
_hydrate_, while that of an _acid_ oxide with water is for him properly
an _acid_, or in order to particularly distinguish this class, an
_oxy-acid_. It was however the older practice to give the name of acid
to the oxide alone, and this naming having found its way into popular
language is much more familiar to the non-scientific reader. The
systematic names of the two compounds of carbon and oxygen are _carbon
monoxide_ and _carbon dioxide_, but we shall use here the more familiar
terms carbonic oxide and carbonic acid.

We have now to call attention to a substance which contributes by far
the largest part to the solid crust of our globe. It is called _silica_,
from _silic-_, the Latin word for flint (without case suffix): it is
seen in flint, and very pure in rock crystal, quartz, agate, and
calcedony. It forms the essential part of every kind of sand and
sandstone, and is the principal ingredient of clay, granite, slate,
basalt, and many other minerals. Silica is the oxide of a quasi-metal
called _silicon_, which can be obtained from silica with difficulty, and
only by roundabout processes, presenting itself in different conditions
according to the process used. Silica is an acid oxide, and it readily
unites with most of the basic oxides when heated with them, forming a
class of compounds of different properties which are much modified in
admixtures containing two or more. Very few of these _silicates_ are
soluble in water, most of them are not: they are all fusible at various
temperatures, except silicate of alumina, of which fire-clay is chiefly
constituted. Alumina, it should be stated, is the oxide of the metal
aluminium. The silicates of lime and of magnesia fuse only with great
difficulty; but the silicates of iron and of manganese are easily fused,
and silicate of lead still more so. Glass is a mixture of silicates,
often of lime, soda, and alumina; sometimes of lead and potash mainly;
porcelain and pottery consist chiefly of silicate of alumina with
varying proportions of silicates of iron, of lime, etc.

It now remains only to mention two non-metallic elements that are nearly
always present in crude iron, but which the metallurgist strives to
eliminate, as they are in general very injurious to the quality of the
material even when their amount is very small. The first is _sulphur_,
well known as _brimstone_, also as _flowers of sulphur_, a yellow
coloured solid, which burns in the air. The product of the combustion is
an invisible gas of a readily recognized pungent odour: this is an
acid-forming oxide containing equal weights of sulphur and oxygen. There
is another oxide in which the weight of oxygen is one and a half times
that of the sulphur, and this is the radicle of the very active
_sulphuric acid_ or _oil of vitriol_. Sulphur, like oxygen, unites with
most of the other elements, forming compounds called _sulphides_. Of
these the iron compound called _pyrites_ is the best known, and its
occurrence in coal prevents the use of that material as fuel in contact
with iron or other metals. _Phosphorus_ is an element that occurs
naturally only in combination; in its separated state it is a very
inflammable solid. It combines directly with other substances and is
taken up by some fused metals in large quantities. In many cases a very
small proportion of it existing in a metal greatly modifies the
properties of that metal. Phosphorus forms several oxides, and these are
radicles of powerful acids, among which is _phosphoric acid_ that
combines with basic oxides to form _phosphates_.

We have now, in the few last paragraphs, set before the reader the
minimum of chemical knowledge that will enable him to follow the
_rationale_ of such processes of the modern treatment of iron and its
ores as we can here give an outline of. Although there are numberless
minerals from which some iron can be extracted, the name of _iron ore_
is confined to such as contain a sufficient amount to make the
extraction commercially profitable, and this requires that the mineral
should be capable of yielding at least one-fifth of its weight. The ores
are very abundant in many parts of the world, and they consist mainly of
_oxides_ and their _hydrates_, or of _carbonate_, or of carbonate mixed
with clay and silicates, sometimes also with coaly matters in addition.
The carbonate iron ores are often mixed with oxides. Each class of ore
is liable to be contaminated with phosphates and with sulphur. The
richest ore is the _magnetic iron ore_, which is found in enormous
masses in Sweden, Russia, and North America. It is an oxide containing
72·41 per cent. of iron. _Red hæmatite_ and _specular ore_ are varieties
of another oxide with 70 per cent. of iron: the former is a very pure
ore when compact. It is found in Lancashire, Cumberland, and South
Wales, and much has been imported from Spain, while America has abundant
supplies near Lake Superior. Specular iron ore forms brilliant
steel-like crystals which show the red colour of hæmatite only when
scratched or powdered. Elba was famous for this ore, which occurs also
in Russia and Sweden, and large deposits are met with in both North and
South America. Brown hæmatite is a hydrate of the former, containing 60
per cent. of iron; it abounds in France and Spain, where some kinds are
associated with a noteworthy quantity of _phosphate_ of iron. _Spathic_
or _sparry iron_ ore is, when pure, a collection of nearly colourless
transparent crystals, consisting of carbonate of iron; it contains about
48 per cent. of iron, and also some of the metal _manganese_, which last
circumstance makes it, as we shall see, particularly suitable for
producing certain kinds of steel—indeed it is sometimes called _steel
ore_. Large beds of it occur in Styria and Carinthia. _Clay iron stone_,
or _clay-band_, has been extensively mined in Britain. It is found
abundantly in Staffordshire, Yorkshire, Derbyshire, and South Wales. It
consists of carbonate of iron intimately mixed with clay. The quantity
of iron in some samples falls as low as 17 per cent., but it rises with
variations to as much as 50 per cent. Much of its importance arises from
the fact of its occurring in beds alternating with layers of coal,
limestone, and clay, so that the same pit is sometimes able to supply
firebricks for building the furnace, fuel for the smelting, and
limestone for the _flux_,—a combination of advantages that for long
enabled iron to be produced in England cheaper than elsewhere. The like
is true of the _blackband ore_, which, in addition to the same
ferruginous composition as the last, contains also so much combustible
or bituminous material that it can be _calcined_ (roasted) without
additional fuel. The deposits of _blackband_ in Lanarkshire and
Ayrshire, which were discovered only in 1801, have given great
industrial importance to the district. Yet another British ore must be
noticed, namely, the _Cleveland ironstone_ of the North Riding of
Yorkshire. This is a carbonate of a grey or bluish colour caused by the
presence of a little iron silicate. It contains also a considerable
amount of phosphorus.

How simple is the operation of obtaining iron from the ore has already
been stated—that it is necessary only to surround lumps of ore by fuel
in a fire urged by a natural or artificial blast, and then to hammer the
mass extracted from the furnace so as to weld together the scattered
particles of the metal, and at the same time squeeze out the associated
slag and cinders, in order to obtain a coherent malleable piece, which
can be reheated in a smith’s fire, and forged into any required form. It
is no wonder therefore that iron was so produced by the ancient Britons;
at any rate Cæsar found them well provided with iron implements and
weapons. No doubt the Romans brought their more advanced skill to the
working of the metal; but in the matter of treating the original ore,
the methods they pursued on an extensive scale in Britain were of the
rude kind already described. Indeed in localities where the Romans were
known to have carried on their operations, the remains of their workings
are almost always found on high ground, so that it may be inferred that
they relied upon the winds to fan their fires, and their operations were
incomplete and wasteful. The most extensive of them appear to have been
in Sussex and Monmouthshire, in which last county there are places where
the ground is in large areas covered by their cinders and refuse, and in
this about 30 or 40 per cent. of iron occurs, so that for some centuries
this material was found capable of being profitably reworked as a source
of the metal. Iron continued to be produced in England during the middle
ages with charcoal for fuel, but its export was forbidden, and whatever
steel was required had to be imported from abroad. Afterwards German
artisans were brought over for making steel, and soon afterwards the
importation of shears, knives, locks, and other articles was prohibited.
The native production of iron continued, and this consumed the forests
so rapidly for the supply of charcoal, that various Acts were passed to
restrain the iron-makers, in order to preserve the timber. In spite of
these, the arts of smelting and working iron advanced apace: bellows
were used for the blast, and then the works were brought down into the
valleys, where water power could be employed to work them. The scarcity
of charcoal fuel caused many attempts to supply its place with pit coal,
but these met with small success, partly on account of the coal
containing so much sulphur, and partly from the difficulty of obtaining
with it a sufficiently high temperature, especially as the blowing
apparatus was as yet very imperfect. At length, in the first half of the
seventeenth century, the problem was solved by Dud Dudley, whose process
was kept secret, but is believed to have consisted in supplying coal at
the top of a higher furnace, in such a manner that the coal was
converted into _coke_ by the heat of the escaping gases before it
reached the reducing zone of the furnace. This innovation was violently
opposed by the charcoal smelters, who persecuted the inventor in every
way, until their resistance was successful. But before the middle of the
next century coke was regularly used in iron smelting, the process
having been made successful by Darby at Coalbrookdale, and then many new
applications of cast iron came into vogue. Coke being a substance
burning less freely than charcoal, bellows were found inadequate to give
the necessary blast, and were displaced by _blowing cylinders_, actuated
at first by water wheels, but this uncertain and comparatively feeble
source of power was soon superseded by the steam engine, the “fire
engine,” for which, as we have seen, Watt obtained his patent in 1769.
The furnaces were not then all engaged in producing the fusible metal
now called _cast_ or _pig iron_ as are the huge blast furnaces we see at
the present time. Indeed it was much to the disgust of the old iron
smelter that occasionally his product turned out to be of the fusible
kind, unworkable by the hammer, which therefore he regarded as
worthless. At what date _cast iron_ was first used is uncertain; but
probably it was not long before the fourteenth century. The furnaces in
use up to that time were small square walled-in structures only 3 or 4
feet high, and their effect would not greatly exceed that of a smith’s
forge: but as improved blowing apparatus gave more power, they soon
became enlarged into oval or round brick towers from 10 to 15 feet high,
and they, like the small furnaces, could be made to yield either smith
iron or steel by modifying the charge and the manner of applying the
blast; while furnaces of dimensions exceeding a certain limit could no
longer be trusted to turn out malleable metal, but they produced instead
the cruder substance we call white pig iron, and this requires much
subsequent treatment before it is converted into malleable or “merchant
iron.” Nevertheless the demand for cast iron as such, and more
particularly the adoption of improved methods of deriving malleable iron
from it, caused further increase in the size and numbers of blast
furnaces, until in the early part of our century 30 feet was not an
unusual height, the highest one in England in 1830 attaining 40 feet.
The total make of pig iron in England was in that year nearly 700,000
tons, perhaps about fifty times as much as it was a century before, and
thirty years later (1860) it had risen to nearly 4,000,000 tons. These
figures show the extraordinary expansion of the British iron manufacture
in the earlier part of the century; and the still more extensive
applications of iron during the next twenty years had the effect of
almost doubling the produce in 1880, and of increasing also three-fold
the amount of foreign metal imported, raising it to 2,500,000 tons. The
reader will now, it is hoped, be prepared to follow with some interest a
brief account of the principal inventions which have brought about
results of such importance.

[Illustration:

  FIG. 17.—_Blast Furnace (Obsolete Type)._
]

[Illustration:

  FIG. 18.—_Section and Plan of Blast Furnace (Obsolete Type)._
]

Deferring for the moment any description of the latest blast furnaces,
we invite his attention to Fig. 17, which represents the furnace used in
the first half of our century, but which now is of an obsolete type,
Fig. 18 being the section and plan of the same. The lower part of Fig.
17 shows where the molten metal has been allowed to run out of the
furnace into channels made in dry sand; first a main stream, then
branches to right and left, each of these with smaller offsets on each
side of it. These smaller channels are the moulds for the _pigs_, so
called because of the fancied resemblance of their position with regard
to the branch that supplied them, to the litter of a sow. They are
easily broken off from the larger mass, and then form pieces about 3 ft.
long with a ᗜ-shaped section, 4 in. wide, the weight being from 60 to 80
lbs. This is iron of the crudest kind, and though it is often referred
to as “cast iron,” it is, as a matter of fact, not used in this state
for any castings, except those of the very roughest and largest kind: a
certain amount of purification is requisite in most cases. This is given
by fusing the metal—along with some form of oxide and often other
matters—in a _cupola furnace_, which is like a small blast furnace,
being from 8 ft. to 20 ft. high and uses coke for fuel with a cold
blast.

So far from being simply iron, pig contains a large and variable
proportion of other matters amounting often to 10 or 12 per cent.; and
these confer upon it its fusibility. The principal one is carbon, which
is found in the metal partly in the state of chemical combination with
it, and partly in the form of small crystals similar to those of
graphite or plumbago, disseminated through the mass. When there is a
comparatively small proportion of the carbon combined with the iron, the
substance is grey, and it can be filed or drilled or turned in a lathe.
In white cast iron the combined carbon predominates, or is sometimes
accompanied by scarcely any graphitic carbon; it is brittle and so very
hard that a file makes no impression. It fuses at a lower temperature
than the other varieties. A third kind is the _mottled_ cast iron, which
shows a large coarse grain when broken, and distinct points of separate
graphite particles; it is tougher than the others, and therefore when
cannon were made of cast iron this variety was preferred. The following
table giving the percentage composition of four samples of crude cast
iron will show their diversities.

 ┌─────────────────────────────────┬────────┬────────┬────────┬────────┐
 │                                 │  White.│  White.│Mottled.│   Grey.│
 ├─────────────────────────────────┼────────┼────────┼────────┼────────┤
 │Iron                             │   88·81│  89·304│   93·29│  90·376│
 │Combined carbon                  │    4·94│   2·457│    2·78│   1·021│
 │Graphite, or uncombined carbon   │     ...│   0·871│    1·99│   2·641│
 │Silicon                          │    0·75│   1·124│    0·71│   3·061│
 │Sulphur                          │   trace│   2·516│   trace│   1·139│
 │Phosphorus                       │    0·12│   0·913│    1·23│   0·928│
 │Manganese                        │    5·38│   2·815│   trace│   0·834│
 └─────────────────────────────────┴────────┴────────┴────────┴────────┘

The reader will observe that the last item in the table above is a
substance that he has not yet made the acquaintance of, namely,
_manganese_. This is a metal which in many of its chemical relations
much resembles iron, and ferruginous ores usually contain a greater or
less proportion of it. Manganese is of great importance in the
manufacture of steel, as we shall presently see; but as a separate metal
it has no application, and is obtainable in the metallic state with much
difficulty. One of its oxides has however very extensive applications in
the chemical arts, and others form acid radicles, which in combination
with potash or soda give rise to useful products. The well-known
“Condy’s fluid” is a solution of one of these.

We have seen how malleable iron or steely iron may be directly obtained
from the ores, but it has been found that on the large scale it is
necessary and more economical to operate on the pig iron produced by the
blast furnaces in such a manner as to remove the greater part of the
foreign substances.

[Illustration:

  FIG. 19.—_Section of a Reverberatory Furnace._
]

The first step in the conversion of the pig iron usually taken has been,
and to a certain extent even is still, to remelt the metal in what is
termed a _finery furnace_, a kind of forge in which a charcoal fire is
urged by a cold blast, and so regulated that an excess of oxygen is
supplied, or rather more than would suffice to convert all the carbon of
the fuel into carbonic acid; although this is perhaps not absolutely
necessary, as carbonic acid would itself supply oxygen by suffering
reduction to carbonic oxide. At any rate the melted metal is exposed to
an oxidizing atmosphere and constantly stirred. Many different
arrangements of the furnace and details of the process have been used.
For instance, where the finest quality of malleable iron was not aimed
at, coke has been the fuel employed, and many shapes of furnaces, etc.,
have been contrived, and various additions of ores, oxides, etc., made
to the charge, according to local practice and the nature of the crude
iron. One marked effect of the operation is the final removal of nearly
all the _silicon_, which is burnt or oxidized into _silica_, and this at
once unites with oxide of iron, which is also formed, to produce a
readily fusible slag of silicate of iron, and in the production of this
silicate any sand attached to the pig will also take part. Much of the
carbon, amounting sometimes to more than half, is also eliminated as
carbonic oxide, and of what is left but little remains in the graphitic
state. The action on the phosphorus is usually less marked, but there is
always a notable reduction of the quantity. The sulphur is also lessened
in some degree, although when coke is used, the fuel has the
disadvantage of itself containing sulphur, phosphates, and other
deleterious matters. Sometimes a little lime is added to the charge to
take up the sulphur from the coke. The operation lasts some hours, the
fused metal being frequently stirred with an iron rod, until it assumes
a pasty granular condition, when the workman gradually collects it upon
the end of the rod into a ball of about three-quarters of a cwt. in
weight. These balls, or _blooms_ as they are called, are removed from
the furnace while still intensely hot, and at once submitted to powerful
pressure by means of some suitable mechanical arrangement, the effect
being to squeeze out the liquid slag and force the particles of metal
together by which the whole becomes partially welded into a more compact
mass. Then this mass is, while still hot, either hammered with gradually
increased force of the strokes, or in the more modern practice, passed
between iron rollers (these we shall presently describe), by which it is
shaped into a bar. The bars are afterwards cut into lengths, reheated
without contact of fuel, again hammered or re-rolled; and this process
is several times repeated when the best product is required. During the
first treatment of the blooms, and also in the subsequent hammering or
rolling, the oxygen of the atmosphere acts on the surface of the glowing
metal, so as to cover it with thin scales of oxide, and these, carried
into the interior of the mass, will give up their oxygen to any residual
silicon, carbon, etc., producing a little more slag, carbonic oxide,
phosphate of iron, etc., which by the pressure of the hammers or rolls
are ultimately forced out of the metal. It will be observed that in
producing the pig iron the chemical action is the separation of oxygen
from the metal, while conversely an oxidizing action is set up in the
finery and subsequent treatment, in order to burn off the foreign
ingredients. But this cannot be done without at the same time
re-oxidizing some of the iron itself, of which therefore there is always
a considerable loss, by its formation into slag (silicate), cinder,
foundry scale (oxide), etc. The quantity of iron lost depends of course
on many conditions, such as the care exercised in the operations, but it
occurs in all the processes that have been devised for the conversion in
question, even in the most modern: its amount may be taken to range
between 10 and 20 per cent. The reader is requested to bear in mind the
nature of the chemical actions that have just been described, for in
even the most recently invented processes the principle is the same in
nature and effect. So completely can the foreign elements be eliminated
by this, or some analogous process, such as we shall presently mention,
that the finest Swedish bar iron contains more than 99½ per cent. of the
metal, and in some cases only a very little carbon and a mere trace of
phosphorus remain, amounting together to less than 1 part in 2000. Such
metal is made from very pure ore, containing no sulphur and scarcely any
phosphorus, while charcoal is the fuel used in all the operations. As
already mentioned, the objection to the use of coke is the sulphur,
phosphates, and siliceous matters it contains. Toward the close of the
eighteenth century an invention came into use which obviated the
disadvantages of the cheaper fuel for converting crude iron. This was
the puddling furnace, brought into use after much experimenting by Henry
Cort in 1784. In it the pig iron is fused in a _reverberatory furnace_,
the form of which will be understood from Fig. 19, which is a diagram
showing such a furnace in section, where _f_ is the fire, _a_ an
aperture at which the fuel is introduced, _p_ the ash pit, _b_ is a low
wall of refractory material called the “bridge,” over which the flame
passes, and is by the low arched roof reflected or _reverberated_
downwards upon the charge, _c_, which is laid on a _hearth_, or iron
floor, having spaces below it where air circulates in order to prevent
it becoming too hot. In Cort’s original arrangement the bed of the
hearth was formed of sand, which gave rise to much inconvenience by
producing a quantity of the very fusible silicate of iron, that speedily
attacked the masonry of the furnace, and therefore a very important
improvement was devised some years later by S. B. Rogers, who made the
bed of his furnace of a layer of oxide of iron, spread on a cast iron
plate 1½ inches thick. In later times it has become usual to cover the
iron hearth with certain other refractory mixtures varied according to
circumstances, of oxide, ore, cinder, lime, etc. There is one of these
mixtures significantly designated “_bull-dog_” by the workmen. We may
mention here that it has, in more recent times, when very high
temperatures are obtainable, been found unnecessary to cause even the
flame to come into contact with the substances on the hearth, inasmuch
as the heat radiated from the flame and the intensely heated roof of the
furnace suffices, so that in consequence of this the roofs are now
constructed nearly flat. In the puddling furnace the melted metal is
constantly stirred, and no little skill is required to regulate the fire
by the damper on the chimney, and to admit the proper amount of air to
mix with the flame. The pig iron softens and melts gradually, until at
length it becomes perfectly liquid, at which stage it swells up and
appears to boil owing to the escape of carbonic oxide in numerous jets,
which burn with the characteristic pale blue flame. The puddler then
briskly stirs the mass to cause more complete oxidation of the carbon,
silicon, etc., by bringing the superficially formed oxide of iron into
the interior. As the iron loses its carbon, it assumes much the texture
of porridge, consisting of pasty lumps of malleable iron implexed with
the liquid slag (silicate of iron, etc.) which drips from the spongy
balls as the puddler collects them at the end of his stirring rod, as in
the finery operation. The next thing is to run the mass immediately
between powerful rolls (puddling rolls) by which the slag is squeezed
out, as before, and finally through the _finishing rolls_ that shape it
into bars or plates.

When a comparatively impure pig iron is used or when a better quality of
malleable metal is desired, the crude iron is submitted to a preliminary
treatment before puddling. This treatment, by a technical distinction,
called _refinery_, is practically identical with the _finery_ process
already described, except that instead of being collected into blooms,
the fluid metal is run out to form a layer 2 or 3 inches thick, and
this, before becoming quite solid, is suddenly cooled by having water
thrown over it, the result being a white, hard, brittle mass, which
broken into pieces is ready for the puddling furnace.

The operation that has been described is known as _hand puddling_, in
contradistinction to later methods in which it has been sought to
substitute some form of machine that will produce the same result
automatically, such as revolving furnaces, etc. It has been found
difficult to maintain these in good working order, and in England at
least mechanical puddling has never found much favour, but in the great
iron works of Creusot, in France, large revolving furnaces were in use
about 1880, which could turn out 20 tons of converted iron in 24 hours,
whereas the old hand puddling furnaces could in the same period produce
only 2½ or 3 tons, with two sets of men, the puddler and one assistant.
Of these mechanical furnaces it is unnecessary to give any account,
especially as the puddling process itself has nearly gone out of use,
having been superseded by more economical methods.

The use of rolls for treating the product of the puddling furnace, and
for making it into bars, was also an invention of Henry Cort’s, for
which he obtained a patent in 1783. This was in many respects an immense
improvement on the older system of hammering; it is still practised, and
by it shapes can be given to the metal scarcely possible on the older
system, while the tenacity of the metal is increased by the uniformity
given to the grain. The difference of chemical composition between cast
and wrought iron the reader has already been made acquainted with, and
there is quite as great a difference in their textures. The former, when
broken across, shows a distinctly crystalline structure, which we may
compare to that of loaf-sugar, while the latter exhibits grain, not
unlike that of a piece of wood. This fibrous structure depends upon the
mechanical treatment of the iron, and in rolled bars the fibres always
arrange themselves parallel to the length of the bar. Fig. 20 shows this
fibrous structure in a piece of iron where a portion has been wrenched
off. Like wood, wrought iron has much greater tenacity along the fibres
than across them; that is, a much less force is required to tear the
fibres asunder than to break them transversely. Consequently, to obtain
the greatest advantage from the strength of wrought iron, the metal must
be so applied that the chief force may act upon it in the direction of
the fibres. Near the beginning of our article on IRON BRIDGES (_q.v._)
the reader will find some illustrations of the very different resisting
powers of cast and wrought iron.

[Illustration:

  FIG. 20.—_Fibrous Fracture of Wrought Iron._
]

Nothing in the way of inventions can be compared to those of Cort’s as
to the effect they have had in promoting the iron industry, until we
reach a period some years after the middle of our century; but we must
not neglect to recognize the scarcely inferior importance of Rogers’
improvement. Singularly enough, neither of these men reaped any benefit
from his inventions. Cort died in the last year of the eighteenth
century, quite a poor man, having been supported only by a niggardly
pension of some £160 from the Government, and leaving his family in
indigent circumstances. Yet a most eminent authority on iron questions
(Sir W. Fairbairn) estimated—some time about the middle of our era—that
the two inventions of Cort’s alone, the rolling-mill and the
reverberatory puddling furnace, had by that time added to the wealth of
Great Britain by an amount equivalent to six hundred million pounds
sterling. For many iron-masters had profited by these inventions,
amassing very great fortunes, in some instances also acquiring titles of
honour. Clearly to Cort and Rogers may be applied the _sic vos non
vobis_ saying.

We shall now turn to the improvements that have been effected in the
blast furnace, and of these none perhaps has been more marked than that
made by Neilson, when in 1828 he substituted heated air for the ordinary
cold air that had before always supplied the blast. It will be
remembered that the heat is due to the combination of only the oxygen of
the air with the carbon of the coke, but the greater part of the air—the
four-fifths of nitrogen—take no part in the action, beyond abstracting a
large proportion of the heat; but when the air is heated to a high
temperature before entering the furnace, the cooling effect of the
nitrogen is greatly obviated, and consequently a much higher temperature
is obtained at the place of combustion, and the requisite intensity of
heat is at once produced, which is most effective in completing the
fusion and separation from each other of the slags and iron, and also in
accomplishing the reduction of the oxide. But Neilson found that the net
result of burning some fuel to heat the air before entering the furnace
was a great economy of the total fuel required for smelting the ore. He
had to encounter many difficulties in carrying his invention into
practice; the iron ovens first used for heating the air were rapidly
oxidized; and when thick cast iron pipes were substituted, these were
liable to leak at the joints on account of the expansions and
contractions caused by changes of temperature. Then the new invention
had as usual to contend with established prejudices and misconceptions;
but it soon came into use in Scotland, where it effected a great saving;
inasmuch as it was found possible to use with the hot blast raw coal of
a certain kind, plentiful in Scotland, because the heat retained by the
ascending gases sufficed to convert the coal at the top of the charge
into coke.

It will be remembered that the active agent in the reduction of the ore
is the carbonic oxide gas formed by the incomplete combustion of the
carbon of the fuel; or what comes to the same thing, the absorption by
carbonic acid first produced of another proportion of carbon. The carbon
oxide robs the iron oxide of its oxygen to become itself changed into
carbonic acid. In reality however the action is more complex than this
in its chemical relations; for instance, metallic iron will under
certain circumstances act conversely on carbonic acid, and rob it of
half its oxygen. The net result of the reactions between carbon, iron,
iron oxide, and these gases depends mainly upon the temperature and
pressure and upon the relative quantities of each substance present. In
the gases escaping from the blast furnace there is always a large
quantity (nearly one-third) of carbonic oxide. At the blast furnaces in
work during the first half of our century the combustible gases were
allowed to burn to waste as they issued from the top of the furnace, in
the manner shown in Fig. 17, and at night the flames used to form a
weird and striking feature in the prospect of an iron-smelting region.

Instead of allowing the escaping gases to burn to waste, it became the
practice about 1860, and so continues, to draw them off and burn them
under steam boilers or use their flames for heating the blast. An
effective method of withdrawing the gases is shown in Fig. 21, which is
a section through the upper part of a smelting furnace, with the “cup
and cone” arrangement. The mouth of the furnace is covered by a shallow
iron cone _a_, open at the bottom, into which fits another cone _b_,
attached to a chain _c_, sustained by an arm of the lever _d_, which is
firmly held in position by the chain _e_, and is also provided with a
counterpoise _f_. When the mouth of the furnace is thus closed, the
gases find an exit by the opening _g_, seen behind the cones, and
leading into a downward passage, through which they are drawn by the
draught of a tall chimney to the place where they are burnt. The charge
for the furnace is filled into the hopper _a_, and at the proper time
the chain, _e_, is slackened when the weight of the material resting on
the suspended cone overcomes that of the counterpoise, and the charge
slides down over the surface of the cone _b_, which is immediately drawn
up again by the counterpoise, so that the opening into the air is at
once closed.

[Illustration:

  FIG. 21.—_Cup and Cone._
]

The march of improvement in the blast furnace has been characterized
particularly in Britain and the United States by a great increase of
dimensions, which is found to promote economy in fuel, etc. In the
former country the furnace of the latter part of our century is commonly
from 70 to 80 feet high, and some have even been built with a height of
more than 100 feet, while in the States the tendency to build very high
furnaces is still more marked. A single large furnace may turn out as
much as 1,500 tons of pig iron in a week, and some in America, it is
said, actually produce as much as 2,500 tons. The more usual output of a
blast furnace is however much less than these amounts; but if we say
only one-half, or even one-third of these quantities, a state of things
is indicated very different from what obtained about 1837, when the best
Welsh furnaces produced only 200 tons a week. If we go back to the
beginning of the century, the difference is much more marked, for the
blast furnaces of that period could turn out only about 30 tons in a
week.

The proportions of fuel, ore, and limestone charged into the furnace
vary greatly according to the composition of the ore, the quality of
iron aimed at, and the practice of each manufacturer. It is usual
previously to calcine the carbonate ores and others also, in order to
expel the carbonic acid and the moisture, of which last all contain a
considerable amount: and sometimes the limestone is mixed with the ore
to undergo this preliminary process. The charge being conveyed from the
roasting kilns to the blast furnace while still hot effects an obvious
economy of fuel in the latter. In the case of hæmatite ore the
quantities of materials in one charge may be something like 54 cwt. of
ore, 9 cwt. of limestone, and 33 cwt. of coke. It is quite common to use
mixtures of different kinds of ore, so as to modify the quality of the
product according to particular requirements. The use of the limestone
is to take up silica, and the slag is found to consist mainly of
silicates of lime and alumina. The amount flowing from a blast furnace
of course varies much according to the conditions, and is larger than
would commonly be supposed; for the production of one ton of pig iron
involves the production of from ½ to 1½ tons of slag.

Fig. 22 represents in section the later type of blast furnace, which of
course is circular in plan. Its height may be taken as 80 feet, and the
diameter at the widest part of the interior as 22½ feet, narrowed to 20
feet near the top. The lowest portion, C, is called the _crucible_, the
bottom of which is the _hearth_, both formed of the most refractory
materials obtainable. The conical widening, B, above the crucible is the
_boshes_, and at the top is seen the “cup and cone” apparatus already
described, A, surmounted by the short cylindrical iron mouth, through
apertures in which the charges are tipped from the gallery, D, these
having been raised there in small trucks by hydraulic or other
elevators. The escaping gases leave the furnace by the exit, E, which
leads into the “down-come,” G, and they are conducted from it to the
“regenerative stoves” and dealt with as presently to be described. Our
section represents the masonry of the furnace as sustained by pillars,
P, at the outside of the lower part; these pillars support a strong ring
of iron plates upon which the wall rests. This arrangement has the
advantage of allowing the workmen the greatest freedom of access to
parts about the crucible, which require much attention. Here, at the
lowest part, is an aperture from which the liquid iron is allowed to run
out every five or six hours, it being plugged in the meantime by clay
and sand. The slag being much lighter than the iron, floats above it,
and runs off at a higher level over the _tympstone_. Opening into the
hearth are several orifices to admit the hot blast from the nozzles of
the _tuyères_, which of course do not project into the furnace itself;
but they are so near to the region of intensest heat that they would be
rapidly destroyed unless they were surrounded by a casing through which
a current of water is constantly running. The _tuyères_, of which there
may be 3 or 5, are supplied from the pipe seen at K. The earlier plans
of heating the air did not permit of a very high temperature being given
to the hot blast, about 600° F. being the limit; but the “regenerative”
stoves can supply a blast of more than 1,600° F., or not far below the
melting point of silver. Another great increase has been in the pressure
of the blast; 2 or 3 lbs. per square inch sufficed in the earlier
practice; but the lofty modern furnaces have to be supplied with the
blast at a pressure of 10 lbs. per square inch, and over. Even when
comparatively low pressures were the rule, a large ironworks required
much blowing power. The works formerly at Dowlais, in South Wales, for
instance, had an engine of 650 horse-power for the blowing engine, in
which a piston of 12 feet diameter moved in a cylinder 12 feet in
length. The quantity of air that passes into a blast furnace amounts to
thousands of tons per week, its weight being much greater than that of
all the ore, coke, and limestone put together.

[Illustration:

  FIG. 22.—_Section of Blast Furnace._
]

It need scarcely be said that great care and expense are bestowed on the
construction of these furnaces. Only the best and most refractory
materials, such as firebricks, are used for the lining, and the exterior
is a casing of solid masonry, strengthened with iron bands. When a new
furnace is finished it takes a month or six weeks to put it into
operation; but when this is done it will remain in action night and day
continuously for a long period—perhaps for eight or ten years—before the
necessity for repairs requires a “blow out.” And the blow out and
restarting, without the cost of repairs, entail an outlay of several
hundred pounds.

The gases leaving the throat of the furnace consist mainly of nitrogen
and a little carbonic acid, together with about one-third of their
volume of the combustible gases, carbonic oxide, and some hydrogen; but
these last do not leave the furnace in an ignited state, because the
oxygen there has already been consumed. They are conducted by the
“down-come” pipe, G, Fig. 22, to a point at which, by means of a valve,
they can be directed to one or other of two circular towers entirely
filled with firebricks, arranged chequerwise, so as to form innumerable
passages between them. The furnace gases are admitted at the bottom of
the Cowper tower, or “regenerative stove,” into a flue to which a
regulated quantity of air has access, and there they are fired: the
flame ascending the flue to the upper part of the tower, thence
descends, communicating its heat to the firebricks, which soon acquire a
very high temperature, especially where the flame first enters, and the
burnt gases leave the tower for a tall chimney, leaving most of their
heat in the firebricks. When this action has continued for a sufficient
time, the connection of the regenerator with the throat of the furnace
is cut off, and the escaping gases are directed into the other
regenerator, and at the same time the blast from the blowing engine is
made to ascend among the firebricks of the first, where gaining
increasing temperature as it ascends—the stove being hottest at the
top—the air leaves the tower to be conducted to the _tuyères_ at such
high temperature as already mentioned. While the one regenerator is thus
heating the blast, the other is in its turn accumulating heat from the
flames of the escaping gases; and thus they are worked alternately, the
action being constantly reversed after suitable intervals.

When iron is combined with a much smaller proportion of carbon than in
cast iron, and contains little or no graphitic or uncombined carbon, we
have the very useful compound known as steel. In the earlier half of the
century it was customary to distinguish steel from malleable iron on the
one hand, and cast iron on the other. If the compound contained from 0·5
to 1·5 per cent. of carbon, it was called steel by some authorities,
while others extended these limits a little on either side. Later it was
found that the presence of elements other than carbon can confer steely
properties on iron, and indeed it is possible to have a metal containing
no carbon, but possessing the characteristic properties of steel. Sir
Joseph Whitworth proposed to classify a piece of metal according to its
tensile strength, without any regard to either its chemical composition
or its mode of manufacture: if it could not bear more than 30 tons per
square inch it should be considered iron, but if it had a higher tensile
strength, it should then be regarded as steel. To estimate the
engineering value a figure depending upon the elongation or stretching
of the specimen before breaking was to be added to the number of tons of
the breaking load. This stretching power of steel is in some cases of as
much importance as the tensile strength: the ordnance maker, for
instance, considers a steel with a breaking strength of 53 tons under an
elongation of 5 per cent. as _for his purposes_ to be rejected: while a
specimen showing a breaking strain of only 30 tons along with an
elongation of 35 per cent., on 2 inches of length, he will regard as
good. The tensile strength of steel depends in part on its composition,
in part on the mode of manufacture, and in part on the subsequent
treatment. The _average_ tensile strength of a wrought iron bar per
square inch of section is about 25 tons (30 is the maximum); while the
like average for steel is 43 tons, and some kinds of cast steel will
bear nearly 60 tons. Steel bars of a certain temper subjected by Sir
Joseph Whitworth to a process of hardening in oil showed a tensile
strength of even 90 tons per square inch. These figures will suffice to
show the great utility of steel in structures and machines. But steel
has besides a characteristic property which makes it extremely valuable
in a great variety of applications, namely, its capability of being
_tempered_. If a piece of steel is heated to dull redness and suddenly
cooled by plunging it into cold water, it becomes so extremely hard that
it cannot be acted on by a file; nay, its hardness may be made to rival
that of the diamond, which is the hardest substance known. Now by a
second operation this hardness can be reduced to any required degree:
this is done by re-heating the metal to a certain moderate degree
between 430° F. and 630° F. and again cooling it by immersion in some
cooling medium. In this “letting down” process, it is the highest
temperature that produces the greatest softening, and the properties of
the tempered steel will depend upon the precise degree to which the
metal has been reheated. For example, if the product be required for
making into sword blades, or watch-springs, and to possess much
elasticity, the proper temperature is between 550° F. and 570° F.; but
if the steel is to be suitable for saws the temperature must range
within a few degrees of 600° F., according to the fineness of the tool
intended; a lower temperature would give a metal too hard for them to be
sharpened with a file. On the other hand, sharp cutting instruments and
tools for working metals are obtained hard by tempering at lower degrees
than springs. In practice the index of the temperature is taken from the
colour of the film of oxide that gradually forms on a polished surface
of the metal as the heat is raised, and begins by a very pale yellow (at
430° F.), passing through deeper shades into brown, then through purple
into deep blue (at 570° F.), etc. The reader will now see why watch and
clock springs have their deep blue colour, and he can observe for
himself the whole series of colours by very gradually heating a piece of
polished steel over a small flame.

If we compare the chemical composition of wrought iron and of cast iron
with that of steel as regards the content of carbon, we see at once that
steel holds an intermediate position, so that if in the puddling furnace
we could arrest the decarbonization at a certain point we should obtain
steel; or if, on the other hand, we could put back into chemical
combination with the decarbonized wrought iron a due percentage of
carbon we should in that way also obtain steel. And it will be observed
that the oldest primitive furnaces could not have failed sometimes to
have produced steel as the net or final result of such actions. In fact,
steel always has been and still is produced on one or other of these two
principles, applied in divers ways, but severally and distinctly
directed to that end. Of the many more or less modified processes of
steel-making that have been in use, we need here but briefly mention a
few which were _the_ processes of the first sixty years of our century,
and are to a considerable extent still in operation, although eclipsed
in importance by two other processes that, since the date referred to,
have been supplying the metal in enormously increased quantities, and
which will have to be particularly described.

The most usual of the older processes of steel-making, still carried on
at Sheffield and elsewhere, is known as the _cementation process_: it
consists in heating bars of the best wrought iron in contact with
charcoal, at a high temperature, for three or four weeks. At Sheffield
the iron bars and charcoal are packed in alternate layers into troughs
14 ft. long by 3½ ft. deep and wide, constructed of slabs of siliceous
sandstone 6 in. thick. The last layer of charcoal at the top is covered
to a certain depth with a layer of refractory matter, and the flames
from a furnace beneath are made to envelop the stone troughs or _pots_,
as they are technically called, for a period of a week or more according
to the thickness of the bars operated upon. These are generally 3 in.
broad and from five- to six-eighths of an inch thick. When it is found
by withdrawing a test bar for examination that the operation is
complete, the fire is gradually diminished and the whole allowed to cool
slowly, which requires about a fortnight. Instead of only charcoal, a
mixture of powdered charcoal or soot with a little salt has been used by
some makers—which mixture, technically called _cement powder_, has given
its name to the process. In some works 16 tons or more of iron are
treated in one operation. The bars are found unchanged in form, but
increased in weight by perhaps 27 lbs. per ton, for carbon has combined
with the iron, being apparently transferred in the iron from one
particle to another. The surface of the bars becomes rough and uneven
from a multitude of blebs or blisters, and hence they are called
_blister bars_, and the steel of which they now consist is named
_blister steel_. In this conversion we may suppose that the iron at its
outer surface first enters into combination with carbon taken from the
carbonic oxide gas, which would be produced by combustion of the
charcoal with the limited quantity of air in its interstices, and the
oxygen thus set free would immediately seize again on the surrounding
charcoal, and by repeated changes of this kind in which the oxygen acts
as a carrier of carbon to the iron, in which it is transferred inwards
from particle to particle. The cause of the blisters has been much
discussed: probably the cause is the formation and escape of a volatile
compound of carbon and sulphur at the surface of the soft metal; for it
is known that nearly the whole of the little sulphur in the wrought iron
disappears in the cementation process. Blister steel is never
homogeneous, for near the surface it always contains more carbon than
within; the bars are therefore broken up into short lengths which are
carefully assorted, bound together with wire, heated, welded together
under a hammer or by rolling, and finally formed into a bar, which is
stamped with the outline of a pair of shears, and is then known as
_shear steel_, because this product was generally found the most
suitable for making the shears used in dressing cloth.

Another method of dealing with the blister steel is to charge crucibles
or pots having covers with 50 or 100 lbs. weight of the broken-up bars,
and subject the crucibles to a strong heat in a reverberatory furnace,
when the metal melts, and at the proper moment the contents of a great
number of pots are almost simultaneously poured into a mould to form an
_ingot_. The result is a very uniform steel of the finest texture, known
and highly esteemed as _cast steel_ or _crucible steel_. This steel is
much more fusible than iron, but less so than cast iron.

The production of steel by arresting at a certain stage the
decarbonizing of cast iron in the puddling furnace requires much
experience on the part of the workman, who has to learn when the desired
point has been reached by certain indications, such as the appearance of
the flame, or by the examination of a small sample of the fluid metal
withdrawn and rapidly cooled. Various additions to the charge in
definite proportions are generally made, such as scales of iron oxide,
or a quantity of an oxide ore (hæmatite, etc.) or other materials, the
most essential for a good product consisting of a little manganese in
some form. The result is _puddled steel_; and this, like blister steel,
can be converted into cast steel by fusion in crucibles, running into
ingot moulds, and subsequent treatment by hammering, pressing, rolling,
etc. In 1864 puddled steel was described as an article of great
commercial importance, but this it soon lost by the introduction of
simpler, cheaper, and more reliable processes. The methods and
improvements proposed for the production of steel have been exceedingly
numerous, as is shown by the records of the English Patent Office alone,
which contain up to the end of 1856 specifications of ninety-two patents
for different steel-manufacturing processes, while from 1857 to 1865,
the epoch-marking period of steel making, seventy-four more patents were
obtained for this purpose. It would be quite beyond our limits to make
special reference to these, and to the numerous patents which have since
been granted, but there is one of great importance in steel-making which
must be mentioned, and that is the patent for the employment in the
cementation process of carbide of manganese, taken out by J. M. Heath in
1839. This made England almost independent of the former large
importations of Swedish and Russian iron, and it caused an immediate
reduction of £40 in the price per ton of good steel, effecting a saving
which up to 1855 is calculated at not less than £2,000,000. Heath was
one of those who fail to benefit by their inventions, for his was boldly
appropriated by another person who took advantage of a verbal flaw in
the specification, and Heath did not obtain any redress from the law
courts until, after ten years’ litigation, a majority of Exchequer
judges reversed all the previous decisions against him (1853). In the
meantime the man had died, but as the patent was about to expire his
widow was on petition granted an extension of it for seven years. The
nature of the influence of manganese on steel-making has not been fully
explained, and there is some diversity of opinion on the subject, as it
is said—on the one hand, merely to remove or counteract the injurious
effects of sulphur or phosphorus; on the other, to impart to the steel
greater ductility, strength, and power of welding, tempering, etc.

The manufacture of _crucible_ or _cast steel_ has been carried on at
Essen in Prussia by the firm of A. Krupp & Co., on a scale surpassing
anything attempted elsewhere,—theirs being the largest steel-works in
the world, and remarkable for the variety and excellence of its
products. It began in so small a way that it is said only a single
workman was employed. To the Great Exhibition of 1851, at London,
Krupp’s firm sent a block of crucible cast steel weighing 2¼ tons, a
larger mass of the metal than had ever been shown before, and looked
upon with no little astonishment, for at that time steel was a precious
commodity, the price of refined steel ranging from £45 to £60 per ton.
At the next London Exhibition, in 1862, the Essen Works showed a block
of cast steel 20 tons in weight, and at the Vienna Exhibition of 1873,
one of 52 tons. This casting, which was first made of a cylindrical
shape, was forged into an octagonal form under an immense steam-hammer,
larger than the Woolwich hammer described on a previous page, for the
weight of the moving part is no less than 50 tons. This huge mass of
cast steel was of the finest quality; the forging into the prismatic
form was to show its malleability, for it was intended for the body of a
gun to have a bore of 14 inches. Since the period referred to, ingots of
more than 100 tons have been cast. That shown at Vienna was the product
of some 1,800 crucibles, each containing 65 lbs. of melted steel, which
had to be poured into the mould in a regular and continuous stream, so
that the metal might solidify into a perfectly uniform mass. Such work
can be done only by trained men, who act in regular ranks with military
precision, and in pairs emptying their crucibles into channels
previously assigned, then filing off to the other end of the rank to
receive another crucible, while the pair of men who were behind are
pouring out theirs, and so on in succession. The crucibles are emptied
into a number of channels formed of iron lined with fire-clay, and
leading down into the mould. Many precautions have to be taken to ensure
the regular progress of the operations, and all the time required to
fill the huge moulds may be counted by minutes.

The headpiece to our chapter on Fire-Arms gives but a very inadequate
idea of the magnitude of the Essen Works about 1870. A better notion
will be obtained from a few figures which we select from a list giving
some of the contents of the Essen Works in 1876. There were 1,109
furnaces of various kinds, of which 250 were for smelting; 77 steam
hammers, 294 steam engines, 18 rolling mills, 365 turning lathes, and
700 other machine tools; 24 miles of ordinary gauge railway for traffic
within the works; together with 10 miles of narrow gauge railway; 38
miles of telegraph lines, with 45 Morse apparatus, etc. (J. S. Jeans’
_Steel: its History, etc._, 1880). These figures belong, be it observed,
to the state of things in 1876; but we learn from a later authority that
in 1894 these works employed 15,000 men, and we must suppose that the
plant has been proportionately increased since the earlier period, when
10,000 men were employed.

In the year 1854 a regular system of records began to be kept of the
amounts of coal and ores raised in Great Britain, and also of the
quantities of the various metals produced. These show that in 1894 very
nearly three times as much coal was raised as in 1854, and that in the
same period the quantity of British pig iron smelted annually had
increased four-fold; these increases look small when compared with the
expansion of the steel production in Britain within the same period of
forty years, for this had enlarged _thirty-fold_. This extraordinary
development is attributable to the introduction of two processes by
either of which various steels of excellent quality, and adapted to a
great range of applications, can be produced cheaply and with certainty.
These processes are respectively known as the Bessemer and the Open
Hearth, and the reader should observe that with the main principles
involved in these he has already been made acquainted.

Henry Bessemer, who first saw the light in England in 1813, may be said
to have been born an inventor, for his father was one before him—a
Frenchman employed in the royal mint at Paris, afterwards appointed by
the Revolutionary authorities to superintend a public bakery; on an
accusation of giving short weight, thrown into prison, from which, and
probably from the guillotine, he escaped, and found employment in the
English mint. Subsequently he devised some notable improvements in the
art of producing letterpress type, and for many years carried on a
prosperous business as a typefounder. The son developed inventive
faculties at a very early age: in lathe engraving, dies, dating stamps,
etc. His name became familiar to everyone by his production of the
metallic powder long known as “Bessemer’s Gold Paint.” It became known
to Bessemer that the raw material of this substance, which was then sold
at £5, 10_s._ per lb., really cost only about one shilling per lb., and
he set himself to discover its composition and mode of manufacture. He
succeeded in this so well that he could produce the article at the
insignificant cost of four shillings a pound, and his first order for a
supply of it was at the rate of £4 per lb., and the business was
continued, realising profits of something like 1,000 per cent. at first.
For this article no patent was taken out, but Bessemer himself, assisted
by two trustworthy workmen, carried on the manufacture in secret, and he
some time afterwards rewarded the fidelity of his men by handing over
the business to them as a free gift. Then he took out patents for
improvements in the manufacture of oils, varnishes, sugar, plate glass,
etc. Several of his machines for these purposes were shown at the London
Exhibition of 1851. Bessemer is said to have obtained altogether some
150 patents, including those granted for inventions connected with our
subject. He may be regarded as the type of the very fortunate inventor,
since on the patents of the one process we are going to describe he
ultimately obtained royalties to the value of more than £1,057,000, and
this irrespective of profits derived from commercially working it
himself.

At the time of the Crimean War, Bessemer had some experiments made at
Vincennes with cylindrical projectiles he had devised for firing from
smooth-bore guns, yet so as to impart to the projectile at the same time
rotation about its axis. The experiments were successful, but it was
pointed out that the guns of cast iron then in use would not bear heavy
projectiles, and he was induced, at the suggestion of the Emperor
Napoleon III., to undertake some researches with the view of finding
metal more suitable for artillery. Bessemer, having then little
knowledge of the metallurgy of iron, applied himself on his return to
England to the study of the best books on the subject, visited the
principal iron-working districts, and began a series of experiments at a
small experimental installation he set up in London. There, after
repeated failures, he did at length succeed in producing a metal much
tougher than the cast iron then used, and a small model gun was
submitted to the Emperor, who encouraged Bessemer to persevere with his
experiments; which he did, though the expense was a great tax on his
capital, continued as the experiments were for two years and a half. But
by this time he had acquired a knowledge of many important facts, and
these gradually led him to the experimental realization of the idea he
had conceived, but only after many trials in which several thousand
pounds were expended. At length the agenda of the British Association
for the Cheltenham meeting of 1856 announced that a paper would be read
by H. Bessemer, entitled “The Manufacture of Iron and Steel without
Fuel.” It will be easily understood that a title in such terms would
give rise to much derisive incredulity; and we may imagine the
iron-masters on that occasion crowding into Section G, while asking each
other in the spirit of certain philosophers of old, “What will this
babbler say?” Some of what he did say may here be quoted, as at once
explanatory and historically memorable.

“I set out with the assumption that crude iron contains about 5 per
cent. of carbon; that carbon cannot exist at a white heat in the
presence of oxygen without uniting therewith and producing combustion;
that such combustion would proceed with a rapidity dependent on the
amount of surface of carbon exposed; and lastly, that the temperature
which the metal would acquire would be also dependent on the rapidity
with which the oxygen and carbon were made to combine; and consequently,
that it was only necessary to bring the oxygen and carbon together in
such a manner that a vast surface should be exposed to their mutual
action, in order to produce a temperature hitherto unattainable in our
largest furnaces.

[Illustration:

  FIG. 23.—_Experiments at Baxter House._
]

“With a view of testing practically this theory, I constructed a
cylindrical vessel of 3 ft. in diameter and 5 ft. in height, somewhat
like an ordinary cupola furnace (see Fig. 23). The interior is lined
with firebricks, and at about 2 in. from the bottom of it I inserted
five _tuyère_ pipes, the nozzles of which are formed of well-burned
fire-clay, the orifice of each _tuyère_ being about three-eighths of an
inch in diameter; they are so put into the brick lining (from the outer
side) as to admit of their removal and renewal in a few minutes, when
they are worn out. At one side of the vessel, about half-way up from the
bottom, there is a hole made for running-in the crude metal, and on the
opposite side there is a tap-hole, stopped with loam, by means of which
the iron is run out at the end of the process. In practice this
converting vessel may be made of any convenient size, but I prefer that
it should not hold less than one nor more than five tons of fluid iron
at each charge; the vessel should be placed so near to the discharge
hole of the blast furnace as to allow the iron to flow along a gutter
into it. A small blast cylinder is required capable of compressing air
to about 8 lbs. or 10 lbs. to the square inch. A communication having
been made between it and the _tuyères_ before named, the converting
vessel will be in a condition to commence work; it will however on the
occasion of its first being used after re-lining with firebricks be
necessary to make a fire in the interior with a few baskets of coke, so
as to dry the brickwork and heat up the vessel for the first operation,
after which the fire is to be all carefully raked out at the
tapping-hole, which is again to be made good with loam: the vessel will
then be in readiness to commence work, and may be so continued without
any use of fuel until the brick lining, in the course of time, becomes
worn away, and a new lining is required. I have before mentioned that
the _tuyères_ are situated nearly close to the bottom of the vessel, the
fluid metal will therefore rise some 18 in. or 2 ft. above them; it is
therefore necessary, in order to prevent the metal from entering the
_tuyère_ holes, to turn on the blast before allowing the fluid crude
iron to run into the vessel from the blast furnace. This having been
done, and the metal run in, a rapid boiling up of the metal will be
heard going on within the vessel, the metal being tossed violently about
and dashed from side to side, shaking the vessel by the force with which
it moves; from the throat of the converting vessel flame will
immediately issue, accompanied by a few bright sparks such as are always
seen rising from the metal when running into the pig-beds. This state of
things will continue for about fifteen minutes, during which time the
oxygen in the atmospheric air combines with the carbon contained in the
iron, producing carbonic oxide, or carbonic acid gas, and at the same
time evolving a powerful heat. Now, as this heat is generated in the
interior of, and is diffused in innumerable fiery bubbles through, the
whole fluid mass, the metal absorbs the greater part of it, and its
temperature becomes immensely increased, and by the expiration of the
fifteen minutes before named that part of the carbon which appears
mechanically mixed and diffused throughout the crude iron has been
entirely consumed: the temperature however is so high that the
chemically combined carbon now begins to separate from the metal, as is
at once indicated by an immense increase in the volume of flame rushing
out of the throat of the vessel. The metal in the vessel now rises
several inches above its natural level, and a light frothy slag makes
its appearance and is thrown out in large foam-like masses. This violent
eruption of cinder generally lasts about five or six minutes, when all
further appearance of it ceases, a steady and powerful flame replacing
the shower of sparks and cinder which always accompanies the boil. The
rapid union of carbon and oxygen which thus takes place adds still
further to the temperature of the metal, while the diminished quantity
of carbon present allows a part of the oxygen to combine with the iron,
which undergoes combustion and is converted into an oxide. At the
excessive temperature that the metal has now acquired, the oxide as soon
as formed undergoes fusion, and forms a powerful solvent of those earthy
bases that are associated with the iron; the violent ebullition which is
going on mixes most intimately the scoria and metal, every part of which
is thus brought in contact with the fluid oxide, which will thus wash
and cleanse the metal most thoroughly from the silicon and other earthy
bases which are combined with the crude iron, while the sulphur and
other volatile matters which cling so tenaciously to iron at ordinary
temperatures are driven off, the sulphur combining with the oxygen and
forming sulphurous acid gas.

“The loss in weight of crude iron during its conversion into an ingot of
malleable iron was found, on a mean of four experiments, to be 12½ per
cent., to which will have to be added the loss of metal in the finishing
rolls. This will make the entire loss probably not less than 18 per
cent. instead of about 28 per cent., which is the loss on the present
system. A large portion of this metal is however recoverable by heating
with carbonaceous gases the rich oxides thrown out of the furnace during
the boil. These slags are found to contain innumerable small grains of
metallic iron, which are mechanically held in suspension in the slags
and may be easily recovered.

“I have before mentioned that after the boil has taken place a steady
and powerful flame succeeds, which continues without any change for
about ten or twelve minutes, when it rapidly falls off. As soon as this
diminution of flame is apparent the workman will know that the process
is completed, and that the crude iron has been converted into pure
malleable iron, which he will form into ingots of any suitable size and
shape by simply opening the tap-hole of the converting vessel and
allowing the fluid malleable iron to flow into the iron ingot moulds
placed there to receive it. The masses of iron thus formed will be free
from any admixture of cinder, oxide, or other extraneous matters, and
will be far more pure and in a forwarder state of manufacture than a
pile formed of ordinary puddle bars. And thus it will be seen that by a
single process, requiring no manipulation or particular skill, and with
only one workman, from three to five tons of crude iron pass into the
condition of several piles of malleable iron in from thirty to
thirty-five minutes, with the expenditure of about a third part the
blast now used in a finery furnace, with an equal charge of iron, and
with the consumption of no other fuel than is contained in the crude
iron.

“To those who are best acquainted with the nature of fluid iron, it may
be a matter of surprise that a blast of cold air forced into melted
crude iron is capable of raising its temperature to such a degree as to
retain it in a perfect state of fluidity after it has lost all its
carbon and is in the condition of malleable iron, which, in the highest
heat of our forges, only becomes softened into a pasty mass. But such is
the excessive temperature that I am enabled to arrive at with a properly
shaped converting vessel and a judicious distribution of the blast, that
I am enabled not only to retain the fluidity of the metal, but to create
so much surplus heat as to remelt all the crop-ends, ingot-runners, and
other scrap that is made throughout the process, and thus bring them,
without labour or fuel, into ingots of a quality equal to the rest of
the charge of new metal....

“To persons conversant with the manufacture of iron, it will be at once
apparent that the ingots of the malleable metal which I have described
will have no hard or steely parts, such as are found in puddled iron,
requiring a great amount of rolling to blend them with the general mass,
nor will such ingots require an excess of rolling to expel cinder from
the interior of the mass, since none can exist in the ingot, which is
pure and perfectly homogeneous throughout, and hence requires only as
much rolling as is necessary for the development of fibre; it therefore
follows that, instead of forming a merchant bar, or rail, by the union
of a number of separate pieces welded together, it will be far more
simple and less expensive to make several bars or rails from a single
ingot. Doubtless this would have been done long ago had not the whole
process been limited by the size of the ball which the puddler could
make.

“The facility which the new process affords of making large masses will
enable the manufacturer to produce bars that, in the old mode of
working, it was impossible to obtain; while at the same time it admits
of the use of more powerful machinery, whereby a great deal of labour
will be saved and the process be greatly expedited.... I wish to call
the attention of the meeting to some of the peculiarities which
distinguish cast steel from all other forms of iron, viz., the perfectly
homogeneous character of the metal, the entire absence of sand-cracks or
flaws, and its greater cohesive force and elasticity, as compared with
the blister steel from which it is made,—qualities which it derives
solely from its fusion and formation into ingots, all of which
properties malleable iron acquires in like manner by its fusion and
formation into ingots in the new process; nor must it be forgotten that
no amount of rolling will give the blister steel, although formed of
rolled bars, the same homogeneous character that cast steel acquires by
a mere extension of the ingot to some ten or twelve times its original
length....

“I beg to call your attention to an important fact connected with the
new process which affords peculiar facilities for the manufacture of
cast steel. At that stage of the process immediately following the boil
the whole of the crude iron has passed into the condition of cast steel
of ordinary quality. By the continuation of the process the steel so
produced gradually loses its small remaining portion of carbon, and
passes successively from hard to soft steel, and from soft steel to
steely iron, and eventually to very soft iron; hence, at a certain
period of the process, any quality of metal may be obtained. There is
one in particular which by way of distinction I call semi-steel, being
in hardness about midway between ordinary cast steel and soft malleable
iron. This metal possesses the advantage of much greater tensile
strength than soft iron; it is also more elastic, and does not readily
take a permanent set, while it is much harder and is not worn or
indented so easily as soft iron; at the same time it is not so brittle
or hard to work as ordinary cast steel. These qualities render it
eminently well adapted to purposes where lightness and strength are
specially required, or where there is much wear, as in the case of
railway bars, which from their softness and lamellar texture soon become
destroyed. The cost of semi-steel will be a fraction less than iron,
because the loss of metal that takes place by oxidation in the
converting vessel is about 2½ per cent. less than it is with iron; but
as it is a little more difficult to roll, its cost per ton may fairly be
considered to be the same as iron; but as its tensile strength is some
30 or 40 per cent. greater than bar iron, it follows that for most
purposes a much less weight of metal may be used than that so taken. The
semi-steel will form a much cheaper metal than any we are at present
acquainted with. These facts have not been elicited from mere laboratory
experiments, but have been the result of working on a scale nearly twice
as great as is pursued in our largest iron works, the experimental
apparatus doing 7 cwt. in thirty minutes, while the ordinary puddling
furnace makes only 4½ cwt. in two hours, which is made into six separate
balls, while the ingots or blooms are smooth, even prisms, 10 in. square
by 30 in. in length, weighing about equal to ten ordinary puddle balls.”

The startling novelty of the methods and results described in this paper
had the effect of paralyzing discussion at the time. But soon the voice
of detraction was heard; many iron-masters ridiculed the idea of
producing iron and steel without fuel, and indeed it may have been
observed, the title of the paper notwithstanding, that first the silicon
and carbon, and then the iron itself, really supplied the fuel. And we
must remember that malleable iron in a molten state was then deemed an
impossibility, for the hottest furnaces then known could not effect the
fusion, however prolonged their action might be, yet Bessemer was to
obtain five tons in this condition in the short space of half an hour
with no other aid than cold air. Then it was said that Bessemer’s
process of forcing air into melted cast iron had no claim of novelty,
for it had been tried before and found valueless. Some iron-masters on
trying experiments on a small scale and with imperfect appliances met
with failures, and discredited the process at once; but five large
establishments paid for licences sums amounting to £26,500 within three
weeks of the reading of the paper. At the works of the Dowlais Iron Co.,
in South Wales, who were the first licensees, the first converter was
set up under Bessemer’s personal superintendence, and at the first
operation five tons of iron were produced direct from the blast furnace
pig. This apparently satisfactory result proved quite otherwise when
this iron came to be practically tested; for it was found quite useless!
It was both “_cold-short_” and “red-short,” to use the technical
terms,—the former of which means that although the sample may be welded,
it is when cold brittle and rotten; the latter means that at a low red
heat it breaks and crumbles under the hammer. Further trials were made,
new experiments instituted, but the success that attended Bessemer’s
early experiments could not be repeated, and as yet no one knew the
reason why. Now it so happened that in the preliminary experiments an
exceptionally pure pig iron had been made use of containing little or no
phosphorus or sulphur, substances very deleterious in iron, and still
more so in steel. With the capital obtained by the sale of his licences
Bessemer quietly set to work to investigate the cause of his
non-success, making daily experiments with a ton or two of metal at a
time. These experiments extended over a period of two and a half years,
and upon them Bessemer and his partner spent about £16,000, besides the
£4,000 the preliminary researches had cost. But all difficulties were at
length overcome, and the process was now found capable of turning out
pure iron and steel when the pure pig iron of Sweden was used in the
converter. In the meantime the licensees had made no attempts
practically to carry out the process, which began to be denounced as
visionary: it was “a mare’s nest”; it was “a meteor that had passed
through the metallurgical world, but had gone out with all its sparks.”
When Bessemer again brought the subject before the public, he found that
no one believed in it; everyone said, “Oh, this is the thing that made
such a blaze two or three years ago, and which was a failure.” Neither
iron-makers nor steel-makers would now take it up. Bessemer and his
partner thereupon joined with three other gentlemen to establish at
Sheffield a steel-works of their own, where the invention should be
carried into full practice. In due time works were erected, and they
commenced to sell steel, receiving at first very paltry orders, for such
quantities as 28 lbs. or 56 lbs.; but the orders soon became larger, and
afterwards very much larger, for they were underselling the Sheffield
manufacturers by £20 a ton, and their steel was undistinguishable from
the higher priced article. Bessemer had now bought his licences back
again, and in the course of his second set of experiments had patented
each improvement as it occurred to him, finally bringing the mechanical
apparatus to the degree of efficiency requisite for practical working,
without which his primary idea would have been valueless. Before
directing the reader’s attention to the form the apparatus had assumed,
we may transcribe what Mr. Jeans, in the work above referred to, has
told about the commercial success of the Bessemer steel-making firm:—

“On the expiration of the fourteen years’ term of partnership of this
firm the works, which had been greatly increased from time to time out
of revenues, were sold by private contract for exactly twenty-four times
the amount of the whole subscribed capital, notwithstanding that the
firm had divided in profits during the partnership a sum equal to
fifty-seven times the gross capital, so that by the mere commercial
working of the process, apart from the patent, each of the five partners
retired after fourteen years from the Sheffield works with eighty-one
times the amount of his subscribed capital, or an average of nearly
cent. per cent., every two months,—a result probably unprecedented in
the annals of commerce.”

[Illustration:

  FIG. 24.—_Bessemer Converter._

  A, Front view, showing the mouth, _c_; B, Section.
]

The form of the Bessemer apparatus as it finally left the inventor’s
hands may now be considered: but in certain details and arrangements
some modifications, dictated by the experience and requirements of
individual establishments, have been made, leaving the principles of the
apparatus unchanged. Thus instead of making the converting vessel turn
on trunnions, it is sometimes constructed fixed, the fluid metal after
conversion being let out at a tap-hole; the number and size of the
_tuyères_ are varied; and so with the disposition of the air chamber or
_tuyère_ box, the pressure of the blast, the capacity of the converter
itself, etc. In capacity converters vary between 2½ tons and 10 tons;
one of medium size is shown in elevation and section in Fig. 24, and may
be described as an egg-shaped vessel about 15 ft. high and 6 ft.
diameter inside. It is strongly made of wrought iron in two parts bolted
together, and is lined inside with some thick infusible coating, of
which more is to be said presently. The converter swings on trunnions,
one of which is hollow, and admits the blast by the pipe _b_ to the base
of the vessel, whence it passes through the passages shown at _e_. The
thickness of the lining at _e_ may perhaps be 20 in., and passages for
the air are perforated in fire-clay _tuyères_, of which there may be
seven, each with seven perforations of half an inch diameter. To the
other trunnion is attached a toothed wheel which engages the teeth of a
rack receiving motion from hydraulic pressure. The iron for the
operation is melted in a furnace having its hearth above the level of
the converter; and to receive its charge the latter is turned so that
the molten cast iron may be poured in from a trough until its surface is
nearly on a level with the lowest of the _tuyères_. The blast having
been turned on, the hydraulic power is set to work and the converter is
slowly brought to an upright position. The pressure of the current of
air prevents any of the fluid metal from entering the blow-holes. The
blast of cold air is continued until all the silicon and carbon have
been removed by oxidation. If the production is to be steel, there is
then added to the contents of the converter, placed in position to
receive it, a certain weight of melted cast iron of a special
constitution, and the blow is resumed for a few minutes; or in more
recent practice this special metal is added to the fluid metal run out
of the converter into a spacious ladle in known quantity. On this
addition an intense action takes place, attended by an extremely
brilliant flame and a throwing out of cinder or slag. The metal thus
added to the decarbonized iron is a carbonized alloy of iron and
manganese obtained from an ore naturally containing the latter metal,
and scarcely any phosphorus or sulphur. The charcoal pig from this ore
is called _spiegeleisen_ (German = mirror-iron) from its brilliant
reflecting facets; it contains from 12 to 20 per cent. of manganese,
with about 5 per cent. of carbon, and a considerable proportion of
silicon. An exact chemical analysis of the particular spiegeleisen
having been previously made, it is known what proportion of it is to be
added to the decarbonized iron in order to convert this into a steel
with any required content of carbon. The manganese probably acts by
combining with oxide of iron diffused through the mass, and together
with the silicon forming the very easily separated slag which is
ejected.

The whole series of operations connected with the Bessemer process may
be easily followed by the help of Fig. 25, which is taken from a
beautiful model in the Museum of Practical Geology. This model, which
was presented to the museum by Mr. Bessemer himself, represents every
part of the machinery and appliances of the true relative sizes. C is
the trough, lined with infusible clay, by which the liquid pig iron is
conveyed to the converters, A. The hydraulic apparatus by which the
vessels are turned over is here below the pavement, but the rack which
turns the pinion on the axis of the converter is shown at B. The vessel
into which the molten steel is poured from the converter is marked E,
and this vessel is swung round on a crane, D, so as to bring it exactly
over the moulds, placed in a circle ready to receive the liquid steel,
which on cooling is turned out in the form of solid ingots. The valves
which control the blast, and those which regulate the movements of the
converter through the hydraulic apparatus, are worked by the handle seen
at H. The crane, or revolving table, D, is also under perfect control,
so that the crude pig iron is converted into steel, and the moulds are
filled with a rapidity and ease that are positively marvellous to a
spectator.

[Illustration:

  FIG. 25.—_Model of Bessemer Steel Apparatus._
]

The development of the Bessemer process soon had the effect of so
reducing the price of steel that this material came into use for almost
every purpose for which iron had previously been employed, such as
railway bars, girders, etc., for bridges, boiler plates, etc., for all
which “steely iron” containing only 0·12 to 0·40 per cent. carbon proved
admirably adapted. The practical success of the Bessemer process had not
long been demonstrated commercially by the inventor and his partners at
Sheffield before other firms began the manufacture: so that in 1878
there were in Great Britain alone twenty-seven establishments making
Bessemer steel and using 111 converters. It may give an idea of the
magnitude the Bessemer steel manufacture had attained even at that time
if we quote the cost of erecting a complete plant for two 5–ton
converters: it was £44,400, as given in a detailed estimate. In all
these cases pig iron from ores free from phosphorus and sulphur had to
be used, for as we have seen the converter failed to eliminate these
vitiating elements. Imported pig ores had in general to be used, or pig
from the limited supply of British hæmatite ores in West Cumberland. The
Barrow Hæmatite Steel Company engaged in the production of Bessemer
steel on a very large scale, having by 1878 erected no fewer than
sixteen converters of the capacity of 6 tons each. In the meanwhile many
efforts were made to discover some method of eliminating phosphorus, so
that the ordinary qualities of British pig iron, and iron derived in any
part of the world from the coarse phosphorized ores, might be available
for the converter. Many of the methods then devised proved correct in
principle and feasible in practice; but as, for sundry reasons, none of
them came extensively into use, we need not here allude to them further.

The solution of the problem was announced in 1879. Some years before, G.
J. Snelus had come to the conclusion that with a siliceous lining it
would be impossible to eliminate phosphorus in the Bessemer converter,
and that some refractory substance of a basic character must be sought
for in order that the slag produced should be in a condition to absorb
the phosphoric acid as fast as it is produced. He patented in 1872 the
use of magnesian limestone as a material for the lining; as that
substance when intensely heated became very hard and stony, being in
that condition quite unaffected by water. Two young chemists, Messrs.
Thomas and Gilchrist, apparently without being aware of Mr. Snelus’s
conclusions, had also convinced themselves that the chief deficiency in
the Bessemer process was due to the excess of silica in the slag, and in
1874 they began to try the effect of basic linings, and also of basic
additions, such as lime, etc., to the charge in the converter, so that
the lining itself should not be worn out by entering into the slag.
Their results proved that phosphorus could be eliminated when the slag
contained excess of a strong base. An example of an operation at
Bolckow, Vaughan, & Company’s Eston works with the highly phosphorized
Cleveland pig iron may be quoted. The basic-lined converter received
first 9 cwt. of lime, then 6 tons of metal. When the blast at 25 lbs.
pressure was turned on, the silicon began at once to burn; for three
minutes the carbon was not affected, but for fourteen minutes longer it
regularly diminished, the silicon keeping pace with it. After the blow
had been continued for thirteen minutes from the commencement, the
converter was turned down to allow of the further introduction of 19½
cwt. of a mixture of two parts of lime with one of oxide of iron. So
long as 1·5 per cent. of carbon remained in the metal the phosphorus was
untouched, and at the end of the blow, _i.e._ when the flame dropped,
only one-third of it had been eliminated; it still formed 1 per cent. of
the metal. The blast continued for another two minutes brought it down
to ¼ per cent., and in one more minute only a trace was left. Most of
the sulphur was got rid of at the same time. From Cleveland pig, thus
de-phosphorized in the Bessemer converter, large quantities of steel
rails were rolled for the North Eastern Railway Company, and were found
entirely satisfactory, being as good as those made from the Cumberland
hæmatite steel. This de-phosphorized process has been brought into
operation wherever phosphoric ores are dealt with, and it has been
applied with equal success in the “open hearth” furnaces, of which we
have now to speak.

All discoveries and all inventions may be traced back to preceding
discoveries and inventions in an endless series, and it is only by its
precursors that each in its turn has been made possible. If we take one
of the greatest marvels brought into existence at nearly the close of
our epoch, namely, “wireless telegraphy,” we may follow up links of a
chain connecting it with the recorded observations of an ancient Greek
(Thales) who flourished seven centuries before our era, and even these
may not have been original discoveries of his. And it will have been
gathered from what has already been said that steel must have been
produced, however unwittingly, at the earliest period at which man began
to reduce iron from its ores. So the very latest, and for many purposes
the most extensively practised, process of modern steel-making, brought
indeed to working perfection mainly by the perseverance and scientific
insight of two individuals, is the result of the observation and the
accumulated experience of former generations. The observations and
experience here alluded to are chiefly those that follow two lines: one
concerning the properties of the metal itself, the other relating to the
means of commanding very high temperatures on a great scale. On this
occasion we are able almost to lay a finger on some proximate links of
the chain. Réaumur, the French naturalist, made steel in the early part
of the eighteenth century by melting cast iron in a crucible, and in
this liquid metal he dissolved wrought iron, the product being, as the
reader will now easily understand, the intermediate substance, steel;
and this was obtained of course at a temperature which was incapable of
fusing wrought iron by itself. He published in 1722 a treatise on “The
Art of converting Iron into Steel, and of softening Cast Iron.” For
this, and certain other metallurgical discoveries, Réaumur received a
life-pension equivalent to about £500 per annum,—a treatment very
different from that dealt out by the British to Henry Cort. The action
in Réaumur’s crucible is precisely that used on the large scale in
Siemens’ open hearth. But this last became possible only when Siemens
had worked out his “regenerative stove” or heat accumulator, the
development of an idea suggested by a Dundee clergyman in 1817.

A general notion of the Siemens’ regenerative stove will have been
already gained from the account given before of its application to the
modern type of blast furnace. Of the inventor himself, C. William
Siemens, it may be observed that he was one of a family of brothers, all
remarkable for their scientific attainments, and in many of his
researches and processes he was aided by his brothers Frederick and
Otto. In our article on “Electric Power and Lighting” there will be
found some notice of a few of Siemens’ inventions pertaining to those
subjects. A still more admirable invention of his is the electric
pyrometer, an instrument of the utmost utility for measuring, with an
accuracy previously unapproachable, the high temperature of furnaces,
etc. Indeed there are few departments of science, pure or applied, which
have not been enriched by the researches and contrivances of this
distinguished man, whose merits were acknowledged by the bestowal upon
him of the highest scientific and academical honours, and also of a
title, for he became Sir William Siemens.

[Illustration:

  FIG. 26.—_Section of Regenerative Stoves and Open Hearth._
]

Siemens was much engaged from 1846 in conjunction with his brother
Frederick in experimental attempts, continued over a period of ten
years, at the construction of the regenerative gas furnace. At length,
in 1861, he proposed the application of his furnace to an “open hearth,”
and during the next few years some partial attempts to carry out his
process were made, and he himself had established experimental works at
Birmingham in order to mature his processes, while Messrs. Martin of
Sireuil, in France, having obtained licences under Siemens’ patents,
gave their attention to a modification of his process, by which they
succeeded in producing excellent steel. Siemens having in 1868 proved
the practicability of his plans by converting at his Birmingham works
some old phosphorized iron rails into serviceable steel, a company was
formed, and in 1869 the Landore Siemens’ Steel Works were established at
Landore in Glamorganshire, and a few years after, these had sixteen
Siemens open hearth melting furnaces at work, giving a total output of
1,200 tons of steel per week. The number of furnaces was subsequently
increased. Extensive works specially designed for carrying out the
Siemens and the Siemens-Martin process were shortly afterwards erected
at other places, as at Newtown, near Glasgow, Panteg in Wales, etc. In
Great Britain the open hearth process gradually gained upon the
Bessemer, until in 1893, when the total output of both kinds amounted to
nearly 3,000,000 tons, this was almost equally divided between them, and
since that period the steel made by the former has greatly surpassed in
amount that made by the latter.

How the regenerative stove, or heat accumulator, works, and how it is
applied in the open hearth process, the reader may learn by aid of the
diagram Fig. 26, in which however no representation of the disposition
of the parts in any actual furnace is given, nor any details of
construction beyond what is necessary to make the principle clear. On
the right and on the left of the diagram will be seen a pair of similar
chambers which are shown as partly below the level of the ground S S´,
such being a usual disposition. The outer walls of these chambers are
thick and the interior is entirely lined with the most refractory
fire-bricks, of which also is formed the partition in between each pair
of compartments, as well as the passages from the top of each opening on
the furnace H. Each chamber or compartment is filled with rows of
fire-bricks, laid chequerwise so as to leave a multitude of channels
between. At the bottom of the chamber on the left let us suppose
atmospheric air to be admitted by the channels A, A, A, and a
combustible gas which we may take to be a mixture of carbonic oxide with
some hydrogen is admitted in the same way to the second compartment on
the left through the passages G, G, G. Supposing the apparatus quite
cold in the first instance, the gas would ascend into the furnace H as
shown by the arrows, because it might be drawn by an up-draught in a
chimney connected with the six chambers shown at the bottom of the
right, and it would also tend to rise up into the space H by its lighter
specific gravity, and there it could be set on fire, when a volume of
flame would pass across to the right, a plentiful supply of air rushing
in through the air chamber from A, A, A, and the products of the
combustion, mainly hot carbonic acid gas and hot nitrogen gas, in
passing through the right-hand chambers, would make the bricks in both
compartments very hot after a time, for the current would divide itself
between the two passages, as indicated by the divided arrow. We have not
shown the valves by which the workman is able, by merely pulling a
lever, to shut off the air supply from A, A, A, and of gas from G, G, G,
and put these channels into direct communication with the up-draught
chimney, at the same time supplying gas at G´, G´, G´, and air at A´,
A´, A´. These rise up among the now heated bricks each in its own
compartment, but mix where they enter the furnace H, now hot enough to
set them on fire, and the gaseous products of combustion, hotter now
than before, descend among the fire-bricks of the left-hand
compartments, heating them in turn. After another period, say half an
hour, the valves are again reversed, and again gas and air both heated
burn in the space H, and their products supply still more heat to the
right-hand compartments. And so the action may be continued with a great
temperature each time produced by the combustion of the combining bodies
at increasingly higher temperatures. Thus, if cold gas and air by
combination give rise to 500° of heat, when the same combine, at say the
initial temperature of 400°, the result would be a temperature of 900°;
if burnt at this latter degree, then 900° + 500° would be reached, and
so on. It would seem as if there were no limit to the temperatures
obtainable in this way. But the nature of the materials of which the
furnace is constructed imposes a limit, for even the most refractory
matters yield at length, and the working would come to an end by the
fusing of the brickwork. The diagram is a section through the length of
the hearth (for it is usually oblong in plan), and the low arch above H
being exposed to the fiercest heat, is formed of the most refractory
“silica bricks,” that is, bricks made of coarsely ground silica held
together with a little lime; yet this extremely resisting material is
acted upon, and the arch has to be renewed every few months or sometimes
weeks. The hearth itself is supported by massive iron plates, shown in
the diagram by the thick lines, above which is laid a deep bed L, of
quartz sand or ganister, or where required a _basic_ lining, beaten hard
down, and forming a kind of basin with sides sloping down in all
directions to a point immediately below the centre of the fire-brick
door D, where is the aperture for tapping, stopped by a mixture of sand
and clay until the metal is ready for drawing off, when it runs outside
into an iron spout lined with sand and is received into the ingot
moulds. B in the figure represents the “bath,” as it is called, of
molten metal, which, in the larger furnaces, where 20 tons of metal is
operated on at once, may occupy an area of 150 square ft.

It need hardly be mentioned that there has to be a certain adjustment
between the volumes of air and of gas that pass into the regenerative
stoves, in order that the best effect may be obtained. Besides the limit
of temperature occasioned by the nature of the materials, there is a
chemical reason why the regenerative stoves cannot increase the
temperature indefinitely. It is noticed that when the temperature of the
furnace has become very high indeed, the flame over the hearth assumes a
peculiar appearance, being interrupted by dark spaces. These are
attributable to what is called in chemistry “dissociation,”—in this case
the dissociation of carbonic acid gas, which by the heat alone separates
into carbonic oxide and oxygen gases. In the same way these gases refuse
to combine if brought together heated beyond a certain temperature. This
phenomenon of dissociation is a general one, for it is found that for
any pair of substances there is a characteristic range of temperature
above or below which they refuse to combine. The gas used in these
stoves is either unpurified coal gas, or that produced by passing steam
over red-hot coal or coke.

We have spoken of the Siemens and the Siemens-Martin open hearth
processes. In the latter a charge of pig iron, say 1½ tons, is first
melted on the hearth, then about 2 tons of wrought iron is added in
successive portions, and in like manner nearly as much scrap steel
(_i.e._ turnings, etc.), the final addition being half a ton of
spiegeleisen containing 12 per cent. of manganese. A furnace of
corresponding dimensions will allow of three charges every twenty-four
hours. In the Siemens process it is not wrought iron or steel scrap that
is mainly used to decarbonize the pig, but a pure oxide ore. This is
thrown into the bath of molten metal in quantities of a few cwts. at a
time, when a violent ebullition occurs. When samples of the metal and of
the slag are found to be satisfactory, spiegeleisen or ferro-manganese
is added, and the charge is cast. This process takes a rather longer
time than the former, but gives steel of more uniform character. In both
processes, phosphorus is oxidized at the high temperature attained and
passes into the slag, which last floats of course on the molten metal
and is from time to time tapped off as the action proceeds.

[Illustration:

  FIG. 26_a_.—_Rolling Mill._
]

Fig. 26_a_ shows a rolling mill with what is called a “two-high” train
for finishing bars by passing them between the grooves cut in the rolls
to give the required section. The rolls in the illustration turn in one
direction only, and therefore the bars after emerging from the larger
grooves have to be drawn back over the machine and set into a smaller
pair from the same side. This inconvenience is avoided in the
“three-high train,” on which three rolls revolve, and the bars can be
passed through them from one side to the other alternately. The celerity
with which a glowing steel ingot is without re-heating converted into a
straight steel rail 60 or 100 feet long, by passing a few times
backwards and forwards between the rolls, is very striking. These rolls
are made of solid steel, and in some cases have a diameter of 26 inches
or more.


                        _IRON IN ARCHITECTURE._

Everyone knows how much iron is used in those great engineering
structures that mark the present age, and of which a few examples will
be described in succeeding articles. One other feature of the nineteenth
century is the use of iron in architecture. Some have, indeed, protested
against the use of iron for this purpose, and would even deny the name
of architecture to any structure obviously or chiefly formed of that
material. Stone and wood, they say, are the only proper materials,
because each part must be wrought by hand, and cannot be cast or
moulded; and further, iron being liable to rust, suggests decay and want
of permanence, and these are characters incompatible with noble
building. All this can rest only on a relative degree of truth—as, for
instance, machinery is used to dress and shape both wood and stone, and
the permanence of even the latter is as much dependent on conditions as
that of iron. Iron used in architecture is hideous when applied in
shapes appropriate only to stone; but when it is disposed in the way
suggested by its own properties, and receives ornament suitable to its
own nature, the result is harmonious and graceful, and the structure may
display beauties that could be attained by no other materials. Be that
as it may, the great and lofty covered spaces that are required for our
railway stations and for other purposes could have been obtained only by
the free use of iron, and everyone can recall to mind instances of such
structure not devoid of elegance, in spite of the absence—the proper
absence—of the Classic “orders” or Gothic “styles.” The first notable
instance of the application of iron on a large scale was the erection of
the “Crystal Palace,” in Hyde Park, for the great Exhibition of 1851. It
was taken down and re-erected at Sydenham, and there it has become so
well known to everyone that any description of it is quite unnecessary
in this place.

As another conspicuous example of what may be done with iron, the Eiffel
Tower at Paris may be briefly described.

The idea of erecting a tower 1,000 feet high was not of itself new. It
had been entertained in England as early as 1833, in America in 1874,
and in Paris itself in 1881. It has been reserved for M. Gustave Eiffel,
a native of Dijon, who commenced to practise as an engineer in 1855, to
realize this ambitious project. He has long been occupied in the
construction of great railway bridges and viaducts, and in these he has
adopted a system peculiar to himself of braced wrought-iron piers
without masonry or cast-iron columns. He also was the first French
engineer to erect bridges of great span without scaffolding. In the
Garabit viaduct he planned an arch of 541 feet, crossing the Truyère at
a height of nearly 400 feet above it. One result of M. Eiffel’s studies
in connection with these lofty piers was his proposal to erect the tower
for the Paris Exhibition of 1889. This proposal met with great
opposition on the part of many influential people in Paris—authors,
painters, architects, and others protesting with great energy against
the modern Tower of Babel, which was, as they said, to disfigure and
profane the noble stone buildings of Paris by the monstrosities of a
machine maker, etc. etc. The Eiffel Tower is now constructed, and no one
has heard that it has dishonoured the monuments of Paris, for it has
been instead a triumph of French skill, the glory of its designer, and
the wonder of the Exhibition.

[Illustration:

  FIG. 26_b_.—_The Eiffel Tower in course of construction._
]

The tower rests on four independent foundations, each at the angle of a
square of about 330 feet in the side, and it may be noted that the two
foundations near the Seine had to be differently treated from the other
two, where a bed of gravel 18 feet thick was found at 23 feet below the
surface, and where a bed of concrete, 7 feet thick, gave a good
foundation. The foundations next the river had to be sunk 50 feet below
the surface to obtain perfectly good foundations. Underlying the whole
is a deep stratum of clay; but this is separated from the foundations by
a layer of gravel of sufficient thickness. Above this are beds of
concrete, covering an area of 60 square metres, and on the concrete
rests a pile of masonry. Each of the four piles is bound together by two
great iron bars, 25 feet long and 4 inches diameter, uniting the masonry
by means of iron cramps, and anchoring the support of the structure,
although its stability is already secured by its mere weight. The tower
is of curved pyramidal form, so designed that it shall be capable of
resisting wind pressure, without requiring the four corner structures to
be connected by diagonal bracing. The four curved supports are, in fact,
connected with each other only by girders at the platforms on the
several stages, until at a considerable length they are sufficiently
near to each other to admit the use of the ordinary diagonals. The work
was begun at the end of January, 1887, and M. Eiffel notes how the
imagination of the workmen was impressed by the notion of the vast
height of the intended structure. Not steel, but iron is the material
used throughout, and the weight of it is about 7,300 tons, without
reckoning what is used in the foundations, and in the machinery
connected with the lifts, etc. It has long ago been found that stone
would be an unsuitable material for a structure of this kind, and it is
obvious that only iron could possibly have been used to build a tower of
so vast a height and within so short a space of time, for it was
completed in April, 1889. A comparison of heights with the loftiest
stone edifices may not be without interest. The highest building in
Paris is the dome of the Invalides, 344 feet; Strasburg Cathedral rises
to 466 feet; the Great Pyramid to 479 feet; the apex of the spire in the
recently completed Cathedral at Cologne to 522 feet. These are
overtopped by the lofty stone obelisk the Americans have erected at
Washington, which attains a height of more than 550 feet. Such spires
and towers have been erected only at the cost of immense labour. But
iron, which can be so readily joined by riveting, lends itself
invitingly to the skill of the constructor, more particularly by reason
of the wonderful tensile strength it possesses. It is scarcely possible
to convey any adequate idea of the great complicated network of bracings
by which in the Eiffel Tower each standard of the columns is united to
the rest to form one rigid pile. The horizontal girders unite the four
piers in forming the supports of the first storey some 170 feet above
the base. The arches which spring from the ground and rise nearly to the
level of these girders are not so much intended to add to the strength
of the structure as to increase its architectural effect. The first
storey stands about 180 feet above the ground, and is provided with
arcades, from which fine views of Paris may be obtained. Here there are
spacious restaurants of four different nationalities. And in the centre
of the second storey (380 feet high) is a station where passengers
change from the inclined lifts to enter other elevators that ascend
vertically to the higher stages of the tower. On the third storey, 900
feet above the ground, there is a saloon more than 50 feet square,
completely shut in by glass, whence a vast panorama may be contemplated.
Above this again are laboratories and scientific observatories, and,
crowning all, is the lighthouse, provided with a system of optical
apparatus for projecting the rays from a powerful electric light. This
light has been seen from the Cathedral at Orléans, a distance of about
70 miles.

[Illustration:

  FIG. 26_c_.—_The Eiffel Tower._
]

The buildings of the Paris Exhibition of 1889 are themselves splendid
examples, not only of engineering skill, but of good taste and elegant
design in iron structures and their decorations. The vast _Salle des
Machines_ (machinery hall) exceeds in dimensions anything of the kind in
existence, for it is nearly a quarter of a mile long, and its roof
covers at one span its width of 380 feet, rising to a height of 150 feet
in the centre. This great hall is to remain permanently, as well as the
other principal galleries with their graceful domes.

The Eiffel Tower having proved one of the most striking features of the
great Paris Exhibition, and of itself a novelty sufficient to attract
visitors to the spot, and having, long before the Exhibition closed,
completely defrayed the expense of its construction, with a handsome
profit besides, its success has naturally provoked similar
enterprises,—as, for instance, at Blackpool, a seaside resort in
Lancashire, there has been erected an openwork metal tower, resembling
the Paris structure, but of far less altitude.


                  _Tall Buildings in American Cities._

In several of the great cities of the United States, the last few years
have witnessed a novel and characteristic development of the use of iron
in architecture. In many structures on the older continent, this
material has been frankly and effectively employed, forming the obvious
framework of the erection, even when the leading motive was quite other
than a display of engineering skill. The Crystal Palace at Sydenham and
other erections have been referred to, in which iron has taken its place
as the main component of structures designed more or less to fulfil
æsthetic requirements: the guiding principle in “tall office buildings”
in the cities of the Western continent is, on the contrary, avowedly
utilitarian. Iron has, of course, long been used in the form of pillars,
beams, etc., in ordinary buildings, and it is only the extraordinary
extension of this employment of it, after the lift or elevator had been
perfected, and the ground-space in great commercial centres was daily
becoming more valuable, that has led to the erection of structures of
the “sky-scraper” class in American cities. For a given plot at a stated
rent, a building of many stories, let throughout as offices, will
obviously bring to its owner a greater return than one of few stories.
The elevators now make a tenth story practically as accessible as a
third storey, and the tall building readily fills with tenants. No claim
for artistic beauty has been advanced for these structures, which aim
simply at being places of business, and if provision be made for
sufficient floor-space and daylight, and for artificial lighting,
heating, and ventilation, together with the ordinary conveniences of
modern life, and ready elevator service, nothing more is required by the
utilitarian spirit, that seeks only facilities for money-getting. These
tall buildings are usually erected on plots disproportionately small,
and the architectural effect is apt to be bizarre and incongruous,
especially when the structure shoots up skyward in some comparatively
narrow street amid more modest surroundings. They are really engineering
structures, but invested with features belonging to edifices of quite
another order of construction. If they are necessities of the place and
period, and are “come to stay,” it cannot be doubted but that decoration
of an appropriate and harmonious character will, in course of time, be
evolved along with them, when the conventionality that clings to
architecture shall be broken through, and a new style appear, as
consistent, and therefore as beautiful, in relation to the “tall office
building,” as were those of the Greek temple and the Gothic minster in
their free and natural adaptation.

[Illustration:

  PLATE IV.

  THE AMERICAN TRACT SOCIETY BUILDING.
]

[Illustration:

  FIG. 26_d_.—_St. Paul Building, N. Y._
]

Here, apparently, is the opportunity for the advent of a new and
characteristic style. There is great ingenuity displayed in the
arrangement and internal finish of these buildings. But besides the
somewhat novel application of iron, the most notable circumstances
regarding them are the tendency to make them of greater and greater
height, and the wonderfully short time in which, upon occasion, they can
be run up. Chicago has recently been noted for its tall edifices, among
which may be named _The Reliance Building_, erected upon a site only 55
feet in breadth, but rising in fourteen stories to the height of 200
feet, and presenting the appearance of a tower. There are no cast iron
pillars, but the whole metal framework is of rolled steel, the columns
consisting of eight angle-sections, bolted together in two-story
lengths, adjoining columns breaking joint at each floor, and braced
together with plate girders, 24 inches deep, bolted to the face of the
columns, with which they form a rigid connection. Externally, the
edifice shows nothing but white enamelled terra-cotta and plate glass.
This building was originally a strongly-built structure of five stories,
the lower one being occupied as a bank. The foundations and the first
story were taken out, and prepared for the lofty edifice, the
superstructure being the while supported on screws. Then the three upper
stories were taken down, and the building was continued from the second
story, which was filled with tenants while the building was in course of
erection above.

[Illustration:

  FIG. 26_e_.—_Manhattan Insurance Co.’s Building, in course of
    erection._
]

Still more lofty edifices have been going skyward in other places.
Already in New York there are a great number of lofty piles due to the
introduction of the lifts or elevators, by which an office on the tenth
floor is made as convenient as one on the second. These buildings
usually receive the name of the owners of the structure, who occupy,
perhaps, only one floor. To mention only a few. There is the American
Tract Society building, with its twenty-three stories, 285 feet high,
which is one of the latest and handsomest of these tall piles in the
city. See Plate IV. Still loftier is the St. Paul building, fronting the
New York Post-Office at the junction of Park Row and Broadway. This
structure is splayed at the angle between Ann Street and Broadway, where
its width is 39½ feet, while its _loftiest_ part has frontages of about
30 feet along each of these thoroughfares. The height is no less than
313 feet above the pavement, and the number of stories is twenty-five.
This building is faced with light yellow limestone, and although it was
commenced only in the summer of 1895, it was expected to be ready for
occupation by the autumn of 1896. Even this great height is overtopped
by the Manhattan Life Insurance Company’s building, rising 330 feet, and
remarkable as perhaps beyond previous record of quickness in building a
gigantic structure. Obviously, the foundations of such a building must
be most seriously considered, prepared and tested, before the great bulk
of the building is begun, and in the _New York Engineering Magazine_ one
of the architects has given a full account, with complete illustrations,
of all the works, from the rock foundation to the completed edifice. A
description of the foundation work, though most interesting for the
professional engineer, would probably have little attraction for the
general reader; but its importance may be inferred from the fact of its
having taken nearly six months for its completion, while the huge
superstructure required only eight months. The eighteenth tier of beams
was reached in “three months from the time the foundations were ready on
which to set the first piece of steel, composing the bolsters that
support the cantilever system.... The substructure, which starts in
bed-rock and continues to the cellar-floor, consists of fifteen piers,
varying in size from 9 feet in diameter, to 21 feet 6 inches by 25 feet
square.... The number of bricks used in the piers amounted to 1,500,000.
From this it may be seen that a good-sized building was sunk out of
sight before any part of the superstructure could be begun.” An open
court within the main structure, special framing for the arrangements of
the company’s offices on the sixth floor, the great height and weight of
the tower, and the requisite provision for wind-bracing, delayed in some
degree a regular advance of the stories; but within three months no less
than 5,800 tons were placed in position. There were girders weighing 40
tons, many columns of 10 and 12 tons, and cantilevers of 80 tons weight
and 67 feet long. Strange to say, that in a building of this magnitude,
where such masses had to be raised 300 feet into the air, there was not
a single accident involving loss of life. When four stories of the steel
framework had been put up, the bricklayers were set to work, and they
followed the frame-setters throughout. After the masons came the
pipe-layers, with their ten miles of pipes, followed by electricians,
fixing their thirty-five miles of communicating wires. Thirty thousand
cubic feet of stone was cut and set on the Broadway front in eighty
days. Then craftsmen of the different trades followed each other, or
worked in harmony together, story after story upwards: the engineers for
boilers, heating, and elevators, the plumbers, the decorators, the
carpenters and cabinet-makers, the plasterers, the marble and tile
workers, the gasmen, etc. In fine, every story was completely finished
and ready for occupation in eight months after the start from the
foundations.

[Illustration:

  FIG. 26_f_.—_Manhattan Insurance Co.’s Buildings nearly completed._
]

The shortness of the time in which these lofty buildings were run up is
not less remarkable than the completeness of their fittings, which
comprise everything requisite for communication within the premises and
in connection with the outer world. The elevators or lifts are the
perfection of mechanism in their way, and act with wonderful smoothness
and regularity; of these are usually two at least, as well as an ample
staircase. Notwithstanding all these appliances, some disastrous and
fatal conflagrations have occurred at buildings erected on the “tall”
principle; and as “business premises” of even 380 feet high are
projected, the authorities have been considering the desirability of
restricting the heights. It has been proposed that offices should not
exceed in height 200 feet; hotels, 150 feet; and private houses, 75
feet.


                             _BIG WHEELS._

The Paris example of an engineering feat upon an unprecedented scale
having proved sufficiently captivating for the general public to ensure
for itself a great commercial success, even amid the attractions of an
International Exhibition, was not lost upon the enterprising people of
the States when the “World’s Fair” at Chicago was in preparation in
1893. It was then that Mr. G. W. G. Ferris, the head of a firm of bridge
constructors at Pittsburg, conceived the idea of applying his
engineering skill to the erection of a huge wheel, revolving in a
vertical plane, with cars for persons to sit in, constituting, in fact,
an enormous “merry-go-round,” as the machine once so common at country
fairs was called. The novelty of the Chicago erection was, therefore,
not the general idea, but the magnitude of the scale, which, for that
reason, involved the application of the highest engineering skill, and
the solution of hitherto unattempted practical problems. Several
thousand pounds were, in fact, expended on merely preliminary plans and
designs. The great wheel at Chicago was 250 feet in diameter, and to its
periphery were hung thirty-six carriages, each seating forty persons. At
each revolution, therefore, 1,440 people would be raised in the air to
the height of 250 feet, and from that elevation afforded a splendid
prospect, besides an experience of the peculiar sensation like that of
being in a balloon, when the spectator has no perception of his own
motion, but the objects beneath appear to have the contrary movement,
that is to say, they seem to be sinking when he is rising, and _vice
versâ_. The axle of the Chicago wheel was a solid cylinder, 32 inches in
diameter and 45 feet long; on this were two hubs, 16 feet in diameter,
to which were attached spoke rods, 2½ inches in diameter, passing in
pairs to an inner crown, which was concentric with the outer rim, but 40
feet within it. The inner and outer crowns were connected together, and
the former joined to the crown of the twin wheel by an elaborate system
of trusses and ties, which, however, left an open space between the rims
of 20 feet from the outside. These last were formed of curved riveted
hollow beams, in section 25½ inches by 19 inches, and between them,
slung upon iron axles through the roofs, were suspended, at equal
intervals, the thirty-six carriages, each 27 feet long, and weighing 13
tons without its passengers, who added 3 tons more to the weight. The
wheel with its passengers was calculated to weigh about 1,200 tons, and
it rested on two pyramidal skeleton towers of ironwork 140 feet high,
having bases 50 feet by 60 feet. The wheel was moved by power applied at
the lowest point, the peripheries of both the rims having great cogs 6
inches deep and 18 inches apart, which engaged a pair of large
cog-wheels, carried on a shaft 12 inches in diameter.

[Illustration:

  FIG. 26_g_.—_Original Design for the Great Wheel._
]

This curious structure was not begun until March, 1893, yet it was set
in motion three months afterwards, having cost about £62,500. The
Company had to hand over to the Exhibition one half of the receipts
after the big wheel had paid for its construction, but even then they
realised a handsome profit, and at the close of the World’s Fair, they
sold the machine for four-thirds of its cost, in order that it might be
re-erected at Coney Island.

No sooner had the great Ferris wheel at Chicago proved a financial
success than an American gentleman, Lieutenant Graydon, secured a patent
for a like machine in the United Kingdom; and as it has now become
almost a matter of course that some iron or steel structure, surpassing
everything before attempted, should form a part of each great
exhibition, a Company was at once formed in London, under the title of
“The Gigantic Wheel and Recreation Towers Co., Limited,” to construct
and work at the Earl’s Court Oriental Exhibition of 1895, a great wheel,
similar in general form to that of Chicago. But the design of the London
wheel had some new features, as will be seen from the sketches, Fig.
26_c_ (from _The Engineer_ of 20th April, 1894), and, moreover, having
been planned of larger dimensions than its American prototype, presented
additional engineering problems of no small complexity. After due
deliberation the scheme of the work was entrusted to Mr. Walter B.
Basset, a talented young engineer, connected with the firm of Messrs.
Maudslay, Sons, & Field, and already experienced in designing iron
structures. Under this gentleman, with the assistance of Mr. J. J.
Webster in carrying out some of the details, the work has been so
successfully accomplished that the “Great Wheel” of 1895 may be cited as
one of the crowning mechanical triumphs of the nineteenth century. The
original design has not been followed so far as regards the lower
platforms for refreshment rooms, &c. Plate V., for which we are indebted
to Mr. Basset, is a photographic representation of the actual structure.

The wheel at Earl’s Court exceeds the Ferris wheel in diameter by 50
feet, being 300 feet across. It is supported on two towers, 175 feet
high, each formed by four columns 4 feet square, built of steel plates
with internal diaphragms, and surmounted by balconies that may be
ascended in elevators raised by a weight of water, which, after having
been discharged into a reservoir under the ground level, is again pumped
up to the top of the towers. Between the balconies on each tower there
is also a communication _through the axle_ of the wheel, which, instead
of being solid as at Chicago, is a tube of 7 feet diameter, and 35 feet
long, made in sections, riveted together, of steel 1 inch thick, and
weighing no less than 58 tons. The raising and fixing in its high place
of such a mass of metal required specially ingenious devices, which have
been greatly appreciated by professional engineers. But for these
devices, the erection of scaffolding in the ordinary way of proceeding
would have entailed an outlay simply enormous. The axle is stiffened by
projecting rings, and, between pairs of these, the spoke rods are
attached by pins 3 inches in diameter. The axle was the production of
Messrs. Maudslay, Field & Co.; all the rest of the metal work was made
at the Arrol Works at Glasgow, and the carriages were constructed by
Brown, Marshall & Co., of Birmingham. The Earl’s Court wheel is turned
by a mechanism different from that of the Chicago wheel, for whereas the
latter was provided with cogs, the former has two chains, each 1,000
feet long and 8 tons weight, surrounding the periphery of the wheel on
either side. The chains go over drums in the engine-shed, from which
they pass underground to guide-pulleys, and as they unwind from the
Great Wheel, they again go over guide-pulleys to lead them back to the
drums. These chains are firmly held throughout in the jaws of V-shaped
grooves, and there are arrangements for taking up the slack. The drums
are actuated by wheel gearing, connected with two horizontal Robey steam
engines, each of 50 horse-power, one on either side, capable of being
worked singly or together. It is, however, found sufficient to use the
engine of one side only, and even then to work it at but 16 horse-power,
and the operation can be controlled by one man, who has also the command
of a brake. Both starting and stopping are accomplished with the
greatest smoothness and absence of strain or jar. There are forty
carriages, each 25 feet long, 9 feet wide, and 10 feet high. Each will
accommodate forty passengers, and these enter at the ends from eight
platforms at different heights from the ground, so arranged as to be on
the level of the eight lowest carriages while the wheel is stationary.
The passengers who have had their ride leave at the other end of the
carriages by eight similar platforms on the other side of the wheel.
After the change of passengers in one set of eight carriages, the wheel
is turned through exactly one-fifth of a revolution, which has the
effect of bringing the next eight carriages to the level of the
platforms, and it is again brought to a standstill whilst the change of
passengers is taking place; and so on, until the whole freight of say
1,600 persons has been changed during the five stoppages in one
revolution, for which about thirty-five minutes are required, and the
process of emptying and filling eight carriages at once is repeated.
There are first and second class carriages, the charge for the former
being two shillings, and for the latter one shilling; so that, reckoning
800 passengers of each class, one turn would bring to the treasury the
handsome sum of £120.

The sensations experienced in a journey on the Great Wheel are, as
already mentioned, comparable to those enjoyed by the aërial voyagers in
a balloon, where all perception of proper motion is lost, and it is the
world beneath that seems to recede and float away, presenting the while
a strangely changing panorama. Many people who have never made a balloon
ascent yet know the calm delight of floating in a boat without effort
down some placid stream, unconscious of any motion beyond that vaguely
inferred from the silent apparent gliding by of the banks. Very similar
are, in part, the feelings of the passenger who is almost imperceptibly
carried up into the air in a carriage of the Great Wheel, but the
vertical direction of the movement, and the gradual expansion of the
horizon as the vertex is approached, lend an unwonted novelty to the
situation. From the Earl’s Court Wheel the view is both interesting and
extensive, for on a clear day the prospect stretches as far as the Royal
Castle of Windsor.

The “Gigantic Wheel” at Earl’s Court was inaugurated on the 11th July,
1895, in the presence of an assemblage of 5,000 people, including many
distinguished personages, who were all treated to a ride. Plate I. shows
a portion of the wheel and carriages as in motion.

[Illustration:

  PLATE V.

  GENERAL VIEW OF THE GREAT WHEEL AT EARL’S COURT.
]

[Illustration:

  FIG. 27.—_Sir Joseph Whitworth._
]



                                 TOOLS.


Of the immense variety of tools and mechanical contrivances employed in
modern times, by far the greatest number are designed to impart to
certain materials some definite shape. The brickmaker’s mould, the
joiner’s plane, the stonemason’s chisel, the potter’s wheel, are
examples of simple tools. More elaborate are the coining press, the
machine for planing iron, the drilling machine, the turning lathe, the
rolling mill, the Jacquard loom. But all such tools and machines have
one principle in common—a principle which casual observers may easily
overlook, but one which is of the highest importance, as its application
constitutes the very essence of the modern process of _manufacture_ as
distinguished from the slow and laborious mode of making things by hand.
The principle will be easily understood by a single example. Let it be
required to draw straight lines across a sheet of paper. Few persons can
take a pen or pencil, and do this with even an approach to accuracy, and
at best they can do it but slowly and imperfectly. But with the aid of a
ruler any number of straight lines may be drawn rapidly and surely. The
former case is an instance of _making_ by hand, the latter represents
_manufacturing_, the ruler being the tool or machine. Let it be observed
that the ruler has in itself the kind of form required—that is to say,
straightness—and that in using it we copy or transfer this straightness
to the mark made on the paper. This is a simple example of the _copying
principle_, which is so widely applied in machines for manufacturing;
for, in all of these, materials are shaped or moulded by various
contrivances, so as to reproduce certain definite forms, which are in
some way contained within the machine itself. This will be distinctly
seen in the tools which are about to be described.

[Illustration:

  FIG. 28.—_Whitworth’s Screw Dies and Tap._
]

Probably no one mechanical contrivance is so much and so variously
applied as the _Screw_. The common screw-nail, which is so often used by
carpenters for fastening pieces of metal on wood, or one piece of wood
to another, is a specimen of the screw with which everybody is familiar.
The projection which winds spirally round the nail is termed the
_thread_ of the screw, and the distance that the thread advances
parallel to the axis in one turn is called the _pitch_. It is obvious
that for each turn the screw makes it is advanced into the wood a depth
equal to the pitch, and that there is formed in the wood a hollow screw
with corresponding grooves and projections. Screws are formed on the
ends of the bolts, by which various parts are fastened together, and the
hollow screws which turn on the ends of the bolts are termed _nuts_. The
screws on bolts and nuts, and other parts of machines, were formerly
made with so many different pitches that, when a machine constructed by
one maker had to be repaired by another, great inconvenience was found,
on account of the want of uniformity in the shape and pitch of the
threads. A uniform system was many years ago proposed by Sir Joseph
Whitworth, and adopted by the majority of mechanical engineers, who
agreed to use only a certain defined series of pitches. The same
engineer also contrived a hand tool for cutting screws with greater
accuracy than had formerly been attained in that process. A mechanic
often finds it necessary to form a screw-thread on a bolt, and also to
produce in metal a hollow screw. The reader may have observed
gas-fitters and other workmen performing the first operation by an
instrument having the same general appearance as Fig. 28. This contains
hard steel _dies_, which are made to press on the bolt or pipe, so that
when the _guide-stock_ is turned by the handles, the required grooves
are cut out. The arrangement of these dies in Sir Joseph Whitworth’s
instrument is shown in Fig. 28, which represents the central part of the
guide-stock; A, B, C are the steel dies retained in their places, when
the instrument is in use, by a plate which can be removed when it is
necessary to replace one set of dies by another, according to the pitch
of thread required. The figure also shows the set of dies, A, B, C,
removed from the guide-stock. D is the work, pressed up against the
fixed die, A, by B and C, the pressure being applied to these last as
required by turning the nut, thus drawing up the key, E, so that the
inclined planes, _f_, _g_, press against similar surfaces forming the
ends of the dies. For producing the hollow screws, _taps_ are provided,
which are merely well-formed screws, made of hard steel and having the
threads cut into detached pieces by several longitudinal grooves, as
represented in the lower part of Fig. 28.

[Illustration:

  FIG. 29.—_Screw-cutting Lathe._
]

The method of forming screws by dies and taps is, however, applicable
only to those of small dimensions, and even for these it is not employed
where great accuracy is required. Perfect screws can only be cut with a
lathe, such as that represented in Fig. 29. In this we must first call
the reader’s attention to the portion of the apparatus marked A, which
receives the name of the _slide-rest_. The invention of this contrivance
by Maudsley had the effect of almost revolutionizing mechanical art, for
by its aid it became possible to _produce true surfaces in the lathe_.
Before the slide-rest was introduced, the instrument which cut the wood
or metal was held in the workman’s hand, and whatever might be his skill
and strength, the steadiness and precision thus obtainable were far
inferior to those which could be reached by the grip of an iron hand,
guided by unswerving bars. The slide-rest was contrived by Maudsley in
the first instance for cutting screws, but its principle has been
applied for other purposes. This principle consists in attaching the
cutting tool to a slide which is incapable of any motion, except in the
one direction required. Thus the slide, A, represented in Fig. 29, moves
along the _bed_ of the lathe, B, carrying the cutter with perfect
steadiness in a straight line parallel to the axis of the lathe. There
are also two other slides for adjusting the position of the cutter; the
handle, _a_, turns a screw, which imparts a transverse motion to the
piece, _b_, and the tool receives another longitudinal movement from the
handle, _c_. The pieces are so arranged that these movements take place
in straight lines in precisely the required direction, and without
permitting the tool to be unsteady, or capable of any rocking motion. In
Whitworth’s lathe, between the two sides of the bed, and therefore not
visible in the figure, is a shaft placed perfectly parallel to the axis
of the lathe. One end of this shaft is seen carrying the wheel, C, which
is connected with a train of wheels, D, and is thus made to revolve at a
speed which can be made to bear any required proportion to that of the
mandril, E, of the lathe, by properly arranging the numbers of the teeth
in the wheels; and the machine is provided with several sets of wheels,
which can be substituted for each other. The greater part of the length
of this shaft is formed with great care into an exceedingly accurate
screw, which works in a nut forming part of the slide-rest. The effect,
therefore, of the rotation of the screw is to cause the slide-rest to
travel along the bed of the lathe, advancing with each revolution of the
screw through a space equal to its pitch distance. There is an
arrangement for releasing the nut from the guiding-screw, by moving a
lever, and then by turning the winch the slide-rest is moved along by a
wheel engaging the teeth of a rack at the back of the lathe. Now, if the
train of wheels, C D, be so arranged that the screw makes one revolution
for each turn of the mandril, it follows that the cutting tool will move
longitudinally a distance equal to the pitch of the guiding-screw while
the bar placed in the lathe makes one turn. Thus the point of the cutter
will form on the bar a screw having the same pitch as the guiding-screw
of the lathe.

Here we have a striking illustration of the copying principle, for the
lathe thus produces an exact copy of the screw which it contains. The
screw-thread is traced out on the cylindrical bar, which is operated
upon by the combination of the circular motion of the mandril with the
longitudinal movement of the slide-rest. By modifying the relative
amounts of these movements, screw-threads of any desired pitch can be
made, and it is for this purpose that the _change wheels_ are provided.
If the thread of the guiding-screw makes two turns in one inch, one
revolution of the wheel C will advance the cutter half an inch along the
length of the bar. If the numbers of teeth in the wheels be such that
the wheel D makes ten revolutions while C is making one, then in the
length of half an inch the thread of the screw produced by the cutter
will go round the core ten times, or, in technical language, the screw
will be of 1/20 inch pitch.

[Illustration:

  FIG. 30.—_Whitworth’s Measuring Machine._
]

Since a screw turning in a nut advances only its pitch distance at each
revolution, a finely-cut screw furnishes an instrument well adapted to
impart a slow motion, or to measure minute spaces. Suppose a screw is
cut so as to have fifty threads in an inch, then each turn will advance
it 1/50 in.; half a turn 1/100 in.; a quarter of a turn, 1/200, and so
on. It is quite easy to attach a graduated circle to the head of the
screw, so that, by a fixed pointer at the circumference, any required
fraction of a revolution may be read off. Thus if the circle had two
hundred equal parts, we could, by turning the screw so that one division
passed the index, cause the screw to advance through 1/200 of 1/50 inch,
or 1/10000 part of an inch. This is the method adopted for moving the
cross-wires of the instruments for measuring very small spaces under the
microscope. Sir Joseph Whitworth, who has done so many great things in
mechanical art, was the first mechanician to perceive the importance of
extreme accuracy of workmanship, and he invented many beautiful
instruments and processes by which this accuracy might be attained. Fig.
30 represents one of his measuring machines, intended for practical use
in the workshop, to test the dimensions of pieces of metal where great
precision is required. The base of the machine is constructed of a rigid
cast iron bed bearing a fixed headstock, A, and a movable one, B, the
latter sliding along the bed, C, with a slow movement, when the handle,
D, is turned. This slow motion is produced by a screw on the axis, _a_,
working in the lower part of the headstock, just as the slide-rest is
moved along the bed of the lathe. The movable headstock, when it has
been moved into the position required, is firmly clamped by a
thumbscrew. The face of the bed is graduated into inches and their
subdivisions. Here it should be explained that the machine is not
intended to be used for ascertaining the absolute dimensions of objects,
but for showing by what fraction of an inch the size of the work
measured differs from a certain standard piece. Each headstock carries a
screw of 1/20 inch pitch, made with the greatest possible care and
accuracy. To the head of the screw in the movable headstock is attached
the wheel, _b_, having its circumference divided into 250 equal parts,
and a fixed index, _c_, from which its graduations may be counted. An
exactly similar arrangement is presented in connection with the screw
turning in the fixed headstock, but the wheel is much larger, and its
circumference is divided in 500 equal parts. It follows, therefore, that
if the large wheel be turned so that one division passes the index, the
bar moves in a straight line 1/500 of the 1/20 of an inch, that is,
1/10000 an inch. The ends of the bars, _d_ and _e_, are formed with
perfectly plane and parallel surfaces, and an ingenious method is
adopted of securing equality of pressure when comparisons are made. A
plate of steel, with perfectly parallel faces, called a _gravity-piece_,
or _feeler_, is placed between the flat end of the bar and the
standard-piece, and the pressure when the screw-reading is taken must be
just sufficient to prevent this piece of steel from slipping down, and
that is the case when the steel remains suspended and can nevertheless
be easily made to slide about by a touch of the finger. Thus any piece
which, with the same screw-readings, sustains the gravity-piece in the
same manner as the standard, will be of exactly the same length; or the
number of divisions through which the large wheel must be turned to
enable it to do so tells the difference of the dimensions in
ten-thousandth parts of an inch. By this instrument, therefore, gauges,
patterns, &c., can be verified with the greatest precision, and pieces
can be reproduced perfectly agreeing in their dimensions with a standard
piece. Thus, for example, the diameters of shafting can be brought with
the greatest precision to the exact size required to best fit their
bearings.

In another measuring machine on the same principle the delicacy of the
measurement has been carried still farther, by substituting for the
large divided wheel one having 200 teeth, which engage an endless screw
or worm. This will easily be understood by reference to Fig. 31, where a
similar arrangement is applied to another purpose. Imagine that a wheel
like P, Fig. 31, but with 200 teeth, has taken the place of E in Fig.
30, and that the wheel, T, on the axis of the endless screw is shaped
like E, Fig. 30. One turn of the axis carrying the endless screw,
therefore, turns the wheel through 1/200 of a revolution, and as this
axis bears a graduated head, having 250 divisions, the screw having 20
threads to the inch, is, when one division passes the index, advanced
through a space equal to 1/250 × 1/200 × 1/20, or 1/1000000 an inch;
that is, the one-millionth part of an inch. This is an interval so small
that ten times its length would hardly be appreciated with the highest
powers of the microscope, and the machine is far too delicate for any
practical requirements of the present day. It will indicate the
expansion caused by heat in an iron bar which has merely been touched
with the finger for an instant, and even the difference of length
produced by the heat radiated from the person using it. A movement of
1/1000000 of an inch is shown by the gravity-piece remaining suspended
instead of falling, and the piece falls again when the tangent-screw is
turned back through 1/250 of a revolution, a difference of reading
representing a possible movement of the measuring surface through only
2/1000000 an inch. This proves the marvellous perfection of the
workmanship, for it shows that the amount of play in the bearings of the
screws does not exceed one-millionth of an inch.

A good example of a machine-tool is the _Drilling Machine_, which is
used for drilling holes in metal. Such a machine is represented in Fig.
31, where A is the strong framing, which is cast in a single piece, in
order to render it as rigid as possible. The power is applied by means
of a strap round the speed pulley, B, by which a regulated speed is
communicated to the bevel wheel, C, which drives D, and thus causes the
rotation of the hollow shaft, E. In the lower part of the latter is the
spindle which carries the drilling tool, F, and upon this spindle is a
longitudinal groove, into which fits a projection on the inside of E.
The spindle is thus forced to rotate, and is at the same time capable of
moving up and down. The top of the spindle is attached to the lower end
of the rack, G, by a joint which allows the spindle to rotate freely
without being followed in its rotation by the rack, although the latter
communicates all its vertical movements to the spindle, as if the two
formed one piece. The teeth of the rack are engaged by a pinion, which
carries on its axis the wheel H, turned by an endless screw on the
shaft, I, which derives its motion by means of another wheel and endless
screw from the shaft, K. The latter is driven by a strap passing over
the _speed pulleys_, L and M, and thus the speed of the shaft K can be
modified as required by passing the strap from one pair of pulleys to
another. The result is that the rack is depressed by a slow movement,
which advances the drill in the work, or, as it is technically termed,
gives the _feed_ to the drill. By a simple piece of mechanism at N the
connection of the shafts K and I can be broken, and the handle O made to
communicate a more rapid movement to I, so as to raise up the drill in a
position to begin its work again, or to bring it quickly down to the
work, and then the arrangement for the self-acting feed is again brought
into play. By turning the wheel, P, the table, Q, on which the work is
fastened, is capable of being raised or lowered, by means of a rack
within the piece R, acted on by a pinion carried on the axle, P. The
table also admits of a horizontal motion by the slide S, and may besides
be swung round when required.

[Illustration:

  FIG. 31.—_Whitworth’s Drilling Machine._
]

The visitor to an engineer’s workshop cannot fail to be struck with the
operation of the powerful _Lathes_ and _Planing Machines_, by which long
thick flakes or shavings of iron are removed from pieces of metal with
the same apparent ease as if the machine were paring cheese. The figure
on the opposite page represents one of the larger forms of the planing
machine, as constructed by Sir J. Whitworth. The piece of work to be
planed is firmly bolted down to the table, A, which moves upon the
Ꮩ-shaped surfaces, running its whole length, and accurately fitting into
corresponding grooves in a massive cast iron bed. The bevel wheel, of
which a portion is seen at B, is keyed on a screw, which extends
longitudinally from end to end of the bed. This screw works in nuts
forming part of the table, and as it turns in sockets at the ends of the
bed, it does not itself move forward, but imparts a progressive movement
to the table, and therefore to the piece of metal to be planed. As this
table must move backwards and forwards, there must be some contrivance
for reversing the direction of the screw’s rotation, and this is
accomplished in a beautifully simple manner by an arrangement which a
little consideration will enable any one to understand. It will be
observed that there are three drum-pulleys at C. Let the reader confine,
for the present, his attention to the nearest one, and picture to
himself that the shaft to which it is attached is placed in the same
horizontal plane as the axis of the screw and at right angles to it,
passing in front of bevel wheel B. A small bevel wheel turning with this
shaft, and engaging the teeth of the wheel B, may, it is plain,
communicate motion to the screw. Now let the reader consider what will
be the effect on the _direction_ of the rotation of B of applying the
bevelled pinion to the nearer or to the farther part of its
circumference, supposing the direction of the rotation of this pinion to
be always the same. He will perceive that the direction in one case will
be the reverse of that in the other. The shaft to which the nearest
pulley is attached carries a pinion engaging the wheel at its farther
edge, and therefore the rotation of this pulley in the same direction as
the hands of a watch causes the wheel B to rotate so that its upper part
moves towards the spectator. The farthest pulley, _a_, turns with a
hollow shaft, through which the shaft of the nearest pulley simply
passes, without any connection between them, and this hollow shaft
carries a pinion, which engages the teeth of B at the nearer edge, and,
in consequence, the rotation of the farther pulley, _a_, in the
direction of the hands of a watch, would cause the upper part of B to be
moving from the spectator. The middle pulley, _b_, runs loosely on the
shaft, and the driving-strap passes through the guide, _c_, and it is
only necessary to move this, so as to shift the strap from one drum to
another, in order to reverse the direction of the screw and the motion.
This shifting of the strap is done by a movement derived from the table
itself, on which are two adjustable stops, D and E, acting on an
arrangement at the base of the upright frame when they are brought up to
it by the movement of the table, so as not only to shift the strap, but
also to impart a certain amount of rotation to upright shaft, F, in each
direction alternately. The piece which carries the tools, G and H, is
placed horizontally, and can be moved vertically by turning the axis, I,
thus causing an equal rotation of two upright screws of equal pitch,
which are contained within the uprights and work in nuts, forming part
of the tool-box. The pieces carrying the tools are moved horizontally by
the screws which are seen to pass along the tool-box, and these screws
receive a certain regulated amount of motion at each reversal of the
movement of the table from the mechanism shown at K. The band-pulley, L,
receives a certain amount of rotation from the same shaft, and the
catgut band passing round the tops of the cylinders which carry the
cutters is drawn in alternate directions at the end of each stroke, the
effect being to turn the cutters half round, so as always to present
their cutting edges to the work. There are also contrivances for
maintaining the requisite steadiness in the tools and for adjusting the
depth of the cut. The cutting edge of the tools is usually of a Ꮩ-shape,
with the angle slightly rounded, and the result of the process is not
the production of a plane, but a grooved surface. But by diminishing the
amount of horizontal _feed_ given to the cutters, the grooves may be
made finer and finer, until at length they disappear, and the surface is
practically a plane. Planing machines are sometimes of a very large
size. Sir J. Whitworth has one the table of which is 50 ft. in length,
and the machine is capable of making a straight cut 40 ft. long in any
article not exceeding 10 ft. 6 in. high or 10 ft. wide.

[Illustration:

  FIG. 32.—_Whitworth’s Planing Machine._
]

[Illustration:

  FIG. 33.—_Pair of Whitworth’s Planes, or Surface Plates._
]

The copying principle is evident in this machine; for the plane surface
results from the combination of the straightness of the bed with the
straightness of the transverse slide along which the tools are moved. It
should, moreover, be observed that it is precisely this machine which
would be employed for preparing the straight sliding surfaces required
in the construction of planing and other machines, and thus one of these
engines becomes the parent, as it were, of many others having the same
family likeness, and so on _ad infinitum_. Thus, having once obtained
perfectly true surfaces, we can easily reproduce similar surfaces. But
the reader may wish to know how such forms have been obtained in the
first instance; how, for example, could a perfectly plane surface be
fashioned without any standard for comparison? This was first perfectly
done by Sir J. Whitworth, forty-five years ago. Three pieces of iron
have each a face wrought into comparatively plane surfaces; they are
compared together, and the parts which are prominent are reduced first
by filing, but afterwards, as the process approaches completion, by
scraping, until the three perfectly coincide. The parts where the plates
come in contact with each other are ascertained by smearing one of them
with a little oil coloured with red ochre: when another is pressed
against it, the surfaces of contact are shown by the transference of the
red colour. Three plates are required, for it is possible for the
prominences of No. 1 exactly to fit into the hollows of No. 2, but in
that case _both_ could not possibly exactly coincide with the surface of
No. 3; for if one of them did (say No. 1), then No. 3 must be exactly
similar to No. 2, and consequently when No. 2 was applied to No. 3,
hollow would be opposed to hollow and prominence to prominence. A little
reflection will show that only when the three surfaces are truly plane
will they exactly and entirely coincide with each other. The planes,
when thus carefully prepared, approach to the perfection of the ideal
mathematical form, and they are used in the workshop for testing the
correctness of surfaces, by observing the uniformity or otherwise of the
impression they give to the surface when brought into contact with it,
after being covered by a very thin layer of oil coloured by
finely-ground red ochre.

Fig. 33 represents a small pair of Whitworth’s planes. When one of these
is placed horizontally upon the other, it does not appear to actually
come in contact with it, for the surfaces are so true that the air does
not easily escape, but a thin film supports the upper plate, which
glides upon it with remarkable readiness (A). When, however, one plate
is made to slide over the other, so as to exclude the air, they may both
be lifted by raising the upper one (B). This effect has, by several
philosophers, been attributed to the mere pressure of the atmosphere;
but recent experiments of Professor Tyndall’s show that the plates
adhere even in a vacuum. The adhesion appears therefore to be due to
some force acting between the substances of the plates, and perhaps
identical in kind with that which binds together the particles of the
iron itself.

[Illustration:

  FIG. 34.—_Interior of Engineer’s Workshop._
]

[Illustration:

  FIG. 35.—_The Blanchard Lathe._
]


                         _THE BLANCHARD LATHE._

This machine affords a striking example of the application of the
copying principle which is the fundamental feature of modern
manufacturing processes. It would hardly be supposed possible, until the
method had been explained, that articles in shape so unlike geometrical
forms as gun-stocks, shoemakers’ lasts, &c., could be turned in a lathe.
The mode in which this is accomplished is, however, very simple in idea,
though in carrying that idea into practice much ingenious contrivance
was required. The illustration, Fig. 35, represents a Blanchard’s lathe,
very elegantly constructed by Messrs. Greenwood and Batley, of Leeds.
The first obvious difference between an ordinary lathe and Blanchard’s
invention is that in the former the work revolves rapidly and the
cutting-tool is stationary, or only slowly shifts its position in order
to act on fresh portions of the work, while in the latter the work is
slowly rotated and the cutting-tools are made to revolve with very great
velocity. Again, it will be observed that the headstock of the Blanchard
lathe, instead of one, bears _two_ mandrels, having their axes parallel
to each other. One of these carries the pattern, C, which in the figure
has the exact shape of a gun-stock that is to be cut in the piece of
wood mounted on the nearer spindle. One essential condition in the
arrangement of the apparatus is that the pattern and the work having
been fixed in similar and parallel positions, shall always continue so
at every point of their revolutions. This is easily accomplished by
placing exactly similar toothed wheels on the two axles, and causing
these to be turned by one and the same smaller toothed wheel or pinion.
The two axles must thus always turn round in the same direction and with
exactly the same speed, so that the work which is attached to one, and
the pattern which is fixed on the other, will always be in the same
phase of their revolutions. If, for example, the part of the wood which
is to form the upper part of the gun-stock is at the bottom, the
corresponding part of the pattern will also be at the bottom, as in the
figure, and both will turn round together, so that every part of each
will be at every instant in a precisely similar position. The wood to be
operated upon is, it must be understood, roughly shaped before it is put
into the lathe. The toothed wheels and the pinion which drives them are
in the figure hid from view by the casing, _h_, which covers them. The
pinion receives the power from a strap passing over _f_. The cutters are
shown at _e_; they are placed radially, like the spokes of a wheel, and
have all their cutting edges at precisely one certain distance from the
axis on which they revolve, so that they all travel through the same
circle. These cutting-edges, it may be observed, are very narrow, almost
pointed. The shaft carrying the cutters is driven at a very high speed,
by means of a strap passing over _k_ and _i_. The number of revolutions
made by the cutters in one second is usually more than thirty. The great
peculiarity of the lathe consists in the manner in which the position of
the cutters is made to vary. The axle which carries them rotates in a
kind of frame, which can move backwards and forwards, so that the
cutters may be readily put at any desired distance from the axis of the
work. Their position is, however, always dependent on the pattern, for,
fixed in a similar frame, _b_, which is connected with the former, is a
small disc wheel, _a_, having precisely the same radius as that of the
circle traced out by the cutters, and this disc is made by a strong
spring to press against the pattern. The cutters, being fixed in the
same rocking-frame which carries this guiding-wheel, must partake of all
its backward and forward motions, and as the cutting-wheel and the
guide-wheel are so arranged as to have always the same relative
positions to the axes of the two headstocks, it follows that the edges
of the cutters will trace out identically the same form as the
circumference of the guiding-disc. The latter is, of course, not driven
round, but simply turns slowly with the pattern by friction, for it is
pressed firmly against the pattern by a spring or weight acting on the
frame, in order that the cutters may be steadily maintained in their
true, but ever-varying, position. The rocking-frame receives a slow
longitudinal motion by means of the screw, _n_, so that the cutters are
carried along the work, and the guide along the pattern.

The whole arrangement is self-acting, so that when once the pattern and
the rough block of wood have been fixed in their positions, the machine
completes the work, and produces an exact repetition of the shape of the
pattern. It is plain that any kind of forms can be easily cut by this
lathe, the only condition being that the surface of the pattern must not
present any re-entering portions which the edge of the guide-wheel
cannot follow. The machine is largely used for the purposes named above,
and also for the manufacture of the spokes of carriage-wheels. The
limits of this article will not permit of a description of the beautiful
adjustments given to the mechanism in the example before us,
particularly in the arrangement for driving the cutters in a framework
combining lateral and longitudinal motions; but the intelligent reader
may gather some hints of these by a careful inspection of the figure.
The machine is sometimes made with the frame carrying the guide-wheel
and cutters, not rocking but sliding in a direction transverse to the
axes of the headstocks. It is extremely interesting to see the Blanchard
lathe at work, and observe how perfectly and rapidly the curves and form
of the patterns seem to grow, as it were, out of the rudely-shaped piece
of wood, which, of course, contains a large excess of material, or, in
the picturesque and expressive phrase of the workmen, _always gives the
machine something to eat_.

[Illustration:

  FIG. 36.—_Vertical Saw._
]


                           _SAWING MACHINES._

With the exception of the last, all the machines hitherto described in
the present article are distinguished by this—they are tools which are
used to produce other machines of every kind. Without such implements it
would be impossible to fashion the machines which are made to serve so
many different ends. Another peculiarity of these tools has also been
referred to, namely, that they are especially serviceable, and indeed
essential, for the reproduction of others of the same class. Thus, the
accurate leading-screw of the lathe is the means used to cut other
accurate screws, which shall in their turn become the leading-screws of
other lathes, and a lathe which forms a truly circular figure is a
necessary implement for the construction of another lathe which shall
also produce truly circular figures. In these tools, therefore, we find
the copying principle, to which allusion has been already made, as the
great feature of all machines; but in order to bring this principle
still more clearly before the reader, we have described in the Blanchard
Lathe a machine of a somewhat different class, because it embodied a
very striking illustration of the principle in question. We are far from
having described all the implements of the mechanical engineer, or even
all the more interesting ones; for example, we have given no account of
the powerful lathes in which great masses of iron are turned, or of the
analogous machines, which, with so much accuracy, shape the internal
surfaces of the cylinders of steam engines, of cannons, &c. The history
of the steam engine tells us of the difficulties which Watt had to
contend with in the construction of his cylinders, for no machine at
that time existed capable of boring them with an approach to the
precision which is now obtained.

[Illustration:

  FIG. 37.—_Circular Saw._
]

The kind of general interest which attaches to the tools we have already
described is not wanting in yet another class of machine-tools, namely,
those employed in converting timber into the forms required to adapt it
for the uses to which it is so extensively applied. And for popular
illustration, this class of tools presents the special advantage of
being readily understood as regards their purpose and mode of action,
while their simplicity in these respects does not prevent them from
showing the advantages of machine over hand labour. Everybody is
familiar with the up-and-down movement of a common saw, and in the
machine for sawing balks of timber into planks, represented in Fig. 36,
this reciprocating motion is retained, but there are a number of saws
fixed parallel to each other in a strong frame, at a distance
corresponding to the thickness of the planks. The saws are not placed
with their cutting edges quite upright, but these are a little more
forward at the top, so that as they descend they cut into the wood, but
move upwards without cutting, for the teeth then recede from the line of
the previous cut, while in the meantime the balk is pushed forward ready
for the next descent of the saw-frame. This pushing forward, or
_feeding_, of the timber is accomplished by means of ratchet-wheels,
which are made to revolve through a certain space after each descent of
the saw-frame, and, by turning certain pinions, move forward the
carriage on which the piece of timber is firmly fixed, so that when the
blades of the saws are beginning the next descent they are already in
contact with the edge of the former cut. To prevent the blades from
moving with injurious friction in the saw-cuts, these last are made of
somewhat greater width than the thickness of the blades, by the simple
plan of bending the teeth a little on one side and on the other
alternately. The rapidity with which the machine works, depends of
course on the kind of wood operated upon, but it is not unusual for such
a machine to make more than a hundred cuts in the minute. The figure
shows the machine as deriving its motion by means of a strap passing
over a drum, from shafting driven by a steam engine. This is the usual
plan, but sometimes the steam power is applied directly, by fixing the
piston-rod of a steam cylinder to the top of the saw-frame, and
equalizing the motion by a fly-wheel on a shaft, turned by a crank and
connecting-rod.

A very effective machine for cutting pieces of wood of moderate
dimensions is the _Circular Saw_, represented in Fig. 37. Here there is
a steel disc, having its rim formed into teeth; and the disc is made to
revolve with very great speed, in some cases making as many as five
hundred turns in a minute, or more than eight in a second. On the bench
is an adjustable straight guide, or fence, and when this has been fixed,
the workman has only to press the piece of wood against it, and push the
wood at the same time towards the saw, which cuts it at a very rapid
rate. Sometimes the circular saw is provided with apparatus by which the
machine itself pushes the wood forwards, and the only attention required
from the workman is the fixing of the wood upon the bench, and the
setting of the machine in gear with the driving-shaft. Similar saws are
used for squaring the ends of the iron rails for railways, two circular
saws being fixed upon one axle at a distance apart equal to the length
of the rails. The axle is driven at the rate of about 900 turns per
minute, and the iron rail is brought up parallel to the axle, being
mounted on a carriage, and still red hot, when the two ends are cut at
the same time by the circular saws, the lower parts of which dip into
troughs of water to keep them cool.

[Illustration:

  FIG. 38.—_Pit-Saw._
]

[Illustration:

  FIG. 39.—_Box Tunnel._
]



                               RAILWAYS.


[Illustration:

  FIG. 40.—_Coal-pit, Salop._
]

Towards the end of last century, tramways formed by laying down narrow
plates of iron, were in use at mines and collieries in several parts of
England. These plates had usually a projection or flange on the inner
edge, thus—L, in order to keep the waggons on the track, for the wheels
themselves had no flange, but were of the kind used on ordinary roads.
These flat tramways were found liable to become covered up with dirt and
gravel, so that the benefit which ought to have been obtained from their
smoothness was in a great measure lost. _Edge rails_ were, therefore,
substituted, and the wheels were kept on the rails by having a _flange_
cast on the inner edge of the rim. The rails were then always made of
cast iron, for, although they were very liable to break, the great cost
of making them of wrought iron prevented that material from being used
until 1820, when the method of forming rails of malleable iron by
rolling came into use. The first time a tramway was used for the
conveyance of passengers was in 1825, when the Stockton and Darlington
Railway was opened—a length of thirty-seven miles. It appears that the
carriages were at first drawn by horses, although locomotives were used
on this and other colliery lines for dragging, at a slow rate, trains of
mineral waggons. At that time engineers were exercising their ingenuity
in overcoming a difficulty which never existed by devising plans for
giving tractive power to the locomotive through the instrumentality of
rack-work rails. It never occurred to them to first try whether the
adhesion of the smooth wheel to the smooth rail was not sufficient for
the purpose. During the first quarter of the present century the greater
part of the goods and much passenger traffic was monopolized by the
canals. It is quoted, as a proof of the careless manner in which this
service was performed, that the transport of bales of cotton from
Liverpool to Manchester sometimes occupied twice the length of time
required in their voyage across the Atlantic. When an Act of Parliament
authorizing the construction of a railway between Liverpool and
Manchester was applied for, the canal companies succeeded in retarding,
by their influence, the passing of that Act for two years. It was
passed, however, in 1828, and the construction of the line was proceeded
with. This line was at first intended only for the conveyance of goods,
especially of cotton and cotton manufactures, and the waggons were to be
drawn by horses. When the line was nearly finished the idea of employing
horses was, at the instigation of Mr. George Stephenson, abandoned in
favour of steam power. The directors were divided in opinion as to
whether the carriage should be dragged by ropes wound on large drums by
stationary engines, or whether locomotives should be employed. Finally,
the latter plan was adopted, and it was also suggested that passengers
might be carried. The directors offered a prize for the best locomotive,
and the result has been already mentioned. In the light of our
experience since that time, it is curious to read of the doubts then
entertained by skilful engineers about the success of the locomotive. In
a serious treatise on the subject, one eminent authority hoped “that he
might not be confounded with those hot-brained enthusiasts who
maintained the possibility of carriages being driven by a steam engine
on a railway at such a speed as twelve miles an hour.” When the “Rocket”
had accomplished the unprecedented velocity of twenty-nine miles an
hour, and the railway was opened for passengers as well as goods, the
thirty stage coaches daily plying between Liverpool and Manchester found
their occupation gone, and all ceased to run except one, which had to
depend on the roadside towns only, while the daily number of passengers
between the two cities rose at once from 500 to 1,600. In that
delightful book, Smiles’s “Life of George Stephenson,” may be found most
interesting details of the difficulties attending the introduction of
railways, especially with regard to the construction of this first
important line. Mr. Smiles relates how the promoters of the scheme
struggled against “vested interests;” how the canal proprietors,
confident at first of a secure and continuous enjoyment of their
monopoly, ridiculed the proposed railway, and continued their exorbitant
charges and tardy conveyance, pocketing in profits the prime cost of
their canal about every three years; how, roused into active opposition,
they did all in their power to thwart the new scheme; how the Lord Derby
and the Lord Sefton of that day, and other landowners, offered every
resistance to the surveyors; how the Duke of Bridgewater’s farmers would
not allow them to enter their fields, and the Duke’s gamekeepers had
orders to shoot them; how even a clergyman threatened them with personal
violence, and they had to do their work by stealth, while the reverend
gentleman was conducting the services in his church; how newspaper and
other writers declared that the locomotives would kill the birds,
prevent cows from grazing and hens from laying, burn houses, and cause
the extinction of the race of horses. All the civil engineers scouted
the idea of a locomotive railway, and Stephenson was held up to derision
as an ignoramus and a maniac by the “most eminent lawyers,” and the most
advanced and “respectable” professional C.E.s of the time. An article
appeared in the “Quarterly Review,” very favourable to the construction
of railways, but remarking in reference to a proposed line between
London and Woolwich: “What can be more palpably absurd and ridiculous
than the prospect held out of locomotives travelling _twice as fast as
stage coaches_! We should as soon expect the people of Woolwich to
suffer themselves to be fired off upon one of Congreve’s _ricochet_
rockets as trust themselves to the mercy of a machine going at such a
rate. We will back old Father Thames against the Woolwich Railway for
any sum. We trust that Parliament will, in all railways it may sanction,
limit the speed to _eight or nine miles an hour_, which we entirely
agree with Mr. Sylvester is as great as can be ventured on with safety.”
This passage, which reads so strangely now, may be seen in the
“Quarterly Review” for March, 1825. But still more curious appear now
the reports of the debates in Parliament, and of the evidence taken
before the Parliamentary Committee, in which we find the opinions and
fears of the best informed men of that period, and trace the frantic
efforts of the holders of the “vested interests” to retain them, however
obstructive of the public good.

[Illustration:

  FIG. 41.—_Sankey Viaduct._
]

[Illustration:

  FIG. 42.—_Rails and Cramp-gauge._
]

When it has been decided to construct a railway between two places, the
laying-out of the line is a subject requiring great consideration and
the highest engineering skill—for the matter is, on account of the great
cost, much more important than the setting-out of a common road. The
idea of a perfect railroad is that of a straight and level line from one
terminus to another; but there are many circumstances which prevent such
an idea from being ever carried into practice. First, it is desirable
that the line should pass through important towns situated near the
route; and then the cost of making the roadway straight and level, in
spite of natural obstacles, would be often so great, that to avoid it
detours and inclines must be submitted to—the inconvenience and the
increased length of road being balanced by the saving in the cost of
construction. It is the business of the engineer who lays out the line
to take all these circumstances into consideration, after he has made a
careful survey of the country through which the line is to pass. The
cost of making railways varies, of course, very much according to the
number and extent of the tunnels, cuttings, embankments, or other works
required. The average cost of each mile of railway in Great Britain may
be stated as about £35,000. The road itself when the rails are laid down
is called _the permanent way_, perhaps originally in distinction to the
temporary tramways laid down by the contractors during the progress of
the works. The permanent way is formed first of _ballast_, which is a
layer of gravel, stone, or other carefully chosen material, about 2 ft.
deep, spread over the roadway. Above the ballast and partly embedded in
it are placed the _sleepers_, which is the name given to the pieces of
timber on which the rails rest. These timbers are usually placed
transversely—that is, across the direction of the rails, in the manner
shown in Fig. 42. This figure also represents the form of rails most
commonly adopted, and exhibits the mode in which they are fastened down
to the sleepers by means of the iron _chairs_, _b_ _c_, the rail being
firmly held in its place by an oak wedge, _d_. These wedges are driven
in while the rails are maintained at precisely the required distance
apart by the implement, _e f_, called a _cramp gauge_, the chairs having
previously been securely attached to the sleepers by bolts or nails. The
double ⟙ form of rail has several important advantages, such as its
capability of being reversed when the upper surface is worn out, and the
readiness with which the ends of the rails can be joined by means of
_fish-plates_. These are shown in Fig. 43, where in a we are supposed to
be looking down on the rails, and in B to be looking at them sideways.
In Fig. 44 we have the rail and fish-plates in section. The holes in the
rails through which the bolts pass are not round but oval, so that a
certain amount of play is permitted to the ends of the rails.

[Illustration:

  FIG. 43.—_Fish-plate._
]

It may easily be seen on looking at a line of rails that they are not
laid with the ends quite touching each other, or, at least, they are not
usually in contact. The reason of this is that space must be allowed for
the expansion which takes place when a rise in the temperature occurs.
If the rails are laid down when at the greatest temperature they are
likely to be subject to, they may then be placed in actual contact; but
in cold weather a space will be left by their contraction. For this
reason it is usual when rails are laid to allow a certain interval; thus
rails 20 ft. long laid when the temperature is 70°, are placed with
their ends 1/20th of an inch apart, at 30° 1/10th of an inch apart, and
so on. The neglect of this precaution has sometimes led to damage and
accidents. A certain railway was opened in June, and after an excursion
train had in the morning passed over it, the midday heat so expanded the
iron, that the rails became in some places elevated 2 ft. above the
level, and the sleepers were torn up; so that, in order to admit of the
return of the train, the rails had to be hastily relaid in a kind of
zigzag. In June, 1856, a train was thrown off the metals of the
North-Eastern Railway, in consequence of the rails rising up through
expansion.

[Illustration:

  FIG. 44.—_Section of Rails and Fish-plates._
]

The distance between the rails in Great Britain is 4 ft. 8½ in., that
width having been adopted by George Stephenson in the construction of
the earlier lines. Brunel, the engineer of the Great Western, adopted,
however, in the construction of that railway, a gauge of 7 ft., with a
view of obtaining greater speed and power in the engines, steadiness in
the carriages, and increased size of carriages for bulky goods. The
proposal to adopt this gauge gave rise to a memorable dispute among
engineers, often called “The Battle of the Gauges.” It was stated that
any advantages of the broad gauge were more than compensated by its
disadvantages. The want of uniformity in the gauges was soon felt to be
an inconvenience to the public, and a Parliamentary Committee was
appointed to consider the subject. They reported that either gauge
supplied all public requirements, but that the broad gauge involved a
great additional outlay in its construction without any compensating
advantages of economy in working; and, as at that time 2,000 miles of
railway had been constructed on the narrow gauge, whereas only 270 miles
were in existence on the broad gauge, they recommended that future
railways should be made the prevailing width of 56½ in. The Great
Western line had engines, bridges, tunnels, viaducts, &c., on a larger
scale than any other railway in Britain. The difference of gauge was
after a time felt to involve so much inconvenience that lines which
adopted the 7–ft. gauge have since relaid the tracks at the more common
width. At the present day we find the Great Western Railway completely
reconstructed on the narrow gauge system, in order that trains may run
without interruption in connection with other lines.

[Illustration:

  FIG. 45.—_Conical Wheels._
]

[Illustration:

  FIG. 46.—_Centrifugal Force._
]

The wheels of railway carriages and engines differ from those of
ordinary carriages in being fastened in pairs upon the axles, with which
they revolve (see Fig. 45). The tire of the wheel is conical, the slope
being about 1 in 20; that is, in a wheel 5 in. broad the radius of the
outer edge is ¼ in. less than that of the inner; and the rails are
placed sloping a little inwards. The effect of this conical figure is to
counteract any tendency to roll off the rails; for if a pair of wheels
were shifted a little to one side, the parts of the tires rolling upon
the rails being then of unequal circumference, would cause the wheels to
roll towards the other side. The conical shape produces this kind of
adjustment so well that the flanges do not in general touch the rails.
They act, however, as safeguards in passing over curves and junctions.
In curves the outer line of rails is laid higher than the inner, so that
in passing over them the train leans slightly inwards, in order to
counteract what is called the centrifugal force, to which any body
moving in a curve is subject. This so-called force is merely the result
of that tendency which every moving body has to continue its motion in a
straight line. A very good example of the effect of this may be seen
when a circus horse is going rapidly round the ring. The inclination
inwards is still more perceptible when a rider is standing on the
horse’s back, as shown in Fig. 46. The earth’s attraction of gravity is
pulling the performer straight down, and the centrifugal force would of
itself throw her outwards horizontally. The resultant or combined effect
of both acts is seen in the exact direction in which she is leaning, and
it presses her feet on the horse’s back, the animal itself being under
similar conditions. It is obvious that the amount of centrifugal force,
and therefore of inward slope, will increase with the speed and
sharpness of the curve, and on the railways the rails are placed so that
the slope counteracts the centrifugal force when the train travels at
about the rate of twenty miles per hour.

[Illustration:

  FIG. 47.—_Points._
]

A very important part of the mechanism of a railway is the mode of
passing trains from one line of rails to another. Engines and single
carriages are sometimes transferred by means of _turn-tables_, but the
more general plan is by _switches_, which are commonly constructed as
shown in Fig. 47. There are two rails, A and B, tapering to a point and
fixed at the other end, so that they have sufficient freedom to turn
horizontally. A train passing in the direction shown by the arrow would
continue on the main line, if the points are placed as represented; but
if they be moved so that the _long tongue_ is brought into contact with
the rail of the main line, then the train would run on to the side
rails. These _points_ are worked by means of a lever attached to the
rod, C, the lever being either placed near the rails, or in a
_signal-box_, where a man is stationed, whose sole duty it is to attend
to the points and to the signals. The interior of a signal-box near an
important junction or station is shown in Fig. 48, and we see here the
numerous levers for working the points and the signals, each of these
having a connection, by rods or wires, with the corresponding point or
signal-post. The electric telegraph is now an important agent in railway
signalling, and in a signal-box we may see the bells and instruments
which inform the pointsman whether a certain section of the line is
“blocked” or “clear.” The signals now generally used on British railways
are made by the semaphore, which is simply a post from which an arm can
be made to project. When the driver of the train sees the arm projecting
from the left-hand side of the post, it is an intimation to him that he
must stop his train; when the arm is dropped half-way, so as to project
45° from the post, it is meant that he must proceed cautiously; when the
arm is down the line is clear. These signals, of course, are not capable
of being seen at night, when their place is supplied with lamps,
provided with coloured glasses—red and green—and also with an uncoloured
glass. The lamp may have the different glasses on three different sides,
and be turned round so as to present the required colour; or it may be
made to do so without turning, if provided with a frame having red and
green glasses, which can be moved like spectacles in front of it. The
meanings of the various coloured lights and the corresponding semaphore
signals are these:

                  | White _All right_ Go on.
                  ↿ Green _Caution_   Proceed slowly.
                  ┓ Red   _Danger_    Stop.

[Illustration:

  FIG. 48.—_Signal-box on the North London Railway._
]

A very clear account of the mode of working railway signals on what is
now called the _block system_, together with a graphic description of a
signal-box, was given in a paper which appeared some years ago in “The
Popular Science Review,” from the pen of Mr. Charles V. Walker, F.R.S.,
the telegraph engineer to the South-Eastern Railway Company, who was the
first to organize an efficient system of electric signalling for
railways. We may remark that the signalling instruments on the
South-Eastern line, and indeed on all the lines at the present day,
address themselves both to the ear and to the eye, for they consist
of—first, bells, on which one, two, or more blows are struck, each
series of blows having its own particular meaning; and, second, of a
kind of miniature signal-post, with arms capable of being moved by
electric currents into positions similar to those of the arm of an
actual signal-post, so that the position of the arms is made always to
indicate the state of the line. One arm of the little signal-post—the
left—is red, and it has reference to _receding_ trains; the other—viz.,
the right—arm is white, and relates to _approaching_ trains. Mr. Walker
thus describes the signalling:

“The ordinary position of the arms of the electro-magnetic telegraph
semaphores will be down; that is to say, when the line is clear of all
trains, and business begins, say in early morning, all the arms will be
down, indicating that no train is moving. When the first train is ready
to start, say from Charing Cross, the signalman will give the proper
bell-signal to Belvidere—two, three, or four blows, according as the
train is for Greenwich, for North Kent, or Mid-Kent, or for the main
line; and the Belvidere man will acknowledge this by one blow on the
bell in reply, and without raising the Charing Cross red or left arm.
This is the signal that the train may go on; and when the train has
passed, so that the Charing Cross man can see the tail lights, he gives
the out signal a second time, which the Belvidere man acknowledges, at
the same time raising the red arm at Charing Cross, behind the train,
and so protecting it until it has passed him at Belvidere, when he
signals to that effect to Charing Cross, at the same time putting down
the red arm there, as an indication that the line is again clear. While
these operations are going on for down trains, others precisely similar,
but in the reverse direction, are going on for up trains.... One and the
same pressure on the key sends a bell signal and raises or depresses the
semaphore arm as the case may require, a single telegraph wire only
being required for the combined system, as for the more simple bell
system.” In one of the signal-boxes on the South-Eastern line, Mr.
Walker states, on a certain day 650 trains or engines were signalled and
all particulars accurately entered in a book, the entries requiring the
writing down of nearly 8,000 figures: an illustration of the amount of
work quietly carried on in a signal-box for the advantage and security
of the travelling public.

Mr. Walker also gives us a peep into the inside of one of the
signal-boxes, thus: “The interior of a large signal-box exhibits a very
animated scene, in which there are but two actors, a man and a boy, both
as busy as bees, but with no hurry or bustle. The ruling genius of the
place is the strong, active, intelligent signalman, standing at one end
of the apartment, the monarch for the time being of all he surveys.
Immediately before him in one long line, extending from side to side, is
a goodly array of levers, bright and clean from constant use and careful
tending, each one labelled for its respective duty. Before him to the
right and left are the various electro-magnetic semaphores, each one in
full view and adjusted in position to the pair of roads to which it is
appropriated, and all furnished with porcelain labels. Directly in front
of him is a screen, along which are arranged the various semaphore keys;
and on brackets, discreetly distributed, are the bells and gongs, the
twin companions each of its own semaphore. Before the screen are the
writing-desk and books, and here stands the youngster, the ministering
spirit, all on the alert to take or to send electric signals and to
record them, his time and attention being devoted alternately to his
semaphore keys and to his books, being immediately under the eye and
control of the signalman. This is no place for visitors, and the scenes
enacted here have little chance of meeting the public gaze; indeed, the
officers whose duties take them hither occasionally are only too glad to
look on, and say as little as may be, and not interrupt the active pair,
between whom there is evidently a good understanding in the discharge of
duties upon the accurate performance of which so much depends. Looking
on, the man will be seen in command of his rank and file: signals come,
are heard and seen by both man and boy; levers are drawn and withdrawn,
one, two, three, or more; the arms and the lamps on the gigantic masts
outside, of which there are three, well laden, are displayed as
required, distant signals are moved, points are shifted and roads made
ready; telegraph signals are acknowledged; and on looking out—for the
box is glazed throughout—trains are seen moving in accordance with the
signals made; and on the signal-posts at the boxes, right and left—for
here they are within easy reach of each other—arms are seen up and down
in sympathy with those on the spot, and with the telegraph signals that
have been interchanged. There is no cessation to this work, and there is
no confusion in it; one head and hand directs the whole, so that there
are no conflicting interests and no misunderstandings; all is done in
perfect tranquillity, and the great secret is that one thing is done at
a time. All this, which is so simple and so full of meaning to the
expert, is to the uninitiated intricate and vague; and though he cannot
at first even follow the description of the several processes, so
rapidly are they begun and ended, yet, as the cloud becomes thin, and
his ideas become clearer, he cannot fail to be gratified, and to be
filled with admiration at the great results that are brought about by
means so simple.”

[Illustration:

  FIG. 49.—_Post Office Railway Van._
]

Most of the carriages used on railways are so familiar to everyone that
it is unnecessary to give any description of them. We give a figure of
one which, though of early type, has special features of interest, being
the well-designed Travelling Post Office, Fig. 49. In such vans as that
here represented letters are sorted during the journey, and for this
purpose the interior is provided with a counter and with pigeon-holes
from end to end. When the train stops bags may, of course, be removed
from or received into the van in the ordinary manner; but by a simple
mechanism bags may be delivered at a station and others taken up while
the train continues its journey at full speed. A bar can be made to
project from the side of the carriage, and on this the bag is hung by
hooks, which are so contrived that they release the bag when a rod,
projecting from the receiving apparatus, strikes a certain catch on the
van. The bag then drops into a netting, which is spread for its
reception; and in order to receive the bags taken up, a similar netting
is stretched on an iron frame attached to the van This frame is made to
fold up against the side of the carriage when not in use. When the train
is approaching the station where the bag is to be taken up, this frame
is let down, and a projecting portion detaches the bags, so that they
drop into the net, from which they are removed into the interior of the
vehicle. These travelling post offices are lighted with gas, and are
padded at the ends, so that the clerks may not be liable to injury by
concussions of the carriages.

England has had to borrow from the United States not a few hints for
such adaptations and appliances as tend to promote the comfort and
convenience of travellers by rail, especially on what we insularly call
long journeys. Some of these vehicles on the American railways are
luxurious hotels upon wheels; they contain accommodation for forty
persons, having a kitchen, hot and cold water, wine, china and linen
closets, and more than a hundred different articles of food, besides an
ample supply of tablecloths, table napkins, towels, sheets, pillowcases,
&c. Then there are other Pullman inventions, such as the “palace” and
the “sleeping” cars, in which the traveller who is performing a long
journey makes himself at home for days, or perhaps for a week, as, for
instance, while he is being carried across the American continent from
ocean to ocean at the easy rate of twenty miles an hour on the Pacific
and other connecting lines. Mr. C. Nordhoff, an American writer, giving
an account of his journey to the Western States, writes thus: “Having
unpacked your books and unstrapped your wraps in your Pullman or Central
Pacific palace car, you may pursue all the sedentary avocations and
amusements of a parlour at home; and as your housekeeping is done—and
admirably done—for you by alert and experienced servants; as you may lie
down at full length, or sit up, sleep, or wake at your choice; as your
dinner is sure to be abundant, very tolerably cooked, and not hurried;
as you are pretty certain to make acquaintances in the car; and as the
country through which you pass is strange and abounds in curious and
interesting sights, and the air is fresh and exhilarating—you soon fall
into the ways of the voyage; and if you are a tired business man or a
wearied housekeeper, your careless ease will be such a rest as certainly
most busy and overworked Americans know how to enjoy. You write
comfortably at a table in a little room called a ‘drawing-room,’
entirely closed off, if you wish it, from the remainder of the car,
which room contains two large and comfortable armchairs and a sofa, two
broad clean plate-glass windows on each side (which may be doubled if
the weather is cold), hooks in abundance for shawls, hats, &c., and
mirrors at every corner. Books and photographs lie on the table. Your
wife sits at the window sewing and looking out on long ranges of
snow-clad mountains or on boundless ocean-like plains. Children play on
the floor or watch at the windows for the comical prairie dogs sitting
near their holes, and turning laughable somersaults as the car sweeps
by. The porter calls you at any hour you appoint in the morning; he
gives half an hour’s notice of breakfast, dinner, or supper; and while
you are at breakfast, your beds are made up and your room or your
section aired. About eight o’clock in the evening—for, as at sea, you
keep good hours—the porter, in a clean grey uniform, comes in to make up
the beds. The two easy-chairs are turned into a berth; the sofa
undergoes a similar transformation; the table, having its legs pulled
together, disappears in a corner, and two shelves being let down furnish
two other berths. The freshest and whitest of linen and
brightly-coloured blankets complete the outfit; and you undress and go
to bed as you would at home.”

An important general truth may find a familiar illustration in the
subject now under notice. The truth in question may be expressed by
saying that, in all human affairs, as well as in the operations of
nature, the state of things at any one time is the result, by a sort of
growth, of a preceding state of things. And in this way it is certainly
true of inventions, that they never make their appearance suddenly in a
complete and finished state—like Minerva, who is fabled to have sprung
from the brain of Jupiter fully grown and completely armed; but rather
their history resembles the slow and progressive process by which
ordinary mortals attain to their full stature. We have already seen that
railways had their origin in the tramways of collieries; and, in like
manner, the railway carriage grew out of the colliery truck and the
stage coach; for when railway carriages to convey passengers were first
made, it did not occur to their designers that anything better could be
done than to place coach bodies on the frame of the truck; and
accordingly the early railway carriages were formed by mounting the body
of a stage coach, or two or three such bodies side by side, on the
timber framework which was supported by the flanged wheels. The cut,
Fig. 56, is from a painting in the possession of the Connecticut
Historical Society, and it represents the first railway train in America
on its trial trip (1831), in which sixteen persons took part, who were
then thought not a little courageous. Here we see that the carriages
were regular stage coaches, and the same was the case in England. But it
is very significant that, to this day, the stage coach bodies are
traceable in many of the carriages now running on English lines,
especially in the first-class carriages, where, in the curved lines of
the mouldings which are supposed to ornament the outside, one may easily
recognize the forms of the curved bodies of the stage coaches, although
there is nothing whatever, in the real framing of the timbers of the
railway carriage, which has the most distant relation to these curves.
Then again, almost universally on English lines, the old stage coach
door-handles are still retained on the first-class carriages, in the
awkward flat oval plates of brass which fold down with a hinge. Many
other points might be named which would show the persistence of the
stage coach type on the English railways. The cut, Fig. 56, proves that
the Americans set out with the same style of carriages; but North
America, as compared with the Old World, is _par excellence_ the country
of rapid developments, and there carriages, or cars, as our
Transatlantic cousins call them, have for a long time been made with
numerous improvements, and in forms more in harmony with the railway
system, than the conservatism of English ideas, still cleaving to the
stage coach type, permitted to be attempted in this country.

Railway travellers in the United States had long enjoyed the benefit of
comforts and convenience in the appointments of their carriages long
before any change had been effected in the general arrangements of the
vehicles provided by the railway companies in England. It is now indeed
a considerable number of years since this state of things has been
altered in the older country; as all the great lines, following the
example of the Midland Company, who first adopted the Pullman cars, have
constructed luxurious vehicles in which every elegance and comfort are
placed within the reach of the English traveller, and these improvements
are highly appreciated by all who have long journeys to make by day or
night.

The elegance and comfort of the arrangements are almost too obvious to
require description. We see the luxuriously padded chairs, which, by
turning on swivels, permit the traveller to adjust his position
according to his individual wishes, so that he can, with ease, place his
seat either to gaze directly on the passing landscape, or turn his face
towards his fellow-travellers opposite or on either side. The chairs are
also provided with an arrangement for placing the backs at any required
inclination, and the light and refined character of the decorations of
the carriage should not escape the reader’s notice. Pullman Cars of
another kind, providing sleeping accommodation for night journeys, are
also in use on the Midland line, and they are fitted up with the same
thoughtful regard to comfort as the Parlour Car.

The great engineering feats which have been accomplished in the
construction of railways are numerous enough to fill volumes. We give,
therefore, only a short notice of one or two recently constructed lines
which have features of special interest, concluding with a brief account
of such remarkable constructions as the railway by which the traveller
may now go up the Rigi, and the railways which ascend Vesuvius and Mt.
Pilatus.


                      _THE METROPOLITAN RAILWAYS._

When the traffic in the streets of London became so great that the
ordinary thoroughfares were unable to meet public requirements, the bold
project was conceived of making a railway under the streets. The
construction of a line of railway beneath the streets of a populous
city, amidst a labyrinth of gas-pipes, water-mains, sewers, &c., is
obviously an undertaking presenting features so remarkable that the
London Underground Railway cannot here be passed over without a short
notice. Its construction occupied about three years, and it was opened
for traffic in 1863. The line commencing at Paddington, and passing
beneath Edgware Road at right angles, reaches Marylebone Road, under the
centre of which it proceeds, and passing beneath the houses at one end
of Park Crescent, Portland Place, it follows the centre of Euston Road
to King’s Cross, where connection with the Great Northern and Midland
system is effected. Here the line bends sharply southwards, and proceeds
to Farringdon Street Station, the original terminus. A subsequent
extension takes an easterly direction and reaches Aldgate Station, the
nominal terminus. The crown of the arch which covers the line is in some
places only a few inches beneath the level of the streets; in other
places it is several feet below the surface, and, in fact, beneath the
foundations of the houses and other buildings. The steepest gradient on
the line is 1 in 100, and the sharpest curve has a radius of 200 yards.
The line is nearly all curved, there not being in all its length
three-quarters of a mile of straight rails. The difficulties besetting
an undertaking of this kind would be tedious to describe, but may
readily be imagined. The line traverses every kind of soil—clay, gravel,
sand, rubbish, all loosened by previous excavations for drains, pipes,
foundations, &c.; and the arrangements of these drains, water and
gas-pipes, had to be reconciled with the progress of the railway works,
without their uses being interfered with even for a time. Of the
stations the majority have roofs of the ordinary kind, open to the sky;
but two of them, namely, Baker Street and Gower Street, are completely
underground stations, and their roofs are formed by the arches of
brickwork immediately below the streets. The arrangements at these
stations show great boldness and inventiveness of design. The booking
offices for the up line are on one side of the road, and those for the
down line on the other. Fig. 50 represents the interior of the Gower
Street Station, and the other is very similar. In each the platforms are
325 ft. long and 10 ft. broad, and the stations are lighted by lateral
openings through the springing of the arch which forms the roof. This
arch is a portion of a circle of 32 ft. radius, with a span of 45 ft.
and a rise of 9 ft. at the crown. The lateral openings are arched at the
top and bottom, but the sides are flat. The width of each is 4 ft. 9
in., and the height outside 6 ft., increasing to 10 ft. at the ends
opening on the platform. The openings are entirely lined with white
glazed tiles, and the outward ends open into an area, the back of which
is inclined at an angle of 45°, and the whole also lined with white
glazed tiles, and covered with glass, except where some iron gratings
are provided for ventilation. The tiles reflect the daylight so
powerfully that but little gas is required for the illumination of the
station in the day-time. The arched roofs of these stations are
supported by piers of brickwork, 10 ft. apart, 5 ft. 6 in. deep, and 3
ft. 9 in. wide. In the spaces between the piers vertical arches, like
parts of the brick lining of a well, are wedged in, to resist the thrust
of the earth, and a straight wall is built inside of this between the
piers, to form the platform wall of the station. The tops of the piers
are connected by arches, and are thus made to bear the weight of the
arched roof, which has 2 ft. 3 in. thickness of brickwork at the crown,
and a much greater thickness towards the haunches.

[Illustration:

  FIG. 50.—_Gower Street Station, Metropolitan Railway._
]

The benefit derived by the public from the completion of the
Metropolitan Railway was greatly increased by the subsequent
construction of another railway—“The Metropolitan District,” which,
joining the Metropolitan at Paddington, makes a circuit about the
west-end of Hyde Park, and passing close to the Victoria Terminus of the
London, Chatham, and Dover and the Brighton and South Coast Railways,
reaches Westminster Bridge, and then follows the Thames Embankment to
Blackfriars Bridge, where it leaves the bank of the river for the
Mansion House, Mark Lane and Aldgate stations. This line, taken in
conjunction with the Metropolitan, forms the “_inner circle_” of the
railway communication in London. The circuit was for a long time
incomplete at the east by the want of connection between the Mansion
House Station and that of Moorgate Street, although these stations are
but little more than half a mile apart. A line connecting these two
points has lately been constructed at great cost, and the public now
possess a complete circle of communication. The number of trains each
day entering and leaving some of the stations on the Metropolitan system
is very great. Moorgate Street Station—a terminus into which several
companies run—may have about 800 trains arriving or departing in the
course of a day.


                         _THE PACIFIC RAILWAY._

The remarkable development of railways which has taken place in the
United States has its most striking illustration in the great system of
lines by which the whole continent can be traversed from shore to shore.
The distance by rail from New York to San Francisco is 3,215 miles, and
the journey occupies about a week, the trains travelling night and day.
The traveller proceeding from the Eastern States to the far west has the
choice of many routes, but these all converge to Omaha. From this point
the Pacific Railroad will convey him towards the land of the setting
sun. The map, Fig. 51, shows the course of this railway, which is the
longest in the world. It traverses broader plains and crosses higher
mountains than any other. Engineering skill of the most admirable kind
has been displayed in the laying-out and in the construction of the
line, with its innumerable cuttings, bridges, tunnels, and snow-sheds.

[Illustration:

  FIG. 51.—_Map of the Route of the Pacific Railway._
]

The road from Omaha to Ogden, near the Great Salt Lake—a distance of
1,032 miles—is owned by the Union Pacific Company, and the Central
Pacific joins the former at Ogden and completes the communication to San
Francisco, a further length of 889 miles—the whole distance from Omaha
to San Francisco being 1,911 miles. The Union Pacific was commenced in
November, 1865, and completed in May, 1869. There are at Omaha extensive
workshops provided with all the appliances for constructing and
repairing locomotives and carriages, and these works cover 30 acres of
ground, and give employment to several thousand men. The population of
Omaha rose during the making of the railway from under 3,000 in 1864 to
more than 16,000 in 1870, and it is now a flourishing town. A little
distance from Omaha the line approaches the Platte River, and the valley
of this river and one of its tributaries is ascended to Cheyenne, 516
miles from Omaha, the line being nowhere very far from the river’s
course. Cheyenne is 5,075 ft. higher above the sea than Omaha, the
elevation of which is 966 ft. The Platte River is a broad but very
shallow stream, with a channel continually shifting, owing to the vast
quantity of sand which its muddy waters carry down. This portion of the
line passing through a district where leagues upon leagues of fertile
land await the hand of the tiller, has opened up vast tracts of
land—hedgeless, gateless green fields, free to all, and capable of
receiving and supporting millions of human inhabitants. Cheyenne, a town
of 3,000 inhabitants, is entirely the creation of the railways, for
southward from Cheyenne a railway passes to Denver, a distance of 106
miles, through rich farming and grazing districts. Seven miles beyond
Cheyenne the line begins to ascend the Black Hills by steep gradients,
and at Granite Canyon, for example, the rise in five miles is 574 ft.,
or about 121 ft. per mile. Many lime-kilns have been erected in this
neighbourhood, where limestone is very abundant. A little beyond this
point the road is in many places protected by snow-sheds, fences of
timber, and rude stonework. At Sherman, 549 miles from Omaha, the line
attains the summit of its track over the Black Hills, and the highest
point on any railway in the world, being 8,242 ft. above the level of
the sea. Wild and desolate scenery characterizes the district round
Sherman, and the hills, in places covered with a dense growth of wood,
will furnish an immense supply of timber for years to come. The
timber-sheds erected over the line, and the fences beside it are not so
much on account of the depth of snow that falls, but to prevent it from
blocking the line by being drifted into the cuts by the high wind. A few
miles beyond Dale Creek at Sherman is the largest bridge on the line. It
is a trestle bridge, 650 ft. long and 126 ft. high, and has a very light
appearance—indeed, to an English eye unaccustomed to these _impromptu_
timber structures, it looks unpleasantly light. From Sherman the line
descends to Laramie, which is 7,123 ft. above the sea level and 24 miles
from Sherman, and here the railway has a workshop, for good coal is
found within a few miles. A fine tract of grazing land, 60 miles long
and 20 miles broad, stretches around this station, and it is said that
nowhere in the whole North American continent can cattle be reared and
fattened more cheaply. The line, now descending the Black Hills, crosses
for many miles a long stretch of rolling prairie, covered in great part
with sage-bush, and forming a tableland lying between the western base
of the Black Hills and the eastern base of the snowy range of the Rocky
Mountains, which latter reach an elevation of from 10,000 to 17,000 ft.
above the sea level and are perpetually covered with snow. Such
tablelands are termed in America “parks.” Before the line reaches the
summit of the pass by which it crosses the range of the snowy mountains,
it traverses some rough country among the spurs of the hills—through
deep cuts and under snow-sheds, across ravines and rivers, and through
tunnels. At Percy, 669 miles, is a station named after Colonel Percy,
who was killed here by the Indians when surveying for the line. He was
surprised by a party of the red men, and retreated to a cabin, where he
withstood the attack of his assailants for three days, killing several
of them; but at length they set fire to the cabin, and the unfortunate
Colonel rushing out, fell a victim to their ferocity. Near Creston, 737
miles from Omaha, the highest point of the chief range is reached,
though at an elevation lower by 1,212 ft. than the summit of the pass
where the line crosses the Black Hills, which are the advanced guard of
the Rocky Mountains. Here is the water-shed of the continent, for all
streams rising to the east of this flow ultimately into the
Atlantic,—while these, having their sources in the west, fall into the
Pacific. Before reaching Ogden the line passes through some grand
gorges, which open a way for the iron horse through the very hearts of
the mountains, as if Nature had foreseen railways and providently formed
gigantic cuttings—such as the Echo and Weber Canyons, which enable the
line to traverse the Wahsatch Mountains.

[Illustration:

  FIG. 52.—_Trestle Bridge._
]

Echo Canyon is a ravine 7 miles long, about half a mile broad, flanked
by precipitous cliffs, from 300 to 800 ft. high, and presenting a
succession of wild and grand scenery. In Weber Canyon the river foams
and rushes along between the mountains, which rise in massive grandeur
on either side, plunging and eddying among the huge masses of rock
fallen from the cliffs above. Along a part of the chasm the railway is
cut in the side of the steep mountain, descending directly to the bed of
the stream. Where the road could not be carried round or over the spurs
of the mountains it passes through tunnels, often cut through solid
stone. A few miles farther the line reaches the city of Ogden, in the
state of Utah, the territory of the Mormons. This territory contains
upwards of 65,000 square miles, and though the land is not naturally
productive, it has, by irrigation, been brought into a high state of
cultivation, and it abounds in valuable minerals, so that it now
supports a population of 80,000 persons.

[Illustration:

  FIG. 53.—_American Canyon._
]

We have now arrived at Ogden, where the western portion of the great
railway line connecting the two oceans unites to the Union Pacific we
have just described. This western portion is known as the Central
Pacific Railroad, and it stretches from Ogden to San Francisco, a
distance of 882 miles.

The portion of the line which unites Sacramento to Ogden, 743 miles, was
commenced in 1863 and finished in 1869, but nearly half of the entire
length was constructed in 1868, and about 50 miles west of Ogden, the
remarkable engineering feat of laying 10 miles of railway in one day was
performed. It was thus accomplished: when the waggon loaded with the
rails arrived at the end of the track, the two outer rails were seized,
hauled forward off the car, and laid upon the sleepers by four men, who
attended to this duty only. The waggon was pushed forwards over these
rails, and the process of putting down the rails was repeated, while
behind the waggon came a little army of men, who drove in the spikes and
screwed on the fish-plates, and, lastly, a large number of Chinese
workmen, with pickaxes and spades, who ballasted the line. The average
rate at which these operations proceeded was about 240 ft. of track in
77½ seconds, and in these 10 miles of railway there were 2,585,000
cross-ties, 3,520 iron rails, 55,000 spikes, 7,040 fish-plates, and
14,080 bolts with screws, the whole weighing 4,362,000 lbs.! Four
thousand men and hundreds of waggons were required, but in the 10 miles
all the rails were laid by the same eight men, each of whom is said to
have that day walked 10 miles and lifted 1,000 tons of iron rails.
Nothing but the practice acquired during the four previous years and the
most excellent arrangement and discipline could have made the
performance of such a feat possible as the laying of eight miles of the
track in six hours, which was the victory achieved by these stalwart
navvies before dinner.

The line crosses the great American desert, distinguished for its
desolate aspect and barren soil, and so thickly strewn with alkaline
dust that it appears almost like a snow-covered plain. The alkali is
caustic, and where it abounds no vegetation can exist, most of the
surface of this waste being fine, hard grey sand, mixed with the
fragments of marine shells and beds of alkali.

The third great mountain range of the North American continent is
crossed by this line, at an elevation of 7,043 ft. above the sea level.
The Sierra Nevada, as the name implies, is a range of rugged wild broken
mountain-tops, always covered with snow. The more exposed portions of
the road are covered with snow-sheds, solidly constructed of pine wood
posts, 16 in. or 20 in. across: the total length of snow-sheds on the
Sierra Nevada may equal 50 miles. These sheds sometimes take fire; but
the company have a locomotive at the Summit Station, ready to start at a
moment’s notice with cars carrying tanks of water. The snow falls there
sometimes to a depth of 20 ft. in one winter; and in spring, when it
falls into the valleys in avalanches, sweeping down the mountain-sides,
they pass harmlessly over the sloping roofs of the snow-sheds. Where the
line passes along the steep flank of a mountain, the roofs of these
snow-sheds abut against the mountain-side, so that the masses of snow,
gliding down from its heights, continue their slide without injury to
line, or sheds, or trains. Where, however, the line lies on level
ground, or in a ridge, the snow-sheds are built with a strong roof of
double slope, in order to support or throw off the snow. From Summit
(7,017 ft.) the line descends continuously to Sacramento, which is only
30 ft. above the sea level, and 104 miles from Summit. About 36 miles
from Summit, the great American Canyon, one of the wildest gorges in the
Sierra Nevada range, is passed. Here the American River is confined for
a length of two miles between precipitous walls of rock, 2,000 ft. in
height, and so steep that no human foot has ever yet followed the stream
through this tremendous gorge (Fig. 53). A few miles beyond this the
line is carried, by a daring feat of engineering, along the side of a
mountain, overhanging a stream 2,500 ft. below. This mountain is known
as “Cape Horn,” and is a place to try the nerves of timid people. When
this portion of the line was commenced, the workmen were lowered and
held by ropes, until they had hewn out a standing-place on the shelving
sides of the precipice, along whose dizzy height, where even the agile
Indian was unable to plant his foot, the science of the white man thus
made for his iron horse a secure and direct road. (Fig. 54.)

[Illustration:

  FIG. 54.—“_Cape Horn._”
]

[Illustration:

  FIG. 55.—_Snow Plough._
]

These lines of railway, connecting Omaha with Sacramento, are remarkable
evidences of the energy and spirit which characterize the Anglo-Saxon
race in America. The men who conceived the design of the Central Pacific
Railroad, and actually carried it into effect, were not persons
experienced in railway construction; but five middle-aged traders of
Sacramento, two of whom where drapers, one a wholesale grocer, and the
others ironmongers, believing that such a railway should be made, and
finding no one ready to undertake it, united together, projected the
railway, got it completed, and now manage it. These gentlemen were
associated with an engineer named Judah, who was a sanguine advocate of
the scheme, and made the preliminary surveys, if he did not plan the
line. The line is considered one of the best appointed and best managed
in the States; yet the project was at first ridiculed and pronounced
impracticable by engineers of high repute, opposed by capitalists, and
denounced by politicians. An eminent banker, who personally regarded the
scheme with hopefulness, would not venture, however, to take any stock,
lest the credit of his bank should be shaken, were he known to be
connected with so wild a scheme. And, indeed, the difficulties appeared
great. Except wood, all the materials required, the iron rails, the
pickaxes and spades, the waggons, the locomotives, and the machinery had
to be sent by sea from New York, round Cape Horn, a long and perilous
voyage of nine months duration, and transhipped at San Francisco for
another voyage of 120 miles before they could reach Sacramento. Add to
this that workmen were so scarce in California, and wages so high, that
to carry on the work it was necessary to obtain men from New York; and
during its progress 10,000 Chinamen were brought across the Pacific, to
work as labourers. Subscriptions came in very slowly, and before 30
miles of the line had been constructed, the price of iron rose in a very
short time to nearly three times its former amount. At this critical
juncture, the five merchants decided to defray, out of their own private
fortunes, the cost of keeping 800 men at work on the line for a whole
year. We cannot but admire the unswerving confidence in their enterprise
displayed by these five country merchants, unskilled in railway making,
unaided by public support, and even discouraged in their project by
their own friends. The financial and legal obstacles they successfully
surmounted were not the only difficulties to be overcome. They had the
engineering difficulties of carrying their line over the steep Sierra, a
work of four years; long tunnels had to be bored; one spring when snow
60 ft. in depth covered the track, it had to be removed by the shovel
for 7 miles along the road; saw-mills had to be erected in the
mountains, to prepare the sleepers and other timber work; wood and water
had to be carried 40 miles across alkali plains, and locomotives and
rails dragged over the mountains by teams of oxen. The chief engineer,
who organized the force of labourers, laid out the road, designed the
necessary structures, and successfully grappled with the novel problem
of running trains over such a line in all seasons, was Mr. S. S.
Montague. The requirements of the traffic necessitate not only solidly
constructed iron-covered snow-sheds, but massive snow-ploughs to throw
off the track the deep snow which could in no other way be prevented
from interrupting the working of the line. These snow-ploughs are
sometimes urged forward with the united power of eight heavy
locomotives. Fig. 55 represents one of these ploughs cleaning the line,
by throwing off the snow on to the sides of the track. The cutting
apparatus varies in its arrangements, some forms being designed to push
the snow off on one side, some on the other, and to fling it down the
precipices; and others, like the one represented, are intended merely to
throw it off the track.

[Illustration:

  FIG. 56.—_The first Steam Railroad Train in America._
]

Sacramento is 1,775 miles from Omaha, and is connected with San
Francisco by a line 139 miles long. At San Francisco, or rather at
Oakland, 1,911 miles from Omaha and 3,212 miles from New York, is the
terminus of the great system of lines connecting the opposite shores of
the vast North American continent. San Francisco, situated on the
western shore of a bay, is connected with Oakland by a ferry; but the
railway company have recently constructed a pier, which carries the
trains out into the bay for 2¼ miles. This pier is strongly built, and
is provided with a double set of rails and a carriage-road, and with
slips at which ships land and embark passengers, so that ships trading
to China, Japan, and Australia can load and unload directly into the
trains, which may pass without change from the shores of the Pacific to
those of the Atlantic Ocean. San Francisco is a marvellous example of
rapid increase, for the population now numbers 170,000, yet a quarter of
a century ago 500 white settlers could not be found in as many miles
around its site. The first house was erected in 1846, and in 1847 not a
ship visited the bay, but now forty large steamships ply regularly,
carrying mails to China, Japan, Panama, South America, Australia, &c.,
and there are, of course, hundreds of other steamers and ships.

The descriptions we have given of only two lines of railway may suffice
to show that the modern engineer is deterred by no obstacles, but boldly
drives his lines through places apparently the most impracticable. He
shrinks from no operations however difficult, nor hesitates to undertake
works the mere magnitude of which would have made our forefathers stand
aghast. Not in England or America alone, but in almost every part of the
world, the railways have extended with wonderful rapidity; the continent
of Europe is embraced by a network of lines; the distant colonies of
Australia and New Zealand have thousands of miles of lines laid down,
and many more in progress; the map of India shows that peninsula
traversed in all directions by the iron roads; and in the far distant
East we hear of Japan having several lines in successful operation, and
the design of laying down more. In connection with such works, at home
and abroad, many constructions of great size and daring have been
designed and erected; many navigable rivers have been bridged, and not
seldom has an arm of the sea itself been spanned; hundreds of miles of
embankments and viaducts have been raised; hills have been pierced with
innumerable cuttings and tunnels, and all these great works have been
accomplished within the experience of a single generation of men, and
have sprung from one single successful achievement of Stephenson’s—the
Liverpool and Manchester Railway, completed and opened in 1830. We in
England should also have pride in remembering that the growth of the
railways here is due to the enterprise, industry, and energy of private
persons; for the State has furnished no funds, but individuals, by
combining their own resources, have executed the works, and manage the
lines for their common interest and the public good. It is said that the
amount of money which has been spent on railways in Great Britain is not
far short of 500 millions of pounds sterling. The greatest railway
company in the United Kingdom is the London and North-Western, which
draws in annual receipts about seven millions of pounds; and the total
receipts of all the railway companies would nearly equal half the
revenue of the State.

[Illustration:

  FIG. 57.—_Railway Embankment near Bath._
]

[Illustration:

  PLATE VI.

  MOUNT WASHINGTON INCLINED TRACK.
]


                          _INCLINED RAILWAYS._

The construction of railways over lofty ranges of mountains will be
found illustrated by the brief notices in other pages of the Union
Pacific line in the United States, and of the St. Gothard railway over
the Alps. In such cases, the track has been to a great extent carried
over the spurs or along the sides of the mountains, so that such
inclines might be obtained as the ordinary locomotive was capable of
ascending. The expensive operation of tunnelling was resorted to only
where sinuous deviations from the more direct route involved a still
greater expenditure of initial cost, or a continual waste of time and
energy in the actual working of the line. Sometimes winding tracks,
almost returning by snake-like loops on their own route, as projected on
the map, were required in order that the ascent could be made with an
incline practicable for the ordinary locomotive. In the earlier
development of railways, there were to be met with cable inclines, where
the traction of the locomotive had to be superseded or supplemented by
that of a rope or chain wound round a drum actuated by a stationary
steam-engine. The more powerful locomotives of the present day are able
to mount grades of such inclination that the employment of cable
traction is no longer requisite, except in but a few cases. Railways had
carried passengers about in all parts of the world for many years before
the engineer addressed himself to the problem of easily and quickly
taking people up heights of steep and toilsome ascent, sought generally
for the sake of the prospect, etc. Such, at least, has been the object
of most of the inclined railways already constructed, but to this their
utility is by no means limited, and as their safety and stability has
been proved by many years of use, they may find wider applications than
the gratification of the tourist and pleasure-seeker.

The toothed rail or rack which was formerly supposed necessary to obtain
power of traction on rails has been already mentioned (p. 101), and as
early as 1812 such a contrivance appears to have been in use in England,
near Leeds, the invention of a Mr. Blenkinsop. This mode of traction
received no development or improvement worthy of notice until Mr. S.
Marsh constructed, in 1866, a railway ladder—for so it may be called—for
the ascent of Mount Washington in the United States. In this case there
was a centre rail formed of iron, angle iron laid between and parallel
to the metals on which ran the wheels of the carriages. In this centre
rail angle irons were connected by round bars of wrought iron, which the
teeth of a pinion of the locomotive engaged, so that a climbing action,
resembling somewhat that of a wheel entering on the successive rounds of
a ladder, was produced, and in this way an ascensive power was obtained
sufficient to overcome gravity, the gradient not much exceeding a rise
of one foot in three at any point (12 vertical to 32 horizontal). This
railway was completed in 1869, and for more than a quarter of a century
it has carried thousands of tourists to the summit of Mount Washington
without a single fatal accident. This system of ascending mountains was
soon adopted in Europe with certain improvements, for in 1870 an
inclined railway was constructed to the summit of the Rigi, in which a
system of involute gearing was substituted for the ladder-like rounds of
Mr. Marsh. A certain vibratory action, due to the successive engagements
of the teeth in the central rack, which was somewhat disagreeable for
passengers, was soon afterwards obviated in the Abt system, in which two
racks are used, with the teeth of one opposite the spaces of the other,
and a double pinion provided, so that greater uniformity in the acting
power is obtained. With certain modifications in detail, such as
horizontal instead of vertical pinions, this system has been largely
adopted wherever cables have been dispensed with. In the inclined
railway by which Mount Pilatus, near Lucerne, is now ascended,
horizontal teeth project from both sides of a centre rail, and these are
engaged by horizontal pinions. The incline here is very steep, being in
places nearly 30 degrees; teeth perpendicular to the plane of the
incline would have offered a less margin of safety than those on the
plan actually adopted. In some places, as among the Alps, and more
particularly in South America, there are railways in which the ordinary
mode of traction and that with the rack are combined; that is, where the
gradient exceeds the ordinary limit, a central rack-rail is laid down,
on approaching which the engineer slackens his speed, and allows
pinions, moved by the locomotive, to become engaged in the double rack,
by which he slowly climbs the steep ascent until a level tract is
reached which permits of the ordinary traction being resumed.

[Illustration:

  FIG. 57_a_.—_Train Ascending the Rigi._
]

Instead of climbing the inclines by rack-work rails, there is another
system which offers great advantages for economy in working, and one
generally resorted to where the incline can be made in one vertical
plane. This is the balanced cable, in which the gravitation force of a
descending car or train is utilised to draw up, or assist to draw up,
the ascending car or train. These cars are attached to the ends of a
cable which passes round a drum at the top of the incline, and means are
provided, according to circumstances, so that the drum may be turned, or
its revolutions controlled by brakes. When there is a water supply at
the upper end of the incline, a simple and economical mode of working
the cable is available; for all that is necessary is to provide each car
with a water-tank capable of being rapidly filled and emptied. The upper
car is made the heavier when required, by filling its tank with water,
when it raises the lower car, and on itself arriving at the bottom, the
water is discharged before the load to be taken up is received.

[Illustration:

  FIG. 57_b_.—_At the Summit of the Rigi._
]

Many inclined railways are now in operation in various parts of the
world, as at Mount Vesuvius, where two of the slopes have a combined
length of 10,500 feet; at Mount Supurga and at Mount San Salvatore there
are others. At Burgen-stock in Switzerland there is one having a slope
57 feet vertical to 100 feet horizontal. These are cable inclines; but a
rack is also used with a pinion regulated by a friction-brake to avoid
accident, in case of the cable parting. The largest inclined railway in
America is at the Catskill Mountains, where an ascent of 1,600 feet is
made in a horizontal distance of 6,780 feet. In this a novel plan has
been adopted for compensating the varying weight that has to be moved,
for it is obvious that at the commencement the load at the top of the
incline has to raise not only that at the bottom, but the whole weight
of the cable also, equal to 35,000 pounds of wire rope, and again after
the middle point has been passed, the descending power is constantly
increasing, while the load being raised is diminishing. Now, in order
that the engine may work with more uniform effect, the engineer has not
made the incline a straight line, but with the slope lightest at the
bottom and gradually increased towards the top, so that the line is
really a curve in the vertical plane, and has at every point just the
inclination required for balancing the weight of the wire cable, as this
shifts from the one track to the other. Instead of a rack pinion and
brake to control a too rapid descent from any accident, the cars are
provided with clutches, which are automatically thrown out on wooden
guard-rails, when a safe speed is exceeded. Inclined railways have also
been constructed to the summit of Snowdon, in North Wales, and to that
of the Jungfrau, in Switzerland.

[Illustration]

[Illustration:

  PLATE VII.

  PIKE’S PEAK RAILWAY, ROCKY MOUNTAINS.
]

[Illustration:

  FIG. 58.—_The Great Eastern at Anchor._
]



                           STEAM NAVIGATION.


The first practically successful steamboat was constructed by Symington,
and used on the Forth and Clyde Canal in 1802. A few years afterwards
Fulton established steam navigation in American waters, where a number
of steamboats plied regularly for some years before the invention had
received a corresponding development in England, for it was not until
1814 that a steam-packet ran for hire in the Thames. From that time,
however, the principle was quickly and extensively applied, and steamers
made their appearance on the chief rivers of Great Britain, and soon
began also to make regular passages from one sea-port to another, until
at length, in 1819, a steamer made the voyage from New York to
Liverpool. It does not appear, however, that such ocean steam voyages
became at once common, for we read that in 1825 the captain of the first
steam-ship which made the voyage to India was rewarded by a large sum of
money. It was not until 1838 that regular steam communication with
America was commenced by the dispatch of the _Great Western_ from
Bristol. Other large steamers were soon built expressly for the passage
of the Atlantic, and a new era in steam navigation was reached when, in
1845, the _Great Britain_ made her first voyage to New York in fourteen
days. This ship was of immense size, compared with her predecessors, her
length being 320 ft., and she was moreover made of iron, while instead
of paddles, she was provided with a screw-propeller, both circumstances
at that time novelties in passenger ships. Fulton appears to have made
trial in America of various forms of mechanism for propelling ships
through the water. Among other plans he tried the screw, but finally
decided in favour of paddle-wheels, and for a long time these were
universally adopted. Many ships of war were built with paddle-wheels,
but the advantages of the screw-propeller were at length perceived. The
paddle-wheels could easily be disabled by an enemy’s shot, and the large
paddle-boxes encumbered the decks and obstructed the operations of naval
warfare. Another circumstance perhaps had a greater share in the general
adoption of the screw, which had long before been proposed as a means of
applying steam power to the propulsion of vessels. This was the
introduction of a new method of placing the screw, so that its powers
were used to greater advantage. Mr. J. P. Smith obtained a patent in
1836 for placing the propeller in that part of the vessel technically
called the _dead-wood_, which is above the keel and immediately in front
of the rudder. When the means of propulsion in a ship of war is so
placed, this vital part is secure from injury by hostile projectiles,
and the decks are clear for training guns and other operations. Thus
placed, the screw has been proved to possess many advantages over
paddle-wheels, so that at the present time it has largely superseded
paddle-wheels in vessels of every class, except perhaps in those
intended to ply on rivers and lakes. Many fine paddle-wheel vessels are
still afloat, but sea-going steamers are nearly always now built with
screw-propellers. In the application of the steam engine to navigation
the machine has received many modifications in the form and arrangement
of the parts, but in principle the marine engine is identical with the
condensing engine already described. The engines in steam-ships are
often remarkable for the great diameter given to the cylinders, which
may be 8 ft. or 9 ft. or more. Of course other parts of the machinery
are of corresponding dimensions. Such large cylinders require the
exercise of great skill in their construction, for they must be cast in
one piece and without flaws. The engraving, Fig. 59, depicts the scene
presented at the works of Messrs. Penn during the casting of one of
these large cylinders, the weight of which may amount to perhaps 30
tons. Only the top of the mould is visible, and the molten iron is being
poured in from huge ladles, moved by powerful cranes. In paddle vessels
the great wrought iron shaft which carries the paddle-wheels crosses the
vessel from side to side. This shaft has two cranks, placed at right
angles to each, and each one is turned by an engine, which is very
commonly of the kind known as the side-lever engine. In this engine,
instead of a beam being placed above the cylinder, two beams are used,
one being set on each side of the cylinder, as low down as possible. The
top of the piston-rod is attached to a crosshead, from each end of which
hangs a great rod, which is hinged to the end of the side-beam. The
other ends of the two beams are united by a cross-bar, to which is
attached the connecting-rod that gives motion to the crank. Another
favourite form of engine for steam-ships is that with oscillating
cylinders. The paddle-wheels are constructed with an iron framework, to
which flat boards, or floats, are attached, placed usually in a radial
direction. But when thus fixed, each float enters the water obliquely,
and in fact its surface is perpendicular to the direction of the
vessel’s course only at the instant the float is vertically under the
axis of the wheel. In order to avoid the loss of power consequent upon
this oblique movement of the floats, they are sometimes hung upon
centres, and are so moved by suitable mechanism that they are always in
a nearly vertical position when passing through the water. Paddle-wheels
constructed in this manner are termed _feathering_ wheels. They do not
appear, however, to possess any great advantage over those of the
ordinary construction, except when the paddles are deeply immersed in
the water, and this result may be better understood when we reflect that
the actual path of the floats through the water is not circular, as it
would be if the vessel itself did not move; for all points of the wheel
describe peculiar curves called _cycloids_, which result from the
combination of the circular with the onward movement.

[Illustration:

  PLATE VIII.

  THE “CLERMONT,” FROM A CONTEMPORARY DRAWING.
]

[Illustration:

  FIG. 59.—_Casting Cylinder of a Marine Steam Engine._
]

The next figure, 60, exhibits a very common form of the screw propeller,
and shows the position which it occupies in the ship. The reader may not
at once understand how a comparatively small two-armed wheel revolving
in a plane perpendicular to the direction of the vessel’s motion is able
to propel the vessel forward. In order to understand the action of the
propeller, he should recall to mind the manner in which a screw-nail in
a piece of wood advances by a distance equal to its pitch at every turn.
If he will conceive a gigantic screw-nail to be attached to the vessel
extending along the keel,—and suppose for a moment that the water
surrounding this screw is not able to flow away from it, but that the
screw works through the water as the nail does in the wood,—he will have
no difficulty in understanding that, under such circumstances, if the
screw were made to revolve, it would advance and carry the vessel with
it. The reader may now form an accurate notion of the actual propeller
by supposing the imaginary screw-nail to have the thread so deeply cut
that but little solid core is left in the centre, and supposing also
that only a very short piece of the screw is used—say the length of one
revolution—and that this is placed in the dead-wood. Such was the
construction of the earlier screw-propellers, but now a still shorter
portion of the screw is used; for instead of a complete turn of the
thread, less than one-sixth is now the common construction. Such a strip
or segment of the screw-thread forms a _blade_, and two, three, four, or
more blades are attached radially to one common axis. The blades spring
when there are two from opposite points in the axis, and in other cases
from points on the same circle. The blades of the propeller are cut and
carved into every variety of shape according to the ideas of the
designer, but the fundamental principle is the same in all the forms. It
need hardly be said that the particles of the water are by no means
fixed like those of the wood in which a screw advances. But as the water
is not put in motion by the screw without offering some resistance by
reason of its inertia, this resistance reacting on the screw operates in
the same manner, but not to the same extent, as the wood in the other
case. When we know the pitch of the screw, we can calculate what
distance the screw would be moved forward in a given number of
revolutions if it were working through a solid. This distance is usually
greater than the actual distance the ship is propelled, but in some
cases the vessel is urged through the water with a greater velocity than
if the screw were working in a solid nut. The shaft which carries the
screw extends from the stem to the centre of the ship where the engines
are placed, and it passes outward through a bearing lined with wood, of
which _lignum vitæ_ is found to be the best kind, the lubricant for this
bearing being not oil but water. The screw would not have met with the
success it has attained but for this simple contrivance; for it was
found that with brass bearings a violent thumping action was soon
produced by the rapid rotation of the screw. The wearing action between
the wood and the iron is very slight, whereas brass bearings in this
position quickly wear and their adjustments become impaired. The
screw-shaft is very massive and is made in several lengths, which are
supported in appropriate bearings; there is also a special arrangement
for receiving the thrust of the shaft, for it is by this thrust received
from the screw that the vessel is propelled, and the strain must be
distributed to some strong part of the ship’s frame. There is usually
also an arrangement by which the screw-shaft can, when required, be
disconnected from the engine, in order to allow the screw to turn freely
by the action of the water when the vessel is under sail alone.

[Illustration:

  FIG. 60.—_Screw Propeller._
]

A screw-propeller has one important advantage over paddle-wheels in the
following particular: whereas the paddle-wheels act with the best effect
when the wheel is immersed in the water to the depth of the lowest
float, the efficiency of the screw when properly placed is not
practically altered by the depth of immersion. As the coals with which a
steamer starts for a long voyage are consumed, the immersion is
decreased—hence the paddle-wheels of such a steamer can never be
immersed to the proper extent _throughout_ the voyage; they will be
acting at a disadvantage during the greater part of the voyage. Again,
even when the immersion of the vessel is such as to give the best
advantage to the paddle-wheels, that advantage is lost whenever a
side-wind inclines the ship to one side, or whenever by the action of
the waves the immersion of the paddles is changed by excess or defect.
From all such causes of inefficiency arising from the position of the
vessel the screw-propeller is free. The reader will now understand why
paddle-wheel steamers are at the present day constructed for inland
waters only.

A great impulse was given to steam navigation, by the substitution of
iron for wood in the construction of ships. The weight of an iron ship
is only two-thirds that of a wooden ship of the same size. It must be
remembered that, though iron is many times heavier than wood, bulk for
bulk, the required strength is obtained by a much less quantity of the
former. A young reader might, perhaps, think that a wooden ship must
float better than an iron one; but the law of floating bodies is, that
the part of the floating body which is below the level of the water,
takes up the space of exactly so much water as would have the same
weight as the floating body, or in fewer words, a floating body
displaces its own _weight_ of water. Thus we see that an iron ship,
being lighter than a wooden one, must have more buoyancy. The use of
iron in ship-building was strenuously advocated by the late Sir W.
Fairbairn, and his practical knowledge of the material gave great
authority to his opinion. He pointed out that the strains to which ships
are exposed are of such a nature, that vessels should be made on much
the same principles as the built-up iron beams or girders of railway
bridges. How successfully these principles have been applied will be
noticed in the case of the _Great Eastern_. This ship, by far the
largest vessel ever built, was designed by Mr. Brunel, and was intended
to carry mails and passengers to India by the long sea route. The
expectations of the promoters were disappointed in regard to the speed
of the vessel, which did not exceed 15 miles an hour; and no sooner had
she gone to sea than she met with a series of accidents, which appear,
for a time, to have destroyed public confidence in the vessel as a
sea-going passenger ship. Some damage and much consternation were
produced on board by the explosion of a steam jacket a few days after
the launch. Then the huge ship encountered a strong gale in Holyhead
Harbour, and afterwards was disabled by a hurricane in the Atlantic, in
which her rudder and paddles were so damaged, that she rolled about for
several days at the mercy of the waves. At New York she ran upon a rock,
and the outer iron plates were stripped off the bottom of the ship for a
length of 80 ft. She was repaired and came home safely; but the
companies which owned her found themselves in financial difficulties,
and the big ship, which had cost half a million sterling, was sold for
only £25,000, or only about one-third of her value as old materials.

The misfortunes of the _Great Eastern_, and its failure as a commercial
speculation in the hands of its first proprietors, have been quoted as
an illustration of the ill luck, if it might be so called, which seems
to have attended several of the great works designed by the Brunels—for
the Thames Tunnel was, commercially, a failure; the Great Western
Railway, with its magnificent embankments, cuttings, and tunnels, has
reverted to the narrow gauge, and therefore the extra expense of the
large scale has been financially thrown away; the Box Tunnel, a more
timid engineer would have avoided; and then there is the _Great
Eastern_. It is, however, equally remarkable that all these have been
glorious and successful achievements as engineering works, and the
scientific merit of their designers remains unimpaired by the merely
accidental circumstance of their not bringing large dividends to their
shareholders. Nor is their value to the world diminished by this
circumstance, for the Brunels showed mankind the way to accomplish
designs which, perhaps, less gifted engineers would never have had the
boldness to propose. The Box Tunnel led the way to other longer and
longer tunnels, culminating in that of Mont Cenis; but for the Thames
Tunnel—once ranked as the eighth wonder of the world—we should probably
not have heard of the English Channel Tunnel—a scheme which appears less
audacious now than the other did then; if no _Great Eastern_ had
existed, we should not now have had an Atlantic Telegraph. Possibly this
huge ship is but the precursor of others still larger, and it is
undoubtedly true that since its construction the ideas of naval
architects have been greatly enlarged, and the tendency is towards
increased size and speed in our steam-ships, whether for peace or war.

[Illustration:

  FIG. 61.—_Section of Great Eastern Amidships._
]

[Illustration:

  FIG. 62.—_The Great Eastern in course of Construction._
]

The accidents which had happened to the ship had not, however,
materially damaged either the hull or the machinery; and the _Great
Eastern_ was refitted, and afterwards employed in a service for which
she had not been designed, but which no other vessel could have
attempted. This was the work of carrying and laying the whole length of
the Atlantic Telegraph Cable of 1865, of which 2,600 miles were shipped
on board in enormous tanks, that with the contents weighed upwards of
5,000 tons. The ship has since been constantly engaged in similar
operations.[1] The _Great Eastern_ is six times the size of our largest
line-of-battle ships, and about seven times as large as the splendid
steamers of the Cunard line, which run between Liverpool and New York.
She has three times the steam power of the largest of these Atlantic
steamers, and could carry twenty times as many passengers, with coal for
forty days’ consumption instead of fifteen. Her length is 692 ft.;
width, 83 ft.; depth, 60 ft.; tonnage, 24,000 tons; draught of water
when unloaded, 20 ft.; when loaded, 30 ft.; and a promenade round her
decks would be a walk of more than a quarter of a mile. The vessel is
built on the cellular plan to 3 ft. above the water-line; that is, there
is an inner and an outer hull, each of iron plates ¾ in. thick, placed 2
ft. 10 in. apart, with ribs every 6 ft., and united by transverse
plates, so that in place of the ribs of wooden ships, the hull is, as it
were, built up of curved cellular beams of wrought iron. The ship is
divided longitudinally by two vertical partitions or bulkheads of
wrought iron, ½ in. thick. These are 350 ft. long and 60 ft. high, and
are crossed at intervals by transverse bulkheads, in such a manner that
the ship is divided into nineteen compartments, of which twelve are
completely water-tight, and the rest nearly so. The diagram (Fig. 61)
represents a transverse section, and shows the cellular construction
below the water-line. The strength and safety of the vessel are thus
amply provided for. The latter quality was proved in the accident to the
ship at New York; and the former was shown at the launch, for when the
vessel stuck, and for two months could not be moved, it was found that,
although one-quarter of the ship’s length was unsupported, it exhibited
no deflection, or rather the amount of deflection was imperceptible.
Fig. 62 is from a photograph taken during the building of the ship, and
Fig. 63 shows the hull when completed and nearly ready for launching,
while the vignette at the head of the chapter exhibits the big ship at
anchor when completely equipped. The paddle-wheels are 56 ft. in
diameter, and are turned by four steam engines, each having a cylinder 6
ft. 2 in. in diameter, and 14 ft. in length. The vessel is also provided
with a four-bladed screw-propeller of 24 ft. diameter, driven by another
engine having four cylinders, six boilers, and seventy-two furnaces. The
total actual power of the engines is more than that of 8,000 horses, and
the vessel could carry coals enough to take her round the world—a
capability which was the object of her enormous size. The vessel as
originally constructed contained accommodation for 800 first-class
passengers, 2,000 second class, and 1,200 third class—that is, for 4,000
passengers in all. The principal saloon was 100 ft. long, 36 ft. wide,
and 13 ft. high. Each of her ten boilers weighs 50 tons, and when all
are in action, 12 tons of coal are burnt every hour, and the total
displacement of the vessel laden with coal is 22,500 tons.

Footnote 1:

  She was broken up for old iron, 1889.

[Illustration:

  FIG. 63.—_The Great Eastern ready for Launching._
]

The use of steam power in navigation has increased at an amazing rate.
Between 1850 and 1860 the tonnage of the steam shipping entering the
port of London increased three-fold, and every reader knows that there
are many fleets of fine steamers plying to ports of the United Kingdom.
There are, for example, the splendid Atlantic steamers, some of which
almost daily enter or leave Liverpool, and the well-appointed ships
belonging to the Peninsular and Oriental Company. The steamers on the
Holyhead and Kingston line may be taken as good examples of first-class
passenger ships. These are paddle-wheel boats, and are constructed
entirely of iron, with the exception of the deck and cabin fittings.
Taking one of these as a type of the rest, we may note the following
particulars: the vessel is 334 ft. long, the diameter of the
paddle-wheels is 31 ft., and each has fourteen floats, which are 12 ft.
long and 4 ft. 4 in. wide. The cylinders of the engines are 8 ft. 2 in.
in diameter, and 6 ft. 6 in. long. The ship cost about £75,000. The
average passage between the two ports—a distance of 65½ miles—occupies 3
hours 52 minutes, and at the measured mile the vessel attained the speed
of 20·811 miles per hour. As an example of the magnificent vessels owned
by the Cunard Company, we shall give now a few figures relating to one
of their largest steam-ships, the _Persia_, launched in 1858, and built
by Mr. N. Napier, of Glasgow, for the company, to carry mails and
passengers between Liverpool and New York. Her length is 389 ft., and
her breadth 45 ft. She is a paddle-wheel steamer, with engines of 850
horse-power, having cylinders 100 in. in diameter with a stroke of 10
ft. The paddle-wheels are 38 ft. 6 in. in diameter, and each has
twenty-eight floats, 10 ft. 8 in. long and 2 ft. wide. The _Persia_
carries 1,200 tons of coal, and displaces about 5,400 tons of water.

[Illustration:

  FIG. 64.—_Comparative Sizes of Steamships._

  1838, _Great Western_; 1844, _Great Britain_; 1856, _Persia_; 1858,
    _Great Eastern_.

  A, Section amidships of _Great Eastern_; B, The same of _Great
    Western_. Both on the same scale, but on a larger one than their
    profiles.
]

A velocity of twenty-six miles per hour appears to be about the highest
yet attained by a steamer.[2] This is probably near the limit beyond
which the speed cannot be increased to any useful purpose. The
resistance offered by water to a vessel moving through it increases more
rapidly than the velocity. Thus, if a vessel were made to move through
the water by being pulled with a rope, there would be a certain strain
upon the rope when the vessel was dragged, say, at the rate of five
miles an hour. If we desired the vessel to move at double the speed, the
strain on the rope must be increased four-fold. To increase the velocity
to fifteen miles per hour, we should have to pull the vessel with nine
times the original force. This is expressed by saying that the
resistance varies as the square of the velocity. Hence, to double the
speed, the impelling force must be quadrupled, and as that force is
exerted through twice the distance in the same time, an engine would be
required of eight times the power—or, in other words, the power of the
engine must be increased in proportion to the _cube_ of the velocity; so
that to propel a boat at the rate of 15 miles an hour would require
engines twenty-seven times more powerful than those which would suffice
to propel it at the rate of five miles an hour.

Footnote 2:

  This has now (1895) been far surpassed.—_Vide infra._

The actual speed attained by steam-ships with engines of a given power
and a given section amidships will depend greatly upon the shape of the
vessel. When the bow is sharp, the water displaced is more gradually and
slowly moved aside, and therefore does not offer nearly so much
resistance as in the opposite case; but the greater part of the power
required to urge the vessel forward is employed in overcoming a
resistance which in some degree resembles friction between the bottom of
the vessel and the water.

The wonderful progress which has, in a comparatively short time, taken
place in the power and size of steam-vessels, cannot be better brought
home to the reader than by a glance at Fig. 64, which gives the profiles
of four steamships, drawn on one and the same scale, thus showing the
relative lengths and depths of those vessels, each of which was the
largest ship afloat at the date which is marked below it, and the whole
period includes only the brief space of twenty years!—for this, surely,
is a brief space in the history of such an art as navigation. All these
ships have been named in the course of this article, but in the
following table a few particulars concerning each are brought together
for the sake of comparing the figures:

     ┌─────┬─────────────────┬─────────────────┬────────┬────────┐
     │Date.│      Name.      │   Propulsion.   │Length. │Breadth.│
     ├─────┼─────────────────┼─────────────────┼────────┼────────┤
     │1838 │_Great Western_  │Paddles          │236 ft. │ 36 ft. │
     │1844 │_Great Britain_  │Screw            │322 ft. │ 51 ft. │
     │1856 │_Persia_         │Paddles          │390 ft. │ 45 ft. │
     │1858 │_Great Eastern_  │Screw and paddles│690 ft. │ 83 ft. │
     └─────┴─────────────────┴─────────────────┴────────┴────────┘

[Illustration:

  FIG. 65.—_The s.s. City of Rome._
]

Several passenger ocean-going steamships have been built since the
_Persia_, of still greater dimensions, and of higher engine power. These
have generally been surpassed in late years by some splendid Atlantic
liners, such as the sister vessels owned by the International Navigation
Co., and now named respectively the _New York_ and the _Paris_. The
_City of Rome_, launched in 1881 by the Barrow Steamship Co., is little
inferior in length to the _Great Eastern_, although the tonnage is only
about one-third. The _City of Rome_ is 560 ft. long, 52 ft. wide, and 37
ft. deep. Her engines are capable of working up to 10,000 indicated
horse-power. Fig. 65 is a sketch of this ship, and shows that she
carries four masts and three funnels. The main shaft measures more than
2 ft. across, and the screw-propeller is 24 ft. in diameter. She has
accommodation for 1,500 passengers, and is fitted with all the
conveniences and luxuries of a well-appointed hotel. The International
Navigation Co.’s ship _Paris_, has made the passage across the Atlantic
in less than six days, and appears to be the fastest vessel in the
transatlantic service. In August, 1889, she made the run from shore to
shore in 5 days, 22 hours, 38 minutes.

The extraordinary increase in the speed of steamships that has been
effected within the last few years depends mainly upon the improvements
that have latterly been made in the marine engine—a machine of which we
have been unable to give an account, because its details are too
numerous and complicated to be followed out by the general reader.
Suffice it to say, that the use of higher steam pressures with compound
expansion (p. 18), condensers which admit of the same fresh water being
used in the boilers over and over again, and better furnace
arrangements, are among the more important of these improvements. But
not only have the limits of practicable speed been enlarged, but a
greater economy of fuel for the work done has been attained; the result
being that ocean carriage is now cheaper than ever. The outcome of this
will not cease with simply a greatly extended steam navigation, but
appears destined ultimately to produce effects on the world at large
comparable in range and magnitude with those that may be traced to the
use of the steam engine itself since its first invention.

Among the curiosities of steamboat construction may be mentioned a
remarkable ship which was built a few years ago for carrying passengers
across the English Channel without the unpleasant rolling experienced in
the ordinary steamboats. The vessel, which received the name of the
_Castalia_, was designed by Captain Dicey, who formerly held an official
position at the Port of Calcutta. His Indian experience furnished him
with the first suggestion of the new ship in the device which is adopted
there for steadying boats in the heavy surf. The plan is to attach a log
of timber to the ends of two outriggers, which project some distance
from the side of the vessel; or sometimes two canoes, a certain distance
apart, are connected together. Some of these Indian boats will ride
steadily in a swell that will cause large steamers to roll heavily.
Improving on this hint, Captain Dicey built a vessel with two hulls,
each of which acted as an outrigger to the other. Or, perhaps, the
_Castalia_ may be described as a flat-bottomed vessel with the middle
part of the bottom raised out of the water throughout the entire length,
so that the section amidships had a form like this—

[Illustration]

The two hulls were connected by what we may term “girders,” which
extended completely across their sections, forming transverse partitions
or bulkheads, and these girders were strongly framed together, so as to
form rigid triangles. These united the two hulls so completely, that
there was not any danger of the vessel being strained in a sea-way. The
decks were also formed of iron, although covered with wood, so that the
whole vessel really formed a box girder of enormous section.

[Illustration:

  FIG. 66.—_The Castalia in Dover Harbour._
]

The reason why the steamers which until lately ran between Dover and
Calais, Folkestone and Boulogne, and other Channel ports, were so small,
was because the harbours on either side could not receive vessels with
such a draught as the fine steamers, for example, which run on the
Holyhead and Kingston line. Now, the _Castalia_ drew only 6 ft. of
water, or 1 ft. 6 in. less than the small Channel steamers, and would,
therefore, be able to enter the French ports at all states of the tide.
Yet the extent of the deck space was equalled in few passenger ships
afloat, except the _Great Eastern_ and some of the Atlantic steamers.
The vessel was 290 ft. in length, with an extreme breadth of 60 ft. The
four spacious and elegantly-fitted saloons—two of which were 60 ft. by
36 ft., and two 28 ft. by 26 ft.—and the roomy cabins, retiring rooms,
and lavatories, were the greatest possible contrast to the “cribbed,
cabined, and confined” accommodation of the ordinary Channel steamers.
There were also a kitchen and all requisites for supplying dinners,
luncheons, etc., on board. But besides the above-named saloons and
cabins, there was a grand saloon, which was 160 ft. long and 60 ft.
wide; and the roof of this formed a magnificent promenade 14 ft. above
the level of the sea. There was comfortable accommodation in the vessel
for more than 1,000 passengers.

The inner sides of the hulls were not curved like the outside, but were
straight, with a space between them of 35 ft. wide, and the hulls were
each 20 ft. in breadth, and somewhat more in depth. There were two
paddle-wheels, placed abreast of each other in the water-way between the
two hulls, and each of these contained boilers and powerful engines. The
designers of this vessel calculated that she would attain a speed of 14¾
knots per hour, but this result failed to be realized. Probably there
were no data for the effect of paddles working in a confined
water-space. The position of the paddles is otherwise an advantage, as
it leaves the sides of the vessel free and unobstructed. The ship had
the same form at each end, so it could move equally well in either
direction. There were rudders at both ends, and the steering qualities
of the ship were good. Although the speed of the _Castalia_ was below
that intended, the vessel was a success as regards steadiness, for the
rolling and pitching were very greatly reduced, and the miseries and
inconveniences of the Channel passage obviated.

[Illustration:

  FIG. 67.—_The Castalia in Dover Harbour—End View._
]

The _Castalia_ is represented in Figs. 66 and 67. She was constructed by
the Thames Iron Shipbuilding Co., and launched in June, 1874, but after
she had been tried at sea, it was found necessary to fit her with
improved boilers, and this caused a delay in placing the vessel on her
station.

The _Castalia_ proved a failure in point of speed, and she was soon
replaced by another and more powerful vessel constructed on the same
general plan, and named the _Calais-Douvres_. But this twin-ship again
failed to answer expectations, and as the harbour on the French shore
was meanwhile deepened and improved, new and very fine paddle-wheel
boats, named the _Invicta_, _Victoria_, and _Empress_ have been placed
on the service. As the latter boat, at least, has steamed from Dover to
Calais, nearly twenty-six miles, under the hour, there is nothing more
to be desired in point of speed. A fourth vessel is to take the place of
the twin-ship, _Calais-Douvres_, and will receive the same name.

[Illustration:

  FIG. 68.—_Bessemer Steamer._
]

Another very novel and curious invention connected with steam navigation
was the steamer which Mr. Bessemer built at Hull in 1874. This invention
also was to abolish all the unpleasant sensations which landsmen are apt
to experience in a sea voyage, by effectually removing the cause of the
distressing _mal de mer_. The ship was built for plying between the
shores of France and England, and the method by which he purposed to
carry passengers over the restless sea which separates us from our
Gallic neighbours was bold and ingenious. He designed a spacious saloon,
which, instead of partaking of the rolling and tossing of the ship, was
to be maintained in an absolutely level position. The saloon was
suspended on pivots, much in the same way as a mariner’s compass is
suspended; and by an application of hydraulic power it was intended to
counteract the motion of the ship and maintain the swinging saloon
perfectly horizontal. It was originally proposed that the movements
should be regulated by a man stationed for that purpose, where he could
work the levers for bringing the machinery into action, so as to
preserve the saloon in the required position. This plan was, however,
improved upon, and the adjustments made automatic. It may be well to
mention that it is a mistake to suppose that anything freely suspended,
like a pendulum, on board a ship rolling with the waves, will hang
vertically. If, however, we cause a heavy disc to spin very rapidly, say
in a horizontal plane, the disc cannot be moved out of the horizontal
plane without the application of some force. A very well-made disc may
be made to rotate for hours, and would, by preserving its original plane
of rotation, even show the effect of the earth’s diurnal motion. Mr.
Bessemer designed such a gyroscope to move the valves of his hydraulic
apparatus, and so to keep his swinging saloon as persistently horizontal
as the gyroscope itself. Mr. Bessemer’s ship was 350 ft. long, and each
end, for a distance of 48 ft., was only about 4 ft. from the line of
floating. Above the low ends a breastwork was raised, about 8 ft. high,
and 254 ft. long. In the centre, and occupying the space of 90 ft., was
the swinging saloon intended for first-class passengers. At either end
of this apartment were the engines and boilers. The engines were
oscillating and expansive, working up to 4,600 horse-power, which could
be increased to 5,000. There were two pairs of engines, one set at
either end of the ship, and each having two cylinders of 80 in. in
diameter, and a stroke of 5 ft., working with steam of 30 lbs. pressure
per square inch, supplied from four box-shaped boilers, each boiler
having four large furnaces. The paddle-wheels, of which there were a
pair on either side of the vessel, were 27 ft. 10 in. in diameter
outside the outer ring, and each wheel has twelve feathering floats. The
leading pair of wheels, when working at full speed, were to make
thirty-two revolutions per minute, and the following pair of wheels move
faster.

Entrance into the Bessemer saloon was gained by two broad staircases
leading to one landing, and a flexible passage from this point to the
saloon. The saloon rested on four steel gudgeons, one at each end, and
two close together near the middle. These were not only to support the
saloon, but also to convey the water to the hydraulic engines, by which
the saloon was to be kept steady. For this purpose the after one was
made hollow, and connected with the water mains from powerful engines,
and also with a supply-pipe leading to a central valve-box, by means of
which the two hydraulic cylinders on either side were supplied with
water. Between the two middle gudgeons, a gyroscope, worked by a small
turbine, filled with water from one of the gudgeons, enabled Mr.
Bessemer to dispense with the services of a man, and thus completed his
scheme of a steady saloon, by making the machinery completely automatic.
The saloon was 70 ft. long, 35 ft. wide, and 20 ft. high. The Bessemer
ship proved to be a total failure, and never went to sea as a passenger
boat.

On board of some modern war-ships where speed is essential, and where
the engines are driven at a very great number of revolutions per minute,
as in the case of torpedo-boat catchers, the vibration throughout the
whole of the vessel becomes extremely trying, not only for the nerves of
the crew, but for the security of the structure itself. The cause of
this vibration and consequent strain and loss of power is not far to
seek. The cylinders of marine engines are always of a large diameter, 6
feet, 8 feet, or even more sometimes, and the pistons and piston-rods
are necessarily of great strength and corresponding weight. Now, at
every half revolution of the engines, this heavy mass of piston and
piston-rod, though moving at an exceedingly high speed in the middle of
the stroke, has to be brought to a standstill, and an equal velocity in
the opposite direction imparted to it. A large portion of the power is
therefore uselessly expended in stopping a great moving mass, and
reversing its motion. All the force required to do this reacts on the
vessel’s frame. Many attempts have been made to construct rotatory
steam-engines, and some hundreds of patents taken out for such
inventions, which in general have a piston revolving about a shaft; but
the great friction, and consequent liability to wear out, have prevented
their practical use.

Lately, a method of using steam on the principle embodied in the water
turbine has been developed, and within the last six or seven years has
found successful application in propelling electro-dynamos at very high
speeds. In the steam turbine there are no pistons, piston-rods, or other
reciprocating parts, the effect depending on the same kind of reaction
that is taken advantage of in the water turbine (which has a high
efficiency in giving out a large proportion of energy), and the power is
applied with smoothness and an entire absence of the oscillations that
would shake to pieces any vessel that an ordinary steam-engine could
propel at the same rate.

The advantages of the steam turbine have been proved by the performances
of a small experimental vessel lately built at Newcastle, and
appropriately named the _Turbinia_. She is only 100 feet in length, and
9 feet in breadth, with a displacement of some 44 tons. Now the highest
record speed for any vessel of that size is 24 knots per hour; but the
_Turbinia_, in a heavy sea, showed, at a measured mile, the speed of 32¾
knots, which is believed to be greater than that of any craft now
afloat, being nearly 37¾ miles an hour, or equal to that of an ordinary
railway train. Besides that, it has been found by experiment, that an
arrangement of the blades of the screw propeller more suitable to high
velocities will enable a still greater speed to be obtained. The weight
of the turbine engines of this vessel is only 3 tons, 13 cwts., and the
whole weight of the machinery, including boilers and condensers, is only
22 tons, with an indicated H.P. of 1576, and a steam consumption of but
16 lbs. per hour. The weight of the turbine is only one-fifth of that of
marine engines of equal power; the space occupied is smaller; the
initial cost is less; not so much superintendence is required; the
charges of maintenance are diminished; reduced dimensions of propeller
and shaft suffice; vibration is eliminated; speed is increased; and
greater economy of fuel is secured.


              _THE RIVER AND LAKE STEAM-BOATS OF AMERICA._

The chapter on “Steam Navigation,” in the foregoing pages, has dealt
mainly with the progress of the ocean-going steam-ship, from the
establishment of regular transatlantic services down to the building of
the splendid liners, the _New York_ and the _Paris_, and we have
recorded, in addition, the performances of the pair of hitherto
unsurpassed sister ships, the _Campania_ and the _Lucania_. The
importance and interest attaching to steam navigation is, however, by no
means confined to ocean-going vessels, and the chapter demands a
supplementary notice of the great developments of the steam-ship in
other parts of the world than Britain, more particularly where great
rivers, navigable for hundreds of miles, and lakes, spreading their
waters over vast areas, present conditions of traffic and opportunities
for adaptation to an extent that could not be required within the range
of Britain or British oceanic lines.

[Illustration:

  PLATE IX.

  THE “MARY POWELL.”
]

If the reader will cast his eye on the map of the United States, he will
see towards the northern boundary a great fresh-water system, comprising
five enormous lakes, the least of which is nearly two hundred, and the
largest nearly three hundred miles in length, in all presenting a total
area greater by far than that of England and Scotland together thrice
told. This lake system has a line of coast to be reckoned only by
thousands of miles, and for a long time an enormous traffic has been
carried across its waters by sailing vessels of all kinds, two- or
three-masted schooners, brigs, and other craft, carrying wood, stone,
lime, and other commodities. On the map, the position of the Detroit
River, which leads from the southern extremity of Lake Huron to Lake
Erie, will readily be recognised, and this strait, which is in the only
line of transport from the three great upper lakes, formerly presented
all the picturesqueness that crowds of boats of every build could
impart. Especially was this the case at Amherstburg, its southern
extremity, where sometimes a northern wind would make the passage
impracticable for several days in succession, and a fleet of a hundred
or two hundred sailing vessels would collect to await the opportunity of
a favouring breeze in order to carry them against the current to Port
Huron. Then, taking advantage of the right moment, they would set their
sails, and in a compact body move slowly up the strait. This was not
quick enough to meet the traffic, and, before long, larger vessels were
built, which were towed up and down the Detroit by steam-tugs. The next
step of replacing sailing ships by steam-vessels was not long in
following, and though there still exist fine specimens of sailing craft
on the lakes, their day may be said to be over. The navigation of these
lakes, before the extensive development of the railway systems near
their shores, comprised a large passenger traffic, which was carried on
by big paddle-wheel steamers, and at the time of the great westward set
of emigration to Michigan, Wisconsin, and Minnesota, these steamers were
crowded to their utmost capacity. The great improvement which in recent
years has become possible for passenger steamers in speed, cabin
accommodation, and other particulars, above all, the growth of great
cities on the shores, the progress of the territories adjoining the lake
system, and other circumstances, are now combining to renew the
passenger traffic on a larger scale than ever. “Fifteen millions of
people,” says Mr. H. A. Griffin, the Secretary of the Cleveland Board of
Control (_Engineering Magazine_, iv., 819), “now live upon the shore
lines of the lakes, or within six hours’ travel by rail, and nearly all
of that population is south of the United States boundary line. The
territory directly tributary to the lakes, north and south of the line,
is capable of easily maintaining a population of 100,000,000.... It does
not require a very lively imagination to foresee the Great Lakes
surrounded by the most prosperous and progressive people on earth, and
crossed and recrossed by scores of lines of passenger steam-ships, in
addition to a still greater number of freight lines.” The number of
first-class passenger steamers already launched or on the stocks is an
indication that the revival of passenger traffic will not lag or be
delayed.

The unique conditions and requirements of this lacustrine traffic were
bound to lead to types of vessels differing in many respects from the
steam-ships to be seen in the harbours of Great Britain. The
introduction of iron shipbuilding gave a great impetus to the
construction of the lake steamers, for vessels of more than 3,000 tons
could be built with a comparatively shallow draught of water (15½ feet),
which was one of the necessities of the situation. As far back as 1872,
iron shipbuilding had been fully established at Cleveland and Detroit,
and at the latter place scores of splendid steel steam-ships have been
turned out. The Cleveland builders have not been far behind, and
Buffalo, Milwaukee, Chicago, and other places, have followed suit. At
the beginning of 1893, there were on the lakes more than fifty vessels
of over 2,000 tons each, while the total number of steam vessels of all
kinds was considerably over 1,600, and sailing vessels with steam-tugs
counted over 2,000. The tonnage of the ships on the lakes has been
estimated at about 36 per cent. of the whole mercantile marine of the
United States, and it is said that 40,000 men are employed upon the
vessels. The total freight passing Detroit in 1892 was calculated to
exceed 34,000,000 tons, an amount greater than the whole foreign and
coasting trade of the port of London. There are more than thirty
shipbuilding concerns on the lakes, and some of them possess large dry
docks of their own; but there are also independent companies owning dry
docks of great size. Some of these shipbuilding establishments have
turned out steel ocean-going tugs, paddle and screw passenger steamers,
cargo-carrying boats, vessels for carrying railway trains across the
Detroit river, etc., etc.

[Illustration:

  FIG. 68_a_.—_A Whaleback Steamer, No. 85, Built at West Superior,
    Wisconsin._
]

The extent and importance which steam navigation has attained in a
definite region have been indicated in the preceding paragraphs; but an
attempt to show by illustration and description the several
characteristic forms the steam-ship has now assumed in these lacustrine
waters would carry us far beyond our allotted limits. The steam vessels
now on the lakes are almost exclusively actuated by screw-propellers,
whether they are passenger or freight boats. The boilers and engines are
near the stern, and the hulls are usually of great length; in fact, some
of these steamboats will compare in dimensions with the _Persia_, which
was the transatlantic marvel about the year 1857. (See p. 137.) Such is
the _Mariposa_, launched in 1892, which is 350 feet long and 45 feet
broad, carrying 3,800 net tons, with a draught of only 15½ feet. There
are others, 380 feet long, with engines of 7,000 horse-power, steaming
at 20 miles an hour, and providing ample accommodation for 600
passengers. The newest and most novel type of steam-ship on the lakes is
the “whaleback.” The celerity with which ships of this kind have been
constructed on occasion is perfectly marvellous. One of them, named the
_Christopher Columbus_, designed to carry passengers to and from the
World’s Fair at Chicago in 1893, was launched in fifty-six days after
the keel had been laid, yet it was a ship intended to carry 5,000
passengers, having a length over all of 362 feet, breadth 42 feet, depth
24 feet. The “whaleback” steamers are designed to give the greatest
carrying capacity with a given draught of water, and all the structures
usually fitted to the upper deck of a steamer are in them replaced by
the plain curved and closed deck, over which, when the vessel is in a
storm, waves may sweep harmlessly, thus avoiding the shocks received by
ships with high sides.

The river steam-boat was, as we have seen, nearly coeval with the
nineteenth century, and although its practicability was first
demonstrated in British waters, regular steam navigation was not
established until a few years afterwards, when, in 1807, Robert Fulton
placed on the River Hudson its first steam-boat. To this others were
soon added, so that in 1813 there were six steam-boats regularly plying
on the Hudson before a single one ran for hire on the Thames. An article
by Mr. Samuel Ward Stanton, in a recent number of _The Engineering
Magazine_, gives a very full account of the Hudson River steam-boats
from the beginning down to 1894, and to this article we are mainly
indebted for the details we are about to give.

The Hudson River washes the western shore of Manhattan Island, on which
stands by far the greater part of the city of New York, with its vast
population. The river is here straight, and has a nearly uniform width
of one mile; at New York it is commonly called the _North River_,
because of the direction of its course, for it descends from almost the
due north. It is not one of the great rivers of the United States as
regards length or extent of navigation; not, _e.g._, like the
Mississippi and the Missouri, which are ascended by steam-boats to
thousands of miles above their mouths; but it has one of the world’s
great capitals on its shores, and at the quays, which occupy both its
banks to the number of eighty or more, may be seen in multitudes some of
the finest ocean-going steamships, trading to every considerable port in
the world. The North River separates New York from what are practically
the populous suburbs of Jersey City and Hoboken, though these are
controlled by their own municipalities.

It was on the River Hudson that steam navigation was inaugurated by
Fulton with a vessel which was 133 feet long, 18 feet broad, and 7 feet
deep, and was named the _Clermont_. The speed attained was but five
miles an hour. The first trip was made on the 7th August, 1807, to
Albany, 150 miles up the river from New York, with twenty-four
passengers on board, and the new kind of locomotion was so well
patronised that during the following winter, when the Hudson navigation
had to be suspended on account of the ice, it was considered expedient
to enlarge the capacity of the boat by adding both to her length and
width; at the same time her name was changed to _The North River_, and
she plied regularly for several seasons afterwards. Her speed down the
river with the current was evidently greater than that of the first trip
up the river, for on 9th November, 1809, the New York _Evening Post_
announced that “The North River steam-boat arrived this afternoon in
twenty-seven and a half hours from Albany, with sixty passengers.”

The paddle-wheels were of a primitive form, and as they were unprovided
with paddle-boxes, the arrangement had the appearance of a great
undershot mill-wheel on each side of the boat, above the deck of which
was placed the steam-engine, a position it has retained in all these
river-boats, in which a huge, rhombus-shaped beam, oscillating high
above the deck, is a conspicuous feature. Another boat of much larger
dimensions was built the following year, having a tonnage of nearly 300,
and from that time there has been a more or less regular increase in the
sizes of the vessels, until in 1866 a tonnage of nearly 3,000 was
reached. In 1817 a vessel called the _Livingstone_ was launched, which
was able to go up to Albany in eighteen hours. In 1823 was launched the
_James Kent_, a novel feature in which vessel was the boiler made of
copper, and weighing upwards of 30 tons. It was so planned that if it
happened to burst, the hot water would be carried through the bottom of
the vessel by tubes or hollow pillars. From this it appears that
considerable apprehension existed as to the liability of the boilers
exploding. We are told that the cost of the copper boiler was in this
case nearly one-third of that of the whole vessel. The cabins are
described as having been very handsomely fitted up, and the speed was
such that fourteen hours sufficed for the trip up river to Albany. Many
fine boats were placed on the river during the twenty following years,
and these were marked by various improvements, as when, in 1840,
anthracite coal was for the first time substituted for wood as the fuel
for the furnaces, with the effect of reducing the cost of this item to
one-half. Then, in 1844, iron began to be used for constructing the
hulls, and a few years afterwards, steamers having a speed of twenty
miles an hour and over, became quite common. In 1865, and again in the
eighties, some four screw-propeller boats were built; but this type does
not appear to have found much favour on the Hudson, for the large
paddle-wheels and the single or double beam, working high above the
deck, have continued the almost universal form of construction. A very
popular and famous boat was placed on the Hudson in 1861. This was the
_Mary Powell_, called the “Queen of the Hudson,” which, although a boat
of moderate tonnage (983), was able on occasion to steam at the rate of
twenty-five miles an hour. This vessel was placed on the line between
New York and Rondont, and was still running in 1894.

One of the most modern and most elegant boats on the Hudson is the _New
York_, launched in 1887, and declared by Mr. Stanton to be one of the
finest river steam-boats in the world, well arranged, and beautifully
finished and furnished. She is built on fine lines, is 311 feet long, 40
feet broad, and with a tonnage of 1,552, draws only 12¼ feet of water.
She can steam at twenty miles an hour, and is placed on one of the New
York and Albany lines. Throughout the summer there are both day and
night boats for Albany, and the latter especially are of great size,
three stories high, and provided with saloons, state-rooms, and, in
fact, all the accommodation of a luxurious first-class hotel. The
vessels named in this notice include but a few of the splendid boats
that ply on the River Hudson, and, in respect of their numbers, speed,
and comfort, it may safely be asserted that they cannot be equalled on
any other river in the world.

[Illustration:

  PLATE X.

  THE “NEW YORK.”
]

[Illustration:

  FIG. 69.—_H.M.S. Devastation in Queenstown Harbour._
]



                             SHIPS OF WAR.


“Take it all in all, a ship of the line is the most honourable thing
that man, as a gregarious animal, has ever produced. By himself,
unhelped, he can do better things than ships of the line; he can make
poems, and pictures, and other such concentrations of what is best in
him. But as a being living in flocks, and hammering out with alternate
strokes and mutual agreement, what is necessary for him in those flocks
to get or produce, the ship of the line is his first work. Into that he
has put as much of his human patience, common sense, forethought,
experimental philosophy, self-control, habits of order and obedience,
thoroughly wrought hand-work, defiance of brute elements, careless
courage, careful patriotism, and calm expectation of the judgment of
God, as can well be put into a space of 300 ft. long by 80 ft. broad.
And I am thankful to have lived in an age when I could see this thing so
done.” So wrote Mr. Ruskin about forty years ago, referring, of course,
to the old wooden line-of-battle ships. It may be doubted whether he
would have written thus enthusiastically about so unpicturesque an
object as the _Glatton_, just as it may be doubted whether the
armour-plated steamers will attain the same celebrity in romance and in
verse as the old frigates with their “wooden walls.” Certain it is that
the patience, forethought, experimental philosophy, thoroughly wrought
hand-work, careful patriotism, and other good qualities which Mr. Ruskin
saw in the wooden frigates, are not the less displayed in the new
ironclads.

Floating batteries, plated with iron, were employed in the Crimean War
at the instigation of the French Emperor. About the same time the
question of protecting ships of war by some kind of defensive armour was
forced upon the attention of maritime powers, by the great strides with
which the improvements in artillery were advancing; for the new guns
could hurl projectiles capable of penetrating, with the greatest ease,
any wooden ship afloat. The French Government took the initiative by
constructing _La Gloire_, a timber-framed ship, covered with an armour
of rolled iron plates, 4½ in. thick. The British Admiralty quickly
followed with the _Warrior_, a frigate similar in shape to the wooden
frigates, but built on an iron frame, with armour composed of plates 4½
in. thick, backed by 18 in. of solid teak-wood, and provided with an
inner skin of iron. The _Warrior_ was 380 ft. long, but only 213 ft. of
this length was armoured. The defensive armour carried by the _Warrior_,
and the ironclads constructed immediately afterwards, was quite capable
of resisting the impact of the 68 lb. shot, which was at that time the
heaviest projectile that could be thrown by naval guns. But to the
increasing power of the new artillery it soon became necessary to oppose
increased thickness of iron plates. The earlier ironclads carried a
considerable number of guns, which could, however, deliver only a
broadside fire, that is, the shots could, for the most part, be sent
only in a direction at right angles to the ship’s length, or nearly so.
But in the more recently built ironclads there are very few guns, which
are, however, six times the weight of the old sixty-eight pounders, and
are capable of hurling projectiles of enormous weight. The ships built
after the _Warrior_ were completely protected by iron plates, and the
thickness of the plates has been increased from time to time, with a
view of resisting the increased power which has been progressively given
to naval guns. A contest, not yet terminated, has been going on between
the artillerist and the ship-builder; the one endeavouring to make his
guns capable of penetrating with their shot the strongest defensive
armour of the ships, the other adding inch after inch to the thickness
of his plates, in order, if possible, to render his ship invulnerable.

[Illustration:

  FIG. 70.—_Section of H.M.S. Hercules._
]

One of the finest of the large ironclads is the _Hercules_, of which a
section amidships is presented on the next page. This ship is 325 ft. in
length, and 59 ft. in breadth, and is fitted with very powerful engines
which will work up to 8,529 indicated horse-power. The tonnage is 5,226;
weight of hull, 4,022 tons; weight of the armour and its backing, 1,690
tons; weight of engines, boilers, and coals, 1,826 tons; total with
equipment and armament, 8,676 tons. Although the _Hercules_ carries this
enormous weight of armour and armament, her speed is very great,
excelling, in fact, that of any merchant steamer afloat, for she can
steam at the rate of nearly 17 miles an hour. She also possesses, in a
remarkable degree, the property which naval men call _handiness_; that
is, she can be quickly turned round in a comparatively small space. The
handiness of a steamer is tested by causing her to steam at full speed
with the helm hard over, when the vessel will describe a circle. The
smaller the diameter of that circle, and the shorter the time required
to complete it, the better will the vessel execute the movements
required in naval tactics. Comparing the performances of the _Warrior_
and the _Hercules_, we find that the smallest circle the former can
describe is 1,050 yards in diameter, and requires nine minutes for its
completion, whereas the latter can steam round a circle of only 560
yards diameter in four minutes. The section (Fig. 70) shows that, like
the _Great Eastern_, the _Hercules_ is constructed with a double hull,
so that she would be safe, even in the event of such an accident as
actually occurred to the _Great Eastern_, when a hole was made by the
stripping off of her bottom plates, 80 ft. long and 5 ft. wide. The
defensive armour of the _Hercules_ is, it will be observed, greatly
strengthened near the water-line, where damage to the ship’s side would
be most fatal. The outer iron plates are here 9 in. thick, while in
other parts the thickness is 8 in., and in the less important positions
6 in. The whole of the hull is, however, completely protected above the
water-line, and the iron plates are backed up by solid teak-wood for a
thickness of from 10 in. to 12 in. The teak is placed between girders,
which are attached to another iron plating 1½ in. thick, supported by
girders 2 ft. apart. The spaces between these girders are also filled
with teak, and the whole is lined with an inner skin of iron plating, ¾
in. thick. The belt along the water-line has thus altogether 11¼ in. of
iron, of which 9 in. are in one thickness, and this part is, moreover,
backed by additional layers of teak, as shown in the section; so that,
besides the 11¼ in. of iron, the ship’s side has here 3 ft. 8 in. total
thickness of solid teak-wood. The deck is also covered with iron plates,
to protect the vessel from vertical fire. The _Hercules_ carries eight
18–ton guns as her central battery, and two 12–ton guns in her bow and
stern: these guns are rifled, and each of the larger ones is capable of
throwing a shot weighing 400 lbs. The guns can be trained so as to fire
within 15° of the direction of the keel; for near the ends of the
central battery the ports are indented, and the guns are mounted on
Scott’s carriages, in such a manner that any gun-slide can be run on to
a small turn-table, and shunted to another port, just as a
railway-carriage is shunted from one line to another. Targets for
artillery practice were built so as to represent the construction of the
side of the _Hercules_, and it was found, as the result of many
experiments, that the vessel could not be penetrated by the 600 lb. shot
from an Armstrong gun, fired at a distance of 700 yds. The production of
such iron plates, and those of even greater thickness which have since
been used, forms a striking example of the skill with which iron is
worked. These plates are made by rolling, and it will be understood that
the machinery used in their formation must be of the most powerful kind,
when it is stated that plates from 9 in. to 15 in. thick are formed with
a length of 16 ft. and a breadth of 4 ft. The plates are bent, while red
hot, by enormous hydraulic pressure, applied to certain blocks, upon
which the plates are laid, the block having a height adjusted according
to the curve required. The operation requires great care, as it must be
accomplished without straining the parts in a manner injurious to the
strength of the plate.

[Illustration:

  FIG. 71.—_Section of H.M.S. Inconstant._
]

Fig. 71 on the next page is the section of another ship of war, the
_Inconstant_, which has not, like the _Hercules_, been designed to
withstand the impact of heavy projectiles, but has been built mainly
with a view to speed. The _Inconstant_ has only a thin covering of iron
plating, except in that portion of the side which is above water, where
there is a certain thickness of iron diminishing from the water-line
upwards, but not enough to entitle the _Inconstant_ to be classed as an
armoured vessel. This ship, however, may be a truly formidable
antagonist, for she carries a considerable number of heavy guns, which
her speed would enable her to use with great effect against an adversary
incapable of manœuvring so rapidly. She could give chase, or could run
in and deliver her fire, escaping by her speed from hostile pursuit in
cases where the slower movements of a ponderous ironclad would be much
less effective. The _Inconstant_ carries ten 12–ton guns of 9 in.
calibre, and six 6–ton 7 in. guns, all rifled muzzle-loaders, mounted on
improved iron carriages, which give great facilities for handling them
The ship is a frigate 338 ft. long and 50 ft. broad, with a depth in the
hold of 17 ft. 6 in. She is divided by bulkheads into eleven water-tight
compartments. The engines are of 6,500 indicated horse-power, and the
vessel attains an average speed of more than 18½ miles per hour.

[Illustration:

  FIG. 72.—_Section, Elevation, and Plan of Turret of H.M.S. Captain._
]

[Illustration:

  FIG. 73.—_H.M.S. Captain._
]

A new system of mounting very heavy naval guns was proposed by Captain
Coles about 1861. This plan consists in carrying one or two very heavy
guns in a low circular tower or turret, which can be made to revolve
horizontally by proper machinery. The turret itself is heavily armoured,
so as to be proof against all shot, and is carried on the deck of the
ship, which is so arranged that the guns in the turret can be fired at
small angles with the keel. The British Admiralty having approved of
Captain Coles’ plans, two first-class vessels were ordered to be built
on the turret system. These were the _Monarch_ and the _Captain_—the
latter of which we select for description on account of the melancholy
interest which attaches to her. On page 155 a diagram is given
representing the profile of the _Captain_, in which some of the
peculiarities of the ship are indicated—the turrets with the muzzles of
two guns projecting from each being easily recognized. The _Captain_ was
320 ft. long and 53 ft. wide. She was covered with armour plates down to
5 ft. below the water-line, as represented by the dark shading in the
diagram. The outer plating was 8 in. thick opposite the turrets, and 7
in. thick in other parts. It was backed up by 12 in. of teak; there were
two inner skins of iron each ¾ in. thick, then a framework with
longitudinal girders 10 in. deep. The deck was plated in the spaces
opposite the turrets with iron 1½ in. thick. The _Captain_ was fitted
with twin screws—that is, instead of having a single screw, one was
placed on each side, their shafts being, of course, parallel with the
vessel’s length. The object of having two screws was not greater power,
for it is probable that a single screw would be more effectual in
propelling the ship; but this arrangement was adopted because it was
considered that, had only one screw been fixed, the ship might easily be
disabled by the breaking of a blade or shaft; whereas in the case of
such an accident to one of the twin screws, the other would still be
available. The twin screws could also be used for steering, and the
vessel could be controlled without the rudder, as the engines were quite
independent of each other, each screw having a separate pair. The
diameter of the screws was 17 ft. The erections which are shown on the
deck between the turrets afforded spacious quarters for the officers and
men. These structures were about half the width of the deck, and tapered
off to a point towards the turrets, so as leave an unimpeded space for
training the guns, which could be fired at so small an angle as 6° with
the length of the vessel. Above these erections, and quite over the
turrets, was another deck, 26 ft. wide, called the “hurricane deck.” The
ship was fully rigged and carried a large spread of canvas. But the
special features are the revolving turrets, and one of these is
represented in detail in Fig. 72, which gives a section, part elevation,
and plan. Of the construction of the turret, and of the mode in which it
was made to revolve, these drawings convey an idea sufficiently clear to
obviate the necessity of a minute description. Each turret had an
outside diameter of 27 ft., but inside the diameter was only 22 ft. 6
in., the walls being, therefore, 2 ft. 3 in. thick—nearly half this
thickness consisting of iron plating. Separate engines were provided for
turning the turrets, and they could also be turned by men working at the
handles shown in the figures. Each turret carried two 25–ton Armstrong
guns, capable of receiving a charge of 70 lbs. of gunpowder, and of
throwing a 600 lb. shot.

After some preliminary trials the _Captain_ was sent to sea, and behaved
so well, that Captain Coles and Messrs. Laird, her designer and
contractors, were perfectly satisfied with her qualities as a sea-going
ship. She was then sent in the autumn of 1870 on a cruise with the
fleet, and all went well until a little after midnight between the 6th
and 7th September, 1870, when she suddenly foundered at sea off Cape
Finisterre. The news of this disaster created a profound sensation
throughout Great Britain, for, with the exception of nineteen persons,
the whole crew of five hundred persons went down with the ship. Captain
Coles, the inventor of the turrets, was in the ill-fated vessel and
perished with the rest, as did also Captain Burgoyne, the gallant
commander, and the many other distinguished naval officers who had been
appointed to the ship; among the rest was a son of Mr. Childers, then
First Lord of the Admiralty. Although the night on which this
unfortunate ship went down was squally, with rain, and a heavy sea
running, the case was not that of an ordinary shipwreck in which a
vessel is overwhelmed by a raging storm. It might be said, indeed, of
the loss of the _Captain_ as of that of the _Royal George_:

                       “It was not in the battle;
                       No tempest gave the shock;
                       She sprang no fatal leak;
                       She ran upon no rock.”

[Illustration:

  FIG. 74.
]

[Illustration:

  FIG. 75.
]

One of the survivors, Mr. James May, a gunner, related that, shortly
after midnight he was roused from his sleep by a noise, and feeling the
ship uneasy, he dressed, took a light, and went into the after turret,
to see if the guns were all right. He found everything secure in the
turret, but that moment he felt the ship heel steadily over, and a heavy
sea having struck her on the weather side, the water flowed into the
turret, and he got out through the hole in the top of the turret by
which the guns were pointed, only to find himself in the water. He swam
to the steam-pinnace, which he saw floating bottom upwards, and there he
was joined by Captain Burgoyne and a few others. He saw the ship turn
bottom up, and sink stern first, the whole time from her turning over to
sinking not being more than a few minutes. Seeing the launch drifting
within a few yards, he called out, “Jump, men! it is your last chance.”
He jumped, and with three others reached a launch, in which were fifteen
persons, all belonging to the watch on deck, who had found means of
getting into this boat. One of these had got a footing on the hull of
the ship as she was turning over, and he actually walked over the bottom
of the vessel, but was washed off by a wave and rescued by those who in
the meantime had got into the launch. It appears that Captain Burgoyne
either remained on the pinnace or failed to reach the launch. Those who
were in that boat, finding the captain had not reached them, made an
effort to turn their boat back to pick him up, but the boat was nearly
swamped by the heavy seas, and they were obliged to let her drift. One
man was at this time washed out of the boat and lost, after having but
the moment before exclaimed, “Now, lads, I think we are all right.”
After twelve hours’ hard rowing, without food or water, the survivors,
numbering sixteen men and petty officers and three boys, reached Cape
Finisterre, where they received help and attention. On their arrival in
England, a court-martial was, according to the rules of the service,
formally held on the survivors, but in reality it was occupied in
investigating the cause of the catastrophe. The reader may probably be
able to understand what the cause was by giving his attention to some
general considerations, which apply to all ships whatever, and by a
careful examination of the diagrams, Figs. 74 and 75, which are copied
from diagrams that were placed in the hands of the members of the
court-martial. The letters b and g and the arrows are, however, added,
to serve in illustration of a part of the explanation. The vessel is
represented as heeled over in smooth water, and the gradations on the
semicircle in Fig. 74 will enable the reader to understand how the heel
is measured by angles. If the ship were upright, the centre line would
coincide with the upright line, marked o on the semicircle, and drawn
from its centre. Suppose a level line drawn through the centre of the
semicircle, and let the circumference between the point where the last
line cuts it and the point o be divided into ninety equal parts, and let
these parts be numbered, and straight lines drawn from the centre to
each point of division. In the figure the lines are drawn at every fifth
division, and the centre line of the ship coincides with that drawn
through the forty-fifth division. In this case the vessel is said to be
inclined, or heeled, at an angle of forty-five degrees, which is usually
written 45°. In a position half-way between this and the upright the
angle of heel would be 22½°, and so on. The reader no doubt perceives
that a ship, like any other body, must be supported, and he is probably
aware that the support is afforded by the upward pressure of the water.
He may also be familiar with the fact that the weight of every body acts
upon it as if the whole weight were concentrated at one certain point,
and that this point is called the centre of gravity of the body.
Whatever may be the position of the body itself, its centre of gravity
remains always at the same point with reference to the body. When the
centre of gravity happens to be within the solid substance of a body,
there is no difficulty in thinking of the force of gravitation acting as
a downward pull applied at the centre of gravity. But this point is by
no means always within the substance of bodies: as often as not it is in
the air outside of the body. Thus the centre of gravity of a uniform
ring or hoop is in the centre, where, of course, it has no material
connection with the hoop; but in whatever position the hoop may be
placed, the earth’s attraction pulls it _as if_ this central point were
rigidly connected with the hoop, and a string were attached to the point
and constantly pulled downwards. This explanation of the meaning of
centre of gravity may not be altogether superfluous, for, when the
causes of the loss of the _Captain_ were discussed in the newspapers, it
became evident that such terms as “centre of gravity” convey to the
minds of many but very vague notions. One writer in a newspaper enjoying
a large circulation seriously attributed the disaster to the
circumstance of the ship having lost her _centre of gravity_! The upward
pressure of water which supports a ship is the same upward pressure
which supported the water before the ship was there—that is, supported
the mass of water which the ship displaces, and which was in size and
shape the exact counterpart of the immersed part of the ship. Now, this
mass of water, considered as a whole, had itself a centre of gravity
through which its weight acted downwards, and through which it is
obvious that an equal upward pressure also acted. This centre of gravity
of the displaced water is usually termed the “centre of buoyancy,” and,
unlike the centre of gravity, it changes its position with regard to the
ship when the latter is inclined, because then the immersed part becomes
of a shape different for each inclination of the ship. Now, recalling
for an instant the fundamental law of floating bodies—namely, that the
weight of the water displaced is equal to the weight of the floating
body—we perceive that in the case of a ship there are two equal forces
acting vertically, viz., the weight of the ship or downward pull of
gravitation acting at G, Fig. 74, the centre of gravity of the ship, and
an equal upward push acting through B, the centre of buoyancy. It is
obvious that the action of these forces concur to turn a ship placed as
in Fig. 74 into the upright position. It is by no means necessary for
this effect that the centre of gravity should be below the centre of
buoyancy. All that is requisite for the stability of a ship is, that
when the ship is placed out of the upright position, these forces should
act to bring her back, which condition is secured so long as the centre
of buoyancy is nearer to the side towards which the vessel is inclined
than the centre of gravity is. When there is no other force acting on a
ship or other floating body, these two points are always in the same
vertical line. The two equal forces thus applied in parallel directions
constitute what is called in mechanics a “couple,” and the effect of
this in turning the ship back into the upright position is the same as
if a force equal to its weight were applied at the end of a lever equal
in length to the horizontal distance between the lines through B and G.
The righting force, then, increases in proportion to the horizontal
distance between the two points, and it is measured by multiplying the
weight of the ship in tons by the number of feet between the verticals
through G and B, the product being expressed in statical foot-tons, and
representing the weight in tons which would have to be applied to the
end of a lever 1 ft. long, in order to produce the same turning effect.
When a ship is kept steadily heeled over by a side wind, the pressure of
the wind and the resistance of the water through which the vessel moves
constitute another couple exactly balancing the righting couple. The
moment of the righting couple, or the righting force, or statical
stability as it is also called, is determined by calculation and
experiment from the design of the ship, and from her behaviour when a
known weight is placed in her at a known distance from the centre. Such
calculations and experiments were made in the case of the _Captain_, but
do not appear to have been conducted with sufficient care and
completeness to exhibit her deficiency in stability. After the loss of
the ship, however, elaborate computations on these points were made from
the plans and other data. The following table gives some of the results,
with the corresponding particulars concerning the _Monarch_ for the sake
of comparison:

 ┌───────────────────────────────────────────────┬──────────┬──────────┐
 │                                               │_Monarch._│_Captain._│
 ├───────────────────────────────────────────────┼──────────┼──────────┤
 │  I. Angle at which the edge of the deck is    │   28°    │   14°    │
 │       immersed                                │          │          │
 │ II. Statical righting force in foot-tons at   │  12,542  │  5,700   │
 │       the angle at which the deck is immersed │          │          │
 │III. Angle of greatest stability               │   40°    │   21°    │
 │ IV. Greatest righting force in foot-tons      │  15,615  │  7,100   │
 │  V. Angle at which the righting force ceases  │   59°    │   54°    │
 │ VI. Reserve of dynamical stability at an angle│  6,500   │   410    │
 │       of 14° in _dynamical_ foot-tons         │          │          │
 └───────────────────────────────────────────────┴──────────┴──────────┘

From No. V. in the above table we learn that if the _Captain_ had been
heeled to 54°, the centre of gravity would have overtaken the centre of
buoyancy—that is, the two would have been in one vertical line. Any
further heeling would have brought the points into the position shown in
Fig. 75, where it is obvious that the action of the forces is now to
turn the vessel still more on its side, and the result is an upsetting
couple instead of a righting couple.

These figures and considerations refer to the case of the vessel
floating in smooth water, but the case of a vessel floating on a wave is
not different in principle. The reader may picture to himself the
diagrams inclined so that the water-line may represent a portion of the
wave’s surface; then he must remember that the very action which heaves
up the water in a sloping surface is so compounded with gravity, that
the forces acting through G and B retain nearly the same position
relatively to the surface as before.

No. VI. in the foregoing table requires some explanation. To heel a ship
over to a certain angle a certain amount of _work_ must be done, and in
the scientific sense _work_ is done only when something is moved through
a space against a resistance. When the weight of a ton is raised 1 ft.
high, one foot ton of work is said to be done; if 2 tons were raised 1
ft., or 1 ton were raised 2 ft., then two foot-tons of work would be
done, and so on. The same would be the case if a pressure equal to those
weights were applied so as to move a thing in any direction through the
same distances. It should be carefully noticed that the foot-ton is
quite a different unit in this case from what it is as the moment of a
couple. If we heel a ship over by applying a pressure on the masts, it
is plain that the pressure must act through a certain space, and the
same heel could be caused either by means of a smaller pressure or a
greater, according as we apply it higher up or lower down; but the space
through which it must act would vary, so that the product of the
pressure and space would, however, be always the same. No. VI. shows the
amount of work that would have to be done in order completely to upset
each of the vessels when already steadily heeled over to 14°. The
amounts in the two cases are so different that we can easily understand
how a squall which would not endanger the _Monarch_ might throw the
_Captain_ over. A squall suddenly springing up would do more than heel a
vessel over to the angle at which it is able to maintain it: it would
swing it beyond that position by reason of the work done on the sails as
they are moving over with the vessel, and the latter would come to a
steady angle of heel only after a series of oscillations. Squalls,
again, which, although suddenly springing up in this manner, could not
heel the ship over beyond the angle where the stability vanishes, might
yet do so if they were intermittent and should happen to coincide in
time with the oscillations of the ship—just as a series of very small
impulses, coinciding with the time of the vibrations of a heavy
pendulum, may accumulate so as to increase the range of vibration to any
extent. It is believed that in the case of the _Captain_ the pressure of
the wind on the underside of the hurricane assisted in upsetting the
vessel. This, however, could only have exerted a very small effect
compared to that produced by the sails. The instability of the _Captain_
does not appear to have been discovered by such calculations as were
made before the vessel went to sea. It was observed, however, that the
ship when afloat was 1 ft. 6 in. deeper in the water than she should
have been—in other words, the freeboard, or side of the ship out of the
water, instead of being 8 ft. high as intended, was only 6 ft. 6 in.,
and such a difference would have a great effect on the stability.

[Illustration:

  FIG. 76.—_H.M.S. Glatton._
]

The turret system has been applied to other ships on quite a different
plan. Of these the _Glatton_ is one of the most remarkable. Her
appearance is very singular, and totally unlike that which we look for
in a ship, as may be seen by an inspection of Fig. 76, page 162. The
_Glatton_, which was launched in 1871, is of the _Monitor_ class, and
was designed by Mr. E. J. Reed, who has sought to give the ship the most
complete protection. With this view the hull is covered with iron plates
below the water-line, and the deck also is cased with 3 in. iron plates,
to resist shot or shell falling vertically. The base of the turret is
shielded by a massive breastwork, which is a peculiarity of this ship.
The large quantity of iron required for all these extra defences has, of
course, the effect of increasing the immersion of the vessel, and
therefore of diminishing her speed. The freeboard when the ship is in
ordinary trim is only 3 ft. high, and means are provided for admitting
water to the lowest compartment, so as to increase the immersion by 1
ft., thus reducing the freeboard to only 2 ft. when the vessel is in
fighting trim, leaving only that small portion of the hull above water
as a mark for the enemy. The water ballast can be pumped out when no
longer needed. The _Glatton_ is 245 ft. long and 54 ft. broad, and she
draws 19 ft. of water with the freeboard of 3 ft., displacing 4,865 tons
of water, while, with the 2 ft. freeboard, the displacement is 5,179
tons. This ship cost £210,000. Mr. Reed wished to construct a vessel of
much larger size on the same plan—a proposal to which, however, the
Admiralty did not then consent. The _Glatton_ is, nevertheless, one of
the most powerful ships of war ever built, and may be considered as an
impregnable floating fortress. Above the water-line the hull is covered
with armour plates 12 in. thick, supported by 20 in. of teak backing,
and an inner layer of iron 1 in. thick. Below the water-line the iron is
8 in. thick, and the teak 10 in. The revolving turret carries two 25–ton
guns, firing each a 600 lb. shot, and is covered by a massive plating of
iron 14 in. in thickness. Besides this the base of the turret is
protected by a breastwork rising 6 ft. above the hull. This breastwork
is formed of plates 12 in. thick, fastened on 18 in. of teak. The turret
rises 7 ft. above the breastwork, and therefore the latter in no way
impedes the working of the guns. The _Glatton_ has a great advantage
over all the other turret ships in having a perfectly unimpeded fore
range for her guns, for there is no mast or other object to prevent the
guns being fired directly over the bow. There are no sails, the mast
being intended only for flying signals and hoisting up boats, &c. The
hull is divided by vertical partitions into nine water-tight
compartments, and also into three horizontal flats—the lowest being
air-tight, and having arrangements for the admission and removal of
water, as already mentioned. The stem of the ship is protruded forwards
below the water for about 8 ft., thus forming a huge ram which would
itself render the _Glatton_ a truly formidable antagonist at close
quarters even if her guns were not used. The engines are capable of
being worked up to 3,000 horse-power, giving the ship a speed of 9½
knots per hour, and means are provided for turning the turret by steam
power. The turret can be rotated by manual labour, requiring about three
minutes for its complete revolution, but by steam power the operation
can be effected in half a minute. The commander communicates his orders
from the pilot-house on the hurricane deck to the engine-room,
steering-house, and turret, by means of speaking-tubes and electric
telegraphs. The _Glatton_ was not designed to be ocean-going, but is
intended for coast defence.

[Illustration:

  FIG. 77.—_H.M.S. Thunderer._
]

The British navy contains two powerful turret-ships constructed on the
same general plan as the _Glatton_, but larger, and capable of steaming
at a greater speed, and of carrying coal for a long voyage. These sister
ships are named the _Devastation_, Fig. 69, and the _Thunderer_, Fig.
77. The _Thunderer_ has two turrets and a freeboard of 4 ft. 6 in. Space
is provided for a store of 1,800 tons of coal, of which the _Glatton_
can carry only 500 tons. The vessel is fitted with twin screws, turned
by two pairs of independent engines, capable of working up to 5,600
horse-power, and she can steam at the rate of 12 knots, or nearly 14
miles, an hour. With the large supply of coal she can carry, the
_Thunderer_ could make a voyage of 3,000 miles without re-coaling.
Though the freeboard of the heavily-plated hull is only 4 ft. 6 in., a
lighter iron superstructure, indicated in the figure by the light
shading, rises from the deck to the height of 7 ft., making the real
freeboard nearly 12 ft. This gives the ship much greater stability, and
prevents her from rolling heavily when at sea. The length is 285 ft. and
the width 58 ft., and the draught 26 ft. The hull is double, the
distance between the outer and inner skins of the bottom being 4 ft. 6
in. The framing is very strong and on the longitudinal principle, and
the keel is formed of Bessemer steel. Each turret is 24 ft. 3 in. in
internal diameter, and is built with five layers of teak and iron.
Beginning at the inside, there is a lining of 2⅝ in. iron plates; then 6
in. of teak in iron frames, arranged horizontally; 6 in. of armour
plates; 9 in. of teak, placed vertically; outside of all, 8 in. armour
plates. Each turret carries two Fraser 35–ton guns, rifled
muzzle-loaders. The turrets revolve by hand or by steam-power. There are
no sails, and thus a clear range for the guns is afforded fore and aft.
The bases of the turrets are protected by the armoured breastwork, of
which a portion is seen in the figure in advance of the fore turret.

Another very powerful ship of war, which possesses some special
features, is represented in the diagram on page 165, Fig. 78. This
vessel, named the _König Wilhelm_, was built at Blackwall for the
Prussian Government by the Thames Ironworks and Steam Shipbuilding
Company, from designs by Mr. Reed. Her length is 365 ft., width 60 ft.;
burthen, 6,000 tons; displacement, 8,500 tons. She is framed
longitudinally, that is, girders pass from end to end, about 7 ft.
apart, and the stem projects into a pointed ram. In this case also the
hull is double; there is, in fact, one hull within another, with a space
of 4½ ft. between them. The armour plates are 8 in. in thickness, with
10 in. of teak backing; but on the less important parts the thickness of
the iron is reduced to 6 in., and in some places to 4 in. This ship has
a broadside battery, and there are no turrets, but on the deck there
are, fore and aft, two semicircular shields, formed of iron plates and
teak, pierced with port-holes for cannon, and also with loop-holes for
muskets. From these a fore-and-aft fire may be kept up. The ship is
fully rigged, and has also steam engines of 7,000 horse-power, by
Maudslay and Co. Her armament consists of four three-hundred-pounders,
capable of delivering fore-and-aft as well as broadside fire, and
twenty-three other guns of the same size between decks. These guns are
all Krupp’s steel breech-loaders.

[Illustration:

  FIG. 78.—_The König Wilhelm._
]

[Illustration:

  FIG. 78_a_.—_The “Victoria” leaving Newcastle-on-Tyne._
]

The great contest of armour plates _versus_ guns has already been
alluded to, and to the remarks then made it may be added that, while on
the one hand, guns weighing 110 tons are mounted in turrets, ships are
already designed with 18 in. and even 20 in. of steel armour plates. It
would be very difficult to predict which side will sooner reach the
limit beyond which increase of size and power cannot go. The gradual
increase of thickness of plating, attended by increased weight of guns,
projectiles, and charges of powder, may be illustrated by stating in a
condensed form a few details of some ships, as regards the thickness of
armour, and its resisting power, which is nearly in proportion to the
square of its thickness; and also some particulars respecting the guns
originally carried by those ships.

 ┌──────────────┬──────────┬──────────┬──────────┬──────────┬──────────┐
 │              │_Warrior._│  _Her-   │_Glatton._│  _Thun-  │  _Vic-   │
 │              │          │ cules._  │          │ derer._  │ toria._  │
 ├──────────────┼──────────┼──────────┼──────────┼──────────┼──────────┤
 │Date when     │   1861   │   1868   │   1872   │   1877   │   1889   │
 │  completed   │          │          │          │          │          │
 │Thickness of  │    4½    │    9     │    12    │    14    │    18    │
 │  iron plating│          │          │          │          │          │
 │  in inches   │          │          │          │          │          │
 │Relative      │    20    │    81    │   144    │   196    │   324    │
 │  resisting   │          │          │          │          │          │
 │  power of    │          │          │          │          │          │
 │  plating     │          │          │          │          │          │
 │Guns carried  │Cast iron,│ Wrought  │ Wrought  │ Wrought  │  Steel,  │
 │              │  smooth  │  iron,   │  iron,   │  iron,   │  Rifled  │
 │              │   bore   │  rifled  │  rifled  │  rifled  │          │
 │Weight of guns│    4¾    │    18    │    25    │    35    │   111    │
 │  in tons     │          │          │          │          │          │
 │Charge of     │    16    │    60    │    70    │   120    │   960    │
 │  powder in   │          │          │          │          │          │
 │  lbs.        │          │          │          │          │          │
 │Weight of     │    68    │   400    │   600    │   700    │  1,800   │
 │  projectiles │          │          │          │          │          │
 │  in lbs.     │          │          │          │          │          │
 │Destructive   │   452    │  3,863   │  5,165   │  8,404   │  56,000  │
 │  power of    │          │          │          │          │          │
 │  projectiles │          │          │          │          │          │
 │  in foot-tons│          │          │          │          │          │
 └──────────────┴──────────┴──────────┴──────────┴──────────┴──────────┘

One of the latest additions out of the thirty or forty armoured ships
that have been added to the British Navy since the preceding pages were
written is included in the above table for the sake of comparison. Our
ironclad fleet now includes vessels protected and armed in many
different ways. Some have the protective armour extended continuously
along the water-line, others have it for only a greater or less part of
their length. The armaments are also very diverse as to the size of the
guns and the way in which they are mounted. A few carry one or two of
the huge 110–ton gun mounted in massive revolving turrets; others have
their guns in central batteries, or in _barbettes_, and others again are
arranged as broadside ships; while these plans are also variously
combined so as to form a great number of different types. In the ships
built within the last 15 years, steel has been almost invariably used
instead of iron for the armour-plating. A great increase of speed has
been obtained in late years. The largest British armoured ships yet
launched have displacements between 10,000 and 12,000 tons, but another
class of first-rate line-of-battle ships of still greater size is in
process of construction, and of these it is estimated that four will be
completed in 1893. They are all of the same design and armament, and
will have a displacement of 14,150 tons, a length of 380 feet, and a
breadth of 75 feet. The armour plates at the sides will be 18 inches
thick. Each ship will carry four 67–ton breech loading rifled guns, ten
6–inch quick firing guns, and 18 other smaller guns, also quick firing.
These vessels are expected to realize a speed of about 20 miles per
hour; but this is somewhat less than a few of the heavy ironclads now
afloat have given by actual trial, a rate equal to 21⅓ miles an hour
having been attained by some. Several of our rapid unarmoured cruisers
are able to steam at 25 miles an hour.

Before the close of 1894, the British navy possessed no fewer than eight
of the largest armoured line of battle-ships mentioned in the foregoing
paragraph, each being of 14,150 tons displacement, and having engines of
13,000 horse-power. At the same period there were in course of
construction four ships surpassing even these in tonnage, though of
somewhat less engine-power. Two were building at Portsmouth, to be
called the _Majestic_ and the _Royal George_, whilst the _Jupiter_ was
in progress at Glasgow and the _Mars_ at Birkenhead. All these are very
heavily armoured vessels, each displacing 14,900 tons, provided with
engines of 12,000 horse-power, and a very effective armament of guns.
Among the powerful ships of the navy may now also be noted the _Blake_,
the _Blenheim_, which, although the displacement is only 500 tons
greater than that of _König Wilhelm_, have engines of nearly three times
the power, namely, of 20,000 horse-power. Of large armoured ships,
namely, those of _9,000 tons and upwards_, Great Britain now has afloat
at least fifty; and the advance that has taken place in the size and
power of war-ships during the last twenty years may be inferred by
reference to the foregoing paragraphs giving the dimensions, &c., of the
_Glatton_ and the _Thunderer_, which paragraphs are, for the sake of
comparison, allowed to appear as they did in the first edition (1876) of
this book. Besides these very large armoured vessels, of which the
smallest is nearly twice as big as the largest of twenty-five years ago,
the British navy comprises ships of every size and for every purpose,
and so many of them that their names and classifications would occupy
many pages.

Two recent additions representing new type of ships claim notice before
this article is concluded. These are first the _Terrible_, with a sister
ship the _Powerful_. The former, of which a representation[3] is given
in Plate V., is pronounced, for its size, armour, armament, and speed
taken together, to be the most powerful cruiser in the world. The length
is 538 ft., breadth 71 ft., depth 43 ft., and the displacement is 14,250
tons. A special object in the design of this vessel was high speed, and
she is provided with twin-screws and two engines, the combined effort of
which is equal to 25,000 horse-power. There are forty-eight boilers and
four funnels, the ship being capable of carrying 3,000 tons of coal. The
vessel is built on the lines of the great Atlantic steamers, and the
engines, guns, and magazines are protected by a thick curved armour
deck. The vessel has a speed of 22 knots, or 25⅓ miles per hour. Her
armament consists of two 22–ton guns, twelve 6–in. quick-firing, and
many other smaller machine guns, and she carries besides four submerged
torpedo tubes. A second ship to be noted is amongst those designed
mainly to exceed all other craft in speed, and ranging in tonnage from
3,800 to 4,500. The _Janus_, a torpedo-boat destroyer of this class, was
found, at a recent trial over a measured mile, to attain the then
unexampled speed of 28 knots, or 32¼ miles per hour. But even this has
been beaten by a new torpedo-boat destroyer, built by Messrs. Yarrow at
Poplar for the Russian Government, and launched in August, 1895. This
vessel, within a few hours after leaving the stocks, cut through the
water at the rate of 30·285 knots, or nearly 35 miles, per hour.

Footnote 3:

  From _Graphic_, 1st June, 1895.

A sad fate befell the _Victoria_, which was one of the heaviest armed of
British ships (_vide_ page 129), when taking part in some naval
manœuvres off Tripoli, on the Syrian coast, where she was the flag-ship
of Admiral Tryon, commander-in-chief of the squadron. On the 22nd June,
1893, in consequence of an inconsiderate order given by the admiral
himself, the _Victoria_ was struck by the formidable ram of the
_Camperdown_ (10,600), and in fifteen minutes turned over and sank in
sight of the whole fleet, carrying down with her the admiral, 30
officers, and 320 men, out of a crew of 600. [1895.]

[Illustration:

  FIG. 78_b_.—_Firing at a floating battery._
]

[Illustration:

  PLATE XI. H.M.S. “TERRIBLE.”
]

[Illustration:

  FIG. 79.—_Krupp’s Works, at Essen, Prussia_.
]



                               FIRE-ARMS.


The invention of gunpowder—or rather its use in war—appears at first
sight a device little calculated to promote the general progress of
mankind. But it has been pointed out by some historians that the
introduction of gunpowder into Europe brought about the downfall of the
feudal system with its attendant evils. In those days every man was
practically a soldier: the bow or the sword he inherited from his father
made him ready for the fray. But when cannons, muskets, and mines began
to be used, the art of war became more difficult. The simple possession
of arms did not render men soldiers, but a long special training was
required. The greater cost of the new arms also contributed to change
the arrangements of society. Standing armies were established, and war
became the calling of only a small part of the inhabitants of a country,
while the majority were left free to devote themselves to civil
employments. Then the useful arts of life received more attention,
inventions were multiplied, commerce began to be considered as
honourable an avocation as war, letters were cultivated, and other
foundations laid for modern science. If such have really been the
indirect results of the invention of gunpowder, we shall hardly share
the regret of the fine gentleman in “Henry IV.”:

              “That it was great pity, so it was,
              That villanous saltpetre should be digged
              Out of the bowels of the harmless earth,
              Which many a good tall fellow had destroyed
              So cowardly.”

We often hear people regretting that so much attention and ingenuity as
are shown by the weapons of the present day should have been expended
upon implements of destruction. It would not perhaps be difficult to
show that if we must have wars, the more effective the implements of
destruction, the shorter and more decisive will be the struggles, and
the less the total loss of life, though occurring in a shorter time.
Then, again, the exasperated and savage feelings evoked by the
hand-to-hand fighting under the old system have less opportunity for
their exercise in modern warfare, which more resembles a game of skill.
But the wise and the good have in all ages looked forward to a time when
sword and spear shall be everywhere finally superseded by the
ploughshare and the reaping-hook, and the whole human race shall dwell
together in amity. Until that happy time arrives—

  “Till the war-drum throbs no longer, and the battle flags are furl’d
  In the Parliament of man, the Federation of the world—
  When the common sense of most shall hold a fretful realm in awe,
  And the kindly earth shall slumber, lapt in universal law,”—

we may consider that the more costly and ingenious and complicated the
implements of war become, the more certain will be the extension and the
permanence of civilization. The great cost of such appliances as those
we are about to describe, the ingenuity needed for their contrivance,
the elaborate machinery required for their production, and the skill
implied in their use, are such that these weapons can never be the arms
of other than wealthy and intelligent nations. We know that in ancient
times opulent and civilized communities could hardly defend themselves
against poor and barbarous races. But the world cannot again witness
such a spectacle as Rome presented when the savage hordes of Alaric
swarmed through her gates, and the mighty civilization of centuries fell
under the assaults of the northern barbarians. In our day it is the poor
and barbarous tribes who are everywhere at the mercy of the wealthy and
cultivated nations. The present age has been so remarkably fertile in
warlike inventions, that it may truthfully be said that the progress
made in fire-arms and war-ships within the second half of the nineteenth
century surpasses everything that had been previously accomplished from
the time gunpowder came into use. Englishmen have good reason to be
proud of the position taken by their country, and may feel assured that
her armaments will enable her to hold her own among the most advanced
nations of the world.

The subject of fire-arms embraces a very wide ground, as will appear if
we consider the many different forms in which these weapons are
constructed in order best to serve particular purposes. Pertaining to
this subject, attention must also be directed to the modern projectiles
and to the newer explosives that have largely taken the place of
ordinary gunpowder. The shot gun, fowling-piece, and sporting rifle
properly come under the head of fire-arms, and in the march of
improvement these forms have most commonly been in advance of military
muskets and rifles, the ingenuity bestowed on all their details being
worthy of admiration. Nevertheless it is to the implements of war that
general interest attaches; for on them depends so much the fate of
battles and the destiny of nations, that whenever any country is engaged
in war the question of arms becomes one of surpassing importance,
enlisting the patriotic instincts of every citizen. Hence in the
following pages our space will be devoted mainly to weapons of war, and
more particularly to those that have been adopted by our own country.

Everyone of course is aware that guns, cannon, and gunpowder are by no
means inventions of the nineteenth century; but there are fewer
acquainted with the fact that rifling, breech-loading, machine guns, and
revolvers were all invented and tried hundreds of years before. The
devices by which some of these ideas were sought to be realised in past
ages appear to us in some instances very primitive, not to say childish,
when compared with modern work: but it must be remembered that nearly
all the appliances required for producing such weapons had themselves to
wait for their invention until the nineteenth century; such, for
instance, as the steam-hammer, powerful and accurate tools, refined
measuring implements, material entirely reliable such as the new steel,
and also scientific investigations of all the conditions involved. The
military fire-arms are of so many different forms and patterns that we
can deal here with but a selection from the various services. If a rough
classification had to be made, the most obvious distinction would be
between the weapons the soldier carries in his hands (small-arms) and
those which are mounted on some kind of carriage and discharge
projectiles of much greater weight (ordnance). Ordnance again includes
guns mounted on forts, carried in ships, or taken with an army into the
field, in each case coming into action under different conditions.
Partaking somewhat of the nature of both field-guns and of small-arms
are the machine guns, of which the French mitrailleur was the first
example, afterwards developing into much more effective weapons in the
hands of Gatling, Gardner, Nordenfelt, Maxim, and Hotchkiss.

As much will have to be said about _rifling_ the bores of muskets and
cannon, we may here explain the nature and object of this device. The
projectiles used in all guns down to comparatively recent times were
almost invariably of spherical form, and could indeed scarcely be
otherwise with smooth-bore weapons. As the diameter of the shot would
necessarily be something less than that of the bore of the barrel, a
considerable loss of power would result from the escape of the powder
gases between the shot and the barrel, which escape is known as
_windage_. Another disadvantage of the spherical projectile is that for
the same weight of metal the air offers a greater resistance to its
passage, and consequently checks its speed more quickly than that of any
other circular form; for the air resistance is proportional to the
square of the diameter, and therefore if we take a ball of 1 in.
diameter and a cylinder of 1 in. in length, each having the same weight
of metal, the diameter of the cylindrical shot will be a little more
than four-fifths of an inch, and the air resistance to the ball will be
exactly half as much again as to the cylinder, that is, in the
proportion of 3 to 2. Again, the passage of the spherical shot within
the barrel of the gun will not be in a straight line, but in a series of
rebounds from side to side, and its direction on leaving the muzzle will
depend upon which part of the bore it just before impinges on, as from
that it will also take a rotatory “twist” that will in part determine
its path through the air.

Now if an elongated projectile were fired from a smooth-bore gun, its
course through the air would be erratic to a degree impossible to the
spherical shot, for it would turn end over end with deviations that
would make aiming impracticable. But if the elongated projectile is made
to spin rapidly enough about its longitudinal axis, it flies through the
air quite steadily, the axis of rotation remaining parallel to that of
the gun throughout the whole flight. The steadiness due to rapid
rotation has familiar examples in spinning tops, in gyroscopic tops, in
the way arrows are feathered so that the air may cause them to revolve
axially, and so on. The axial rotation of the projectile is effected by
ploughing out in the cylindrical barrel of the gun a number of spiral or
twisting grooves, which the projectile is compelled to follow as it
travels along the barrel, either by means of corresponding protuberances
formed upon its surface in the first instance, as in Jacob’s bullets, or
by studs let into it, as in the studded shots and shells for ordnance
which constituted at one time the regulation plan adopted by the British
Government; or otherwise by making the force of the explosion expand
some portion of the projectile in such a manner that this portion shall
completely fill up the grooves, thus preventing windage, and causing the
projectile to follow the twist of the grooves. This is the more general
method, especially since the adoption of breech-loading. The Lancaster
rifling, and that advocated by Whitworth, are the same in principle, but
differ in appearance, from the section of the barrel being made in the
one case oval, in the other hexagonal or polygonal, but with the twist
necessary to produce rotation.

Incident to the discharge of all fire-arms, great and small, is a
phenomenon of which we have to speak, because it is one which in the
mounting of heavy ordnance especially has to be taken into account. And
as it also illustrates in a very direct way one of the most general laws
of nature, while people often have very vague and erroneous ideas of its
cause and operation, it deserves the reader’s attention. In gunnery it
is called the _recoil_, and is familiar to anyone who has ever fired a
pistol, fowling-piece, or rifle, in the kick backwards felt at the
moment of the discharge. This law is in operation whenever the condition
of a body in respect to its rest or motion is changing. That is,
whenever a body at rest has motion given to, or if when already moving
it is made to go faster or slower, or to stop, or when the direction of
the motion is changed from that in a straight line. Now although these
changes or actions are frequently occurring before our eyes, the
operation in them of Newton’s third law of motion does not generally
present itself to common observation. This third law was stated by Sir
Isaac Newton thus:—“To every action there is always an opposite and
equal reaction.” Now the expanding gases due to the gunpowder explosion
press the bullet forwards and the barrel (with its attachments)
backwards, with the same pressure in both cases, but at the end of the
bullet’s passage along the bore the same velocity is not imparted to the
two bodies, because the same pressure acting for the same time on bodies
of unequal _mass_ always produces velocities that are inversely
proportional to the _masses_. The reader should try to acquire this
conception of _mass_, remarking that it is a something quite distinct
from that of _weight_. A given lump of metal, for instance, would have
exactly the same _mass_ in any part of the universe, whereas its weight
would depend upon its position; as, for instance, at the distance from
the earth of the moon’s orbit, it would _weigh_ only as 1/3600th part of
its weight at the earth’s surface, and if it could be carried to the
very centre of the earth it would there have no weight at all. Though
the lump of metal will have different weights at different parts of the
earth’s surface, it has been found (by experiment) that the weights of
bodies at any one place are proportional to their masses. Therefore the
same numbers that express the weights of bodies might also express their
masses; but for certain good reasons these quantities are referred to
different units. In England a piece of metal weighing 32 lbs. under
standard conditions is said to have mass = 1; and so on. As with the
_same pressure acting for the same time_, the velocities imparted are
inversely proportional to the masses, it follows that the number
expressing the velocity multiplied by that representing the mass in each
such case of action and reaction will give the same product, or in other
words the _amount of motion_ (momentum) will be the same. This is what
Newton meant by saying the reaction is _equal_ to the action. We may now
by way of illustration calculate the velocity of recoil of a rifle under
conditions similar to those that might occur in practice. Let us suppose
that the rifle, including the stock and all attachments, weighs 10 lbs.,
and that from it is fired a bullet weighing one-sixteenth of a pound,
with a velocity at the muzzle of 1,200 ft. per second. To obtain the
amount of motion or the momentum, we should here multiply the number
expressing the _mass_ of the bullet by 1,200, but for our present
purpose the weight numbers may be used for the sake of simplicity;
therefore 1/16 x 1,200 = 75 will represent (proportionately) the forward
momentum of the bullet, and according to Newton’s law the backward
momentum of the rifle will be, on the same scale, 75 also. We must
therefore find the number which multiplied by 10 will give 75, and this
obviously is 7·5. That is as much as to say that at the instant the
bullet is leaving the muzzle, the rifle itself, _if free to move_, would
be moving backward at the speed of 7½ ft. per second. Observe that this
result would be the same if the rifle were fired where weight is
non-existent; nor is the recoil due, as sometimes is erroneously
supposed, to the resistance of the air to the passage of the bullet
along the barrel, for even if the air were abolished, the recoil, so far
as due to the masses and velocities, would remain the same, as indeed
may be seen from the fact of our calculation taking no account of the
bore of the rifle or of the shape of the bullet, circumstances of the
utmost importance where atmospheric resistance is concerned.

The foregoing calculation however involves an assumption not in exact
conformity with actual conditions, by taking for granted that the
_centre of gravity_ of the rifle is in the line of the axis of the
barrel, while in fact this centre is almost always lower, and therefore
the kick of the recoil acts in part as a turning-over push, tending to
tilt up the muzzle of the gun, and for that reason the firer must hold
the weapon very firmly or he will miss his aim. When such a rifle as we
have supposed is fired, say from the shoulder, it would follow from the
above calculation that the backward kick of the recoil is equivalent to
a blow from a 10–lb. weight moving at the speed of 7½ ft. per second.
This would certainly be a very uncomfortable experience, but the
backward momentum must be met somehow. We have supposed that the gun is
free to move, but we know the firer presses it firmly against the
muscles of his shoulder, and the stock of the gun is spread out and
provided with a smooth hollow heel plate, so that any pressure from it
is felt as little as possible, especially as the muscle against which it
is applied acts as an elastic pad. With the rifle thus firmly held we
may regard the marksman and his rifle as forming only _one mass_, and
the centre of gravity of this being now much below the axis of the
barrel, the effect of the recoil tends to overthrow the man backwards;
but he learns to resist this by standing firmly, so that the elasticity
of his whole frame comes into play; and besides this, the mass factor of
the momentum being now so large, the velocity factor becomes
comparatively insignificant.

Although the momenta of gun and projectile are, according to Newton’s
law, _equal_ and opposite, the case is very different with regard to
their _energies_, or powers of doing work, for the measure of these is
jointly mass and _the square of the velocity_. The _energy_ (_vis viva_)
of a body of weight in pounds = W, moving with the velocity of v feet
per second is always Wv^2/64·4, that is, it will do this number of
foot-lbs. units of work before it comes to rest. It would require too
much space to demonstrate and fully explain here what this means, but
the reader may refer to our index under the entries “Energy” and “Work,”
or to any modern elementary treatise on dynamics. If the calculation be
made of the energies of the ball and of the rifle due to our calculated
velocities of recoil, it will be found that that of the ball is 160
times greater than that of the other, and the ball possesses this energy
in a much smaller compass.

[Illustration:

  FIG. 80.—_Trajectory of a Projectile._
]

The course or track of a projectile through the air after it leaves the
gun is called the _trajectory_, and this has been studied both
experimentally and theoretically, with interesting results. Assuming
that the shot passed through empty space, or that the air offered no
resistance to its passage, it would be very easy to trace the path of a
projectile. Let us suppose that Fig. 80 represents a gun elevated at a
high angle. The moment the projectile leaves the muzzle, gravity begins
to act upon it, causing it to move vertically downwards with
ever-increasing velocity until it finally reaches the ground; the onward
uniform movement parallel to the axis of the piece being continued all
the time. We could find the position of the projectile at the end of
successive equal periods of time by drawing a straight line AC, a
prolongation of the axis of the piece, or a line of the same
inclination; on this we mark off equal distances representing by scale
the velocity of the projectile per second, the points B, C, D, E being
the positions the projectile would be in at the end of each successive
second if gravity did not act. In order to bring the diagram within
moderate compass, we suppose the projectile to have only the small
velocity of 115 ft. per second. At the end of the first second it would
be at B, but now suppose that gravity is allowed to act for one second,
it would at the end of that time have fallen 16 ft. vertically below B
and have arrived at _b_. Similarly we may set off by scale on verticals
through C, D, and E distances representing 64 ft., 144 ft., and 256 ft.
respectively. Because, for instance, the ball, without gravity acting,
would at the end of 3 seconds be at D, where we may suppose its course
arrested and gravity then allowed to act for 3 seconds to pull the ball
down from its position of rest at D; at the end of this period, gravity
alone acting, its position would be 144 ft. vertically below D, because
gravity pulls a body that distance in 3 seconds, and the actual position
3 seconds after the ball had left the muzzle would be at _d_, after it
had described the curved path A, _b_, _c_, _d_. Supposing _d_ to be the
highest point of the trajectory, another 3 seconds would bring the ball
along a downward curve, and at the end of 6 seconds from the discharge
it would be at a point on the same level as A. Now the complete curve
would be symmetrical on each side of a vertical line through its highest
point, and it would be in fact a regular _parabola_ with its vertex at
_d_.

The foregoing presupposes that the air offers no resistance to the
passage of the projectile through it. The fact however is quite
otherwise, for no sooner does the projectile begin its flight than its
velocity is constantly diminished by the air’s resistance. Now this
resistance is complex, depending upon a number of different conditions,
the effect of which can be taken into account only by extremely complex
calculations. Obviously it will vary according to the area of the
section presented by the projectile to the line of its flight, and again
by the shape of its front, for a pointed shot will cleave the air with
less resistance than one with a flat front. Then the density of the air
at the time will also enter into the calculation. The mass of the
projectile and also its velocity, upon which depend its _vis viva_,
energy, or power of overcoming resistance in doing work, will also have
to be considered. Most complex of all is the law, or rather laws (_i.e._
relations), which connect the air resistance with the velocity; for this
relation no definite expression has been found. It is a function of the
velocity (known only by experiment under defined conditions), and
varying with the velocity itself. Thus for velocities up to 790 ft. per
second, it is a function (determined experimentally) of the second power
or square of the velocity; between 790 ft. per second and 990 ft. per
second the law of resistance is changed and becomes a function of the
third power of the velocity; between 990 ft. and 1,120 ft. velocity the
law again changes and is related to the sixth power of the velocity;
between 1,120 ft. and 1,330 ft. the resistance is again related to the
third power of the velocity; and with higher speeds than that last named
it is again more nearly related to the square of the velocity. It will
be seen that to calculate the path of a projectile is really a very
difficult mathematical problem, and indeed one which can be solved only
approximately when all the known data are supplied.

The air resistance to the motion of a projectile is much greater than
before trial would be supposed. Let us take an experiment that has
actually been recorded, in which a bullet three-quarters of an inch in
diameter, weighing one-twelfth of a pound, was found to have a velocity
of 1,670 ft. per second at a distance of 25 ft. from the gun, and this
50 ft. farther was reduced to 1,550 ft. per second. Now if the reader
will calculate, according to the formula we have given above, the
_energy_ due to the bullet’s velocity at these points, he will find it
must have done 500 foot-lbs. units of work in traversing the 50 ft., and
as this could have been expended only in overcoming the resistance of
the air, we learn that this last must have been equivalent to a mean or
average pressure of 10 lbs. thrusting the bullet backwards.

It will be interesting to compare the difference in the trajectory of a
projectile under defined conditions, worked out with the air resistance
taken into account, compared with the trajectory when the air is
supposed to be non-existent. We find an example of the former problem
fully worked out by many elaborate mathematical formulæ in Messrs. Lloyd
and Hadcock’s treatise on Artillery. The problem is thus stated:—“An
11–in. breech-loading howitzer” (a howitzer is a piece of ordnance used
for firing at high angles) “fires a 600–lb. projectile with an initial
velocity of 1,120 foot-sec. at an elevation of 20°. Find the range, time
of flight, and angle of descent.” We shall calculate these points on the
suppositions adopted with regard to Fig. 80, and with no higher
mathematics than common multiplication and division.

It will have been observed that we supposed two motions that really take
place simultaneously to take place successively and independently: one
in the direction of the line of fire, due to the initial velocity; the
other vertically downwards, due to the action of gravity, the final
result being the same. This affords an excellent illustration of another
of Newton’s laws of motion, and should be considered by the reader in
this connection. The law itself admits of being stated in various ways,
as thus:—“Whenever a force acts on a body, it produces upon it exactly
the same change of motion in its own direction, whether the body be
originally at rest or in motion in any direction with any velocity
whatever—whether it be at the same time acted on by other forces or
not.” Or again: “When two forces act in any direction whatever on a body
free to move, they impress upon it a motion which is the _superposition_
(or compounding) of those that it would receive if each force acted
separately.” The law is given also in the following form (Thomson and
Tait):—“When any forces act on a body, then, whether the body be
originally at rest or moving with any velocity and in any direction,
each force produces in the body the exact change of motion which it
would have had had it acted singly on the body originally at rest.” In
all of these expressions the word “forces” is used, and a very
convenient word it is, but it may be noted in passing, nothing but a
word; for it stands for no real self-existing things, since, apart from
observed changes of motion in bodies, forces for us have no existence.
Nevertheless, it is useful for the sake of abbreviating statements about
changes of motion, to regard these actions as produced by imaginary
agents—imagined for the time and for this purpose, and therefore vainly
to be sought for in the realm of reality.

[Illustration:

  FIG. 81.—_Diagram._
]

In dealing with the trajectory of the howitzer’s projectile through
airless space we have no concern with its diameter nor with its weight.
We use the little diagram, Fig. 81, to represent the motions,—_c_ being
a horizontal line, _a_, a vertical one, the angle at B is therefore a
right angle, and we assume that at A to be 20°. Now, the most elementary
geometry teaches us that every triangle having these angles will have
the lengths of its sides in the same invariable proportions one to
another whatever may be the size of the triangle itself, and it has been
found convenient to calculate these proportions once for all, not merely
for angle 20°, but for every angle up to 90°. Besides this, distinct
names have been given to the proportions of every side of the triangle
to each of the other two sides. Thus in the triangle before us, if we
take _a_, _b_, and _c_ to represent the numbers expressing the lengths
of the sides against which they are placed, _a_ divided by _b_, that is
_a_ ÷ _b_, or _a_/_b_, is called the _sine_ of angle 20°, while _c_/_b_
is named the _cosine_ of that angle, etc. These therefore are _numbers_
which are given in mathematical tables, and we find by these that _sine_
20° = 0·3420201, and _cosine_ 20° = 0·9396926, and these with the
initial velocity give us all the data we require. We may first find the
_time_ the projectile would take to reach the ground level, or strictly
that of the muzzle of the gun at B. Taking _t_ to stand for this time,
we know that AC = 1,120 × _t_, but CB will be the distance that a body
would fall from rest at C by the influence of gravity in that same time,
_t_, and it is known by experiment that this distance is 16·1 feet
multiplied by the _square_ of the time from rest in seconds. We have now
therefore the length of the line CB, and put _a_/_b_ = CB/AC = (16·1 ×
_t_^2)/(1,120 × _t_) = _sine_ 20° = ·3420201, and dividing numerator and
denominator by _t_ and multiplying the above 3rd and 5th expressions by
1,120, we have

                 16·1 × _t_ = 1,120 × ·3420201

                              1,120 × ·3420201
          and therefore _t_ = ———————————————— = 23·7927 secs.
                                    16·1

Having obtained the time, it will be easy to work out the lengths _b_
and _a_ as 26,648 ft. and 9114·1 ft. respectively; and as _c_/_b_ =
_cosine_ 20°, we have _c_ = 26,648 × ·9396926 = 25040·8 ft., which is
the _range_. The trajectory will be a curve (parabola) symmetrical on
each side of a vertical line half-way between A and B, and the length of
this line within the triangle will be equal to half of _a_, and in half
of 23·7927 seconds the projectile, supposed to move only along the line
AC, would reach the point where this vertical axis intersects AC. If
during this half-time it had been falling from rest at the same
intersection, it would have reached a point below by a space just one
quarter of CB (the spaces fallen through being as the _squares_ of the
times), and therefore at this its highest point its distance above AB
would also be one quarter the length of _a_ = 2278·525 ft., which
distance is called the _height_ of the trajectory; and the descending
curve being in every respect symmetrical to the ascending branch, the
angle at which this would be inclined to AB would be 20°, but in the
opposite direction to BAC, while the velocity would be the same as at A.
We may now compare these results with those calculated when the air
resistance is taken into account:—

 ┌─────────────────────────────────┬───────────┬───────────┬───────────┐
 │                                 │Without air│With air   │           │
 │                                 │resistance.│resistance.│Difference.│
 ├─────────────────────────────────┼───────────┼───────────┼───────────┤
 │Time of descent                  │23·7927    │22·61 sec. │–1·18 sec. │
 │                                 │secs.      │           │           │
 │Angle of descent                 │20°        │23° 49´    │+3° 49´    │
 │Velocity of descent              │1120       │868·8      │–251·2     │
 │                                 │foot-secs. │foot-secs. │f.-s.      │
 │Range                            │25040·8 ft.│20,622 ft. │–4418·8 ft.│
 │Height of trajectory             │2278·5 ft. │1989 ft.   │–288·5 ft. │
 └─────────────────────────────────┴───────────┴───────────┴───────────┘

With the air resistance the trajectory will no longer be a symmetrical
curve: its highest point, instead of being on the vertical line midway
between A and B, will be on one 1,050 ft. nearer to B than to A, and the
descending branch will be steeper than the ascending. The total time, it
will be observed, is less, although the final, and therefore the mean,
velocity, is also less; but this shortening of the time is due to the
trajectory itself being much less in length. The range of the projectile
is decreased by 4,418 ft., or 1,473 yards, or more than four-fifths of a
mile. The loss of velocity at the descent is very notable, and the
reader will find it interesting to calculate the corresponding loss of
energy by the formula already given.

The reader should now easily understand that the projectile from a rifle
or gun discharged horizontally through airless space at the height of
16·1 ft. above a level plain would strike the ground in one second at a
range or distance from the gun exactly equal to the initial velocity, or
if the gun were on a tower and its axis 64·4 ft. above the plain, the
range would then be 2V. It will be seen therefore that, corresponding to
the range intended, there must be in general a certain inclination given
to the axis of the piece in aiming, and this is done by means of the
_sights_, one of which near the muzzle is usually fixed, while that next
the breech is adjustable by sliding along an upright bar, which is
graduated so that the proper elevation may be given for any required
range. These graduations are made from experiments, and of course have
reference only to some standard quantity and quality of ammunition and a
standard of weight, shape, and material in the projectile. Sometimes
large pieces of ordnance are laid by elevation in degrees, etc., marked
on their mounting, the angles being taken from a table prepared for that
particular gun and ammunition, from experiments at different ranges.

After these generalities about fire-arms we may enter upon certain
particulars about the construction of some varieties, beginning with


                         _THE MILITARY RIFLE._

[Illustration:

  FIG. 82.—_Muzzle-loading Musket and Rifles_ (_obsolete patterns_).

  A. Brown Bess and Bayonet; B. Brunswick Rifle; C. Enfield Rifle and
    Bayonet.
]

In Fig. 82 are represented the muzzle-loading musket and muzzle-loading
rifles which formed the regulation weapons of the British infantry from
the beginning of the century up to the year 1864. Somewhat slow in its
earlier stages was the development of the modern military rifle from the
old smooth bore musket with its flint-lock, which was the ordinary
weapon of the British and other armies up to nearly the middle of this
century. Partly, perhaps, owing to the inherent conservatism of
government departments, and partly to the very serious outlay involved
in arming all the troops of a nation with a new weapon, it has happened
that many improvements in small arms were in use as applied to sporting
guns, long before they were adopted in the regulation weapons of armies.
The advance towards the modern arm of precision has been made along all
the several directions that converge in the latest product, and it may
be said that the most obvious of these are spiral rifling,
breech-loading, and improved ammunition. The improvements in any one of
these particulars would have been of little advantage unless the others
had been kept in line with it. How long antiquated systems may continue
in use may be illustrated by the case of the flint-lock, which was
retained in the British army from the time it superseded the old
match-lock, in the latter part of the seventeenth century, down to
almost the middle of this present nineteenth. It is quite possible that
not a few readers still in their fifties may never have seen a
flint-lock outside of a museum, yet this was the firing apparatus of the
weapon that used to be affectionately known to our soldiers as “Brown
Bess,” and that for a century and a half continued the regulation arm of
British troops helping Wellington to win his victories, and superseded
by the percussion musket only in 1842. The “Brown Bess” of the earlier
part of the century had a smooth-bore barrel of three-quarters of an
inch diameter (0·753 inch), and 39 inches long; this musket weighed,
with its bayonet, 11 lbs., 2 oz. The bullet was spherical, and made of
lead, in weight a little over one ounce. The diameter of the bullet was
slightly smaller than the bore of the barrel, because a closely fitting
ball could not be used, on account of the great force required to push
it home with a ram-rod. The bullet was therefore wrapped in loosely
fitting material, called a “patch,” and this made the gun easy to load,
even when the barrel was “fouled” by the solid residues that always
remain after the explosion of gunpowder. “Brown Bess” was credited with
a range of 200 yards, but its want of accuracy was such that the soldier
was directed not to fire until he could see the whites of the enemies’
eyes. But in 1800 one or two British regiments were armed with the
muzzle-loading rifle known as Baker’s, and again in 1835 these were
provided with the _Brunswick rifle_. These regiments afterwards became
known as the Rifle Brigade. The bullets in both cases were spherical,
and as the earlier pattern had a seven-grooved barrel, there was so much
difficulty in introducing the bullets into the muzzles that mallets had
to be used. The bullet of the Brunswick rifle was encircled by a
projecting band, which fitted into two rather deep grooves diametrically
opposite to each other in the barrel. This bullet, wrapped in some
slightly greased material, could be readily dropped into the muzzle, and
rammed home without difficulty. Moreover, whereas in Baker’s rifle the
grooves made only a quarter of a turn in the length of the barrel, the
grooves of the Brunswick rifle made more than one complete turn. This
was so much an improvement on “Brown Bess” that the effective range was
more than doubled. For the rank and file of the infantry regiments the
flint-lock smooth-bore musket was, however, the regulation weapon until
1842, when it was superseded by the percussion musket. The
percussion-cap is now comparatively little used, as, since the
introduction of cartridges containing their own means of ignition, it is
rapidly becoming a thing of the past. The copper percussion-cap, in the
form it still retains, was invented about 1816, and was universally
adopted for sporting-guns a long time before it was used for the
military weapon. In 1842 the percussion musket was definitely adopted as
the weapon of the British army, but up to that date the flint-locks
still continued to be made at Birmingham.

The barrel of the percussion musket then issued was shortly afterwards
rifled, when about the year 1852 the Minié system was adopted, and the
Government awarded to M. Minié, a Frenchman, the sum of £20,000 for the
bullet he had invented. What the meaning of this improvement was may now
be explained, and we must begin by mentioning the various forms of
grooving, or, at least, such forms as found some approval during the
present century, for grooved barrels had been tried long before. At
first the grooves appear to have been intended merely to receive the
fouling, and these were often made without any twist or spiral, but
parallel to the axis of the barrel. The grooves are hollow channels of
greater or less depth, and of various forms; square, triangular,
rounded, or of such a form that the inner line of a section of the
barrel would present the form of a ratchet wheel. The numbers of the
grooves made use of have varied between two and twelve, or more, and
different rates of twist, or numbers of turns of the spiral in the
length of the barrel have been resorted to, these ranging from half a
turn to twelve turns. The Brunswick rifle had been found wanting in
accuracy, when at length in 1846 General Jacobs proposed the adoption of
the conical bullet with projecting spiral ridges which fitted into
grooves cut in the rifle barrel. The difficulty in using muzzle-loading
rifles consisted in the force required to ram down the bullet, which had
to adapt itself to the grooves, and fill them up so that the gases due
to the explosion of the powder should not escape. If the bullet simply
dropped into the bore of the rifle easily, it did not effectually fill
the grooves, which then became channels of this _windage_, and if, on
the other hand, the leaden bullet was made to fill the grooves from the
muzzle, great force was required, and the time and effort expended in
ramming the missile home, detracted enormously from the efficiency of
the rifle as a military weapon. Mr. Lancaster produced rifles having a
slightly oval, instead of a circular, bore, making, of course, the
necessary twist within the barrel. A bullet of the corresponding
section, but nearly globular, much as if the projecting belt of the
Brunswick bullet had been laterally extended to its opposite poles,
could be easily dropped in at the muzzle, without force being required
to make it take grooves, the barrel being internally smooth throughout.
It was, however, soon found that this easy-fitting ball allowed a
considerable amount of _windage_, and the Minié system was definitely
adopted, in which advantage was taken of a fact observed some years
before by a French artillery officer, who found that an elongated leaden
bullet, if hollowed out at the base, was so expanded by the pressure of
the powder gases that the material was forced into the grooves of a
rifle. Minié made his bullet elongated, pointed in front, and hollowed
out part of its length by a conical space, the widest part of which was
at the base, and was covered by a small iron cup, that, when driven
inwards by the pressure of the gases, caused an expansion of the bullet
by which the lead was forced into the grooves of the rifling. But the
forces operating on the base of the bullet would at times cause the iron
cup to cut the bullet in two, and propel the anterior portion only,
leaving the base in the form of a ring clinging to the rifling. The
military authorities had many comparative trials carried out between the
smooth-bore percussion musket and the Minié rifle. The greater accuracy
of the latter may be inferred from the results of practice made by men
firing at a target 6 feet high and 20 feet broad; when at 100 yards
distance, 74 hits out of 100 shots were made from the musket, against 94
from the rifle; and the superiority of the latter, at longer ranges, was
increasingly marked. Thus at 260, 300, and 400 yards the respective
percentages of hits were for the musket 42, 16, 4½, but for the same
ranges the rifle gave 80, 55, 52.

[Illustration:

  FIG. 83.—_The Minié Bullet._
]

Curiously enough, the principle of the expanding bullet had been brought
forward by the late Mr. W. Greener seventeen years before the government
prize was awarded to M. Minié. Mr. Greener’s bullets were of an oval
form, being half as long again as their diameter, with one end flattened
where the lead was excavated in a narrowing hollow nearly through the
bullet. In this opening was inserted the end of a tapering plug of hard
metal, and when the rifle was fired this plug was driven home, and the
lead thus expanded took the grooves, so preventing windage, and giving
range and accuracy; while allowing the piece to be loaded with as much
ease as the smooth-bore musket. The invention, though favourably
reported on by the military authorities at the time, did not receive the
attention it would seem to have deserved. However, in 1857, Mr.
Greener’s claim of priority for the first suggestion of the expanding
bullet was acknowledged by a government award of £1,000.

[Illustration:

  FIG. 84.—_Greener’s Expanding Bullet._
]

Sir Joseph Whitworth, having been invited by the British military
authorities to institute experiments with a view to producing the best
type of rifle, with the help of the most perfect machinery, constructed
the barrels with a polygonal bore, a plan which he had before adopted
for large guns. The barrels were accurately bored out to a hexagonal
section, and experiments were made to find what number of turns in the
twist would give the projectile a sufficient rapidity of rotation to
maintain it during its flight parallel to its axis. It was found that
one turn in 20 inches was sufficient, and the projectile was made by
machinery to fit accurately but easily into the rifled bore, so that it
dropped into its place, and the loading could be expeditiously
performed. The bullet was long, compared with the bore, which was made
smaller than before, and it was found that the explosion caused it to
expand sufficiently to fill up the corners of the hexagon, so that there
was no loss from windage. The accuracy of aim of the Whitworth rifle was
superior to that of any weapon of the kind that had, up to that time,
been produced. When officially tried against the Enfield, its mean
deviation at 500 yards range was only 4½ inches, while that of the
Enfield at the same range was 27 inches. Mr. Whitworth had proved the
advantages of using a small bore, an elongated bullet, and a sharp twist
in the rifling; and it was acknowledged that as a military weapon his
rifle was superior to all other arms of similar calibre that had before
been produced. Some doubt appears to have been entertained, however, as
to whether the mechanical perfection of the trial rifles could be
maintained if they came to be manufactured on the large scale, and also
as whether an adequate supply of the polygonal ammunition would be
procurable when required. The Whitworth rifle was never adopted into the
government service, and soon after these trials in 1857, the adoption of
another type of weapon became imperative, as the results obtained by the
Germans with their needle-gun, demonstrated the enormous advantages of a
breech-loading rifle.

[Illustration:

  FIG. 85.—_The Chassepot Rifle.—Section of the Breech._
]

The French then adopted the Chassepot rifle (so called after its
inventor), which embodied the same principle as the needle-gun, but with
improvements. This arm has a rifled barrel, with a breech mechanism of
great simplicity, which is represented in section in Fig. 85. The piece
marked B corresponds to what is called the “hammer” in the old lock used
with percussion-caps, and the first operation in charging the rifle
consists in drawing out B, as shown in the cut, until, by the spring, C,
connected with the trigger, A, falling into a notch, the hammer, if we
may so term it, is retained in that position. The effect of this
movement is to draw out also a small rod attached to the hammer, and
terminated in front by a needle, about ½ in. long, at the same time that
a spiral spring surrounding the rod is compressed, the spring being
fastened to the front end of the rod, and abutting against a screw-plug,
which closes the hinder end of F, and permits only the rod to pass
through it. The piece F, which is also movable, has projecting from its
front end a little hollow cylinder, through the centre of which the
needle passes, and this little cylinder has a collar, serving to retain
its position, an india-rubber ring surrounding a portion of the
cylinder, and forming a plug to effectually close the rear end of the
barrel. It will be noticed that the cylinder is continued by a smaller
projection, which forms a sheath for the point of the needle. The
movable breech-piece, F, is provided with a short lever, E, by which it
is worked. The second movement performed by the person who is charging
the piece is to turn this lever from a horizontal to a vertical
position, which thus causes the piece F to turn 90° about its axis, and
then by drawing the lever towards him he removes the piece F from the
end of the barrel, which, thus exposed, is ready to receive the
cartridge. The cartridge contains the powder and the bullet in one case,
the posterior portion containing also a charge of _fulminate_ in the
centre, and it is by the needle penetrating the case of the cartridge
and detonating this fulminate that the charge is exploded. When the
cartridge has been placed in the barrel, the piece F is pushed forward,
the metallic collar and india-rubber ring stop up the rear of the
barrel, and on turning the lever, E, into a horizontal position, the
breech is entirely closed. If now the trigger be drawn, the hammer is
released, and the spring carries it forward, at the same time impelling
the needle through the base of the cartridge-case, where it immediately
causes the explosion of the fulminate. The bullet is conical, and its
base having a slight enlargement, the latter moulds itself to the
grooves with which the barrel is rifled. When the piece has not to be
fired immediately, the lever is not placed horizontally, but in an
inclined position, in which the hammer cannot move forward, even if the
trigger be drawn. The Chassepot has an effective range of 1,093 yards,
and the projectile leaves the piece with a velocity of 1,345 ft. per
second, the trajectory being such that at 230 yards the bullet is only
18 in. above the straight line. The piece can be charged and fired by
the soldier in any position, and it was found that it could be
discharged from seven to ten times per minute, even when aim was taken
through the sights with which it is furnished, and fourteen or fifteen
times per minute without sighting. The ordinary rifled musket, which
this arm superseded, could only be fired twice in a minute, and could
only be loaded when the soldier was standing up.

Other nations followed either by adopting as their infantry arm some
form of breech-loader, or by converting their muzzle-loaders into
breech-loaders as a temporary expedient, pending the selection of some
more perfect type. When in 1864 a committee which had been appointed to
investigate the question of proper arms for our infantry, recommended
that that branch of the service should be supplied with breech-loaders,
our Government, considering that no form of breech-loader had up to that
time been invented which would unequivocally meet all the requirements
of the case, wisely determined that, pending the selection of a suitable
arm, the service muzzle-loaders should meanwhile be converted into
breech-loaders. The problem of how this was to be done was solved by the
gunmaker Snider, and in the “Converted Enfield” or “Snider” the British
army was provided for a time with an arm satisfying the requirements of
that period. This change of weapon was effected at a comparatively small
outlay, for the conversion cost less than twenty shillings an arm. The
breech action in the Snider consisted of a solid piece of metal which
closed the breech end of the barrel, and, being hinged on the right-hand
side parallel to the barrel, could be turned aside, making room for the
insertion into the conically widened bore of a metallic cartridge case,
invented by Colonel Boxer, which contained the projectile, the powder
charge, and the means of ignition in itself. A short backward movement
of the breech-lock caused a claw acting on the base of the spent
cartridge case to withdraw it from the barrel, and then the reaction of
a spring brought the breech-block back into position, after insertion of
a new cartridge. This cartridge proved very effective in increasing the
range and accuracy of the weapon. It should be mentioned that all the
breech-loading mechanisms are provided with arrangements by which the
metallic cases of the spent cartridges are automatically extracted from
the barrel. The authorities having, in 1866, offered gunmakers and
others handsome prizes for the production of rifles best fulfilling
certain conditions, nine weapons were selected out of 104 as worthy to
compete. No first prize was awarded, but the second was given to Mr.
Henry, while Mr. Martini was seventh on the list. In order to obtain a
weapon fulfilling all the requirements, a vast number of experiments
were made by the committee appointed for that purpose, as to best
construction of barrel, size of bore, system of rifling, kind of
cartridge, and other particulars, and assistance was rendered by several
eminent gunsmiths and engineers.

[Illustration:

  FIG. 86.—_Section of Martini-Henry Lock._
]

After a severe competition it appeared that the best weapon would be
produced by combining Henry’s system of rifling with Martini’s mechanism
for breech-loading. The parts constituting the lock and the mechanism
for working the breech, shown in Fig. 86, are contained in a metal case,
to which is attached the woodwork of the stock, now constructed in two
parts. To this case is attached the butt of the rifle by a strong metal
bolt 6 in. in length, A, which is inserted through a hole in the
heel-plate. The part that closes the breech—termed the “block”—is marked
B. It turns loosely on a pin, C, passing through its rear end and fixed
into the case at a level somewhat higher than the axis of the barrel.
The end of the block is rounded off so as to form with the rear end of
the case, D, which is hollowed out to receive it in a perfect knuckle
joint. Let it be observed that this rounded surface, which is the width
of the block, receives the whole force of the recoil, no strain being
put on the pin, C, on which the block turns. In the experiments a leaden
pin was substituted, and the action of the mechanism was not in the
least impaired. This arrangement serves greatly to diminish the wear and
the possibility of damage from the recoil. As the pin on which the block
turns is slightly above the axis at the barrel, it follows that the
block, when not supported, immediately drops down below the barrel.
Behind the trigger-guard is a lever, E, working on a pin, F, fitted into
the lower part of the case. To this lever is attached a much shorter
piece called the “tumbler,” which projects into the case, G. It is this
tumbler which acts as a support for the block, and raises it into its
firing position or lowers it according as the lever, E, is drawn toward
a firer or pushed forward. How this is accomplished will be readily
understood by observing the form of the notch, H, in which the upper end
of the tumbler moves. It will be noticed that the piece being in the
position for firing, if the lever be pushed back, G slides away from the
shallower part of the notch into the deeper, and the block accordingly
falls into the position shown in the figure; and if again the lever is
drawn backward, G acting on H will raise the block to its former
position. The block or breech-piece is hollowed out on its upper
surface, I, so as to permit the cartridge to be readily inserted into
the exploding chamber, J. The centre of the block is bored out, and
contains within the vital mechanism for exploding the cartridge, namely,
a spiral spring, of which the little marks at K are the coils in
section. These coils pass round apiece of metal called the “striker,”
which is armed with a point, capable of passing through a hole in the
front face of the block exactly behind the percussion-cap of the
cartridge when the block is in the firing position. When the lever
handle is moved _forward_, it causes the tumbler, which works on the
same pin, to revolve, and one of its arms draws back the striker,
compressing the spring in so doing, so that as the block drops down the
point of the striker is drawn inwards. In this position the piece
receives the cartridge into the chamber. The lever, E, being now drawn
backward, the piece is forced into the notch, H, and the block is kept
firmly in its place; besides this, there is a further compression of the
spring by the tumbler, and in this position the spring is retained by
the rest-piece, L, which is pushed into a bend in the tumbler. By
pulling the trigger this piece is released, so that the tumbler can
revolve freely, and relieve the pent-up spring, whose elasticity impels
the striker forward, so that this enters the carriage directly. A very
important and ingenious part of this arrangement is the contrivance for
extracting the case of the exploded cartridge. The extractor turns on
the pin, M, and has two arms pointing upwards, N, which are pressed by
the rim of the cartridge pushed home into two grooves cut in the sides
of the barrel. It has another arm, O, bent only slightly upwards and
pointing towards the centre of the case, and forming an angle of about
80° with the above-mentioned upright arm; when, by pushing forward the
lever, its short arm drops into the recess, the block, no longer
supported, falls, and hits the point of the bent arm of extractor, so
causing the two upright arms to extract the cartridge-case a little way.

[Illustration:

  FIG. 87.—_The Martini-Henry Rifle._

  A, ready for loading; B, loaded and ready for firing.
]

The barrel is of steel; the calibre is 0·451 in. It is rifled on Mr.
Henry’s patent system. The section of the bore may be generally
described as a heptagon with re-entering angles at the junctions of the
planes, so that there are fourteen points of contact for the bullet,
viz., one in the middle of each plane, and one at each of the
re-entering angles. The twist of rifling is one turn in 22 in. The
charge consists of 85 grains of powder, and a bullet weighing 480
grains, of a form designed by Mr. Henry. The cartridge is of the same
general construction as the “Boxer” cartridge, used in the Snider rifle,
but it is bottle-shaped, the diameter being enlarged from a short
distance in rear of the bullet, in order to admit of its being made
shorter, and consequently stronger, than would be otherwise possible. A
wad of bees’-wax is placed between the bullet and powder, by which the
barrel is lubricated at each discharge. The sword-bayonet to be used
with this rifle is of a pattern proposed by Lord Elcho. It is a short
sword, broad towards the point, and furnished on a portion of the back
with a double row of teeth, so as to form a stout saw. It is so balanced
as to form a powerful chopping implement, so that, in addition to its
primary use as a bayonet, it will be useful for cutting and sawing
brushwood, small trees, &c.

The following are the principal particulars of weight, dimensions, &c.,
of the Martini-Henry rifle:

                         │Without bayonet            4 ft.     1     in.
 Length of rifle         │With bayonet fixed         5 ft.     8     in.
                         │Of barrel                  2 ft.     9·22  in.

 Calibre                 │                                     0·451 in.

 Rifling                 │Grooves                    7
                         │Twist                      1 turn in 22    in.

 Weight                  │Without bayonet            8 lbs.    7     oz.
                         │With bayonet              10 lbs.    4     oz.

 Bayonet                 │Length                     2 ft.     1½    in.
                         │Weight without scabbard    1 lb.     8     oz.

 Charge of powder        │                          85 grains.
 Weight of bullet        │                         480 grains.

                  The rifle is sighted to 1,400 yards.

As an evidence of the accuracy of fire in this rifle, it may be stated
that of twenty shots fired at 1,200 yards, the mean absolute deflection
of the hits from the centre of the group was 2·28 ft. The highest point
in the trajectory at 500 yards is rather over 8 ft. so that the bullet
would not pass over a cavalry soldier’s head within that distance. The
trajectory of the Snider at the same range rises to nearly 12 ft. The
bullet will pass through from thirteen to seventeen ½ in. elm planks
placed 1 in. apart at 20 yards distance; the number pierced by the
Snider under similar circumstances being from seven to nine. As regards
rapidity of fire, twenty rounds have been fired in 53 seconds; and one
arm which had been exposed to rain and water artificially applied for
seven days and nights, and had during that time fired 400 rounds, was
then fired, without cleaning, twenty rounds in 1 minute 3 seconds.

Rifles of the Martini-Henry and Chassepot type were soon superseded, for
as early as 1876 Switzerland had armed her troops with a magazine rifle
of a smaller calibre than any then in use, and this weapon was found so
effective that in a few years after every European nation had followed
suit, as also had the United States and Japan, each country adopting
some particular pattern of a weapon with certain modifications. Of these
the Mannlicher and the Mauser are much used. A magazine rifle is one
that can be fired several times successively without reloading. Like
revolvers, the magazine arms repeat their fire, but instead of having
several distinct firing chambers, they have but one, from which the
empty cartridge cases are automatically extracted by the breech
mechanism, for the magazine rifle is necessarily a breech-loader. The
magazine rifle carries a supply of cartridges, which one after another
are brought into the firing chamber by the simple action of the breech
mechanism, so that the soldier is enabled to discharge several rounds in
any position without reloading. The several varieties of the magazine
rifle may be classed according to the position of the magazine. This may
be: First, in the stock; second, under the barrel; third, in a box under
the breech; or fourth, in a box above the breech. In the first and
second variety the cartridges are in line in a tube, out of which they
are moved on by a spiral spring, and this was the earlier form of the
weapon. The box above or below the breech is the later development, and
has the advantage of holding the cartridges lying side by side, and thus
in a position in which they are not so liable to injure each other as in
the tubular arrangements. Then, again, the movement of the cartridge in
the breechbox in arriving at the firing chamber is much less than in the
linear magazines, and the centre of gravity of the whole changes but
little when the supply is exhausted. With any of the varieties of
magazine a suitable modification of the mechanism may be adopted, so
that the weapon can at will be used as a single firing rifle, but
changeable in an instant to the magazine form. Again, the box magazine
may be made as a fixture on the rifle, or it may be detachable.
Commissions of military authorities had for several years been
deliberating upon the best models for their respective nations, while
Professor Hebler was working out his researches as to the best calibre
for military rifles. Hebler published a work showing the great
advantages of a bore one-third less in diameter than that commonly in
use, which was about 0·45 inch, as in our Martini-Henry. The
small-calibre rifle shoots straighter and hits harder than the large
bore one, and the recoil is less, and so is the weight of the weapon.
Lead is found to be too soft a material for the bullet of the small-bore
rifles, as it does not keep in the rifling, which has a sharper turn
than that in the older weapon; hence the bullets are now cased in steel
or nickel. These bullets have remarkable power of penetration. Some will
go through a steel plate 1¼ inch thick, making a clean hole in it, and
the Lebel bullet penetrates 15 inches of solid oak, at a distance of 220
yards. Such a missile would, therefore, be capable of going completely
through the bodies of several men or horses.

[Illustration:

  FIG. 88.—_The Mannlicher Magazine Rifle._
]

The Germans, about 1888, adopted a magazine rifle known as the Mauser.
It had a fixed tubular magazine for eight rounds below the barrel, and a
breech mechanism of the Remington-Keene type. The French followed suit
with their famous Lebel gun, the construction of which was long kept
secret. It also has a fixed under barrel tubular magazine, and the
cartridges used with it contain smokeless powder. It is said that a new
gun of practically the same pattern has been adopted by Russia, but with
a detachable magazine to contain five rounds. The Russian gun will also
use smokeless powder. In England, a small-bore rifle of 0·303 inches
calibre is now issued to all troops. It has an under breechbox magazine,
modified from the Lee rifle. The box is detachable, so that the weapon
could normally be used as a single loader, and the magazine attached
only when required. But the British authorities have decided that the
magazine box is to be attached to the weapon by a chain. The first issue
of this pattern of rifle to British soldiers took place early in 1890.
The Austrians are adopting the Mannlicher pattern, in which the magazine
idea is embodied in a complete and practical form. This rifle has a
fixed box magazine below the breech. From this box, in which the
cartridges—five in number—lie side by side, they are fed up by springs
as they are disposed of by the movement of the breech mechanism. The
magazine is recharged by placing in it a tin case containing five
cartridges, and the case drops out when all the cartridges have been
fired. In this form there is of course no necessity for providing any
mechanism for holding the magazine in reserve while the rifle is used as
a single loader. As to calibre, the Austrian authorities follow other
countries in adopting a small bore, namely, 0·315 inch. Italy has
converted her single-fire Vetterli rifle into a magazine arm, with a box
something like the Mannlicher, and Belgium has adopted a gun of the same
type. The rate of fire from charged magazines of such guns as the “Lee,”
“Mannlicher” and “Vetterli,” worked with the right hand without bringing
the piece down from the shoulder is, for all of them, about one shot per
second; but the time that is required to recharge the magazines varies
much according to the contrivance used. The number of rounds the
magazine of a rifle is capable of containing when fully charged is from
5 to 12, or more, according to the difference of system. It is
considered that in the detachable Lee or the quick recharging Mannlicher
five rounds are ample for use at a critical moment.

[Illustration:

  FIG. 89.—_The Magazine and Breech of the Mannlicher Rifle._
]

The calibre of the military rifle has been decreased with almost every
new pattern adopted. Thus, while the _old_ “Brown Bess” had a calibre of
0·75 inch, in the last issue of it the bore was reduced to 0·693 inch;
the Enfield (1852) had a bore of 0·577 inch; the Martini-Henry, 0·451
inch, which, in a newer pattern adopted in 1887, was reduced to 0·400
inch; and, finally, in the Lee-Metford, the calibre is only 0·303 inch.
A similar consecutive reduction of bores has taken place in the rifles
adopted by other countries, and one of the latest type, issued for the
use of the United States Navy, has a bore of only 0·236 inch, and it is
even expected that a still smaller one will become general. The
advantage of the narrow and lighter projectile is that while it has a
higher initial velocity with a given charge, its flight is less checked
by the resistance of the atmosphere, the section it presents being so
much less. Thus the bullet of 0·236 inch diameter has a section little
more than one-fourth that of the 0·45 inch bullet. The difference is
well shown in the comparative heights of the _trajectory_ (or path of
the bullet) of the Martini-Henry 0·450 inch bullet, and that of the
0·303 inch Lee-Metford (the latter with _cordite_ ammunition); for at a
range of 1,000 yards the former reaches to 48 feet above the line of
sight, while the latter rises to only 25 feet.

Some form of repeating or magazine rifle has now been adopted by all the
most important nations of the world. The number of shots contained in
the magazines varies from 5 to 12. In the British detachable box
magazine there are ten charges. The calibres of the barrels range in the
infantry patterns of different nations from 0·256 inch to 0·315 inch;
the explosive used in every case is some kind of smokeless powder, and
this, in the cartridge for the Lee-Metford, is _cordite_. The bullets
are not made simply of lead, but of lead coated with a harder metal or
alloy such as steel, cupro-nickel, nickel steel, or they consist
entirely of some of these alloys.

Although the magazine rifle is now the regulation weapon of the infantry
of all great armies, it is not improbable that at no distant future it
maybe superseded by one in which, as in certain machine guns, the force
of the recoil will be used for actuating the breech and lock movements.
Many patents have already been taken out for rifles on this principle,
and several patterns have actually been constructed, in which a merely
momentary contact of the breech-piece with the end of the barrel is
sufficient; the recoil of the barrel with the reaction of a spring
performs all the requisite movements with such rapidity that an amazing
speed of firing has been obtained. It is said that such an automatic gun
can send forth bullets at a perfectly amazing rate. Of course the
mechanism of such a gun is somewhat intricate, and it is impossible to
explain its construction and action without a great number of diagrams
and much description.


                            _RIFLED CANNON._

Having briefly sketched in the foregoing section the development of the
military rifle from such weapons as our own “Brown Bess,” down to the
repeating or magazine rifle, we now purpose to adopt a similar course
with regard to ordnance, giving also some particulars of the methods of
manufacture, etc., and following in general the order of history.

Naturally there is nothing that accelerates progress in warlike
inventions so much as the exigences of war itself. This is well
exemplified in circumstances attending the Crimean War, which was waged
in 1854 by England and France in alliance against Russia. The desire of
having ships that could run the gauntlet of the heavy guns mounted on
Russian forts led to the construction of _La Gloire_ and other
armour-plated vessels, as we have already seen, and a suggestion of the
French Emperor, as to improving metal for guns, made to Mr. Bessemer,
led incidentally but ultimately to the great revolution in the
manufacture of steel, although it is true that Krupp of Essen had begun
to produce small cast-steel ordnance as early as 1847. But what
determined the necessity for rifled ordnance was more particularly the
greater comparative effects obtained by the muzzle-loading rifles over
the field artillery then in use in the several engagements that took
place in the Crimea, especially in the battle of Inkerman (1854). The
rifles so much surpassed in accuracy at long ranges the smooth-bore
field-pieces firing spherical projectiles, that field artillery was on
the point of losing its relative importance, and even in the matter of
range the latter lost so much by windage that the men serving the
artillery could sometimes be leisurely picked off by the rifle
sharp-shooters. Inventors were soon at work on devising methods of
increasing the accuracy of ordnance fire with both light and heavy
pieces, and before the end of the war some cast-iron guns rifled on
Lancaster’s plan had been mounted on forts and in ships, without proving
very successful except in regard to increase of range when elongated
pointed projectiles were used with them.

[Illustration:

  FIG. 90.—_32–pounder, 1807._
]

Now let us see of what kind was the ordnance used for some years after
the middle of the century, in order that we may be the better able to
appreciate the progress that has since been made. Ordnance is, as
already noticed, of several species, as guns mounted on fortresses,
naval guns, siege guns, field-guns, etc., and the size of the pieces
under each of those heads is distinguished sometimes in one, sometimes
in another of three different ways. We may name it by the weight of the
gun itself in tons or hundredweights, as “a 35–ton gun,” etc.; or by the
weight of its projectile, as “a 68–pounder,” etc.; or by its calibre,
that is the diameter of its bore, as “a 4–inch gun,” etc. We may take
the naval guns with which Nelson won his battles (Trafalgar, 1807) as
representative of all except field ordnance up to about 1856. They were
all made of cast iron, threw spherical projectiles, and were very rudely
mounted. The gun most commonly mounted on board our ships of war was the
32–pounder, weighing 32 cwt., shown with its carriage in Fig. 90. The
carriage was of wood, and consisted of two side pieces joined back and
front by two transverse pieces and carried by four low wooden wheels.
The trunnions of the gun fitted into bearings at the top of the
side-pieces, and were secured by iron plates that passed over them in a
semi-cylindrical form and were bolted down to the wood. The position of
the trunnions on the gun was always such that the breech end of the gun
preponderated, being supported on an adjustable wooden wedge; and when
the muzzle of the gun had to be lowered, this was done by raising the
breech end with handspikes and pushing in the wedge so far as to prevent
the breech from dropping down again. There was a vent or narrow passage
to contain a train of powder from the touch-hole at the upper part of
the breech to the rear of the charge. When the gun was fired, with its
muzzle protruding a little way out of the port-hole, the recoil would
trundle it inwards about its own length, when its course would be stayed
by a thick rope attached to the sides of the vessel; and by other tackle
it would be kept in position until loaded, when it would be allowed to
roll back, or would be drawn by ropes and pulleys out to the port-hole,
and by the same means such lateral inclination as might be required
could be given. This last adjustment was called _training_ the gun. A
32–pounder required the services altogether of a dozen or fourteen men,
but these by virtue of constant drill would learn to handle the clumsy
machine with a certain amount of expedition. If we except a notch on the
highest point of the muzzle, the pieces were devoid of anything of the
nature of sights, though sometimes marks were made on the adjustable
wedge under the breech to correspond with certain elevations. Nor were
sights required; for the mode of fighting then was to get quite close to
the adversary’s ship and pour in a _broadside_ by firing simultaneously
all guns on the enemy’s side when they had been _trained_ (by rough
methods), so as to concentrate their effect as much as possible on one
point of the antagonist. Nelson’s famous ship the _Victory_ carried a
few larger guns than the 32–pounders, namely, two 68–pounders, called
_carronades_ (from having first been cast at Carron in Scotland), and
some 42–pounders. The 32– and 42–pounders numbered together thirty, and
there were also as many 24–pounders, with forty 12–pounders. These were
all simply cast of the required dimensions, and were not made with the
one single improvement which after two centuries’ use of cast-iron guns
had been introduced into France about fifty years before, namely, the
_boring_ of the chase out of a solid casting.

On the outbreak of the Crimean War (1854) the minds of many inventors
were occupied by the problem of ordnance construction, and this also
engaged the attention among others of two of the most eminent British
mechanical engineers of the day. These were Sir W. Armstrong and Sir J.
Whitworth, who, with others, were invited by our War Department to
submit the best models of field and heavy guns their skill was severally
able to produce. Two years afterward, Sir W. Armstrong had, after many
experiments, completed a gun of 1·88 in. calibre. This had a forged
steel barrel 6 feet in length; but it was only after eight such forgings
had been bored and rejected on account of flaws revealed only by the
boring that a sound barrel was at length obtained. This barrel was
strengthened on the outside by _jackets_ made from coils of wrought iron
bars welded into a piece and shrunk on while hot (of which process we
shall have something more to say presently); the barrel was rifled with
many shallow grooves, and the pointed projectile, 3 calibres long, was
made of lead, for which afterwards iron coated with lead was
substituted. This gun was a breech-loader, the breech being closed by a
block let into a slot after loading, and then pressed against the barrel
by some turns of a screw which advanced parallel to the axis of the
piece, and was made hollow for loading through, before the closing block
was put in. In a trial of the various pieces ready in 1857, it was found
that the Armstrong gun made as just described had an accuracy and range
immensely greater than any weapon that had ever been tested, and the
Government authorities approved of the system of construction, except
that they preferred muzzle-loading pieces to breech-loading, as being
simpler in action, more easily kept in repair, and cheaper in original
cost and ammunition.

When Sir Joseph Whitworth’s gun was, in 1863, submitted to a competitive
trial against the Armstrong, as to their endurance and mode of ultimate
failure when fired with ever-increasing charges of powder and shot, at
the forty-second round the Armstrong breech-loader split, and at the
sixtieth the Armstrong muzzle-loader had one of its coils cracked; while
it was not until the ninety-second round that the Whitworth gun burst
violently into eleven pieces. These competing guns were 12–pounder
field-guns weighing 8 cwts., and from each 2,800 regulation rounds had
been fired before they were subjected to the bursting proofs. The result
of these trials being that the authorities considered that steel was not
then sufficiently reliable, and they decided to adopt the system of
building up rifled guns with iron jackets over an inner tube of steel.
Sir Joseph Whitworth made his guns entirely of steel, and they were
striking examples of beautiful and accurate workmanship. His system of
rifling consisted in forming the bore of the gun so that its section is
a regular hexagon, and the projectile is an elongated bolt with sides
exactly fitting the barrel of the gun: the projectile is, in fact, a
twisted hexagonal prism. Fig. 91 shows at the left-hand side the section
of the barrel, and on the right we see the form of the projectile on a
smaller scale, this last representing, in fact, the exact size and shape
of the bullet of the Whitworth _rifle_ mentioned on another page. Sir
Joseph’s guns were muzzle-loaders, and they were remarkable for their
long range and accuracy of fire. One of these guns, with a charge of 50
lbs. of gunpowder, threw a 250–lb. shot a distance of nearly six miles,
and on another occasion a 310–lb. shell was hurled through the air, and
first touched the ground at a distance of more than six and a quarter
miles from the gun. These distances are greater than any to which shot
or shell had previously been thrown.

[Illustration:

  FIG. 91.—_Whitworth Rifling and Projectile._
]

As the material of these Whitworth guns was very costly, and very
perfect workmanship was required in the formation of the barrel and the
shots, the expense attending their manufacture and use was much greater
than that incurred in the case of the Armstrong guns. Sir W. Armstrong’s
estimate for a 35–ton gun was £3,500, and Sir J. Whitworth’s, £6,000.
The gun, as constructed at Woolwich on Mr. Fraser’s plan, was estimated
to cost £2,500. The first cost of a gun is a matter for consideration,
since each piece, even the strongest, is able only to fire a limited
number of rounds before it becomes unsafe or useless. It appears that no
cannon has yet been constructed capable of withstanding without
alteration the tremendous shocks given by the explosion of the
gunpowder, and these alterations, however small at any one discharge,
are summed up and ultimately bring to an end what may be termed the
“life of the piece.”

[Illustration:

  FIG. 92.—_600–pounder Muzzle-loading Armstrong Gun._
]

About the year 1858 Sir William Armstrong (afterwards Lord Armstrong)
established at Elswick, Newcastle-on-Tyne, a manufactory of ordnance,
which has since developed into the great arsenal now so well known all
over the world. Here all the resources of science have been applied to
the problems of artillery, and experiments carried on with a prodigality
of cost and promptness of execution impossible at a government
establishment trammelled with official regulations. Here, and also at
Woolwich, our national ordnance factory, guns have since always been
constructed on the building-up plan advocated by Sir W. Armstrong, whose
principle consists in disposing of the fibre of the iron so as best to
resist the strains in the several parts of the gun. Wrought iron being
fibrous in its texture has, like wood, much more strength in the
direction of the grain than across it. The direction of the fibre in a
bar of wrought iron is parallel to its length, and in that direction the
iron is nearly twice as strong as it is transversely. A gun may give way
either by the bursting of the barrel or by the blowing out of the
breech. The force which tends to produce the first effect acts
transversely to the axis of the gun; hence the best way to resist it is
to wrap the iron round the barrel, so that the fibres of the metal
encircle it like the hoops of a cask. The force which tends to blow out
the breech is best resisted by disposing the fibres of the iron so as to
be parallel to the axis of the gun; hence Sir W. Armstrong makes the
breech-piece from a solid forging with the fibre in the required
direction. But the Elswick building-up principle involves much more than
the direction of the fibres of the iron, for each coil or jacket, after
having its spires welded together, was bored out on a lathe, and the
exterior of the part of the gun on which it was to be placed was also
turned with the utmost exactness, so that when the enveloping piece was
heated to a certain temperature and in this state brought into position,
it would in cooling compress the parts it encircled just to that degree
which careful calculations showed would best strengthen the gun without
unduly straining the metal at any part. The Elswick guns being built up
of several superimposed jackets of calculated lengths and thicknesses,
the means was afforded of distributing the tensions throughout the whole
mass of metal to the best advantage. In the simpler form, arranged by
Mr. Fraser, and for the sake of economy adopted by the authorities at
Woolwich in 1867, the greater part of the benefit derivable from
adjustment of tension was no doubt sacrificed to cheapness of
manufacture. These, and also the forms of Armstrong guns that have not
yet been described, ceased to be made after 1880, by which time steel
had replaced iron in every part of the construction and fittings of
guns, and muzzle-loading had been definitely abandoned in favour of
breech-loading.

[Illustration:

  FIG. 93.—_35–ton Fraser Gun._
]

Now, in 1874, when the first edition of the present work was in
preparation, the Fraser-Woolwich guns were in full vogue, being spoken
of by the public press as the _ne plus ultra_ of artillery construction
in size, efficiency, and economy. When, accordingly, the author had been
privileged to visit the arsenal and witness the production of these guns
in every stage of their manufacture, he wrote a description of it which
is here retained as printed at the time, seeing that it may not be
without historical interest, particularly since great numbers of these
guns must still be extant, mounted on our forts in various parts of the
world, and seeing also that the description of the simpler formations
may render more easily to be understood future references to similar
operations in gun-making as have been retained in the later
developments. Of course, the following description was written in the
_present tense_, and therefore in perusing it the reader must constantly
bear in mind that the guns with which our ships of war have since been
equipped are in _every respect entirely different_ from


                 _The Fraser-Woolwich Guns, 1867–1880._

[Illustration:

  FIG. 94.—_Section of 9 in. Fraser Gun._
]

Until the year 1867 the guns made at Woolwich were constructed according
to the original plan proposed by Sir W. Armstrong, and on this system
one of the large guns consisted of as many as thirteen separate pieces.
These guns, though unexceptionable as to strength and efficiency, were
necessarily so very costly that it became a question whether anything
could be done to lessen the expense by a simpler mode of construction or
by greater economy in the material. The problem was solved in the most
satisfactory manner by Mr. Fraser, of the Royal Gun Factory, who
proposed an important modification of the original plan, and the
adoption of a kind of iron cheaper than had been previously employed,
yet perfectly suited for the purpose. Mr. Fraser’s modification
consisted in building up the guns from only a few coils, instead of
several, the coils being longer than Sir W. Armstrong’s, and the iron
coiled upon itself two or even three times: a plan which enabled him to
supersede the breech-piece, formerly made in one large forging, by a
piece formed of coils. In order to perceive the increased simplicity of
construction introduced by Mr. Fraser, we need but glance at the section
of a 9 in. gun constructed according to his system, Fig. 94, and
remember that a piece of the same size made after the original plan had
ten distinct parts, whereas the Fraser is seen to have but four. Compare
also Figs. 92 and 93. We shall now describe the process of making the
Fraser 9 in. gun. The parts of the gun as shown in the section, Fig. 94,
are: 1, the steel barrel; 2, the B tube; 3, the breech-coil; 4, the
cascable screw. The inner steel barrel is made from a solid cylinder of
steel, which is supplied by Messrs. Firth, of Sheffield. This steel is
forged from a cast block, the casting being necessary in order to obtain
a uniform mass, while the subsequent forging imparts to it greater
solidity and elasticity. After the cylinder has been examined, and the
suitable character of the steel tested by trials with portions cut from
it, the block is roughly turned and bored, and is then ready for the
toughening process. This consists in heating the tube several hours to a
certain temperature in an upright furnace, and then suddenly plunging it
into oil, in which it is allowed to remain for a day. By this treatment
the tenacity of the metal is marvellously increased. A bar of the steel
1 in. square previous to this process, if subjected to a pull equal to
the weight of 13 tons, begins to stretch and will not again recover its
original form when the tension is removed, and when a force of 31 tons
is applied it breaks. But the forces required to affect the toughened
steel in a similar manner are 31 tons and 50 tons respectively. The
process, unfortunately, is not without some disadvantages, for the
barrel is liable to become slightly distorted and even superficially
cracked. Such cracks are removed by again turning and boring; the
hardness the steel acquires by the toughening process being shown by the
fact that in the first boring 8¼ in. diameter of _solid_ steel is cut
out in 56 hours, yet for this slight boring, in which merely a thin
layer is peeled off, 25 hours are required; and lest there should be any
fissures in the metal, which, though not visible to the eye, might make
the barrel unsound, it is filled with water, which is subjected to a
pressure of 8,000 lbs. per square inch. If under this enormous pressure
no water is forced outwards, the barrel is considered safe. It is now
ready to have the B tube shrunk on it.

The B tube, like certain other portions of these guns, is constructed
from coiled iron bars, and this constitutes one great peculiarity of Sir
W. Armstrong’s system. It has the immense advantage of disposing the
metal so that its fibres encircle the piece, thus applying the strength
of the iron in the most effective way. The bars from which the coils are
prepared are made from “scrap” iron, such as old nails, horse-shoes, &c.
A pile of such fragments, built up on a wooden framework, is placed in a
furnace and intensely heated. When withdrawn the scraps have by
semi-fusion become coherent, and under the steam hammer are soon welded
into a compact mass of wrought iron, roughly shaped as a square prism.
The glowing mass is now introduced into the rolling-mill, and in a few
minutes it is rolled out, as if it were so much dough, into a long bar
of iron. In order to form this into a coil it is placed in a very long
furnace, where it can be heated its entire length. When sufficiently
heated, one end of the bar is seized and attached to an iron core of the
required diameter, and the core being made to revolve by a steam engine,
the bar is drawn out of the furnace, winding round the core in a close
spiral, so that the turns are in contact. The coil is again intensely
heated, and in this condition a few strokes of the steam hammer in the
direction of its axis suffice to combine the spires of the coil into one
mass, thus forming a hollow cylinder.

The B tube for the 9 in. gun is formed of two double coils. When the two
portions have been completely welded together under the steam hammer,
the tube, after cooling, is roughly turned and bored. It is again fine
bored to the required diameter, and a register of the diameter every few
inches down the bore is made. These measurements are taken for the
purpose of adapting most accurately the dimensions of the steel barrel
to the bore of the B tube, as it is found that perfect exactness is more
easily obtained in turning than in boring. The steel barrel is therefore
again turned to a size slightly _larger_ than the bore of the B tube,
and is then placed muzzle end upwards, and so arranged that a stream of
water, to keep it cool, shall pass into it and out again at the muzzle,
by means of a syphon, while the B tube, which has been heated until it
is sufficiently expanded, is passed over it and gradually cooled.

If now the B tube were allowed to cool spontaneously, its ends would, by
cooling more rapidly than the central part, contract upon the steel
barrel and grip it firmly at points which the subsequent cooling would
tend to draw nearer together longitudinally, and thus the barrel would
be subjected to injurious strains. In order to prevent this, the B tube
is made to cool progressively from the breech end, by means of jets of
water made to fall upon it, and gradually raised towards the muzzle end,
which has in the meanwhile been prevented from shrinking by having
circles of gas-flames playing upon it.

The breech-coil, or jacket, is formed of three pieces welded together.
First, there is a triple coil made of bars 4 in. square, the middle one
being coiled in the reverse direction to the other two. After having
been intensely heated in a furnace for ten hours, a few blows on its end
from a powerful steam hammer welds its coils perpendicularly, and when a
solid core has been introduced, and the mass has been well hammered on
the sides, it becomes a compact cylinder of wrought iron, with the
fibres all running round it. When cold it is placed in the lathe, and
the muzzle end is turned down, leaving a shoulder to receive the
trunnion-ring. The C coil is double, welded in a similar manner to the B
coil, and it has a portion turned off, so that it may be enclosed by the
trunnion-ring.

The trunnion-ring is made by punching a hole in a slab of heated iron
first by a small conical mandrel, and then enlarging by repeating the
process with larger and larger mandrels. The iron is heated for each
operation, and the trunnions are at the same time hammered on and
roughly shaped—or, rather, only one has to be hammered on—for a portion
of the bar which serves to hold the mass forms the other. The
trunnion-ring is then bored out, and after having been heated to
redness, is dropped on to the triple breech-coil which is placed muzzle
end up, and the turned end of the C coil (of course, not heated) is then
immediately placed within the upper part of the trunnion-ring. The
latter in cooling contracts so forcibly as to bind the ends of the coils
together, and the whole can thus be placed in a furnace and heated to a
high temperature, so that when removed and put under the steam hammer,
its parts are readily wielded into one mass. The breech-coil in this
state weighs about 16 tons; but so much metal is removed by the
subsequent turnings and borings, that it is reduced to nearly half that
weight in the gun. It is then turned in a lathe of the most massive
construction, which weighs more than 100 tons. Fig. 34, page 95, is from
a drawing taken at Woolwich, and shows one of the large guns in the
lathe. No one who witnesses this operation can fail to be struck with
the apparent ease with which this powerful tool removes thick flakes of
metal as if it were so much cheese. The projections of the trunnions
prevent the part in which they are situated from being finished in this
lathe, and the gun has to be placed in another machine, where the
superfluous metal of the trunnion-ring is pared off by a tool moving
parallel to the axis of the piece. Another machine accomplishes the
turning of the trunnions, the “jacket” being made to revolve about their
axis. The jacket is then accurately bored out with an enlargement or
socket to receive the end of the B tube, and a hollow screw is cut at
the breech end for the cascable.

The portion of the gun, consisting of the steel barrel with the B tube
shrunk on it, having been placed upright with the muzzle downwards, the
breech-piece, strongly heated, is brought over it by a travelling crane,
and slips over the steel barrel, while the recess in it receives the end
of the B tube. Cold water is forced up into the inside of the barrel in
order to keep it cool. As the breech cools, which it is allowed to do
spontaneously, it contracts and grips the barrel and B tube with great
force. The cascable requires to be very carefully fitted. It is this
piece which plays so important a part in resisting the force tending to
blow out the end of the barrel. The cascable is a solid screw formed of
the very best iron, and its inner end is wrought by scraping and filing,
so that when screwed in there may be perfect contact between its face
and the end of the steel barrel. A small annular space is left at the
circumference of the inner end, communicating through a small opening
with the outside. The object of this is, that in case of rupture of the
steel barrel, the gases escaping through it may give timely warning of
the state of the piece.

Besides minor operations, there remain the important processes of
finishing the boring, and of rifling. The boring is effected in two
operations, and after that the interior is gauged in every part, and
“lapping” is resorted to where required, in order to obtain the perfect
form. Lapping consists in wearing down the steel by friction against
fine emery powder and oil, spread on a leaden surface. The piece is then
ready for rifling. The machinery by which the rifling is performed
cannot be surpassed for its admirable ingenuity and simplicity.

In this operation the gun is fixed horizontally, its axis coinciding
with that of the bar, which carries the grooving tools. This bar is
capable of two independent movements, one backwards and forwards in a
straight line in the direction of the length of the bar, and the other a
rotation round its axis. The former is communicated by a screw parallel
to the bar, and working in a nut attached to the end of it. For the
rotatory movement the bar carries a pinion, which is engaged by a rack
placed horizontally and perpendicularly to the bar, and partaking of its
backward and forward movement, but arranged so that its end must move
along another bar placed at an angle with the former. It is this angle
which determines the pitch of the rifling, and by substituting a curved
guide-bar for the straight one, an increasing twist may be obtained in
the grooves.

The projectile used with these guns is of a cylindrical form, but
pointed at the head, and the moulds in which these shots are cast are so
arranged that the head of the shot is moulded in iron, while the body is
surrounded with sand. The rapid cooling induced by the contact of the
cold metal causes the head of the shot to solidify very quickly, so that
the carbon in the iron is not separated as in ordinary casting. In
consequence of this treatment, the head of the shot possesses the
hardness of steel, and is therefore well adapted for penetrating iron
plates or other structures. The projectiles are turned in a lathe to the
exact size, and then shallow circular cavities are bored in them, and
into these cavities brass studs, which are simply short cylinders of a
diameter slightly larger than the cavities, are forced by pressure. The
projecting studs are then turned so as accurately to fit the spiral
grooves of the guns. Thus the projectile in traversing the bore of the
piece is forced to make a revolution, or part of a revolution, about its
axis, and the rapid rotation thus imparted has the effect of keeping the
axis of the missile always parallel to its original direction. Thus
vastly increased accuracy of firing is obtained.

[Illustration:

  FIG. 95.—_Millwall Shield after being battered with Heavy Shot.—Front
    View._
]

[Illustration:

  FIG. 96.—_Rear View of the Millwall Shield._
]

Shells are also used with the Woolwich rifled guns. The shells are of
the same shape as the solid shots, from which they differ in being cast
hollow, and having their interior filled with gunpowder. Such shells
when used against iron structures require no fuse; they explode in
coming into collision with their object. In other cases, however, the
shells are provided with fuses, which cause the explosion when the shot
strikes. Fig. 93, page 195, represents one of the 35–ton guns, made on
the plan introduced by Mr. Fraser. This piece of ordnance is 16 ft.
long, 4 ft. 3 in. in diameter at the breech, and 1 ft. 9 in. at the
muzzle. The bore is about 1 ft. Each gun can throw a shot or bolt 700
lbs. in weight, with a charge of 120 lbs. of powder. It is stated that
the shot, if fired at a short range, would penetrate a plate of iron 14
in. thick, and that at a distance of 2,000 yards it would retain
sufficient energy to go through a plate 12 in. thick. The effect of
these ponderous missiles upon thick iron plates is very remarkable.
Targets or shields have been constructed with plates and timber backing,
girders, &c., put together in the strongest possible manner, in order to
test the resisting power of the armour plating and other constructions
of our ironclad ships. The above two cuts, Figs. 95 and 96, are
representations of the appearance of the front and back of a very strong
shield of this description, after having been struck with a few 600 lb.
shots fired from the 25–ton gun. The shots with chilled heads, already
referred to, sometimes were found to penetrate completely through the 8
in. front plate, and the 6 in. of solid teak, and the 6 in. of plating
at the back. The shield, though strongly constructed with massive plates
of iron, only served to prove the relative superiority of the artillery
of that day, which was at the time when our century had yet about thirty
years to run. Up to 1876 no confidence was placed in steel as a
resisting material, a circumstance perhaps not much to be wondered at,
as its capabilities had not then been developed by the newer processes
of manufacture, described in our article on Iron; nor had mechanicians
acquired the power of operating with large masses of the metal. Since
then it has come about that only steel is relied upon for efficiently
resisting the penetration of projectiles, iron being held of no account
except as a backing. There has always been a rivalry between the
artillerist and the naval constructor, and this contest between the
attacking and the defending agencies is well illustrated in the table on
page 166, where the parallel advance in the destructive power of guns
and in the resisting power of our war-ships is exhibited in a numerical
form.

[Illustration:

  FIG. 97.—_Comparative Sizes of 35 and 81 ton Guns._

  A, 35–ton; B, 81–ton.
]

The 35–ton Fraser guns were at the time of their production humorously
called in the newspapers “Woolwich infants”; but it was not long before
they might in another sense be called infants in comparison with a still
larger gun of 81 tons weight constructed at Woolwich shortly before
iron-coiling and muzzle-loading were set aside. Fig. 97 shows the
relative dimensions of the 35–ton and 81–ton guns: the latter was built
up in the same way as the 9–inch gun described above, but the coils were
necessarily longer and the chase was formed in three parts instead of
two. The total length of this gun was 27 feet, and the bore was about 24
feet long and 14 in. in diameter, and the weight of the shot about 1000
lbs., with sufficient energy to penetrate at a considerable distance an
iron plate 20 in. in thickness. It was for the manufacture of these very
large guns that the great steam hammer, represented in Plate III., was
erected at Woolwich.

                  *       *       *       *       *

The 81–ton gun was the largest muzzle-loader ever made in the national
gun factory at the time when such huge weapons were in request; but in
1876 its dimensions were surpassed by those of a few 100–ton guns built
at Elswick to the order of the Italian Government for mounting on their
most formidable ironclads. These guns have a calibre of 17·72 inches,
and are provided with a chamber of somewhat larger bore to receive the
charge of powder. They are built up on the Armstrong shrinkage
principle, and comprise as many as twenty different tubes, jackets,
hoops, screws, etc., and are undoubtedly the most powerful
muzzle-loading weapons ever constructed. It happened, just as these guns
were completed, that the British Government, apprehensive at the time of
a war with Russia, exercised its rights of purchasing two of them, one
to be mounted at Gibraltar, the other at Malta.

The Elswick establishment soon afterwards surpassed all its former
achievements in building great guns, by designing and constructing the
huge breech-loaders, one of which forms the subject of our Plate XII.
These are known as the Armstrong 110–ton guns; they are formed of solid
steel throughout, and their weight is accurately 247,795 lbs., or 110
tons 12 cwts. 51 lbs. The total length of the gun is 43 ft. 8 in., and
of this 40 ft. 7 in. is occupied by the bore, along which the rifling
extends 33 ft. 1 in. The calibre of the rifled part is 16¼ in., and the
diameter of the powder chamber is somewhat greater. The regulation
charge of powder weighs 960 lbs., although the guns are tested with
still greater charges. The weight of the projectile is 1,800 lbs., and
it leaves the muzzle with a velocity of 2,128 ft. per second, which is
equivalent to a dynamical energy of 56,520 foot-tons. What this means
will perhaps be better understood, not by describing experiments such as
those on the Millwall Shield, the results of which are depicted in Figs.
95 and 96, but by stating that if the shot from the 110–ton gun
encountered a solid wall of wrought iron a yard thick, it would pass
through it. The Elswick 110–ton gun is, in fact, the most powerful piece
of ordnance that has ever been constructed. There are no trunnions to
these great guns, but they are encircled by massive rings of metal,
between which pass strong steel bands that tie the gun to its carriage,
or, rather, to the heavy steel frame on which it is mounted, and which
slides on a couple of girders. The force of the recoil acts on a
hydraulic ram that passes through the lower part of the supporting
frame. The whole working of the gun is done by hydraulic power, and,
indeed, the same method has been applied by the Elswick firm to the
handling of all heavy guns. By hydraulic power, maintained automatically
by a pumping engine exercising a pressure of from 800 lbs. to 1,000 lbs.
per square inch, are operated the whole of the movements required for
bringing the cartridge and the projectile from the magazine; for
unscrewing the breech block, withdrawing it, and moving it aside; for
pushing home the shot and the cartridge to their places in the bore; for
closing the breech and screwing up the block; for rotating the turret
within which the gun is mounted, or in other cases for ramming the piece
in or out, and for elevating or depressing it. It is, indeed, obvious
that such ponderous masses of metal as form the barrels and projectiles
of these 110–ton and other guns of the larger sizes could not be handled
to advantage by any of the ordinary mechanical appliances. But by the
application of the hydraulic principle, a very few men are able to work
the largest guns with the greatest ease, for their personal labour is
thus reduced to the mere manipulation of levers. On board ship the power
required for working large guns has lately been sometimes supplied by a
system of shafting driven by a steam engine and provided with drums and
pulleys, exactly as in an engineer’s workshop. Great care has also been
bestowed upon the mounting of the smaller guns, which are so nicely
poised on their bearings and provided with such accurately fitted racks,
pinions, etc., that a steel gun of 10 ft. in length can easily be
pointed in any direction by the touch of a child’s hand. The mechanical
arrangements are now so admirably adapted for facility of working that,
unless in the rude shocks of actual warfare the nicely adjusted
machinery is found to be liable to be thrown out of gear, these
applications of the engineer’s skill may be considered as having done
all that was required to bring our modern weapons to perfection.

[Illustration:

  PLATE XII.

  THE 110–TON ARMSTRONG GUN.
]

With the construction of the 110–ton we arrive at a period when
commences a new era in guns—and especially in the armament of
war-ships—necessitated by various circumstances, amongst which may be
named the invention of torpedoes and the building of swiftly moving
torpedo-boats, and of still swifter “torpedo-boat catchers or
destroyers”; so that guns that could be worked only at comparatively
long intervals were at a great disadvantage. Again, about 1880, were
published the records of a most elaborate and important series of
researches conducted by Captain Noble and Sir F. Abel, the chemist of
our War Department. They had investigated all the conditions attending
the combustion of gunpowder in confined spaces, the nature and
quantities of the products, the temperature and pressures of the
confined gases, etc. The information thus afforded was extremely
valuable; but besides this, direct experiments made with actual guns
were carried out, more particularly at Elswick, in which the speed of
the projectiles at every few inches of their travel along the bore of
the piece was ascertained, and also the pressures of the powder gases at
any point. The way in which this is done we shall explain on another
page. (_See article on Recording Instruments._)

So long as muzzle-loading was in use, guns were necessarily made short,
for had they not to be run in from the port-holes and embrasures of
forts in order to be loaded? Now there was an obvious disadvantage in
this, for the projectile left the gun before the expansive force of the
gases had been spent that could have imparted additional velocity. When
however muzzle-loading was abandoned, and especially when strong and
trustworthy steel became available for the construction of the gun
throughout, there was no reason to waste in this way the power of the
charge, so that barrels were made lighter, much longer in proportion to
the calibre, and every part accurately adapted in strength to the strain
to be resisted. For instances of increasing length, take the 38–ton
12–inch guns built up at Woolwich (of only seven pieces) for H.M.S.
_Thunderer_ (see Fig. 93), on Mr. Fraser’s plan. These had a bore equal
to only 16 times their calibre, while in the Armstrong 100–ton guns the
bore is 21 calibres long; and in the 110–ton guns the total length of
the chase is 31 times the diameter of the rifled part. It has since been
the practice to make the bore of guns from 30 to 40 calibres in length.

The effect of a longer chase used with an appropriate charge is very
clearly and instructively shown by the diagram Fig. 98, which is by
permission copied from the very comprehensive work by Messrs. E. W.
Lloyd and A. G. Hadcock, entitled _Artillery: its Progress and Present
Position_. The reader should not pass over this diagram until he has
thoroughly understood it, for it is an excellent example of the graphic
method of presenting the results of scientific investigations. At the
lower part of the diagram there are drawn to scale half-sections of a
long and of a short gun. The horizontal line above is marked in equal
parts representing feet numbered from the base of the projectiles. The
upright line on the left numbered at every fourth division is the scale
for the pressures in tons per square inch on the base of the projectile,
and these are represented by the height of the plain curves above the
horizontal line at each point in the travel of the shot. The dotted
lines represent in the same way, but _not_ on the same scale as the
former, the velocity with which the base of the projectile passes every
point in the chase. The figures 2, 4, and 6 on the upright line at the
right-hand side refer only to pressures: the velocities scale is such
that the point where the dotted meets the right-hand one is 2,680 units
above the horizontal line, as the middle upright in the same way is
1,561 high, and the heights of the dotted lines represent each on the
same scale the velocities of the bases of the projectiles at the
corresponding parts of the chases. The shorter gun has the rifled part
of the chase 15·4 calibres long; the corresponding part of the longer is
nearly 33 calibres. The short 7–inch gun has a charge of 30 lbs. of
gunpowder, and its projectile weighed 115 lbs. The longer 6–inch gun was
not charged with gunpowder, but with the more powerful modern explosive
_cordite_ (see Index), of which there was 19·5 lbs., and its projectile
weighed 100 lbs. The charges were so adjusted that the shots had the
same initial maximum pressure of 20 tons per square inch applied to
them. Now the cordite, though much more powerful than gunpowder (that
is, a given weight will produce far more gas), is slower in its
ignition, continuing longer to supply gas. The maximum pressure, 20 tons
in both cases, is suddenly attained by the gunpowder gases, when the
shot has hardly moved 6 inches onward, and the pressure declines rapidly
as the moving shot leaves more space for the gas; while the cordite
gases produce their greatest pressure more gradually at a part where the
shot is already about 20 inches on its way, and not only do their
highest pressures continue for a greater distance,—but the decline is
far less rapid than in the other case. It will be observed by the
intersection of the dotted lines, that when the shots in each case have
moved about 2 ft. their velocities are equal. They finally leave the
muzzles with the velocities marked on the diagram, and if the reader
will apply the formula given on page 174 he will obtain their respective
energies in _foot-lbs._; but for large amounts like these it is more
usual to state the energy in _foot-tons_, which of course will be
arrived at by dividing the _foot-lbs._ numbers by 2,240, and these will
work out in the one case to 4978·9 ft.-tons, and in the other to 1942·5
ft.-tons. The shot from the long gun will therefore have more than 2½
times the destructive power of the other.

[Illustration:

  FIG. 98.—_Diagram of Velocities and Pressure._
]

The operations required in constructing guns are multiform, and have to
be very carefully conducted so that the workmanship shall be of the best
quality. The finest ores are selected for reduction, and the steel is
obtained by the Siemens-Martin process already described. It must be
free from sulphur and phosphorus, and contain such proportions of
carbon, silicon, and manganese as experience has shown to be best, and
its composition is ascertained by careful chemical analysis before it is
used. The fluid steel is run into large ladles lined with fire-brick,
and provided with an opening in the bottom from which the metal can be
allowed to run out into the _ingot_ moulds, the size and proportions of
these being in accordance with the object required; some admitting of as
much as 80 tons at one operation. When a barrel or hoop is required of
not less than 6 inches internal diameter the ingot is cut to the
required length and roughly bored. The ingot is then heated, a long
cylindrical steel bar is put through the hole, and under a hydraulic
press the hot metal is squeezed into greater length and less diameter.
The hole first bored through the ingot is of somewhat greater, and the
steel bar (called a mandril) of less, diameter than required in the
finished piece. Portions are cut from each end of what is now called the
_forging_ and subjected to mechanical tests: if these are satisfactory,
the forging is rough bored and turned on the outside. It is then
annealed, by being heated and allowed to cool very slowly. The next
operation is to _harden_ the metal by raising it to a certain
temperature, at which it is immersed in rape oil until cold. Then the
piece is again annealed, and fine-turned and bored. All these operations
have to be performed not only on the barrel, but also on each hoop,
before the hoops are shrunk on, and the greatest nicety of measurement
is required in each piece. Then the gun has to be turned on the outside,
the screw for the breech piece cut, the bore rifled, etc. The object of
the annealing is to relieve the metal from internal strains. It will not
be wondered at that months are required for the construction of the
larger kind of guns. Thus at Elswick a 6 in. quick firing gun, upon
which men are employed night and day, cannot be completed in less than
five months, and sixteen months are required for making a 67–ton gun.

We may take as an illustration of the progress of modern artillery one
of the products of the Elswick factory which has just been referred to,
and for which the demand from all quarters has been unprecedentedly
great, namely, the 4·7 inch gun. This weapon is mounted in various
manners according to the position it has to occupy, whether for a land
defence, or on ship-board between decks, or on the upper deck. The
arrangement shown in Fig. 99, which is reproduced from Messrs. Lloyd &
Hadcock’s work, is known as the centre pivot mounting, and is suitable
for such a position as the upper deck of a ship. The reader should
compare the proportions and mounting of this weapon with those of the
old 32–pounder sketched in Fig. 90, observing the very much greater
comparative length of the modern weapon, and the mechanism for elevating
and training it (which, however, the scale of the drawing crowds into
too small a space to show as it deserves). C is a projection from the
breech, to which is attached the piston of the recoil press; at T is the
handle for training, which actuates a worm at V; the elevation is
regulated by the turning of the four-armed wheel. The long chase of the
gun projects in front; but the mounting and the breech machinery are
protected by shields of thick steel, of which the sections of two plates
are denoted by the dark upright parts in front. These are fixed; but a
movable plate above the gun can be raised or lowered into an inclined
position, for better taking sights. In the figure this is shown as open
and in a horizontal position. This gun is provided with sights by which
it can be aimed at night; that is, the sights can be illuminated by
small electric lamps suitably placed; the wires connecting these with
voltaic battery cells carried on the mounting are indicated. The figure
represents the gun as constructed about 1893, but the improvements that
are continually being made have brought about some modifications in the
details.

[Illustration:

  FIG. 99.—_Elswick 4·7 inch Q. F. Gun on Pivot Mounting._
]

Very notable among the productions of the great Elswick factory are the
_quick firing_ guns. These were at first confined to guns of small
calibre, such as the 6–pounders. They are, of course, all
breech-loaders, and the powder and shot are both contained in a single
metallic cartridge case. A more formidable weapon of the same class is
the 45–pounder rapid firing gun, which, like the rest, is constructed
entirely of steel, with a total length of 16 ft. 2½ in., a calibre of
4·724 in., and a length of bore equal to 40 diameters. The weight of
this gun is 41 cwt., and it throws a shell of 45 lbs. weight with a
12–lb. charge of gunpowder. Quick firing guns having a calibre of 6 in.
are now also made in great numbers for arming our ironclads. The breech
block in the quick firing guns turns aside on a hinge, and after the
introduction of the cartridge it is closed and screwed up to its place
by a slight turn of a handle. The piece is then pointed and trained by
aid of mechanical gearing as in the case of the heavier guns. But Mr.
Hotchkiss has introduced a simpler method of elevating and training his
3–pounder and 6–pounder quick firing guns, by attaching to the rear, and
unaffected by the recoil, a shoulder piece against which the marksman
can lean, and move the weapon as he takes his aim. Though these guns
weigh respectively 4½ cwt. and 7 cwt., they can thus be pointed with the
greatest ease. The firing is done by pulling a trigger in what seems
like the stock of a pistol. The empty cartridge case is automatically
extracted from the firing chamber by the act of opening the breech, and
it drops to the ground. Ten or twelve rounds per minute can be fired
from these guns, and Lord Armstrong has advocated the use of a number of
them for naval armament in preference to that of a few ordinary
breech-loaders of more unwieldy dimensions. He has calculated that in a
given time a far greater weight of metal can be projected from a vessel
armed with quick firing guns than from one provided only with the
heavier class of cannons.

The breech pieces in the Elswick guns are closed on the “interrupted
screw” system—that is, a very large screw thread of V-shaped section is
cut in the barrel at the breech end, and a corresponding thread on the
principal part of the breech block, which is, of course, capable of
rotating about the axis. The screw threads, however, are not continuous,
segments parallel to the axis being cut away, the spaces in the outer
thread corresponding with the projecting parts in the inner, and _vice
versâ_, so that when the block is pushed home, one very small part of a
turn suffices to engage all the threads. The screw is also made conical,
and is so cut into steps, as it were, that great resisting power is
brought into play. The Elswick guns are provided with hydraulic buffers
for checking the recoil, and the principle is applied in various
modified forms. In some cases the pistons allow for the water a passage,
which towards the end gradually diminishes. This is the arrangement for
the 3–pounder rapid firing Hotchkiss gun, and the force of the recoil is
made at the same time to compress two springs, which serve to return the
gun to the firing position. This very handy gun is said to be able to
fire twenty rounds per minute. In Mr. Vavasseur’s plan of mounting, the
recoil is checked by ports, or openings, in the piston of a hydraulic
cylinder being gradually closed, which is easily arranged by making a
spiral groove within the cylinder, which gives a small axial motion to
part of the piston.

[Illustration:

  FIG. 100.—_The Moncrieff Gun raised and ready for firing._
]

[Illustration:

  FIG. 101.—_Moncrieff Gun lowered for loading._
]

An extremely effective plan for the defence of coasts and harbours was
originated by Colonel Moncrieff, when about 1863 he contrived a method
of mounting large guns on the disappearing system, by which almost
complete protection against hostile fire is given to both gun and
gunners. He utilizes the recoil as a means of bringing the gun down into
a protected position the moment it has been fired, and retains this
energy by a simple arrangement until the piece has been reloaded, when
it is allowed to expend itself by again raising the gun above the
parapet into the original firing position. The configuration and action
of Colonel Moncrieff’s gun-carriage will be understood by an inspection
of the annexed illustrations, where in Fig. 100 is shown the gun raised
above the parapet and ready for firing. When the discharge takes place,
the gun, if free, would move backwards with a certain speed, but the
disposition of the mounting is such that this initial velocity receives
no _sudden_ check, the force being expended in raising a heavy
counterpoise, and at the same time the gun is permitted to descend,
while maintaining a direction parallel to its firing position. At the
end of the descent, which, it must be understood, is caused by the force
of the recoil, and not by the counterpoise, for this more than balances
the weight of the gun, the latter is retained as shown in Fig. 101 until
it has been reloaded; and when it has again to be fired, it is released
so as to allow the descent of the counterpoise to raise it once more
into position. The great advantage of this invention is the protection
afforded to the artillerymen and gun while loading; and even the aiming
can be accomplished by mirrors, so that the men are exposed to no
danger, except from “vertical fire,” which involves but little risk.

Colonel Moncrieff took out a patent for his invention in 1864, but
committed the practical working out of his idea to the firm of Sir W. G.
Armstrong & Co., in whose hands the design was ultimately transformed
from the original somewhat cumbersome arrangement of the mounting into
the compact and manageable form shown in Fig. 102, which represents a
13·9 inch 68–ton breech-loading disappearing gun on the Elswick
hydro-pneumatic mounting. The principle of hydraulic power is fully
explained in our article on that subject, and an example of its
application to cranes as devised by Sir W. Armstrong is there described.
When guns began to be made very large, and projectiles weighing several
cwts. had to be dealt with, the application of power in some form became
essential for loading, running out, elevating, training, etc.; and
though steam-power naturally was first used, hydraulic power was adopted
at Elswick, and has been there applied to the mountings of large guns
with the greatest success by Mr. G. W. Rendel. To mention the various
arrangements in which this power is applied, or to attempt any
description of the elaborate machinery by which it is regulated, would
carry us far beyond our limits. But the powerful weapon depicted in Fig.
102 is designed to be worked only by the manual effort of a few men. In
this mounting the pressure of condensed air sustains the gun in the
firing position; that pressure, acting upon the water in the recoil
presses, having previously forced up their rams so as to turn into a
nearly vertical position the strong brackets or beams on which the
trunnions are supported. The recoil is checked in the usual way by the
forcing of the water through small ports or valves as the ram descends,
but these valves are so arranged that the water is in part forced back
into the air chamber, and there recompresses the air, to restore the
power for again raising the gun. The pressure in the air chamber when
the gun is down may be about 1,400 lbs. per square inch; when it is up
this will be reduced to perhaps one half by the expansion of the air in
doing work. We have here the reaction of compressed air taking the place
of the gravity of the counterpoise originally designed. There are in
this hydro-pneumatic mounting a number of adjusting appliances, such as
forcing pumps, brakes, etc., for regulating the pressures, or quantity
of liquid, as, for instance, when lowering the gun without any recoil
action in operation. Then again, with any change in the weight of
projectile or in the powder charge, there would be a corresponding
change in the power of the recoil, and therefore the necessity for
compensatory adjustments, which are made with great readiness. The
nicety with which the parts are adapted to each other in this mounting
must be obvious, when we observe the magnitude of the mass to be moved
with the least delay, and brought to rest, quite gently and exactly, in
a new position. Details cannot here be given even of the method by which
the valves in the recoil cylinders are automatically controlled for this
purpose. Means are also supplied for setting the gun, while still in its
protected position, to the required angle of elevation or depression.
The adjustment is made by the long rods attached near the breech and set
at their lower ends to the position giving the intended angle to the
raised gun. The varied and powerful strains to which the parts of this
mechanism are subject, and which have had to be calculated and provided
for, may be inferred from the enormous recoil energy of the gun, which
under ordinary conditions amounts to no less than 730 foot-tons. The gun
is provided with ordinary, and also with reflecting, sights, so that no
one need be exposed to the enemy’s fire. Protective armour above the gun
is not required, as the pit itself being usually on some elevation is
imperceptible to the enemy, and the gun is visible but for a few
seconds, forming a quite inconspicuous object. The pit in which the gun
is mounted is commonly lined with concrete. Italy, England, Norway,
Japan and other countries have appreciated the advantages of the
disappearing system in providing the most powerful coast defences yet
devised, and a great many guns have been mounted on this principle.

[Illustration:

  FIG. 102.—_68–ton Gun on Elswick Hydro-Pneumatic Mounting._
]

An extraordinary piece of ordnance is represented in Fig. 103. It is one
of two huge mortars, the idea of which presented itself to Mr. Mallet
during the Crimean War, the intention being to throw into the Russian
lines spherical shells a yard in diameter, which would, in fact, have
constituted powerful mines, rendering it impossible for the
fortifications to continue tenable. Mallet’s original design was to
project these shells from mortars of no less than 40 tons weight. When
it was pointed out that the transport of so heavy a mass would be
impracticable, the design was changed to admit of the mortar being made
in pieces not exceeding eleven tons in weight, and built up where
required. During the most active period in the siege of Sebastopol this
plan was submitted to Lord Palmerston, who at once ordered two of these
apparently formidable pieces to be constructed, without waiting for
official examinations of the scheme, and the usual reports of
experts,—promptness in this case being considered of the utmost
importance. A contract was made with a private firm, who undertook to
deliver them in ten weeks. But the difficulties attending such
constructions not being understood at the time, delays arose, the
contractors failed, and two years elapsed before the mortars were
completed. In the meantime peace had been concluded, and the mortars
were never fired against any hostile works; but experiments were made
with one of them at Woolwich. The heaviest of the shells it was intended
to project weighed 2,940 lbs., and for this it was proposed to use a
charge of 80 lbs. of gunpowder. In the experiments the charges first
used were low, but gradually increased: when it was found that after
every few rounds repairs became necessary in consequence of the weak
points in the construction, and after the nineteenth round the mortar
was so much damaged that the trials were definitely discontinued. The
other mortar, though mounted, was never fired, but remains at Woolwich,
an object of some interest to artillerists, especially since there has
been some talk of reverting to this very old-fashioned form of ordnance
as a means of attacking ironclads in their most vulnerable direction by
the so-called vertical fire. In one of the rounds of the Mallet mortar
tried at Woolwich, a shell weighing 2,400 lbs. was thrown by a charge of
70 lbs. of gunpowder a distance of more than a mile and a half, and it
buried itself in the soil to a very great depth.

[Illustration:

  FIG. 103.—_Mallet’s Mortar_
]

For high-elevation firing, howitzers will more probably be the form of
ordnance most in use. The range of the howitzer is determined by the
angle at which it is elevated, whereas with the mortar it is chiefly by
variation of the powder charge that the aim is adjusted. Many of the old
short 9 in. muzzle-loaders have already been converted into 11 in.
rifled howitzers, and these are likely to prove of great service in
defending our harbours and channels against war vessels.

Some account has been given in a preceding article of the great steel
works of Krupp & Co. at Essen, and the place has been noted as one of
the greatest gun factories in the world during the second half of our
century. The process there practised of casting crucible steel ingots,
and already described, is precisely that used in the first stage of
gun-making. The steel for guns put into the crucibles is a carefully
adjusted mixture of one quality of iron puddled into steel and subjected
to certain treatment; the other portion is made from a different quality
of iron from which all the carbon has been puddled out. The cast ingot
is forged under a great steam hammer, bored, turned, and steel hoops
shrunk upon it, in several layers, and other operations are performed
upon it like those which have already been mentioned. A 14 in. gun is
said to require sixteen months for its manufacture, and its cost to be
about £20,000.

[Illustration:

  FIG. 104.—_32–pounder Krupp Siege Gun, with Breech-piece open._
]

Artillerists had long carried on a warm controversy as to the relative
merits of wrought iron and steel in gun construction, the latter
material being regarded with shyness on account of its want of
uniformity as formerly produced. Krupp however began as early as 1847 to
make guns of his excellent crucible steel, and through bad report and
good report confined himself to this material until, it is asserted, by
1878 he had supplied over 17,000 steel guns of all calibres. He began by
making a 3–pounder gun, but soon produced pieces of larger size, all of
which were bored and turned out of solid masses of metal. At a later
period the plan of shrinking on strengthening hoops of steel was
adopted. The Krupp guns have found extensive favour, and many very heavy
ones have been made, some indeed of greater weight than the 110–ton
Armstrong; but the excess of weight is due to the mass of metal which
the Krupp construction of the breech mechanism requires. Thus Krupp’s
120–ton gun has a muzzle energy of but 45,796 foot-tons, while that of
the Elswick piece is 55,105 foot-tons.

[Illustration:

  FIG. 105.—_The Citadel of Strasburg after the Prussian Bombardment._
]

The breech arrangement in the Krupp guns consists of a lateral slot into
which slides a closing block after the charge has been inserted from the
rear. An obsolete form of this breech piece is seen in Fig. 104, which
represents a 32–pounder gun such as was used in sieges by the Prussians
in the Franco-German War. It will be observed here that the slot and
breech piece are of rectangular form; but this shape, causing the piece
to be weak where most strength was required, was afterwards altered into
a D-shaped section, the curved side being of course to the rear. That
difficulty which baffled the earliest attempts at breech-loading is the
same that has given much trouble to modern gunmakers. It consists in so
closing the breech that no escape of the powder gases can take place
there at the moment of discharge. When we remember that the momentary
pressure of the gases in the powder chamber may amount to more than 40
tons on the square inch, we can well understand the enormous velocity
with which they will rush forth from even the smallest interspace
between the base of the gun and the breech block, but we can hardly
realise without actual inspection the mechanical action they produce in
their passage: when once the escape occurs, a channel is cut in the
metal as if part had been removed by an instrument, and the piece in
that condition is disabled for further use. Several devices are in use
obtaining perfect closure of the breech, which is technically called
_obturation_ (Latin, _obturare_, to close up). One of these consists in
fitting closely into the circumference of the bore a ring of very
elastic steel, turned up at the edges towards the powder chamber. The
gas pressure forces the edge of this ring still more closely against the
interior of the powder chamber, much in the same way as the Bramah
collar acts in the hydraulic press (see Fig. 165). The shaded circle
shown on the breech piece in Fig. 104 is an additional device for
obtaining obturation. The Broadwell ring, as the above-mentioned
contrivance is called, is not used in English guns, but another plan of
obtaining a gas-joint has been much adopted, in which a squeezable pad
is by compression forced outwards to close up the bore.

A very long range was claimed for Krupp’s guns at the time of the
Franco-German War, for at the siege of Paris (1870) it was said they
could hurl projectiles to the distance of five miles, though probably
there was some exaggeration in this statement. There is no doubt however
that the Prussians had very effective and powerful artillery, as may be
gathered from Fig. 105, which is taken from a photograph of part of the
fortifications of Strasburg after the bombardment of that fortress. The
explosive shells used by the Prussians against masses of troops were not
precisely segment shells of the form already described, but the
principle and effect were the same, for the interior was built up of
circular rings, which broke into many pieces when the shell exploded.

Out of the very numerous forms in which modern ordnance is constructed,
we have been able to select but a few examples for illustration and
description. These will suffice, it is hoped, to give an idea of the
progress that the century has witnessed. It would be beyond our scope to
give details of the ingenious mechanical devices that have come to be
applied to guns: such as the breech-closing arrangements, the various
ways in which recoil is controlled and utilized, etc. A good
illustration, had space permitted, of the scientific skill applied to
ordnance would be found in the contrivances fitted to certain
projectiles in order to determine their explosion at the proper moment.
These are very different from the cap or time fuse that did duty in the
first half of the century. We have indeed said little of the projectiles
themselves beyond mention of the Palliser chilled shot and the obsolete
studded projectiles. We have not explained how bands of copper, or other
soft metal, are put round a certain part of the shot or shell, in order
that, being forced into the grooves, the axial rotation may be imparted,
or how windage is prevented by “gas checks” attached to the base of the
projectiles. We must now be contented to conclude this section by
showing the structure of two kinds of explosive shells which have been
much used.

Shrapnel shell takes its name from Lieutenant Shrapnel, who was its
inventor about the end of last century, but the projectile began to be
used only in 1808. Fig. 105_a_ is a section showing the shell as a case
containing a number of spherical bullets, of which in the larger shells
there are very many, the interspaces being filled with rosin, poured in
when melted; the bullets are thus prevented from moving about. The
figure shows the shell without the fuse or percussion apparatus, which
screws into the hollow at the front. The bursting charge of gunpowder is
behind the bullets, and when it explodes they travel forward with a
greater velocity than the shell, but with trajectories more or less
radiating, carrying with them wide-spreading destruction and death.

A shrapnel shell may be said to be a short cannon containing its charge
of powder in a thick chamber at the breech end; the sides of the fore
part of the shell are thinner than those of the chamber, and may be said
to form the barrel of the cannon. This cannon is loaded up to the muzzle
with round balls, which vary with the shell in size. An iron disc
between the powder and the bullets represents the wad used in ordinary
fowling-pieces. A false conical head is attached to the shell, so that
its outward appearance is very similar to that of an ordinary
cylindro-conoidal shell: that is to say, it looks like a very large long
Enfield bullet. The spinning motion which had been communicated to the
shell by the rifling of the gun from which it had been fired causes the
barrel filled with bullets to point in the direction of the object at
which the gun has been aimed. Consequently, when the shrapnel shell is
burst, or rather fired off, the bullets which it contained are streamed
forward with actually greater velocity than that at which the shell had
been moving; and the effect produced is similar to firing grape and
canister from a smooth-bore cannon at a short range.

[Illustration:

  FIG. 105_a_.—_The Shrapnel and Segment Shells._
]

Segment shells were first brought into use by Lord Armstrong in 1858 in
connection with his breech-loading guns. The segment shell consists of a
thin casing like a huge conical-headed thimble, with a false bottom
attached to it. It is filled with small pieces of iron called
“segments,” cast into shapes which enable them to be built up inside the
outer casing into two or more concentric circular walls. The internal
surface of the inmost wall forms the cavity of the compound or segment
shell, and contains the bursting charge. The segment shell is fitted
with a percussion fuse, which causes it to explode when it strikes. In
the shrapnel shell, the powder charge is situated in rear of the
bullets, and consequently produces the chief effect in a forward
direction. In the segment shell, the powder is contained inside the
segments, and therefore produces the chief effect in a lateral
direction. When the shrapnel shell is burst at the right moment, its
effect is greatly superior to that of the segment shell; on the other
hand, the segment shell, when employed at unknown or varying distances,
is far more unlikely to explode at the proper time.

Shrapnel and segment shells can be used with field artillery, _i.e._,
9–pounders, 12–pounders, 16–pounders; and also with heavy rifled guns in
fortresses, viz., 40–pounders, 64–pounders, 7–in. and 9–in. guns. But
the conditions of their service are very different in each case. With
regard to field artillery, the distance of the enemy is rarely known,
and is constantly changing, and hence the men who have to adjust the
fuses would probably be exposed to the fire of the enemy’s artillery,
and, consequently, could not be expected to prepare the fuses with the
great care and nicety which are absolutely necessary to give due effect
to the shells. There are, however, some occasions when the above
objections would not hold good—as, for instance, when field artillery
occupy a position in which they wait the attack of an enemy advancing
over ground in which the distances are known.

Segment shells require no adjustment of their percussion fuse. They
enable the artillerymen to hit off the proper range very quickly, since
the smoke of the shell which bursts on striking tells them at once
whether they are aiming too high or too low.

With regard, however, to the service of heavy rifled guns in fortresses,
the conditions are quite different. In the first place, the distance of
all objects in sight would be well known beforehand; and in the second
place, the fuses of the shells would be carefully cut to the required
length in the bomb-proofs, where the men would be completely sheltered.
The 7–in. shrapnel contains 227 bullets, and a 9–in. shrapnel would
contain 500 bullets of the same size, and these shells could be burst
with extraordinary accuracy upon objects 5,000, 6,000, or 7,000 yards
off.


                            _MACHINE GUNS._

The name of machine guns has been applied to arms which may be regarded
as in some respects intermediate between cannons and rifles, since in
certain particulars they partake of the nature of both. Like the former,
they are fired from a stand or carriage, and in some of their forms
require more than one man for their working: in the calibre of their
barrels and the weight of their projectiles, they are assimilated to the
rifle, but they are capable of pouring forth their missiles in a very
rapid succession—so rapid indeed as practically to constitute volley
firing. The firing mechanism of the machine gun has always an automatic
character, but the rifle has acquired this feature, so that it cannot be
made a distinguishing mark: on the other hand, since machine guns have
been made to discharge projectiles of such weights as 1 lb. or 3 lb.
there is nothing to separate them from quick-firing ordnance unless it
be the automatic firing.

The idea of combining a number of musket-barrels into one weapon, so
that these barrels may be discharged simultaneously or in rapid
succession, is not new. Attempts were made two hundred years ago to
construct such weapons; but they failed, from the want of good
mechanical adjustments of their parts. Nor would the machine gun have
become the effective weapon it is, but for the timely invention of the
rigid metallic-cased cartridge. Several forms of machine guns have in
turn attracted much attention. There is the Mitrailleur (or
Mitrailleuse), of which so much was heard at the commencement of the
Franco-German War, and of whose deadly powers the French managed to
circulate terrible and mysterious reports, while the weapon itself was
kept concealed. Whether this arose from the great expectations really
entertained of the destructive effects of the mitrailleur, or whether
the reports were circulated merely to inspire the French troops with
confidence, would be difficult to determine. Our own policy in regard to
new implements of war is not to attempt to conceal their construction.
Experience has shown that no secret of the least value can long be
preserved within the walls of an arsenal, although the French certainly
apparently succeeded in surrounding their invention with mystery for a
while. The machine gun, or “battery,” invented by Mr. Gatling, an
American, is said by English artillerists to be free from many defects
of the French mitrailleur. In 1870 a committee of English military men
was appointed to examine the powers of several forms of mitrailleur,
with a view to reporting upon the advisability or otherwise of
introducing this arm into the British service. They recommended for
certain purposes the Gatling battery gun.

[Illustration:

  FIG. 105_b_.—_The Gatling Gun.—Rear View._
]

In the Gatling the barrels, ten in number, are distinct and separate,
being screwed into a solid revolving piece towards the breech end, and
passing near their muzzles through a plate, by which they are kept
parallel to each other. The whole revolves with a shaft, turning in
bearings placed front and rear in an oblong fixed frame, and carrying
two other pieces, which rotate with it. These are the “carrier” and the
lock cylinder. Fig. 105_b_ gives a rear view, and Fig. 105_c_ a side
view, of the Gatling battery gun. The weapon is made of three sizes, the
largest one firing bullets 1 in. in diameter, weighing ½ lb., the
smallest discharging bullets of ·45 in. diameter. The small Gatling is
said to be effective at a range of more than a mile and a quarter, and
can discharge 400 bullets or more in one minute. Mr. Gatling thus
describes his invention:

“The gun consists of a series of barrels in combination with a grooved
carrier and lock cylinder. All these several parts are rigidly secured
upon a main shaft. There are as many grooves in the carrier, and as many
holes in the lock cylinder, as there are barrels. Each barrel is
furnished with one lock, so that a gun with ten barrels has ten locks.
The locks work in the holes formed in the lock cylinder on a line with
the axis of the barrels. The lock cylinder, which contains the lock, is
surrounded by a casing, which is fastened to a frame, to which trimmers
are attached. There is a partition in the casing, through which there is
an opening, and into which the main shaft, which carries the lock
cylinder, carrier, and barrels, is journaled. The main shaft is also at
its front end journaled in the front part of the frame. In front of the
partition in the casing is placed a cam, provided with spiral surfaces
or inclined planes.

“This cam is rigidly fastened to the casing, and is used to impart a
reciprocating motion to the locks when the gun is rotated. There is also
in the front part of the casing a cocking ring which surrounds the lock
cylinder, is attached to the casing, and has on its rear surface an
inclined plane with an abrupt shoulder. This ring and its projection are
used for cocking and firing the gun. This ring, the spiral cam, and the
locks make up the loading and firing mechanism.

“On the rear end of the main shaft, in rear of the partition in the
casing, is located a gear-wheel, which works to a pinion on the
crank-shaft. The rear of the casing is closed by the cascable plate.
There is hinged to the frame in front of the breech-casing a curved
plate, covering partially the grooved carrier, into which is formed a
hopper or opening, through which the cartridges are fed to the gun from
feed-cases. The frame which supports the gun is mounted upon the
carriage used for the transportation of the gun.

“The operation of the gun is very simple. One man places a feed-case
filled with cartridges into the hopper; another man turns the crank,
which, by the agency of the gearing, revolves the main shaft, carrying
with it the lock cylinder, carrier, barrels, and locks. As the gun is
rotated, the cartridges, one by one, drop into the grooves of the
carrier from the feed-cases, and instantly the lock, by its impingement
on the spiral cam surfaces, moves forward to load the cartridge, and
when the butt-end of the lock gets on the highest projection of the cam,
the charge is fired, through the agency of the cocking device, which at
this point liberates the lock, spring, and hammer, and explodes the
cartridge. As soon as the charge is fired, the lock, as the gun is
revolved, is drawn back by the agency of the spiral surface in the cam
acting on a lug of the lock, bringing with it the shell of the cartridge
after it has been fired, which is dropped on the ground. Thus, it will
be seen, when the gun is rotated, the locks in rapid succession move
forward to load and fire, and return to extract the cartridge-shells. In
other words, the whole operation of loading, closing the breech,
discharging, and expelling the empty cartridge-shells is conducted while
the barrels are kept in continuous revolving movement. It must be borne
in mind that while the locks revolve with the barrels, they have also,
in their line of travel, a spiral reciprocating movement; that is, each
lock revolves once and moves forward and back at each revolution of the
gun.

“The gun is so novel in its construction and operation that it is almost
impossible to describe it minutely without the aid of drawings. Its main
features may be summed up thus: 1st.—Each barrel in the gun is provided
with its own independent lock or firing mechanism. 2nd.—All the locks
revolve simultaneously with the barrels, carrier, and inner breech, when
the gun is in operation. The locks also have, as stated, a reciprocating
motion when the gun is rotated. The gun cannot be fired when either the
barrels or locks are at rest.”

There is a beautiful mechanical principle developed in the gun, viz.,
that while the gun itself is under uniform constant rotary motion, the
locks rotate with the barrels and breech, and at the same time have a
longitudinal reciprocating motion, performing the consecutive operations
of loading, cocking, and firing without any pause whatever in the
several and continuous operations.

The small Gatling is supplied with another improvement called the “drum
feed.” This case is divided into sixteen sections, each of which
contains twenty-five cartridges, and is placed on a vertical axis on the
top of the gun. As fast as one section is discharged, it rotates, and
brings another section over the feed aperture, until the whole 400
charges are expended.

[Illustration:

  FIG. 105_c_.—_The Gatling Gun.—Front View._
]

After a careful comparison of the effects of field artillery firing
shrapnel, the committee concluded that the Gatling would be more
destructive in the open at distances up to 1,200 yards, but that it is
not comparable to artillery in effect at greater distances, or where the
ground is covered by trees, brushwood, earthworks, &c. The mitrailleur,
however, would soon be knocked over by artillery if exposed, and
therefore will probably only be employed in situations under shelter
from such fire. An English officer, who witnessed the effects of
mitrailleur fire at the battle of Beaugency, looks upon the mitrailleur
as representing a certain number of infantry, for whom there is not room
on the ground, suddenly placed forward at the proper moment at a
decisive point to bring a crushing fire upon the enemy. Many other
eye-witnesses have spoken of the fearfully deadly effect of the
mitrailleur in certain actions during the Franco-German War.

Mr. Gatling contends that, shot for shot, his machine is more accurate
than infantry, and certainly the absence of nerves will ensure
steadiness; while so few men (four) are necessary to work the gun that
the exposure of life is less. No re-sighting and re-laying are necessary
between each discharge. When the gun is once sighted its carriage does
not move, except at the will of the operator; and the gun can be moved
laterally when firing is going on, so as to sweep the section of a
circle of 12° or more without moving the trail or changing the wheels of
the carriage. The smoke of battle, therefore, does not interfere with
its precision.

Whatever may be the part this new weapon is destined to play in the wars
of the future, we know that every European Power has now provided itself
with some machine guns. The Germans have those they took from the
French, who adhere to their old pattern. The Russians have made numbers
of Gatlings, each of which can send out, it is said, 1,000 shots per
minute, and improvements have been effected, so as to obtain a lateral
sweep for the fire.

[Illustration:

  FIG. 105_d_.—_The Montigny Mitrailleur._
]

A competitor to the Gatling presents itself in the Belgian mitrailleur,
the Montigny, Fig. 105_d_. This gun, like the Gatling, is made of
several different sizes, the smallest containing nineteen barrels and
the largest thirty-seven. The barrels are all fitted into a wrought iron
tube, which thus constitutes the compound barrel of the weapon. At the
breech end of this barrel is the movable portion and the mechanism by
which it is worked. The movable portion consists mainly of a short
metallic cylinder of about the same diameter as the compound barrel, and
this is pierced with a number of holes which correspond exactly with the
position of the gun-barrels, of which they would form so many
prolongations. In each of the holes or tubes a steel piston works
freely; and when its front end is made even with the front surface of
the short cylinder, a spiral spring, which is also contained in each of
the tubes, is compressed. The short cylinder moves as a whole backwards
and forwards in the direction of the axis of the piece, the movement
being given by a lever to the shorter arm of which the movable piece is
attached. When the gun is to be loaded this piece is drawn backwards by
raising the lever, when the spiral springs are relieved from
compression, and the heads of the pistons press lightly against a flat
steel plate in front of them. The withdrawal of the breech-block gives
space for a steel plate, bored with holes corresponding to the barrels,
to be slid down vertically; and this plate holds in each hole a
cartridge, the head of each cartridge being, when the plate has dropped
into its position, exactly opposite to the barrel, into which it is
thrust, when the movable breech-block is made to advance. The anterior
face of this breech-block is formed of a plate containing a number of
holes again corresponding to the barrels, and in each hole is a little
short rod of metal, which has in front a projecting point that can be
made to protrude through a _small_ aperture in the front of the plate,
the said small apertures exactly agreeing in position with the centres
of the barrels, and being the only perforations in the front of the
plate. The back of the plate has also openings through which the heads
of the pistons can pass, and by hitting the little pieces, or strikers,
cause their points to pass out through the apertures in front of the
plate, and enter the base of the cartridges, where _fulminate_ is
placed. The plate filled with cartridges has a bevelled edge, and the
points of the strikers are pushed back by it as it descends. The heads
of the pistons are separated until the moment of discharge from the
recesses containing the strikers by the flat steel plate or shutter
already mentioned. The effect, therefore, of pushing the breech-block
forward is to ram the cartridges into the barrels, and at the same time
the spiral springs are compressed, and the heads of the pistons press
against the steel shutter which separates them from the strikers, so
that the whole of the breech mechanism is thus closed up. When the piece
is to be fired a handle is turned, which draws down the steel shutter
and permits the pistons to leap forward one by one, and hit the
strikers, so that the points of the latter enter the cartridges and
inflame the fulminate. The shutter is cut at its upper edge into steps,
so that no two adjoining barrels are fired at once. The whole of the
thirty-seven barrels can be fired by one and a quarter turns of the
handle, which may, of course, be given almost instantly, or, by a slower
movement, the barrels can be discharged at any required rate.

The barrels of the machine guns we have described do not, as is
generally supposed, radiate; on the contrary, they are arranged in a
perfectly parallel direction. In consequence of this, the bullets are at
short ranges directed nearly to one spot. The Gatling gun was adopted as
a service weapon by the British navy, and in several minor actions it
had proved effective, but in its original form it was superseded by the
Gardner gun, in which the barrels are fixed horizontally side by side,
and are in number five or fewer; each barrel is able to fire 120 rounds
per minute. A new system of feed was afterwards applied to the Gatling
gun by Mr. Accles, by means of which this gun was greatly improved and
its rate of firing was increased to more than 1,000 rounds per minute;
indeed, 80 rounds have been fired from it within 2 seconds. The Gatlings
in this improved form have ten barrels, and are provided with feed
drums, each containing 104 cartridges, and capable, when empty, of being
almost instantly replaced by a full one. The contents of one drum can,
if necessary, be discharged in about 2¼ seconds, so that in this time
104 rifle bullets would be fired; or considerably more than the rate of
1,000 rounds per minute could easily be maintained. The weapon is so
mounted, that without moving its carriage it can be pointed at any angle
of elevation or depression, and through a considerable lateral range.

Mr. Nordenfelt has brought out a machine gun, which, on account of the
simplicity and strength of its firing mechanism, has proved the most
reliable weapon of its class, and it also has been adopted into the
British service, and indeed into that of nearly every nation in the
world. In this gun there are five barrels arranged as in the Gardner,
but the firing is operated by a lever working backwards and forwards at
the rate of 600 rounds per minute.

[Illustration:

  FIG. 105_e_.—_A Hotchkiss Gun._
]

In the firing of all these weapons, by turning a crank, or moving a
lever at one side, any attempt at exact aiming must obviously be
difficult if not impossible, from the liability of the gun to get moved.
Several designs have been proposed for making the firing mechanism
entirely automatic so as to require no effort on the part of the firer,
whose attention can then be directed solely to pointing the piece. It
would not be easy to explain in detail the way in which this is
accomplished in these very ingenious guns; for while the principle of
their action is sufficiently clear, namely, that the force of the recoil
is made to extract the spent cartridge, open the breech, insert a fresh
cartridge, close the breech, and fire the charge, the mechanism of the
reacting springs, etc., by which this is effected could scarcely, even
by the aid of elaborate diagrams, be made intelligible to any other than
a gunsmith. The Maxim is one of those automatic guns: it has but one
barrel, and after the first discharge it will go on firing with
marvellous rapidity the cartridges supplied to it in a continuous chain,
and this without any deviation from such direction as may be given to it
by the operator, for he has neither crank to turn nor lever to move, but
merely sits behind an iron shield directing the weapon at will, which,
without interference, fires hundreds of shots per minute from one
barrel, so long as the long bands of cartridges are supplied to it.

Mr. Nordenfelt and Mr. Hotchkiss have also both contrived quick firing
guns for 1–lb., 3–lb., and 6–lb. projectiles, and these, it has been
thought, will be of great service in naval warfare as against torpedo
boats.

Though the automatic mechanism, whereby the breech operations are all
performed by the force of the recoil of the barrel, which is allowed to
slide backwards, and is then returned to its place by a spring, is too
complicated for illustration here, mention may be made of a quite recent
device by which the recoil action is dispensed with, and the mechanism
so far simplified that scarcely more than half the number of parts in
the lock mechanism are required. Imagine a closed tube beneath the
barrel, parallel to it, and communicating with it only by a small boring
near the muzzle; through this opening the expanding gases will pass, in
a degree depending on its size and position, and by their action on a
piston near the breech, impulses are supplied that will actuate the lock
mechanism so long as cartridges are supplied, as they may be in a
continuous band. A weapon of this construction has been already tried,
and its discharges are so rapid that the sound of them is described as
being quite deafening. This plan appears to be equally applicable to
small arms, and to machine or field guns. A very effective gun of the
kind, which fires ordinary rifle bullets, has been contrived by Mr.
Hotchkiss, and is represented in Fig. 105_e_. It is capable of sending
forth as many as 1,000 shots in one minute.

Modern ordnance has required certain modifications in the making of
gunpowder, so that the original name of _powder_ would now hardly be
applicable at all. The large charges now used, if introduced in the form
of fine powder, would certainly shatter the guns from the suddenness of
the exploding force. Hence the material is made up into larger or
smaller masses, generally rounded like small pebbles. The explosive used
for the huge 110–ton guns presents itself in the form of
chocolate-coloured hexagonal prisms, two or three inches long and about
an inch in diameter. These are obtained by compressing the specially
prepared material into moulds with a hydraulic press. The reason for
this process is that, in order to obtain precision and uniformity in the
effects, not only must the composition of the powder be always the same,
but the size, shape, weight, and number of the several portions that
make up the charge must be invariable. It has not been found possible to
fire one of these monster guns many times without such signs of
deterioration as would suggest a short “life” for each of them. But the
greatest necessity for modern fire-arms is a smokeless powder or other
explosive. It is obvious that the advantages of quick firing, whether of
large or of small fire-arms, are greatly reduced if the soldier or
gunner is prevented by smoke from taking aim. The invention of a
smokeless gunpowder has several times been announced, and great advances
have, indeed, been made towards its realization. Certain compositions,
which appeared to meet the requirement of being practically smokeless,
have, however, been found liable to chemical changes, or to corrode the
bore, or to possess other objectionable properties. In this country the
explosive coming into use as best adapted for quick firing guns, etc.,
presents itself in appearance like whitish or grey strings, and has
hence received the name of _cordite_. The composition and mode of
manufacture of these new substitutes for gunpowder are not readily
disclosed, each military authority jealously guarding its own secrets.
The problem of smokeless powder has, however, been almost completely
solved, for at a military review that took place on the Continent in
1889, the discharge of the rifles (loaded with blank cartridges, of
course) is said to have been attended with no more smoke than the puff
of a cigar. The new invention will cause some changes in military
tactics, for the manœuvres formerly executed under cover of the battle
smoke will no longer be possible. Some particulars as to the nature of
smokeless powders will be found in the article on “Explosives.”

[Illustration]

[Illustration:

  FIG. 106.—_Harvey’s Torpedo. Working the Brakes._
]



                               TORPEDOES.


The notion of destroying ships or other structures by explosions of
gunpowder, contained in vessels made to float on the surface of the
water, or submerged beneath it, is not of very modern origin. Two
hundred and fifty years ago the English tried “floating petards” at the
siege of Rochelle. During the American War of Independence similar
contrivances were used against the British, and from time to time since
then “torpedoes,” as they were first termed by Fulton, have been
employed in warfare in various forms; but up to quite a recent period
the use of torpedoes does not appear to have been attended with any
decided success, and it is probable that but for the deplorable Civil
War in the United States we should have heard little of this invention.
During that bitter fratricidal struggle, however, when so much ingenuity
was displayed in the contrivance of subsidiary means of attack and
defence, the torpedo came prominently into notice, having been employed
by the Confederates with the most marked effects. It is said that
thirty-nine Federal ships were blown up by Confederate torpedoes, and
the official reports own to twenty-five having been so destroyed. This
caused the American Government to turn their attention to the torpedo,
and they became so convinced of the importance of this class of war
engine that they built boats expressly for torpedo warfare, and equipped
six _Monitors_ for the same purpose.

It has been well remarked that the torpedo plays the same part in naval
warfare as does the mine in operations by land. This exactly describes
the purpose of the torpedo where it is used defensively, but the
comparison fails to suggest its capabilities as a weapon of offence.
There are few occasions where a mine is made the means of attack, while
the torpedo readily admits of such an employment, and, used in this way,
it may become a conspicuous feature of future naval engagements. Many
forms of this war engine have been invented, but all may be classified,
in the first place, under two heads: viz., stationary torpedoes, and
mobile or offensive torpedoes; while independent distinctions may be
made according to the manner of firing the charge; or, again, according
to the mode of determining the instant of the explosion. The stationary
torpedo may be fixed to a pile or a raft, or attached to a weight; the
offensive torpedo may be either allowed to float or drift against the
hostile ships, or it may be propelled by machinery, or attached to a
spar of an ironclad or other vessel. The charge may be fired by a match,
by percussion, by friction, by electricity, or by some contrivance for
bringing chemicals into contact which act strongly upon each other, and
thus generate sufficient heat to ignite the charge. The instant of
explosion may be determined by the contact of the torpedo with the
hostile structure (in which case it is said to be “self-acting”), or by
clockwork, or at the will of persons directing the operations. In some
cases lines attached to triggers are employed; in others electric
currents are made use of.

[Illustration:

  FIG. 107.—_Submerged Torpedo._
]

In the American Civil War the stationary torpedoes at first laid down
were self-acting, that is, they were so arranged as to explode when
touched by a passing vessel. Such arrangements present the great
disadvantages of being as dangerous to friendly as to hostile ships. The
operation of placing them is a perilous one, and when once sunk, they
can only be removed at great risk. Besides this, they cannot be relied
on for certain action in time of need, as the self-acting apparatus is
liable to get out of order. The superiority of the method of firing them
from the shore when the proper instant arrived, became so obvious that
the self-acting torpedo was soon to a great extent superseded by one so
arranged that an observer could fire it at will, by means of a
trigger-line or an electric current. Similar plans had often been
previously employed or suggested. For example, during the war between
Austria and Italy the Austrian engineers at Venice had very large
electric torpedoes sunk in the channels which form the approaches to the
city. They consisted of large wooden cases capable of containing 400
lbs. of gun-cotton, moored by chains to a wooden framework, to which
weights were lashed that sufficed to sink the whole apparatus, Fig. 107.
A cable containing insulated wires connected the torpedo with an
electrical arrangement on shore, and the explosion could take place only
by the operator sending a current through these wires. The torpedo was
wholly submerged, so that there was nothing visible to distinguish its
position. There was no need of a buoy or other mark, as in the case of
self-acting torpedoes, to warn friendly vessels off the dangerous spot,
and therefore nothing appeared to excite an enemy’s suspicions. But it
is, however, absolutely necessary that the defenders should know the
precise position of each of their submarine mines, so that they might
explode it at the moment the enemy’s ship came within the range of its
destructive action. This was accomplished at Venice in a highly
ingenious manner, by erecting a camera obscura in such a position that a
complete picture of the protected channels was projected on a fixed
white table. While the torpedoes were being placed in their positions an
observer was stationed at the table, who marked with a pencil the exact
spot at which each torpedo was sunk into the water. Further, those
engaged in placing the torpedoes caused a small boat to be rowed round
the spot where the torpedo had been placed, so as to describe a circle
the radius of which corresponded to the limit of the effective action of
the torpedo. The course of the boat was traced on the picture in the
camera, so that a very accurate representation of the positions of the
submarine mines in the channels was obtained. Each circle traced on the
table was marked by a number, and the wire in connection with the
corresponding torpedo was led into the camera, and marked with the same
number, so that the observer stationed in the camera could, when he saw
the image of an enemy’s ship enter one of the circles, close the
electric circuit of the corresponding wire, and thus instantly explode
the proper torpedo. The events of the war did not afford an opportunity
of testing practically the efficiency of these preparations.

Another mode of exploding torpedoes from the shore has been devised by
Abel and Maury. It has the advantage of being applicable by night as
well as by day. The principle will be easily understood with the
assistance of the diagram, Fig. 108, in which, for the sake of
simplicity, the positions of only three torpedoes, 1, 2, 3, are
represented.

[Illustration:

  FIG. 108.—_Mode of Firing Torpedo._
]

In this arrangement two observers are required at different stations on
the shore. At each station—which should not, of course, be in any
conspicuous position—is a telescope, provided with a cross-wire, and
capable of turning horizontally about an upright axis. The telescope
carries round with it, over a circular table of non-conducting
substance, a metallic pointer which presses against narrow slips of
metal let into the circumference of the table. To each slip of metal a
wire passing to a torpedo is attached, and another wire is connected
with the axis of the pointer, so as to be put into electric contact with
each of the others when the pointer touches the corresponding piece of
metal on the rim of the table. The mode in which these wires are
connected with the torpedoes, the telescopes, and the electric apparatus
is shown by the lines in the diagram. At each station is a key, which
interrupts the electric circuit except when it is pressed down by the
operator. There are thus four different points at which contacts must be
simultaneously made before the circuit can be complete or a torpedo
explode. In the diagram three of these are represented as closed, and in
such a condition of affairs it only remains for the observer to depress
the handle of the key at station B to effect the explosion of torpedo
No. 2. The observer at station a is supposed to see the approaching
vessel in the line of torpedo No. 2, and recognizing this as an enemy’s
ship, he depresses the key at his station. The operator at B, by
following the course of the vessel with his telescope, will have brought
the pointer into contact with the wire leading to No. 2 torpedo, and he
then causes the explosion to take place by completing the circuit by
depressing his key. A modification of this plan is proposed by which the
position of the torpedoes is indicated by placing marks, such as
differently-coloured flags, or by night lamps with coloured glasses,
throwing their light only towards the telescopes. These marks are placed
in the line of direction of each torpedo from the telescope as at
_c_{1}_, _c_{2}_, _c_{3}_ and _b_{1}_, _b_{2 3}_; and if they can be put
at some distance, the position of the torpedo is determined with great
accuracy by the intersection of the lines of sight of the two
telescopes. Electric wires connect the stations and the torpedoes in the
same manner as we have before described. Such methods of firing
torpedoes are no doubt the most efficient, for the destructive charge
may be sunk so far below the surface that not a ripple or an eddy can
excite an enemy’s suspicion, or the channel appear otherwise than free
and unobstructed, while friendly ships may pass and repass without risk;
for the current which determines the explosion only passes when the two
sentinels complete the circuit by simultaneously depressing their keys.

Attempts have often been made to convert the torpedo into an offensive
weapon, by causing vessels containing explosive charges to drift by
currents, or otherwise, into contact with the enemy’s ships. The results
have been always unsatisfactory, as there is great uncertainty of the
machine coming into contact with its intended mark. Besides, it is easy
to defend vessels against such attacks by placing nets, &c., to
intercept the hostile visitors, especially if the attack is made by day,
and by night the chance that a torpedo drifting at random would strike
its object is very small indeed. One condition essential to the success
of such attacks is that the approach of the insidious antagonist may be
unobserved. Accordingly divers schemes have been projected for
propelling vessels wholly submerged beneath the surface of the water, so
that they may approach their object unperceived, and exert their
destructive effect precisely at that part of the vessel where damage is
most fatal, and where an ironclad vessel is most vulnerable, namely,
below the water-line. Vessels have been built, propelled by steam and so
contrived that their bodies are wholly submerged, only the funnel being
visible above the surface. These _quasi_ submarine ships carry small
crews, and are fitted with a long projecting spar in front, at the end
of which is carried the torpedo.

[Illustration:

  FIG. 109.—_Explosion of Whitehead’s Torpedo._
]

[Illustration:

  FIG. 110.—_Effect of the Explosion of Whitehead’s Torpedo._
]

The Federal navy sustained several disasters from torpedo-boats of this
kind. For example, the commander of the United States steamer
_Housatonic_ reported the loss of that vessel by a rebel torpedo off
Charleston on the evening of the 17th February, 1864, stating that about
8·45 p.m. the officer of the deck discovered something in the water
about 100 yards from, and moving towards, his ship. It had the
appearance of a plank moving in the water. It came directly towards the
ship, the time from when it was first seen till it was close alongside
being about two minutes; and hardly had it arrived close to the ship
before it exploded, and the ship began to sink. The torpedo-boat, with
its commander and crew, were lost, having, it is supposed, gone into the
hole made by the explosion, and sunk with the _Housatonic_. In general,
however, the performance of submarine boats has been unsatisfactory.
There is the difficulty of determining accurately the course of the
boat; there is great danger to the men manning it, as exemplified in the
case above; and there is again the problem of providing a means of
propulsion which shall enable such a boat to advance or retreat for,
say, a mile or more, without making its presence conspicuous by smoke or
otherwise. The latter condition would appear to exclude the use of steam
for such purposes, as the inevitable smoke and vapour would betray the
presence of the wily craft. Another power which has been proposed is air
strongly compressed, and recently a still more portable agent has been
suggested in solid carbonic acid, which is capable of exerting a
pressure of forty atmospheres by passing into the gaseous form. A
locomotive form of torpedo, invented by Mr. Whitehead, has the explosive
charge, which consists of about 18 lbs. of glyoxyline, placed in the
front part of a cigar-shaped vessel, the other part containing mechanism
for working a screw-propeller, by means of compressed air contained in a
suitable reservoir. This torpedo having been sunk a few feet below the
water, the motive power may be set in action by drawing a cord attached
to a detent, when the mechanical fish proceeds in a straight line under
the water. It is said that this torpedo is effective at 500 yards from
the ship attacked, and may even be made sufficiently powerful to travel
1,000 yards under the water. The great objection to such arrangements is
the uncertainty of the missile arriving at its destination, for even
supposing that the water were without currents, the least deviation from
the straight course would cause the torpedo to pass wide of the mark at
1,000 yards distant. It is said that at the experimental trials more
than one projector of such war engines has been startled by his machine,
after pursuing a circuitous submarine course, exploding in dangerous
proximity to the place whence it was sent off, the engineer narrowly
escaping being “hoist with his own petard.” The experiments which have
been made with Whitehead’s torpedo in smooth water appear, however, to
have been so far successful that we may probably hear of this invention
being put in practical operation in certain cases. Fig. 109 shows the
upthrow of water produced by the explosion of one of these torpedoes
against an old hulk. The large mass of water thus heaved up is a proof
of the mechanical energy of the explosion, and the effect on the hulk is
shown in Fig. 110, which exhibits the damage done to her timbers, from
the effects of which, it need hardly be said, she immediately sank. In
Fig. 112 we have the representation of the explosion of one of
Whitehead’s torpedoes containing 67 lbs. of gun-cotton, instead of the
glyoxyline. The accurate delineation of these pyramids of water could
not have been obtained but by the aid of instantaneous photography, and
it constitutes a good example of the great value of such an application
of that art, for the instantaneous photographs obtained in these
experiments enabled the engineers to calculate accurately the volume and
height of the column of water, which thus furnishes a measure of the
power of the explosion.

[Illustration:

  FIG. 111.—_Experiment made by the Royal Engineers with a Torpedo
    charged with 10 lbs. of Gun-Cotton._
]

The ordinary torpedo adopted by the British authorities for coast
defence consists of a cylinder of boiler plate, 4 ft. long and 3 ft. in
diameter. It is intended to contain 432 lbs. of loose gun-cotton,
equivalent in explosive energy to about a ton of gunpowder. The effect
of one of these torpedoes exploded 37 ft. beneath the surface of the
water is depicted in Fig. 113, and in Fig. 114 is shown the effect
produced when the same charge was exploded at the depth of 27 ft. below
the surface. Gun-cotton appears to be the most effective explosive for
torpedoes, if we may judge by the large volume of water heaved up, as
witness Fig. 111, which shows the result with a small torpedo,
containing only 10 lbs. of gun-cotton, exploded at a less depth than
those already mentioned. The ordinary torpedoes are moored by an anchor
attached to the torpedo, and floating above it is a buoy shaped like an
inverted cone. This cone contains a mechanical arrangement of such a
nature that when it is struck by a passing vessel, an electric circuit
is closed by bringing into contact two wires connecting the torpedo with
a voltaic battery on shore. While the apparatus may thus be at any
moment made fatal to a hostile vessel touching it, from the control it
is under by the engineer having the management of the battery contacts,
friendly vessels may pass over it with impunity.

[Illustration:

  FIG. 112.—_Explosion of Whitehead’s Torpedo, containing 67 lbs. of
    Gun-Cotton._
]

The employment of torpedoes develops, as a matter of course, a system of
defence against them. Nets spread across a channel will catch drifting
torpedoes, and stationary ones may be caused to explode harmlessly by
nets attached to spars pushed a great distance forward from the
advancing ship.

Before the final adoption of Whitehead’s torpedo, presently to be
described, the British Government had, after various official trials,
approved of a towing torpedo designed for offensive operations. It is
the invention of Commander Harvey, and is worthy of a detailed
description for the ingenuity of its construction.

[Illustration:

  FIG. 113.—_Explosion of 432 lbs. of Gun-Cotton in 37 feet of Water._
]

[Illustration:

  FIG. 114.—_Explosion of 432 lbs. of Gun-Cotton in 27 feet of Water._
]

The shape of Harvey’s torpedo, as may be noticed on reference to Fig.
118, is not symmetrical, but it has some remote resemblance to a boat,
though constructed with flat surfaces throughout. The outside case is
formed of wood well bound with iron, all the joints being made
thoroughly water-tight. The length is 5 ft. and the depth 1¾ ft., while
the breadth is only 6 in. Within this wooden case is another water-tight
case made of thick sheet copper, from the top of which two very short
wide tubes pass upwards to what we may term the deck of the wooden case.
These are the apertures through which the charge of gunpowder or other
explosive material is introduced; and when the tubes have been securely
stopped with corks, brass caps are screwed on. The centre of the
internal case is occupied by a copper tube, _g_, Fig. 115, which passes
the entire depth, and is soldered to the top and bottom of the copper
case, so that the interior of the tube has no communication with the
body of the torpedo, the principal charge merely surrounding it. Thus
the tube forms a small and quite independent chamber in the midst of the
large one, which latter is capable of containing 80 lbs. of gunpowder.
The copper tube or priming-case contains also a charge, _a_, which when
exploded bursts the tube, and thus fires the torpedo in its centre. The
priming charge is put in from the lower end of the tube, which is
afterwards closed by a cork and brass cap, _h_; for the centre of the
priming-case is occupied by a brass tube, _b_, closed at the bottom, but
having within a pointed steel pin projecting upwards. In this tube works
the exploding bolt _c d_, which requires a pressure of 30 or 40 lbs. to
force it down upon the steel pin. This pressure is communicated to the
bolt by the straight lever working in the slot at its head, _d_, and
itself acted on at its extremity by the curved lever to which it is
attached. Thus from the mechanical advantage at which the levers act a
moderate downward pressure suffices to force the exploding bolt to the
bottom of the brass tube. The lower end of this bolt has a cavity
containing an exploding composition sufficient in itself to fire the
torpedo, even independently of the priming charge contained in the
copper tube. This composition is safely retained in the end of the bolt
by a metallic capsule, _c_, which, when the bolt is forced down, is
pierced through by the steel pin at the bottom of the brass tube, and
then the explosion takes place. The bolts are not liable to explosion by
concussion or exposure to moderate heat, and they can be kept for an
indefinite period without deterioration.

[Illustration:

  FIG. 115.—_Section of Priming-Case and Exploding Bolt._
]

The mode of producing the explosion is not stated: it consists probably
of an arrangement for bringing chemicals into contact. Besides the two
levers already mentioned, a shorter curved lever working horizontally
will be noticed. The object of this is to make a lateral pressure also
effective in forcing down the bolt—a result accomplished by attaching to
the short arm of the lever a greased cord, which, after passing
horizontally through a fairleader, runs through an eye (see Fig. 117) in
the straight lever, and has its extremity fastened so that a horizontal
movement of the short lever draws the other down. A very important part
of the apparatus is the safety key, _f_, Fig. 115, a wedge which passes
through a slot in the exploding bolt, and resting on the brass-work of
the priming-case, retains the muzzle 1 in. above the pin. Through the
eye of the safety key and round the bolts passes a piece of packthread,
_e_, which being knotted is strong enough to keep the key securely in
its place, but weak enough to yield when the strain is put on the line,
_d´_, used for withdrawing the safety key at the proper moment. This
line is attached to the eye of the key, and passes through one of the
handles forming the termination of the iron straps. As represented in
Fig. 117, it forms the centre one of the three coils of rope. The bottom
of the torpedo is ballasted with an iron plate, to which several
thicknesses of sheet lead can be screwed on as occasion requires. Fig.
117 shows the arrangement of the slings by which the torpedo is attached
to the tow-rope, and it will be seen that another rope passes backwards
through an eye in the stern to the spindle-shaped object behind the
torpedo. This is a buoy, of which two at least are always used, although
only one is represented in the figure. Each buoy, in length 4½ ft., is
made of solid layers of cork built up on an iron tube running through it
lengthways, so that the buoys admit of being strung upon the rope.

[Illustration:

  FIG. 116.—_Harvey’s Torpedo._
]

Having thus described the construction of the torpedo, we proceed to
explain how it is used. It must be understood that if the torpedo and
its attached buoys are left stationary in the water, the tow-rope being
quite slack, the torpedo will, from its own weight, sink several feet
below the surface. But when they are _towed_, the strain upon the
tow-line brings the torpedo to the surface, to dip below it again as
often as the tow-line is slackened. There is another peculiarity in the
behaviour of the torpedo, and that is that, when towed, it does not
follow in the wake of the vessel, but diverges from the ship’s track to
the extent of 45°. Its shape and the mode in which it is attached to the
tow-line are designed so as to obtain this divergence. But, according as
the torpedo is required to diverge to the right or to the left, there
must be the corresponding shape and arrangement of tow-line and levers;
hence two forms of torpedo are required, the starboard and the port. The
figures represent the port torpedo, or that which is launched from the
left side of the torpedo-ship, and diverges to the left of its course.
The efficiency of the torpedo depends upon the readiness and certainty
with which it can be brought into contact with the hostile ship, and
this is accomplished by duly arranging the course of the torpedo vessel,
and by skilfully regulating the tow-line so as to obtain the requisite
amount of divergence, and to cause the torpedo to strike at the proper
depth. The tow-rope is wound on a reel, furnished with a powerful brake,
the action of which will be readily understood by inspection of Fig.
116, which represents also a similar smaller reel for the line attached
to the safety key. Leather straps, sprinkled with rosin to increase the
friction, encircle the drums of the reels, and can be made to embrace
them tightly by means of levers, so that the running out of the lines
can be checked as quickly as may be desired. Handles are attached to the
straps, so that they can be lifted off the drum when the line is being
drawn in by working the handles. When the torpedo is ready for action
and has been launched, a suitable length of tow-line, which is marked
with knots every ten fathoms, is allowed to run off its reel, while the
safety key-line is at the same time run off the small reel, care being
taken to avoid fouling or such strains on the line as would prematurely
withdraw the key. Fig. 106 will make clear the mode of controlling the
lines, but it is not intended to represent the actual disposition in
practice, where the men and the brakes would be placed under cover. On
the left of the figure a starboard torpedo is about to be launched; on
the right a port torpedo has been drawn under the ironclad and is in the
act of exploding, the safety key having been withdrawn by winding in its
line when the torpedo came into proximity to the attacked vessel.

[Illustration:

  FIG. 117.—_Harvey’s Torpedo._
]

[Illustration:

  FIG. 118.—_Harvey’s Torpedo._
]

[Illustration:

  FIG. 119.—_Official Trial of “Harvey’s Sea Torpedo,” February, 1870._
]

When the torpedo has been launched over the vessel’s side, the latter
being in motion, the torpedo immediately diverges clear of the ship; and
when the buoys have also reached the water, the men working the reels
pay out the line steadily, occasionally checking the torpedo to keep it
near the surface, but avoiding a sudden strain upon the slacked
tow-rope, which would cause the torpedo to dive, and in shallow water
this might lead to the injury or loss of the torpedo. The torpedo can be
gradually veered out to the distance required, at the same time that the
safety-key is so managed that sufficient strain may be put upon it to
prevent it from forming a long bight astern of the torpedo, but avoiding
such a strain as would break the yarn holding the safety-key in its
place. The distance to which the tow-line may be paid will depend upon
the circumstances of the attack. More than 50 fathoms is, however, a
disadvantage, as the long bight of tow-lines makes the torpedo drag
astern. The torpedo can always be made to dive several feet below the
surface by suddenly letting out two or three fathoms of tow-line. The
torpedo vessel should, of course, be a steamer of considerable
speed—able to outstrip when necessary all her antagonists, and, as a
rule, it is found best to make the attack at night. Let us imagine two
ships of war at anchor, and parallel to each other at perhaps a distance
of 60 fathoms; and suppose that, under cover of darkness, a hostile
torpedo vessel boldly steams up between them, having launched both its
starboard and port torpedoes. In such a case neither ship could fire at
the torpedo vessel for fear of injuring the other, while the torpedo
vessel would in all probability succeed in bringing its floating mines
into contact with both its enemies.

[Illustration:

  FIG. 120.—_Model of Submarine Guns._
]

Another device for submarine attacks upon vessels on which much
ingenuity has been expended is the submarine gun. It has been sought to
propel missiles beneath the surface of the water, these missiles being
usually provided with a charge which, on contact with the vessel’s side,
would explode, and by making a hole below the water-line, cause the
certain destruction of the ship. It is obvious that such a mode of
attack would reach the only vulnerable parts of a thickly-plated
ironclad, and therefore the project has been recently revived in several
forms. Fig. 120 is taken from the photograph of a model of an invention
of this kind. The guns which are to propel the submarine projectiles,
have port-holes formed by valves in such a manner that the gun when
loaded can be run out without allowing water to enter; it can then be
fired while the muzzle is below the surface, and again drawn in without
the port being at any time so opened that water can pour into the
vessel. All contrivances of this kind have hitherto been failures;
indeed, it does not appear possible that they could succeed, except at
very close quarters, for the resistance offered by water to a body
moving rapidly in it is extremely great, and, as we have already had
occasion to state, the resistance increases as the square of the
velocity, and probably in even a higher degree for very great
velocities. Any one who will remember the effort it requires to move
one’s hand quickly backwards and forwards through water will easily
understand that the resistance it presents would, in a comparatively
short space, check the speed of a projectile, however great that speed
might be at first. A good many years ago Mr. Warner produced a great
sensation by an invention which appears to have been essentially a
floating torpedo. The cut below, Fig. 121, represents the result of an
experiment publicly made by him off Brighton, in 1844, upon a barque,
which was towed out by a steamer to a distance of a mile and a half from
the shore. Mr. Warner was on board the steamer, and the barque was 300
yards astern. Five minutes after a signal had been made from the shore,
the torpedo was caused to explode, striking the barque amidships,
throwing up a large column of water and _débris_, shooting the mainmast
clean out of the vessel, the mizen going by the board, and dividing the
hull into two parts, so that she sank immediately. Yet this invention,
though apparently so successful, does not seem to have ever been put in
practice.

[Illustration:

  FIG. 121.—_The Warner Experiment off Brighton._
]

The stationary torpedoes of the kind mostly used in the American Civil
War were, as already stated, _self-acting_; that is, they exploded when
touched by a passing vessel. They would now be more generally called
_self-acting mines_, and are to be distinguished from that form of the
weapon in which the explosion is determined by some manipulation on
shore, such as the closing of an electric circuit, when the hostile
vessel comes within the area of destructive action. This form receives
the name of _observation mines_. Stationary mines are essentially
instruments of defence, and as such are employed for the protection of
rivers and harbours. The self-acting varieties usually contain a charge
of 70 lbs. to 80 lbs. of gun-cotton, and are commonly arranged in lines.
Of course, when the occasion for which such mines have been laid down is
past, they must be removed, and the operation of picking them up is one
of great danger. The observation mines, on the other hand, do not
require immediate removal, and they can be taken up with little risk. In
the British service the observation mine contains about 500 lbs. of
gun-cotton, and a line of these is sometimes moored in a water-way, from
35 feet to 50 feet below the surface. The area of destructive action in
this case is a circle of about 30 feet radius, and therefore a line of
seven such mines laid across a channel at intervals of 120 feet apart
would ensure the almost certain destruction of any war vessel of
ordinary breadth that might attempt to pass up a river of 840 feet in
width. This is about the distance across the Thames near the Tower of
London, but the depth of the river there being only 12 feet at low-water
and 33 feet at high-water, would not suffice to give effect to the full
energy of so large a charge of gun-cotton; for it has been found that,
for a given charge, there is a certain depth under water at which its
explosion will produce the maximum effect, and this depth will be
greater with heavier charges than with light ones. The regulation
“observation mine” of the British service has a cylindrical case of
stout plate-iron, 32 inches in diameter and 34 inches high, with domed
ends. Within this gun-cotton is contained, in a wet condition, in a
number of copper envelopes, which have holes for access of water to wet
the charge from time to time as occasion requires, the wet condition
being the safest for the carriage of gun-cotton. The centre of the case
is a tin charged with some discs of dry gun-cotton, and the detonator
required to bring about the explosion of the whole charge when the
electrical contact is made, fires the fuze contained within the primer.
These cases are arranged to have a certain buoyancy, and are moored with
wire ropes to heavy iron sinkers, the mooring ropes being of such length
as to keep the explosive case at the proper depth below the surface, and
of sufficient strength to resist the force of the currents in the
waterway. There is also another type of submarine mine, operated by an
electric current, the circuit of which is closed by contact of a passing
vessel, if at the time a battery on shore is included in the circuit. In
this way the mines can be made harmless or dangerous for passing vessels
at the will of the operator on shore. The passing vessel is made to
complete the circuit by tilting over the cylindrical case so far that
some mercury contained in a small part of it is upset, and makes the
requisite metallic contact. This arrangement is known as the
_electro-contact_ mine.

In former pages of this article on torpedoes will be found
representations of the effects produced by _Whitehead’s torpedo_, which,
being automobile and travelling altogether under the surface of the
water, was capable of being made a very formidable weapon of offence.
When the earlier editions of this work were going through the press, it
was understood that the Whitehead torpedo left much to be desired as
regards speed, certainty of direction through the water, and perhaps in
other points, the inventor being constantly engaged in effecting
improvements. At that time particular pains were taken to keep secret
the nature of the most important parts of the internal mechanism. The
work of construction was carried on in a room with locked doors,
blocked-out windows, and a military guard outside. The earlier
experimental forms of this automobile torpedo were constructed in
complete secrecy by the inventor himself, with the help of only one
trusted, skilled mechanic and a boy, who was no other than Mr.
Whitehead’s own son. The history of the invention is very interesting,
and exemplifies the power of skill and perseverance to overcome a
multitude of difficulties, the result being a machine which is simply a
marvel of ingenuity and of delicate nicety of adaptation.

The first notion of the automobile torpedo appears to have occurred to
an Austrian naval officer; but it took rather the form of a small vessel
containing within itself some propelling power by which it could move
along the surface of the water, its course being directed by ropes or
guiding lines from the shore or from a ship. The fore part of the little
vessel was to hold an explosive, to be fired automatically by the
self-propelled torpedo coming into contact with the side of the hostile
vessel. The propelling power, as first suggested, was clockwork, if that
could be made efficient, or steam as an alternative. The Austrian
authorities, however, considered that it would be impracticable to
direct the course of the torpedo in the manner proposed, and that there
were also great objections to each of the methods of obtaining motive
power. The assistance of a thoroughly competent and skilful mechanician
was then sought, and Mr. Whitehead, at that time the director of an
engineering establishment at Fiume, devoted himself to solving the
problem of devising a torpedo which should be able to travel beneath the
surface of the water, and, when once started, should require no external
guidance to keep it on its proper course. After some years of
experimental labours, Mr. Whitehead produced the first form of the
weapon with which his name is associated, but to this he has since added
from time to time many ingenious improvements. A committee of experts
having been appointed by the Austrian Government to test the
capabilities of the new invention, it was made the subject of a long
series of trials, after which the committee recommended its immediate
adoption in the Austrian navy. The earlier form of the Whitehead torpedo
had, however, the defect already mentioned, of being sometimes very
erratic in its course; its speed was small (6 knots) compared with that
of the more recent patterns (30 knots), and its range of travel
proportionately less. The British Admiralty having invited Mr. Whitehead
to visit England with some specimens of his invention, a committee was
appointed to make complete trials of the capabilities of two weapons he
had brought with him. Although by this time great improvements had been
made on the original design, and in particular, Mr. Whitehead had almost
completely overcome the difficulty of keeping the torpedo at a uniform
depth during its course, by means of delicate adjustments in what we may
call the steering chamber (to be presently mentioned), much remained to
be accomplished before the weapon attained the perfection of the modern
patterns. Indeed, the inventor may be said to have from time to time
redesigned his contrivances, as when in 1876 the speed was increased to
18 knots, and again in 1884 more powerful engines brought up the speed
to 24 knots. Further improvements have been made by Mr. Whitehead, who
designed a new form of the weapon in 1889, and some of the more recent
patterns can now show a speed of 30 knots or more. The committee
appointed by the Admiralty to conduct experiments with the first pair of
torpedoes brought to England, after having tested them in various ways
for a period extending over six months, reported that they believed that
“any maritime nation failing to provide itself with submarine locomotive
torpedoes, would be neglecting a great source of power, both for offence
and defence.” Upon this recommendation the Admiralty immediately
purchased from Mr. Whitehead for £15,000 the secret of the internal
mechanism of his invention and the rights of manufacturing it. The
self-adjusting apparatus within the steering chamber, by means of which
the torpedo was kept at its due depth, was then a jealously-guarded
secret; but when the arrangement with Mr. Whitehead was effected, the
Government immediately set about the manufacture of these torpedoes on a
large scale. The artificers employed in making the Whitehead torpedoes
were now numerous, and the internal structure of these weapons could not
advantageously be altogether concealed from those who had to handle them
on board of the ships, so that it inevitably happened that some details
of their construction leaked out, and came into the possession of other
powers, whereupon all the maritime states followed the example of Great
Britain by providing their navies with Whitehead or some such form of
locomotive torpedo. It is no part of our plan to enter into the
mechanical _minutiæ_ of the Whitehead torpedo. We may, however, give the
reader such an idea of the external appearance and internal arrangement
of the Whitehead torpedo as will enable him to appreciate to some extent
the ingenuity and skill that have been brought to bear upon its
construction.

There are in existence many different patterns of the
weapon—twenty-four, it is said—and this is what might be expected from
the fact of its being produced at several different manufactories, each
striving to effect whatever improvements its resources will supply. Some
torpedoes have been made at Fiume, very many at Mr. Whitehead’s works at
Portland, as also at the Government establishment at Woolwich, while
private enterprise in this direction is encouraged by contracts with
some private firms, such as that of Messrs. Greenwood & Bately at Leeds.
The greatest diameter of the large torpedo is 18 inches, but in some it
is rather more, in others 14 inches or 16 inches; and the length may
vary between 14 feet and 19 feet. Many of our Whitehead torpedoes are
made of polished steel, but in the later patterns phosphor-bronze is
partly made use of, as being not liable to corrode. The interior of the
torpedo is divided by transverse partitions into five distinct
compartments. The foremost of these, called the “head,” contains the
explosive charge when the weapon is ready for use in actual warfare.
This section, which may occupy about one-sixth of the total length, is
an air-tight case made of phosphor-bronze, one-sixteenth of an inch
thick, and it is kept permanently charged with slabs of wet gun-cotton,
which may amount to 200 pounds weight in all, and is ready to be
attached by a screw and bayonet joint to the body of the torpedo; but
this is done only at the time immediately before it is required for its
destructive employment. Its place at other times, as when the torpedo is
used for drill practice, and to test its running powers, is occupied by
a dummy head of steel, of exactly the same shape and size, and packed
with wood in such a manner that its weight and centre of gravity are
like those of the explosive head when the latter is ready for action.
The wet gun-cotton requires a _detonative_ explosive of dry material
close to it, in order to determine its own detonation. The explosive
heads of the Whitehead are not fitted with the pistol and priming tube
until all is ready for the discharge of the weapon, as this would render
the handling of the torpedo highly dangerous. This priming apparatus is
merely a metallic tube that slips into a corresponding hollow in the
explosive head so far as to reach well within the wet gun-cotton charge,
although still separated from the latter by a metal casing. The
posterior extremity of the priming tube contains a few ounces of dry
gun-cotton, and just in front of this is a copper cap containing some
fulminate of mercury, which readily explodes when struck by the point of
a steel rod, occupying the centre of the tube and projecting a short
distance out at the “nose” of the torpedo, so as to be driven inwards by
the impact of the latter on a ship’s side. The explosion of the
fulminate causes the detonation of the dry gun-cotton at the bottom of
the priming tube, and this is taken up by the whole mass of the
explosive with destructive effect. The danger of premature or accidental
explosion by anything coming in contact with the projecting striker is
obviated by several checks which prevent any chance blow driving the rod
home against the fulminate charge. The anterior projecting end of the
rod has a screw thread worked upon it, and on this turns freely a nut
provided with wings like a small fan, revolving in such a manner that as
the torpedo is moved through the water, the nut is spun off, and the
striker is free to be driven back, except in so far as it is still
retained by a small copper pin, the breaking of which requires a
considerable blow. Again, the little fan above mentioned cannot begin to
spin off the rod until another pin or wedge has been withdrawn, which
operation is performed just before launching the weapon.

Immediately behind the exploding head of the torpedo is the air-chamber,
which occupies a considerable space in the length, _i.e._, about
one-third of the whole. This part is made of the toughest steel, nearly
⅓ of an inch thick, and contains the power actuating the motor, in the
form of air forced into it by powerful pumps on board the ship, until
the pressure reaches the enormous amount of 1,300 lbs. or more on the
square inch, or, at least, this is what is made use of in the newer
patterns when charged for action. In the largest size of the weapon the
weight of air injected may be more than 60 lbs., and, of course,
considerably detracts from the buoyancy of this part.

Behind the air-chamber comes another much shorter compartment we have
called the “steering chamber,” in which are contained the most ingenious
and delicate parts of the apparatus, namely, the mechanism by which this
extraordinary artificial fish adjusts itself, after the manner of a
living thing, to the required conditions. Among other contrivances, it
contains several valves controlling the action of the compressed air on
the engines, etc. The enormous pressure to which the air-chamber is
charged, if allowed to act unchecked, would give at first a power almost
sufficient to shatter the machinery, and, in order to prevent this, a
“reducing valve” is interposed so that only a moderate and uniform
pressure of air is allowed to act upon the engines. Then there is the
“starting valve” by which the air is admitted or cut off from the
engines, and still another valve which is contrived to delay the action
of the compressed air for the short interval during which the torpedo is
passing from the discharging tube until it enters the water. For during
this interval the propellers not having to act against the water, but
only against the resistance of the atmosphere, would be whirled round at
an enormous speed, and the machinery would sustain such shocks and
strains as might endanger the whole apparatus. It is to prevent this
that the “delay action valve” is provided.

The automatic apparatus by which the torpedo’s course is regulated is a
very remarkable part of the invention, and it admits of the nicest
adjustments. This was the crown of Mr. Whitehead’s ingenuity, but the
details were, by an arrangement between the government and the inventor,
not to be made public, though necessarily communicated to certain
officers in the service, and known to the chief artisans employed in
their fabrication. These persons are all, we believe, required to give
pledges not to divulge the arrangement of particular parts. But such
details could scarcely be made intelligible, even should they be
interesting, to the general reader. The principles upon which the
controlling apparatus are arranged may, however, be comprehended without
difficulty.

The tail of the torpedo is provided with two rudders, one in its central
vertical plane, and the other in its central horizontal plane. Their
action in directing the torpedo’s course is exactly that which the tail
supplies to a fish, or the rudder to a boat. Suppose that while the
torpedo is passing through the water the vertical rudder is by any means
turned towards one side, the course of the metallic fish will be
diverted towards that side; or again, a turning upwards of the
horizontal rudder would have the effect of directing the nose towards
the surface, and would make the torpedo rise, and so on. Now the
positions of the horizontal rudder are regulated from the “steering
chamber,” in which a heavy weight is suspended like a pendulum, so as to
be capable of swinging fore and aft. This pendulous weight actuates the
horizontal rudder through a system of rods and levers, so that when it
hangs vertically the horizontal rudder is level, but if from any cause
the nose of the torpedo were directed downwards, the pendulous weight
would come to a more forward position in the steering chamber, and would
raise the rudder, and thus turn the nose towards the surface until the
original horizontal position were regained. In the contrary case, of
course, the reverse action would take place. But the torpedo, while
preserving a horizontal position, might tend to sink to too great a
depth, or rise too near the surface, and this is prevented by another
adjustment, namely, a piston receiving the pressure of the water, which,
on the other side, is opposed by a spring. If the torpedo sinks a little
the pressure increases, the piston, which moves with perfect freedom
without allowing water to pass in, is forced inwards, and its movement
is communicated to the same levers that connect the pendulous weight
with the horizontal rudder, the latter is raised, and then the nose of
the torpedo is directed upwards, and it consequently approaches the
surface again. In the contrary case the spring, relieved from some of
the external pressure, operates the levers in the other direction.

The compartment immediately behind the “steering chamber” contains the
engines which are of the Brotherhood type, provided with _three_ single
acting cylinders. The three-fold throw prevents any possibility of the
engine getting on a “dead point.” Though this compartment is the
shortest in the torpedo, the engines in the larger sizes are capable of
indicating as much as thirty horse power. It has for simplicity been
stated above that the pendulous weight and the balanced piston act by
means of rods on the horizontal rudder; this was so in the early
patterns of the torpedo, but it was soon found that they did not do so
with sufficient steadiness and promptitude, and the force they could
apply was in the larger and swifter forms quite ineffective. Nowadays
the engine compartment always contains a little piece of apparatus which
is an arrangement of cylinder and piston, upon which the compressed air
acts in one or the other direction according to the way its slide-valve
is moved. It is this slide-valve that the rods from the “steering
chamber” move, and allow the force of the compressed air to turn the
rudder up or down. This auxiliary apparatus has the same relation to the
torpedo rudder that the steam-steering apparatus of a large vessel has
to its rudder. Although it is only about a few inches long, its power
and delicacy are such that the pressure of half an ounce on its slide
admits to its piston a force equal to 160 lbs., and its introduction has
given the torpedo the power of steadily steering itself.

Behind the engine compartment, but completely shut off from it, is
another almost empty division occupying a considerable part of the
length of the torpedo, and known as the “buoyancy chamber.” But it
contains, attached to the bottom of it, a certain amount of ballasting,
so adjusted to balance the weights of the other parts that the whole
floats horizontally, and at the same time preserving the tube in one
vertical position as regards its transverse diameter, _i.e._, so that
the horizontal rudder is always horizontal. The shaft from the engine
passes through this compartment, as also the rod from the small motor
that moves the horizontal rudder. These, of course, pass through
water-tight bearings.

At the tail of the torpedo, behind the rudders, are _two_ three-bladed
screw propellers, of which the anterior one is mounted on a tubular
shaft having a common axis with the other, but made to revolve in the
opposite direction by means of a bevel wheel mounted on each independent
shaft, with a third such wheel connecting them. The object of the double
screw is to obviate “slip,” that is, ineffective motion of the blades
through the water, and by this means the full power of the engines can
be developed; while any tendency to _deviation_ to right or left, due to
the rotation, is reduced to a minimum. We have spoken of one horizontal
and one vertical rudder, although externally there appear to be two of
each kind, right and left, above and below, on the tail of the torpedo.
These pairs, however, are so connected as to be always in the same
respective planes. The controlling mechanism acting in two different
ways on the horizontal rudder has been already indicated, but nothing
has yet been said about the vertical rudder. It is not moveable by
anything within the torpedo, but is commonly fixed by clamping screws in
or about the same vertical plane as the axis of the torpedo, and it
performs the same function as a kind of back fin, which, in the earlier
forms, extended nearly the whole length of the tube; and that is
obviating any tendency of the torpedo to roll about its axis. The
vertical rudder can also be fixed at a considerable inclination to the
axis should occasion require, and the effect of that would be to cause
the torpedo to pursue a circular course of greater or less radius,
according to the less or greater degree of inclination. Very rarely,
however, would this be required, and the vertical rudder may be
considered as fixed in the axial plane, or having such slight
inclination as may, on trial, have been found necessary to counteract
any tendency to lateral deviation.

There are several different methods for discharging the Whitehead
torpedoes from ships. They may be sent from a tube below the water-line,
but the arrangements for that purpose are complicated and difficult to
manage, while, on the other hand, the launch of the weapon is not
perceived by the enemy, and it is at the same time out of the reach of
any blow from a hostile missile while yet in its discharging tube. More
commonly the discharging tube is arranged above the water-level. On
regular torpedo boats, the tubes are sometimes mounted on pairs upon a
revolving table, provided with many nice adjustments, and even the
single above-water torpedo tube, as used between decks, is an apparatus
having somewhat complicated appliances. The torpedo is expelled from the
tube now preferably by a small charge of _cordite_. But in the Royal
Navy no fewer than some twenty different patterns of torpedo tubes have
been in use for the various sizes of torpedoes. In some of these,
compressed air, in others gunpowder or _cordite_, in others, again,
mechanical impulse propels the torpedo into its element. It would
obviously be impossible within our limits to enter into details of these
various constructions, or to attempt descriptions of _all_ the ingenious
contrivances applied to the torpedo itself, or to give an account of the
means of defence against mines and torpedoes, this last being a matter
belonging to naval tactics. The adoption of the torpedo as a naval
weapon has given rise to special types of boats adapted for its
employment, and these again have required other boats to destroy them
(“torpedo-boat destroyers” or “catchers”). Light draught and high speed
were desired in these last; but in many cases the intended speed was
inferior to that of the torpedo boats that were to be caught.

The following particulars about the British torpedo-boat destroyer
_Daring_ may be compared with those given of the cruiser _Majestic_. The
_Daring_ is 185 feet long, 7 broad, and she draws only 7 feet of water.
Her speed is about 28½ knots per hour, with a steam pressure in the
boilers of 200 lbs. per square inch, and an air pressure in the
stoke-holds equivalent to 3 inches of water (forced draught.)

The importance attached to the prospective use in war of the automobile
torpedo may be shown by the fact that at the end of 1890 the number of
torpedo boats built or laid down for England was 206, and for France
210, while other nations followed with numbers proportionate to their
means. Forty “torpedo-boat destroyers” were in building for the British
Navy towards the close of the year 1896, and now (March, 1897) it is
announced that the number of torpedo boats and torpedo-boat destroyers
in the French Navy is to be increased by 175.

[Illustration]

[Illustration:

  FIG. 122.—_M. Ferdinand de Lesseps._
]



                              SHIP CANALS.


Artificial canals are amongst the oldest of inventions, for, centuries
ago, they have been constructed, even of very large dimensions, in
various parts of the world. There is in China, for instance, a great
canal, 900 miles in length and 200 feet broad, which is supposed to have
been made 800 years ago. The advantages of canals did not escape the
attention of the Egyptians, Greeks and Romans. We read of very early
attempts to cut through isthmuses, in order to form a water
communication between regions where other carriage would be long and
difficult. It appears to be admitted that canals connecting the Red Sea
with the Mediterranean existed some centuries before the Christian era,
and to cut the Isthmus of Corinth by a waterway was a cherished project
with several Roman Emperors, and now it appears that in this nineteenth
century this project will shortly be realized. But as the canal-lock is
but a comparatively modern invention, dating only from the fourteenth
century, and first used in Holland, all the canals anterior to that
period had to be designed as level cuts, a restriction which greatly
increased the difficulties of the problem. Canals were in use in various
parts of Europe, particularly in Holland and France, long before any
were constructed in England, as, for example, the Languedoc Canal,
which, by a cut of 150 miles, connects the Bay of Biscay with the
Mediterranean. It is 60 feet broad, and attains, at its highest level,
an elevation of 600 feet above the sea. The canal system in England was
first introduced in the middle of the eighteenth century, and soon
afterwards, the Duke of Bridgewater engaged the famous Brindley to
construct a canal, connecting his collieries at Worsley with Manchester,
about seven miles distant, and afterwards extended his scheme, so as to
open up a more direct water communication between Manchester and
Liverpool. Before the making of this canal, the cost of the carriage of
goods between these towns had been forty shillings per ton by land, and
twelve shillings by water. After that, they were conveyed with
regularity for six shillings per ton. The system was soon extended, so
as to connect the Trent with the Mersey, and the boldness of both the
projectors and their engineer in carrying out this scheme is memorable
in the history of such undertakings. Brindley was equal to the task of
coping with the difficulty of carrying his canal over what had hitherto
been supposed an insuperable obstacle, for he pierced Harecastle Hill
with a tunnel more than a mile and a half in length—a then unheard of
piece of engineering—to say nothing of several shorter tunnels, many
aqueducts, and scores of locks. The Duke of Bridgewater, who at one
period had been unable to raise £500 on his own bond for the prosecution
of his scheme, died in 1803, in receipt of a princely income from the
profits of his useful undertaking. For its creation, he had, however,
denied himself the present enjoyments of his patrimonial revenue, by
reducing his expenses at one period to the modest sum of £400 per annum.
Before his death, the Duke, for taxation purposes, estimated his income
at £110,000 per annum. Before the railway system was fully established a
network of canals had united the most populous places in England, the
total length of the waterways being not much less than two thousand
miles. With the rise of railways the importance of canals as channels
for the conveyance of merchandise declined. But, nevertheless, in
consequence of the continued increase of traffic and the great cheapness
with which goods can be carried by water, canals are often able to
compete with railways in the carriage of bulky or heavy goods when speed
of transit is not an object. The English canals have, therefore, never
been disused or abandoned, notwithstanding the ubiquitous ramifications
of the railway lines. Nay, the value of the Bridgewater Canal system,
about to be superseded so far as concerns the communication between
Liverpool and Manchester by the greater scheme we have presently to
describe, is such that £1,710,000 is now required for its purchase; and
that is the value in spite of four lines of railway connecting those
great towns, and all competing for the carriage of goods. In these
canals, designed for inland communication only, the navigation is
confined to boats or barges of very insignificant dimensions compared
with the sea-going ships that some great modern canals are constructed
to receive.

To the present century belongs the famous “Caledonian Canal,” as the
waterway is often called that extends in a straight line for more than
60 miles across Scotland, in north-east and south-west directions. The
canal work here was commenced in 1802, under the direction of Telford,
and though it was opened for traffic in 1822, the work as it now exists
was not completed until 1847. But the length of the actual canal
construction in this case did not much exceed 23 miles, for a natural
waterway, navigable for ships of any burden, is formed by the series of
narrow lakes that fill what is called the “Great Glen of the Highlands.”
This glen has many of the characteristics of a great artificial ditch:
its highest point is only 90 feet above the tide level in Loch Linnhe; a
circumstance not a little remarkable in so mountainous a country. What
is also remarkable is the great depth of these lakes, which in some
places exceeds 900 feet. The banks also are generally very steep, and
indeed at one time it was impracticable to pass along the shores of Loch
Ness, the longest of the lakes. But there are now good roads along both
banks. Although the ground traversed by the artificial channels of the
Caledonian Canal is chiefly alluvial, the cost of the undertaking proved
to be great, amounting, it is said, to about one and a quarter million
pounds sterling. Indeed, had it not been for the introduction of steam
navigation before the completion of the work, and the consequent
increase and facility of water conveyance, it is doubtful whether the
utility of this canal would have been commensurate with its cost, or its
receipts have made any profit for its promoters. By the Caledonian Canal
large steamers and other vessels may pass from sea to sea, and in the
summer time the steamers that traverse it are crowded with tourists
attracted by the magnificent scenery it presents throughout the greater
part of its length.

But whatever had previously been done in canal construction was
surpassed in enterprise and importance by Lesseps’ great work in Egypt.


                           _THE SUEZ CANAL._

As we have already seen, the idea of opening a waterway between the Red
Sea and the Mediterranean is by no means a product of the present
century. The ancient Egyptians do not appear to have cut directly
through the Isthmus, but Herodotus describes a canal made by Necho about
the year 600 B.C., from Suez through the Bitter Lakes to Lake Timsah and
then westward to Bubastis on the Nile. He mentions certain water gates,
and states that vessels took four days in sailing through. This canal
became silted up with sand ages ago, but it was cleared out again and
re-opened in the seventh century of our era by the Caliph Omar, and
traces of it are still visible. According to some recent discoveries in
the chief archives of Venice, as early as the end of the fifteenth
century, when Vasco da Gama had discovered the Cape of Good Hope, and
the Portuguese took that new route to India, hitherto the exclusive
property of the Venetian and Genoese merchants, a re-cutting of the
Isthmus of Suez was thought of. Plans were prepared and embassies sent
to Egypt for paving the way for the accomplishment of this great
enterprise, which, it is said, was only foiled by the persistent
opposition of some patricians, who were probably bribed by foreign gold
to prevent the execution of the plan. One of our Elizabethan poets,
Christopher Marlowe, appears, in the following lines, to have
anticipated M. de Lesseps:—

            “Thence marched I into Egypt and Arabia,
            And here, not far from Alexandria,
            Whereat the Terrene and the Red Sea meet,
            Being distant less than full a hundred leagues.
            I meant to cut a channel to them both,
            That men might quickly sail to India.”

For at that period travellers going to India in the famous sailing
ships, called “East Indiamen,” were obliged to sail round the Cape of
Good Hope and pass from the Southern to the Indian Ocean. The reader who
wishes to understand the importance of the Suez Canal should look at the
map of the Eastern Hemisphere, where he will have no difficulty in
finding the position of the vast continent of Africa, which is washed on
the north by the Mediterranean Sea, on the west by the Atlantic, on the
south by the Southern Ocean, and on the east and north-east by the
Indian Ocean and the Red Sea. If he now traces the waterway round
Africa, on coming to the head of the Red Sea he will find the only
interruption of the oceanic continuity in the narrow neck of land called
the Isthmus of Suez. But for this, ships might long ago have made
complete circuits round this vast, and, even as yet, but partially
explored continent. The circuit would, indeed, be a great one of some
15,000 miles; but the barrier that the Isthmus presented to
inter-oceanic communication between the eastern and the western worlds
was a piece of physical geography which has undoubtedly been a most
important factor in determining the course of history. It has been said
that had there existed at Suez a strait like that of Gibraltar or that
of Messina, instead of a sandy isthmus, the achievements of Diaz, Vasco
da Gama, and Columbus would have lost much of their significance; but
the advantages to the world’s commerce would have been incalculable, and
the progress of the race might have been more rapid.

The Emperor Napoleon I. had the idea of restoring the old canal; but it
was only when steam navigation had taken its place on the seas that the
scheme was looked upon as offering any chance of financial success. But
General Chesney, who made some surveys for the French Government in
1830, had come to the conclusion that there was a considerable
difference of level between the two seas—a difference, he calculated, of
about 30 feet. The existence of such a state of things would, of course,
have been very unfavourable for the undertaking; but the General’s
supposition was soon proved to have been erroneous.

The suggestion of carrying out the project of constructing a ship canal
through the Isthmus was seriously revived by Père Enfantin, the St.
Simonian, in the year 1833. He then induced M. Ferdinand Lesseps, the
French vice-consul, and Mehemet Ali, the Pasha of Egypt, to take some
practical measures towards its accomplishment. Surveys were made, but
owing to the breaking out of a plague, and to other causes, not much
more was heard of the scheme till 1845. In 1846 _La Société d’Etude du
Canal de Suez_ was formed, and among those who turned their attention to
the subject was Robert Stephenson. His report was wholly unfavourable to
the enterprise. He recommended the construction of a railway through
Egypt, and a line was accordingly made between Alexandria and Suez. But,
notwithstanding the opinion of Mr. Stephenson, M. Lesseps persevered
with wonderful energy, believing, on the report of other engineers, that
the scheme could be successfully carried out. It is right, however, to
state that Mr. Stephenson did not say it was impossible to complete the
Suez Canal—he merely gave it as his opinion that the cost of making the
canal, and keeping it in a proper state for navigation, would be so
great that the scheme would not pay. However, in 1854, the Viceroy of
Egypt signed the concession, and in 1860 the work was actually
commenced, but not on a plan that was advocated by the English engineers
of making the canal 25 feet above the sea level. There were also some
political and financial difficulties to be overcome. The Suez Canal
Company, it was said, had expended twelve millions of money in what was
considered to be chiefly shifting sands.

[Illustration:

  FIG. 123.—_The Sand-Glass._
]

When the Suez Canal was projected, many prophesied evil to the
undertaking, from the sand of the Desert being drifted by the wind into
the canal, and others were apprehensive that where the canal was cut
through the sand, the bottom would be pushed up by the pressure of the
banks. They imagined that the sand would behave exactly like the ooze of
a soft peat-bog, through which, when a trench has been cut, the bottom
of the trench soon rises, for the soft matter has virtually the
properties of a liquid: it acts, in fact, exactly like very thick
treacle. Sand, however, is not possessed of liquid properties; it has a
definite angle of repose, which is not the case with thin bog. This
behaviour of sand is familiarly illustrated in the sand-glass, which the
diagram Fig. 123, will recall to mind. It may be observed that the sand
falling in a slender stream from the upper compartment is in the lower
one heaped up in a little mound, the sides of which preserve a nearly
constant inclination of about 30°. In this property it is distinctly
different from peat-bog or such-like material, which has no definite
angle of repose. It need hardly be said that all apprehensions as to the
safety of the canal from the causes here alluded to have proved
unfounded.

But if some English engineers appeared to oppose the project, another
eminent one, Mr. Hawkshaw, certainly helped it on at a moment when the
Viceroy of Egypt was losing confidence; and, had his opinion been
adverse to the project reported upon, the Viceroy would certainly not
have taken upon himself additional liability in connection with the
undertaking, and the money expended up to that date would have been
represented only by some huge mounds of sand and many shiploads of
artificial stone, thrown into the bottom of the sea to make the harbour
of Port Saïd. And that M. Lesseps appreciated the good offices of Mr.
Hawkshaw is shown from the fact that, when he introduced that engineer
to various distinguished persons, on the occasion of the opening of the
canal, he said, “This is the gentleman to whom I owe the canal.” It
cannot, therefore, be said of the English nation that they were jealous
of the peaceful work of their French neighbours, or opposed it in any
other sense but as a “non-paying” and apparently unprofitable scheme.

The Canal was opened in great state by Napoleon III.’s Empress Eugénie,
in November, 1869, when a fleet of fifty vessels passed through, and the
fact was thus officially announced in Paris:—“The canal has been
traversed from end to end without hindrance, and the Imperial yacht,
_Aigle_, after a splendid passage, now lies at her moorings in the Red
Sea.

“Thus are realized the hopes which were entertained of this great
undertaking—the joining of the two seas.

“The Government of the Emperor cannot but look with satisfaction upon
the success of an enterprise which it has never ceased to encourage. A
work like this, successfully accomplished in the face of so many
obstacles, does honour to the energetic initiative of the French mind,
and is a testimony to the progress of modern science.”

An Imperial decree was then issued, dated the 19th of November,
appointing M. de Lesseps to the rank of Grand Cross of the Legion of
Honour, in consideration of his services in piercing the Isthmus of
Suez.

The Suez Canal is 88 geographical, or about 100 statute miles long: its
average width is 25 yards, and the minimum depth, 26 feet. At intervals
of five or six miles, the canal is widened, for a short space, to 50
yards, forming thus sidings (_gares_) where only vessels can pass each
other. At these, therefore, a ship has often to wait until a file of
perhaps twenty steamers, coming the other way, has passed. Occasionally
a ship gets across, or “touches,” and then the canal is blocked for
hours. So much inconvenience has been found from the restricted
dimensions of the work, that in 1886 it was proposed to widen the canal,
or, alternatively, to construct a second canal, and use the two like the
lines of a railway, so that vessels would never have occasion to pass
each other. The amount of traffic is very large, and has been steadily
increasing. Thus, in 1874, the tonnage of the vessels passing through
was 5,794,400 tons; in 1880, the tonnage was 8,183,313, and the receipts
of the Company amounted to £2,309,218. In 1875, the British Government
purchased, from the Khedive, £4,000,000 worth of shares.

[Illustration:

  FIG. 124.—_A Group of Egyptian Fellahs, and their Wives._
]

The Suez Canal is not so much a triumph of engineering as a monument of
successful enterprise and determination on the part of its great
promoter, M. Lesseps, in the face of great difficulties. According to
the original programme, the canal was to have been constructed by forced
labour, supplied by the Viceroy. The unhappy peasantry of the country,
called “fellahs,” were compelled to give their labour for a miserable
pittance of rice. No doubt, in ancient times, when forced labour was in
use, every peasant might cheerfully work, because it was for the general
benefit to bring sweet water from the Nile to other dry and thirsty
places in Egypt; but to be obliged to work at a waterway of salt, which
was only to be of use to foreigners who passed through the country,
could not be expected of human beings, and therefore the carrying out of
the work was not unaccompanied by cruelties of the nature attending
slave labour in other lands. This was one of the reasons why the late
Lord Palmerston opposed the canal scheme, for the kind hearted statesman
bore in mind the loss of health and life occasioned to poor Egyptians by
this mode of labour, and the more so because it had been originally
proposed that one of the conditions on which the French Company was to
take up the project should be the execution of the work by _free
labour_. In consequence, no doubt, of representations from free
countries, the Porte was induced to put a veto on the employment of
forced labour, and everyone thought that this would be the deathblow to
the completion of the canal: but M. Lesseps did not give way to despair,
and he since stated that if he had depended on the labours of the
fellahs only, the difficulties of the work never could have been
surmounted; and that, in fact, the successful prosecution of the work
was owing to his having turned his attention to the mechanical
contrivances used for dredging on the Thames and the Clyde, from which
he obtained better results in half the time and at half the cost.

[Illustration:

  FIG. 125.—_Dredges and Elevators at Work._
]

[Illustration:

  FIG. 126.—_Map of the Suez Canal._
]

The dredges used in the construction of the canal were of a new
description. They were wonderful mechanical contrivances, and but for
them the canal would not have been finished. They were not the
contrivance of M. Lesseps, but of one of the contractors, a
distinguished engineer, who received his technical education in France
but his practical experience in England. The use of the dredging
machines was prepared for by digging out a rough trough by spade work,
and as soon as it had been dug to the depth of from six feet to twelve
feet, the water was let in. After the water had been let in, the steam
dredges were floated down the stream, moored along the bank, and set to
work. The dredges were of two kinds. The great _couloirs_ consisted of a
long, broad, flat bottomed barge, on which stood a huge framework of
wood, supporting an endless chain of heavy iron buckets. The chain was
turned by steam, and the height of the axle was shifted from time to
time, so that the empty buckets, as they revolved round and round,
should always strike the bottom of the canal at a fixed angle. As they
were dragged over the soil they scooped up a quantity of mud and sand
and water, and as each bucket reached its highest point in the round, it
discharged its contents into a long iron pipe which ran out at right
angles to the barge. The further extremity of this pipe stretched for
some yards beyond the bank of the canal, and therefore, when the
dredging was going on, there was a constant stream of liquid mud pouring
from the pipe’s mouth upon the shore, and thus raising the height of the
embankment. When the hollow scooped out by the buckets had reached the
required depth, the dredge was moved to another place, and the same
process was repeated over and over again. These stationary dredges,
however, though very effective, required much time in moving, and the
lighter work of the canal was chiefly effected by movable dredges of a
smaller size. These machines were of the same construction as those
described; the only difference was that the mud raised by their agency
was not poured directly on shore by pipes attached to the dredges, but
was emptied in the first instance into large barges moored alongside the
dredge. These barges were divided into compartments, each of which
contained a railway truck, and when the barge was filled it steered away
to the bank, where an elevator was fixed. The trucks, filled with mud
were raised by a crane worked by steam power, and placed upon inclined
rails, attached to the elevator, which sloped upwards at an angle of 45
degrees towards the bank. They were then drawn up the rails by an
endless rope, and as each truck reached the end of the rails its side
fell open, the mud was shot out upon the bank, and the empty truck
returned by another set of rails to the platform on which the elevator
was placed, and was thence lowered into the barge to which it belonged.
As the elevator could unload and re-load a barge much faster than the
dredges could fill it with mud, each elevator was fed by half a dozen
dredges, and thus the mud raised from the canal by several dredges was
carted away without difficulty at one and the same time. As these
floating dredges were much easier to shift than those encumbered by the
long _couloir_ pipes, the work of excavating the bed went on much more
rapidly. But in places where there was any great mass of earth or sand
to be removed, the large _couloirs_ could scoop out a given volume in a
shorter time.

The traveller who wishes to see the canal should go to France, and,
embarking at the port of Marseilles, cross the Mediterranean Sea, and
steam to Port Saïd, which is about 150 miles east of the port of
Alexandria, where the isthmus is crossed by the railroad, and is used by
travellers to India, being known as the “overland route.” And this
railway conveys the mail to and from India, thus saving the great sea
voyage round Africa and the Cape of Good Hope. Nevertheless, it involves
two transhipments—from the steamer to the rail at Alexandria, and from
the railway to the steamer at Suez.

[Illustration:

  FIG. 127.—_Port Saïd, the Mediterranean entrance to the Suez Canal._
]

Let us notice in order the places passed by the traveller in going from
Port Saïd to Suez and the Red Sea. The arrow (Fig. 126) points in the
direction of the compass, and shows that the canal runs very nearly from
north to south. Port Saïd is the little town at the northern or
Mediterranean entrance to the canal, situated on the flat sands at the
entrance of the canal, and is built chiefly of wood, with straight wide
streets and houses, and although it now contains several thousand
inhabitants, before the making of the canal was begun one hundred people
could hardly have been got together. The town contains nothing deserving
of notice, and has a striking resemblance to the newly settled cities of
America. But in it reside agents who represent numerous varied
interests—administrative, financial, mercantile and political. It is
provided with docks, basins, quays and warehouses, and has a harbour
stretching out a couple of miles or so into the sea, for to that
distance two piers, or rather breakwaters, run out.

Fig. 128 shows these two converging breakwaters, which have been built
out into the Mediterranean from the coast, the larger and more westerly
one being one mile and a half long, the shorter about a mile and a
quarter, and the distances between the two lighthouses erected on the
extremities of the breakwater being half a mile.

The piers are made of concrete which was cast in blocks weighing 10 tons
each. This composition has of late years been greatly approved by
engineers where stone cannot be procured. The sea-face of the great
canal in Holland is composed of a similar artificial stone, and it is
found to bear the wear and tear of the waves almost, if not quite, as
well as ordinary stone. It is stated that 25,000 blocks, each weighing
10 tons, were used. They were not laid with the regularity of ordinary
masonry, but had been dropped from large barges, so that they presented
a very rugged and uneven appearance (Fig. 129); but the object of
throwing out these great bulwarks is for the purpose of preventing the
sand brought down by the Nile silting in and closing up the canal. Along
the western pier there is, from this cause, a constant settlement of
sand, which was partially washed through the interstices left between
the blocks of artificial stone, and might have given some trouble by
forming sandbanks in the harbour; but this was prevented by the
introduction of smaller stones, which could readily be carried out in
boats at the low tide.

[Illustration:

  FIG. 128.—_Bird’s-eye View of Port Saïd._
]

Beginning with the Mediterranean Sea and Port Saïd, there is a run of 28
miles to Kantara, through Lake Menzaleh. Although called a lake, it is,
in truth, nothing but a shallow lagoon or swamp, in which water-fowl of
all kinds are very abundant, the great flocks of white pelicans and pink
flamingoes being especially striking. The waters of this lagoon cover
lands that once were fertile, and the salt sea-sands doubtless conceal
the remains of many an ancient town.

[Illustration:

  FIG. 129.—_One of the Breakwaters at Port Saïd._
]

Of all portions of the undertaking, this one, M. Lesseps states, was the
most arduous and difficult, though, at the time, it attracted the least
attention. A trough had to be dredged out of the bed of the shallow
lagoon, and on either side of this hollowed out space high sandbanks had
to be erected, and the difficulty of making a solid foundation for these
sand banks was found to be extreme. The difficulty, however, was
surmounted, and such is the excellence of the work, that the water
neither leaks out, nor does any of the brackish water of the lagoon
infiltrate and undermine the great embankments.

[Illustration:

  FIG. 130.—_Lake Timsah and Ismaïlia._
]

At Kantara, the canal crosses the track of the highway between Cairo and
Syria—a floating bridge carries the caravans across; and near this spot
is stationed an Egyptian man-of-war, which supplies the police for the
proper watch and ward of the canal. From Kantara to El Fendane is a
distance of 15 miles—that is to say, to the southern extremity of Lake
Ballah, where the canal still passes through sand embankments, raised
within a mere. The lake is, however, almost dried up, and therefore the
difficulties which had to be surmounted at Lake Menzaleh were not felt
here.

The traveller may now be supposed to have arrived at Lake Timsah, where,
no doubt, in the days of the Pharaohs, a lake existed. When taken in
hand by M. Lesseps, it was a barren, sandy hollow, containing a few
shallow pools, through which a man could easily wade, but now it is
filled with the waters of the Mediterranean Sea. It is a pretty, inland,
salt water lake, about three miles in width. On the northern shore
stands the town, or, rather, small settlement of Ismaïlia, which is, in
fact, the “half way house” where most of the officials of the Suez Canal
Company resided, as they could get to either end of the canal with
greater facility, or to Cairo by the railroad, which comes to this
point, and continues, with the canal, to Suez.

[Illustration:

  FIG. 131.—_Railway Station at Ismaïlia._
]

When the canal was opened, in November, 1869, Ismaïlia was the scene of
the most brilliant part of the opening ceremony, in which the French
Empress Eugénie, the Empress of Austria, the Crown Prince of Prussia,
and other distinguished personages took share. The Khedive built himself
a summer palace, and M. Lesseps erected a villa, and the town was most
artistically laid out, with every prospect of becoming a flourishing
place. But the drainage had been so entirely overlooked, that it is said
the sewage found its only outlet in the fresh water canal; and the
consequence was fever broke out and so infected the town, that it was
soon almost quite deserted. In 1882, Ismaïlia was once more the scene of
bustle and activity, for here was the base of Sir Garnet Wolseley’s
operations in his brilliant campaign against Arabi. The British Navy
entered the canal, and took possession of Ismaïlia, where the army and
the military stores were rapidly concentrated. From this place, Sir
Garnet advanced along the route of the railway and the Sweet Water
Canal, and, after storming the lines of Tel-el-Kebir, occupied Cairo,
without further resistance, after a campaign of only three weeks’
duration.

From Lake Timsah to the Bitter Lakes the canal again passes for eight
miles or so through the desert, where, by partial excavations by hand
labour and subsequent flooding to admit the dredges, it was considered
that a sufficiently deep channel could be made. The _couloirs_ were set
to work, when suddenly “a lion arose in their path” in the shape of a
great rock, about 80 feet in length, and lying 12 feet only below the
surface, and right in the middle of the main channel. If anything could
show the indomitable energy of M. Lesseps it was his courage in dealing
with this difficulty, and at a time when a few months only could elapse
before the advertised day of the opening. He attacked the sunken rock
with gunpowder. A large raft, or floor, supported on barges, was moored
over the sunken rock, and from this men, armed with long poles shod with
steel, drilled numerous holes, into which charges of gunpowder were
placed, and fired in the usual manner by the electric battery. This
temporary obstruction occurred opposite to the landing place at
Sérápeum.

[Illustration:

  FIG. 132.—_The Viceroy of Egypt cutting the last embankment of the
    Reservoir of the Plain of Suez, to unite the two seas—the
    Mediterranean and the Red Sea._
]

Passing by Sérápeum, the traveller arrives at a vast expanse of water
called the “Bitter Lakes,” because the dry sandy hollow formerly
contained a marsh, or mere, of very brackish water. The possibility of
keeping this great area filled with sea water had been denied by the
opponents of the canal, who said the water would sink into the sand or
be evaporated by the intense heat of the sun; but none of these
prognostications have been verified, and it is now a great inland sea,
far surpassing Lake Timsah, being 25 miles long and from six to seven
miles wide. The only difficulty in filling this enormous natural basin
arose from the rapidity and force with which the waters flowed in. This
was done when the water at Suez was at low tide, and then subsequently
the Red Sea was allowed to flow in. Though the expanse of water in the
Bitter Lakes is great enough, the available channel is still narrow. But
the steamers can proceed at full speed, as here there are no banks to be
washed away.

Since the two seas have joined their waters, a strong current has set in
from south to north, but there is no eddy or fall at the place where the
waters meet. The tide runs up the canal with great force, and there is a
difference of six or seven feet between high and low water: but the tide
does not extend beyond the Bitter Lakes, where it is gradually diffused
and lost. The colour of the current of water from Suez is said to be
green, whilst that portion fed by the Mediterranean is blue. Since the
Bitter Lakes have been filled the mean temperature of the districts on
the banks has fallen 5° Centigrade. It is also stated that, although the
canal swarms with sea fish they keep to their respective ends of the
canal, as if the Mediterranean fish would not consort with those of the
Red Sea, or, rather, make themselves at home in strange waters. There is
also, perhaps, another cause, and that is the very bitter nature of the
water at the northern end of the Bitter Lakes, which acts as a natural
barrier, through which the fish may decline to pass.

The bed of the Bitter Lakes is the only portion of the canal’s course in
which it was not necessary to make a cutting. Buoys are laid down to
mark the best channel, but such is the width and depth of the water that
vessels need not exactly keep within them. Quitting the Bitter Lakes we
again enter the canal proper. In order to reach the vast docks which the
Suez Canal Company has constructed on the western coast of the Red Sea,
the canal is now quitted, and the vessel crosses the neck of the Red
Sea. The Cairo and Alexandria Railway has been extended two miles, and
is carried through the sea on an embankment, which lands the train close
to the docks and quays of the canal, so that passengers by the overland
route are able to embark from the train on board the steamer, and thus
escape the troublesome transhipment of themselves and luggage.


                      _THE MANCHESTER SHIP CANAL._

The project of constructing a ship canal to connect Manchester with the
sea appears to have been started just before the railway era, but it was
then abandoned, as the opening of the Liverpool and Manchester Canal
brought about an immediate reduction in the rates of carriage. Perhaps
it was the success of the Suez Canal which caused the revival of this
scheme, in 1880, combined with the depression of the cotton trade at
that period, when the Liverpool dock dues and the comparatively high
railway rates proved a heavier tax than usual on the great Lancashire
industry. The first definite steps were taken two years afterwards, when
two plans were submitted for the selection of a committee. One scheme
proposed to construct the canal without any locks; but, as Manchester is
60 feet above the sea level, there would, it was felt, be certain
inconveniences in loading or unloading ships in a deep depression. The
other plan was submitted by Mr. Leader Williams, a well known canal
engineer, who proposed to take the canal from Runcorn, a distance of 20
miles, and making use of locks. When Parliament was applied to for
powers authorizing the prosecution of the enterprise, there was, of
course, much opposition offered by the various interests involved, and
the inquires before the Committees of each House of Parliament were
unusually protracted, for they extended in all to 175 days, and the cost
to the promoters is said to have amounted to £150,000. Then, when the
Bill had passed, it was found that the capital (£8,000,000) could not be
raised owing to the financial depression, and partly also to some want
of confidence in the soundness of the undertaking on the part of the
Lancashire capitalists. But the promoters submitted the whole scheme to
a representative committee, who should consider any possible objections.
This committee reported (after sitting almost daily for five weeks) upon
every point, and were unanimous in pronouncing the undertaking to be
perfectly practicable and commercially sound. After this there was no
difficulty in raising the required capital, which was subscribed by
corporate bodies as well as private persons. The contract was let for
£5,750,000, and the work was commenced in November, 1887, the contractor
undertaking to have the canal completed and ready for traffic by January
1st, 1892.

[Illustration:

  FIG. 133.—_Western Portion._
]

[Illustration:

  FIG. 134.—_Eastern Portion._

  FIGS. 133 AND 134.—_Map of the Manchester Ship Canal._
]

The Manchester Docks of this canal will cover an area of nearly 200
acres at the south-western suburb of that city, and from there the canal
traverses the Valley of the Irwell, following, indeed, the general
course of the river, but not its windings, so that the bed of the river
is, in the distance of eight miles, or down to its junction with the
Mersey, repeatedly crossed by the line of the canal. From the confluence
of the rivers, the canal traverses the Valley of the Mersey, for this is
the name retained by the combined streams. The course of the river, in
its progress towards the sea, now makes wider bends, but the canal
proceeds, by a slight and nearly uniform curve, to Latchford, near
Warrington, passing to the south of which last named place it follows a
straight line to Runcorn, which is at a distance of 23 miles from
Manchester. Here it reaches what is now the estuary of the Mersey, but
the embankments are continued along the southern shore to Eastham, where
the terminal locks are placed. In this part of the canal, the engineer
had difficulties to overcome of a different nature from those
encountered in the upper part, where it was chiefly a matter of cutting
across the ground intervening between the bends of the river, so as to
form for its waters a new and direct channel everywhere of the requisite
breadth and depth. But when Runcorn has been passed, and Weston Point
rounded, there is the mouth of the River Weaver to be crossed, and this
is marked by a great expanse of loose and shifting mud. Other affluents
of the Mersey are dealt with by means of sluices, and in one instance
the waters of a river are actually carried beneath the course of the
canal by conduits of 12 feet in diameter. The total length of the canal
from Manchester to the tidal locks at Eastham is 35 miles.

[Illustration:

  FIG. 135.—_A Cutting for the Manchester Ship Canal._
]

[Illustration:

  FIG. 136.—_Blasting Rocks for the Manchester Ship Canal._
]

The minimum width of the canal at the bottom is 120 feet, its depth 26
feet. But for several miles below Manchester this width will be
increased, so that ships may be moored along the sides, and yet
sufficient space left for the up and down lines of traffic in the
middle. In this way, works and manufactories on the banks will be able
to load and unload their cargoes at their own doors, and it may be
expected that the advantages so offered will cause the banks of the
canal to be much in request for the sites of works of all kinds. At the
several places where the locks are placed there will be a smaller and a
larger one, side by side, so that water shall not be needlessly used in
passing a moderate sized vessel through the greater locks. As these last
are 550 feet long and 60 feet wide, they are capable of receiving the
largest ships, whilst the smaller locks are 300 feet long and 40 feet
wide. Again, both the larger and the smaller are provided with gates in
the middle, so that only half their length may be used when that is
found sufficient. Coming down the canal from Manchester, the first set
of locks will be at Barton, about three miles distance, just below the
place where the Bridgewater Canal is carried across the Irwell, which is
now to become the ship canal, by means of the aqueduct of 1760, by which
Brindley became so famous. There is a story told about Brindley being
desirous of satisfying the duke about the practicability of his plan,
and requesting the confirmatory opinion of another engineer. When,
however, this gentleman was taken to the place where it was proposed to
construct the aqueduct, he shook his head, and said that he had often
heard of castles in the air, but had never before been shown where any
of them were to be erected. This aqueduct is about 600 feet long, and
the central one of its three arches spans the river at a height of
nearly 40 feet above the water. But the Manchester Ship Canal requires a
clear headway of 75 feet, and Mr. Williams is going to replace the fixed
stone structure by a swinging aqueduct, or trough of iron, which can be
turned round, so as to give a clear passage for ships in his canal. This
trough, or great iron box, will have gates at each end, and gates will
be provided in the aqueduct at each side, so that no water will be lost
when the water bridge is turned aside. But more than this; hydraulic
lifts have been designed, so that, in a few minutes, vessels can be
lowered from the Bridgewater Canal into the Manchester Canal, or raised
from the latter into the former while still floating in water. The
supply of water for the canal will be ample, as it has the rivers
Irwell, Mersey and Bollin, with their tributary streams, to draw from.
It should be mentioned that the terminal locks at Eastham will be of
somewhat larger dimensions than those already referred to, and will be
three in number. The largest, which is on the south or landward side,
will be 600 feet by 80 feet, the middle one 350 feet by 50 feet, and the
smallest one 150 feet by 30 feet. These three locks will be separated by
concrete piers 30 feet wide, on which will be placed the hydraulic
machinery for opening and closing the gates. Besides the ordinary gates,
there will be provided for each lock at Eastham an outer pair of
storm-gates that will be closed only in rough weather. These gates will
shut from the outside against the lock sills, and, by resisting the
force of wind and waves, will protect the ordinary tidal gates from
being forced open. The lock gates throughout will be made of a wood
obtained from British Guiana, and known as _greenheart_. This timber is
the product of a large tree (_Nectandra Rodiœi_) belonging to the laurel
family. It is a very heavy and close grained wood, the strength and
endurance of which have been proved many years ago by its use in
ship-building, etc., and some of the logs imported for the canal are
remarkably fine specimens, being 22 inches square and 60 feet long. A
pair of the largest gates weigh about 500 tons. The gates of the tidal
locks at Eastham will all be open for half the time of each tide, when
there will be a depth of water, above the sills, greater by 11 feet than
that of any dock in Liverpool or Birkenhead.

[Illustration:

  FIG. 137.—_Manchester Ship Canal Works, Runcorn._
]

The way in which the difficulty is overcome of crossing the several busy
lines of railway that intersect the course of the new canal, so that
their traffic shall not be impeded, is one of special interest in this
bold scheme. The London and North Western Railway crosses the Mersey at
Runcorn by a bridge that leaves a clear headway of 75 feet at high
water, and it was determined that this headway should be maintained in
the bridges over the canal. The use of swing bridges on lines of railway
over which trains are constantly passing being out of the question, it
is necessary that the railways be carried over the canal at the required
height. It is accordingly laid down in the Act of Parliament that before
the Canal Company can cut the existing lines of railway it shall
construct permanent bridges, and carry over them lines rising by
gradients not exceeding 1 in 135, and not only so, but these deviation
lines must be previously given up to the several railway companies for
six months to be tried experimentally in that period for goods traffic.
The cost of constructing these deviation lines, which, in all, will not
be far short of 12 miles of new railway, will not be much less than
£500,000. The traffic of the canal will probably have great feeders at
certain points in the other canals and the railway lines that reach it.
For instance, the Bridgewater Canal, now incorporated with the greater
undertaking, will bring traffic from the Staffordshire potteries, the
river Weaver brings salt laden barges from Cheshire, and at other points
the railways will bring the produce of the excellent coal fields of
South Yorkshire and South Lancashire, which will be automatically
transferred from the waggons into ocean going steamships.

[Illustration:

  FIG. 137_a._—_The French Steam Navvy._
]

[Illustration:

  FIG. 137_b_.—_The English Steam Navvy._
]

Though the general notion of the construction of the canal as a deep,
wide trench, or cutting following the course shown on the map, is
sufficiently simple, the operation of carrying this into practice
involves the exercise of great skill and ingenuity in dealing with
mechanical obstacles. Man’s operations in the world consist but in
changing the position of masses of matter; and the properties of
matter—its inertia, cohesion, gravitation, etc., are the forces that
oppose his efforts. The quantity of matter to be shifted in excavating
this trench of thirty-five miles long across the country was no less
than sixty millions of tons. The number of “navvies” employed at one
time has been 15,000; but even this army of workmen would have made but
slow progress with a cutting of this magnitude, had not the “strong
shouldered steam” been also called into operation for scooping out the
soil. The illustrations (Figs. 137_a_ and #137_b_:fig137b) will show the
arrangement of two forms of “steam navvies” that were much used on the
works. One (Fig. 137_a_) is similar to the dredgers used for clearing
mud out of rivers and canals: it consists of a series of scoops, or
buckets, mounted on an endless chain, so as to scrape the material from
an inclined embankment and tip it into waggons for removal. The other
(Fig. 137_b_) may be compared to a gigantic ladle made to scrape against
the face of a cutting in rising, and filling each time its bucket with
nearly a ton of the material. It is most interesting to witness the
perfect control which the man at the levers exercises over this machine,
the movements of which he directs with as much precision as if he were
handling a spoon. One of these steam navvies is able to fill 600 waggons
or more—that is, to remove 3,000 tons of material—in one day; and as
many as eighty of them have been simultaneously used on the Canal works.
The value of the plant employed by the contractor is estimated at
£700,000, and the length of temporary railway lines (see Fig. 137), for
transport of the “spoil,” etc., is said to exceed 200 miles. There is a
main line running through from one end of the canal to the other, and
known to the workmen as the “Overland Route.” From this diverge numerous
branches, some to the bottom of the excavations in progress, others to
embankments down which is tipped out the “spoil,” as the dug out
material is called; while others connecting with brickfields and
quarries, or with existing canals and railway lines, serve to bring
supplies of the materials used in the constructions. Some 150
locomotives are constantly at work on these temporary lines, and the
coal consumed by them, and by the steam navvies, steam cranes, pumping
engines, etc., is equivalent to about two train loads every day.

Though the Manchester Ship Canal is to be nearly twice as wide as the
Suez Canal, its width for some miles below Manchester will be still
greater, for there the banks will form long continuous wharves for the
accommodation of the works and factories that are certain to be
attracted to the spot. Indeed, so obvious are the advantages of ocean
shipment, and so extensive the industries of South Lancashire, that it
is not improbable the whole course of the canal may, in process of time,
be lined with wharves, and the two great cities of Manchester and
Liverpool may be united by a continuous track of dense population. Be
that as it may, there seems every reason to believe that the undertaking
will be a financial success. Calculation has shown that if the cotton
alone that enters and leaves Manchester were carried by the canal at
half the rates charged by the railways, there would result not only an
annual saving of £456,000 to the cotton trade, but a clear profit to the
canal company sufficient to pay more than 3 per cent. interest on its
own capital. And, again, the railway and other local interests that have
hitherto been opposed to this great enterprise can hardly fail to be in
the long run benefited by the enlarged prosperity and increased general
trade and manufactures it will develop. So that it will presently be
found that there is room enough and work enough for both canal and
railways.

The Manchester Ship Canal, so far from having been ready for traffic on
the 1st January, 1892, was not completed until the end of 1893, and it
was only on the 16th December, 1893, that the directors and their
friends made the trial trip throughout its entire length, accomplishing
the distance of 35½ miles in 5½ hours. The total cost of the canal was
greatly in excess of the estimates, which placed it at eight million
pounds, as fifteen millions is the sum actually expended upon it. With
such a vast capital expenditure, it may be some time before the ordinary
shareholders can look for dividends, especially as there has not been
any sudden rush of traffic, such as many sanguine people expected. On
the other hand, traffic is continuously and steadily increasing, and
there is reason to believe that this great work will ultimately prove a
commercial, as it has an engineering, success.

[Illustration:

  FIG. 137_c._—_Sketch Map of The North Sea Canal._
]


                         _THE NORTH SEA CANAL._

Like several other canals for sea going ships this last addition to the
achievements of modern engineering is but the realisation of a project
conceived at a long past period. The idea of a canal to connect the
Baltic and the North Sea dates back into the Middle Ages, and indeed a
short canal was constructed in 1389, which by uniting two secondary
streams of the peninsula really did provide a waterway between the two
seas. The inefficiency of this means of communication may be inferred
from the fact of there having been proposed since that period no fewer
than sixteen schemes of canalisation between these two seas, of which
the recently completed North Sea Canal is the sixteenth, and it need
hardly be said the greatest, so that in comparison with it the rest
vanish into insignificance. The canal was commenced in 1887, and on the
20th of June, 1895, it was opened by the reigning Emperor of Germany,
William II., with a very imposing naval pageant in which nearly a
hundred ships of war from the great navies of the world took part. A
glance at the accompanying sketch-map will show the great importance of
this canal as a highway of commerce. The entrance to the Baltic has
hitherto been round the peninsula of Denmark and through the narrow
“belts” and “sounds” that divide the Danish Islands, a course beset with
imminent perils to navigators, for the channels abound in rocks and
dangerous reefs, to say nothing about the frequent storms and the
impediments of ice floes. Yet as many as 35,000 vessels have lately had
to take that course annually, these representing a total tonnage of no
less than 20,000,000 tons. The figures speak for the magnitude of the
Baltic shipping intercourse with the rest of the world; while the losses
incurred in traversing these forbidding waters may be gathered from the
statement that since 1858, nearly 3000 ships have been wrecked in them,
and a greater number much damaged. Indeed, for large vessels, there is
hardly a more dangerous piece of navigation in all Europe. The
importance of this canal must not therefore be estimated solely by the
saving of length in ships’ course, though that is great, as the map
shows.

The North Sea Canal is 61 miles long, 200 ft. wide at the surface, 85
ft. wide at the bottom, and it will admit of vessels of 10,000 tons
register passing through, the average time of transit being about twelve
hours. The estimated cost of this undertaking was nearly eight and a
quarter million pounds sterling, and about one-third of this sum was
contributed by Germany, for whom the canal is of the greatest strategic
importance in case of war, for her fighting ships need not then traverse
foreign waters. The construction was therefore pushed forward with
unusual energy, as many as 8,600 men having been engaged on the works at
one time. An important naval station already exists at Kiel, the Baltic
end of the canal, where there is a splendid harbour. The engineer and
designer of this water-way is Herr Otto Baensch, who has devised much
ingenious machinery in connection with the immense tidal locks at the
extremities of the canal, and the swing bridges by which several lines
of railway are carried across it. In the construction of this canal
there were no vast engineering difficulties to be overcome, and hence
striking feats of mountain excavation or valley bridging are not to be
met with in its course, though in places there are some deep cuttings.
The methods of excavating and of steam dredging that were made use of
have already been illustrated in relation to the other works described
in this article. The country through which the canal passes does not
present any unusually picturesque features.


               _THE PANAMA AND NICARAGUA CANAL PROJECTS._

The several undertakings described in our chapter on Ship Canals are now
all completed and in active operation, and but for financial
mis-management and dishonest speculations, the same might probably have
been said of another great project, the name of which was on everyone’s
lips a short time ago, but in which public interest has lately waned;
perhaps from a mistaken impression that the construction itself is
involved in a common ruin with the fortunes of so many of its promoters,
or that the scheme was frustrated by some unforeseen and insurmountable
engineering difficulties. These assumptions have so little justification
that it is quite probable that Lesseps’ last great project may yet be
completed under more favourable auspices, and the Panama Canal unite the
Atlantic and Pacific Oceans. The Panama Canal Company still exists, and
possesses not only a very large part of the work almost quite finished,
but all the extensive plant in perfect condition for resuming
operations. The original scheme provided for a tidal water-way between
the two oceans, without the intervention of a single lock. The canal was
to be nearly 47 miles in length, 100 feet wide at the surface of the
water, 72 feet wide at the bottom, and 29 feet deep. The entrances are
at Colon on the Atlantic side, and at Panama on the Pacific. The latter
is the eastern extremity, and the western one is on the Atlantic side,
owing to the configuration of the isthmus which curves round the Panama
Gulf that opens to the south. A railway crosses the isthmus between the
points already named, and the route of the canal is laid down almost
parallel with this railway, from which it is nowhere far distant. For
the first 20 miles from the Atlantic side the land is only at a very
moderate elevation above the sea-level, say 25 or 30 feet, but the next
11 miles is more hilly, the elevations reaching at some points 150 to
170 feet, but these are only for short distances. A few miles farther
on, they rise still higher, until at Culebra the highest point is met
with, about 323 feet above the sea-level, and a cut of this depth, 1,000
feet long, would be required. Through this highest part it has been
proposed to drive a tunnel, but the total extent of the deep cutting at
this part of the canal would be nearly 2 miles in length. This would no
doubt be a work of the most formidable magnitude, for it has been
calculated that no less than 24,000,000 cubic yards of material,
consisting for the most part of solid rock, would have to be removed. It
is not supposed, however, to offer any great difficulty in an
engineering point of view. Doubtless it would be costly, and would take
some time to accomplish. Another heavy piece of work would consist in
constructions for controlling a mountain torrent called the Rio Chagres,
through the valley of which the canal passes. This stream is very
variable in the quantity of water it discharges, rising in the rainy
season 45 feet above its ordinary level, and sending down forty times as
much water as it does in the dry season.

Mr. Saabye, an American engineer, who examined unofficially the works of
the Panama Canal in 1894, considers that about one half of the total
excavation has already been done, and one half of the total length of
the canal almost finished, and remaining in comparatively good
condition. At both ends, including 15 miles on the Atlantic side, there
is water 18 to 24 feet deep. “Besides the work already done, the Canal
Company has on hand, distributed at both terminals, and at convenient
points along the canal route, an immense stock of machinery, tools,
dredges, barges, steamers, tug-boats, and materials for continued
construction. At Panama, La Boca, and Colon, as well as along the canal,
are numerous buildings—large and small—for offices, workshops,
storehouses, and warehouses, and for lodging and boarding the men who
were employed on the work. The finished work, as well as all the
machinery, tools, materials, buildings, etc., are well taken care of and
looked after. The Canal Company employs one hundred uniformed policemen,
besides numerous watchmen, machinists, and others, whose sole duty
consists in watching the canal and looking after needed repairs of plant
and care of materials. In fact, the work and the whole plant is in such
a condition, so far as I could ascertain, that renewed construction
could be taken up and carried to a finish at any time it is desired to
do so, after the Company’s finances will permit.”

An enormous amount of money has already been expended on the Panama
Canal, and much of it lavishly and unnecessarily. A reorganised company
may probably be able to form such estimates of the probable cost of
completing the work under careful and efficient management, that
financial confidence in it maybe restored. The canal not only already
possesses the requisite plant, but the route has the special advantages
of assistance in transport from the railway everywhere at but a short
distance from it, and fine commodious harbours for its ocean mouths. If
it were finished as originally designed, vessels could pass through it
with one tide, say in about six hours. It is understood that before the
Panama enterprise is again proceeded with, the Company think that a sum
of about £25,000 should be expended in a complete survey and re-study of
all the conditions, and the results submitted to the most eminent
engineers.

A rival scheme for carrying a ship canal across the isthmus that divides
the Atlantic and Pacific Oceans is that known as the Nicaragua Canal, as
the proposed route is to cross Lake Nicaragua, an extensive sheet of
water situated some 400 or 500 miles north-west of the Panama Canal. The
lake is 110 miles long and 45 miles broad, and is on its western side
separated from the Pacific by a strip of land only 12 miles wide, having
at one point an elevation not exceeding 154 feet, which is probably the
lowest on the isthmus. The lake drains into the Caribbean Sea on the
east, by the San Juan river, a fine wide stream, 120 miles in length,
which is navigable for river boats from the Caribbean Sea up to the
lake, except near its upper part, where some rapids at certain times
prevent the passage of the boats. This canal project first took definite
form in 1850, when a survey was made and routes reported on. The scheme
attracted some attention in the United States, and in 1872, and again in
1885, further surveys and estimates were made at the instance of the
States Government. The earlier schemes provided for the rise and fall
between sea and lake-–108 feet, a considerable number of locks—eleven on
each side, making the total length from sea to sea 181 miles. The report
of the latter advocated the canalization of the San Juan by a very bold
measure, namely, the construction of an immense dam, by which the waters
were to be retained in the valley for many miles at the level of the
lake. A company was formed to promote the project, and again in 1890
there were more surveys and estimates made. This company actually
expended a considerable sum of money in attempting to improve the
harbour at Greytown, which would have formed the eastern terminus, but
had become silted up. But it was found afterwards that it would be
better to recommend the formation of an artificial harbour at another
point, by constructing two long piers running out into the sea, although
this change would involve the abandonment of a few hundred yards of
canal already excavated by the company near Greytown. The company has
also laid down about 12 miles of railway along the proposed route, with
wooden and iron sheds as workshops, offices, etc., and, moreover, had
dredges and other appliances at work. At this stage it was proposed that
the United States Government should guarantee the bonds of the Nicaragua
Canal Company to the extent of more than twenty million pounds sterling.
By an Act of Congress passed in March, 1895, a commission of engineers
was appointed for the purpose of ascertaining the feasibility,
permanence, and cost of construction and completion of the Nicaragua
Canal by the route contemplated. The report of this commission is an
elaborate and exhaustive review of the whole scheme based upon a
personal examination of the route, and on the plans, surveys, and
estimates made for the company, whose records, however, are stated in
the report to be deficient in the supply of many important data. The
Canal Company’s project provided for the improvement of Greytown
harbour, as already stated, and from that place the canal was to proceed
westward at the sea-level to the range of high ground on the eastern
side of the isthmus, which elevation was to be ascended by three locks
of unusual depth, and a deep cut more than 3 miles in length, through
rock to a maximum depth of 324 feet. After passing this enormous cut,
the route provides for a series of deep basins, in which the water is
confined by numerous dams or embankments, the canal excavations being
confined to short sections through higher ground separating these
basins. The total length of these embankments will be about 6 miles, and
their heights will vary from a few feet to more than seventy. About 31
miles from Greytown the canal reaches the San Juan river, which,
however, by means of an enormous dam across the valley at a place called
Ochoa, 69 miles below the point at which it receives the waters of Lake
Nicaragua, is there practically converted into an arm of the lake. This
dam, which would raise the water of the river 60 feet above its present
level, and would, of course, flood the valley back to the lake, is the
most notable feature of the project. Its maximum height would be about
105 feet, and the weirs on its crest, to discharge the surplus water,
would require a total length of nearly a quarter of a mile. Twenty-three
smaller embankments would also be needed for retaining the waters; the
river would have to be deepened in the upper part, and a channel dredged
out in the soft mud of the lake for 14 miles beyond the river. The big
Ochoa dam is said to have no precedent in engineering construction, on
account of its great height and the enormous volume of the waters it is
intended to retain. No doubt its construction and safe maintenance are
within the range of engineering skill, when a thoroughly exhaustive
survey of the site has been made, and the necessary funds are
forthcoming. From the western shore of the lake its level would also be
extended by another great dam crossing the valleys of the Tola and the
Rio Grande, with a length of 2,000 feet and a height of 90 feet. The
canal would then be carried to the sea-level by a series of locks. The
length of the canal from sea to sea would be 170 miles, but of this only
40 miles of channel would require to be excavated. The total cost of the
work, as estimated by the Nicaragua Canal Company, would be about
fifteen million pounds sterling, but the State Commission of Engineers
thinks about double that amount would be a safer calculation, and taking
into account the imperfection of the data, even this might be exceeded
in certain contingencies. The Government of the United States has been
urged to expend a few thousand pounds on another engineering commission,
to make complete surveys, and consider all the practical problems
involved, including the final selection of a route.

[Illustration:

  FIG. 138.—_Britannia Bridge, Menai Straits._
]



                             IRON BRIDGES.


The credit of having invented the arch is almost universally assigned to
the ancient Romans, though the period of its introduction and the date
of its first application to bridge building are unknown. That some
centuries before the Christian era, the timber bridges of Rome had not
been superseded by those of more permanent construction is implied in
the legend of the defence of the gate by Horatius Cocles—a tale which
has stirred the heart of many a schoolboy, and is known to everybody by
Macaulay’s spirited verses, in which

                   “Still is the story told,
                   How well Horatius kept the bridge,
                     In the brave days of old.”

Some of the arched bridges built by the Romans remain in use to this day
to attest the skill of their architects. The Ponte Molo at Rome, for
example, was erected 100 B.C.; and at various places in Italy and Spain
many of the ancient arches still exist, as at Narni, where an arch of
150 ft. span yet remains entire. Until the close of the last century the
stone or brick arch was the only mode of constructing substantial and
permanent bridges. And in the present century many fine bridges have
been built with stone arches. The London and Waterloo Bridges across the
Thames are well-known instances, each having several arches of wide
span, attaining in the respective cases 152 ft. and 120 ft. The widest
arch in England, and one probably unsurpassed anywhere in its
magnificent stride of 200 ft., is the bridge across the Dee at Chester,
built by Harrisson in 1820. At the end of last century _cast_ iron began
to be used for the construction of bridges, a notable example being the
bridge over the Wear at Sunderland, of which the span is 240 ft. But
with the subsequent introduction of _wrought_ iron into bridge building
a new era commenced, and some of the great results obtained by the use
of this material will be described in the present article. In order that
the reader may understand how the properties of wrought iron have been
taken advantage of in the construction of bridges, a few words of
explanation will be necessary regarding the strains to which the
materials of such structures are exposed.

Such strains may be first mentioned as act most directly on the
materials of any structure or machine, and these are two in number,
namely, extension and compression. When a rope is used to suspend a
weight, the force exerted by the latter tends to stretch the rope, and
if the weight be made sufficiently great, the rope will break by being
pulled asunder. The weight which just suffices to do this is the measure
of the _tenacity_ of the rope. Again, when a brick supports a weight
laid upon it, the force tends to compress the parts of the brick or to
push them closer together, and if the force were great enough, the brick
would yield to it by being crushed. Now, a brick offers so great a
resistance to a crushing pressure, that a single ordinary red brick may
be capable of supporting a weight of 18 tons, or 40,320 lbs.—that is,
about 1,000 lbs. on each square inch of its surface. Thus the bricks at
the base of a tall factory chimney are in no danger of being crushed by
the superincumbent weight, although that is often very great. The
_tenacity_ of the brick, however, presents the greatest possible
contrast to its strength in resisting pressure, for it would give way to
a pull of only a few pounds. Cast iron resembles a brick to a certain
extent in opposing great resistance to being crushed compared to that
which it offers to being pulled asunder, while wrought iron far excels
the cast metal in tenacity, but is inferior to it in resistance to
compression.

The following table expresses the forces in tons which must be applied
for each square inch in the section of the metals, in order that they
may be torn apart or crushed:

 ┌───────────────────────┬──────────────────────┬──────────────────────┐
 │                       │ Tenacity per square  │Crushing pressure per │
 │                       │    inch, in tons.    │square inch, in tons. │
 ├───────────────────────┼──────────────────────┼──────────────────────┤
 │Cast iron              │          8           │          50          │
 │Wrought iron           │          30          │          17          │
 │Iron wire              │          40          │         ...          │
 └───────────────────────┴──────────────────────┴──────────────────────┘

Besides the direct strains which tend to simply elongate or compress the
materials of a structure or of a machine, there are modes of applying
forces which give rise to transverse strains, tending to twist or wrench
the pieces or to bend them, or rupture them by causing one part of a
solid to slide away from the rest. Strains of this kind no doubt come
into play in certain subordinate parts of bridges of any kind; but if we
divide bridges according to the nature of the strains to which the
essential parts of the structure are subject, we may place in a class
where the materials are exposed to crushing forces only, all bridges
formed with stone and brick arches; and in a second class, where the
material is subjected to extension only, we can range all suspension
bridges; while the third class is made up of bridges in which the
material has to resist both compression and extension. This last
includes all the various forms of girder bridges, whether trussed,
lattice, or tubular. The only remark that need be here made on arched
bridges is, that when cast iron was applied to the construction of
bridges, the chief strength of the material lying in its resistance to
pressure, the principle of construction adopted was mainly the same as
that which governs the formation of the arch; but as cast iron has also
some tenacity, this permitted certain modifications in the adjustment of
the equilibrium, which are quite out of the question in structures of
brick and stone.

[Illustration:

  FIG. 139.
]

[Illustration:

  FIG. 140.
]

[Illustration:

  FIG. 141.
]

[Illustration:

  FIG. 142.
]

The general principle of the construction of girder bridges is easily
explained by considering a simple case, which is almost within
everybody’s experience. Let us suppose we have a plank supported as in
Fig. 139. The plank will by its own weight sink down in the centre,
becoming curved in the manner shown; or if the curvature be not
sufficiently obvious, it may always be increased by placing weights on
the centre, as at _g_. If the length of the plank had been accurately
measured when it was extended flat upon the ground, it would have been
found that the upper or concave surface, _a b_, had become shorter, and
the lower or convex surface, _c d_, longer when the plank is supported
only at the ends—a result sufficiently obvious from the figure it
assumes. It is plain, then, that the parts of the wood near the upper
surface are squeezed together, while near the lower surface the wood is
stretched out. Thus, the portions in the vicinity of the upper and lower
surfaces are in opposite conditions of strain; for in the one the
tenacity of the material comes into play, and in the other its power of
resisting compression. There is an intermediate layer of wood, however,
which, being neither extended or compressed, receives no strain. The
position of this is indicated by the line _e f_, called the _neutral
line_. If the plank, instead of being laid flat, is put upon its edge,
as in Fig. 140, the deflection caused by its weight will hardly be
perceptible, and it will in this position support a weight which in its
former one would have broken it down. There is in this case a neutral
line, _e f_, as before; but as the part which is most compressed or
extended is now situated at a greater distance from the neutral line,
the resistance of the material acts, as it were, at a greater leverage.
Again the portions near the neutral line are under no strain; they do
not, therefore, add to the strength, although they increase the weight
to be supported, and they may, for that reason, be removed with
advantage, leaving only sufficient wood to connect the upper and lower
portions rigidly together. The form of cast iron beams, Fig. 141, which
were used for many purposes, depends upon these principles. The
sectional area of the lower flange, which is subjected to tension, is
six times that of the upper one, which has to resist compression,
because the strength of cast iron to resist pressure is about six times
greater than its power of resisting a pull. If the upper flange were
made thicker, the girder would be weaker, because the increased weight
would simply add to the tension of the lower one, where, therefore, the
girder would be more ready to give way than before. If we suppose the
vertical web divided into separate vertical portions, and disposed as at
Fig. 142, the strength of the girder, and the principle on which that
strength depends, will be in no way changed, and we at once obtain the
box girder, which on a large scale, and arranged so that the roadway
passes through it, forms the tubular bridge. It is only necessary that
the upper part should have strength enough to resist the compressing
force, and the lower the extending force, to which the girder may be
subject; and wrought iron, properly arranged, is found to have the
requisite strength in both ways, without undue weight. The various forms
of trussed girders, the trellis and the lattice girders, now so much
used for railway bridges, all depend upon the same general principles,
as does also the Warren girder, in which the iron bars are joined so as
to form a series of triangles, as in Fig. 143.

[Illustration:

  FIG. 143.
]

Girders have been made of wrought iron up to 500 ft. in length, but the
cost of such very long girders is so great, that for spans of this width
other modes of construction are usually adopted.


                           _GIRDER BRIDGES._

[Illustration:

  FIG. 144.—_Section of a Tube of the Britannia Bridge._
]

The Britannia Bridge, which carries the Chester and Holyhead Railway
across the Menai Straits, is perhaps the most celebrated example of an
iron bridge on the girder principle. It was designed by Stephenson, but
the late Sir W. Fairbairn contributed largely by his knowledge of iron
to the success of the undertaking, if he did not, in fact, propose the
actual form of the tubes. Stephenson fixed upon a site about a mile
south of Telford’s great suspension bridge, because there occurred at
this point a rock in the centre of the stream, well adapted for the
foundation of a tower. This rock, which rises 10 ft. above the low-water
level, is covered at high water to about the same depth. On this is
built the central tower of the bridge, 460 ft. from the shore on either
side, where rises another tower, and at a distance from each of these of
230 ft. is a continuous embankment of stone, 176 ft. long. The towers
and abutments are built with slightly sloping sides, the base of the
central or Britannia tower being 62 ft. by 52 ft., the width at the
level where the tubes pass through it, a height of 102 ft., being
reduced by the tapering form to 55 ft. The total height of the central
tower is 230 ft. from its rock foundation. The parapet walls of the
abutments are terminated with pedestals, the summits of which are
decorated by huge lions, looking landwards. As each line of rails has a
separate tube, there are four tubes 460 ft. long for the central spans,
and four 230 ft. long for the shorter spans at each end of the bridge.
Each line of rails, in fact, traverses a continuous tube 1,513 ft. in
length, supported at intervals by the towers and abutments. The four
longer tubes were built up on the shore, and were floated on pontoons to
their positions between the towers, and raised to the required elevation
by powerful hydraulic machinery. The external height of each tube at the
central tower is 30 ft., but the bottom line forms a parabolic curve,
and the other extremities of the tubes are reduced to a height of 22¾
ft. The width outside is 14 ft. 8 in. Fig. 144 shows the construction of
the tube, and it will be observed that the top and bottom are cellular,
each of the top cells, or tubes, being 1 ft. 9 in. wide, and each of the
bottom ones 2 ft. 4 in. The vertical framing of the tube consists
essentially of bars of ⟙-iron, which are bent at the top and bottom, and
run along the top and bottom cells for about 2 ft. The covering of the
tubes is formed of plates of wrought iron, rivetted to ⟙- and ∟-shaped
ribs. The thickness of the plates is varied in different parts from ½
in. to ¾ in. The plates vary also in their length and width in the
different parts of the tubes, some being 6 ft. by 1¾ ft., and others 12
ft. by 2 ft. 4 in. The joints are not made by overlapping the plates,
but are all what are termed _butt_ joints, that is, the plates meet edge
to edge, and along the juncture a bar of ⟙-iron is rivetted on each
side, thus: ╬. The cells are also formed of iron plates, bolted together
by ∟-shaped iron bars at the angles. The rails rest on longitudinal
timber sleepers, which are well secured by angle-iron to the ⟙-ribs of
the framing forming the lower cells. More than two millions of rivets
were used in the work, and all the holes for them, of which there are
seven millions, were punched by special machinery. The rivets being
inserted while red hot, and hammered up, the contraction which took
place as they cooled drew all the plates and ribs very firmly together.
In the construction of the tubes no less than 83 miles of angle-iron
were employed, and the number of separate bars and plates is said to be
about 186,000. The expansion and contraction which take place in all
materials by change of temperature had also to be provided for in the
mode of supporting the tubes themselves. This was accomplished by
causing the tubes, where they pass through the towers, to rest upon a
series of rollers, 6 in. in diameter, and these were arranged in sets of
twenty-two, one set being required for each side of each tube, so that
in all thirty-two sets were needed. There are other ingenious
arrangements for the same purpose at the ends of the tubes resting on
the abutments, which are supported on balls of gun-metal, 6 in. in
diameter, so that they may be free to move in any manner which the
contractions and expansions of the huge tubes may require. Each of the
tubes, from end to end of the bridge, contains 5,250 tons of iron. The
mode in which these ponderous masses were raised into their elevated
position is described in the article on “Hydraulic Power,” as it
furnishes a very striking illustration of the utility and convenience of
that contrivance. The foundation-stone of the central tower was laid in
May, 1846, and the bridge was opened in October, 1850. The tubes have
some very curious acoustic properties: for example, the sound of a
pistol-shot is repeated about half a dozen times by the echoes, and the
tubular cells, which extend from one end of the bridge to the other,
were used by the workmen engaged in the erection as speaking-tubes. It
is said that a conversation may thus be carried on with a person at the
other end of the bridge, a distance of a quarter of a mile. The rigidity
of the great tubes is truly wonderful. A very heavy train, or the
strongest gale, produces deflections in the centre, vertical and
horizontal respectively, of less than one inch. But when ten or a dozen
men are placed so that they can press against the sides of the tube,
they are able, by timing their efforts so as to agree with the period of
oscillation proper to the tube, to cause it to swing through a distance
of 1¼ in.—an illustration of facts of great importance in mechanics,
showing that even the most strongly built iron structure has its own
proper period of oscillation as much as the most slender stretched wire,
and that comparatively small impulses can, by being isochronous with the
period of oscillation, accumulate, as it were, and produce powerful
effects. Bridges are often tried by causing soldiers to march over them,
and such regulated movements form the severest test of the freedom of
the structures from dangerous oscillation. The main tubes of the
Britannia Bridge make sixty-seven vibrations per minute. The expansion
and contraction occurring each day show a range of from ½ in. to 3 in.
The total cost of the structure was £601,865.

A stupendous tubular bridge has also been built over the St. Lawrence at
Montreal, and the special difficulties which attended its construction
render it perhaps unsurpassed as a specimen of engineering skill. The
magnitude of the undertaking may be judged of from the following
dimensions: Total length of the Victoria Bridge, Montreal, 9,144 ft., or
1¾ miles; length of tubes, 6,592 ft., or 1¼ miles: weight of iron in the
tubes, 9,044 tons; area of the surface of the ironwork, 32 acres; number
of piers, 24, with 25 spans between the piers, each from 242 ft. to 247
ft. wide.

[Illustration:

  FIG. 145.—_Albert Bridge, Saltash._
]

Another singular modification of the girder principle occurs in the
bridge built by Brunel across a tidal river at Saltash, Fig. 145. Here
only a single line of rails is carried over the stream, which is,
however, 900 ft. wide, and is crossed by two spans of about 434 ft.
wide. A pier is erected in the very centre of the stream, in spite of
the obstacles presented by the depth of the water, here 70 ft., and by
the fact that below this lay a stratum of mud 20 ft. in depth before a
sound foundation could be reached. This work was accomplished by sinking
a huge wrought iron cylinder, 37 ft. in diameter and 100 ft. in height,
over the spot where the foundation was to be laid. The cylinder
descended by its own weight through the mud, and when the water had been
pumped out from its interior, the workmen proceeded to clear away the
mud and gravel, till the rock beneath was reached. On this was then
built, within the cylinder, a solid pillar of granite up to the
high-water level, and on it were placed four columns of iron 100 ft.
high, each weighing 150 tons. The two wide spans are crossed by girders
of the kind known as “bow-string” girders, each having a curved
elliptical tube, the ends of which are connected by a series of iron
rods, forming a catenary curve like that of a suspension bridge. To
these chains, and also to the curved tubes, the platform bearing the
rails is suspended by vertical suspension bars, and the whole is
connected by struts and ties so nicely adjusted as to distribute the
strains produced by the load with the most beautiful precision. When the
bridge was tested, a train formed wholly of locomotives, placed upon the
entire length of the span, produced a deflection in the centre of 7 in.
only. This bridge has sometimes been called a suspension bridge because
of the flexible chords which connect the ends of the bows; but this
circumstance does not in reality bring the bridge as a whole under the
suspension principle. The section of the bow-shaped tube is an ellipse,
of which the horizontal diameter is 16 ft. 10 in. and the vertical
diameter 12 ft., and the rise in the centre about 30 ft. Beside the two
fine spans which overleap the river, the bridge is prolonged on each
side by a number of piers, on which rest ordinary girders, making its
total length 2,240 ft., or nearly half a mile; 2,700 tons of iron were
used in the construction. As in the case of the Britannia Bridge, the
tubes were floated to the piers, and then raised by hydraulic pressure
to their position 150 ft. above the level of the water. The bridge was
opened by the late Prince Consort in 1860, and has received the name of
the Albert Bridge.


                         _SUSPENSION BRIDGES._

The general principle of the suspension bridge is exemplified in a chain
hanging between two fixed points on the same level. If two chains were
placed parallel to each other, a roadway for a bridge might be formed by
laying planks across the chains, but there would necessarily be a steep
descent to the centre and a steep ascent on the other side. And it would
be quite impossible by any amount of force to stretch the chains into a
straight line, for their weight would always produce a considerable
deflection. Indeed, even a short piece of thin cord cannot be stretched
horizontally into a perfectly straight line. It was, therefore, a happy
thought which occurred to some one, to hang a roadway from the chains,
so that it might be quite level, although they preserved the necessary
curve. In designing such bridges, the engineer considers the platform or
roadway as itself constituting part of the chain, and adjusts the loads
in such a manner that the whole shall be in equilibrium, so that if the
platform were cut into sections, the level of the road would not be
impaired.

Public attention was first strongly drawn to suspension bridges by the
engineer Telford, who, in 1818, undertook to throw such a bridge across
the Menai Straits, and the work was actually commenced in the following
year. The Menai Straits Suspension Bridge has been so often described,
that it will be unnecessary to enter here into a lengthy account of it,
especially as space must be reserved for some description of other
bridges of greater spans. The total length of this bridge is 1,710 ft.
The piers are built of grey Anglesea marble, and rise 153 ft. above the
high-water line. The distance between their centres is 579 ft. 10½ in.,
and the centres of the main chains which depend from them are 43 ft.
below the line joining the points of suspension. The roadway is 102 ft.
above the high-water level, and it has a breadth of 28 ft., divided into
two carriage-ways separated by a foot-track. The chains are formed of
flat wrought iron bars, 9 ft. long, 3¼ in. broad, and 1 in. thick. In
the main chains, of which there are sixteen, no fewer than eighty such
bars are found at any point of the cross section, for each link is
formed of five bars. These bars are joined by cross-bolts 3 in. in
diameter. The main chains are connected by eight transverse stays formed
of cast iron tubes, through which pass wrought iron bolts, and there are
also diagonal ties joining the ends of the transverse stays. The time
occupied in the construction was 6½ years, and the cost was £120,000.
This bridge has always been regarded with interest for being the first
example of a bridge on the suspension principle carried out on the large
scale, and also for its great utility to the public, who, instead of the
hazardous passage over an often stormy strait, have now the advantage of
a safe and level roadway.

[Illustration:

  FIG. 146.—_Clifton Suspension Bridge, near Bristol._
]

The Clifton Suspension Bridge over the Avon, near Bristol, is noted for
having a wider span than any other bridge in Great Britain, and it is
remarkable also for the great height of its roadway. The distance
between the centres of the piers—that is, the distance of the points
between which the chains are suspended—is more than 702 ft. Part of the
ironwork for this bridge was supplied from the materials of a suspension
bridge which formerly crossed the Thames at London, and was removed to
make room for the structure which now carries the railway over the river
to the Charing Cross terminus. Five hundred additional tons of ironwork
were used in the construction of the Clifton Bridge, which is not only
much longer than the old Hungerford Bridge, but has its platform of more
than double the width, viz., 31 ft. wide, instead of 14 ft. A view of
this bridge is given in Fig. 146, where its platform is seen stretching
from one precipitous bank of the rocky Avon to the other, and the river
placidly flowing more than 200 ft. below the roadway. The picturesque
surroundings of this elegant structure greatly enhance its appearance,
and the view looking south from the centre of the bridge itself is
greatly admired, although the position may be at first a little trying
to a spectator with weak nerves. The work is also of great public
convenience, as it affords the inhabitants of the elevated grounds about
Clifton a direct communication between Gloucestershire and
Somersetshire, thus avoiding the circuitous route through Bristol, which
was required before the completion of the bridge.

[Illustration:

  FIG. 147.
]

The use of iron wire instead of wrought bars has enabled engineers to
far exceed the spans of the bridges already described. The table on page
199 shows that iron wire has a tenacity nearly one-third greater than
that of iron bars, and this property has been taken advantage of in the
suspension bridge which M. Chaley has thrown over the valley at
Fribourg, in Switzerland. This bridge has a span of no less than 880
ft., and is constructed entirely of iron wires scarcely more than ⅒ in.
in diameter. The main suspension cables, of which there are two on each
side, are formed of 1,056 threads of wire, and have a circular section
of 5½ in. diameter. The length of each cable is 1,228 ft., and at
intervals of 2 ft. the wires are firmly bound together, so as to
preserve its circular form. But as the cable approaches the piers, the
wires are separated, and the two cables on each side unite by the
spreading out of the wires into one flat band of parallel wire, which
passes over the rollers at the top of the piers, and is again divided
into eight smaller cables, which are securely moored to the ground. Each
of the mooring cables is 4 in. in diameter, and is composed of 528
wires. In order to obtain a secure attachment for the mooring cables,
shafts were sunk in the solid rock 52 ft. deep, and the ingenious mode
in which, by means of inverted arches, an anchorage in the solid rock is
formed for the cables, will be understood by a reference to Fig. 147.
The cables pass downwards through an opening made in each of the middle
stones, and are secured at the bottom by stirrup-irons and keys. The
suspension piers are built of blocks of stone, very carefully shaped and
put together with cramps and ties, so as to constitute most substantial
structures. These piers are embellished with columns and entablatures,
forming Doric porticoes, enclosing the entrances to the bridge, which
are archways 43 ft. high and 19 ft. wide. The roadway is 21 ft. wide,
and is supported on transverse beams, 5 ft. apart, upon which is laid
longitudinal planking covered by transverse planking. The roadway beams
are suspended to the main cables by vertical wire cables, 1 in. in
diameter. The length of these suspension cables of course varies
according to their position, the shortest being ½ ft. and the longest 54
ft. in length. Each suspension cable is secured by the doubling back of
the wires over a kind of stirrup, through which passes a plate of iron,
supported by the two suspension cables, the latter being close together,
and, indeed, only separated by the thickness of the suspension cables,
which hang between them. The roadway has a slight rise towards the
centre, its middle point being from 20 to 40 in. above the level of the
ends, according to the temperature.

To test the stability of the bridge, fifteen heavy pieces of artillery,
accompanied by fifty horses and 300 people, were made to traverse it at
various speeds, and the results were entirely satisfactory. Indeed, a
few years afterwards the people of Fribourg had another wire bridge
thrown over the gorge of Gotteron, at about a mile from the former.
This, though not so long (640 ft.), spans the chasm at a great height,
and in this respect is probably not surpassed by any bridge in the
world—certainly not by any the length of which can compare with its own.
The height of the roadway above the valley is 317 ft., or about the same
as that of the golden gallery of St. Paul’s Cathedral above the street.
The structure is very light, and the sensation experienced when, looking
_vertically_ downwards through the spaces between the flooring boards,
you see the people below diminished to the apparent size of flies, and
actually feel yourself suspended in mid-air, is very peculiar, as the
writer can testify.

The Americans have, however, outspanned all the rest of the world in
their wire suspension bridges. They have thrown a suspension bridge of
800 ft. span over the Niagara at a height of 260 ft. above the water, to
carry not only a roadway for ordinary traffic, but a railway. Suspension
bridges are not well adapted for the latter purpose, but there seemed no
other solution of the problem possible under the circumstances. The
bridge, however, combines to a certain extent the girder with the
suspension principle. The girder which _hangs_ from the main cables (for
they are made of wire), carries the railway, and below this is the
suspended roadway for passengers and ordinary carriages. The engineer of
this work was Roebling, who also designed many other suspension bridges
in America.

The spans of any European bridges are far exceeded by that of the wire
suspension bridge which crosses the Ohio River at Cincinnati, with a
stride of more than 1,000 ft.; and this is, in its turn, surpassed by
another bridge which has been thrown over the Niagara. This bridge,
which must not be confounded with the one mentioned above, or with the
Clifton Bridge in England already described, merits a detailed
description from the audacity of its span, which is nearly a quarter of
a mile, and entitles it to the distinction of being the longest bridge
in the world of one span.

[Illustration:

  FIG. 147_a_.—_Clifton Suspension Bridge, Niagara._
]

The new suspension bridge at the Niagara Falls, called the Clifton
Bridge, of which a view is given in Fig. 147_a_, is intended for the use
of passengers and carriages visiting the Falls, and it is also the means
of more direct communication between several small towns near the banks
of the river. The bridge is situated a short distance below the Falls,
crossing the river at right angles to its course at a point where the
rocks which form the banks are about 1,200 ft. apart. The distance
between the centres of the towers is 1,268 ft. 4 in., and the bridge has
by far the longest single span of any bridge in the world, the distance
between the points of suspension being more than twice that of the Menai
Bridge, and more than six times the span of the widest stone bridge in
England. This remarkable suspension bridge was constructed by Mr. Samuel
Keefer, and was opened for traffic on the 1st of January, 1869, the
actual time employed in the work having been only twelve months. The
cables and suspenders are made of wire, which was drawn in England at
Warrington and Manchester, and the wires for the main cables were made
of such a length, that each wire passed from end to end of the cable
without weld or splice. The length of each of the two main cables is
1,888 ft., and of this length 1,286 ft. usually hangs between the
suspending towers, the centre being about 90 ft. below the level of the
points of suspension. This last distance, however, varies considerably
with the temperature, for in winter the contraction produced by the cold
brings up the centre to 89 ft. below the level line, while in summer it
maybe 3 ft. lower. The centre of the bridge is about 190 ft. above the
water in summer, and 193 ft. in winter. The cables are each formed of
seven wire ropes, and each rope consists of seven strands, each strand
containing nineteen No. 9 Birmingham gauge wires of the diameter of
0·155 in. The cables of this bridge do not hang in vertical planes,
since in the centre they are only 12 ft. apart; while at the towers,
where they pass over the suspension rollers, they are 42 ft. apart. The
end of the platform which rests on the right bank is 5 ft. higher than
the other, and if a straight line were drawn from one end to the other,
the centre of the roadway would be in winter 7 ft. above it, and in
summer 4 ft. From each point of suspension twelve wire ropes, called
“stays,” pass directly to certain points of the platform. The stays are
not attached to the cables, but pass over rollers on the tops of the
towers, and are anchored in the rock, independently of the cables. The
longest stays are tangential to the curve formed by the main cables, and
they are fixed to the platform at a point about half-way to the centre.
Other stays proceed from the platform at intervals of 25 ft., between
the longest and the end of the bridge. The thickness of the stays is
varied according to the strain they have to bear, and they form not only
a great additional support to the platform, but they also serve to
stiffen the bridge and lessen the horizontal oscillations to which the
platform would be liable from the shifting loads it has to bear. There
are also stays which transversely connect the two cables. The wire ropes
by which the platform is suspended to the main cables are ⅝ths of an
inch in diameter, and have such a strength that the material would only
yield to a strain of 10 tons. These suspenders are placed 5 ft. apart
and are 480 in number, the lengths, of course, being different according
to the position. To each pair of suspenders is attached a transverse
beam, 13½ ft. long, 10 in. deep, and 2½ in. wide. Upon these beams—which
are, of course, 5 ft. apart from centre to centre—rests the flooring,
formed of two layers of pine planking 1½ in. thick; and the roadway thus
formed constitutes a single track 10 ft. in width. Along each side of
the platform is a truss the whole length of the bridge, formed of an
upper and a lower beam, 6½ ft. apart, united by ties and diagonal
pieces. The lower chord of the truss is 2 ft. below the road, and on it
rolled iron bars are bolted continuously from one end of the bridge to
the other. The last arrangement contributes greatly to stiffen the
platform, vertically and horizontally. In the central part of the bridge
the flooring-boards are bolted up to the cables, and there are studs
formed of 2 in. iron tubes, so that the platform cannot be lifted
vertically without raising the cables also; and as thus 81 tons of the
weight of the cables vertically rest upon the platform, great steadiness
is secured, inasmuch as the central part of the cables must partake of
any movement of the platform, and their weight greatly increases the
inertia to be overcome. In order still further to prevent oscillations
as much as possible, a number of “guys” are attached to the bridge.
These are wire ropes of the same thickness as the suspenders, and they
connect the platform with various points of the bank—some going
horizontally to the summit of the cliffs, others vertically, but the
majority obliquely. There are twenty-eight guys on the side of the
bridge next the falls, and twenty-six on the other side. The thickness
of the wire rope of which they are made being little more than ½ in.,
they are scarcely visible, or rather appear like spider lines. About 400
ft. of the length of the bridge in the centre is without either guys or
stays except two small steel ropes, which, tightly strained from cliff
to cliff, cross each other nearly at right angles at the centre of the
bridge. The suspension towers are pyramidal in form and are built of
white pine, the timbers being a foot square in section and very solidly
put together, so that they are capable of bearing forty times the load
which can ever be put upon them. The towers are surmounted by strong
frames of cast iron, to which are fixed the rollers carrying the cables
and stays to their anchorage. The weight of the bridge itself, together
with the greatest load it can be required to bear, amounts to 363 tons.
Its cost was £22,000, and it was constructed without a single accident
of any kind.

The foam of the great falls is carried by the stream beneath the bridge,
and in sunshine the spectator who places himself on the centre of its
platform sees in the spray driven by the wind, not a mere fragment of a
rainbow, or a semicircular arc, but the complete circle, half of which
appears beneath his feet. The gorge of the Niagara is very liable to
furious blasts of winds, for by its conformation it seems to gather the
aërial currents into a focus, so that a gentle breeze passing over the
surrounding country is here converted into a strong gale, sweeping down
with great force between the precipitous banks of the river. Indeed, one
would suppose that the cavern from which Æolus allows the winds to rush
out, must be situated near Niagara Falls. The bridge is not disturbed by
ordinary winds, although during its construction, before the stays and
guys were fixed, it was subject to considerable displacement from this
cause. The peculiar arrangement of the cables, by which they hang, not
vertically, but widening out from the centre of the bridge, giving what
has been termed the “cradle” form, has proved of the highest advantage,
so that, with the aid of the guys and stays, and the plan of attaching
the central part of the roadway to the cables, the bridge is believed to
be capable of withstanding without damage a gale having the force of 30
lbs. per square foot, although its total pressure on the structure might
then amount to more than 100 tons. The stability of the structure was
severely tested soon after its erection by a furious gale from the
south-west, by which the guys were severely strained; in fact, many of
them gave way. In one case an enormous block of stone, 32 tons in
weight, to which one of the guys was moored, was dragged up and moved 10
ft. nearer the bridge. This and some lateral distortion of the platform,
which was easily remedied, was all the damage sustained by the bridge.
By an increase of the strength of the guys, &c., and the addition of the
two diagonal steel wire ropes mentioned above, the bridge was soon made
stronger than before. Some years ago, when the Menai suspension bridge
was exposed to a storm of like severity, that structure suffered great
damage, the platform having been broken and some of it swept away. In
the great gale which swept down upon the Niagara bridge, although the
force of the wind was so great that passengers and carriages could not
make headway, the vertical oscillations of the bridge never exceeded 18
in., an amount which must be considered extremely satisfactory in a
bridge of the kind, having a span of nearly a quarter of a mile.[4]

Footnote 4:

  Notwithstanding the skill displayed in its construction, this bridge
  has, since the above account was written, been destroyed by a
  tremendous hurricane.

[Illustration:

  FIG. 147_b_.—_Living Model of the Cantilever Principle._
]


                         _CANTILEVER BRIDGES._

The great Forth Bridge, now (December, 1889) approaching completion, is
the first bridge on the cantilever and central girder principle that has
been erected in Great Britain, and it has also the distinction of being
by far the widest spanned bridge in all the world. We are told by the
engineers of the bridge that the cantilever and girder principle is by
no means new, for it has been adopted hundreds of years ago by
comparatively rude tribes in the construction of timber bridges, to
which it readily lends itself. Such bridges are described as having been
erected by the natives of Hindoostan, Canada, Thibet, etc., even at
remote periods. The principle of the cantilever and girder construction
was well illustrated by Mr. Baker, one of the engineers of the bridge,
at a lecture given by him at the Royal Institution, by means of what he
termed “a living model,” of which (Fig. 147_b_) shows the general
arrangement. Two men, seated on chairs, extend their arms and hold in
their hands sticks, of which the other ends butt against the chairs. The
central girder is represented by a shorter stick, suspended at _a_ and
_b_. We have here the representation of two double cantilevers, the
ropes at _c_ and _d_, connected with the weights, representing the
anchorages of the landward arms of the cantilevers. When a weight is
placed on _a b_, which was done in the “living model,” by a third man
seating himself thereon, a tensile strain comes into action in the ropes
and in the men’s arms, while the sticks abutting on the chairs have to
resist a compressing force, and the weight of the whole is borne by the
legs of the chairs, also under compression. Now let the reader imagine
the men’s heads to be 360 feet above the ground, and about a third of a
mile apart, while the distance between _a_ and _b_ is 350 feet, and he
will have a rough but sufficiently clear idea, not only of the principle
upon which the Forth Bridge is constructed, but also of the magnitude of
one of its spans. To complete the comparison, Mr. Baker further invited
his hearers to suppose that the pull upon each arm of the men is equal
to 10,000 tons, and that the legs of each chair press on the ground with
the weight of more than 100,000 tons.

The Forth Bridge spans the estuary at Queensferry nine miles north-west
from Edinburgh, and its purpose is to afford uninterrupted railway
communication along the eastern side of Scotland. It will, in effect,
shorten the railway journey between Edinburgh and Perth, or Aberdeen, by
nearly two hours. Queensferry had long been established as a usual place
for crossing the Forth, and readers of Scott’s “Antiquary” will remember
that the first chapter describes how Monkbarns and Lovel, by some
accidental delays to the coach, lost the tide, and had to wait, to sail
“with the tide of ebb and the evening breeze,” finding themselves, in
the meanwhile, pretty comfortable over a good dinner at the “Hawes Inn.”
This inn still stands, its situation being close to the southern end of
the great bridge. A design for the erection of a light suspension bridge
at the same spot was published at the beginning of the present century,
but although the spans were to be equal to those of the present bridge
(17,000 feet), the different scale of the projects may be inferred from
the total weight of iron to be used being estimated at 200 tons, while
50,000 tons will be required for the structure now approaching
completion.

In 1873, an Act of Parliament was obtained authorizing the construction
of a suspension bridge at Queensferry, to carry the railway over the
estuary. The design comprised practically two bridges, each carrying a
single line of rails, the bridges being braced together at intervals.
The central towers were to have been 600 feet high, or about 100 feet
loftier than any other erection then existing in the world. The designer
was the late Sir Thomas Bouch, and preparations were made for carrying
out the plans by the erection of workshops and the manufacture of bricks
for the piers. But the project was knocked on the head by the terrible
disaster at the Tay Bridge, in December, 1879, when several of the
central piers were overturned by the force of the wind, with swift
destruction to a passing train, which was precipitated into the water,
and every one of about ninety persons in the train perished. Sir Thomas
Bouch having been the designer of the Tay Bridge, public confidence in
his plan was shaken to such an extent, that the four railway companies
who were promoting the construction of the suspension bridge abandoned
the project in favour of a design on the cantilever and central girder
system, which was then brought forward by Mr. (now Sir John) Fowler and
Mr. Baker. When the Bessemer process had made steel attainable at a
cheap rate, these engineers recognized the advantages which cantilever
bridges, made of that material, presented for the wide spans required
for carrying railways across navigable rivers, and in 1865 they had
designed such a bridge, with 1,000 feet spans for a viaduct, across the
Severn, near the position of the present tunnel. It was not, however,
until 1881 that the designs for the Forth Bridge were published in
English and American engineering journals. These designs at once
attracted attention, and scarcely a year had elapsed before a railway
bridge was built for the Canadian and Pacific Railway, on the same
principle, and this has been followed by others since. It is, however,
absurd to allege that the engineers took their ideas from America,
merely because these smaller undertakings have been completed before the
great work that dwarfs them all was open for traffic. The construction
of the Forth Bridge on its present design was commenced in January,
1883. Its site at Queensferry is at a point where the estuary narrows,
and where, in the very middle of the channel, there is a small rocky
island, called Inchgarvie, that furnishes a solid foundation for the
great central pier. On each side of this island the channels are about
one-third of a mile wide, and more than 200 feet deep, and through them
the tide rushes with great velocity. The impossibility of building up
any intermediate piers, under such circumstances, is sufficiently
obvious—the currents must be crossed at one span, if a railway bridge
had to be made. The formation of the piers for such a work presented
many novel problems, and much of the work had to be commenced in deep
water; that is, the ground of rock or hard clay had to be prepared, in
some parts, as far as 90 feet below high water. Each pier stands on four
caissons, which are great tubes or drums of iron and steel, filled up
with concrete. Each weighed, when empty, about 400 tons, but when filled
up with concrete, the weight would be about 3,000 tons. The diameter of
each is 70 feet, and the deepest one is sunk 89 feet below the water,
and it was with no little labour that some of them were put in their
places. Each caisson has an outer and an inner tube, is 70 feet in
diameter at the base, and 60 feet at the top. Seven feet from the
bottom, an air-tight partition formed a chamber in the lower part of the
caisson, about 70 feet in diameter, by 7 feet high, and shafts
sufficiently large to admit the passage of men and tools led from the
top. Air was forced into this chamber, when the caisson had been sunk,
expelling the water, and then men descended through the shafts and
locks, in which a high pressure of air was also maintained, and
excavated the material at the bottom, until the caisson had, by its own
weight, sunk to the depth required. The work in this air chamber was
carried on by means of electric lights, and ten or twelve weeks were
occupied in sinking each caisson. The pressure of the air in the working
chamber was sometimes as high as 35 pounds per square inch, or
sufficient to maintain the mercurial column in a barometer 72 inches
high, instead of the ordinary 29 or 30 inches. It was found that the
labour in the compressed air chamber could not be done by our home
workmen, as they were quite unaccustomed to the high air pressures
required to keep out the water; but arrangements were made for the
assistance of a staff of French workmen, inured to the conditions by
long working under water in the construction of the docks at Antwerp.

[Illustration:

  PLATE XIII.

  THE FORTH BRIDGE.
]

The stores, offices and workshops, situated on a slight eminence near
the south end of the bridge, are very extensive, occupying, it is said,
an area of 50 acres. Here are great furnaces, cranes and machinery for
shaping and fitting the steel plates and bars ready for taking their
appointed places in the vast structure. An hydraulic crane may, for
instance, be seen lifting a ton weight flat steel plate that has been
heated to redness in a regenerative gas furnace, and transferring it to
an hydraulic press, where it is quickly and quietly bent to the required
shape. The plate is then cooled, and, when the edges have been planed,
it is placed in position with the adjoining plates, and the rivet holes
are drilled by an ingenious machine, specially designed by Mr. Arrol,
the contractor, for that purpose. It works upon 8–feet lengths of the
tubes, and simultaneously cuts ten rivet holes at different points in
the circumference. All the different parts of the structure are
temporarily fitted together to ascertain that every piece is properly
adjusted. They are then marked according to the position they are to
take, and are laid aside until they are wanted. Thus the work at the
bridge has proceeded without any awkward hitches arising from ill
adjusted sections being brought together. At times, 1,800 tons of
finished steel-work has been turned out of these shops in a month, and
this material, which was supplied by the Steel Company of Scotland, has
been found thoroughly trustworthy in every respect. Its strength is
one-half greater than that of the best wrought-iron, and the plates have
thrice the ductility of iron plates. The steel plates for the great
tubes are supplied in lengths of 16 feet, and of different thicknesses,
between ⅜ths of an inch and 1¼ inch.

[Illustration:

  FIG. 147_c_.—_Principal Dimensions of the Forth Bridge._
]

The sketch, Fig. 147 _c_, shows the general dimensions of the bridge
proper, or that part of the viaduct which will actually span the
estuary. Of the three great piers that support the cantilevers, it will
be observed that the central one, which rests on Inchgarvie, is wider
than the other two. Each consists mainly of four tubes, 12 feet in
diameter, made of plates of steel 1¼ inch in thickness, and these rise
to the highest part of the bridge, which is 361 feet above the water, so
that the structure is as lofty as St. Paul’s Cathedral. These great
tubes are not placed vertically, but incline inwards towards the top, so
that while the “straddle legs” of each pair are 120 feet apart at the
base, they are only 33 feet apart at the top. These lofty columns are
also braced together diagonally by other steel tubes—that is, a tube
passes from the foot of every column to each of the other three. At the
base of each column, the lowest spanning member springs also (which
appears like an arch, but is not so), as a tube of 12 feet diameter.
Thus abutting or resting on enormously thick plates of steel that cap
the masonry of each pier, are five tubular steel limbs, three of which
are 12 feet in diameter, and two are 8 feet, and, besides these five,
girder members diverge from nearly the same centre. One of the large
tubular members is the first strut that rises obliquely to support the
upper structure. From the point where this strut meets the upper member,
a stay passes downwards with an opposite inclination to the lower
member, from its point of junction with which another strut rises, and
so on. All the struts, as being subject to compressing force, are made
of steel tubes; the straight upper members and the stays are lattice
braced girders of rectangular section. The apparent curve of the lower
member—for it is really made up of sections of straight tubes—may
suggest the notion of an arch; but the reader must remember that the
principle of this bridge has no relation to that of the arch. The
cantilevers do not unite the long arms they stretch, but each is an
independent structure with its own perfect stability, and it will not be
clutched on or locked up to its neighbours by the central girders. The
weight of one of these 1,700 feet spans is about 16,000 tons, and the
heaviest train loads might be two coal trains, weighing together, say
800 tons, or only one-twentieth of the dead weight of the structure.
But, what would not generally be supposed, the pressure of the wind is
an element of much more importance in considering the stability of the
bridge than the weight of the rolling load. It is to resist the wind
pressure that the lofty columns that are only 33 feet apart at the top
across the bridge, plant their bases 120 feet asunder. The estimated
lateral pressure of the wind on one of the cantilevers, assuming it as
equal to 56 lbs. per square foot, would amount to 2,000 tons. These
strains are so fully provided for that the engineers are confident that
a hurricane of such a force as would desolate the country would leave
the Forth Bridge intact, even if the wind blew in opposite directions on
the two arms of the cantilever. To rend asunder the top ties, a pull
equivalent to the weight of 45,000 tons would be required, whilst the
utmost strain that passing trains could possibly bring upon these ties
would be less than 2,000 tons. A striking illustration of the strength
of these huge brackets was lately given by Mr. Baker himself, when in a
public lecture he assured his audience that half a dozen of our
ponderous modern ironclads might be hung from the cantilevers. Everyone
knows that a bracket requires to be strongest nearest the base, and the
lower steel arms that stretch out 680 feet each diminish in diameter
until at the end it has decreased to five feet, and the pairs approach
each until, from being 120 feet apart at the base, they are only 33 feet
apart at the ends. The central girders will each weigh about 1,000 tons,
and only one end of each will be attached to a cantilever, the other
ends will simply rest on what are called “rocking columns,” so that
there may be freedom of motion to allow play for the changes of position
that will be induced by changes of temperature expanding or contracting
the huge masses of metal.

The reader can hardly have failed to observe that the chief element in
the stability of the structure depends upon balancing a great mass of
metal on the one side of a pier by an equal mass on the other side. But
while each end of the central cantilever bears half the weight of a
central girder, the two shoreward cantilevers have this load at their
inner ends only. How is their balance maintained? In this way: the
shoreward arms are made about 10 feet longer than those that stretch
over the water and their extremities are also loaded with about 1,000
tons of iron, built up within the shore piers.

The lofty columns of the piers were erected without any external
staging, from a temporary platform surrounding the piers and supporting
the necessary machinery. The weight of this platform with the machinery
on it was about 400 tons, and as the work proceeded it was raised as
required by hydraulic machines placed within the vertical columns. As
the height of these increased, the men and materials had to be conveyed
to the platform by cages moving between guide ropes and worked by steam
engines. From this platform were constructed not only the main columns,
but the great diagonal tubes, the bracing girders, and the viaduct
girder. The cantilevers were also put together without scaffolding. When
the first few feet of the lower member had been built out from the base,
a movable platform was hung round it, and on this platform were the
cranes for putting the plates into position, the furnace for heating the
rivets, and the hydraulic riveter of specially designed construction,
without noise or hammering, the riveting being completed by the
application of a pressure equal to 3 tons per square inch. The building
up of the cantilever arms on either side of each pier always proceeded
at the same rate, so that the balance was constantly maintained. This
building out from each side of the pier, without the necessity of
relying upon any temporary scaffolding from below, is one great
advantage of the cantilever system, as it is both easier and safer than
a system which relies upon the temporary scaffolding raised from below.
The Forth is for the time the longest spanned bridge in the world; but
it may not retain that honour long, for the legislature of the United
States has already authorized the construction of a cantilever bridge,
the spans of which are to be 2,480 feet. Still more gigantic is the
project lately put forward by some competent French engineers of
bridging the English Channel from Folkestone to Cape Grisnez in 70 spans
on the cantilever system. The designs have been completed and the
calculations made, and no one doubts of the engineering practicability
of the scheme. But the cost is estimated at about 34 million pounds
sterling, or nearly six times as much as that required for constructing
the proposed Channel Tunnel; so that the scale could be turned in favour
of the bridge only if the political reasons that were opposed to the
tunnel were held not to be applicable to the bridge. But it is difficult
to conceive that the existing traffic could ever be developed to such an
extent as to make an undertaking of this magnitude a commercial success.

Since the above account was written, the Forth Bridge was formally
opened on the 4th March, 1890, by the Prince of Wales, in the presence
of a great gathering of railway directors, eminent engineers, and other
distinguished persons from all parts. A very strong gale was blowing at
the time, and at this very hour the bridge was therefore subjected to
another severe but undesigned test of its stability. The perfect
steadiness and security of the structure impressed all who were present
on that occasion, and the train crossed the bridge, exposed to a wind
pressure, registered by the gauge, of 25 lbs. per square foot. At the
luncheon following the opening ceremony, the Prince announced that
baronetcies had been conferred upon Mr M. W. Thompson (the chairman of
the Bridge Company) and upon Sir John Fowler, and that Mr. Baker and Mr.
Arrol, the contractor for the works, were to be knighted. Sir John
Fowler, the engineer-in-chief, was born in 1817, and has been engaged in
many other important works of railway construction in Yorkshire, in that
of the London and Brighton Railway, in the Sheffield Waterworks, &c. The
Metropolitan Railway in London, which also was carried out by Sir John
Fowler, would alone suffice to make him famous as an engineer. Sir
Benjamin Baker is a much younger man, who has had a large and varied
practice in railway engineering in various parts of the world. He is in
much request on the American continent, and is now engaged in carrying
out a ship railway in Canada and a tunnel under the Hudson at New York.
Sir William Arrol began life at nine years of age as a “piecer” in a
cotton mill, but was afterwards apprenticed as an engineer. Subsequently
he was employed as a foreman by engineering firms in Glasgow. In 1866,
he began business on his own account at Dalmarnock, and obtained
contracts at first for smaller then for larger works connected with
bridge and viaduct building. He is distinguished for the energy and
inventive resources he displays in carrying out his undertakings.


                      _THE TOWER BRIDGE, LONDON._

A little more than four years after the opening of the Forth Bridge, in
June 1894, another great enterprise which had been commenced eight years
before, was inaugurated by the Prince and Princess of Wales as
representatives of Her Majesty the Queen. This was the Tower Bridge,
which not only is one of the most important public works of the century,
but one that presents features of interest and novelty that have never
before been combined in any single structure. The want of an adequate
communication between the shores of the Thames eastward of London Bridge
had long been felt, and was for years a subject of serious consideration
for the Metropolitan authorities. The congested state of the traffic
across London Bridge has often furnished a spectacle for the sight-seer,
and figures are not wanting to show that the number of foot-passengers
alone who daily traverse that bridge, which altogether is only 54 feet
wide, would be equal to the whole population of many considerable
cities: for in 1882 a count showed the daily average of pedestrians to
be 110,525, while the number of vehicles was 22,242. There was much
difference of opinion as to the best method of providing the required
means of communication; but there was an almost universal agreement as
to its position being selected just eastward of the Tower of London. The
map of the districts connected by the Tower Bridge which is given in
Fig. 147_d_, will show a reader who has any acquaintance with London the
suitability of the site. The problem of traversing the river at this
point involved complex conditions as affecting the vehicular traffic and
the navigation, and many different schemes were proposed and examined,
comprised under the three heads of bridges, tunnels and ferries. But a
ferry is always an imperfect means of communication, liable to accidents
and interruptions from fogs, and in severe weather from ice, rendering
the transit impossible for sometimes many days together. A tunnel
beneath the river would, of course, leave the navigation without
impediment, but among its special disadvantages are the great expense of
construction and maintenance, for it has been found that tunnels beneath
waterways are very costly in both respects. Besides, there would have to
be long inclined approaches at each end, and the cost would be
enormously increased by the amount of valuable land these would occupy.
It was indeed proposed that the tunnel should be provided instead with
hydraulic lifts at each end, like those often found in connection with
the sub-ways at railway stations; but such would have to be of
Brobdignagian dimensions, and would daily entail heavy expense. Then, as
regards the bridges, schemes of various kinds were proposed, some even
bridging the whole 850 feet width of the river at a single span, but all
distinguishable by these important characteristics: they either provided
a high level roadway which requires long inclines to reach it, but
permitted lofty-masted ships to pass under it; or, on the other hand,
the roadway was to be made at a low level with a clear headway above the
water of moderate height. While avoiding the inclined approaches, this
plan would either prevent fully rigged vessels passing to the wharves
above the bridge, or some part of the structure would have to open or
swing aside, that the ships might pass through the opening, thus
completely interrupting the pedestrian and vehicular traffic for the
time, with an amount of inconvenience that may be imagined when, as
often happens, twenty large ships or more might pass in the course of a
day, each causing a stoppage of five minutes in the road traffic. Nor
would it be without risks that large vessels could pass through a
comparatively narrow opening in a strong tide-way. Plans for sub-ways,
for high level roadways and for low level roadways, were examined by
Parliamentary Committees when powers to construct the works were
successively applied for by the Metropolitan authorities, and much
valuable evidence having been given, such objectionable features of each
scheme as have been already referred to were duly noted. At length in
1878, Mr. Horace Jones, the late architect to the City of London, in a
report on the various projects, suggested the general plan on which the
present bridge is built, and this having been approved of by the Common
Council, steps were taken to obtain Parliamentary powers to raise the
necessary capital and to proceed with the works; but, for various
reasons, it was not until 1885 that the Act authorising the undertaking
was passed. In the meantime Mr. John Wolfe Barry was appointed engineer
of the structure, while Mr. Jones was to superintend the architectural
details; but after having received the honour of knighthood in 1885, he
died in the same year; and Mr. Barry, reconsidering the joint design,
introduced some new features and somewhat modified the architectural
expression of the structure. One striking point of originality about the
Tower Bridge is that while it is essentially an iron and steel
construction as much as the Forth Bridge, the heavy stiff metal-work is
encased in masonry of elegant and appropriate architectural design, by
which the general desire that the bridge should harmonize so far as
might be, with the ancient historical fortress it adjoins, has been
happily realised. Then again, by the ingenious engineering, the public
have the advantage of a low level roadway, while the largest vessels may
pass freely through a wide space without risk. These apparently
incompatible advantages have been obtained by the adoption of what is
the _bascule_ principle on a hitherto unattempted scale. _Bascule_ is a
French engineering term, which is probably less familiar to most of our
readers than the thing itself. It is applied to the platform of a
draw-bridge which turns as the lid of a box does on its hinges, to
afford a passage over the stream or moat when it is horizontal, and when
drawn up vertically denies such passage. Smaller _bascule_ bridges on
exactly the same plan as in the Tower Bridge may often be seen in places
having docks or canals, such as Hull, &c. In these a flap or platform is
let down from each side from the vertical position, in which the
water-way is open until the free edges meet together to form the
roadway. These platforms turn on horizontal pivots, and are
counterpoised by loads of stone or metal, so that they are without
difficulty raised and lowered by a winch or handle that turns a cogged
pinion engaging the teeth of a large quadrant.

[Illustration:

  PLATE XIV.

  THE TOWER BRIDGE IN COURSE OF CONSTRUCTION.
]

[Illustration:

  “THE ENGINEER”      SWAIN ENG.

  FIG. 147_d_.—_Map of the Tower Bridge and its Approaches._
]

The following general description of the Tower Bridge is mainly
abstracted from a very full and excellent account of it drawn up in 1894
by Mr. J. E. Tuit, engineer to Sir W. Arrol & Co., the contractors, in
which are embraced the whole of the technical details of the structure.
The map, Fig. 147_d_, shows the site of the bridge and its approaches,
of which the northern one begins close to the mint and passes along the
east side of the Tower of London to the northern abutment. This approach
is formed of a series of brick arches, and is nearly 1,000 feet long and
35 feet wide in the roadway, with a footpath 12½ feet wide on either
side of it. The incline is only a rise of 1 in 60, but the southern
approach is slightly steeper, namely, 1 in 40 leaving the street level
at Tooley Street. At each abutment there are also stairs connecting the
banks of the river with the roadway of the bridge. The width of the
river between the two abutments is 880 feet, and this is divided, as
shown in Fig. 147_e_, into two side spans, each 270 feet wide, and one
central span of 200 feet clear, making together 740 feet, the river
piers, each of which is 70 feet wide, completing the total span. The
clear headway above high water, when the _bascules_ or leaves are down,
is, in the middle span, 29½ feet in the centre, but only 15 feet at the
ends; but when the leaves are raised for ships to pass, it is about 143
feet. The headway at the shore sides of the piers is 27 feet, but this
is lessened to 23 feet and 20 feet at the north and south abutments
respectively. The roadway and footpaths are continued along the side
spans of the same width as on the approaches, but over the central span
the road is 32 feet, and each footway 8½ feet wide. The river piers are
said to be the largest in the world of the same kind, and their great
area was necessitated by the nature of the London clay on which they
rest, which was found incapable of bearing a load much exceeding four
tons per square foot without some risk of undue settlement.

The part of the piers below the bed of the river is formed of concrete,
while the upper part is brickwork, set in cement and faced with Cornish
granite. Upon each of the river piers rest four octagonal columns, built
up of flat steel plates, connected together at their edges by splayed
angle-bars. The columns are 120 feet high, and 5½ feet in diameter;
those on each pier are securely braced together, at certain stages also
by plate girders, 6 feet deep, to form a floor or landing, and the tops
of the columns are similarly joined together. At the height of 143 feet
above high water there are two footways, each 12 feet wide and 230 feet
long, carried on girders over the central span, and supported by the
columns on each pier. It must be noted that all the roadway, and, in
fact, all the practical and useful structure of the bridge, depend upon
the steel-work alone, which is supported mainly by the eight octagonal
columns just mentioned. The architectural features, which so
appropriately clothe all the steel columns, are added for æsthetic
considerations, and their masonry takes no part in bearing the weights
and strains of the structure. Indeed, the stone-work of the towers is
carefully separated from the columns, which were covered with canvas
while the masonry was built round them, and spaces were left at every
point where compression of the steel-work would bring weight upon the
stone-work. This investment of the metal-work by beautiful architecture
is, as already mentioned, one of the most original features of the Tower
Bridge. The view of the work in progress, as given in Plate VIII., which
is one of the many beautiful illustrations in Mr. Tuit’s book, will give
the reader an opportunity of judging how much the structure gains in
sightliness by the addition of the architectural features. Two hydraulic
lifts are placed in each tower to convey pedestrians to and from the
higher level footways, when the moving parts of the bridge are open, and
stairs also are provided for the same purpose for those who prefer them
to using the lifts.

[Illustration:

  FIG. 147_e._—_The Tower Bridge._
]

 Length of Bridge with its approaches                         2680 feet.

 Length of Northern approach                                  1000 feet.

 Length of Southern approach                                   800 feet.

 Width between N. and S. abutments                             830 feet.

 Width of central span                                         200 feet.

 Width of side spans, each                                     270 feet.

 Depth of River at high water under central span               33½ feet.

 Depth of River at lowest tides under central span              12 feet.

 Clear headway at high water when the leaves are down (varies 20 to 29½
   from one part of the bridge to another)                    feet.

 Clear headway in centre span at high water with the leaves    143 feet.
   raised

The side spans are really suspension bridges, but the chains have only
two links, connected at the lowest point by a pin 2½ feet in diameter,
while their higher ends are supported on the columns of the piers, and
on similar but shorter columns on the abutments. The horizontal pulls of
the chains on the piers are made to balance each other by connecting the
chains to tie bars stretching across the central span, and the landward
ends of the chains, after passing over the lower columns of the
abutments, are securely anchored in enormous masses of concrete.

Each of the opening parts, or _bascules_, or leaves, as they may be
called, consists of four girders 18½ feet apart, rigidly braced
together, and connected at the pier end with a great shaft, 48 feet long
and 1 foot 9 inches in diameter, which turns in massive bearings,
resting upon four fixed girders. The leaf is counterbalanced on the
shore side of the pivot shaft by 350 tons of lead and iron; the short
leverage of the centre-weight and small space available for it required
the greater part of this weight to be of lead, rather than of the less
expensive metal. The pivot shaft passes through the centre of gravity of
the whole, so that, although the total weight is nearly 1,200 tons, no
very great power is required to set it in motion, as the pivot shaft
rests on rollers to diminish the friction. The power for moving the leaf
is applied to toothed quadrants of 42 feet radius, of which two are
fixed to the outside girders of each leaf, and are geared into cogs
moved by eight large hydraulic engines, with six accumulators, into
which water is pumped by two engines, each of 360 horse-power.

The total length of the bridge, including the approaches, is just half a
mile, and the height of the towers from the foundations is 293 feet, so
that if one of them were placed beside St. Paul’s Cathedral, it would
compare with it in height as shown in the sketch, Fig. 147_f_.

[Illustration:

  FIG. 147_f_.—_Sketch._
]


                      _THE GREAT BROOKLYN BRIDGE._

The Clifton Bridge at Niagara Falls, which for a time had the
distinction of being the longest in span of any suspension bridge in the
world, has been fully described in previous pages; but more recently
this bridge has been surpassed in span, and in all other respects, by a
structure that immediately connects two of the most populous localities
in the United States of America. The Island of Manhattan, which is
occupied by the city of New York proper, has a population of nearly two
millions, and a strait on its eastern side, connecting Long Island Sound
with New York Harbour, alone divides it from the other great seats of
population, called respectively Long Island City and Brooklyn. This
channel is about ten miles long, and of a varying width, which may
average three-quarters of a mile. There are many ferries between the
opposite shores, and the waters are busy with steamers, sailing-boats,
tugs, and craft of all kinds, engaged either in traffic with ports near
at hand, or in trade with distant lands. At the southern end of this
strait, near the point of its junction with New York Bay, is the
narrowest part of its course, and it is here that it is crossed by the
magnificent suspension bridge, known indifferently as the East River
Bridge, or Brooklyn Bridge, which provides land communication between
New York, with its population of two millions, and Brooklyn, the fourth
city of the States in point of size, with inhabitants numbering about
one million. Brooklyn is largely a residential place for persons whose
daily business is in New York. It has wide, well-planned streets, many
shaded by the luxuriant foliage of double rows of trees, and possesses
parks, public buildings, institutes, churches, etc., on a scale
commensurate with its importance.

The central span of Brooklyn Bridge, from tower to tower, is 1,595 feet,
and each shore part, extending from the tower to the anchorage of the
cables, is 930 feet span, while the two approaches beyond the anchorage
together add 2,534 feet to the total length, which is 5,989 feet, or
considerably over a mile. The centre span, it will be observed, is much
greater than that of the Niagara Falls Clifton Bridge, which was less
than one quarter of a mile, whereas the Brooklyn Bridge span extends to
something approaching one-third of a mile, or, more exactly, a few yards
longer than three-tenths. The width of the Brooklyn is another one of
its remarkable features, for this is no less than 85 feet, and includes
two roadways for ordinary vehicles, and two tramway tracks, on which the
carriages are moved by an endless cable, worked by a stationary engine
on the Brooklyn side. There is also a footpath, 13 feet wide, for
pedestrians. In this structure, as in many other suspension bridges,
advantage has been taken of the great tenacity of steel wire as compared
with iron bars. But here the wires are not twisted in strands like
ropes, but are laid straight together, and bound into a cylindrical
form, each wire being 3,572 feet long, and extending from end to end of
the cables, which are four in number, each calculated to bear a strain
of 12,200 tons. The number of wires in each cable is very great, for
instead of about the thousand of which the stranded wire cables usually
consist, there are 5,296 steel wires wrapped closely round, and forming
a cylinder 15¾ inches in diameter. Each wire is galvanised, that is,
coated with zinc, and then coated with oil. The towers over which the
cables pass are of masonry, and rise to 272 feet above high-water; their
dimensions at the water level are 140 feet by 50 feet, which offsets
diminish until at the top they are 120 feet by 40 feet. At the anchor
structures, the cables enter the masonry at nearly 80 feet above
high-water, and pass 28 feet into the stonework for connection with the
anchor chains. The anchorages are masses of masonry, measuring at the
base 129 feet by 119 feet, and at the top 117 feet by 104 feet, with a
height of 89 feet in front and 85 feet in the rear. The weight of each
anchor-plate is 23 tons. The roadway of the bridge is suspended from the
cables above the buildings and streets between the towers and the
anchorages. The approaches, on the Brooklyn side 971 feet, on the New
York side 1,563 feet, are carried on stonework arches, which are
utilised as warehouses, but where these approaches cross streets, iron
bridges are thrown over. The clear headway between the centre of the
roadway over the river at high-water is 135 feet, so that there is no
obstruction to navigation, and the headway at the towers is 119 feet, so
that the roadway rises towards the centre about 3 feet 3 inches in 100
feet. The two towers comprise more than 85,000 cubic yards of masonry,
and for various purposes 13,670 tons of concrete were used. The work was
commenced in January, 1870, and the first wire was carried across on
29th May, 1877. The bridge was opened to the public on the 24th of May,
1883, and the tramway four months later. The bridge was made free for
pedestrians in 1891, and in 1894 the tram-car fares were reduced to five
cents (2½_d._) for two journeys. In that year, 41,927,122 passengers
were carried on the cars. The average number of persons daily crossing
the bridge is estimated at about 115,000, although on one day (11th
Feb., 1895) as many as 225,645 passengers have been carried on the cars.
The cost of the work connected with this great bridge was $15,000,000
(£3,125,000).

In relation to the subject of wide-spanning bridges, the erection has
been contemplated of structures which would surpass in magnitude and
boldness any of those yet named. Thus, in 1894, the New York Chamber of
Commerce proposed to throw across the River Hudson, which washes the
western side of New York, a bridge with a clear span of 3,200 feet
(six-tenths of a mile), and 500 feet clear height; and the project was
declared by an eminent and experienced engineer to be quite feasible.

[Illustration:

  PLATE XV.

  THE BROOKLYN BRIDGE.
]

[Illustration:

  FIG. 148.—_Newspaper Printing-Room, with Walter Machines._
]



                           PRINTING MACHINES.


A volume might be filled with descriptions of the machines which in
every department of industry have taken the place of slow and laborious
manual labour. But if even we selected only such machines as from the
beautiful mechanical principles involved in their action, or from their
effects in cheapening for everybody the necessaries and comforts of
life, might be considered of universal interest, the limits of the space
we can afford for this class of inventions would be far exceeded. The
machines for spinning, for weaving fabrics, for preparing articles of
food, are in themselves worthy of attention; then there is a little
machine which in almost every household has superseded one of the most
primitive kinds of hand-work, and that is the sewing machine. But all
these we must pass over, and confine our descriptions of special
machines to a class in which the interest is of a still more general and
higher character, since their effect in promoting the intellectual
progress of mankind is universally acknowledged. We need hardly say that
we allude to Printing Presses, and if we add a few lines on printing
machines other than those which have given us cheap literature, it is
because these other machines also have contributed to the general
culture by giving us cheap decorative art, and in their general
principles they are so much akin to the former that but little
additional description is necessary.


                        _LETTERPRESS PRINTING._

The manner in which the youthful assistants of printers came to receive
their technical appellation of “devils” has been the subject of many
ingenious explanations. One of these is to the effect that the earlier
productions of the press, having imitated the manuscript characters, the
uninitiated supposed the impressions were produced by hand-copying, and
in consequence of their rapid production and exact conformity with each
other, it was thought that some diabolical agency must have been
invoked. Another story relates that one of Caxton’s first assistants was
a negro boy, who of course soon became identified in the popular mind
with an imp from the nether world. A very innocent explanation is put
forward in another tale, relating that one of the first English printers
had in his employment a boy of the name of De Ville, or Deville, which
name was soon corrupted into the now familiar title, and became the
inheritance of this youth’s successors in the craft. Perhaps a more
probable and natural explanation might be found in the personal
appearance which the apprentices must have presented, with hands, and no
doubt faces also, smeared over with the black ink which it was their
duty to manipulate. For the ink was formerly always laid upon large
round pads or balls of leather, stuffed with wool. When these balls,
Fig. 149, which were, perhaps, about 12 in. in diameter, had received a
charge of ink, the apprentice dabbed the one against the other, working
them with a twisting motion, and after having obtained a uniform
distribution of the ink on their surfaces with many dexterous
flourishes, he applied them to the face of the types with both hands,
until all the letters were completely and evenly charged. The operation
was very troublesome, and much practice was required before the
necessary skill was obtained, while it was always a most difficult
matter to keep the balls in good working condition.

[Illustration:

  FIG. 149.—_Inking Balls._
]

[Illustration:

  FIG. 150.—_Inking Roller._
]

The first important step towards the possibility of a printing machine
was made, when for these inking balls was substituted a cylindrical
roller, mounted on handles, Fig. 150. The body of the roller is of wood,
but it is thickly coated with a composition which unites the qualities
of elasticity, softness, and readiness to take up the ink and distribute
it evenly over the types. The materials used for this composition are
chiefly glue and treacle, and sometimes also tar, isinglass, or other
substances. Glycerine and various other materials have also been
proposed as suitable ingredients for these composition rollers, but it
is doubtful whether the original compound is not as efficacious as any
yet tried. The composition is not unlike india-rubber in its appearance
and some of its properties. Fig. 150 represents equally the mode in
which the roller is applied to the type in hand presses, and that in
which it is charged with ink, by being moved backwards and forwards over
a smooth table upon which the ink has been spread.

From the time of the first appearance of printing presses in Europe down
to almost the beginning of the present century, a period of 350 years,
no improvement in the construction appears to have been attempted. They
were simply wooden presses with screws, on exactly the same plan as the
cheese-presses of the period. Earl Stanhope first, in 1798, made a press
entirely of iron, and he provided it with an excellent combination of
levers, so that the “platen,” or flat plate which overlies the paper and
receives the pressure, is forced down with great power just when the
paper comes in contact with the types. Such presses are capable of
turning out about 250 impressions per hour, and it should be noted that
the very finest book printing is still done by presses upon this
principle. One reason is that in such cases, where it is desired to
print with the greatest clearness and depth of colour, the ink employed
is much thicker, or stiffer, and requires more thorough distribution and
application to the type than a machine can effect. Stanhope’s press was
not of a kind to meet the desire for rapid production, to which the
increasing importance of newspapers gave rise. The first practical
success in this direction was achieved by König, who, in 1814, set up
for Mr. Walter, the proprietor of the “Times,” two machines, by which
that newspaper was printed at the rate of 1,100 impressions per hour,
the machinery being driven by steam power.

The “Times” of the 28th November, 1814, in the following words made its
readers acquainted with the fact that they had in their hands for the
first time a newspaper printed by steam power:

“Our journal of this day presents to the public the practical result of
the greatest improvement connected with printing since the discovery of
the art itself. The reader of this paragraph now holds in his hand one
of many thousand impressions of ‘The Times’ newspaper, which were taken
off by a mechanical apparatus. A system of machinery almost organic has
been devised and arranged, which, while it relieves the human frame of
its most laborious efforts in printing, far exceeds all human powers in
rapidity and dispatch. That the magnitude of the invention may be justly
appreciated by its effects, we shall inform the public that after the
letters are placed by the compositors, and enclosed in what is called
the ‘form,’ little more remains for man to do than to attend upon and
watch this unconscious agent in its operations. The machine is then
merely supplied with paper, itself places the form, inks it, adjusts the
paper to the form newly inked, stamps the sheet, and gives it forth to
the hands of the attendant, at the same time withdrawing the form for a
fresh coat of ink, which itself again distributes, to meet the ensuing
sheet now advancing for impression, and the whole of these complicated
acts is performed with such a velocity and simultaneousness of movement
that no less than 1,100 sheets are impressed in one hour. That the
completion of an invention of this kind, not the effect of chance, but
the result of mechanical combinations, methodically arranged in the mind
of the artist, should be attended with many obstructions and much delay
may be readily admitted. Our share in this event has, indeed, only been
the application of the discovery, under an agreement with the patentees,
to our own particular business; yet few can conceive, even with this
limited interest, the various disappointments and deep anxiety to which
we have for a long course of time been subjected. Of the person who made
the discovery we have little to add. Sir Christopher Wren’s noblest
monument is to be found in the building which he erected: so is the best
tribute of praise which we are capable of offering to the inventor of
the printing machine comprised in the preceding description, which we
have feebly sketched, of the powers and utility of his invention. It
must suffice to say further, that he is a Saxon by birth, that his name
is König, and that the invention has been executed under the direction
of his friend and countryman, Bauer.”

[Illustration:

  FIG. 151.—_Diagram of Cowper and Applegath’s Single Machine._
]

Each of the machines erected by König for the “Times” printed only one
side of the sheet, so that when they had been half printed by one
machine, they had then to be passed through the other, in order to be
“perfected,” as it is technically termed. These machines were greatly
improved by Messrs. Applegath and Cowper, who contrived also a
modification by which the sheets could be perfected in one and the same
machine. As the principle of these machines has been followed, with more
or less diversity of detail, in most of the printing machines at present
in use, it is very desirable to lay that principle clearly before the
reader. The diagram, Fig. 151, will make the action of Applegath and
Cowper’s single-printing machine easily understood. The type is set up
on a flat form, A B, which occupies part of the horizontal table, C D,
the rest of which, A C, is the inking table. E is a large cylinder,
covered with woollen cloth, which forms the “blanket.” The paper passes
round this cylinder, and it is pressed against the form. The small black
circles, _f_, _g_, _h_, _k_, _l_, _m_, _n_, represent the rollers for
distributing the ink. _f_ is called the _ductor_ roller. This roller,
which revolves slowly, is made of metal, and parallel to it is a plate
of metal, having a perfectly straight edge, nearly, but not quite,
touching the cylinder, and at the other side, as well as at the
extremities, bent upwards, so as to form a kind of trough, to contain
the ink, as a reservoir. The slow rotation of the ductor conveys the ink
to the next roller, which is covered with composition, and being made to
move backwards and forwards between the ductor roller and the table at
certain intervals, it is termed the _vibrating_ roller. The ink having
thus reached the inking-table, is spread evenly thereon by the
_distributing rollers_, _h_, _k_, and it is taken up from the inking
table, as the latter passes under, by the _inking_ rollers, _l_, _m_,
_n_. The table, C D, as a whole is constantly moving right and left in a
horizontal direction, so that the form passes alternately under the
impression cylinder, E, and the inking rollers, _l_, _m_, _n_. The axles
of the inking and distributing rollers are made long and slender, and
instead of turning in fixed bearings, they rest in slots or notches, in
order that, as the form passes below them, they may be raised, so that
they rest on the inking slab, and on the types, only by their own
weight. They are placed not quite at right angles to the direction of
the table, but a little diagonally. The sliding motion caused by this,
helps very much in the uniform spreading of the ink. By these
arrangements the form is evenly smeared with ink, since each inking
roller passes over it _twice_ before it returns to meet the paper under
E.

[Illustration:

  FIG. 152.—_Diagram of Applegath and Cowper’s Perfecting Machine._
]

[Illustration:

  FIG. 153.—_Cowper’s Double Cylinder Machine._
]

Fig. 152 is a similar diagram, to show the action of the double or
perfecting printing machine, in which the sheets are printed on both
sides. It will be observed that the general arrangement of impression
cylinder, rollers, &c., is represented in duplicate, but reversed in
direction. There are also two cylinders, B B, the purpose of which, as
may be gathered from an inspection of the diagram, is to reverse the
sheets of paper, so that after one side has been printed under the
cylinder, E´, the blank surface may be turned downward, ready to receive
the impression from the form, A B. Fig. 153 gives a view of the Cowper
and Applegath double machine, as actually constructed. The man standing
up is called the _feeder_ or _layer-on_. He pushes the sheets forward,
one by one, towards the tapes, which carry them down the farther side of
the more distant cylinder, under which they pass, receiving the
impression; and so on in the manner already indicated in the diagram,
Fig. 152, until finally they reach a point where, released by the
separation of the two sets of tapes, they are received by the
_taker-off_ (the boy who is represented seated on the stool), and are
placed by him on a table. The bed or table which carries the form moves
alternately right and left, impelled by a pinion acting in a rack
beneath it, in such a manner that the direction of the table’s motion is
changed at the proper moment, while the driving pulley continues to
revolve always in the same direction. The movements of the table and of
the cylinders are performed in exact harmony with each other, for these
pieces are so connected by trains of wheels and rack-work that the
sheets of paper may always receive the impression in the proper position
as regards the margins, and therefore, when the sheets are printed on
both sides, the impressions will be exactly opposite to each other. This
gives what is technically called “true register,” and as this cannot be
secured unless the paper travels over both cylinders at precisely the
same rate, these are finished with great care by turning their surfaces
in a lathe to exactly the same diameter. The action of the machine will
not be fully understood without a glance at the arrangement of the
endless tapes which carry the paper on its journey. The course of these
may be followed in Fig. 154, and a simple inspection of the diagram will
render a tedious description unnecessary.

[Illustration:

  FIG. 154.—_Tapes of Cowper’s Machine._
]

In Fig. 155 we have a representation of a steam-power printing machine,
such as is now very largely used for the ordinary printing of books,
newspapers of moderate circulation, hand-bills, &c., and in all the
ordinary work of the printing press. In this the table on which the form
is placed has a reciprocating motion, but the large cylinder moves
continuously always in the same direction. The feeder, or layer-on,
places the sheet of paper against certain stops, and at the right moment
the sheet is nipped by small steel fingers, and carried forwards to the
cylinder, which brings it into contact with the inked type. This is done
with much accuracy of register, for the impression cylinders gear in
such a manner with the rest of the parts that their revolutions are
synchronous. This is a perfecting machine, for the paper, after having
received the impression on one side, is carried by tapes round the other
cylinder, where it receives the impression on the other side, “set-off
sheets” being passed through the press at the same time. The axles of
the impression cylinders are mounted at the ends of short rocking beams,
by small oscillations of which the cylinders are alternately brought
down upon, or lifted off, the form passing below them. A machine of this
kind can print 900 impressions per hour, even of good bookwork, and for
newspaper or other printing, where less accuracy and finish are
required, it may be driven at such a rate as to produce 1,400 perfected
impressions per hour.

[Illustration:

  FIG. 155.—_Messrs. Hopkinson and Cope’s Perfecting Machine._
]

The machines used for lithographic printing by steam power are almost
identical in their general arrangement with that just described, which
may be taken as a representative specimen of the modern printing
machine.

To such machines as those already described the world is indebted for
cheap books, cheap newspapers, and cheap literature in general. But
when, with railways and telegraphs, came the desire for the very latest
intelligence, the necessities of the newspaper press, as regards
rapidity of printing, soon required a greater speed than could possibly
be attained by any of the flat form presses; for in these the table,
with the forms placed upon it, is unavoidably of a considerable weight,
and this heavy mass has to be set in motion, stopped, moved in the
opposite direction, and again stopped during the printing of each sheet.
The shocks and strains which the machine receives in these alternate
reversals of the direction of the movement impose a limit beyond which
the speed cannot be advantageously increased. When Mr. Applegath was
again applied to by the proprietors of the “Times” to produce a machine
capable of working off a still larger number of impressions, he decided
upon abandoning the plan of reciprocating movement, and substituting a
continuous rotary movement of the type form. And he successfully
overcame the difficulties of attaching ordinary type to a cylindrical
surface. The idea of placing the type on a rotating cylinder is due to
Nicholson, who long ago proposed to give the types a wedge shape, so
that the pieces of metal would, like the stones of an arch, exactly fit
round the cylindrical surface. The wedge-shaped types were, however, so
liable to be thrown from their places by the centrifugal force, that
Nicholson proposed also certain mechanical methods of locking the types
together after they had been placed on the circumference of the drum.
The plan he suggested for this purpose involved, however, such an
expenditure of time and trouble that his idea was never carried into
practice. Mr. Applegath used type of the ordinary kind, which was set up
on flat surfaces, forming the sides of a prism corresponding to the
circumference of his revolving type cylinder, which was very large and
placed vertically. The flat surfaces which received the type were the
width of the columns of the newspaper, and the type forms were firmly
locked up by screwing down wedge-shaped rules between the columns at the
angles of the polygon. These form the “column rules,” which make the
upright lines between the columns of the page, and by their shape they
served to securely fix the type in its place. The diameter of the
cylinder to which the form was thus attached was 5 ft. 6 in., but the
type occupied only a portion of its circumference, the remainder serving
as an inking table. Round the great cylinder eight impression rollers
were placed, and to each impression roller was a set of inking rollers.
At each turn, therefore, of the great cylinder eight sheets received the
impression. These cylinders were, as already stated, placed vertically,
and, as it was necessary to supply the sheets from horizontal tables, an
ingenious arrangement of tapes and rollers was contrived, by which each
sheet was first carried down from the table into a vertical position,
with its plane directed towards the impression roller, in which position
it was stopped for an instant, then moved horizontally forwards round
the impression cylinder, and was finally brought out, suspended
vertically, ready for a taker-off to place on his pile. This machine
gave excellent results as to speed and regularity. From 10,000 to 12,000
impressions could be worked off in an hour, and the advantage was
claimed for it of keeping the type much cleaner, by reason of its
vertical position. The power of this machine may be judged of from one
actual instance. It is stated that of copies of the “Times” in which the
death of the Duke of Wellington was announced, 14th November, 1852, no
less than 70,000 were printed in one day, and the machines were not once
stopped, either to wash the rollers or to brush the forms. It may be
mentioned, in order to give a better idea of the magnitude of the
operation of printing this one newspaper, that one average day’s copies
weigh about ten tons, and that the paper for the week’s consumption
fills a train of twenty waggons.

At the “Times” office and elsewhere, the vertical machine has some years
ago been superseded by others with horizontal cylinders. The fastest,
perhaps, of all these printing machines is that which is now known as
the “Walter Press,” so called either because its principle was suggested
by the proprietor of the “Times,” or merely out of compliment to him.
The improvements which are embodied in the Walter Press have been the
subject of several patents taken out in the names of Messrs. MacDonald
and Calverley, and it is to these improvements that we must now direct
the attention of the reader. But we must premise that such machines as
the Walter Press became possible only by the discovery of the means of
rapidly producing what is called a stereotype plate from a form of type.
A full account of the methods of effecting this is reserved for a
subsequent article, but here it may suffice to say, that when a thick
layer of moist cardboard, or rather a number of sheets of thin unsized
paper pasted together and still quite moist, is forced down upon the
form by powerful pressure, a sharp even mould of the type is obtained,
every projection in the latter producing a corresponding depression in
the _papier maché_ mould. When the paper mould is dry, it may be used
for forming a _cast_ by pouring over it some fusible metallic alloy,
having the properties of becoming liquid at a temperature which will not
injure the mould, of taking the impressions sharply, and of being
sufficiently hard to bear printing from. One of the improvements in
connection with the Walter Press is in the mode of forming cylindrical
stereotype casts from the paper mould. For this purpose the mould is
placed on the _internal_ surface of an iron semi-cylinder, with the face
which has received the impression of the type inwards. The central part
of the semi-cylinder is occupied by a cylindrical iron core, which is
adjusted so as to leave a uniform space between its convex surface and
the concave face of the mould. Into this space is poured the melted
metal, and its pressure forces the mould closely against the concave
cylindrical surface to which it is applied, so that the thickness
becomes quite uniform. The iron core has a number of grooves cut round
it, and these produce in the cast so many ribs, or projections, which
encircle the inner surface, and serve both to strengthen the cast and
afford a ready means of obtaining an exact adjustment. Not the complete
cylinder, but only half its circumference, is cast at once, the axis of
the casting apparatus being placed horizontally, and the liquid metal
poured in one unbroken stream between the core and the mould from a
vessel as long as the cylinders. Fig. 156 is a section of the casting
apparatus, in which _a_ is the core, _b_ the _papier maché_ mould, _c_
the iron semi-cylinder containing it, _d_ the metal which has been
poured in at the widened space, _e_. When the metal has solidified, the
core is simply lifted off, and the cast is then taken out, in the form
of a semi-cylinder, the internal surface of which has exactly the
diameter of the external surface of the roller of the machine on which
it is to be placed, in company with another semi-cylindrical plate, so
that the two together encircle half the length of the roller, and when
another pair of semi-cylinders have been fixed on the other part of the
roller, the whole matter of one side of the newspaper sheet, usually
four pages, is ready for printing. One great advantage of working from
stereotype casts made in this way is that the form-bearing cylinder of
the machine has no greater circumference than suffices to afford space
for the matter on one side of the paper. The casts are securely fixed on
the revolving cylinder by elbows, which can be firmly screwed down. The
casts are usually made to contain one page each, so that four
semi-cylinders, each half the length of the revolving cylinder, are
fixed on the circumference of the latter. The process of casting in no
way injures the paper mould, which is in fact generally employed to
produce several plates.

[Illustration:

  FIG. 156.
]

[Illustration:

  FIG. 157.—_Diagram of the Walter Press._
]

The Walter Machine is not fed with separate sheets of paper, but takes
its supply from a huge roll, and itself cuts the paper into sheets after
it has impressed it on both sides. This is done by a very simple but
effective plan, which consists in passing the paper between two
equal-sized rollers, the circumference of which is precisely the length
of the sheets to be cut. These rollers grip the paper, but only on the
marginal spaces; and on the circumference of one of them, and parallel
to its axis, is a slightly projecting steel blade, which fits into a
corresponding recess, or groove, in the circumference of the other, and
at this time the whole width of the sheet is firmly held by a projecting
piece acted on by a spring. Although the Walter Machine, as actually
constructed, presents to the uninitiated spectator an apparently endless
and intricate series of parallel cylinders and rollers, yet it is in
reality exceedingly simple in principle, as may be seen by the diagram
given in Fig. 157. In this we may first direct the reader’s attention to
the two cylinders, F_{1}, F_{2}, which bear the stereotype casts—one of
the matter belonging to one side of the sheet, the other of the matter
belonging to the other side, for the Walter Press is a perfecting
machine—and the web of paper having been printed by F_{1}, against which
it is pressed by the roller, P_{1}, passes straight, as shown by the
dotted line, to the second pair of cylinders, in order to be printed on
the other side; and here, of course, the form cylinder, F_{2}, is below,
and the impression cylinder, P_{2}, above, and an endless cleaning
blanket is supplied to the latter to receive the _set-off_. The web of
paper then passes between the cutting rollers, C, C_{1}, by which it is
cut in sheets. But the knife has a narrow notch in the centre, and one
at each end, so that the paper is not severed at those parts, narrow
strips or tags being left, which maintain for a while a slight
connection. But the tapes, _t_{1}_, _t_{2}_, between which the paper is
now carried, are driven at a rather quicker rate than the web issues
from C, C_{1}; and the result is, that the tags are torn, and the sheet
becomes separated from the portion next following it. Thus, as a
separate sheet, it arrives at the horizontal tapes, _h_, and is brought
to another set of tapes mounted on the frame, _r_, rocking about the
centre, _c_, by which it is brought finally to the tapes, _f_{1}_,
_f_{2}_, which by the movement of _r_ receive the sheets alternately. A
sheet-flyer, _s_, oscillates between the tapes, _f_{1}_, _f_{2}_; and as
fast as the sheets arrive, lays them down right and left alternately,
and it only remains for the piles, _p_{1}_, _p_{2}_ so formed, to be
removed. The inking apparatus of each form-cylinder is indicated by the
series of rollers marked I_{1}, I_{2}; and in this part of the machine
there are also some improvements over former presses, for the
distributing rollers are not made of composition, but of iron, turned
with great exactness to a true surface, and arranged so as not quite to
touch each other. At D is an apparatus for damping the paper, in which
there are hollow perforated cylinders, covered by blanket, and filled
with some porous material, which is kept constantly wet. These cylinders
being made to rotate rapidly, the centrifugal force causes the water to
find its way uniformly to the outside. Here the paper also passes
between rollers intended to flatten and to stretch it. At R is the great
roll of paper, from which the machine takes its supply. These rolls
contain, perhaps, five miles length of paper, and at first it was a
matter of some difficulty to fix them firmly on their wooden axles, so
that they might be steadily unwound; but the contrivers of the Walter
Press make these spindles as tight as may be required by forming them in
wedge-shaped pieces, which can be made to increase the thickness of the
spindle by drawing one upon another by screws.

The great speed of the Walter Machine is secured by the paper being
drawn by the machine itself from a continuous web, instead of being laid
on in a separate sheet, so that the machine is not dependent on the
dexterity of the layers-on, who are besides necessarily highly-skilled
workmen, and therefore a great economy of wages results from using a
machine which does not require their services; and as the Walter Press
also itself lays down the perfected sheets, the necessary attendants are
as few as possible. The waste of paper and loss of time by stoppages are
said to be extremely small with this machine.

Fig. 148 will give some idea of the appearance of the printing-room
where one of the leading London daily papers is being printed by Walter
Presses.

Another fast printing machine is the type revolving cylinder machine
invented by Colonel Richard M. Hoe, and manufactured by the well-known
firm of Hoe and Company, New York, with whose name the history of fast
printing machines must ever be associated. In these machines the type is
placed on the circumference of a cylinder which rotates about a
horizontal axis, and the difficulties of securely locking up the type
are successfully overcome. The machines are made with two, four, six,
eight, or ten impression cylinders, and at each revolution of the great
cylinder the corresponding number of impressions are produced. The
engraving on the opposite page, Fig. 158, represents the two-cylinder
machine, and an examination of the figure will render its general action
intelligible. The form of type occupies about one-fourth of the
circumference of the great cylinder, the remainder being used as an
ink-distributing surface. Round this main cylinder, and parallel to it,
are placed smaller impression cylinders, from two to ten in number,
according to the size of the machine. When the press is in operation,
the rotation of the main cylinder carries the type form to each
impression cylinder in succession, and it there impresses the paper,
which is made to arrive at the right time to secure true register. One
person is required for each impression cylinder, to supply the sheets of
paper, which have merely to be laid in a certain position, when, at the
proper moment, they are seized by the “grippers,” or fingers of the
machine, and after having been printed, are carried out by tapes, and
laid in heaps by self-acting sheet-flyers, by which the hands which are
required to receive and pile the sheets in other machines are dispensed
with. The ink is contained in a fountain placed beneath the main
cylinder, and is conveyed by means of rollers to the distributing
surface of the main cylinder. This surface, being lower than that of the
type forms, passes by the impression cylinders without touching them.
For each impression cylinder there are two inking rollers, receiving
their supply of ink from the distributing surface of the main cylinder.
These inking rollers, the bearings of which are, by springs, drawn
towards the axis of the main cylinder, rise as the form passes under
them, and having inked it, they again drop on to the distributing
surface. Each page of the matter is locked up on a detachable segment of
the large cylinder, which segment constitutes its bed and chase. The
column-rules are parallel with the shaft of the cylinder, and are
consequently straight, while the head, advertising, and dark rules have
the form of segments of a circle. The column-rules are in the shape of a
wedge, with the thin end directed towards the axis of the cylinder, so
as to bind the types securely. These wedge-shaped column-rules are held
in their place by tongues projecting at intervals along their length,
and sliding in grooves cut crosswise in the face of the bed. The spaces
in the grooves between the column-rules are accurately fitted with
sliding blocks of metal level with the surface of the bed, the ends of
the blocks being cut away underneath, to receive a projection on the
sides of the tongues of the column-rules. The locking up is effected by
means of screws at the foot of each page, by which the type is held as
securely as in the ordinary manner upon a flat bed. The main cylinder of
the machine represented in Fig. 158 has a diameter of 3 ft. 9 in., and
its length is, according to the size of the sheets to be printed, from 4
ft. 5 in. to 7 ft. 4 in. The whole is about 20 ft. long, 10 ft. wide,
including the platforms, and a height of 9 ft. in the room in which it
is placed suffices for its convenient working. The steam power required
is from one to two horse-power, according to the length of the main
cylinder. The speed of these machines is limited only by the ability of
the feeders to supply the sheets fast enough. The ten-cylinder machine
has, of course, ten impression cylinders, instead of two, and there are
ten feeding-tables, arranged one above the other, five on each side. The
main cylinder has a diameter of 4 ft. 9 in., and is 6 ft. 8 in. long.
The machine occupies altogether a space of 31 ft. by 16 ft., and its
height is 18 ft. A steam engine of eight horse-power is sufficient to
drive the ten-cylinder machine, which is then capable of producing
25,000 impressions per hour. The mechanism of the larger machines is
precisely similar to that of the two-cylinder machine, except such
additional devices as are necessary to carry the paper to and from the
main cylinder at four, six, eight, or ten points of its circumference.
Much admirable contrivance is displayed in the manner of disposing
feeders as closely as possible round the central cylinder.

[Illustration:

  FIG. 158.—_Messrs. Hoe’s Type Revolving Cylinder Machine._
]

In some machines, such as Messrs. Hoe’s, Fig. 158, the sheet-flyers are
interesting features, for they form an efficient contrivance for laying
down and piling up, with the greatest regularity, sheet after sheet as
it issues from the press. The sheet-flyer is in fact an automatic
taker-off, and therefore it supersedes the services of the boy who would
otherwise be required. It is simply a light wooden framework of parallel
bars, turning on one of its sides as a centre; and the tapes carrying
the sheet, passing down between the bars, bring the paper down upon the
frame, where its progress is then stopped, the frame makes a rapid turn
on its centre, lays down the sheet, and quickly rises to receive another
from the tapes. One can hardly see a printing machine in action without
being struck with the deftness with which the sheet-flyer does its duty;
for the precision with which it receives a sheet, lays it down, and then
quickly returns, to be ready for the next, suggest to the mind of the
spectator rather the movements of a conscious agent than the motions of
an unintelligent piece of mechanism. The sheet-flyer is seen at the
left-hand side of Fig. 158, where it is in the act of laying down a
sheet on the pile it has already formed.

[Illustration:

  FIG. 159.—_Messrs. Hoe’s “Railway” Machine._
]

[Illustration:

  FIG. 160.—_Napier’s Platen Machine._
]

The modern improvements in printing presses are well illustrated by the
machine represented on the opposite page, Fig. 159, which has been
designed by the Messrs. Hoe to work exclusively by hand. It is intended
for the newspaper and job work of a country office, and it works easily,
without noise or jar, by turning the handle always in the same
direction, producing 800 impressions in an hour. The bed moves backwards
and forwards on wheels running on rails, the reciprocating movement
being derived from the circular one by means of a crank. From the mode
in which the table is carried backwards and forwards, the manufacturers
call this the “Railway Printing Machine.” The paper is fed to the
underside of the cylinder, which, after an impression has been given,
remains stationary while the bed is returning, and while the layer-on is
adjusting his sheet of paper. The axle of the impression cylinder
carries a toothed wheel working in a rack on the bed or table, the wheel
having at two parts of its circumference the teeth planed off so as to
permit of the return of the table without moving the impression
cylinder, which is again thrown into gear with the rack by a catch, so
that the same tooth of the rack always enters the same space on the
toothed wheel, and thus a good register is secured. The impression
cylinder remains unaltered, whatever may be the size of the type form,
it being only necessary to place the forward edge of the form always on
the same line of the bed. Machines of a very similar construction, but
driven by steam power, are used in lithographic printing; and in some of
these machines advantage is elegantly taken of the fact that, when a
wheel rolls along, the uppermost point of its circumference is always
moving forward at exactly twice the velocity of its centre. Hence, if
the table of a printing machine rests on the _circumference_ of wheels,
a backward and forward movement of the centres of these wheels, produced
by the throw of a crank through a space of 2 ft., would produce a
rectilineal reciprocating movement through a distance of 4 ft. of a
table resting on the circumference of the wheels. Any reader who is
interested in geometry or mechanics would do well to convince himself
that the lowest point of the wheel of a railway carriage, for example,
is stationary (considered while it is the lowest point), that the
_centre_ of the wheel is moving forwards with the velocity of the train,
and that the highest point of the wheel is moving forwards with just
twice the speed of the train. There is no difficulty about the rate of
rectilineal motion of the centre, but the reader cannot possibly
perceive the truth of the statement regarding the lowest and highest
points unless he reflects on the subject, or puts it to the test of
experiment. Another form of press which is used for good book printing
is represented in the engraving, Fig. 160, which shows Napier’s platen
machine. There the action is similar to that of the ordinary hand
presses as regards the mode in which the paper is pressed against the
face of the type; but the movements are all performed by steam power,
applied through the driving belt, shown in the figure.

The various kinds of printing machines adapted to each description of
work are too numerous to admit of even a passing mention here; but those
which have been described may fairly be considered as representing the
leading principles of modern improvements. This article relates only to
the mechanism by which an impression is transferred from a form to the
surface of paper: the interesting and novel _processes_ by which the
form itself may be produced—processes which have amazingly abridged the
printers’ labour and extended the resources of the art—deserve a
separate chapter, and will furnish matter for an article on Printing
Processes, which will be the better understood by being placed after
chapters wherein the scientific bases of some of these processes are
discussed.


                          _PATTERN PRINTING._

The machines used for printing patterns are, in principle, very similar
to those for letterpress printing; but the circumstance of several
different colours having frequently to go to the production of one
pattern leads to the multiplication, in the present class of machines,
of the apparatus for distributing the colours and impressing the
materials. Pattern printing machines are most extensively used for
impressing fabrics, such as calicoes, muslins, &c., and for producing
the wall-papers for decorating apartments. The machines employed for
calicoes and for papers are so much alike, that to describe the one is
almost to describe the other.

The papers intended for paper-hangings are, in the first instance,
covered with a uniform layer of the colour which is to form the ground,
and this is done even in the case of papers which are to have a white
ground. The colours thus laid on, and those which are applied by the
machine, are composed of finely-ground colouring matters mixed with thin
size or glue to a suitable consistence, and the ground-tint is given by
bringing the upper surface of the paper, as it is mechanically unwound
from a great roll, into contact with an endless band of cloth emerging
from a trough containing a supply of the fluid colour. The paper then
passes over a horizontal table, where the layer of colour is uniformly
distributed over its surface by brushes moved by machinery, and the
paper, after having been thoroughly dried, is ready to receive the
impressions. The impressions may be given by flat blocks of wood on
which the pattern is carved in relief, or from revolving cylinders on
which the pattern is similarly carved. The former is the process of hand
labour called “block printing,” and it requires much skill and care on
the part of the operator; but with these, excellent results are
obtained, as a correct adjustment of the positions of the parts of the
pattern can always be secured. The latter is the mode of printing
mechanically on rollers, corresponding with the type-bearing cylinders
of the machines already described; but for pattern printing on paper
they are made of fine-grained wood, mounted on an iron axle, and they
are carved so that the design to be printed stands out in relief on
their surface. One of these rollers is represented in Fig. 161, and it
should be clearly understood that each colour in the pattern on a
wall-paper requires a separate roller, the design cut on which
corresponds only with the forms the particular colour contributes to the
pattern. Such rollers being necessarily somewhat expensive, as the
pattern is usually repeated many times over the cylindrical surface, the
plan has been adopted of fastening a mass of hard composition in an iron
axle, and when this has been turned to a truly cylindrical surface, it
is made to receive plates of metal, formed of a fusible alloy of lead,
tin, and nickel. These plates are simply casts from a single carved
wooden mould of the pattern, which has thus only once to be formed by
hand. The plates are readily bent when warmed, and are thus applied to
the cylindrical surface, to which they are then securely attached. It is
found advantageous to cover the prominent parts of the rollers which
produce the impressions with a thin layer of felt, as this substance
takes up the colours much more readily than wood or metal, and leaves a
cleaner impression.

[Illustration:

  FIG. 161.—_Roller for Printing Wall-Papers._
]

The machine by which wall-papers are printed is represented in Fig. 162,
where it will be observed that the impression cylinder has a very large
diameter, and that a portion of its circumference forms a toothed wheel,
which engages a number of equal-sized pinions placed at intervals about
its periphery. Each pinion being fixed on the axle of a pattern-bearing
roller, these are all made to revolve at the same rate. There is,
however, some adjustment necessary before that exact correspondence of
the impressions with each other is secured, which is shown on the
printed pattern by each colour being precisely in its appointed place.
The rollers are constantly supplied with colour by endless cloths, which
receive it from the troughs that are shown in the figure, one trough
being appropriated to each roller. Some of these machines can print as
many as eighteen or twenty different colours at once, by having that
number of rollers; and it is easy to see how, by dividing each trough
into several vertical compartments, in each of which a different colour
is placed, it would be possible to triple or even quadruple the number
of colours printed by one machine.

The machinery by which calicoes are printed is almost identical in
construction with that just described, and presents the same general
appearance. There is, however, an important difference in the rollers,
which in calico printing are of copper or bronze, and have the design
engraved upon their polished cylindrical surface, not in relief, but in
hollows. After the whole surface of the roller becomes charged with
colour, there is in the machine a straight-edge, which removes the
colour from the smooth surface, leaving only what has entered into the
hollow spaces of the design, which, as the roller comes round to the
cloth, yield it up to the surface of the latter. Thus, by a self-acting
arrangement, the rollers are charged with colour, cleaned, and made to
give up their impressions to the stuff by parting with the colour in the
hollows. Rollers having patterns in relief are also used in calico
printing, the mechanism being then almost identical with that of the
former machine. It need hardly be said that great pains are taken in the
construction of such machines to have each part very accurately
adjusted, so that the impression may fall precisely upon the proper
place, without any blurring or confusion of the colours, and the fact
that an intricate design, having perhaps eighteen or twenty tints, can
be thus mechanically reproduced millions of times speaks volumes for the
accuracy and finish of the workmanship which are bestowed on such
printing machines.

[Illustration:

  FIG. 162.—_Machine for Printing Paper-Hangings._
]

[Illustration:

  FIG. 163.—_Chain-Testing Machine at Messrs. Brown and Lenox’s Works,
    Millwall._
]



                            HYDRAULIC POWER.


If a hollow sphere, _a_, Fig. 173, be pierced with a number of small
holes at various points, and a cylinder, _b_, provided with a piston,
_c_, fitted into it, when the apparatus is filled with water, and the
piston is pushed inwards, the water will spout out of all the orifices
equally, and not exclusively from that which is opposite to the piston
and in the direction of its pressure. The jets of water so produced
would not, as a matter of fact, all pursue straight paths radiating from
the centre of the sphere, because gravity would act upon them; and all,
except those which issued vertically, would take curved forms. But when
proper allowance is made for this circumstance, each jet is seen to be
projected with equal force in the direction of a radius of the sphere.
This experiment proves that when pressure is applied to any part of a
liquid, that pressure is transmitted _in all directions equally_. Thus
the pressure of the piston—which, in the apparatus represented in the
figure, is applied in the direction of the axis of the cylinder only—is
carried throughout the whole mass of the liquid, and shows itself by its
effect in urging the water out of the orifices in the sphere in all
directions; and since the force with which the water rushes out is the
same at every jet, it is plain that the water must press equally against
each unit of area of the inside surface of the hollow sphere, without
regard to the position of the unit.

If we suppose the piston to have an area of one square inch, and to be
pushed inwards with a force of 10 lbs., it cannot be doubted that the
square inch of the inner surface of sphere immediately opposite the
cylinder will receive also the pressure of 10 lbs.; and since the
pressures throughout the interior of the hollow globe are equal, every
square inch of its area will also be pressed outwards with a force equal
to 10 lbs. Hence, if the total area of the interior be 100 square
inches, the whole pressure produced will amount to a hundred times 10
lbs.

[Illustration:

  FIG. 164.—_Pascal’s Principle._
]

[Illustration:

  FIG. 165.—_Collar of Hydraulic Cylinder._
]

That water or any other liquid would behave in the manner just described
might be deduced from a property of liquids which is sufficiently
obvious, namely, the freedom with which their particles move or slide
upon each other. The equal transmission of pressure in all directions
through liquids was first clearly expressed by the celebrated Pascal,
and it is therefore known as “Pascal’s principle.” He said that “if a
closed vessel filled with water has two openings, one of which is a
hundred times as large as the other; and if each opening be provided
with an exactly-fitting piston, a man pushing in the small piston could
balance the efforts of a hundred men pushing in the other, and he could
overcome the force of ninety-nine.” Pascal’s principle—which is that of
the hydraulic press—may be illustrated by Fig. 164, in which two tubes
of unequal areas, _a_ and _b_, communicate with each, and are supposed
to be filled with a liquid—water, for example, which will, of course,
stand at the same level in both branches. Let us now imagine that
pistons exactly fitting the tubes, and yet quite free to move, are
placed upon the columns of liquid—the larger of which, _b_, we shall
suppose to have five times the diameter, and therefore twenty-five times
the sectional area, of the smaller one. A pressure of 1 lb. applied to
the smaller piston would, in such a case, produce an upward pressure on
the larger piston of 25 lbs.; and in order to keep the piston at rest,
we should have to place a weight of 25 lbs. upon it. Here then a certain
force appears to produce a much larger one, and the extent to which the
latter may be increased is limited only by the means of increasing the
area of the piston. Practically, however, we should not by any such
arrangement be able to prove that there is exactly the same proportion
between the total pressures as between the areas, for the pistons could
not be made to fit with sufficient closeness without at the same time
giving rise to so much friction as to render exact comparisons
impossible. We may, however, still imagine a theoretical perfection in
our apparatus, and see what further consequences may be deduced,
remembering always that the actual results obtained in practice would
differ from these only by reason of interfering causes, which can be
taken into account when required. We have supposed hitherto that the
pressures of the pistons exactly balance each other. Now, so long as the
system thus remains in equilibrium no _work_ is done; but if the
smallest additional weight were placed upon either piston, that one
would descend and the other would be pushed up. As we have supposed the
apparatus to act without friction, so we shall also neglect the effects
due to difference in the levels of the columns of liquid when the
pistons are moved; and further, in order to fix our ideas, let us
imagine the smaller tube to have a section of 1 square inch in area, and
the larger one of 25 square inches. Now, if the weight of the piston,
_a_, be increased by the smallest fraction of a grain, it will descend.
When it has descended a distance of 25 in., then 25 cubic inches of
water must have passed into _b_, and, to make room for this quantity of
liquid, the piston with the weight of 25 lbs. upon it must have risen
accordingly. But since the area of the larger tube is 25 in., a rise of
1 in. will exactly suffice for this; so that a weight of 1 lb.
descending through a space of 25 in., raises a weight of 25 lbs. through
a space of 1 in. This is an illustration of a principle holding good in
all machines, which is sometimes vaguely expressed by saying that _what
is gained in power is lost in time_. In this case we have the piston,
_b_, moving through the space of 1 in. in the same time that the piston
a moves through 25 in.; and therefore the _velocity_ of the latter is
twenty-five times greater than that of the former, but the time is the
same. It would be more precise to say, that what is gained in force is
lost in space; or, that no machine, whatever may be its nature or
construction, is of itself capable of doing _work_. The “mechanical
powers,” as they are called, can do but the work done upon them, and
their use is only to change the relative amounts of the two factors, the
product of which measures the work, namely, space and force. Pascal
himself, in connection with the passage quoted above, clearly points out
that in the new mechanical power suggested by him in the hydraulic
press, “the same rule is met with as in the old ones—such as the lever,
wheel and axle, screw, &c.—which is, that the distance is increased in
proportion to the force; for it is evident that as one of the openings
is a hundred times larger than the other, if the man who pushes the
small piston drives it forward 1 in., he will drive backward the large
piston one-hundredth part of that length only.” Though the hydraulic
press was thus distinctly proposed as a machine by Pascal, a certain
difficulty prevented the suggestion from becoming of any practical
utility. It was found impossible, by any ordinary plan of packing, to
make the piston fit without allowing the water to escape when the
pressure became considerable. This difficulty was overcome by Bramah,
who, about the end of last century, contrived a simple and elegant plan
of packing the piston, and first made the hydraulic press an efficient
and useful machine. Fig. 166 is a view of an ordinary hydraulic press,
in which a is a very strong iron cylinder, represented in the figure
with a part broken off, in order to show that inside of it is an iron
piston or ram, _b_, which works up and down through a water-tight
collar; and in this part is the invention by which Bramah overcame the
difficulties that had previously been met with in making the hydraulic
press of practical use. Bramah’s contrivance is shown by the section of
the cylinder, Fig. 165, where the interior of the neck is seen to have a
groove surrounding it, into which fits a ring of leather bent into a
shape resembling an inverted U. The ring is cut out of a flat piece of
stout leather, well oiled and bent into the required shape. The effect
of the pressure of the water is to force the leather more tightly
against the ram, and as the pressure becomes greater, the tighter is the
fit of the collar, so that no water escapes even with very great
pressures. To the ram, _b_, Fig. 166, a strong iron table, _c_, is
attached, and on this are placed the articles to be compressed. Four
wrought iron columns, _d d d d_, support another strong plate, _e_, and
maintain it in a position to resist the upward pressure of the goods
when the ram rises, and they are squeezed between the two tables. The
interior of the large cylinder communicates by means of the pipe, _f f_,
with the suction and force-pump, _g_, in which a small plunger, _o_,
works water-tight. Suppose that the cylinders and tubes are quite filled
with water, and that the ram and piston are in the positions represented
in the figure. When the piston of the pump, _g_, is raised, the space
below it is instantly filled with water, which enters from the
reservoir, _h_, through the valve, _i_, the valve _k_ being closed by
the pressure above it, so that no water can find its way back from the
pipe, _f_, into the small cylinder. When the piston has completed its
ascent, the interior of the small cylinder is therefore completely
filled with water from the reservoir; and when the piston is pushed
down, the valve, _i_, instantly closes, and all egress of the liquid in
that direction being prevented, the greater pressure in _g_ forces open
the valve, _k_, and the water flows along the tube, _f_, into the large
cylinder. The pressure exerted by the plunger in the small cylinder,
being transmitted according to the principles already explained,
produces on each portion of the area of the large plunger equal to that
of the smaller an exactly equal pressure. In the smaller hydraulic
presses the plunger of the forcing-pump is worked by a lever, as
represented in the figure at _n_; so that with a given amount of force
applied by the hand to the end of the lever, the pressure exerted by the
press will depend upon the proportion of the sectional area of _b_ to
that of _o_, and also upon the proportion of the length _m n_, to the
length _m l_. To fix our ideas, let us suppose that the distance from
_m_ of the point _n_ where the hand is applied is ten times the distance
_m l_, and that the sectional area of _b_ is a hundred times that of
_o_. If a force of 60 lbs. be applied at _n_, this will produce a
downward pressure at _m_ equal to 60 × 10, and then the pressure
transmitted to the ram of the great cylinder will be 60 × 10 × 100 =
60,000 lbs. The apparatus is provided with a safety-valve at _p_, which
is loaded with a weight; so that when the pressure exceeds a desired
amount, the valve opens and the water escapes. There is also an
arrangement at _q_ for allowing the water to flow out when it is desired
to relieve the pressure, and the water is then forced out by the large
plunger, which slowly descends to occupy its place. The body of the
cylinder is placed beneath the floor in such presses as that represented
in Fig. 166, in order to afford ready access to the table on which the
articles to be compressed are placed.

[Illustration:

  FIG. 166.—_Hydraulic Press._
]

The force which may, by a machine of this kind, be brought to bear upon
substances submitted to its action, is limited only by the power of the
materials of the press to resist the strains put upon them. If water be
continually forced into the cylinder of such a machine, then, whatever
may be the resistance offered to the ascent of the plunger, it must
yield, or otherwise some part of the machine itself must yield, either
by rupture of the hydraulic cylinder, or by the bursting of the
connecting-pipe or the forcing-pump. This result is certain, for the
water refuses to be compressed, at least to any noticeable degree, and
therefore, by making the area of the plunger of the force-pump
sufficiently small, there is no limit to the pressure per square inch
which can be produced in the hydraulic cylinder; or, to speak more
correctly, the limit is reached only when the pressure in the hydraulic
cylinder is equal to the cohesive strength of the material (cast or
wrought iron) of which it is formed. It has been found that when the
internal pressure per square inch exceeds the cohesive or tensile
strength of a rod of the metal 1 in. square (see page 207), no increase
in the thickness of the metal will enable the cylinder to resist the
pressure. Professor Rankine has given the following formula for
calculating the external radius, R, of a hollow cylinder of which the
internal radius is _r_, the pressure per square inch which it is desired
should be applied before the cylinder would yield being indicated by
_p_, while _f_ represents the tensile strength of the materials:

                   R = _r_√((_f_ + _p_)/(_f_ – _p_))

We may see in this formula that as the value of _p_ becomes more and
more nearly equal to _f_, the less does the divisor (_f_ – _p_) become,
and therefore the greater is the corresponding value of R; and when _f_
= _p_, or _f_ – _p_ = 0, the interpretation would be that no value of R
would be sufficiently great to satisfy the equation. Thus a cylinder,
made of cast iron, of which the breaking strain is 8 tons per square
inch, would have its inner surface ruptured by that amount of internal
pressure, and the water passing into the fissures would exert its
pressure with ever-increasing destructive effect.

With certain modifications in the proportions and arrangement of its
parts, the hydraulic press is used for squeezing the juices from
vegetable substances, such as beetroots, &c., for pressing oils from
seeds, and, in fact, all purposes where a powerful, steady, and easily
regulated pressure is needed. Cannons and steam boilers are tested by
hydraulic pressure, by forcing water into them by means of a force-pump,
just as it is forced into the cylinder of the hydraulic press described
above. This mode of testing the strength has several great advantages;
for not only can the pressure be regulated and its amount accurately
known; but in case the cannon or steam boiler should give way, there is
no danger, for it does not explode—the metal is simply ruptured, and the
moment this takes place, the water flows out and the strain at once
ceases.

The strength of bars, chains, cables, and anchors is also tested by
hydraulic power, and the engraving at the head of this article, Fig.
163, represents the hydraulic testing machine at the works of Messrs.
Brown and Lenox, the eminent chain and anchor manufacturers, of
Millwall. Immediately in front of the spectator are the force-pumps, and
the steam engine by which they are driven. It will be observed that four
plungers are attached to an oscillating beam in such a manner that the
water is continuously forced into the hydraulic cylinder. The outer pair
of plungers are of much larger diameter than the inner pair, in order
that the supply of water may be cut off from the former when the
pressure is approaching the desired limit, and the smaller pair alone
then go on pumping in the water, the pressure being thus more gradually
increased. Behind the engine and forcing pump is the massive iron
cylinder, where the pressure is made to act on a piston, which is forced
towards that end of the cylinder seen in the drawing. The piston is
attached to a very thick piston-rod, moving through a water-tight collar
at the other end of the cylinder. The effect of the hydraulic pressure
is, therefore, to draw the piston-rod into the cylinder, and not, as in
the apparatus represented in Fig. 166, to force a plunger out. The head
of the piston-rod is provided with a strong shackle, to which the chains
to be tested can be attached. In a line with the axis of the cylinder is
a trough, some 90 ft. long, to hold the chain, and at the farther end of
the trough is another very strong shackle, to which the other end of the
chain is made fast. A peculiarity of Messrs. Brown and Lenox’s machine
is the mode in which the tension is measured. In many cases it is deemed
sufficient to ascertain by some kind of gauge the pressure of the water
in the hydraulic cylinder, and from that to deduce the pull upon the
chain; but the Messrs. Brown have found that every form of gauge is
liable to give fallacious indications, from variations of temperature
and other circumstances, and they prefer to measure the strain directly.
This is accomplished by attaching the shackle at the farther extremity
of the trough to the short arm of a lever, turning upon hard steel
bearings, the long arm of this lever acting upon the short arm of
another, and so on until the weight of 1 lb. at the end of the last
lever will balance a pull on the chain of 2,240 lbs., or 1 ton. The
tension is thus directly measured by a system of levers, exactly
resembling those used in a common weighing machine, and this is done so
accurately that even when a chain is being subjected to a strain of many
tons, an additional pull, such as one can give to the shackle-link with
one hand, at once shows itself in the weighing-room. The person who has
charge of this part of the machine places on the end of the lever a
weight of as many pounds as the number of tons strain to which the chain
to be tested has to be submitted. The engineer sets the pump in action,
the water is rapidly forced into the cylinder, the piston is thrust
inwards, and the strain upon the chain begins; the engineer then cuts
off the water supply from the larger force-pumps, and the smaller pair
go on until the strain becomes sufficient to raise the weight, and then
the person in the weighing-room, by pulling a wire, opens a valve in
connection with the hydraulic cylinder, which allows the water to
escape, and the strain is at once taken off. This testing machine, which
is capable of testing cables up to 200 tons or more, was originally
designed by Sir T. Brown, the late head of the firm, and not only was
the first constructed in the country, but remains unsurpassed in the
precision of its indications.

The testing of cables, which we have just described, is a matter of the
highest importance, for the failure of cables and anchors places ships
and men’s life in great danger, since vessels have frequently to ride
out a storm at anchor, and should the cables give way, a ship would then
be almost entirely at the mercy of the winds and waves. Hence the
Government have, with regard to cables and anchors, very properly made
certain stringent regulations, which apply not only to the navy but to
merchant shipping. The chain-cable is itself a comparatively modern
application of iron, for sixty years ago our line-of-battle ships
carried only huge hempen cables of some 8 in. or 9 in. diameter.
Chain-cables have now almost entirely superseded ropes, though some
ships carry a hempen cable, for use under peculiar circumstances. The
largest chain-cables have links in which the iron has a diameter of
nearly 3 in., and these cables are considered good and sound when they
can bear a strain of 136 tons. Such are the cables used in the British
navy for the largest ships. Of course, there are many smaller-sized
cables also in use, and the strains to which these are subjected when
they are tested in the Government dockyards vary according to the
thickness of the iron; but it is found that nearly one out of every four
cables supplied to the Admiralty proves defective in some part, which
has to be replaced by a sounder piece. The chain-cables made by Messrs.
Brown and Lenox for the _Great Eastern_ are, as might have been
expected, of the very stoutest construction; the best workmanship and
the finest quality of iron having been employed in their manufacture.
These cables were tested up to 148 tons, a greater strain than had ever
before been applied as a test to any chain, and it was found that a pull
represented by at least 172 tons was required to break them. It is
difficult to believe that a teacup-full of cold water shoved down a
narrow pipe is able to rend asunder the massive links which more than
suffice to hold the huge ship securely to her anchors, but such is
nevertheless the sober fact. The regulations of the Board of Trade
require that every cable or anchor sold for use in merchant ships is to
be previously tested by an authorized and licensed tester, who, if he
finds it bears the proper strain, stamps upon it a certain mark.

The means which is afforded by hydraulic power of applying enormous
pressures has been taken advantage of in a great many of the arts, of
which, indeed, there are few that have not, directly or indirectly,
benefited by this mode of modifying force. An illustration, taken at
random, may be found in the machinery employed at Woolwich for making
elongated rifle-bullets. The bullets are formed by forcing into dies,
which give the required shape, little cylinders of solid lead, cut off
by the machine itself from a continuous cylindrical rod of the metal.
The rod, or rather filament, of lead is wound like a rope on large
reels, from which it is fed to the machine. It is in the production of
this solid leaden rope or filament that hydraulic pressure is used.
About 4 cwt. of melted lead is poured into a very massive iron cylinder,
the inside of which has a diameter of 7½ in., while the external
diameter is no less than 2 ft. 6 in., so that the sides of the cylinder
are actually 11¼ in. thick. When the lead has cooled so far as that it
has passed into a half solid state, a ram or plunger, accurately fitting
the bore of the cylinder, is forced down by hydraulic pressure upon the
semi-fluid metal. This plunger is provided with a round hole throughout
its entire length, and as it is urged against the half solidified metal
with enormous pressure, the lead yields, and is forced out through the
hole in the plunger, making its appearance at the top as a continuous
cylindrical filament, quite solid, but still hot. This is wound upon the
large iron reels as fast as it emerges from the opening in the plunger,
and these reels are then taken to the bullet-shaping machine, which
snips off length after length of the leaden cord, and fashions it into
bullets for the Martini-Henry rifle. The leaden pipes which are so much
used for conveying water and gas in houses are made in a similar manner,
metal being forced out of an annular opening, which is formed by putting
an iron rod, having its diameter of the required bore of the pipe, in
the middle of the circular opening. The lead in escaping between the rod
and the sides of the opening takes the form of a pipe, and is wound upon
large iron reels, as in the former case.

[Illustration:

  FIG. 167.—_Section of Hydraulic Lift Graving Dock._
]

[Illustration:

  FIG. 168.—_Section of Column._
]

Another interesting application of hydraulic power is to the raising of
ships vertically out of the water, in order to examine the bottoms of
their hulls, and effect any necessary repairs. The hydraulic lift
graving dock, in which this is done, is the invention of Mr. E. Clark,
who, under the direction of Mr. Robert Stephenson, designed the
machinery and superintended the raising of the tubes of the Britannia
Bridge, where a weight of 1,800 tons was lifted by only three presses.
The suitability of the hydraulic press for such work as slowly raising a
vessel was doubtless suggested to him in connection with this
circumstance, and the durability, economy, and small loss of power which
occurs in the action of the press, pointed it out as particularly
adapted for this purpose. The ordinary dry dock is simply an excavation,
lined with timber or masonry, from which the tide is excluded by a gate,
which, after the vessel has entered the dock at high water, is closed;
and when the tide has ebbed, and left the vessel dry, the sluice through
which the water has escaped is also closed. In a tideless harbour the
water has to be pumped out of the dock, and this last method is also
adopted even in tidal waters, so that the docks may be independent of
the state of the tides. The lift of Clark’s graving dock is a direct
application of the power of the hydraulic press, and we select for
description the graving dock constructed at the Victoria Docks for the
Thames Graving Dock Company, whose works occupy 26 acres. Fig. 167 is a
transverse section of this hydraulic lift graving dock, in which there
are two rows of cast iron columns, 5 ft. in diameter at the base, where
they are sunk 12 ft. in the ground, and 4 ft. in diameter above the
ground. The clear distance between the two rows is 60 ft., and the
columns are placed 20 ft. apart from centre to centre, sixteen columns
in each row, thus giving a length of 310 ft. to the platform, but
vessels of 350 ft. in length may practically be lifted. The bases of the
columns, one of which is represented in section in Fig. 168, are filled
with concrete, on which the feet of the hydraulic cylinders rest. The
outer columns support no weight, but act merely as guides for the
crossheads attached to the plungers. The height of the columns is 68½
ft., and a wrought iron framed platform connects the columns at the top.
In order that any inequalities in the height of the rams may be
detected, a scale is painted on each column, to mark the positions of
the crossheads. The hydraulic cylinders, which are within these columns,
have solid rams of 10 in. diameter, with a stroke of 25 ft., and on the
tops of these are fastened the crossheads, 7½ ft. long, made of wrought
iron, and supporting at the ends bars of iron, to the other ends of
which the girders of the platform are suspended. The girders are,
therefore, sixteen in number, and together form a gridiron platform,
which can be raised or lowered with the vessel upon it. The thirty-two
hydraulic cylinders were tested at a pressure of more than 3 tons per
square inch. The water is admitted immediately beneath the collars at
the top (this being the most accessible position) by pipes of only ½ in.
diameter, leading from the force-pumps, of which there are twelve, of 1⅞
in. diameter, directly worked by a fifty horse-power steam engine. The
presses are worked in three groups—one of sixteen, and two of eight
presses,—so arranged that their centres of action form a sort of tripod
support, and the presses of each group are so connected that perfect
uniformity of pressure is maintained. The raising of a vessel is
accomplished in about twenty-five minutes, by placing below the vessel a
pontoon, filled in the first instance with water, and then raising the
pontoon with the vessel on it, while the water is allowed to escape from
the pontoon through certain valves; then when the girders are again
lowered, the pontoon, with the vessel on it, remains afloat. Thus in
thirty minutes a ship drawing, say, 18 ft. of water is lifted on a
shallow pontoon, drawing, perhaps, only 5 ft., and the whole is floated
to a shallow dock, where, surrounded with workshops, the vessel, now
high and dry, is ready to receive the necessary repairs. The number of
vessels which can thus be docked is limited only by the number of
pontoons, and thus the same lift serves to raise and lower any number of
ships, which are floated on and off its platform by the pontoons. With a
pressure in the hydraulic cylinders of about 2 tons upon each square
inch, the combined action of these thirty-two presses would raise a ship
weighing 5,000 tons.

Hydraulic power has been used not only for graving docks, as shown in
the above figures, but also for dragging ships out of the water up an
inclined plane. The machinery for this purpose was invented by Mr.
Miller for hauling ships up the inclined plane of “Martin’s slip,” at
the upper end of which the press cylinder is placed, at the same slope
as the inclined plane, and the ship is attached, by means of chains, to
a crosshead fixed on the plunger. Hydraulic power has also been used for
launching ships, and the launch of the _Great Eastern_ is a memorable
instance; for the great ship stuck fast, and it was only by the
application of an immense pressure, exerted by hydraulic apparatus, that
she could be induced to take to the water. Water pressure is also
applied to hoists for raising and lowering heavy bodies, and in such
cases the pressure which is obtained by simply taking the water supply
from an elevated source, or from the water-main of a town, is sometimes
made use of, instead of that obtained by a forcing pump. The lift at the
Albert Hall, South Kensington, by which persons may pass to and from the
gallery without making use of the stairs, is worked by hydraulic
pressure in the manner just mentioned. In such lifts or hoists there is
a vertical cylinder, in which works a leather-packed piston, having a
piston-rod passing upwards through a stuffing-box in the top of the
cylinder. The upper end of the piston-rod has a pulley of 30 in. or 36
in. diameter, attached to it, and round this pulley is passed a chain,
one end of which is fixed, and the other fastened to the movable cage or
frame. So that the cage moves with twice the speed of the piston, and
the length of the stroke of the latter is one-half of the range of the
cage.

Sir William Armstrong has applied hydraulic power to cranes and other
machines in combination with chains and pulleys. His hydraulic crane is
represented by the diagram, Fig. 169, intended to show only the general
disposition of the principal parts of this machine, which is so
admirably arranged that one man can raise, lower, or swing round the
heaviest load with a readiness and apparent ease marvellous to behold.
Here it is proper to mention once for all, that the pressure for the
hydraulic machines is obtained not only by natural heads of water, or by
forcing-pumps worked by hand, but very frequently by forcing-pumps
worked by steam power. It is usual to have a set of three pumps with
their plungers connected respectively with three cranks on one shaft,
making angles of 120° with each other. A special feature of Sir W.
Armstrong’s hydraulic crane is the arrangement by which the engines are
made to be always storing up power by forcing water into the vessel,
_a_, called the “accumulator.” The accumulator—which in the diagram is
not shown in its true position—may be placed in any convenient place
near the crane, and consists of a large cast iron cylinder, _b_, fitted
with a plunger, _c_, moving water-tight through the neck of the
cylinder. To the head of the plunger is attached by iron cross-bars, _d
d_, a strong iron case filled with heavy materials, so as to load the
plunger, _c_, with a weight that will produce a pressure of about 600
lbs. upon each square inch of the inner surface of the cylinder. The
water is pumped into the cylinder by the pumping engines through the
pipe, _f_, and then the piston rises, carrying with it the loaded case,
guided by the timber framework, _g_, until it reaches the top of its
range, when it moves a lever that cuts off the supply of steam from the
pumping engine. When the crane is working the water passes out of the
cylinder, _a_, by the pipe, _h_, and exerts its pressures on the
plungers of the smaller cylinders; and the plunger of the accumulator,
in beginning its descent again, moves the lever in connection with the
throttle-valve of the engine, and thus again starts the pumps, which
therefore at once begin to supply more water to the accumulator. The
latter is, however, large enough to keep all the several smaller
cylinders of the machine at work even when they are all in operation at
once. Fig. 169 shows a sketch elevation and a ground plan of the crane
as constructed to carry loads of 1 ton, but the size of the cylinders is
somewhat exaggerated, and all details, such as pipes, guides, valves,
rods, &c., are omitted. The hydraulic apparatus is entirely below the
flooring—only the levers by which the valves are opened and closed
appearing above the surface. The crane-post, _i_, is made of wrought
iron: it is hollow and stationary; the jib, _k_, is connected with the
ties, _l_, by side-pieces, _n_, which are joined by a cross-piece at
_m_, turning on a swivel and bearing the pulley, _u_. The jib and the
side-pieces are attached at _o_ to a piece turning round the crane-post,
and provided with a friction roller, _p_, which receives the thrust of
the jib against the crane-post; the same piece is carried below the
flooring and is surrounded with a groove, which the links of the chain,
_q_, fit. This chain serves to swing the crane round, and for this
purpose the hydraulic cylinders, _r_, _r´_, come into operation. The
plungers of these have each a pulley, over which passes the chain _q_,
having its ends fastened to the cylinders, so that when, by the pressure
of the water, one plunger is forced out, the other is pushed in, and the
chain passing round the groove at _s_ swings the jib round. The
cylinders are supplied with water by pipes—omitted in the sketch, as are
also those by which the water leaves the cylinders. These pipes are
connected with valves—also omitted on account of the scale of the
diagram being too small to show their details—so that the movement of a
lever, _t_, in one or the other direction at the same time connects one
cylinder with the supply and the other with the exit-pipe. When the
crane is swinging round, the sudden closing of the valves would produce
an injurious shock, and to prevent this relief-valves are provided on
both the supply and exit-pipes communicating with each cylinder. When,
therefore, the valves are closed, the impetus of the jib and its load
acting on the chain, and through that on the plungers, continues to move
the latter, the motion is permitted to take place by the relief-valves
opening, and allowing water to enter or leave the cylinders against the
pressure of the water. There is also a self-acting arrangement by which,
when these plungers have moved to the extent of their range in either
direction, the valves are closed. The chain of the crane rests on guide
pulleys, and passing over the pulley _u_, goes down the centre of the
crane-post to the pulley _v_, and thence passes backwards and forwards
over a series of three pulleys at _w_ and two at _x_, and is fastened at
its end to the cylinder, _y_. As there are thus six lines of chain, when
the plunger of the lifting cylinder comes 1 ft. out, 6 ft. of chain pass
over the guide pulley, _u_. The plunger, when near the end of its stroke
in either direction, is made to move a bar—not shown—which closes the
valve. When the crane is loaded, the load is lowered by simply opening
the exhaust-valve, when the lift-plunger will be forced back into its
cylinder by the pull on the chain. But as the chain may require to be
lowered when there is no load upon it, although a bob is provided at _z_
to draw the chain down, it would be disadvantageous to increase the
weight of this to the extent required for forcing back the lifting
plunger. A _return_ cylinder is therefore made use of, the plunger of
which has but a small diameter, and is connected with the head of the
lift-plunger, so that it forces the latter back when the lift-cylinder
is put in communication with the exhaust-pipe. The water is admitted to
the lifting cylinder from the accumulator by a valve worked by a lever,
which, when moved the other way, closes the communication and opens the
exhaust-pipe, and then the pressure in the return cylinder, which is
constant, drives in the plunger of the lifting cylinder. The principle
of the accumulator may plainly be used with great advantage even when
manual labour is employed, for a less number of men will be required for
working the pumps to produce the effect than if their efforts had to be
applied to the machine only at the time it is in actual operation, for
in the intervals they would, in the last case, be standing idle.
Apparatus on the same plan has been used with advantage for opening and
shutting dock gates, moving swing bridges, turn-tables, and for other
purposes where a considerable power has to be occasionally applied.

[Illustration:

  FIG. 169.—_Sir W. Armstrong’s Hydraulic Crane._
]

[Illustration:

  FIG. 170.—_Raising Tubes of the Britannia Bridge._
]

[Illustration:

  FIG. 171.—_Press for Raising the Tubes._
]

[Illustration:

  FIG. 172.—_Head of Link-Bars._
]

A famous example of the application of hydraulic power was the raising
of the great tubes of the Britannia Bridge. As already stated, the tubes
were built on the shore, and were floated to the towers. This was done
by introducing beneath the tubes a number of pontoons, provided with
valves in the bottom, so as to admit the water to regulate the height of
the tube according to the tide. The great tubes were so skilfully guided
into their position that they appeared to spectators to be handled with
as much ease as small boats. The mode in which they were raised by the
hydraulic presses wall be understood from Fig. 170, where A is one of
the presses and C the tube, supported by the chains, B. The tubes were
suspended in this manner at each end, and as the great tubes weighed
1,800 tons, each press had, therefore, to lift half this weight, or 900
tons. The ram or plunger of the pump was 1 ft. 8 in. in diameter, and
the cylinder in which it worked was 11 in. thick. Two steam engines,
each 40 horse-power, were used to force the water into the cylinders.
These cylinders were themselves remarkable castings, for each contained
no less than 22 tons of iron. Notwithstanding the great thickness of the
metal, an unfortunate accident occurred while the plungers were making
their fourth ascent, for the bottom of one of the cylinders gave way—a
piece of iron weighing nearly a ton and a half having been forced out,
which, after killing a man who was ascending a rope ladder to the press,
fell on the top of the tube 80 ft. below, and made in it a deep
indentation. The accident occasioned a considerable delay in the
progress of the work, for a new cylinder had to be cast and fitted. Such
an accident would assuredly have caused the destruction of the tube
itself but for the foresight and prudence of the engineer in placing
beneath the ends of the vast tube as it ascended slabs of wood 1 in.
thick, so that it was impossible for the tube to fall more than 1 in. It
must be stated that as the tube was lifted each step, the masonry was
built up from below, and then as the next lift proceeded inch by inch, a
slab of wood was placed under the ends. Although by the giving way of
the cylinder of the hydraulic press the end of the tube fell through no
greater space than 1 in., the momentum was such that beams calculated to
bear enormous weights were broken. At the time of the accident the
pressure in the cylinder did not exceed that which it was calculated to
bear or that which is frequently applied in hydraulic presses for other
purposes. Some scientific observers attributed the failure of the
cylinder to the oscillating of the tube. It had been found when the
similar tubes of the bridge over the Conway were being raised, that when
the engines at each end made their strokes simultaneously, a dangerous
undulation was set up in the tube, and it was therefore necessary to
cause the strokes of the engines to take place alternately. The chains
by which the tubes were suspended were made of flat bars 7 in. wide and
about 1 in. thick, being rolled in one piece, with expanded portions
about the “eye,” through which the connecting-bolts pass. The links of
the chain consisted of nine and eight of these bars alternately—the bars
of the eight-fold links being made a little thicker than those of the
nine-fold, so as to have the same aggregate strength. The mode in which
the hydraulic presses were made to raise the tubes is very clearly
described by Sir William Fairbairn in his interesting work on the Conway
and Britannia Bridges, and his account of the mode of raising the tubes
is here given in his own words, but with letters referring to Fig. 171:
“Another great difficulty was to be overcome, and it was one which
presented itself to my mind with great force, viz., in what manner the
enormous weight of the tube was to be kept suspended when lifted to the
height of 6 ft., the proposed travel of the pump, whilst the ram was
lowered and again attached for the purpose of making another lift. Much
time was occupied in scheming means for accomplishing this object, and
after examining several projects, more or less satisfactory, it at last
occurred to me that, by a particular formation of the links (of the
chain by which the tubes were to be suspended) we might make the chains
themselves support the tube. I proposed that the lower part of the top
of each link, immediately below the eye, should be formed with square
shoulders cut at right angles to the body of the link (Fig. 172). When
the several links forming the chain E were put together, these shoulders
formed a bearing surface, or “hold,” for the crosshead B attached to the
top of the ram A of the hydraulic pump. But the upper part of this
crosshead, C C, was movable, or formed of clips, which fitted the
shoulders of the chain, and were worked by means of right- and
left-handed screws, and could be made either to clip the chain
immediately under the shoulders when the ram of the pump was down and a
lift about to be made, or be withdrawn at pleasure. Attached to the
large girders F were a corresponding set of clips, D D, which were so
placed and adjusted as to height that when the ram of the pump was at
the top there was distance between the two sets of clips equal to twice
the length of the travel of the pump, or the length of the two sets of
the links of the chain. To render the action of the apparatus more
clear, suppose the tube resting on the shelf of masonry in the position
that it was left in after the operation of floating was completed, and
the chains attached, and everything ready for the first lift, the ram of
the pump being necessarily down. The upper set of clips attached to the
crosshead are forced under the shoulders of the links, and the lower set
of clips attached to the frames resting upon the girders are drawn back,
so as to be quite clear of the chain; the pumps are put into action
simultaneously at both ends of the tube, and the whole mass is slowly
raised until it has reached a height of 6 ft. from its original
resting-place. The clips attached to the crosshead, B, have so far been
sustaining the weight, but it will be observed that by the time the pump
has ascended to its full travel, the square shoulders of another set of
links have come opposite to the lower clips on the girders, D, and these
clips are advanced under the shoulders of the links, and the rams being
allowed to descend a little, they in their turn sustain the load and
relieve the pumps. The upper clips being withdrawn, the rams are allowed
to descend, and after another attachment, a further lift of 6 ft. is
accomplished; and thus, by a series of lifts, any height may be
attained. The fitness of this apparatus for its work was admirable, and
the action of the presses was, as Mr. Stephenson termed it, delightful.”

[Illustration:

  FIG. 173.—_Apparatus to prove Transmission of Pressure in all
    directions._
]

[Illustration:

  FIG. 174.—_Pneumatic Tubes and Carriages._
]



                          PNEUMATIC DISPATCH.


When the use of the electric telegraph became general, it was found
necessary to establish in all large towns branch stations, from which
messages were conveyed to the central station, or to which they were
sent, either by messengers who carried the written despatch, or by
telegraphing between the central and branch stations. The latter had the
disadvantages of rendering the original message liable to an additional
chance of incorrect transmission, and when an unusually great number of
despatches had to be sent to or from a particular branch station, there
was necessarily great delay in the forwarding of them. The plan of
sending the written messages between the central stations by bearers was
unsatisfactory on account of the time occupied. These inconveniences led
to the invention of a system for propelling, by the pressure of air, the
papers upon which the messages were written through tubes connecting the
stations. This was first carried into practice by the Electric and
International Telegraph Company, who, in this way, connected their
central station in London with their City branch stations. The apparatus
was designed and erected by Mr. L. Clark and Mr. Varley in 1854. The
first tube laid down was from Lothbury and the Stock Exchange—a distance
of 220 yards. This tube had an inside diameter of only 1½ in.; but a
larger tube, having a diameter of 2¼ in. was, some years afterwards,
laid between Telegraph Street and Mincing Lane—a distance of 1,340
yards—and was used successfully. In these tubes the carriers were pushed
forward by the pressure of the atmosphere, a vacuum having been produced
in front by pumping out the air. The plan of propelling the carrier by
compressing the air behind it was also tried with good results, and, in
fact, with a gain of speed; for, while a carrier occupied 60 or 70
seconds in passing from Telegraph Street to Mincing Lane when drawn by a
vacuum, it accomplished its journey in 50 or 55 seconds when it was shot
forwards by compressed air, the difference in pressure before and behind
it being the same in each case. A great deal of trouble was occasioned
when the vacuum system was used, by water being drawn in at the joints
of the pipes. This water sometimes accumulated to such a degree,
especially after wet weather, that it completely overcame the power of
the vacuum to draw the air through it, by lodging in the vertical
portions of the tube, where they passed to the upper floors of the
central station. This was remedied by improving the construction of the
joints, and by arranging a syphon for drawing off any water which might
be present. The best construction of the carrier was another matter
which required some experience to discover. It was found that
gutta-percha, or papier maché covered with felt, was the most efficient
material. The tubes found by Mr. Varley to give the best results were
formed of lead covered externally with iron pipes. The joints were made
perfectly smooth in the inside by means of a heated steel mandrel, on
which they were formed, so that the tube was of one perfectly uniform
bore throughout. An ingenious arrangement was also adopted by which the
air itself was made to do the work of opening and closing the valves,
and even that of removing the carrier from the tube: when, by a
telegraphic bell, rung from the distant station, it was announced that a
carrier was dispatched, the attendant at the receiving station had only
to touch for a second a knob marked “receive,” which put the tube in
communication with the vacuum, in which condition it remained until the
arrival of the carrier, which, by striking against a pad of
india-rubber, released the detent, and thus cut off the vacuum. The
carrier then fell out of the receiver and dropped into a box placed to
catch it. When a carrier was sent, it was placed in the tube, and a
button marked “send” was touched, by which a communication was opened
with a vessel of compressed air and the end of the tube behind the
carrier was immediately closed by a slide, the movements being all
performed by the air itself. On the arrival of the carrier, the boy at
the receiving station rang an electric bell to signal its reception; and
the sender then touched another knob marked “cut off,” which caused the
supply of compressed air to be cut off, and the slide to be withdrawn
from the end of the tube, which was then ready either to receive or send
carriers. By this arrangement there was no waste of power, for the
reservoirs of compressed air or of vacuum were only drawn upon when the
work was actually required to be done.

The tubes laid down by the Telegraph Company are still in active
operation; but at the new Central Telegraph Station the automatic valves
of Messrs. Clark and Varley appear to be dispensed with, and the
attendants perform the work of closing the tube, shutting off the
compressed air, &c., by a few simple movements.

In December, 1869, Messrs. Siemens were commissioned by the
Postmaster-General to lay tubes on their system from the General Post
Office to the Central Telegraph Station; and the work having been
accomplished in February, 1870, and proving perfectly satisfactory after
six weeks’ trial, it was decided to connect in the same manner Fleet
Street and the West Strand office at Charing Cross with the Central
Station. The system proposed by the Messrs. Siemens consisted in forming
a circuit of tubes, through which the carriers might be continually
passing in one direction. The diagram, Fig. 175, will give an idea of
the manner in which it was designed to arrange the tubes between the
Central Telegraph Station and Charing Cross. The arrows indicate the
direction in which the air rushes through the tubes; A is the piston in
the cylinder, and valves are so arranged as to pump air out of the
chamber V, and compress it into the chamber P. This plan has been
departed from, so far as regards the Charing Cross Station, for want of
space there prevented the tube being curved with a radius large enough
to convey the carriers without their being liable to stick, and
consequently, these are not carried round in the tube. The passage of
carriers being stopped here, there are, in point of fact, two tubes: an
“up” tube and a “down” tube. But these are connected by a sharp bend, so
that though the tube is continuous as regards the air current, it is
interrupted as regards the circulation of the carriers. The tubes are of
iron, 3 in. internal diameter, made in lengths of about 19 ft.; and for
the turns and bends, pieces are curved with a radius of 12 ft. Both
lines are laid side by side in a trench at about a foot depth below the
streets. The ends of the adjacent lengths form butt joints, so that the
internal surface is interrupted as little as possible, and there is a
double collar to fasten the lengths together. Arrangements are also made
for removing from the inside of the tubes water or dirt, or matter which
may in any manner have got in.

[Illustration:

  FIG. 175.—_Diagram of Tubes, &c._
]

[Illustration:

  FIG. 176.—_Sending and Receiving Apparatus.—Transverse Section._
]

One special feature of Messrs. Siemens’ invention is the plan by which
the carriers are introduced into and removed from the tube at any
required station without the circulation of the air being interfered
with. The simple yet ingenious mechanism by which this is effected will
be understood from the sections shown in Figs. 176 and 177. The figures
represent the position of the apparatus when placed to receive a
carrier; A´ is the receptacle into which the carrier is shot by the air
rushing from A towards A´´. This receptacle is ᗜ-shaped, the curve of
the Ⅾ corresponding with that of the tube, and the upper flat part
admitting of a piece of plate glass being inserted, through which the
attendant may perceive when a carrier arrives. The progress of the
carrier is arrested by a perforated plate, B, which allows the air to
pass. The ends of this receptacle are fixed in two parallel plates, F
F´, which also receive the ends of the plain cylinder, having precisely
the same diameter as the tube, A. These plates are connected also by
cross-pieces, D E, the whole forming a sort of frame, which turns upon E
as a centre; and according as it is put in the position shown by the
plain line in Fig. 176, or in that indicated by the dotted lines, causes
the receiving tube or the hollow cylinder to form part of the main tube,
the cross-piece, D, serving as a handle for moving the apparatus. It
should be remarked that the plates are made to fit the space cut out of
the main tube with great nicety, otherwise much loss of power would
result from leakage. When the hollow cylinder is in a line with the main
tube, it is plain that the carrier will not be stopped, as the tube is
then continuous and uninterrupted. In this hollow cylinder also the
carrier to be sent is deposited after the rocking frame has been placed
on it, Fig. 177; then, on drawing the handle, the hollow cylinder is
brought into the circuit, and the carrier at once shoots off. To stop a
carrier, the receiving-tube is put in by another movement of the handle,
and when the carrier arrives, it is removed by bringing the open
cylinder, or _through tube_, into the circuit, and thus making the
receiver ready for having the carrier pushed out of it by a rod which is
made to slide out by moving a handle. In order to avoid the obstruction
to the movement of the air which would be caused by the carrier while in
the receiving-tube, a pipe, G, is provided, through which the air
chiefly passes when the perforations of the plate, B, are closed by the
presence of a carrier. In this pipe at H is a throttle-valve, which is
opened by tappets, K, on the rocking frames when the receiver is in
circuit, and again closed when the open tube is substituted. The current
thus suffers no interruption by the action of the apparatus.

[Illustration:

  FIG. 177.—_Receiving Apparatus.—Longitudinal Section._
]

The carriers are small cylinders of gutta-percha, or papier maché,
closed at one end, and provided with a lid at the other. They are
covered with felt or leather, and at the front they are furnished with a
thick disc of drugget or leather, like the leathers of a common
water-pump, but fitting quite loosely in the tube. Such a carrier, being
placed in the tube at the Central Station, Fig. 175, will be carried by
the current in the direction of the arrows to the Charing Cross Station,
where its progress will be interrupted; but according to the original
plan it would continue its journey until it again reached the Central
Station, where it would be intercepted by the diaphragm, Fig. 175. But
the carrier is stopped, if at any station the receiving-tube is placed
in circuit, and this is done when an electric signal indicates to the
station that a carrier intended for it has been dispatched. The tubes
are worked on the “block system,” that is, each section is known to be
clear before a carrier is allowed to enter it, and a bell is provided,
which is struck by a little lever, moved by each carrier in its passage
through, so that the attendant at each station knows when a carrier has
shot along the “through tube” of the station. This mode of working the
tubes renders the liability to accidents much less, but their carrying
power might be increased by dispatching carriers at regular and very
short intervals of time, when the limit would be only in the ability of
the attendants to receive a carrier and open the circuit in sufficient
time to allow the next following one to proceed without stoppage. The
length of the lines of tube laid down on this system, with the times
required for the carriers to traverse them, are stated below, the
pressure and the vacuum being respectively equal to the absolute
pressures of 22 lbs. and 5½ lbs. on each square inch of the reservoirs
during the experiments:

        ┌────────────────────────────────────────┬──────┬──────┐
        │                                        │Yards.│M. S. │
        │Telegraph Station to General Post Office│   852│ 1  54│
        │General Post Office to Temple Bar       │ 1,206│ 2  28│
        │Temple Bar to General Post Office       │ 1,206│ 2  10│
        │General Post Office to Telegraph Station│   852│ 1  13│
        │                                        │ —————│ —————│
        │                                        │ 4,116│ 7  45│
        └────────────────────────────────────────┴──────┴──────┘

When the air was not compressed, but the vacuum only was used, the air
being allowed to enter the other end of the tube at the ordinary
atmospheric pressure, the time required for the carrier to traverse the
circuit was 10 minutes 23 seconds. In this case the vacuum was
maintained, so that the air was constantly in movement; but when the
experiment was tried by allowing the air in the tube to become
stationary, placing a carrier at one end, and then opening communication
with the vacuum reservoir at the other, the carrier required 13½ minutes
to complete the journey. This is explained by the fact of the greater
part of the air having to be exhausted from the tube before the carrier
could be set in motion.

The utility and advantage of the pneumatic system is well seen when its
powers are compared with the wires. Thus, a single carrier, which may
contain, say, twenty-seven messages, can be sent every eight minutes;
and since not more than one message per minute could be transmitted by
telegraph wire, even by the smartest clerks, the real average being
about two minutes for each message, it follows that only four messages
could be sent in the time required for a single carrier to traverse the
up tube, and to do the work which could be done by the tube seven wires
and fourteen clerks would be required.

Mr. R. S. Culley, the official telegraph engineer, states as his
experience of the relative wear and tear of the carriers in these iron
tubes and in the smooth lead tubes, that it had been found necessary to
renew the felt covering of eighty-two dozen of the carriers used for
three months in the iron tubes, while in the same period only
thirty-eight dozen of those used in the lead tubes required to be
recovered. The numbers of carriers sent and received by the pneumatic
tubes on the 21st of November, 1871, between 11 a.m. and 4 p.m., were:

                     Iron tubes             │  135

                     2¼ in. lead tubes 1,170│
                                            │1,697
                     1½ in. lead tubes   527│

The mileage of the carriers sent was much greater in the lead than in
the iron pipes, although the total lengths of each kind were
respectively 5,974 yards and 6,826 yards. The result is remarkable, as
showing the effect of apparently slight differences when their operation
is summed up by numerous repetitions.

The circuit at Charing Cross having been divided on account of the
difficulty mentioned above, the tubes act as separate pipes—one for “up”
traffic (_i.e._, to Central Telegraph Station), the other for “down”
(_i.e._, from the Central Station). The air, however, still accomplishes
a circuit, being exhausted at one end and compressed at the other. A
very noticeable and curious difference is found between the times
required by the carriers to perform the “up” and the “down” journeys:

                 An “up” carrier requires   6·5 minutes
                 A “down” carrier requires 12·5 minutes
                                           ————
                         Together          19·0 minutes

When two pipes were separated at Charing Cross so that the air no longer
circulated from one to the other, but both were left open to the
atmosphere, while the “up” pipe was worked by a vacuum only and the
“down” pipe by pressure only, the times were for

                     An “up” carrier   8·5 minutes
                     A “down” carrier 11·3 minutes
                                      ————
                         Together     19·8 minutes

The time, therefore, for the whole circuit was practically the
same—whether the tubes were worked by a continuous current of air or
separated, and one worked by the vacuum and the other by pressure. It
was also seen that when the tubes were connected so that the air current
was continuous, and the pump producing a vacuum at one end and a
compression at the other, the neutral point where the pressure was equal
to that of the atmosphere was not found midway between the two
extremities—that is, at Charing Cross Station—but much nearer the vacuum
end. When the tubes were disconnected, it appeared, as already shown by
the figures given above, that there was a gain of speed on the down
journey, and a loss of speed on the up journey; and as the requirements
of the traffic happened to require greater dispatch for the down
journeys, the tubes have been worked in this manner.

It has been proposed to convey letters by pneumatic dispatch between the
General and Suburban Post Offices, and the Post Office authorities have
even consulted engineers on the practicability of sending the Irish
mails from London to Holyhead by this system. It was calculated,
however, that although the scheme could be carried out, the proportion
of expense for great speeds and long distances would be enormously
increased. A speed of 130 miles per hour was considered attainable, but
the wear and tear of the carriers would be extremely great at this high
velocity, and it was considered doubtful whether this circumstance might
not operate seriously against the practical carrying out of the plan.
The prime cost would be very great, for the steam power alone which
would be requisite would amount to 390 horse-power for every four miles.
We thus see that very high velocities would introduce a new order of
difficulties in the practical working. The case as regards the velocity
with which electric signals can be sent round the world is very
different.

An amusing hoax appears to have been perpetrated by some waggish
telegraph clerk on an American gentleman at Glasgow, with regard to the
pneumatic system of sending messages; for the gentleman sent to the
“Boston Transcript” a letter, in which he relates that having sent a
telegraphic message from Glasgow to London, he received in a few minutes
a reply which indicated a mistake somewhere, and then he went to the
Glasgow telegraph office, and asked to see his message.

“The clerk said, ‘We can’t show it to you, as we have sent it to
London.’ ‘But,’ I replied, ‘you must have my original paper here. I wish
to see that.’ He again said, ‘No, we have not got it: it is in the post
office at London.’ ‘What do you mean?’ I asked. ‘Pray, let me see the
paper I left here half an hour ago.’ ‘Well,’ said he, ‘if you must see
it, we will get it back in a few minutes, but it is now in London.’ He
rang a bell, and in five minutes or so produced my message, rolled up in
pasteboard.... I inquired if I might see a message sent. ‘Oh, yes; come
round here.’ He slipped a number of messages into the pasteboard scroll,
popped it into the tube, and made a signal. I put my ear to the tube and
heard a slight rumbling noise for seventeen seconds, when a bell rang
beside me, indicating that the scroll had arrived at the General Post
Office, 400 miles off. It almost took my breath away to think of it.”

In the journal called “Engineering,” into which this curious letter was
copied, it is pointed out that to travel from London to Glasgow, a
distance of 405 miles, in seventeen seconds, the carrier must have moved
at the rate of 24 miles per second, or 5 miles a second faster than the
earth moves in its orbit, and the carrier would have in such a case
become red hot by its friction against the tube before it had travelled
a single second.

A plan of conveying, not telegraph messages, but parcels, was proposed
and carried into effect some time ago, and more recently has been
applied to lines of tubes in connection with the General Post Office.
These tubes pass from Euston Station down Drummond Street, Hampstead
Road, Tottenham Court Road, to Broad Street, St. Giles’s, whence, with a
sharp bend, they proceed to the Engine Station at Holborn, and then to
the Post Office. The tube is formed chiefly of cast iron pipes of a
⌓-shaped section, 4 ft. 6 in. wide and 4 ft. high, in 9 ft. lengths.
There are curves with radii of 70 ft. and upwards, and at these parts
the tube is made of brickwork and not of iron. The carriages run on four
wheels, and are so constructed that the ends fit the tubes nearly, and
the interval left is partly closed by a projecting sheet of india-rubber
all round. The carriages are usually sent through the tube in trains of
two or three, and the trains are drawn forward by an exhausting
apparatus formed by a fan, 22 ft. in diameter, worked by two horizontal
steam engines having cylinders 24 in. in diameter and a stroke of 20 in.
The air rushes by centrifugal force from the circumference of the fan,
and is drawn in at the centre, where the exhaust effect is produced. The
tubes which convey the air from the main tube open into the latter at
some distance from its extremities, which are closed by doors, so that
after the carriage passes the entrance of the suction tube, its momentum
is checked by the air included between it and the doors, which air is,
of course, compressed by the forward movement of the carriage. At the
proper moment the doors are opened by a self-acting arrangement, and the
carriage emerges from the tube. There are two lines of tube—an “up” and
a “down” line—and means are provided for rapidly transferring the
carriages from one to the other at the termini. The time occupied in the
transit is about 12 minutes. Some of the inclines have as much slope as
1 in 14, yet loads of 10 or 12 tons weight are drawn up these gradients
without difficulty. The mails are sent between Euston Station and the
Post Office by means of these tubes. Passengers have also made the
journey as an experiment by lying down in the carriages. Fig. 174 shows
one of the carriages and the entrance to the tubes.

Great expectations have been formed by some persons of the applications
of pneumatic force. Some have suggested its use for moving the trains in
the proposed tunnel between England and France. But calculations show
that for long distances and large areas such modes of imparting motion
are enormously wasteful of power. Thus, in the tunnel alluded to it must
be remembered that not only the train, but the whole mass of air in the
tunnel would have to be drawn or pushed forward. The drawing of a train
through by exhausting the air would be very similar to drawing it
through by a rope; in fact, the mass of air may be regarded as a very
elastic rope, but by no means a very light one, or one that could be
drawn through without some opposing force which has a certain
resemblance to friction coming into operation. Indeed, it has been
calculated that in the case named, only five per cent. of the total
power exerted by the engines in exhausting the air could possibly
produce a useful effect in moving the train.

Air has also been made the medium for conveying intelligence in another
manner than by shooting written messages through tubes, for its property
of transmitting pressure has been applied to produce at a distance
signals like those made use of in the electric telegraph system. A few
years ago, an apparatus for this object was contrived by Signor
Guattari, whose invention is known as the “Guattari Atmospheric
Telegraph.” In this there is a vessel charged with compressed air by a
compression-pump, and the pressure is maintained by the same means,
while the reservoir is being drawn upon. A valve is so arranged that the
manipulator can readily admit the compressed air to a tube extending to
the station where the signals are received, at which the pressure is
made to move a piston as often as the sender opens the valve. This
movement is made to convey intelligence when a duly regulated succession
of impulses is sent into the tube—the receiving apparatus being arranged
either to give visible or audible signals, or to print them on slips of
paper, according to any of the methods in use with the electric
telegraph. Certain advantages over the electric system are claimed for
this pneumatic telegraph—as, for example, greater simplicity and less
liability to derangement. The tubes, which are merely leaden piping of
small bore, are also exempt from the inconvenient interruptions which
electric communication sometimes suffers from electrical disturbances in
the atmosphere. The pneumatic system is easily arranged, and from its
great simplicity any person can in a few hours learn to use the whole
apparatus, while it is calculated that the expense of construction and
working would not be above half of that incurred for the electric
system. For telegraphs in houses, ships, warehouses, and short lines,
this invention will doubtless prove very serviceable; but for long lines
a much greater force of compression would be required, and the time
needed for the production of an impulse at the distant ends of the tubes
would be considerably increased. [1875].

[Illustration]

[Illustration:

  FIG. 178.—_The Sommeiller Boring Machines._
]



                              ROCK BORING.


Allusion has already been made to one great characteristic of our age,
namely, the replacement, in every department of industry, of manual
labour by machines. A brief notice of even the main features of the
various contrivances which have been made to take the place of men’s
hands would more than occupy this volume. Accordingly, we must omit all
reference to many branches of manufacture, although the products may be
of very great utility, and the processes of very high interest; and in
taking one example here and another there, we must be guided mainly by
the extent and depth of the influence which the new invention appears
destined to exert. This consideration has, with scarcely an exception,
decided the selection of the topics already discussed, and it has also
determined the introduction of the present article, which relates to
machines of no less general importance than the rest, although at first
sight it might seem to enter upon the details of merely a special branch
of industry. But so general are the interests connected with the subject
we are about to lay before our readers, that we are not sure it would
not have been more logical to have placed the present article before all
the rest. For whence comes the iron of which our steam engines, tools,
rails, ships, cannon, bridges, and printing presses are made?—whence
comes the fuel which supplies force to the engines?—whence come, in
fine, the substances which form the _matériel_ of every art? Plainly
from the earth—the nurse and the mother of all, and in most cases from
the bowels of the earth, for her treasures are hidden far below the
surface—the coal, and the ores of iron and other metals, are not ready
to our hand, exposed to the light of day. The railways also, and the
canals, can be made only on condition that we cut roads through the
solid rocks, and pierce with tunnels the towering mountains. Hence the
tools which enable us to penetrate into the substance of the earth
present the highest general interest from a practical point of view, and
this interest is enhanced by the knowledge of the structure and past
history of our planet acquired in such operations.

The operations by which solid rocks are penetrated in the sinking of
shafts for mines, or in the driving of tunnels, drifts, headings,
galleries, or cuttings for railways, mines, or other works, are easily
understood. In the first place a number of holes—perhaps 3 ft. or 4 ft.
deep and 2 in. or 3 in. in diameter—are formed in the rock. The holes
are then charged with gunpowder or other explosive materials, a
slow-burning match is adjusted, the miners retire to a safe distance,
the explosion takes place—detaching, shattering, and loosening masses of
the rock more or less considerable; and then gangs of workmen clear away
the stones and _débris_ which have been detached by the explosion, and
the same series of operations is renewed. The holes for the blasting
charges are formed by giving repeated blows on the rock with a kind of
chisel called a _jumper_—the end of which is formed of very hard steel,
so that the rock is in reality chipped away. The _débris_ resulting from
this operation is cleared away from time to time by a kind of auger or
some similar contrivance. But for many purposes it is necessary to drill
holes in rocks to great depths, hundreds of feet perhaps, as for
example, in order to ascertain the nature of underlying strata, or to
verify the presence of coal or other minerals before the expense of
sinking a shaft is incurred. These bore-holes were commonly formed in
exactly the same manner as the blast-holes already mentioned, by
repeated blows of a chisel or jumper, which was attached to the end of a
rod; and as the hole deepened, additional lengths of rod were joined on,
and the rods were withdrawn from time to time to admit of the removal of
the _débris_ by augers, or by cylinders having a valve at the bottom.
The reciprocating movement is given to the chisels and rods either by
hand or by steam or water power. When the length of the rods becomes
considerable, of course the difficulty of giving the requisite blows in
rapid succession is greatly increased, for the whole length of rods has
to be lifted each time, and if allowed to fall with too much violence,
the breaking of the chisel or the rods is the inevitable result. The
time requisite for drawing out the rods, removing the fragments chipped
out, and again attaching the rods and lowering, also increases very much
as the bore gets deeper. Messrs. Mather and Platt, the Manchester
engineers, have, in order to obviate these difficulties, constructed
machines in which the chipping or cutting is done by the fall of a tool
suspended from a rope, the great advantage resulting from the
arrangement being the facility and rapidity with which the tools used
for the cutting and for the removal of the _débris_ are lowered to their
work and drawn up. It is necessary in using the jumper, whether in
cutting blast-holes or bore-holes, to give the tool a slight turn after
each blow, in order that the rock may be chipped off all round, and the
action of the tool equalized. Many attempts have been made to drill
rocks after the fashion in which iron is drilled—that is, by drilling
properly so called, in which the tool has a rapid rotary motion. But
even in comparatively soft rock, it is found that no steel can
sufficiently withstand the abrading action of the rock, for the tool
becomes quickly worn, and makes extremely slow progress. We shall have
presently to return to the subject of bore-holes; but now let us turn
our attention to an example which will illustrate the nature and
advantages of the machinery which has in recent times been applied to
work the jumpers by which the holes for blasting are formed.


                        _THE MONT CENIS TUNNEL._

The successful construction, by the direction of Napoleon, of a broad
and easy highway from Switzerland into Italy, crossing the lofty Alps
amid the snows and glaciers of the Simplon, has justly been considered a
feat of skill redounding to the glory of its designers. But we have
recently witnessed a greater feat of engineering skill, for we have seen
the Alps conquered by the stupendous work known as the Mont Cenis
Tunnel. This tunnel is 7½ English miles in length; but it is not the
mere length which has made the undertaking remarkable. The mountain
which is pierced by the tunnel is formed entirely of hard rock, and what
added still more to the apparently impracticable character of the
proposal when first announced was the circumstance that it was quite
impossible to sink vertical shafts, so that the work could not, as in
the usual process, be carried on at several points simultaneously, but
must necessarily be continued from the two extremities only, a
restriction which would occasion a vast loss of time and much expense,
to say nothing of the difficulties of ventilating galleries of more than
three miles in length. The reader must bear in mind that the importance
of this question of ventilation depends not simply on the renewing of
the air contaminated by the respiration of the workmen, but on the quick
removal of the noxious gases produced in the explosions of the blasting
charges. A work surrounded by such difficulties would probably have
never been attempted had not Messrs. Sommeiller and Co. invited the
attention of engineers to an engine of their invention, worked by
compressed air, and capable of automatically working “jumpers” which
could penetrate the hardest rock. These rock-boring machines, having
been examined by competent authorities in the year 1857, were pronounced
so efficient that the execution of the long-spoken-of Alpine tunnel was
at once resolved upon, and before the close of that year the work had
actually been commenced, after a skilful and accurate survey of the
proposed locality had been made, and the direction of the tunnel set
out. The tunnel does not pass through Mont Cenis, although the post road
from St. Michel to Susa passes over part of Mont Cenis, which gives its
name to the pass. The mountain really pierced by the tunnel is known as
the Grand Vallon, and the tunnel passes almost exactly below its summit,
but at a depth the perpendicular distance of which is as nearly as
possible one mile. The northern end of the tunnel is near a village
named Fourneaux.

Pending the construction of the Sommeiller machines, and other machinery
which was to supply the motive force, the work of excavation was
commenced at both ends, in 1857, in the ordinary manner, that is, by
hand labour, and in 1858 surveys of the greatest possible accuracy were
meanwhile made, in order that the two tunnels might be directed so that
they would meet each other in the heart of the mountain. The reader will
at once perceive that the smallest error in fixing on the direction of
the two straight lines which ought to meet each other would entail very
serious consequences. The difficulties of doing this may be conceived
when we remember that the stations were nearly 8 miles apart, separated
by rugged mountains, in a region of snows, mists, clouds, and winds,
over which the levels had to be taken, and a very precise triangulation
effected. So successfully were these difficulties overcome, and so
accurately were the measurements and calculations made, that the
junction of the centre lines of the completed tunnel failed by only a
_few inches_, a length utterly insignificant under the conditions.

The work was carried on by manual labour only, until the beginning of
1861, for it was found, on practically testing the machinery, that many
important modifications had to be made before it could be successfully
employed in the great work for which it was designed. After the
machinery had been set to work, at the Bardonnêche end, breakages and
imperfections of various parts of the apparatus, or the contrivances for
driving it, caused delay and trouble, so that during the whole of 1861
the machines were in actual operation for only 209 days, and the
progress made averaged only 18 in. per day, an advance much less than
could have been effected by manual labour. The engineers, not
disheartened or deterred by these difficulties and disappointments,
encountered them by making improvement after improvement in the
machinery as experience accumulated, so that a wonderful difference in
the rate of progress showed itself in 1862, when the working days
numbered 325, and the average rate of advance was _three feet nine
inches per day_.

At the Fourneaux extremity more time was required for the preparation of
the air-compressing machinery, and the machines had been at work in the
other extremity, with more or less interruption, for nearly two years
before the preparations at Fourneaux were completed.

The illustration at the head of this article, Fig. 178, represents the
Sommeiller machines at work, the motive power being compressed air,
conveyed by tubes from receivers, into which it is forced until the
pressure becomes equal to that of six atmospheres, or 90 lbs. per square
inch. The compression was effected by taking advantage of the natural
heads of water, which were made to act directly in compressing the air;
the pressure due to a column of water 160 ft. high being made to act
upwards, to compress air, and force it through valves into the
receivers; then the supply of water was cut off, and that which had
risen up into the vessel previously containing air was allowed to flow
out, drawing in after it through another valve a fresh supply of air;
and then the operations were repeated by the water being again permitted
to compress the air, and so on, the whole of the movements being
performed by the machinery itself. The compressed air, after doing its
work in the cylinders of the boring tools, escaped into the atmosphere,
and in its outrush became greatly cooled, a circumstance of the greatest
possible advantage to the workmen, for otherwise, from the internal
warmth of the earth, and that produced by the burning of lights,
explosions of gunpowder, and respiration, the heat would have been
intolerable. At the same time, the escaping air afforded a perfect
ventilation of the workings while the machines were in action. At other
times, as after the explosion of the charges, it was found desirable to
allow a jet of air to stream out, in order that the smoke and carbonic
acid gas should be quickly cleared away. Even had the work been done by
manual labour alone, a plentiful supply of compressed air would have
been required merely for ventilation, so that there was manifest
advantage in utilizing it as the motive power of the machines.

[Illustration:

  FIG. 179.—_Transit by Diligence over Mont Cenis._
]

The experience gained in the progress of the work suggested from time to
time many improvements in the machinery and appliances, which finally
proved so effectual that the progress was accelerated beyond
expectation. At the end of 1864, when the machines had been in work
about four years, it was calculated that the opening of the tunnel might
be looked for in the course of the year 1875. But in point of fact it
happened that on the 25th December, 1870, perforator No. 45 bored a hole
from Italy into France, by piercing the wall of rock, about 4 yards
thick, which then separated the workings from each other. The centre
lines of the two workings, as set out from the different sides of the
mountain, failed to coincide by only a foot, that set out on the
Fourneaux side being this much higher than the other, but their
horizontal directions exactly agreeing. The actual length of the tunnel
was found to be some 15 yards longer than the calculated length, the
calculation having given 7·5932 miles for the length, whereas by actual
measurement it was found to be 7·6017 miles. The heights above the
sea-level of the principal points are these:

                                                            Feet.
       Fourneaux, or northern entrance                      3,801
       Bardonnêche, or southern entrance                    4,236
       Summit of tunnel                                     4,246
       Highest point of mountain vertically over the tunnel 9,527

The tunnel is lined with excellent brick and stone arching, and it is
connected with the railways on either side by inclined lines, which are
in part tunnelled out of the mountain, so that the extremities of the
tunnel referred to above are not really entered by the trains at all;
but these lateral tunnels join the other and increase the total distance
traversed underground to very nearly 8 miles, or more accurately, 7·9806
miles. The time required by a train to pass from one side to the other
is about 25 minutes. What a contrast is this to the old transit over the
Mont Cenis pass by “diligence”! We have the scene depicted in Fig. 179,
where we perceive, sliding down or toiling up the steep zigzag ascents,
a series of curious vehicles drawn by horses with perpetually jingling
bells.

The cost of the Mont Cenis Tunnel was about £3,000,000 sterling, or
upwards of £200 per yard; but as a result of the experience gained in
this gigantic work, engineers consider that a similar undertaking could
now be carried out for half this cost. It is supposed that the profit to
the contractors for the Mont Cenis Tunnel was not much less than £100
per yard. The greatest number of men directly employed on the tunnel at
one time was 4,000, and the total horse-power of the machinery amounted
to 860. From 1857 to 1860, by hand labour alone, 1,646 metres were
excavated; from 1861 to 1870 the remaining 10,587 metres were completed
by the machines. The most rapid progress made was in May, 1865, in which
month the tunnel was driven forward at one end the length of 400 feet.
When the workings were being carried through quartz, a very hard rock,
the speed was greatly reduced—as, for example, during the month of
April, 1866, when the machines could not accomplish more than 35 ft.

The perforators used in the Mont Cenis Tunnel were worked by compressed
air, conveyed to a small cylinder, in which it works a piston, to the
rod of which the jumper is directly attached. The air, being admitted
behind the piston, impels the jumper against the rock, and the tool is
then immediately brought back by the opening of a valve, which admits
compressed air in front of the piston, at the same time that the air
which has driven it forward is allowed to escape, communication with the
reservoir of compressed air having previously been closed behind it. The
whole of these movements are automatic, and they are effected in the
most rapid manner, four or five blows being struck in every second, or
between two and three hundred in one minute. Water was constantly forced
into the holes, so as to remove the _débris_ as quickly as it was
formed. A number of these machines were mounted on one frame, supported
on wheels, running on the tramway which was laid along the gallery. The
perforators had no connection with each other, for each one had its own
tube for the conveyance of compressed air, and its own tube to carry the
water used for clearing out the hole, and the cylinders were so fixed on
the frames that the jumpers could be directed in any desired manner
against any selected portion of the rock. They were driven to an average
depth of about 2½ ft., and the process occupied from forty to fifty
minutes. When a set of holes had thus been formed, the cylinders were
shifted and another series commenced, until about eighty holes had been
bored, the formation of the whole number occupying about six or seven
hours, and the holes being so arranged that the next operation would
detach the rock to the required extent. The flexible tubes, which
conveyed the air and water to the machines from the entrances, were then
removed from the machines and stowed away, the frame bearing the
perforators was drawn back along the tramway, workmen advanced whose
duty it was to wipe out the holes, charge them with powder, and fix the
fuses ready for the explosion. When the slow-burning match was ignited,
all retired behind strong wooden barricades, at a safe distance, until
the explosion had taken place; and after the compressed air had been
allowed to stream into the working, so as to clear away all the smoke
and gas generated by the explosion, the workmen ran up on a special
tramway the waggons which were to carry away all the detached stones;
and when this had been done, the floor was levelled, the tramways were
lengthened, and the frame bearing the drilling machines was brought up
to begin a fresh series of operations, which were usually repeated about
twice in the course of every twenty-four hours. A great part of the rock
consists of very hard calcareous schist, interspersed with veins of
quartz, one of the hardest of all rocks, which severely tries the temper
of the steel tools, for a few blows on quartz will not unfrequently
cause the point of a jumper to snap off.


                       _ROCK-DRILLING MACHINES._

Several forms of rock-drills, or perforators, have been constructed on
the same principle as that used in the Mont Cenis Tunnel, and a
description of one of them will give a good notion of the general
principle of all. We select a form devised by Mr. C. Burleigh, and much
used in America, where it has been very successfully employed in driving
the Hoosac Tunnel, effecting a saving in the cost of the drilling
amounting to one-third of the expense of that operation, and effecting
also a still greater saving of time, for the tunnel, which is 5 miles in
length, is to be completed in four years, instead of twelve, as the
machines make an advance of 150 ft. per month, whereas the rate by hand
labour was only 49 ft. per month. These machines are known as the
“Burleigh Rock Drills,” and have been patented in England for certain
improvements by Mr. T. Brown, who has kindly supplied us with the
following particulars:

[Illustration:

  FIG. 180.—_Burleigh Rock Drill on Tripod._
]

The Burleigh perforator acts by repeated blows, like Bartlett and
Sommeiller’s, but its construction is more simple, and the machine is
lighter and not half the size, while its action is even superior in
rapidity and force. The Burleigh machines are composed of a single
cylinder, the compressed air or steam acting directly on the piston,
without the necessity of flywheel, gearing, or shafting. The regular
rotation of the drills is obtained by means of a remarkably simple
mechanical contrivance. This consists of two grooves, one rectilinear,
the other in the form of a spiral cut into the piston-rod. In each of
these channels, or grooves, is a pin, which works freely in their
interior: these pins are respectively fixed to a concentric ring on the
piston-rod. A ratchet wheel holds the ring, and the pin slides into the
curve, causing it to turn always in the same direction, without being
able to go back. By this eminently simple piece of mechanism, the
regular rotation of the drill-holder is secured. The slide-valve is put
into motion by the action of a projection, or ball-headed piston-rod, on
a double curved momentum-piece, or trigger, which is attached to the
slide-rod or spindle by a fork, thus opening and shutting the valve in
the ascent and descent of the piston. Fig. 180 represents one of the
machines attached in this instance by a clamp to the frame of a tripod.
The principal parts of the machine are the cylinder, with its piston,
and the cradle with guide-ways, in which the cylinder travels. The
action of the piston is similar to that of the ordinary steam hammer,
with this difference, that, in addition to the reciprocating, it has
also a rotary, motion. The drill-point is held in a slip-socket, or
clamp, at the end of the piston-rod, by means of bolts and nuts. The
drill-point rotates regularly at each stroke of the piston, making a
complete revolution in every eighteen strokes. For hard rocks it is
generally made with four cutting edges, in the form of a St. Andrew’s
cross, thus striking the rock in seventy-two places in one revolution,
each cutting edge chipping off a little of the stone at each stroke in
advance of the one preceding. The jumper makes, on an average, 300 blows
per minute, and such is the construction of the machine, that the blows
are of an elastic, and not of a rigid, nature, thus preventing the
drill-point from being soon blunted. It has been found in practice, that
a drill-point used in the Burleigh machine can bore on an average 20 ft.
of Aberdeen granite without re-sharpening. As the drill pierces the
rock, the machine is fed down the guide-ways of the cradle by means of
the feed-screw (see Fig. 180), according to the nature of the rock and
the progress made. When the cylinder has been fed down the entire length
of the feed-screw, and if a greater depth of hole is required, the
cylinder is run back, and a longer drill is inserted in the socket at
the end of the piston-rod. The universal clamp may be attached to any
form of tripod, carriage, or frame, according to the requirements of the
work to be done; it enables the machines to work vertically,
horizontally, or at any angle.

The following advantages are claimed for this machine: Any labourer can
work it; it combines strength, lightness, and compactness in a
remarkable degree, is easily handled, and is not liable to get out of
order. No part of the mechanism is exposed; it is all enclosed within
the cylinder, so there is no risk of its being broken. It is applicable
to every form of rockwork, such as tunnelling, mining, quarrying, open
cutting, shaft-sinking, or submarine drilling; and in hard rock, like
granite, gneiss, ironstone, or quartz, the machine will, according to
size, progress at the incredible rate of _four inches_ to _twelve inches
per minute_, and bore holes from ¾ in. up to 5 in. diameter. It will, on
an average, go through 120 ft. of rock per day, making forty holes, each
from 2 ft. to 3 ft. deep, and it can be used at any angle and in any
direction, and will drill and clear itself to any depth up to 20 ft.

The following extract from the “Times,” September 24th, 1873, gives an
account of some experiments with the machine, made at the meeting of the
British Association in that year, before the members of the Section of
Mechanical Science:

“Yesterday, considerable interest was taken in this section, as it had
been announced that a ‘Burleigh Rock Drilling Machine’ would be working
during the reading of a paper by Mr. John Plant. The machine was not,
however, in the room, but was placed in the grounds outside, where it
was closely examined by the members after the adjournment, and seen in
full operation, boring into an enormous block of granite. The aspect of
the machine cannot be called formidable in any respect, for it looks
like a big garden syringe, supported upon a splendid tripod; but when at
work, under about 80 lbs. pressure of compressed air, it would be deemed
a very revolutionary agent indeed, against whose future power the
advocates for manual labour in the open quarry, the tunnel, and even the
deep mine, may well look aghast. Placed upon a block of granite a yard
deep, the machine was handled and its parts moved by the fair hands of
many of the lady associates of scientific proclivities; but once the
source of power was turned on, the drill began its poundings, eating
holes 2 in. in diameter in the block of granite, and making a honeycomb
of it as easily as a schoolboy would demolish a sponge cake. It pounds
away at the rate of 300 strokes, and progresses forward about 12 in., in
the minute, making a complete revolution of the drill in eighteen
strokes, and keeping the hole free of the pounded rock. The machine was
fixed to work at any angle, almost as readily as a fireman can work his
hose; and its adaptation to a wide range of stone-getting, by drilling
for blasting, and cutting large blocks for building and engineering,
with a saving of capital and labour, was admitted by many members of the
section. The tool is called the ‘Burleigh Rock Drill,’ invented by Mr.
Charles Burleigh, a gentleman hailing from Massachusetts, United States.
The patent is the property of Messrs. T. Brown and Co., of London. The
principal feature of this new machine is, that it imitates in every way
the action of the quarryman in boring a hole in the rock.”

[Illustration:

  FIG. 181.—_Burleigh Rock Drill on Movable Column._
]

Many forms of carriages and supports have, from time to time, been made
to suit the work for which the ‘Burleigh’ machines have been required.
The machine is attached to these carriages, or supports, by means of the
universal clamp, by which it can be worked in any direction and at any
angle. Of these carriages we select for notice only two forms, one of
which is shown in Fig. 181. This carriage can be used to great advantage
in adits and drifts. It consists of an upright column, with a screw
clamp-nut for holding and raising or lowering the machine, the whole
being mounted on a platform which can slide right across the carriage,
and thus the machine can be brought to work on any point of a heading.
It is secured in position by means of a jack-screw in the top of the
column; and as the carriage is mounted on wheels, it is easily moved to
permit of blasting. Fig. 182 represents a carriage which is the result
of many years’ experience with mining machinery, and it is considered a
very perfect appliance. It is constructed of wood and iron, and it runs
on wheels. The supports for the machines, four of which may be mounted
at once, are two horizontal bars, the lower of which can be raised or
lowered, as may be necessary. The two parallel sides of the carriage are
joined only at the upper side, and there is nothing to prevent it from
being run into the heading, though the way between the rails may be
heaped up with broken rock, if only the rails are clear. Drilling, and
the removal of the broken rock, may then proceed simultaneously; for, by
means of a narrow gauge inside the carriage rails, small cars may be
taken right up to the _débris_. It is made in different sizes, to suit
the dimensions of the tunnel required. To give the carriage steadiness
in working, it is raised from the wheels by jack-screws, and held in
position by screws in a similar manner to the carriage represented in
Fig. 181.

[Illustration:

  FIG. 182.—_Burleigh Rock Drills mounted on a Carriage._
]

[Illustration:

  FIG. 183.
]

An extremely interesting system of drilling rocks—totally different from
that on which the machines we have just described are constructed—has,
within the last few years, been introduced by Messrs. Beaumont and
Appleby. What does the reader think of boring holes in rocks with
diamonds? It has long been a matter of common knowledge that the diamond
is the hardest of all substances, and that it will scratch and wear down
any other substances, while it cannot itself be scratched or worn by
anything but diamond. In respect to wearing down or abrading hard
stones, the diamond, according to experiments recently made by Major
Beaumont, occupies a position over all other gems and minerals to a
degree far beyond that which has been generally attributed to it; for in
these experiments it was found that on applying a diamond, or rather a
piece of the “carbonate” about to be described, fixed in a suitable
holder, to a grindstone in rapid rotation, the grindstone was quickly
worn down; but on repeating a similar experiment with sapphires and with
corundum, it was these which were worn down by the grindstone. Without,
on the present occasion, entering into the natural history of the
diamond, we may say that there are, besides the pure colourless
transparent crystals so highly prized as gems, several varieties of
diamond, and that those which are tinged with pink, blue, or yellow, are
far from having the same value for the jeweller. Then there is another
impure variety called _boort_, which appears to be employed only to
furnish a powder by which the brilliants are ground and polished. In the
diamond gravels of Brazil, from which we derive our regular supply of
these gems, there was discovered in 1842 a curious variety of
dark-coloured diamond, in which the crystalline cleavage, or tendency to
split in certain directions (which belongs to the ordinary stones),
appears to be almost absent; and the substance might be regarded as a
transition form between the diamond and graphite but for its hardness.
This substance was until lately used for the same purposes as _boort_,
which is a nearer relative of the pure crystal, and like it, splits
along certain planes. It received from the miners the name of
“_carbonado_,” and with regard to the application we are considering, it
has turned out to be a sort of Cinderella among diamonds; for its
unostentatious appearance is more than compensated for by its surpassing
all its more brilliant sisters in the useful property to which reference
has been made. This Brazilian term is doubtless the origin of the
English name by which the substance in question is known among the
English diamond merchants, who call it “carbonate”—an unfortunate word,
for it is used in chemistry with an entirely different signification.
“Carbonate” it is, however, which supplies the requirements of the
rock-drill, and the selected stones are set in a crown, or short tube,
of steel, represented by _c_ in Fig. 183. In this they are secured as
follows: holes are drilled in the rim of the tube, and each hole is then
cut so that a piece of the diamond exactly fits it, and when this piece
has been inserted, the metal is drawn round by punches, so as almost to
cover the stone, leaving only a point projecting, _b b_. The portions of
the crown between the stones are somewhat hollowed out, as at _a_, for a
purpose which will presently be mentioned. The crown thus set with the
boring gems is attached to the end of a steel tube, by which it is made
to rotate with a speed of about 250 revolutions per minute while pressed
against the rock to be bored. Water is forced through the steel tube,
and passing out between the rock and the crown, especially under the
hollows, _c c_, makes its escape between the outside of the boring-tube
and the rock, thus washing away all the _débris_ and keeping the drill
cool. The pressure with which the crown is forced forward depends, of
course, on the nature of the rock to be cut, and varies from 400 lbs. to
800 lbs. In this way the hardest rocks are quickly penetrated—sometimes,
for example, at the rate of 4 in. per minute, compact limestone at 3
in., emery at 2 in., and quartz at the rate of 1 in. per minute. It is
found that, even after boring through hundreds of feet of such
materials, the diamonds are not in the least worn, but as fit for work
as before: they are damaged only when by accident one of the stones gets
knocked out of its setting; and this machine surpasses all in the
rapidity with which it eats its way through the firmest rocks. This, it
must be observed, is the special privilege of the diamond drill—that,
since the begemmed steel crown and the boring-rods are alike tubular,
the rock is worn away in an annular space only, and a solid cylinder of
stone is detached from the mass, which cylinder passes up with the
hollow rods, where, by means of certain sliding wedges, it is held fast,
and is drawn away with the rods.

When the diamond drill is used merely for driving the holes for
blasting, this cylinder of rock is not an important matter; but there is
an application of the drill where this cylinder is of the greatest
value, furnishing as it does a perfect, complete, and easily preserved
section of the whole series of strata through which the drill may pass
when a bore-hole is sunk in the operation of searching for minerals
(which is so significantly called in the United States “prospecting,” a
phrase which seems to be making its way in England in mining
connections); for the core is uniformly cylindrical, the surface is
quite smooth, and any fossils which may be present come up uninjured, so
far as they are contained in the solid core, and thus the strata are
readily recognized. Contrast this with the old method, where the
bore-hole in prospecting is made by the reciprocating action imparted to
a steel tool, and merely the _pounded_ material is obtained, usually in
very small fragments, by augers or sludge-pumps: the fossils, which
might afford the most valuable indications, crushed and perhaps
incapable of being recognized; and instead of the beautifully definite
and continuous cylinder, a mere mass of _débris_ is brought up. In the
prospecting-bores the diameter of the hole is from 2 in. to 7 in. The
size adopted depends on the nature of the strata to be penetrated, and
on the depth to which it is proposed to carry the boring. When the
strata are soft, the operation is commenced with a bore of 7 in., and
when this has been carried to an expedient depth, the danger of the
sides of the hole falling in is avoided by putting down tubes, and then
the diamond drill, fixed to tubes of a somewhat smaller diameter, will
be again inserted, and the boring recommenced; or the hole can be
widened, so as to receive the lining-tubes. Of course, in boring through
hard rocks, such as compact limestones, sandstone, &c., no lining-tubes
are necessary.

In a very interesting paper, read before the members of the Midland
Institute of Mining Engineers, by Mr. J. K. Gulland, the engineer of the
Diamond Rock-Boring Company, who have the exclusive right of working the
patents for this remarkable invention, that gentleman concludes by
remarking that “the leading feature of the diamond drill is that it
works without percussion, thus enabling the holing of rocks to be
effected by a far simpler class of machinery than any which has to
strike blows. Every mechanical engineer knows, often enough to his cost,
that he enters upon a new class of difficulties when he has to recognize
it as a normal state of things with any machinery he is designing that
portions of it are brought violently to rest. These difficulties
increase very much when the power, as in the case of deep bore-holes,
has to be conveyed for a considerable distance. Where steel is used a
percussive action is necessitated, as, if a scraping action is used, the
drill wears quicker than the rock. The extraordinary hardness of the
diamond places a new tool in our hands, as its hardness, compared with
ordinary rock, say granite, is practically beyond comparison. Putting
breakages on one side, a piece of “carbonate” would wear away thousands
of times its own bulk of granite. Irrespective of the private and
commercial success which this invention has attained, it is a boon to a
country such as ours, where minerals constitute in a great measure our
national wealth and greatness.”

The advantages of the diamond drill may be illustrated by the case of
what is termed the Sub-Wealden Exploration. From certain geological
considerations, which need not be entered upon here, several eminent
British and continental geologists have arrived at the conclusion that
it is probable that coal underlies the Wealden strata of Kent and
Sussex, and that it may be perhaps met with at a workable depth. If such
should really prove to be the case, the industrial advantages to the
south of England would be very great, for the existence of coal so
comparatively near to the metropolis would prove not only highly
lucrative to the owners of the coal, but confer a direct benefit upon
thousands by cheapening the cost of fuel. A number of property owners
and scientific men, having resolved that the matter should be tested by
a bore, raised funds for the purpose, and a 9 in. bore had been carried
down to a depth of 313 ft. in the ordinary manner, when a contract was
entered into with the Diamond Rock-Boring Company for a 3 in. bore
extracting a cylinder of rock 2 in. in diameter. The company, as a
precautionary measure, lined the old hole with a 5 in. steel tube; and
in spite of some delay caused by accidents, they increased the depth of
the hole to 1,000 ft. in the interval from 2nd February, 1874, to 18th
June, 1874–-the progress of the work being regarded with the greatest
interest by the scientific world. Unfortunately, the further progress of
the work has been prevented by an untoward event, namely, the breaking
of the boring-rod, or rather tube; and, although the company is prepared
with suitable tackle for extracting the tubes in case of accidents of
this kind, and generally succeeds in lifting them by a taper tap, which,
entering the hollow of the tube, lays hold of it by a few turns—yet, in
this instance, where there have been special difficulties, the
extraction of so great a length of tubes is, as the reader may imagine,
by no means an easy task. Six attempts have been made to remove the
boring-rods which have dropped down; but so difficult has this operation
proved, that, all these efforts having failed, it has been decided to
abandon the old work and commence a new boring on an adjacent spot. A
contract has been entered into with the Diamond Boring Company, who have
undertaken to complete the first 1,000 ft. for £600, which is only £200
more than it would have cost to completely line the old bore-holes with
iron tubes—an operation which was contemplated by the committee in
charge of the exploration. The terms agreed to by the company are very
favourable to the promoters of the Sub-Wealden Exploration, although the
cost of the second 1,000 ft. will be £3,000 more; and the committee are
relying upon the public for contributions to enable them to carry on
their enterprise. It is most probable that funds will be forthcoming,
and should the boring result in the finding of coal measures beneath the
Wealden strata, all the nation will be the richer and participate in the
advantages resulting from an undertaking carried on by private persons.
Already a totally unexpected source of wealth has been met with by the
old bore showing the existence of considerable beds of gypsum in these
strata, and the deposits of gypsum are about to be worked. Whether coal
be found or not found, there is no doubt that a bore-hole going down
2,000 ft. will greatly increase our geological knowledge, and may reveal
facts of which we have at present no conception.

[Illustration:

  FIG. 184.—_The Diamond Drill Machinery for deep Bores._
]

The boring-tubes, it maybe remarked, are made in 6 ft. lengths, and are
so contrived that the joints are nearly flush—that is, there is no
projection at the junctions of the tubes. Fig. 184 is engraved from a
photograph of the machinery used for working the diamond drill when
boring a hole for “prospecting.” This looks at first sight a very
complicated machine, but in reality each part is quite simple in its
action, and is easily understood when its special purpose has been
pointed out. We cannot, however, do more than indicate briefly the
general nature of the mechanism. The reader will on reflection perceive
that, although the idea of causing a rod to rotate in a vertical hole
may be simple, yet in practically carrying it out a number of different
movements and actions have to be provided for in the machinery. The
weight of the rods cannot be thrown on the cutters, nor borne by the
moving parts of the machine—hence the movable disc-shaped weights
attached to the chains are to balance the weight of the boring-rods as
the length of the latter is increased. There must also be a certain
amount of _feed_ given to the cutters, regulated and adjusting itself to
avoid injurious excess: hence a nut which feeds the drill is encircled
by a friction-strap in which it merely slips round without advancing the
cutter when the proper pressure is exceeded. There must be means of
throwing this into or out of gear, or advancing the tool in the work and
of withdrawing it—hence the handles seen attached to the brake-straps.
Water must be drawn from some convenient source, and caused to pass down
the drill-tube—hence the force-pump seen in the lowest part of the
figure. The rods must be raised by steam power and lowered by mechanism
under perfect control—hence suitable gearing is provided for that
purpose.

The reader may be interested in learning what is the cost of
“prospecting” with this unique machinery. The company usually undertake
to bore the first 100 ft. for £40, but the next 100 ft. cost £80–-that
is, for 200 ft. £120 would be charged; the third 100 ft. would cost
£120–-that is to say, the first 300 ft. would cost £240, and so on—each
lower 100 ft. costing £40 more than the 100 ft. above it. Some of the
holes bored have been of very great depth, and have been executed in a
marvellously short space of time. Thus, in 54 days, a depth of 902 ft.
was reached at Girrick in a boring for ironstone; another for coal at
Beeston reached 1,008 ft.; and at Walluff in Sweden 304½ ft. were put
down in one week!

These machines are peculiarly suitable for submarine boring, for they
work as well under water as in the air; and they will no doubt be put
into requisition in the preliminary experiments about to be made for
that great project which bids fair to become a sober fact—the Channel
Tunnel between England and France; and as, by the time these pages will
be before the public, the work of the greatest and boldest rock-boring
yet attempted will have commenced, and the scheme itself will be the
theme of every tongue, the Author feels that the present article would
be incomplete without some particulars of the great enterprise. [1875.]


                         _THE CHANNEL TUNNEL._

The notion of connecting England and France by a submarine line of
railways is not of the latest novelty, but has been from time to time
mooted by the engineers of both countries. The most carefully prepared
scheme, however, is embodied in the joint propositions of Sir J.
Hawkshaw and Messrs. Brunlees and Low among English engineers; and those
of M. Gamond on the French side, which these gentlemen have prepared at
the invitation of the promoters of the scheme, give the clearest and
most authentic account of the considerations on which this gigantic
enterprise will be based, and from this document we draw the following
passages:

    The undersigned engineers, some of whom have been engaged for a
    series of years in investigating the subject of a tunnel between
    France and England, having attentively considered those
    investigations and the facts which they have developed, beg to
    report thereon jointly for the information of the committee.

    These investigations supported the theory that the Straits of
    Dover were not opened by a sudden disruption of the earth at that
    point, but had been produced naturally and slowly by the gradual
    washing away of the upper chalk; that the geological formations
    beneath the Straits remained in the original order of their
    deposit, and were identical with the formations of the two shores,
    and were, in fact, the continuation of those formations.

    Mr. Low proposed to dispense entirely with shafts in the sea, and
    to commence the work by sinking pits on each shore, driving
    thence, in the first place, two small parallel driftways or
    galleries from each country, connected at intervals by transverse
    driftways. By this means the air could be made to circulate as in
    ordinary coal-mines, and the ventilation be kept perfect at the
    face of the workings.

    Mr. Low laid his plans before the Emperor of the French in April,
    1867, and in accordance with the desire of his Majesty, a
    committee of French and English gentlemen was formed in
    furtherance of the project.

    For some years past Mr. Hawkshaw’s attention has been directed to
    this subject, and ultimately he was led to test the question, and
    to ascertain by elaborate investigations whether a submarine
    tunnel to unite the railways of Great Britain with those of France
    and the Continent of Europe was practicable.

    Accordingly, at the beginning of the year 1866, a boring was
    commenced at St. Margaret’s Bay, near the South Foreland; and in
    March, 1866, another boring was commenced on the French coast, at
    a point about three miles westward of Calais; and simultaneously
    with these borings an examination was carried on of that portion
    of the bottom of the Channel lying between the chalk cliffs on
    each shore.

    The principal practical and useful results that the borings have
    determined are that on the proposed line of the tunnel the depth
    of the chalk on the English coast is 470 ft. below high water,
    consisting of 175 ft. of upper or white chalk and 295 ft. of lower
    or grey chalk; and that on the French coast the depth of the chalk
    is 750 ft. below high water, consisting of 270 ft. of upper or
    white chalk and 480 ft. of lower or grey chalk; and that the
    position of the chalk on the bed of the Channel, ascertained from
    the examination, nearly corresponds with that which the geological
    inquiry elicited.

    In respect to the execution of the work itself, we consider it
    proper to drive preliminary driftways or headings under the
    Channel, the ventilation of which would be accomplished by some of
    the usual modes adopted in the best coal-mines.

    As respects the work itself, the tunnel might be of the ordinary
    form, and sufficiently large for two lines of railway, and to
    admit of being worked by locomotive engines, and artificial
    ventilation could be applied; or it might be deemed advisable, on
    subsequent consideration, to adopt two single lines of tunnel. The
    desirability of adopting other modes of traction may be left for
    future consideration.

Such are the essential passages of the report which, in 1868, was
submitted to the Government of the Emperor Louis Napoleon, and was made
the subject of a special commission appointed by the Emperor to inquire
into the subject in all its bearings. The commission presented its
report in 1869, and these are the chief conclusions contained in it:

    I. The commission, after having considered the documents relative
    to the geology of the Straits, which agree in establishing the
    continuity, homogeneity, and regularity of level of the _grey
    chalk_ between the two shores of the Channel,

    Are of opinion that driving a submarine tunnel in the lower part
    of this chalk is an undertaking which presents reasonable chances
    of success.

    Nevertheless they would not hide from themselves the fact that its
    execution is subject to contingencies which may render success
    impossible.

    II. These contingencies maybe included under two heads: either in
    meeting with ground particularly treacherous—a circumstance which
    the known character of the grey chalk renders improbable; or in an
    influx of water in a quantity too great to be mastered, and which
    might find its way in either by infiltration along the plane of
    the beds, or through cracks crossing the body of the chalk.

    Apart from these contingencies, the work of excavation in a soft
    rock like grey chalk appears to be relatively easy and rapid; and
    the execution of a tunnel, under the conditions of the project, is
    but a matter of time and money.

    III. In the actual state of things, and the preparatory
    investigations being too incomplete to serve as a basis of
    calculation, the commission will not fix on any figure of expense
    or the probable time which the execution of the permanent works
    would require.

The chart, Fig. 185, and the section, Fig. 186, will give an idea of the
course of the proposed tunnel, which will connect the two countries
almost at the nearest points. The depth of the water in the Channel
along the proposed line nowhere exceeds 180 ft.—little more than half
the height of St. Paul’s Cathedral, which building would, therefore, if
sunk in the midst of the Channel, still form a conspicuous object rising
far above the waves. But the tunnel will pass through strata at least
200 ft. below the bottom of the Channel, rising towards each end with a
moderate gradient; and from the lower points of these inclines the
tunnel will rise slightly with a slope of 1 in 2,640 to the centre, or
just sufficient for the purposes of drainage. On the completion of the
tunnel a double line of rails will be laid down in it, and trains will
run direct from Dover to Calais. Companies have already been formed in
England under the presidency of Lord Richard Grosvenor, and in France
under that of M. Michel Chevalier, and the legislation of each country
has sanctioned the enterprise. Verily the real magician of our times is
the engineer, who, by virtually abolishing space, time, and tide, is
able to transport us hither and thither, not merely one or two—almost
like the magicians we read of in the “Arabian Nights,” with their
enchanted horses or wonderful carpets—but by hundreds and by tens of
hundreds.

[Illustration:

  FIG. 185.—_Chart of the Channel Tunnel._
]

The “Daily News” of January 22nd, 1875, in presenting its readers with a
chart of the proposed tunnel, offered also the following sensible and
interesting comment on the subject:

“This long-debated project has at length emerged from the region of
speculation, and is entering the stage of practical experiment. On this
side the Channel a company has been formed to carry out the work, and on
the other side the French Minister of Public Works has presented to the
Assembly a Bill authorizing a French company to co-operate with the
English engineers. The enterprise is one worthy of the nations which
have in the present generation joined the two shores of the Atlantic by
an electric cable, and cut a ship canal through the Isthmus of Suez, and
of the age which has obliterated the old barrier of the Alps. All these
gigantic undertakings seemed almost as bold in conception and as
difficult of execution as the great work now about to commence. Those
twenty miles of sea have long been crossed by telegraph lines; they will
soon be bridged, as it were, by splendid steamers; but even our own
generation, accustomed as it is to gigantic engineering works, has
scarcely regarded the construction of a railway underneath the waves as
within the reach of possibility. M. Thomé de Gamond, who first made the
suggestion five and thirty years ago, was long regarded as an
over-sanguine person, who did not recognize the inevitable limits of
human skill and power. A tunnel under twenty miles of stormy sea seemed
very much like an engineer’s dream, and it is only within the last few
years that it has been regarded as a feasible project. Of its
possibility, however, there seems now to be no manner of doubt. It is
merely a stream of sea-water, and not a fissure in the earth, which
divides us from the Continent. Prince Metternich was right in speaking
of it as a ditch. The depth is nowhere greater than one hundred and
eighty feet; and so far as careful soundings can ascertain the condition
of the soil underneath the water, it consists of a smooth unbroken bed
of chalk. The success of the experiment depends on this bed of chalk
being continuous and whole. Should any very deep fissure exist, which is
extremely improbable, the tunnel may probably not be driven through it.
But given, what every indication shows to exist, a homogeneous chalk bed
some hundreds of feet in thickness, the driving of a huge bore for
twenty miles through it is a mere question of time, money, and
organization, and as the engineers have these resources at their
command, they are sanguine, and we may even say confident, of success.

[Illustration:

  FIG. 186.—_Section of the Channel Tunnel._
]

[Illustration:

  FIG. 187.—_View of Dover._
]

“The method by which it is proposed that the excavation shall be made is
in some respects similar to that which was successfully employed in
tunnelling the Alps. Mont Cenis was pierced by machinery adapted to the
cutting of hard rock; the chalk strata under the Channel are to be bored
by an engine, invented by Mr. Dickenson Brunton, which works in the
comparatively soft strata like a carpenter’s auger. A beginning will be
made simultaneously on both sides of the Channel, and the effort will at
first be limited to what we may describe as making a clear hole through
from end to end. This small bore, or driftway as it is called, will be
some seven or nine feet in diameter. If such a communication can be
successfully made, the enlargement will be comparatively easy. Mr.
Brunton’s machine is said to cut through the chalk at the rate of a yard
an hour. We believe that those which were used in the Mont Cenis Tunnel
cut less than a yard a day of the hard rock of the mountain. Two years,
therefore, ought to be sufficient to allow the workers from one end to
shake hands with those from the other side. The enlargement of the
driftway into the completed tunnel would take four years’ more labour
and as many millions of money. The millions, however, will easily be
raised if the driftway is made, since the victory will be won as soon as
the two headways meet under the sea. One of the great difficulties of
the work is shared with the Mont Cenis Tunnel, the other is peculiar to
the present undertaking. The Alps above the one, and the sea above the
other, necessarily prevent the use of shafts. The work must be carried
on from each end; and all the _débris_ excavated must be brought back
the whole length of the boring, and all the air to be breathed by the
workmen must be forced in. The provision of a fit atmosphere is a mere
matter of detail. In the great Italian tunnel the machines were moved by
compressed air, which, being liberated when it had done its work,
supplied the lungs of the workers with fresh oxygen. The Alpine
engineers, however, started from the level of the earth: the main
difficulty of the Submarine Tunnel seems to be that it must have as its
starting-point at each end the bottom of a huge well more than a hundred
yards in depth. The Thames Tunnel, it will be remembered, was
approached, in the days when it was a show place