Torpedoes and Torpedo Warfare

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Title: Torpedoes and Torpedo Warfare
Author: Sleeman, C. W.
Language: English
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*** Start of this LibraryBlog Digital Book "Torpedoes and Torpedo Warfare" ***

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[Transcriber's Notes: Mathematical problems could not be represented as
in the original as we cannot stack numbers. The following rules were
used:

Parentheses added to groupings of numbers.

Bracket and "rt" square roots. [3rt]

Carets and curly brackets indicate a superscripted number, letter or
symbol. 4^{3}

An underscore and curly brackets indicate a subscript. H_{2}O

Bold text is surrounded by =equal signs= and italic text is surrounded
by _underscores_.]

[Illustration: _The "Suna" before the Explosion._]

[Illustration: _The Torpedo._]

[Illustration: _The "Suna" after the Explosion._]

Griffin & C^{o.} Portsmouth. W.F. Mitchell del.

TORPEDOES

AND

TORPEDO WARFARE:

CONTAINING A

COMPLETE AND CONCISE ACCOUNT OF THE

RISE AND PROGRESS OF SUBMARINE WARFARE;

ALSO A

DETAILED DESCRIPTION OF ALL MATTERS APPERTAINING THERETO,
INCLUDING THE LATEST IMPROVEMENTS.

BY
C. W. SLEEMAN, ESQ.,
LATE LIEUT. R.N., AND LATE COMMANDER IMPERIAL OTTOMAN NAVY.

_WITH FIFTY-SEVEN FULL-PAGE ILLUSTRATIONS, DIAGRAMS,
WOODCUTS, &c._

PORTSMOUTH:
GRIFFIN & CO., 2, THE HARD,
(_Publishers by Appointment to H.R.H. The Duke of Edinburgh._)
LONDON AGENTS: SIMPKIN, MARSHALL, & CO.
1880.

_All Rights reserved._]

PREFACE.

IN the following pages the Author has endeavoured to supply a want,
viz. a comprehensive work on Torpedo Warfare, brought down to the
latest date.

The information has been obtained while practically engaged in torpedo
work at home and abroad, and from the study of the principal books
which have already appeared on the subject, and to the authors of which
he would now beg to express his acknowledgments, viz.: "Submarine
Warfare," by Lieut.-Commander Barnes, U.S.N.; "Notes on Torpedoes," by
Major Stotherd, R.E.; "Art of War in Europe," by General Delafield,
U.S.A.; "Life of Fulton," by C. D. Colden; "Torpedo War," by R.
Fulton; "Armsmear," by H. Barnard; "Treatise on Coast Defence," by
Colonel Von Scheliha; Professional Papers of the Royal Engineers; "The
Engineering"; "The Engineer"; "Scientific American"; "Iron"; &c., &c.

The Author is also desirous of thanking the following gentlemen, to
whom he is indebted for much of the valuable information contained
herein:--

Messrs. Siemens Brothers, Messrs. Thornycroft and Co., Messrs. Yarrow
and Co., Captain C. A. McEvoy, 18 Adam Street, W.C., Mr. L. Lay,
Messrs. J. Vavaseur and Co.

LONDON, 1879.

CONTENTS.

PAGE
Preface iii

CHAPTER I.

The early History of the Torpedo--Remarks on the existing
State of Torpedo Warfare 1

CHAPTER II.

Defensive Torpedo Warfare--Mechanical Submarine
Mines--Mechanical Fuzes--Mooring Mechanical Mines 13

CHAPTER III.

Defensive Torpedo Warfare (_continued_)--Electrical
Submarine Mines--Electrical Fuzes--Insulated Electric
Cables--Electric Cable Joints--Junction Boxes--Mooring
Electrical Submarine Mines 27

CHAPTER IV.

Defensive Torpedo Warfare (_continued_)--Circuit
Closers--Firing by Observation--Voltaic
Batteries--Electrical Machines--Firing Keys and Shutter
Apparatus--Testing Submarine Mines--Clearing a Passage
through Torpedo Defences 60

CHAPTER V.

Offensive Torpedo Warfare--Drifting Torpedoes--Towing
Torpedoes--Locomotive Torpedoes--Spar Torpedoes--General
Remarks on Offensive Torpedoes 115

CHAPTER VI.

Torpedo Vessels and Boats--The _Uhlan_--The _Alarm_--The
_Destroyer_--Thornycroft's Torpedo Boats--Yarrow's
Torpedo Boats--Schibau's Torpedo Boats--Herreshoff's
Torpedo Boats--Torpedo Boat Attacks--Submarine Boats 158

CHAPTER VII.

Torpedo Operations--The Crimean War (1854-56)--The
Austro-Italian War (1859)--The American Civil War
(1861-65)--The Paraguayan War (1864-68)--The Austrian
War (1866)--The Franco-German War (1870-71)--The
Russo-Turkish War (1877-78) 187

CHAPTER VIII.

On Explosives--Definitions--Experiments--Gunpowder--Picric
Powder--Nitro-Glycerine--Dynamite--Gun-cotton--Fulminate
of Mercury--Dualin--Lithofracteur--Horsley's
Powder--Torpedo Explosive Agents--Torpedo Explosions 204

CHAPTER IX.

Torpedo Experiments--Chatham, England,
1865--Austria--Carlscrona, Sweden, 1868--Kiel,
Prussia--England, 1874--Copenhagen, Denmark,
1874--Carlscrona, Sweden, 1874-75--Portsmouth, England,
1874-75--Pola, Austria, 1875--Portsmouth, England,
1876--Experiments with Countermines--The Medway, England,
1870--Stokes Bay, England, 1873--Carlscrona, Sweden, 1874 220

CHAPTER X.

The Electric Light--The Nordenfelt and Hotchkiss Torpedo
Guns--Diving 239

CHAPTER XI.

Electricity 265

APPENDIX.

McEvoy's Single Main Systems 283
Siemens' Universal Galvanometer Tables 287
Synopsis of the Principal Events that have occurred in
connection with the History of the Torpedo 290

Index 297

LIST OF PLATES.

DESTRUCTION OF TURKISH GUNBOAT "SUNA" (_Frontispiece_).
I. FULTON'S TORPEDOES.
II. FRAME TORPEDOES, BUOYANT MECHANICAL MINES.
III. SINGER'S AND MCEVOY'S MECHANICAL MINES.
IV. EXTEMPORE MECHANICAL MINE, MECHANICAL PRIMERS.
V. MECHANICAL FUZES.
VI. FORM OF CASE OF SUBMARINE MINES.
VII. ELECTRIC FUZES.
VIII. ELECTRIC CABLES, EXTEMPORE CABLE JOINTS.
IX. PERMANENT JOINTS FOR ELECTRIC CABLES.
X. JUNCTION BOXES, MECHANICAL TURK'S HEAD.
XI. MOORINGS FOR SUBMARINE MINES.
XII. STEAM LAUNCH FOR MOORING SUBMARINE MINES.
XIII. MATHIESON'S CIRCUIT CLOSER.
XIV. AUSTRIAN CIRCUIT CLOSER, MERCURY CIRCUIT CLOSER.
XV. MCEVOY'S MAGNETO ELECTRO CIRCUIT CLOSER.
XVI. RUSSIAN SUBMARINE MINE, FIRING BY OBSERVATION.
XVII. APPARATUS FOR FIRING BY OBSERVATION.
XVIII. SYSTEMS OF DEFENCE BY SUBMARINE MINES.
XIX. FIRING BATTERIES, TESTING BATTERIES.
XX. FIRING KEYS, SHUTTER APPARATUS.
XXI. SHUTTER APPARATUS.
XXII. GALVANOMETERS FOR TESTING.
XXIII. SIEMENS' UNIVERSAL GALVANOMETER.
XXIIIA. DITTO DITTO.
XXIV. DITTO DITTO.
XXIVA. DITTO DITTO.
XXV. SHUNT, COMMUTATOR, RHEOSTAT.
XXVI. WHEATSTONE'S BRIDGE.
XXVII. TEST TABLE, DIFFERENTIAL GALVANOMETER.
XXVIII. METHODS OF TESTING--ARMSTRONG--AUSTRIAN.
XXIX. DRIFTING TORPEDOES.
XXX. HARVEY'S TOWING TORPEDO.
XXXI. DITTO DITTO.
XXXII. SYSTEMS OF ATTACK WITH HARVEY'S SEA TORPEDO.
XXXIII. DITTO DITTO.
XXXIV. DITTO DITTO.
XXXV. GERMAN AND FRENCH TOWING TORPEDOES.
XXXVI. WHITEHEAD'S FISH TORPEDOES.
XXXVII. THORNYCROFT'S BOAT APPARATUS FOR FISH TORPEDOES.
XXXVIII. LAY'S LOCOMOTIVE TORPEDO.
XXXIX. DITTO DITTO.
XL. DITTO DITTO.
XLI. DITTO DITTO.
XLII. DITTO DITTO.
XLIII. DITTO DITTO.
XLIV. MCEVOY'S DUPLEX SPAR TORPEDOES.
XLV. THE "ALARM" TORPEDO SHIP.
XLVI. THE "DESTROYER" TORPEDO SHIP.
XLVII. THORNYCROFT'S TORPEDO BOATS.
XLVIII. DITTO DITTO.
XLIX. YARROW'S TORPEDO BOATS.
L. DITTO DITTO.
LI. RUSSIAN TORPEDO BOAT, HERRESHOFF'S TORPEDO BOAT.
LII. SUBMARINE MINE EXPLOSION.
LIII. DITTO DITTO.
LIV. MCEVOY'S SINGLE MAIN SYSTEM.

[Illustration]

Torpedoes and Torpedo Warfare.

CHAPTER I.

THE EARLY HISTORY OF THE TORPEDO.--REMARKS ON THE EXISTING STATE OF
TORPEDO WARFARE.

THE earliest record we have of the employment of an infernal machine
at all resembling the torpedo of the present day, was in 1585 at the
siege of Antwerp. Here by means of certain small vessels, drifted down
the stream, in each of which was placed a magazine of gunpowder, to be
fired either by a trigger, or a combination of levers and clockwork, an
Italian engineer, Lambelli, succeeded in demolishing a bridge that the
enemy had formed over the Scheldt.

So successful was this first attempt, and so tremendous was the effect
produced on the spectators, by the explosion of one of these torpedoes,
that further investigation of this new mode of Naval warfare was at
once instituted.

But it was not until some two hundred years after that any real
progress was effected, though numerous attempts were made during this
period, to destroy vessels by means of sub-marine infernal machines.

It was owing to the fact, that the condition which is now considered as
essential in torpedo warfare, viz., that the charge must be submerged,
was then entirely ignored, that so long a standstill occurred in this
new art of making war.

_Captain Bushnell, the Inventor of Torpedoes._--To Captain David
Bushnell, of Connecticut, in 1775, is most certainly due the credit
of inventing torpedoes, or as he termed them submarine magazines. For
he first proved practically that a charge of gunpowder could be fired
under water, which is incontestably the essence of submarine warfare.

_Submarine Boat._--To Captain Bushnell is also due the credit of first
devizing a submarine boat for the purpose of conveying his magazines to
the bottom of hostile ships and there exploding them.

_Drifting Torpedoes._--Another plan of his for destroying vessels, was
that of connecting two of his infernal machines together by means of a
line, and throwing them into the water, allowing the current to carry
them across the bows of the attacked ship.

_Mode of Ignition._--The ignition of his magazines was generally
effected by means of clockwork, which, when set in motion, would
run for some time before exploding the machines, thus enabling the
operators to get clear of the explosion.

Captain Bushnell's few attempts to destroy our ships off the American
coast in 1776 and 1777, with his submarine boat, and his drifting
torpedoes were all attended with failure, a result generally
experienced, where new inventions are for the first time subjected to
the test of actual service.

_Robert Fulton._--Robert Fulton, an American, following in his
footsteps, some twenty years after, revived the subject of submarine
warfare, which during that interval seems to have been entirely
forgotten.

A resident in France, in 1797, he is found during that year making
various experiments on the Seine with a machine which he had
constructed, and by which he designed "to impart to carcasses of
gunpowder a progressive motion under water, to a certain point, and
there explode them."[A]

_Fulton's Failures._--Though these first essays of his resulted in
failure, Fulton thoroughly believed in the efficacy of his schemes, and
we find him, during that and succeeding years, vainly importunating the
French and Dutch Governments, to grant him aid and support in carrying
out experiments with his new inventions, whereby he might perfect
them, and thus ensure to whichever government acceded to his views, the
total destruction of their enemy's fleets.

_Bonaparte aids Fulton._--Though holding out such favourable terms, it
was not until 1800, when Bonaparte became First Consul, that Fulton's
solicitations were successful, and that money was granted him to carry
out a series of experiments.

In the following year (1801), under Bonaparte's immediate patronage,
Fulton carried out various and numerous experiments in the harbour of
Brest, principally with a submarine boat devised by him (named the
_Nautilus_), subsequently to his invention of submarine carcasses as
a means of approaching a ship and fixing one of his infernal machines
beneath her, unbeknown to the crew of the attacked ship.

_First Vessel destroyed by Torpedoes._--In August, 1801, Fulton
completely destroyed a small vessel in Brest harbour by means of one of
his submarine bombs, then called by him for the first time, torpedoes,
containing some twenty pounds of gunpowder. This is the first vessel
known to have been sunk by a submarine mine.

_Bonaparte's patronage withdrawn._--Notwithstanding the apparent
success, and enormous power of Fulton's projects, on account of a
failure on his part to destroy one of the English Channel fleet, at the
end of 1801, Bonaparte at once withdrew his support and aid.

Disgusted with this treatment, and having been previously pressed by
some of England's most influential men, to bring his projects to that
country, so that the English might reap the benefit of his wonderful
schemes, Fulton left France, and arrived in London, in May, 1804.

_Pitt supports Fulton._--Mr. Pitt, then Prime Minister, was much struck
with Fulton's various schemes of submarine warfare, and after examining
one of his infernal machines, or torpedoes, exclaimed, "that if
introduced into practice, it could not fail to annihilate all military
marines."[B]

Though having secured the approval of Mr. Pitt, and a few other members
of the Government, he was quite unable to induce the English to accept
his schemes in toto, and at once employ them in the Naval service.

Twice Fulton attempted to destroy French men-of-war, lying in the
harbour of Boulogne, by means of his drifting torpedoes, but each time
he failed, owing as he then explained, and which afterwards proved
to be the case, to the simple mistake of having made his machines
specifically heavier than water, thus preventing the current from
carrying them under a vessel's bottom.

_Destruction of the "Dorothea."_--Though in each of the above-mentioned
attempts Fulton succeeded in exploding his machines, and though on the
15th October, 1805, in the presence of a numerous company of Naval
and other scientific men, he completely demolished a stout brig, the
_Dorothea_, off Walmer Castle, by means of his drifting torpedoes,
similar to those employed by him at Boulogne, but considerably
improved, still the English Government refused to have anything further
to do with him or his schemes.

England, at that time, being mistress of the seas, it was clearly
her interest to make the world believe that Fulton's schemes were
impracticable and absurd.

Earl St. Vincent, in a conversation with Fulton, told him in very
strong language, "that Pitt was a fool for encouraging a mode of
warfare, which, if successful, would wrest the trident from those who
then claimed to bear it, as the sceptre of supremacy on the ocean."[C]

Wearied with incessant applications and neglect, and with failures, not
with his inventions, but in inducing governments to accept them, he
left England in 1806, and returned to his native country.

_Application to Congress for Help._--Arrived there, he lost no time in
solicitating aid from Congress to enable him to carry out experiments
with his torpedoes and submarine boats, practice alone in his opinion
being necessary to develop the extraordinary powers of his invention,
as an auxiliary to harbour defence.

By incessant applications to his government, and by circulating his
torpedo book[D] among the members, in which he had given detailed
accounts of all his previous experiments in France and England, and
elaborate plans for rendering American harbours, etc., invulnerable
to British attack, a Commission was appointed to inquire into and
practically test the value of these schemes.

They were as follows:--

1.--_Drifting Torpedoes._--Two torpedoes connected by
a line floated in the tide at a certain depth, and
suffered to drift across the bows of the vessel to
be attacked; the coupling line being arrested by the
ship's cable would cause the torpedoes to be forced
under her bottom; this plan is represented and will be
readily understood by Fig. 3.

2.--_Harpoon Torpedo._--A torpedo attached to one end
of a line, the other part to a harpoon, which was to be
fired into the bows of the doomed vessel from a piece
of ordnance mounted in the bows of a boat, specially
constructed for the purpose; the line being fixed to
the vessel by the harpoon, the current, if the vessel
were at anchor, or her progress if underweigh, would
carry the torpedo under her bottom. Fig. 2 represents
this type of Fulton's submarine infernal machine.

3.--_Spar Torpedo._--A torpedo attached to a spar
suspended by a swivel from the bowsprit of a torpedo
boat, so nearly balanced, that a man could easily
depress, or elevate the torpedo with one hand, whilst
with the other he pulled a trigger and exploded it.

4.--_Block Ship._--Block ships, that is vessels from
50 to 100 tons, constructed with sides impervious to
cannon shot, and decks made impenetrable to musket
shot. A spar torpedo _a, a, a_, to be carried on each
bow and quarter Fig. 4 represents this curious craft.

_Stationary Mines._--Stationary buoyant torpedoes
for harbour defence, to be fired by means of levers
attached to triggers. This kind of mine is shown at
Fig. 1.

5.--_Cable Cutters._--Cable cutters, that is submarine
guns discharging a sharp piece of iron in the shape of
a crescent, with sufficient force to cut through ship's
cables, or other obstructions.[E]

_Practical Experiments._--Various and exhaustive experiments were
carried out in the presence of the Commissioners, tending generally to
impress them with a favourable view of Fulton's many projects.

As a final test, the sloop _Argus_ was ordered, under the
superintendence of Commodore Rodgers, to whom Fulton had previously
explained his mode of attack, to be prepared to repel all attempts made
against her by Fulton, with his torpedoes.

_Defence of the "Argus."_--Though repeated attempts were made, none
were successful, owing to the energetic, though somewhat exaggerated
manner in which the defence of the sloop had been carried out. She
was surrounded by numerous spars lashed together, nets down to the
ground, grappling irons, heavy pieces of metal suspended from the yard
arms ready to be dropped into any boat that came beneath them, scythes
fitted to long spars for the purpose of mowing off the heads of any who
might be rash enough to get within range of them.

As Robert Fulton very justly remarked, "a system, then only in its
infancy, which compelled a hostile vessel to guard herself by such
extraordinary means could not fail of becoming a most important mode of
warfare."

Three of the Commissioners reported as favourably as could be expected,
considering its infancy, on the practical value of Fulton's scheme of
torpedo warfare.

_Congress refuse aid._--But on the strength of Commodore Rodgers's
report, which was as unfair and prejudiced, as the others were fair
and unprejudiced, Congress refused Fulton any further aid, or to
countenance any further experiments that he might still feel inclined
to prosecute.

Though undeterred by this fresh instance of neglect, and still having a
firm belief in the efficacy of his various torpedo projects, yet other
important matters connected with the improvement of the steam engine
occupied his whole time and prevented him from making any further
experiments with his submarine inventions.

_Mode of Firing, 1829._--Up to 1829, that is to say for nearly sixty
years after the invention of torpedoes, mechanical means only were
employed to effect the ignition of the torpedo charges, such as levers,
clockwork, and triggers pulled by hand; with such crude means of
exploding them, it is not extraordinary to find, that all the attempts
made to destroy hostile ships, resulted in failure.

[Illustration: FULTON'S TORPEDOES.

PLATE I]

Briefly reviewing the history of the torpedo during its first period
of existence, viz., from Captain Bushnell's invention of submarine
magazines in 1775, down to the introduction of electricity, as a
means of exploding submarine mines, by Colonel Colt, in 1829, we
find that due to the unwearied exertions, and numerous experiments
carried out by Captain Bushnell, Mr. R. Fulton and others, the
following very important principles in the art of torpedo warfare were
fully proved:--

1.--That a charge of gunpowder could be exploded under
water.

2.--That any vessel could be sunk by a torpedo,
provided only the charge were large enough.

3.--That it was possible to construct a boat which
could be navigated, and remain for several hours under
water, without detriment to her crew.

4.--That a ship at anchor could be destroyed, by means
of drifting torpedoes, or by a submarine or ordinary
boat, armed with a spar torpedo.

5.--That a vessel underweigh could be destroyed by
means of stationary submarine mines, and by the harpoon
torpedo.

These principles, which at the time were fully admitted, laid the
foundations of the systems of torpedo warfare, that are at the present
day in vogue, all over the world.

_Second Epoch._--The second epoch in the life of the torpedo dates from
1829, when Colonel Colt, then a mere lad, commenced experiments with
his submarine battery.

_Colt's Experiments._--His first public essay, was on the 4th June,
1842, when he exploded a case of powder in New York harbour, while
himself standing at a great distance off.

Having by numerous successful experiments satisfactorily proved that
vessels at anchor could be sunk by means of his electrical mines,
Colonel Colt engaged to destroy a vessel underweigh by similar means,
which feat he successfully accomplished on 13th April, 1844.

_Colt's Electric Cable._--The electric cable as used by Colonel Colt,
was insulated by cotton yarn, soaked in a solution of asphaltum and
beeswax, and the whole enclosed in a metal case.

_Colt's Reflector._--On examining Colt's papers after his death, one
was found illustrating one of his many devices for effecting the
explosion of a submarine mine at the proper instant.

_Description of Reflector._--One set of conducting wires from all the
mines is permanently attached to a single pole of a very powerful
firing battery, the other wires lead to metal points which are attached
to marks on a chart of the channel in front of the operator and which
marks correspond with the actual positions of the mines in the channel.
A reflector, is arranged to throw the image of a hostile vessel on the
chart, and as this image passes over either of the wire terminations
on it, the operator with the other battery wire, completes the
circuit, and explodes the torpedo, over which by her image thrown on
the chart, the vessel is supposed to be at that precise moment.[F] In
his experiment with a vessel under weigh, Colt had probably taken the
precaution of laying down several circles of mines, and thus aided by
cross staffs, ensured the experiment being a success.

With regard to the invention of the word torpedo, for submarine
infernal machines, Dr. Barnard in his life of Colt says, "that Fulton
used the word torpedo, probably on account of its power of stunning or
making torpid, and that a long way through the water,--in so naming it,
he buildeth better than he knew, for Colt's torpedoes being fired by
electricity may with special fitness take its name from the electric
eel."[G]

_Theoretical Knowledge._--Though many opportunities have occurred
during the last thirty-five years for practically testing the
effectiveness of torpedoes when employed on actual service, especially
during the American Civil War (1861-65) and the late Turco-Russian
War (1877-78), yet in so far as the offensive and electrical portion
of submarine warfare is concerned, our knowledge of them is still
principally theoretically.

_Failure of Offensive Torpedoes._--The manipulation of the ordinary
spar or outrigger torpedo boats, and of the various automatic
torpedoes, appears simple enough, when practice is made with those
submarine weapons during peace time, also the results of such practice
is without doubt uniformly successful, yet when the crucial test of
actual service is applied, as was the case during the war of 1877, with
the Whitehead and spar torpedoes, then a succession of failures had to
be recorded.[H]

The cause of this want of success in war-time with offensive torpedoes,
lies in the fact, that during peace time the experiments and practice
carried out with them, are done so, under the most favourable
circumstances, that is to say in daylight, and the nerves of the
operators not in that high state of tension, which would be the case,
were they attacking a man-of-war on a pitch dark night, whose exact
position cannot be known, and from whose guns at any moment a sheet of
fire may be belched forth, and a storm of shot and bullets be poured on
them, whilst on actual service, this would in nine out of ten instances
be the case.

Some uncertainty must and will always exist in offensive torpedo
operations when carried out in actual war, where, as in this case, the
success of the enterprise depends almost wholly on the state of a man's
nerves, yet this defect, a want of certainty, may to a considerable
extent be eradicated were means to be found of carrying out in time of
peace, a systematic practice of this branch of torpedo warfare, under
circumstances similar to those experienced in war time, and this is not
only possible, but practicable.

_Moral Effect of Torpedoes._--We now come to the moral effect of
torpedoes, which is undoubtedly the very essence of the vast power of
these terrible engines of war. Each successive war that has occurred,
in which the torpedo has taken a part, since Captain Bushnell's futile
attempt in 1775 to destroy our fleet by drifting numerous kegs charged
with gunpowder down the Delawarre, teem with proofs of the great worth
of torpedoes in this respect alone.

That such a dread of them should and always will be met with in future
Naval wars, at times creating a regular torpedo scare or funk, is not
extraordinary, when it is remembered that these submarine weapons of
the present day, are capable of sinking the finest ironclad afloat, and
of launching into eternity without a moment's warning or preparation,
whole ships' crews.

The torpedoes existing at the present day have, without doubt, reached
a very high degree of excellence, in so far as their construction,
fuzes, cables, &c., both electrically and mechanically, is concerned,
but much has yet to be done to develop their actual effectiveness.

The result of the numerous and exhaustive experiments that have of
late years been carried out by England, America, and Europe prove that
the necessary distances between stationary submarine mines are by far
greater than those within which the explosions are effective.

Therefore it will be found necessary to supplement those submarine
harbour defences, by automatic torpedoes that can be controlled and
directed from the shore, as well as by specially constructed torpedo
boats.

_Automatic Arrangements._--And to ensure certainty, which is the
desideratum in torpedo warfare, circuit closers, or other automatic
arrangements for exploding the submarine mines, must be employed, as
the system of firing them by judgment is not at all a sure one.

_Ship Defence._--The problem, which occupies the attention of Naval
and other scientific men, at the present day, is how best to enable a
ship to guard herself against attacks from the fish and other automatic
torpedoes, and this without in any way impairing her efficiency as a
man-of-war.

The means of such defence, should most certainly be inherent in the
vessel herself, outward methods, such as nets, booms, etc., are
to great extent impracticable, besides one of the above mentioned
torpedoes, being caught by such obstructions would, on exploding, most
probably destroy them, thus leaving the vessel undefended against
further attacks.

_Mechanical Mines._--Several ingenious methods have of late been
devised for the purpose of obviating one of the principal defects
common to all kinds of mechanical submarine mines, the most efficient
and practical of which will be found fully described in the following
pages, viz., the great danger attendant on the mooring of such mines;
but as yet, no really practical mode of rendering mechanical mines
safe, after they have once been moored and put in action, has been
discovered, were such to be devised, a very difficult and extremely
important problem of defensive torpedo warfare would be solved.

_Electrical Mines._--In regard to electrical submarine mines, much
has been done by torpedoists in general to simplify this otherwise
somewhat complicated branch of defensive torpedo warfare, by adopting
the platinum wire fuze, in the place of the high tension one, by the
employment of Leclanché firing batteries, by the simplification of
the circuit closer, and discarding the use of a circuit breaker, by
altering the form of torpedo case, and whenever possible by enclosing
the circuit closer in the submarine mine.

The necessity of a very elaborate system of testing should, if
possible, be overcome, for a system of submarine mines that requires
the numerous and various tests that are at the present day employed,
to enable those in charge of them to know for certain that when wanted
the mines will explode, cannot be considered as adaptable to actual
service. It must be remembered that the safety of many ports, etc.,
will in future wars depend almost entirely on the practical efficiency
of electrical and mechanical mines. As yet, in actual war, little or
no experience has been gained of the real value of a mode of coast
defence by electrical mines, excepting from a moral point of view,
though in this particular they have most undoubtedly been proved to be
exceedingly effective.

A submarine mine much wanted on active service, is one that can be
carried on board ships, capable of being fitted for use at a moment's
notice, and of being easily and rapidly placed in position by the
ordinary boats of a man-of-war. It should be a self-acting electrical
mine, with the circuit closing apparatus enclosed in the torpedo case,
and capable of carrying about 100 lbs. of guncotton. This form of mine
would be found extremely useful to secure the entrance to a harbour,
etc., where ships might happen to be anchored for the night, or which
might have been wrested from the enemy, etc.

They should be capable of being placed in position and picked up again,
in the shortest possible space of time.

_Offensive Torpedoes._--Coming to the question of offensive torpedoes
there still seems to be a great difference of opinion as to the real
value of the Whitehead fish torpedo, and this point will never be
finally settled until that weapon has been more thoroughly tested on
actual service; from a specially built torpedo boat, by which is meant
a Thornycroft or Yarrow craft, the spar torpedo would seem to be the
most effective weapon. Torpedo vessels for the special purpose of
experimenting with the Whitehead torpedo have been built by England,
America, and several continental governments, so that we may soon hope
to get some more decided opinion as to the utility of that weapon.
When manipulated from the shore, or large ships, the Lay torpedo boat,
if only its speed be increased will prove an exceedingly effective
submarine weapon, for the purposes of offence, active defence, or
clearing harbours, etc., of mines, in fact, it may be more truly said
of this weapon, than of the Whitehead, "that it can do everything but
speak." Captain Harvey has greatly improved his towing torpedo, but it
is still a somewhat complicated and difficult weapon to manipulate by
ordinary persons, that is, those not specially trained for the work.

Drifting torpedoes under certain circumstances should prove invaluable,
but little or no improvement has been effected in this direction.
Submarine boats have also remained _in statu quo_, though for the
purpose of clearing an enemy's harbour of mines, it seems impossible to
devise any better method.

Electric lights are now universally adopted for use on board ship, and
will play a very important part in the defence of ships against torpedo
attacks in future wars. Glancing back on what has been effected in the
matter of improving the system of torpedo warfare in all its branches
during the last few years, with the exception of the vast improvements
in the form and construction of steam torpedo boats, their engines,
etc., very little has been done, owing principally to the want of that
practical knowledge which unfortunately can only be gained from their
employment in actual war.

The late Turco-Russian war afforded a splendid opportunity for applying
the crucial test of actual service to both the offensive and defensive
branches of torpedo warfare, yet little or no light was thrown on the
somewhat shadowy subject of submarine warfare. The present struggle
between Peru and Chili may furnish some experience, but it will not be
very satisfactory, as hardly any knowledge of manipulating torpedoes is
possessed by either side.

FOOTNOTES:

[Footnote A: C. D. Colden's "Life of Fulton."]

[Footnote B: C. D. Colden's "Life of Fulton."]

[Footnote C: C. D. Colden's "Life of Fulton."]

[Footnote D: "Torpedo Warfare," by R. Fulton, 1810.]

[Footnote E: C. D. Colden's "Life of Fulton."]

[Footnote F: Johnston's Cyclopædia.]

[Footnote G: Armsmear.]

[Footnote H: See Chapter VII.]

CHAPTER II.

DEFENSIVE TORPEDO WARFARE.--MECHANICAL MINES.--MECHANICAL
FUZES.--MOORING MECHANICAL MINES.

BY defensive torpedo warfare is meant the protection of harbours,
rivers, etc., by means of various descriptions of torpedoes moored
beneath the surface of the water.

Submarine, or sea mine, is the term that has been generally adopted to
designate this particular species of torpedo.

_Submarine Mines.--Defence in Future Wars._--The very conspicuous part
played by submarine mines, in the many wars that have taken place
since the introduction of the torpedo as a legitimate mode of Naval
warfare, when their manipulation was comparatively little understood,
and construction very imperfect, proves that, with the experience so
gained, and the vast improvements that have been, and are daily being
effected, in all that appertains to the art of torpedo warfare, the
protection of harbours, etc., will in future wars depend in a great
measure on the adoption of a systematic and extensive employment of
submarine mines.

The utility and power of this mode of coast defence has been fully
exemplified in actual war, more especially during the Franco-German war
(1870-1) and the late Turco-Russian war (1877-8).

_Torpedoes in the Franco-German War._--In the former instance, the
superiority of the French over the Germans, in the matter of ships,
was more than neutralised, by the use on the part of the latter of
electrical, mechanical, and dummy mines for the protection of their
harbours, etc. In regard to the utility of the latter, it is on record
that a certain German port was entirely defended by dummy mines, the
Burgomaster of that place having been unable to obtain men to place the
active mechanical ones in position, owing to the numerous and serious
accidents that had previously occurred in other German ports at the
commencement of the war, in mooring the latter kind of submarine mine.

The effect, so far as keeping the French fleet at a distance was
concerned, was precisely the same, as though active instead of dummy
mines had been employed, thus still further proving the vast moral
power possessed by torpedoes.

_Torpedoes in the Russo-Turkish War._--In the war of 1877, the Turks,
though possessing a powerful fleet in the Black Sea and flotilla on the
Danube, made little or no use of their superiority over the Russians in
this respect. They failed to even attempt to destroy the bridges formed
by the Russians over the Danube, nor did they make any attempt to
capture Poti, re-take Kustendje, or to create diversions on the Russian
coast in the Black Sea. Had the latter service alone been effectually
carried out, by which means, a large force of the enemy would have been
held in check, immense help would have been afforded to the Ottoman
armies in Europe and Asia. Again, during the whole of the war, the
Russian port of Odessa was never sighted, and Sebastopol only once by
the Ottoman fleet.

_Cause of Failure of the Ottoman Fleet._--The cause of this repeated
neglect on the part of the Turkish fleet may be traced almost entirely
to the assumption (which in nine out of ten cases was an erroneous one)
on the part of the Naval Pashas and Beys that every Russian harbour,
etc., was a mass of submarine mines, and this in several instances
extending many miles to seaward.

So also, some of the many failures experienced by the Russians in
their numerous boat torpedo boat attacks, were due in a great measure
to an erroneous supposition on the part of the captain of the Russian
steamer, _Constantine_ (employed to convoy the torpedo boats), that
the Turks had defended the entrance, to a distance of some miles to
seaward, of their harbours, etc., and thus the torpedo boats were
dispatched to the attack some miles off the entrance, causing them,
owing to the darkness, to enter the harbour in which the Turkish
vessels were lying, in a very straggling manner. And to a similar
reason the failure of the Russians to capture Sulina, in the attack
made on that place in October, 1877, was principally owing to their not
daring to send their Popoffkas to attack from the sea.

One of the chief points of usefulness of an extensive and systematic
employment of submarine mines, will be to minimise the number of
vessels necessary for the protection of harbours, etc., thus enabling
a far larger number of ships to operate at sea against those of an
enemy, this especially applies to countries like England and America
possessing a large extent of seacoast, numerous harbours, rivers, etc.,
which it would be necessary to defend in the event of war.

_Science of Torpedo Warfare._--The science of defensive torpedo warfare
may be considered to consist of:--

1.--The arrangement of the mines in positions, such
that it would not be possible for a hostile vessel
attempting to force a passage into a harbour, etc.,
defended by such means, to pass more than one line of
them, without coming within the destructive radius of
some one or other of the remaining mines.

NOTE.--The difficulty of attaining the above effect, lies in the fact
that the destructive radius of a submarine mine, is considerably less
than the distance that must be maintained between them, to prevent
injury by concussion to the cases, circuit closers, electric cables,
etc., of such mines on the explosion of an adjacent one.

As an illustration of the above, take the case of a 500 lb. guncotton
submarine mine. Now the destructive radius of a sea-mine is found by
the formula R = [3rt](32 × C), where R is the destructive radius in
feet of a mine moored at its most effective depth, and C is the charge
(guncotton) in lbs.

In the above case R would be about 24 feet, which in so far as the
actual destruction of a ship is concerned, may be taken as correct,
but if injury to a vessel's engines, boilers, etc., be also taken into
consideration, and as the vessel would most probably be underweigh
on such an occasion, this would be a very vital and important
consideration, R would under those circumstances be more than doubled.
Now the necessary interval for safety between such mines, according
to torpedo authorities, is equal to 10 R, and should certainly be not
less than 8 R, which in this case would give about 200 feet, therefore
assuming the radius of destruction to be 50 feet, it is seen that there
would be under those conditions a clear undefended space of about 100
feet between each couple of 500 lb. mines in the same line.

2.--The combined arrangement of submarine mines with
forts and batteries, in such a manner, that every one
of the former shall be well covered by the guns of
the latter, and also that it would be impossible for
an enemy's ships to get within effective range of the
forts, or batteries, without moving over ground where
mines were laid.

NOTE.--This applies to the defence of the more important harbours,
etc., in which case the submarine mines (which would be chiefly
electrical ones) would only act as auxiliaries to the land defences. To
effectually carry out the above, there can be no question but that they
who plan the forts, etc., should also plan the systems of submarine
defence.

A harbour, river, etc., which it is necessary to protect by electrical
submarine mines, etc., and where no land defences exist, should have
its mines supported by a powerful ship or ships, as maybe thought
desirable.

_Success in Torpedo Warfare._--The two most important conditions
essentially necessary to the successful employment of torpedoes, both
offensive and defensive, are:--

1. CERTAINTY OF ACTION.
2. SIMPLICITY OF MANIPULATION.

Without the former this mode of Naval warfare is comparatively useless,
while without the latter the former condition is rarely obtained, more
especially in the case of offensive torpedoes.

Submarine mines are divided into separate classes, viz.:--

1. MECHANICAL MINES.
2. ELECTRICAL MINES.

_Mechanical Mines._--By this description of submarine mines, is meant
those whose charges are fired by mechanical means alone.

_Mechanical Mines in the American Civil War._--During the civil war
of America (1861-5), the Confederates depended almost entirely on
mechanical submarine mines for the protection of their harbours,
rivers, etc., and to this extensive use of such mines may be traced
nearly the whole of the Federal disasters afloat.

In the principal wars that have subsequently occurred, though this
form of submarine mine has been to a certain extent used, it has
generally been only as an auxiliary to the more effective electrical
torpedo, and owing to the deterrent effect produced by the numerous
torpedo successes that characterised the American Civil War, on Naval
Commanders, etc., few vessels have been destroyed by their means, the
effect of the employment of defensive torpedoes having been almost
wholly a moral one.

_Mechanical Mines for Coast Defence._--The experience hitherto gained,
with regard to the employment of mechanical mines for coast defence in
actual war, proves that they will be found exceedingly valuable in the
following positions:--

1.--In combination with booms or other obstructions
placed in defence of narrow channels, etc., which are
intended to be completely blocked up.

2.--In shallow water on the flanks of electrical mines.

3.--In protecting unfrequented bays, channels, etc.,
and a long line of seacoast, which may otherwise be
entirely undefended.

NOTE.--In this latter instance, though the mines may not be covered
by any guns, still they will be of great use, in so far, that being
mechanical ones, they cannot be rendered useless by the process of
cutting cables, etc., but must be destroyed, which in time of peace
is a work of considerable labour and danger, and, therefore, would in
the time of war, cause at the very least, serious delay to an enemy
desirous of effecting a landing, etc., at a point so protected.

There are numerous objections against their employment, the principal
ones being:--

1.--That they are all, more or less dangerous to place
in position.

2.--That they cannot be tested when moored.

3.--That they are as dangerous to friend as to foe,
when once placed in action.

4.--That an exploded, or known damaged mine cannot be
replaced.

NOTE.--The above objections, especially 2 and 3, constitute without
doubt very serious defects in a system of defence by mechanical mines,
and in the case of purely mechanical ones, it seems almost impossible
to eradicate any of them, though, notwithstanding, under the particular
circumstance before-mentioned, these species of defensive torpedo will
be found extremely useful.

_The Advantages of Mechanical Mines._--They possess a few advantages,
which are as follows:--

1.--They are comparatively cheap.

2.--They can be kept in store and ready for use at a
moment's notice.

3.--They do not require specially trained men to
manipulate them.

4.--Extempore ones can be easily and readily made.

_Best Kinds of Mechanical Mines._--Among the very numerous and various
kinds of mechanical submarine mines that have been devised the
following may be considered as the most effective, and practicable of
them all:--

1.--FRAME TORPEDOES.
2.--BUOYANT MINES.

This includes:--

_a._--BARREL MINE.
_b._--BROOK'S MINE.
3.--SINGER'S MINE.
4.--MCEVOY'S IMPROVED MINE.
5.--EXTEMPORE MINE.

_Frame Torpedoes._--This form of defensive mine is shown at Fig. 6. It
consists of a frame work which is formed of four strong timbers _a_,
_a_, _a_, _a_, these being kept parallel and only a few feet apart by
means of cross timbers _b_, _b_. A cast-iron torpedo _c_, _c_, _c_, in
the shape of a shell, is bolted to the head of each of the timbers _a_,
_a_, _a_, containing about thirty pounds of fine grained gunpowder, and
fitted with a percussion fuse, which is so placed that it would come
into contact with a vessel striking against the framework, directly
or not. One end of the frame is securely anchored, the other, that on
which the torpedoes are fixed, is kept at its proper distance below
the surface of the water by means of chains, _d_, _d_, and anchors. To
prevent the frame from sinking when sodden with water, the uprights
_e_, _e_, are provided.

This form of mechanical mine, which performs the double function of
torpedo and obstruction, was much used by the Confederates, and found
extremely useful, no passage was attempted to be forced by the Federals
where these torpedoes were known to be placed.

_Stake Torpedo._--Fig. 7 represents another form of the frame torpedo.

It consists of a piece of timber, _a_, its heels secured by a heavy
metal shoe _b_, working in a universal joint in the mooring, _c_. At
the head of the piece of timber is secured a torpedo _d_, containing
about fifty pounds of gunpowder, and fitted with four or five sensitive
fuzes. The proper angle of inclination is obtained by securing the
upper end of the timber to an anchor as shown at _e_. As a proof of the
efficiency of this species of mechanical mine, even though having been
in position for a great length of time, the U.S. gunboat, _Jonquil_,
was nearly destroyed whilst attempting to remove some similar torpedoes
which had been in position for two years.

[Illustration: FRAME TORPEDOES, BUOYANT MECHANICAL MINES.

PLATE II.]

_The Barrel Torpedo._--One description of this form of mechanical
submarine mine is shown at Fig. 8. It consists of a barrel _a_, to the
ends of which are attached two cones of pine _b_, _b_, for the purpose
of preventing the current from turning the mine over.

To ensure its being watertight, pitch is poured into the interior
through the bunghole, and the barrel rolled about, so that the inside
may be evenly covered. The outside was also thoroughly coated with
pitch. These mines usually contain about 100 lbs. of gunpowder, and
are exploded by means of percussion or chemical fuzes (_c_, _c_, _c_,)
generally five in number, screwed into sockets on each side and on the
top of the bilge of the barrels. To keep them upright a weight _d_ is
hung below the mine.

This kind of mechanical mine was much used by the Confederates, and to
some extent by the Turks in their late war with Russia.

They are cheap, convenient, and under certain circumstances very
effective. One of the objections to their use is the difficulty of
mooring them securely in strong currents, as otherwise they are very
liable to shift their positions. Three Confederate vessels were
"hoisted by their own petards," from this cause.[I]

_Brook's Torpedo._--Another form of buoyant mechanical mine is
represented at Fig. 9. It was designed for the express purpose of
preventing its discovery by dragging, etc., by the enemy. It consists
of the torpedo case _a_, formed of copper, which is attached to a
spar _b_, the lower end of which is secured to an universal joint in
its anchor _c_. Five percussion or chemical fuzes _d_, _d_, _d_, are
screwed into the head of the copper case.

_Turtle Torpedo._--To increase the danger and uncertainty of any
attempt to remove this form of buoyant mine, a turtle torpedo _A_, is
attached to it by a wire _e_. This torpedo contains about 100 lbs. of
gunpowder, and is exploded by means of a friction primer which passes
through a watertight joint _f_, and is attached to the wire _e_.

Whether this combination would prove effective, has yet to be seen, but
the buoyant mine alone was considered one of the most dangerous used by
the Confederates.

_Singer's Mechanical Mine._--An elevation and section of this form of
mechanical mine is shown at Fig. 10. It consists of an air chamber
_a_, and a powder chamber _b_; in the latter is fixed a rod of iron
_c_, one end of which rests in a cup formed in a lug _d_, where there
is a screw by means of which the rod _c_ may be screwed against the
bottom of the torpedo case, on the interior. In the cup is placed the
fulminating substance. A heavy cast iron cap _A B_ rests upon the top
of the case and is prevented from falling off by a low rim of tin,
which enters an aperture in the cap as at _e_: a wire _f_ connects
this cap with a pin _g_, which keeps a plunger _h_ at rest. The head
of this plunger _h_ is directly beneath the bottom of the rod _c_,
within the case; by means of a spring _i_, directly the pin _g_ is
drawn out, which is done by a hostile vessel striking against the mine
and knocking off the cap _A B_, the plunger _h_ is forced against the
bottom of the case and drives the rod _c_ into the cup containing the
fulminate, and so explodes the torpedo. The case of these mines, as
used by the Confederates, was formed of tin, and they contained from
50 to 100 lbs. of powder. A safety pin _k_ is provided to prevent a
premature explosion due to the pin _g_ being accidentally withdrawn.

This form of submarine mine was one of the most successful and most
extensively employed of all, on the part of the Confederates.

Though no accidents are stated to have occurred in placing this mine
in position, yet the fact of the iron rod _c_ having to be fixed for
action, and that close against the interior of the bottom of the case,
before the charge of powder has been put in, is an element of great
danger, for a comparatively slight blow beneath it, which might easily
occur in transport, etc., would explode the torpedo prematurely.

_McEvoy's Improved Singer's Mine._--To obviate this defect Captain
McEvoy has designed an improved mode of ignition for Singer's mine.
This is shown at Fig. 11. The form of case, and arrangement of heavy
cap are similar to those in Singer's mine. The mode of ignition is
as follows:--In the powder chamber _b_ is fixed a friction fuze _f_,
which by means of a piece of wire secured to a length of chain _k_,
_k_, is connected with the heavy cast iron cap _A B_. The piece of wire
passes through a diaphragm of thin metal _h_, which is soldered all
around, thus forming a complete watertight joint. Premature explosion
is prevented by passing a link of the chain, through a slot in the bolt
_c_, securing it there by a pin of bent wire _l_. The dotted line of
chain _k_, _k_, shows its position during the process of mooring this
form of Singer's torpedo. The manner of lowering this and also Singer's
mine is shown at Fig. 12. A buoy _x_, is attached by means of a line,
in the former case to the pin _l_, Fig. 12, in the latter case to
the pin _k_, Fig. 10, the pulling out of either, sets their respective
mines in action.

[Illustration: SINGER'S AND M^{c}EVOY'S MECHANICAL MINES.

PLATE III.]

_Mathieson's Cement Safety Plug_.--In the place of the safety pin _l_,
Fig. 11, employed by Captain McEvoy in his improved form of Singer's
mine, Quartermaster-Sergeant Mathieson, late Royal Engineers, employs
a plug or disc of soluble cement, so arranged that the action of the
sea-water after the mine has been placed in position destroys the plug
or disc, and so frees the chain which is connected with the fuze and
the heavy cap of the torpedo. This plan does away with the necessity of
using a buoy and line as shown in Fig. 12, and also affords ample time
for the men engaged in mooring the mine to get far away before it is
ready for action.

_Mechanical Mine_.--The extempore mechanical submarine mine, shown at
Fig. 13, will be found to possess all the qualities which are necessary
to a perfect mine of that description.

It is extremely simple, it can be readily and quickly made, all the
materials of which it is constructed are at hand on board every
man-of-war, and it is certain in its action.

It consists of a barrel _a_, which is thoroughly coated inside and
out with hot pitch, etc., to make it watertight, a block of wood _b_,
secured to the top of the cask _a_, and having a recess cut in it to
receive a round shot _c_, also a hole through which a strop _d_, is
passed, and another hole to receive a toggle _e_. At the bottom of the
cask on the inside, is fixed a wooden frame work _f, f_, to the top of
which two ordinary gun friction tubes are fixed _g_, _g_. A piece of
wood _h_, is secured to the bottom of the cask on the outside, bored
with two holes, one to receive a thin iron rod _i_, the other for the
safety pin _k_. Wires _x_, _x_, secure the gun tubes _g_, _g_, to
one end of the iron rod _i_, the other end of which is connected by
means of a rope lanyard to the shot _c_. Weights are slung beneath the
barrel to keep the mine upright. The principle of action of this form
of mechanical mine is precisely similar to that of Captain McEvoy's
improved Singer's mine, and need not, therefore, be described.

_McEvoy's Mechanical Primer_.--A sectional view of this apparatus
is represented by Fig. 14. It consists of two brass tubes fitting
accurately one within the other, of which _a_, _a_, is the inner one.
To this inner tube are affixed two brass diaphragms _b_, _b_. A brass
spindle _c_, carries a weight _d_, which is regulated by a spring, _e_.
A locking rod, _f_, moves in a ball and socket joint at _g_. A hammer
_h_, which is shown in Fig. 14, at full cock, is kept in that position
by the rod _f_. A vessel, striking the mine, in which this apparatus is
placed causes the weight, _d_, to cant over, allowing the rod, _f_, to
be forced upwards by means of the spring _e_, and so frees the hammer
_h_, which falls on a nipple _i_, on which is placed the percussion
substance, and so explodes the mine.

_McEvoy's Papier Maché Safety Plug._--To prevent a premature explosion
during transport, etc., of a mine in which this apparatus is placed, a
plug of papier maché, which is soluble in water, is inserted in the two
spaces _p_, _p_, by which the spindle _c_, is prevented from moving to
one side or the other. The use of a papier maché, instead of a cement
plug for the purposes of safety, is a great improvement, as by the
simple process of pressure, any period of time that it is necessary
should elapse before the complete destruction of the plug, can be
readily and certainly obtained, which when a cement plug, formed of
different ingredients is used, is not always the case.

_McEvoy's Mechanical Mines._--Captain McEvoy has also devised a plan,
whereby a mechanical mine of the foregoing form may be placed in a
state of safety, even after it has been rendered active. In the place
of the aforesaid papier maché wad at _p_, Fig. 14, he uses a plunger
which fits into the cavity _p_, of the heavy weight _d_. This plunger
is always kept in a position clear of the weight by means of a spiral
spring, unless it is desired to render the mine inactive when the
plunger is forced into the aforesaid cavity and kept there by means of
a pin inserted above it. Above this there is another plunger, acted
on by a spiral spring sufficiently powerful to enable it to force
the previous mentioned plunger into the safety position; this upper
plunger is rendered inactive by means of a pin. The mine being placed
in position, that pin which is keeping the lower plunger inserted in
the cavity _p_, of the weight _d_, is withdrawn and the mine rendered
active. To the pin of the upper plunger is attached a line which is
anchored some distance from the mine in a known position. Then to
render the mine inactive for the purpose of picking it up, etc., it
is only necessary to raise the aforesaid line, and draw out the pin
of the upper plunger, which by means of the strong spiral spring will
force the lower plunger into the safety position, and render the mine
inactive.

Whether this invention is a practicable one or not, remains to be
proved, but anyhow it is a step in the right direction.

[Illustration: EXTEMPORE MECHANICAL MINE, MECHANICAL PRIMERS.

PLATE 4]

_Abel's Mechanical Primer._--This is shown in section and elevation at
Fig. 15 (A and B). _a_, _a_, is the powder chamber in which the priming
charge is placed; _b_ is a screw plug to close the chamber; _c_ is a
flexible india rubber tube; _d_, _d_, are screw bands; _e_ is a glass
tube containing oil of vitriol enclosed in a lead tube; _f_ which
contains the explosive mixture; _g_, an eye at the head of the primer
to receive the firing line; _h_, _h_ are segmental guards; _i_ is the
guard ring; and _j_ the safety screw pin. This apparatus is screwed
into a socket in the upper part of the torpedo case, as shown at Fig.
15 (C).

_Mode of Action._--When placed in position, to render the primer ready
for action, the guard ring, _i_, is pulled off, first having removed
the safety pin _j_, when the segmental guards _h_, _h_, will fall away,
leaving the india rubber tube _c_, _c_, exposed.

A sufficient strain being brought on the rope secured to the ring _g_,
the lead tube _f_ bends, causing the fracture of the glass tube _e_,
thus igniting the priming charge and exploding the mine.

A submarine mine so fitted may be fired at will, by bringing a line,
from the ring _g_, to the shore, or it may be made self-acting by
connecting two of them together, etc.

_Percussion and Chemical Fuzes._--Many forms of this mode of mechanical
ignition have been from time to time devised, of which the following
are the most important ones:--

_Sensitive Fuze._--It consists of an inner cylinder _a_, _a_, Fig. 15,
of composition metal, 1-1/2" diameter, and 2-1/2" long, having a thread
cut on its outside, and a bouching _b_, 2-1/4" diameter and 2" long
with a sexagonal projection _c_, for applying a wrench, also with an
external and internal thread. The upper end of the inner cylinder _a_,
is solid for 1", and is perforated by three holes _d_, _d_, _d_, in
each of which a percussion primer is placed _e_, _e_. A piece of thin,
soft and well annealed copper _f_ is soldered to the upper end of the
bouching _b_, to keep moisture from the primers, and is so thin that a
slight blow will crush without breaking it. A safety cap can be screwed
on to the external thread above the projection _c_.

_Rain's Detonating Composition._--The detonating composition employed
in this and many other forms of percussion fuzes by the Confederates,
etc., consisted of a combination of fulminate of mercury and ground
glass, and was invented by, and is named after, General Rains, Chief
of the Torpedo Bureau, at Richmond, during the Civil War (1861-5). So
sensitive was this composition that seven pounds pressure, applied to
the head of one of the primers, would explode it.

When required for use the internal cylinder _a_, containing the primers
_e_, _e_, is screwed up until contact between them and the copper cap
_f_ is secured.

_McEvoy's Percussion Fuze._--Fig. 16 represents a longitudinal section,
full size, of the mechanical percussion fuze, used by Captain McEvoy in
connection with his drifting torpedo, which latter will be hereafter
described. _a_ is a piece of metal, having an external and internal
thread, and a projection _b_, to which is applied the spanner for
screwing it into the torpedo case. This piece _a_ is hollow at its
upper end, and is closed by means of a thin copper dome _c_, which is
soldered to it. Screwed into the piece _a_ is the plug, or nipple _d_,
with a hole through it from end to end, it is rammed full of mealed
powder, and then a fine hole is drilled through the composition. A
cavity _e_ at the head of the plug, or nipple _d_, is filled with a
fulminating substance. A spiral spring _f_, encircles the plug _d_, on
which a cap _g_ rests; _h_ is a needle in this cap. The action of this
fuze will be readily understood from the plan of the fuze at Fig. 16.
A safety cap is provided, which fits into the slots _i_, _i_, and is
fixed there by means of a set screw.

_Improved Form of Jacobi's fuze._--The section shown in Fig. 17 is an
improved form of the chemical fuze, invented by Professor Jacobi, and
used by the Russians in their land and sea mines during the Crimean war
(1854-5). It consisted of a small glass tube _a_, containing sulphuric
acid, enclosed in a lead cylinder _b_. A mixture of chlorate of potash
and white sugar surrounds the tube and holds it in position; _c_ is a
primer filled with mealed powder in connection with the charge of the
mine. The action of this fuze is as follows:--On a vessel striking
against the lead cylinder _b_, it is crushed in, breaking the glass
tube containing the sulphuric acid, and thus causes it (acid) to flow
into the mixture of chlorate of potash and white sugar, producing fire,
which by means of the primer _c_, passes into the charge, and explodes
the mine.

[Illustration: MECHANICAL FUZES.

PLATE V.]

_Defect of Chemical Fuze._--The defect of the chemical fuze just
described is its slow rate of ignition when compared to gunpowder. This
may be remedied by adding a small quantity of sulphuret of antimony or
perro cyanide of potassium.

Both the Turks and the Germans employed, as a mode of ignition for
their mechanical submarine mines, the chemical fuze described above,
with but slight modifications in the shape of the lead cylinder and
manner of fixing the fuze into the torpedo case.

Mechanical fuzes, both percussion and chemical, which require a blow
to effect their ignition, are to a certain extent defective when
applied to submarine mechanical mines (which are always buoyant ones)
in so far that a hostile vessel passing over ground supposed to be
defended by torpedoes of any description, would do so at as slow a
rate of speed as it would be possible to proceed at, and would, under
those circumstances, _push away_ rather than strike a buoyant mine,
with which she might come in contact. During the American civil war
and the Russo-Turkish war, especially in the former, there are several
instances on record of vessels passing over buoyant mechanical mines
unharmed, whilst similar vessels have afterwards been destroyed
by those self-same mines; and the only cause for such apparent
inconsistency being the above-mentioned one, viz., the pushing rather
than striking effect produced on a buoyant mine by a vessel under weigh
proceeding at a very slow speed, or merely drifting with the current.

_Steward's Safety-Cock Arrangements._--To obtain security to a certain
extent in placing mechanical submarine mines in position, which,
as has been previously stated, is one of the defects common to all
forms of such torpedoes, many ingenious methods have been devised,
such as safety caps to their fuzes, safety pins, soluble plugs, &c.
Another method, suggested by Captain Harding Steward, R.E., which
it is intended should be used in connection with the other safety
arrangements, is shown at Fig. 18. It consists of a stop-cock _A_,
which, in connection with a tube, is introduced between the fuze and
the charge. It is so arranged that when the cock is turned in the
direction of the tube, as shown in section _B_ at _e_, the gas on
formation can pass easily through and explode the charge; but when
the cock is shut off, the gas on formation escapes through the side
_d_, as shown in section _C_. To prevent destruction of the charge
through leakage under the pressure of the water, the cone in connection
with the stop-cock should fit very accurately, and, as an additional
preventive, the escape hole should be covered with a waterproof
plaster, which at a moderate depth would keep the water out and yet
offer no material resistance to the escape of the gas if the stop-cock
were shut off, as at _C_. The efficiency of this arrangement, as
far as relates to its cutting off the gas from the charge, has been
satisfactorily proved by practical experiments.

_Mooring Mechanical Mines._--This description of defensive torpedo
will rarely be used in deep-water channels, &c., and on account of
the impossibility of ascertaining whether such a mine has drifted or
otherwise, it should not be moored in a very rapid current. Such being
the case, an ordinary mushroom anchor, heavy stone, &c., and single
steel wire mooring-rope, will be generally found quite sufficient to
keep such mines in position.

When only a few mechanical submarine mines are moored in position, and
at some distance apart, it would be found a useful plan to moor them
each with three anchors, one anchor being up-stream. By this method,
at low water, on the up-stream anchor being raised, the mine would
show itself, and might in that position be approached and rendered
inactive. Were this plan to be adopted when several such mines are in
position, there would be the danger of the up-stream anchor on being
raised, bringing up to the surface, and probably in contact with the
boat at work, a mine to which that particular anchor does not belong,
an explosion being the result.

FOOTNOTES:

[Footnote I: "Submarine Warfare," by Commander S. Barnes, U.S.N.]

CHAPTER III.

DEFENSIVE TORPEDO WARFARE--_continued_.

BY electrical submarine mines is meant those whose charges are ignited
by the agency of electricity.

_Submarine Mines during the Crimean and American Wars._--It was during
the Crimean war (1854-6) that this description of defensive torpedoes
was for the first time employed on actual service. Several of the
principal Russian harbours were protected by this form of submarine
mine, but owing to the smallness of their charges, and to the want of
electrical knowledge on the part of the Russian officers and men in
charge of them, none of the ships of the Allies were sunk, or even
rendered _hors de combat_ by this mode of harbour defence, though in
several instances ground known to be covered with submarine mines was
passed over by both English and French vessels of war.

Subsequently the Confederates, during the American civil war, employed
electrical submarine mines in considerable numbers for the defence
of their numerous harbours, rivers, &c.; but though in so far as the
size of the torpedo charges was concerned, they did not make the same
mistake as the Russians, yet, owing to the absence of proper electrical
apparatus, and the want of any practical knowledge of the manipulation
of electrical sea mines, on the part of the Confederate torpedoists,
they were almost entirely unsuccessful in destroying the Federal
warships; the _Commodore Jones_ being the sole instance, out of the
large number of vessels belonging to the Northerners which were sunk
and severely injured by torpedoes, of a war steamer being sunk by means
of electrical submarine mines.

In the Franco-German and Russo-Turkish wars which have lately occurred,
electrical sea mines were very extensively used in coast defence, but
with the exception of the loss of the gunboat _Suna_ to the Turks,
during the latter struggle, by this form of defensive torpedo, no other
damage to vessels resulted from their use, yet owing to the vast moral
power possessed by these submarine weapons, they were enabled to most
effectually carry out the work of defence entrusted to their care.

Of late years many important discoveries have been made in the science
of electricity, and vast improvements have been effected in electrical
apparatus, to which causes may be traced the vastly improved system of
electrical submarine mines as adopted by the English, American, and
principal European governments at the present day, as compared with
those that have hitherto been employed.

The certainty of action when required of electrical submarine mines,
which is of course the desideratum of all torpedoists, has, by the
improved mode and manner of ascertaining the exact electrical condition
of each particular mine, and of the system as a whole, which is at
present in vogue, been made almost absolute.

_Advantages of Electrical Submarine Mines._--This form of defensive
torpedo possesses numerous important advantages, the principal of which
are as follows:--

1.--They are always absolutely under control.

NOTE.--By detaching or connecting the firing battery, which is effected
by means of a plug, key, &c., they may be respectively rendered
harmless, or dangerous. Thus friendly ships may pass over them in
safety, whilst those of the enemy are debarred from so doing. On this
account harbours, &c., protected by such mines are termed "Harbours of
refuge."

2.--Fresh mines may be added to a system of such
defensive torpedoes, thereby allowing an exploded mine
to be replaced.

NOTE.--This is a very important point in connection with a system of
defence by submarine mines, as in the case of a deep water channel,
a hostile vessel being sunk by one of them, would not become an
obstruction, as, were the channel a comparatively shallow one would
most probably be the result, and therefore it would be necessary to put
a fresh mine in the place of the exploded one; this would also apply
were a mine to be prematurely ignited, or if any portion of its firing
apparatus were injured.

3.--At night, or in a fog, no vessel can pass through a
channel, &c., so protected without affording a means of
ascertaining her presence.

NOTE.--This is also a very important advantage of a system of defence
by electrical sea mines, affording as it does a complete safeguard
against surprise.

4.--The power of obtaining proof, without going
near it, by a system of testing that the electrical
condition of the mine, &c., is perfect.

NOTE.--This again is an extremely important point. For were a charge to
become wet, one of the electric cables of the mine broken, or damaged,
&c., it would instantly be made apparent at the firing station, and
could be at once remedied.

5.--They can be raised for examination, or removed when
no longer required, with ease and safety.

Such are some of the chief advantages of employing the agency of
electricity to effect the ignition of the charge in a system of defence
by submarine mines.

_Defects of Electrical Submarine Mines._--The following are the chief
defects connected with the use of electrical mines:--

1.--The number of wires that are required to be used
with them.

2.--The necessity of employing specially trained men in
their manipulation.

In time there seems little doubt but that the former obstacle will be
to a considerable extent overcome, but the latter must always be a flaw
in an otherwise perfect system of coast defence by submarine mines.

_Rules to be observed in using Electrical Submarine Mines._--In
connection with a system of electrical submarine mines the following
rules should be carefully observed:--

1.--They should be moored in deep channels, that is
to say, where the larger class of vessels would in
attempting to force a passage be obliged to go.

NOTE.--Mechanical submarine mines should never be used under these
circumstances, as the difficulties of mooring them and keeping them in
position would be very considerable, also a vessel being sunk in a very
deep channel would not necessarily block it, and as a mechanical mine
cannot be replaced, a gap would be left in the defence.

2.--They should be placed in the narrowest parts of the
channel.

NOTE.--The object of this rule is evident, fewer mines being required,
and consequently in the case of electrical ones, a far less number
of wires are needed, which gives an increase of simplicity, and
consequently more effectiveness. This point should be observed in
connection with mechanical, as well as electrical submarine mines.

3.--They should where practicable be moored on the
ground.

NOTE.--The advantages attendant on an observance of this rule are:--

_a._--Increased vertical effect.

_b._--Avoidance of mooring difficulties.

_c._--Less liability of shifting from its original
position.

_d._--Less chance of its being discovered and rendered
useless by an enemy.

_e._--By far heavier charges may be conveniently
employed.

4.--Where possible, no indication whatever should be
given of the position of the mines by their circuit
closers, or in the case of small buoyant ones, by the
mines themselves.

NOTE.--In some instances this will be almost impracticable, as for
example, where there is a very great rise and fall of tide. For
instance, at Noel Bay in the Bay of Fundy, the rise is over fifty feet.
Here, when circuit closers, or small buoyant mines are used, both of
which ought never to be more than twenty feet below the surface, long
before low water they would be found floating on the surface in full
view. Many attempts have been made to overcome this difficulty, but as
yet no really practicable means have been devised.

5.--The stations where the firing batteries, &c., are
placed, should be in the defensive work likely to
be held the longest, thus enabling the mines to be
commanded up to the last moment.

6.--The electric cables should be laid in positions
such that their discovery by the enemy would be
extremely difficult, and almost impossible.

NOTE.--This may be to a certain extent effected by leading them from
the mines to the firing and observing stations by circuitous routes,
and by burying them in trenches.

7.--They should not be thrown away on boats.

NOTES.--As they can in all cases be fired by will, even when circuit
closers are used, this rule is easily observed. But to prevent an
enemy's boats from rendering the mines useless, a line of small
torpedoes might be placed in advance of the large ones, or the circuit
closers themselves might be charged.

At night, or in foggy weather it will be necessary to employ
guard-boats, electric lights, &c., to protect them against damage by an
enemy's boats, &c.

In the foregoing pages of this chapter will be found the requirements
and conditions essential to a perfect system of electrical submarine
mines for the defence of a harbour, river, &c.; in the following
pages a general description of the component parts of such defensive
torpedoes, under the following heads--Form and Construction of Case;
Electrical Fuzes; Electric Cables; Watertight Joints; Junction Boxes;
and Mode of Mooring, will be considered.

_Form and Construction of Torpedo Case._--The case of a submarine mine
should be capable of fulfilling the following conditions:--

1. It must be able at great depths to withstand a great
pressure of water, and remain perfectly watertight.

NOTE.--This in the case of a charge of gunpowder being an imperative
necessity.

2. As a buoyant mine, it must be capable of affording
a considerable excess of buoyancy, by which it may be
rendered stationary when moored.

NOTE.--This is generally obtained by having an air space within
the torpedo, thus requiring a much larger case in which the charge
is enclosed than would otherwise be necessary, causing increased
difficulties in transportation, mooring, and raising them for
examination, &c.

3. When explosive agents which require a certain time
for thorough combustion are used as the charge, such
as gunpowder, picric powder, gun-cotton (not fired by
detonation), &c., a much stronger case is necessary
to obtain the full explosive effect than would be the
case were detonated charges, under the same conditions,
employed.

NOTE.--This is an extremely important point, for if a weak case is
employed with a charge of gunpowder, &c., fired by a fuze primed with
powder only, a portion of it on being fired would generate a sufficient
quantity of gas to burst the case, thus blowing out the remainder of
the charge before its ignition had been effected.

4. It should be of such a form that the complete
ignition of the charge is obtained by the employment
of the least number of fuzes possible to effect this
result.

NOTE.--This point is especially to be observed when gunpowder is the
explosive agent.

The various forms of defensive torpedo cases may be classed under the
following heads:--

1.--Spherical shape.
2.--Cylindrical shape.
3.--Conical shape.

_Spherical Shape._--This form of case is theoretically the very
best one possible to devise, but on account of the difficulty of
constructing it, and its comparative costliness, such a form may be put
aside as being impracticable.

_Cylindrical Shape._--Torpedoists in general have hitherto adopted the
cylindrical form of case as being the best adaptable for both ground
and buoyant mines containing a heavy charge.

The Confederates employed exclusively this shape for their electrical
submarine mines, which were ground ones, and the Austrians in the war
of "66" approved of this form of case for their electrical submarine
mines, which were buoyant ones. Figs. 19 and 20 represent respectively
the American and Austrian mines.

In England the cylindrical shape has up to quite lately found most
favour with her torpedoists for both buoyant and ground mines. At Fig.
21 is represented a 100-lb. buoyant electrical mine, surrounded by a
wooden jacket, _e_, and having its circuit closer, _C_, enclosed within
it; and at Fig. 22 is shown a 250-lb. electrical mine, which may be
used either as a buoyant or ground one.

For large ground mines, the best form of torpedo case seems to be that
of the turtle mine, which is shown at Fig. 9. A heavy charge may be
contained in it; it forms its own anchor; and it would withstand an
explosion of an adjacent mine without sustaining any injury. At present
the cylindrical shape is the form generally used, though as far as
retaining its position on the ground in a strong tide, it cannot be
compared to the turtle form.

[Illustration: FORM OF CASE OF SUBMARINE MINES.

PLATE VI.]

_The Conical Shape._--Hitherto this shape of submarine mine case was
only used in connection with mechanical mines, but now it is the
form considered most suitable for all buoyant mines, electrical or
mechanical. At Fig. 23 is shown the conical shaped mechanical mine,
employed by the Confederates for use with sensitive fuzes. The conical
form of torpedo case lately approved of by the English torpedo
authorities is somewhat similar to that one, the charge being contained
in a kind of box hung from the top of the case, and the circuit closer
is screwed into the bottom of the case; surrounding the upper part
of the case is a thick buffer of wood, by which damage to the mine
is prevented by the passage of friendly ships. This is altogether a
very neat and serviceable form of torpedo case. This form of case is
also more difficult to discover by dragging, and easier to retain in
position.

_Electrical Fuzes._--The fuzes employed in connection with electrical
submarine mines may be divided into two classes:--

1. Platinum wire bridge fuzes.

NOTE.--That is where the evolution of heat is caused by a large
_quantity_ of the electric force flowing through a good conductor
of large section, such as the copper core of electric cables, being
suddenly checked by a very thin wire composed of a metal which compared
with the conductor offers a very great resistance, such as _platinum_.

2. High tension fuzes.

NOTE.--That is where the evolution of heat is caused by the electric
spark, or by the electric discharge taking place through a substance
which offers very great resistance to the passage of the electric force.

_Platinum Wire Fuze._--This is the form of electrical fuze most
commonly used, and which will most certainly supersede altogether the
high tension fuze.

There are numerous advantages accruing from the use of platinum wire
fuzes, the chief of which are here enumerated:--

_a._--Great facilities for, and entire safety whilst
testing the circuit.

_b._--Extreme simplicity of manufacture.

_c._--Non-liability to deteriorate.

_d._--Perfect insulation of the electric cables used in
connection with submarine mines not necessary.

_English Service Platinum Wire Fuze._--The following is a description
of the platinum wire fuze of the form adopted in the English service, a
section of which is shown at Fig. 24. It consists of a head of ebonite
_a_, hollowed out, in which a metal mould is fixed, the wires which
have been previously bared are inserted into holes in this mould, and
firmly fixed thereto by means of a composition poured into the mould,
whilst hot; this is shown at _b_. The two bared ends of the wires which
project beyond the metal mould, as _c_, _c_, are connected by a bridge
of platinum-silver wire ·0014" in diameter and weighing ·21 grs. per
yard. This is effected as follows:--

A very fine shallow groove is made in the flat ends of the bare wires
_c_, _c_, and the platinum-silver wire is laid across in the incisions,
and fixed there by means of solder. The length of the bridge _d_ is
·25."

A tube _e_, made of tin, and soldered to a brass socket _f_, is fixed
by means of cement to the ebonite head _a_; in this tube is placed the
fulminate of mercury, the open end of the tube _g_ being closed with a
pellet of red lead and shellac varnish; around the bridge of the fuze
is placed some loose gun-cotton.

_McEvoy's Platinum Wire Fuze._--Another form of platinum wire fuze,
which has been devised by Captain McEvoy, formerly of the Confederate
Service, is shown at Fig. 25. It consists of the head _a_, formed of
a mixture of ground glass, or Portland cement, worked up with sulphur
as a base: this mixture when hot is poured into a mould, in which the
two insulated copper wires, _b_, _b_, have been previously placed; when
cold, the mixture with the wires affixed is removed from the mould,
and the platinum wire bridge _c_ being secured to the bare ends of the
copper wires, the whole is firmly fixed in a brass socket _d_, by means
of cement; the space _e_ is filled with loose dry gun-cotton, so as
to surround the bridge _c_; a copper tube _f_, closed at one end, is
partly filled with fulminate of mercury, and when the fuze is required
for service, this tube is secured to the brass socket _d_ by means of
cement.

In this form of low tension fuze there is no liability whatever of
any injury being caused to the bridge by the working of the wires in
the head, or by damp even after lying in the water for a month or
more. One peculiarity of this fuze is that the composition is run over
the insulated wires without materially softening the dielectric, or
affecting in the slightest degree the insulation of the wires.

_High Tension Fuzes._--The high tension fuze was devised for use with
electrical submarine mines, in the place of the platinum wire fuze,
on account of the little knowledge possessed, in the early days of
submarine warfare, in regard to the manipulation of Voltaic batteries.

Platinum wire requires a temperature of some 500° F. to heat it to
incandescence, and therefore necessitates the use of a powerful Voltaic
battery, both in intensity and power, to effect the ignition of
gunpowder by this means at considerable distances.

The Grove and Bunsen pile were the only suitable form of Voltaic
battery known at the period of the introduction of high tension fuzes,
both of which possessed the defects of uncertainty and inconstancy, and
also were by far too cumbersome and too difficult to keep in effective
working order to be of any real practicable value.

High tension fuzes may be ignited by means of either an electro-magneto
machine, an electro-dynamo machine, a frictional machine, or by a
Voltaic battery, generating an electric current of high intensity.
Various kinds of this form of electrical fuze have been designed, the
principal of which are as follows:--

1.--Statham's fuze.
2.--Beardslee's fuze.
3.--Von Ebner's fuze.
4.--Abel's fuze.
5.--Extempore fuze.

_Statham's Fuze._--A section and elevation of this electric fuze are
shown at Fig. 26; _a_, _b_ is a gutta percha tube, with an opening cut
in it, as shown in figure. The interior of this vulcanised gutta percha
tube is coated with a thin layer of sulphide of copper, which coating
is obtained by leaving a bare copper wire for some time in connection
with the above-mentioned tube. The extremities of two insulated copper
wires _c_, _c_, considerably smaller than the conducting wires, are
uncovered, scraped, and then inserted into the tube _a_, _b_, with an
interval of ·15 inch between them. The wires are then bent as shown in
the figure, and the priming placed between the terminals. The whole
is covered with a gutta percha bag, which is filled with fine grained
gunpowder. The priming substance is composed of fulminate of mercury
worked up with gum water. The objection to this fuze, which was used
by the Allies in their destruction of the Russian fortifications at
Sebastopol, is the want of sensitiveness of sulphide of copper, and the
consequent necessity of a very powerful firing battery.

_Beardslee's Fuze._--This high tension fuze is shown at Fig. 27.
It consists of a cylindrical piece of soft wood a, which is about
three-quarters of an inch in length and in diameter; two copper nails,
_b_, _b_, are driven through this piece of wood _a_, in such a way
that while the two heads come together as close as possible without
absolutely touching, the pointed ends are some distance apart from
each other, and project through the wood _a_; two insulated copper
wires, _c_, _c_, are firmly soldered to these projecting ends, and
a piece of soft wax, _d_, is pressed around the junction points. In
a groove, across the heads of the copper nails, is placed a little
black lead, to which is added a minute quantity of some substance, the
nature of which is known only to Mr. Beardslee. Several folds of paper
are wrapped round the wooden cylinder, forming a cylinder about 2-1/2
inches long, one end of which is tightly fastened round the insulated
wires as at _e_. The other end of the cylinder is then filled with
powder, _f_, and closed by a piece of twine. The whole fuze is then
coated with black varnish. Though not highly sensitive, Beardslee's
fuze is exceedingly efficient, and extremely simple.

_Von Ebner's Fuze._--This form of fuze was devised by Colonel Von Ebner
of the Austrian Engineers. A section and elevation of it is shown at
Fig. 28. It consists of an outer cylinder, _a_, of gutta percha, and an
inner one of copper, _b_, which latter encloses a core formed of ground
glass and sulphur, _c_, which core is cast round the two conducting
wires _d_, _d_ in such a way that they are completely insulated from
one another. In the first instance the wire is in one continuous
length, the opening _e_ being subsequently made, and carefully gauged,
so as to ensure a uniform break, or interval in the conductor of
each fuze. The priming composition, which consists of equal parts of
sulphide of antimony and chlorate of potash, is placed in the hollow
_f_, to which is added some powdered plumbago, for the purpose of
increasing the conducting power of the composition. This mixture is
put into the hollow, _f_, of the fuze under considerable pressure, the
terminals being connected with a sensitive galvanometer, in circuit
with a test battery, and the pressure applied so as to obtain, as far
as possible, uniformity in the electrical resistance of each fuze.

The Austrians employed this form of high tension fuze in connection
with a frictional machine for the electrical mines used in their
defence of Venice, &c. during the war of 1866.

_Abel's Fuze._--Mr. Abel devised a high tension fuze, which in 1858 was
extensively experimented with; the Beardslee and Von Ebner fuze being
based upon the principles applied for the first time in Abel's fuze.

[Illustration: ELECTRICAL FUZES.

PLATE VII]

Many modifications of it have been from time to time devised by Mr.
Abel; a section and elevation of the more recent form of his fuze
is shown at Fig. 29. It consists of _b_, _b_, a body of beech wood,
hollowed for half its length, in which space the priming charge
is placed; it is also perforated by three holes, one vertical for
the reception of the capsule of sensitive mixture, the other two
horizontal, in which the conducting wires are placed; _a_, _a_ are two
insulated copper wires, passing into the vertical hole, and resting
on the sensitive mixture; in a cavity, _d_, of the body of the fuze
is placed some mealed powder, which is fired by the ignition of the
sensitive mixture on the passage of the electrical current.

The insulated wires used in connection with this fuze consist of two
copper wires, about 2 inches long, and ·022 inch in diameter, enclosed
in a covering of gutta percha ·13 inch in diameter, and separated about
·06 inch from each other.

At one end the wires are bared to 1·25 inch, at the other they are
merely cut across by a very sharp pair of scissors. This end of the
double covered wire is inserted into a paper cylinder _c_, _c_, which
holds a small quantity of the priming mixture. This capped end of
the wires is inserted into the wooden body of the fuze through the
vertical hole _i_, and projects ·15 inch into the cavity _d_. The bare
ends of the double covered wires are pressed into small grooves in the
head of the cylinder _e e_, and each extremity is bent into one of
the small channels _d' d'_, which are at right angles to the vertical
perforation. _d' d'_ are two small copper tubes driven into these
channels over the wire ends, to keep the wires in position, and to form
the opening into which the conducting wires _f_ are inserted and bent
round, as at _e'_.

The priming mixture of Abel's original fuze, which was the one used
by the Confederates, was composed of 10 parts of subphosphide of
copper, 45 parts of subsulphide of copper, and 15 parts of chlorate of
potash. These ingredients reduced to a very fine state of division, and
intimately mixed, in a mortar, with the addition of a little alcohol,
are dried at a low temperature and preserved in bottles until required
for use. The sensitive mixture used by Mr. Abel more recently for his
submarine electrical high tension fuzes, is composed of an intimate
mixture of graphite and fulminate of mercury. By the process of
ramming, the electrical resistance of the fuze is regulated.

_Extempore Fuzes._--It may be necessary in some cases, when a specially
manufactured fuze is not attainable, to make a fuze on the spot. The
following is a neat and simple method of constructing an extempore high
tension fuze.

_Fisher's Extempore Fuze._--This form of fuze was devised by
Lieutenant now Captain Fisher, R.N. It consists of a small disc of
gutta percha, through which the ends of two wires are inserted about
1/4 inch apart, their ends terminating in small copper plates formed
by hammering down the wire. These flat ends should be fixed parallel,
and in the first place in contact with one another, also should be
level with the surface of the gutta percha. The other two extremities
of the wires are then placed in circuit with a sensitive galvanometer
and a test battery; the needle of the former deflects violently, there
being a complete metallic circuit; the flat ends of the wires or poles
of the fuze are then separated very carefully, until the needle just
ceases to deflect. In the space thus formed, a little scraped charcoal
is placed, and rammed in by a piece of wood. By the application of
pressure, any degree of sensitiveness may be attained, merely observing
the deflection of the galvanometer needle. Over the charcoal a little
powdered resin is shaken, and pressed down, by which means the charcoal
is fixed in position, and owing to the inflammability of the resin, the
ignition of the gunpowder priming is ensured. The disc of gutta percha
is then placed in an empty Snider ball cartridge, &c., and by the
application of a little warm gutta percha applied externally, the holes
where the projecting ends of the wires pass are closed, and the disc is
fixed and insulated. The case is then filled with some mealed powder
and fine grained powder, on the top of which is placed a little cotton
wool, and the whole pressed down tightly with the finger, the open
end of the case being then choked, as in Beardslee's fuze and Abel's
extempore one. The apex is then covered with some warm gutta percha,
and the whole of the fuze coated over with red sealing-wax dissolved in
methylated spirits.

_Insulated Electric Cables._--For the work of defence by electrical
submarine mines, the wires along which the electric current flows have,
on account of their being led underground and through the water, to be
covered with some substance which shall prevent the current during its
passage from escaping to earth, or in other words, they (the wires)
must be insulated.

The substances in general use for such purposes are as follows:--

1.--Gutta percha.
2.--Ordinary india rubber.
3.--Hooper's material.

_Gutta Percha._--This substance was used by Messrs. Siemens in the
cables manufactured by them for the Austrian government in 1866, and is
to some extent still employed, though Hooper's material or vulcanised
india rubber, has been found to be more suitable. The dielectric, gutta
percha, possesses the following advantages:--

_a._--It can be put on the conducting wire, as an
unbroken tube.

_b._--It only absorbs 1 per cent. of water.

_c._--It has the property of clinging to the metallic
conductor, by which is meant, that should it
(conductor) be cut through, and any strain be brought
on the cable, there is a tendency on the part of the
gutta percha to cling to the conducting wire, thereby
not increasing the fault.

The defects of such an insulator are:--

_a._--Its liability to become hard and brittle when
exposed to dry heat, and consequently it requires to be
stored under water.

_b._--It becomes comparatively a bad dielectric at 100°
F.

_c._--It becomes plastic at high temperatures, which
causes the conducting wire to alter its position.

In some particulars ordinary india rubber is a better insulator than
gutta percha, but this substance is equally inferior to Hooper's
material, &c. The advantages possessed by this substance are:--

_a._--It is not easily affected by a dry heat.

_b._--It is a very excellent dielectric.

The defects of this mode of insulation are:--

_a._--It must be put on the conducting wires in a
series of jointed pieces.

_b._--It does not cling to the conducting wire, so that
if the electric cable be cut, and any strain be brought
on it (cable), the previous fault is increased.

_c._--It absorbs 25 per cent. of water.

_Hooper's Material._--This insulating material consists of an inside
coating of pure india rubber, then another similar coating in
conjunction with oxide of zinc, which is termed the separator, and
an outside coating of india rubber combined with sulphur. The use of
the separator is to prevent any damage to the conducting wires by the
action of the sulphur. The three coatings are then baked for some
hours at a very high temperature, which fuses the whole into a solid
mass, and vulcanises the outer coating. The properties of the pure
india rubber which is in contact with the metallic conductor are thus
preserved, while any decay of the outer covering is prevented by the
vulcanising process.

The advantages claimed by Mr. Hooper for this mode of insulating
electric submarine cables, are:--

_a._--High insulation.

_b._--Flexibility.

_c._--Capability of withstanding the bad effects of dry
heat.

The qualifications essential to a perfect insulated electrical cable
for use with submarine mines are as follows:--

1.--Capacity to bear a certain amount of strain without
breaking.

2.--Perfect insulation, or at least as nearly so as
it is possible to obtain, and composed of a substance
capable of being readily stored, and kept for a
considerable length of time without being injured.

3.--Pliability so that it may be wound on, or paid out
from, a moderately sized drum without injury.

4.--Provided with an external covering capable of
protecting the dielectric from injury when used in
situations where there is a rocky or shingly bottom, &c.

The insulated wire of a submarine cable is technically spoken of as its
_core_.

By a _cable_ is meant to be understood any piece of covered wire.

Several forms of submarine electrical cables have been devised, all of
which more or less possess the qualifications enumerated above. The
following are some of the most effective:--

1.--Siemens's cable.
2.--Hooper's cable.
3.--Gray's cable.
4.--Service cable.

_Siemens's Cable._--This form of cable is represented at Fig. 30. It
consists of a strand _a_, which is composed of three or more copper
wires formed by laying up the several single copper wires spirally,
several layers of gutta percha, or india rubber, _b_, two coverings of
hemp, saturated with Stockholm tar, _c_ and _d_, and several plies of
copper tape _e_, wound on, so that each strip overlaps the preceding
one, as shown at Fig. 30. The conductivity of the copper employed for
the strand is equal to at least 90 per cent. of that of pure copper.

This exterior covering of copper tape is a patent of Messrs. Siemens
Brothers, and when once laid down, the cable so covered is very
efficiently protected, and of course it is little affected by the
action of the sea water. This mode of protection has one great defect,
viz., that in the event of a kink occurring in paying out the line, and
at the same time a sharp strain being applied, the copper tape at that
point is extremely likely to destroy the insulation by being drawn in
such a way as to cut through the dielectric. On this account great care
must be observed in handling this form of cable.

In practice precautions must be taken to prevent the copper tape
covering from being brought into contact with any iron, for were such
to happen, electrical action would at once ensue, causing the iron to
corrode with enormous rapidity.

In some of Siemens's cables, vulcanised india rubber replaces the gutta
percha insulation. Iron covered cables, either galvanised or plain, are
manufactured as well as the copper tape covered ones by that firm.

_Hooper's Cable._--This form of cable is represented at Fig. 31. It
consists of a metal conducting wire, generally copper, _a_, covered
with an alloy to protect it from chemical action, the insulating
substance _b_, known as Hooper's material, previously described at page
39, a covering of tarred hemp _c_, and an outer covering of iron wires
(No. 11 B. W. G.), each of which is separately covered with tarred hemp
and wound on spirally, _d_.

Gray's cable is very similar to the one just described, the chief
difference in it as compared with Hooper's being the absence of the
separator.

_Silvertown Cables._--The following is a description of the core of an
electrical submarine cable, which is used by the English government,
and is supposed to contain all the advantages of the foregoing, and
none of their defects. It consists of a strand conductor of four copper
wires (No. 20 B. W. G.) of quality not less than 92 per cent. of pure
copper, and possessing an electrical resistance of not more than 14
ohms per nautical mile. This strand is tinned and insulated with
vulcanised india rubber to a diameter of ·24 inch, and then covered
with a layer of felt, and the whole subjected to a temperature of 300°
F. under steam pressure. This forms the core of the various kinds of
cables employed in connection with a system of defence by electrical
submarine mines, which are enumerated as follows:--

1.--Single core armoured cable.

2.--Multiple cable.

3.--Circuit closer cable.

4.--Single core unarmoured cable.

5.--Special cables for firing by cross bearings.

_Single Core Armoured Cable._--This form of cable is used in connection
with each mine of a group or system, and also to connect forts,
&c. across an arm of the sea. Over the core, which has been fully
described, is laid a spiral covering of tanned, picked Russian hemp,
over this are laid ten galvanised iron wires (No. 13 B. W. G.),
each one of which is covered with a similar hemp, which is laid in
an opposite spiral to the former similar covering, with a twist of
one revolution in about thirteen inches; in order to prevent these
wires from gaping when the cable is kinked, a further covering of two
servings of hemp passed spirally in opposite directions is laid, and
the whole passed through a hot composition of a tar and pitch mixture.
Exterior diameter of this cable is 7/8 inch. Its weight in air is
27-50/112 cwt., and in water 14-40/112 cwt. per nautical mile. The
breaking strain of a cable thus manufactured is 62-1/2 cwt., and its
cost about £47 per nautical mile. A diagram of this cable is shown at
Fig. 32.

_Multiple Cable._--This form of cable is employed in cases where it is
necessary to carry a large number of cables into the firing station,
&c. It consists of seven single cores formed into a strand, over which
a padding of hemp fibres is laid longitudinally, and over this again
is laid an armouring of sixteen (No. 9 B. W. G.) galvanised iron
wires, each one of which is covered with a layer of tarred tape put
on spirally with a twist of one revolution in 15 inches. The exterior
covering consists of two layers of hemp and composition, which is
laid on with a short twist, and in opposite directions. The external
diameter of this cable is 1-1/4 inch. Its weight in air and water is
78-25/112 cwt., and 45-32/112 cwt. respectively per nautical mile.
Its breaking strain is 135 cwt., and cost about £357 per nautical
mile. This form of cable is used in connection with a junction box,
from which the single armoured cables leading to the different mines
radiate, and is shown at Fig. 33.

_Circuit Closer Cable._--This cable, which connects the mine and
circuit closer, has been found to be subjected to exceptional wear and
tear, and therefore requires a special form of exterior protection. The
core of this cable is the same as the one described at page 41, also
it is covered with a similar padding of hemp, but instead of the iron
wires as in the case of the multiple cable, &c., nine strands, each of
which is composed of fourteen No. 22 Bessemer Steel Wires, are wound
on, each such strand being covered with hemp, which is put on with a
twist of one revolution in every 7-1/2 inches, the external covering
being the same as in other cables.

This form of armouring for an electric cable possesses the
qualifications of pliability, lightness, and great tensile strength.
Its weight in air is 52-106/112 cwt., and in water 28-4/112 cwt. per
nautical mile. Its breaking strain 65 cwt., and cost about £127 per
nautical mile.

_Single Core Unarmoured Cable._--This form of cable is used in a system
of defence by submarine mines to connect the detached works of a
maritime fortress, &c., for the purpose of telegraphing.

It consists of the ordinary service core, over which are laid two
servings of tarred hemp, put on spirally. The weight of this cable in
air is 4-13/112 cwt., and in water 1-36/112 cwt. per nautical mile; its
breaking strain is 7-1/2 cwt., and its cost per nautical mile is about
£35.

_Special Cables._--In firing electrical submarine mines by means of
cross bearings, a special cable is employed. As a general rule there
would be three lines of mines placed to converge on one of the stations.

Each of these lines would be provided with a conducting wire in
connection with the firing arrangements, while one line of wire in
connection with the firing station would be required for telegraphing.
For the purpose in question a four cored cable is used.

_Land Service Cable._--The cable employed for this service consists
of a core formed similar to that of the multiple cable, described at
page 41; over which is laid a padding of hemp, and finally two servings
of tarred hemp laid spirally in opposite directions are wound on. Its
weight in air is 16 cwt., and in water 4-50/112 cwt. per nautical mile.
Its breaking strain 17-1/2 cwt., and cost per nautical mile about £137.

_Sea Service Cable._--This consists of a similar core to the land
service cable, and padding of hemp, over which is laid an armouring
of fifteen No. 13 galvanised iron wires, each one being covered with
tarred tape, and finally the ordinary servings of tarred hemp. Its
weight in air is 49-101/112 cwt., and in water 25-109/112 cwt. per
nautical mile. Its breaking strain 65-100/112 cwt., and cost per
nautical mile about £202.

When frictional electricity is used to fire high tension fuzes, it has
been found by experiment that if several lines of insulated cables
are laid in the same trench for a few hundred yards, the inductive
effect of the electrical charge generated by a frictional machine is so
great that its discharge through one cable is sufficient not only to
fire the fuze in immediate connection with it, but by induction every
other fuze in connection with the remaining wires laid in the trench.
And this effect equally occurs when the electric cables are some feet
apart, provided they run parallel for a few hundred yards, and whether
the shore ends of the cables, the fuzes in connection with which are
not intended to be fired, are insulated, or put directly to earth,
the connections beyond the fuzes being to earth, or even insulated,
provided a very few yards of conductor exist beyond the fuze.

The length of wire which it is necessary to use between the mine
and its circuit closer would be quite sufficient for the purpose of
effecting ignition by induction. With platinum wire fuses there is no
danger whatever of the above happening, nor in the case of high tension
fuzes is there so much danger of ignition by induction, when a constant
instead of a frictional electric battery is used to generate the
current.

Another mode of protecting an insulated cable is to place it, as it
were, in the core of a hempen cable. In forming the rope on the cable,
great care is necessary to prevent any serious amount of torsion,
or tension coming on the insulated wire, either of which would most
assuredly result in injury to the cable. This form of cable might in
connection with obstructions, &c., be of great use, as on account of
its closely resembling an ordinary rope, it would be very unlikely to
excite suspicion, and so would most probably be cut, the result of
which, by previous arrangement, would be an explosion of a mine, or by
means of a galvanometer, &c., an indication that the obstructions, &c.,
were being interfered with.

_Jointing Electrical Cables._--This is a very important point in
connection with a system of defence or offence by electrical torpedoes.
In many instances it will be found necessary to join either two lengths
of cable, or an insulated wire and a cable, together, in both of which
cases, great care must be used in making the joints, so that the
insulation and the continuity of the circuit may be perfect.

[Illustration: ELECTRIC CABLES, EXTEMPORE CABLE JOINTS.

PLATE VIII]

Many species of junctions have been from time to time devised, the most
practical and generally employed of which are:--

1.--India rubber tube joint.
2.--Mathieson's joint.
3.--Beardslee's joint.
4.--McEvoy's joint.
5.--Permanent junction.

_India rubber Tube Joint._--This form of joint is a very useful one
for extempore purposes, being easily and quickly made, and being very
effective. At Fig. 34 is shown a sketch of such a junction. About 1·5
inches of the copper conductor of the two insulated cables are laid
bare and connected together by means of Nicoll's metallic joint, as
shown at Fig. 36, or by turning one of the conductors round the other,
their ends being carefully pressed down by means of pliers, to prevent
any chance of the india rubber tube being pierced; over the splice thus
formed serve some twine, and over the whole put a coating of india
rubber cement, grease, &c., then draw the vulcanised india rubber
tube, which has been previously placed on one of the insulated cables,
over the splice _a_, as shown at _b_, and secure it firmly by means of
twine, _c_, _c_, and then to prevent any strain being brought on the
joint, form a half-crown as shown in Fig. 35 at _A_.

In forming the splice, it is very important that the metallic ends
should be perfectly clean. The danger to this mode of jointing of the
piercing of the tube by the ends of the conductors is entirely removed
by employing the Nicoll metallic joint, which is formed as follows:--

_Nicoll Metallic Joint._--One of the conducting wires, as _a_, Fig. 36,
is formed into a spiral twist by means of a very simple instrument,
and the other wire _b_, which is left straight, is inserted into the
spiral, the whole being placed on an anvil, and pressed closely and
securely together by a single blow of a hammer.

_Mathieson's Joint._--This somewhat complicated, though very effective
mode of jointing, which is adopted in the English torpedo service, is
shown at Fig. 37, in elevation and section. It consists of two ebonite
cylinders _a_, _a_, through which the cables to be connected are
passed. Within these cylinders an ebonite tube _b_, _b_ is placed, the
ends of which are wedge-shaped, and which press against two vulcanite
rings _c_, _c_; in the interior of this tube _b_, _b_ is the metallic
joint _d_ of the two cables. The centre of the tube _b_, _b_ is of
square section, and fits into a hollow of similar form in the cylinders
_a_, _a_, the object of this being to prevent any twisting of the
wires during the process of screwing up, which would be liable to
injure the metallic joint _d_.

The manner of making this joint will be easily understood from the
figure. With this, as with all other temporary joints, it is advisable
to form a half-crown in the cable, including the joint.

_Beardslee's Joint._--This form of temporary joint when used with
strand conductors, which are composed of a number of small wires, has
been found to be exceedingly useful and effective, the only defect of
such a joint being the liability of straightening the wires of the
conductors should a direct strain be brought upon the wire extremities.
Fig. 38 represents a section of this joint; it consists of an ebonite
cylinder _a_, one end of which is solid, and the other open and fitted
with a screw thread, into which is screwed a plug _b_; through both the
plug _b_, and the solid end of the cylinder _a_, perforations are made
just large enough to admit the insulated wires _c_, _c_; about half an
inch of the extremities of these wires are bared and cleaned, and then
passed, the one through the plug _b_, a disc of vulcanised india rubber
_d_, and a metal disc _e_, and the end of the strand conductor turned
back on the face of this metal disc, the other through the perforation
in the solid end of the cylinder _a_, then through similar discs _d_
and _e_, and the end of the strand conductor treated in the same
manner as the former one; then by means of the screw plug _b_, the two
metallic discs _b_, _b_, and consequently the bare extremities of the
strand conductors are brought into close metallic contact.

_McEvoy's Joint for Iron Wire covered Cable_.--This form of joint is
shown in section at Fig. 39. Two brass caps _a_, _a_ are slipped over
the ends of the cables required to be joined, then the iron wire and
other coverings of the cables down to the insulating substance are
removed, the former being bent back close against the bottom of the
caps _a_, _a_, as shown in Fig. 39 at _b_, _b_; the cores of the cables
are then joined by an india rubber temporary joint _c_, which has been
described at page 45: the whole is then placed in the body of the
joint, and the brass caps _a_, _a_ screwed up, jamming the bent back
iron wires against a solid piece of brass _d_, _d_, by which means a
firm and perfect joint is made in the cables.

[Illustration: PERMANENT JOINTS FOR ELECTRIC CABLES.

PLATE IX]

Fig. 40 represents a section of a McEvoy temporary joint for single
cored unarmoured cables, which seems to fulfil all the conditions
necessary to a perfect joint of that description. This joint is, with
the exception of there being two screw plugs instead of one, very
similar to Beardslee's joint described at page 46; this alteration is a
great improvement, remedying as it does the one defect of Beardslee's
joint, viz., the liability of the cables to be drawn apart due to any
great tension being brought on them.

A permanent joint in electrical submarine cables, which from its nature
requires to be an exceptionally good one, is a somewhat difficult and
troublesome operation, and also requires a considerable time to form a
thoroughly reliable one.

_Siemens's Methods of Jointing._--The following methods, and
instructions for forming such joints, are those adopted by Messrs.
Siemens Brothers in connection with their telegraph cables, and which
will be found generally applicable to all insulated cables.

_The Formation of a Joint in the Conductor of an Insulated Cable._--The
conductor is either covered with a gutta percha or an india rubber
dielectric. In both cases cut off the dielectric so as to bare the
conductor-wire for a length of about three inches, taking care never to
cut at right angles to the conductor-wire, for fear of injuring it with
the cutting-knife or scissors.

Then clean the wires forming the strand with file-card and emery-paper,
and solder them into a solid bar for a length of about one inch.

Having soldered the wires, forming the ends of the two lengths of
conductors to be joined, into two solid rods, file each of them off
in a slanting manner, so that they will form a scarf-joint when put
together.

Place the two ends of strand in the two small vices on a stand which
is supplied for the purpose, so that the two scarfed ends overlap each
other, and bind them round with a piece of fine black iron wire, in the
shape of a spiral, so as to keep the ends close together, then solder
the two ends together by applying a hot soldering iron.

Then remove the iron binding wire and clean up the joint, filing off
all unnecessary solder.

And make a band of four fine tinned copper wires, and bind them tightly
side by side round the joint, covering the whole length of the scarf,
and then solder the band and joint solidly together.

Then make another band of four fine tinned copper wires and bind them
round the joint in the same manner as before, but extending about a
quarter of an inch beyond each end of the other binding wire, the
parts only of this second binding which project beyond the end of the
first binding are to be soldered, so that the centre part remains loose
and may keep up a connection between the two ends by forming a spiral
between them in the event of the scarf giving way and the two ends of
the conductor separating slightly.

This form of joint is called the "spring" joint.

The finished joint should be washed with spirit of wine and brushed, so
as to take away all particles of soldering flux, and to avoid oxidation
of the wire. The washed joint should then be dried with a piece of
cloth and exposed to the flame of a spirit lamp to dry it thoroughly.
A cable conductor ought never to be jointed with the help of soldering
acid, but with that of resin, sal ammoniac, or borax only, so that any
chance oxidation, and consequently destruction, of the conducting wire
may be avoided.

There are other modes of jointing conductors, such as the twisting and
scale joint, but the foregoing method will sufficiently explain this
part of electric cable work.

_The Formation of a Joint in an India rubber Insulated Cable._--In
making a joint in any insulated cable, the very greatest care must be
taken to keep the hands, tools, and materials clean and dry.

Remove the felt for about twelve inches from each end of the core by
soaking it with mineral naphtha and then rubbing it off clean with the
file-card. The cleaned surface sear with a red-hot iron, to burn off
all remaining fibres of the felt. Wash these seared ends clean with
naphtha.

Then cut off about four inches of the insulating material (taking
care never to cut at right angles to the conducting wire for fear of
injuring it) so as to leave enough of the conductor bare to join and
solder in the manner described at page 47.

After the conductor is jointed and soldered, clean again the seared
parts of the insulator with the glazed side of the squares of cloth
moistened with mineral naphtha, so as to leave a clean adhesiveness
only; taper again the insulating material down to the conductor for
about two inches on each side of the conductor-joint with a pair of
curved and very clean scissors.

The tapering must be completed in such slanting way that the different
layers of the dielectric are so far exposed as to enable a secure
laying on of the new jointing material.

India rubber core consists chiefly of three layers of insulating
material: the first layer next to the strand is called the pure or
brown; the second layer is the white or separating; the third layer is
the light red or jacket rubber.

Coat the conductor with a pure (brown) rubber tape tightly laid on
in a spiral form, commencing at the spot where the separator (white)
ends, across the corresponding place on the opposite side of the joint
and back again in a contrary direction. The ends are fastened down by
pressing a clean, heated searing-iron or a heated knife on them. By
doing so the band will stick; the remaining portions of the band to be
cut off with the scissors.

Lay on tightly the separating india rubber tape in the same manner, but
beginning where the jacket or outer layer of rubber ends. One lap will
be sufficient.

Complete the insulation by lapping on tightly two layers of red india
rubber tape: the last lap must cover each end of the core to four
inches on each side of the conductor-joint, or extend to the searing or
tackiness, but not beyond it.

Lay on three tight bindings of the cloth tapes, all in the same
direction, care being taken to avoid wrinkles. The ends of the cloth
tapes are cemented down with a thin coating of india rubber cement.

Immerse the joint in the jointing-bath at 150° to 200° F. and gradually
raise the heat so that in half an hour the temperature will be 320° F.,
at which temperature keep the joint for twenty minutes: then take it
out and let it cool in the open air.

_The Formation of a Joint in a Gutta percha Insulated Cable._--Having
jointed the conducting wires in the manner described at page 47, clean
and dry the joint well and cover the bare conductor with a thin layer
of compound. This is best done by heating a small stick of compound to
nearly its melting point, and rubbing it over the bare conductor, which
has been previously heated with the flame of a spirit-lamp.

Heat the gutta percha covering of both ends gently until it is quite
soft, without, however, causing it to bubble or burn. Draw, then, with
the fingers, the gutta percha coverings of both ends down, tapering
them off until they meet in the middle of the joint; heat them
sufficiently to make them adhere together.

Apply a layer of compound on the tapered-off gutta percha in the same
manner as described for coating the bare conductor, and cover it with
a first coating of gutta percha sheet to about half the thickness
necessary to finish the joint. This is done by heating a small sheet
of gutta percha, of about one-eighth of an inch in thickness, until it
is quite soft, and by pressing it in that state round the joint to the
required size; the greatest care to be taken to expel all the air.

The projecting lips are then cut off with a pair of curved scissors.
The seam thus produced is to be rubbed with a hot iron until it is
completely closed and the joint well rounded off.

Apply another layer of compound and a second layer of gutta percha
in exactly the same manner as described for the first layer; care,
however, is to be taken to get the seam in this second layer of gutta
percha not over, but as nearly as possible right opposite to, the seam
in the layer underneath.

The whole to be worked as cylindrical as possible, and to a size not
exceeding the original core. The joint, so far finished, is then to be
cooled with water until the gutta percha is quite consolidated.

Another, the overlapping gutta percha joint, is made in the following
manner:--

Cut off the two ends of the core, so that the gutta percha and the
conductor-wire are flush. Warm the gutta percha for a distance of
about three inches from each of the ends with the flame of a spirit
lamp, and, when sufficiently soft, push it back until it forms an
enlargement. The two ends of the conductor are then to be soldered
according to instructions for making joint in conductors.

To have a perfectly clean surface of the two gutta percha enlargements,
remove all impurities by the way of peeling them with a sharp knife.
Warm gently both knobs and the copper joint, and cover the whole length
of the bare wire with compound, planing it with a warm smoothing-iron.

Draw then with the fingers one of the warmed and softened knobs
carefully up to the other knob or enlargement, leaving on its way
a perfect tube of gutta percha upon the wire, decreasing gradually
to the thickness of the copper strand towards the other knob. Any
superfluous gutta percha is removed. This scarf is finished with a warm
smoothing-iron, so as to unite it to the compound on the wire strand,
and a thin layer of compound is also put over the scarf in the same
manner as before.

The other knob is then warmed and drawn in the same way over the tube
already formed, which is at the same time heated sufficiently to make
the two adhere.

Apply a layer of compound on the second scarf of gutta percha, covering
it in the same manner as described for coating the bare conductor,
and cover it with a small sheet of gutta percha in the same manner as
described above, so as to make the finished joint to the size of the
core as manufactured.

_Rules to be observed in forming Joints._--The following rules must be
carefully observed in forming either a temporary or permanent joint:--

1.--In laying bare the conductor, the dielectric should
be warmed and then pulled off, so preventing any chance
of it being damaged, which might be the case were the
dielectric to be cut off.

2.--For a perfect junction, soldering is necessary.

3.--The wires before connection should be carefully
cleaned, and the hands of those performing the work
must be dry.

4.--Gutta percha should not be given too much heat,
for it then becomes oily and will not, in that state,
properly adhere.

5.--Grease and dirt must be scrupulously avoided.

Great care is absolutely necessary in making junctions, as they are the
principal sources of defect in the insulation of electrical submarine
cables.

_Junction Boxes._--When it is necessary to employ a multiple cable,
a junction box is used to facilitate the connection of the several
separate wires diverging from the extremities of such a cable. In
one angle of such a box the multiple cable is introduced, while the
separate cables make their exit on the opposite sides and pass to the
different mines. Different views of a junction box are shown at Fig.
41, where _A_ is a plan of the top or lid, _B_ a plan of the bottom,
with the lid off, _C_ an elevation, and _D_ a section of the box.

The manner of using the junction box is as follows:--

The multiple cable is put in at _a_, and secured there by means of a
nipping hook, shown at Fig. 42, which hook passes through the bottom
of the junction and is made secure by means of a nut. The single core
cables radiating from the junction box pass through the openings _b_,
_b_, _b_ on the sides, and angle opposite to where the multiple cable
a enters. Each multiple cable is composed of seven cores, and each of
these is connected by means of joints with the mine cables within the
junction box, and each of these seven cables is secured by means of a
nipper similar to, but smaller than, the one shown at Fig. 42, which
are also secured by means of nuts, as in the case of the multiple cable
nipping hook. When all the connections are made, the lid _A_ is placed
so as to rest on the studs _c_, _c_, _c_, and firmly secured by a bolt
_d_, which is made water-tight by means of a washer and nut.

By means of the nipping hooks, which take any strain that may be
brought on the cables, the connections within the box are ensured
against injury by such a cause.

To enable the whole to be lifted together for the purposes of
examination of the cables, &c., a buoyed rope is connected to the
eye-bolt _e_. For this service a dummy circuit closer is the best form
of buoy, it having great buoyancy and resembling in appearance an
active circuit closer.

A junction box should be placed in such a position as to be easily
attained, even in the presence of an enemy, and its buoy should, if
possible, not be seen. It is also very essential that it should be in
a safe and guarded position, for any injury to the junction box or
multiple cable would be fatal to the group of mines in connection.

In the following cases, special junction boxes are used:--

1.--A seven cored armoured cable to be connected direct
to another length of the same.

2.--A single armoured cable to be connected as in
foregoing instance.

3.--A T junction box for the branch system of
electrical contact mines.

_Junction Box for Multiple Cables._--At Fig. 43 is represented a plan
of lower half of this form of junction box. It consists of a pair of
cast iron plates of precisely similar form to the one shown at Fig.
43, and so made as to be capable of being fastened tightly together by
means of four bolts and nuts passing through the holes _a_, _a_. The
grooves _b_, _b_ at the two extremities are just large enough to grip
the armoured cable firmly, when the upper and lower parts are screwed
together. A larger space is provided in the hollow for the joint.

_Junction Box for Single Cored Cables._--For this purpose a junction
box similar to, but smaller than the one above described is employed.

_T Junction Box._--This form of junction box is employed when the
system of electrical contact mines on branches from a single cable is
used. This system is dependent on the use of a platinum wire fuze in
connection with a platinum wire bridge in each branch close to its
junction with the main cable.

This form of junction box, which is shown at Fig. 44 is very similar
to the one used for the connection of two multiple cables, only
differing in its shape, which is that of a T. _a_ is a disconnector,
which will be described further on; _b_, _b_, _b'_ are the armoured
electric cables, _b_, _b_ being the main, and _b'_ the branch cable in
connection with the forked joint formed within the T junction box; _c_,
_c_, _c_ are Turk's heads formed to prevent any strain being brought on
the forked joint. This form of Turk's head is made by turning back the
wires of the cable armouring, and frapping them round with spun yarn
until the necessary size and shape is attained.

_McEvoy's Turk's Head._--Another form of Turk's head, devised by
Captain McEvoy, is shown at Fig. 45. It consists of two separate pieces
of brass, _a_ and _b_, the former screwing over the latter. The mode of
using it is as follows:--

Slip the piece of brass _b_ over the cable _c_, and turn back the wires
of the cable _d_, _d_, &c., so that they lie against the shoulder of
the brass piece _b_, then slip the other piece of brass _a_ over the
cable and screw it on the piece _b_, firmly jamming the turned back
wires _d_, _d_, &c. This is a very neat and quick method of forming
a Turk's head, and it should be invariably used in preference to the
foregoing method, which is clumsy, and which takes some time to form.

The section of a disconnector is shown at Fig. 46. It consists of an
iron cover, or dome _a_, which is provided with a screw fitting on
to another screw on the ebonite body _b_ of the apparatus. When the
dome _a_ is screwed tightly down on the washer _i_, the whole is made
perfectly watertight. _c_, _c_ are insulated terminals for connecting
the cores of the branch and main cables after their armouring has been
removed, as shown at Fig. 44. _d_, _d_ are two copper conducting wires
(No. 16 B. W. G.) passing through the centre of the ebonite body _b_,
and projecting into the interior of the apparatus. These wires are
held in position and insulated by means of a composition formed of a
mixture of pitch, tallow, beeswax and gutta percha. This composition
is put on whilst hot and allowed to cool gradually, when it becomes
hard and durable. Great care is necessary to ensure the cavity within
the ebonite body _b_ being completely filled, as otherwise a leakage
might occur, owing to the great pressure of water at depths where the
disconnection would be generally used. _f_ is a boxwood cover which is
slipped on, and fits fairly tight to the ebonite body _b_; _g_ is a
piece of thin platinum wire, weighing 1·6 grains to the yard, and being
4/10 inch in length; _h_ is an ebonite pin, which passes through two
small holes in the boxwood cover _f_, into which it fits tightly, and
in such a position as to be directly beneath the platinum wire bridge
_g_, when the boxwood cover _f_ is fixed on. The pin _h_ is pushed
through the holes in the cover _f_ from the outside, so as to pass
beneath the bridge _g_ after the priming has been inserted, and the
cover has been placed on.

When prepared for use, the platinum wire bridge _g_ is surrounded by
some loose gun-cotton priming, sufficient in quantity to blow off the
boxwood cover _f_, without destroying the dome _a_; the cover _f_
being blown off, carries the ebonite pin _h_ with it, and through
the platinum wire bridge _g_, thereby rupturing it, and breaking the
continuity of the circuit. The object of so doing is to cut off the
connection of an exploded mine, so that the full amount of the firing
current is available for the other mines, and not suffered to be wasted
by passing through the exposed wire of the broken circuit, which, were
the disconnector not employed, would be the case.

When any particular mine of a system is struck, the current passes
through the main cable _b_, the disconnector _a_ (which is in
connection with that mine), and branch cable _b'_ to the fuze, and so
explodes the mine, and destroys the platinum wire bridge _g_ of the
disconnector at practically the same instant. The effect of the latter
operation would be to cut off and insulate the branch cable of the
exploded mine, and so prevent any loss of the electrical current, when
another mine of that system is required to be fired.

The platinum wire bridge _g_ is 4/10 inch long, while that of the fuze
is 3/10 inch, the object of this difference in length of the bridges
being to ensure the former one _g_ being fired, and thus the insulation
made doubly sure. Many other forms of disconnectors have been devised,
but none have proved in practice so effective as the one just described.

[Illustration: JUNCTION BOXES. MECHANICAL TURK'S HEAD.

PLATE X]

_Mooring Electrical Submarine Mines._--This is one of the most
difficult problems to be solved in connection with a system of
submarine mines. The objects to be attained in mooring are as follows:--

1.--The mines should preserve the exact positions in
which they are laid down.

NOTE.--From the comparatively small radius of destructive effect,
of even heavily charged submarine mines, it will be understood how
absolutely essential, in the case of mines fired by judgment, it is
that this object should be attained.

2.--The mooring chains, or ropes, must be so arranged
that no twisting whatever should occur, as otherwise
fracture of the insulated wire would be likely to
happen.

3.--In the case of buoyant mines, their distance from
the bottom must be so adjusted, that at no time shall a
vessel passing over them be out of their vertical range
of destruction, nor shall they be visible.

The difficulties attendant upon the efficient mooring of submarine
mines are immense, as will be understood when the action of gales
of wind, and strong tides, which latter vary continually in their
direction and in their rise and fall, are taken into consideration.

The foregoing remarks apply more particularly to a system of buoyant
submarine mines, as those placed on the ground are comparatively easy
to moor.

Several modes of mooring buoyant submarine mines have been suggested,
the most practicable of which are as follows:--

1.--Ladder moorings.
2.--Fore and aft moorings.
3.--Austrian method of mooring.
4.--Single rope mooring.

_Ladder Mooring._--This is a method of mooring, which in places where
it may be necessary to place the anchors far apart will be found useful.

The circuit closer is connected to the mine by two ropes which lead
thence to two anchors, the ropes being separated by wooden rounds,
or spreaders, 1 to 3 feet long, by which the tendency to twisting is
prevented.

The anchors are placed some 12 feet apart.

The only defect of the ladder mooring is the quantity of sea-weed, &c.,
that is liable to be lodged on the rounds, thus causing the circuit
closer to be drawn out of its proper position.

_Fore and aft Mooring._--This mode may be advantageously employed in a
tideway where the current runs very strong, that is to say, five knots
per hour, or more. It consists simply of two anchors, one of which is
moored up, and the other down the stream.

_Austrian Method of Mooring._--This method of mooring, adopted by the
Austrians during the war of 1866, is shown at Fig. 47. It consists of
a wooden triangular platform on which several heavy weights _a_, _a_,
_a_ are placed; the mine is attached to this platform by means of three
wire ropes _b_, _b_, _b_, connected to the angles of the latter, and
fastened to three chains, which by means of a catch holds the mine at
the position required.

This catch consists of a pulley attached to the extremity of the wire
rope of the platform, through which the mooring chain of the mine is
passed, and fastened by a key at the required depth by means of a
self-acting arrangement.

This key, which is of considerable weight, slips down as the mine is
being hauled into position, but the moment the chain is slacked, two
arms catch into a link of the chain, and so hold the mine in position.
The weight of such a key is about 60 lbs. It is fitted with nuts, &c.,
to enable it to be taken to pieces.

This plan of mooring proved very effective in the harbours of the
Adriatic, where there is hardly any tide or current to twist the
mooring ropes, or otherwise disturb the mines. The Austrians have
lately adopted the mushroom sinker in place of the wooden platform and
weights, for their anchor.

_Single Rope Mooring._--This simple method of mooring has after
numerous exhaustive experiments been adopted as the most practicable
and effective of all others. Whenever possible, a wire instead of
hempen cable should be used to connect the mine and its circuit closer
to the mooring anchor, as the former is less liable to twist, kink, or
wear from friction than the latter.

A ground mine with circuit closer attached is represented at Fig. 48,
where _a_ is the wire mooring rope, _b_ the electric cable leading from
the mine to the circuit closer, _C_, and _c_ the cable leading from
the firing station to the mine; _d_ is the oblong sinker attached to
the mine, and _e_ the tripping chain leading to the shore, to which
the cable _c_ is attached at intervals, so that by underrunning the
electric cable, the tripping chain may be easily picked up, and the
mine raised.

[Illustration: MOORINGS FOR SUBMARINE MINES.

PLATE XI]

At Fig. 49 is shown a buoyant mine. The only difference in the mooring
of this and the one before described, is that instead of resting on
its anchor on the ground, it is moored at a certain distance above its
anchor _d_, to which it is secured by a chain _e_.

Fig. 50 represents an electro contact mine. _M_ is the mine with
circuit closer enclosed, _a_ the wire mooring rope, _d_ the mushroom
anchor, and _b_ the electric cable leading from the mine to the
disconnector _D_.

The mushroom sinker or anchor, which is undoubtedly the most effective
of all other forms of mooring anchors used for the purposes of
anchoring submarine mines, is shown at _e_, Fig. 49; the legs are added
for use on rocky or hard bottoms, under which circumstances the weight
of the anchor should also be increased.

For ground mines the form of sinker shown at _d_, Fig. 48 is employed;
it is of an oblong shape, and hollowed out in the centre to allow of
its being lashed close up to the mine.

Large blocks of stones with their bases slightly hollowed are useful as
extempore moorings, so also is the one shown at Fig. 51, which consists
of a strong heavy wooden shaft _a_, with a number of wooden arms _b_,
_b_ attached to its base; this form of extempore sinker was considered
very efficient by the American authorities.

The wooden weighted platform, which was described at page 56, is also a
very useful form of extempore sinker.

For dead weight moorings, pigs of ballast, heavy stones, &c., may be
used.

The weight of the anchor or sinker for mooring submarine mines is a
very important consideration. It will depend on the amount of buoyancy
of the mine, on the strength of current, and on the nature of the
bottom, also whether the mines are to be hauled down to, or moored with
the anchor.

Stotherd uses the following formula:

W = [2rt](B^{2} + P^{2})

where B is the excess of the flotation over the weight of the charge of
a given submarine mine;

P is the pressure exerted by any given current on the same buoyant mine;

W the weight of sinker necessary to overcome the tendency of the
mine to move. In still water P becomes nothing, and therefore W equal
to 2 B, that is, in still water double the buoyancy of a mine is a
sufficient weight for its anchor.

The value of P may be found from the formula P = 4·085 × V^{2}, where V
is the velocity of the current in miles per hour.

From this equation P will be found in terms of pressure in pounds per
square foot of flat surface, which is nearly double that on the curved
surface of a cylinder.

In regard to the amount of buoyancy of a submarine mine, it has been
found by actual practice that in the case of a mine moored in still
water it should certainly be not less than the weight of the charge,
whilst if subjected to the lateral pressure due to a current, it should
be not less than three times the pressure exerted by the current.

It is always necessary to allow an excess of buoyancy over the
calculated amount to counteract any leakage, or other disturbing cause
which might otherwise materially affect the efficiency of the mine.

There are two modes of placing a mine in position; either by attaching
the anchor, with the cable necessary for the depth of water, to the
mine, and lowering both together, or by placing the anchor first, and
then hauling the mine down to it, and by means of a catch, fastening it
at the required depth.

The first mode is exceedingly simple, but except under very favourable
circumstances cannot be relied on when firing by observation is the
means adopted to explode a system of submarine mines. The second plan
is practically easy to carry out, and by it a mine may be placed more
accurately. To enable either of the above methods to be properly
carried out, specially fitted steamboats, &c., are requisite.

At Fig. 52 is represented a 42 feet launch fitted for laying down a
submarine mine by the first of the two modes enumerated above.

[Illustration: STEAM LAUNCH FOR MOORING SUBMARINE MINES.

PLATE XII.]

_a_ is the mine; _b_ is the electric cable carried from the drum _c_
to the charge, and connected for use; _d_ is the circuit closer, which
is attached to the mine by its electric cable and mooring rope; _f_
is the mushroom sinker attached by means of its mooring chain to the
mine, it is suspended by a slip rope _g_, which passes over a small
crutch fitted with a sheave _h_; _i_ is a hollow iron derrick, and _k_
the tackle and fall for lifting mine into boat; this derrick is formed
of an iron tube about 3 inches diameter, 3/8 inch thick, and 10 feet 6
inches long; it is attached to an iron tube mast of similar diameter
and thickness to the derrick, but 12 feet 3 inches long, an iron chain
6 feet 6 inches long and 5/8 inch diameter, connects the derrick to
the mast; _m_ is a leading sheave to keep the cable clear whilst it is
being paid out; _l_ is a crab, for working the tackle _k_, &c., and _c_
is the drum on which the electric cable is wound.

In connection with the defence of a harbour by a system of electrical
submarine mines of large size, it will be necessary to employ a service
of steamtugs, steamboats, mooring-barges, &c., specially fitted for
such work. One of the great advantages of the hauling down method
of placing mines in position, is, that the anchors, with the cables
connected thereto, may be carefully and accurately got into position
during the time of peace, and the mines themselves, which should be
kept in store ready fitted for immediate use, need not be placed in
position until they are actually required. The drums used for reeling
a multiple cable on, are capable of holding half a nautical mile in
length. That used for a single core armoured cable is similar to but
smaller than the aforesaid drum, and is capable of stowing one nautical
mile of such a cable. For transportation wooden drums are ordinarily
used.

CHAPTER IV.

DEFENSIVE TORPEDO WARFARE--_continued_.

_CLOSING the Electric Circuit._--In connection with the system of
coast defence by means of electrical submarine mines, there are two
distinct methods of effecting the closing of the electric circuit, and
consequently, the firing battery being connected, the explosion of the
mine or mines, which methods may be used separately, or in combination,
and are as follows:--

1.--The self-acting method.
2.--The firing by judgment, or observation method.

During the early days of submarine defensive warfare, the latter method
alone was used, owing to the absence of anything like a practicable
form of self-acting apparatus; but within the last few years, the
former has almost entirely superseded the latter method, except in very
exceptional cases; this revolution being due to the vast improvements
that have been, and still are being effected in the system of firing
electrical submarine mines automatically.

_Use of Circuit Closers._--Electrical submarine mines may by means of
an apparatus, termed a _circuit closer_, be rendered self-acting; that
is to say, by the action of a vessel coming in contact with such an
apparatus, which may be either within the mine itself, or within a buoy
attached to the mine, the electric circuit is closed, and the mine in
connection with the circuit closer so struck, exploded. The essential
feature of such a mode of closing the electric circuit is, that
electrical submarine mines may be rendered either active or harmless,
at the will of the operator, which is effected by the putting in, or
taking out of a plug, by which means the firing current is either
thrown in, or out of the circuit.

_Circuit closers._--Many different forms of circuit closers have been
devised, among which the following seem the most suitable and are those
generally used:--

1.--Mathieson's inertia circuit closer.
2.--Mathieson's spiral spring circuit closer.
3.--Austrian self-acting circuit closer.
4.--McEvoy's mercury circuit closer.
5.--McEvoy's weight magneto circuit closer.

_Mathieson's Circuit Closer._--This form of circuit closer has been
adopted by the English government in connection with their system of
defence by electrical submarine mines.

The details of this apparatus are shown at Pl. xiii.

Fig. 53, _a_ is a gun-metal dome screwed on to a metal base _b_, its
foot resting on a gutta percha washer _c_, so as to exclude any water;
_d_ is a cap screwed on to the top of the dome, and made watertight
by the leather washer _e_; _f_ is a guard cap screwed into the cap
_d_, this is to keep the spindle of the circuit closer steady during
transport, and would be removed when the apparatus is prepared for
service; _g_ is the ebonite base plug through which pass the insulated
wires _E_ and _L_; _h_ is an hexagonal collar, working in the metal
base plate _b_, by means of which, and the brass collar _i_, and the
leather washer _k_, the base plug is secured, and water is excluded
from the interior of the circuit closer; _l_, _l_, _l_ are brass
columns supporting a circular ebonite piece _m_; _n_ is a metal bridge
screwed on to the base plate _b_, into which is screwed the spindle
_p_, both of which are prevented from moving after being screwed up by
the set screws _r_ and _s_.

The spindle _p_ carries a leaden ball _t_, which is supported upon the
rest _v_, and is secured in position by the screw nut _w_; _x_ is an
india rubber ring, the object of which is to prevent any damage being
done to the spindle should the ball when set in action by a heavy
blow from a passing vessel be brought into contact with the dome; 2
is a brass disc attached to the spindle carrying an ebonite disc 4,
connected to it by screws; 6 is a brass contact ring also fixed to the
ebonite disc 4, provided with a screw 8, for the attachment of one of
the base plug wires, and with platinised projections 3, 3, 3, Fig.
56. The contact ring 6 is completely insulated from the spindle and
brass disc 2. Three contact springs 5, are attached to the circular
ebonite piece _m_, and the faces opposite to the platinised projections
of the disc 2 are also platinised. 7 shows the contact screws of the
connecting pieces, which serve also as adjusting screws to regulate the
sensitiveness of the apparatus, the points of which as well as their
bearings on the springs are platinised.

The springs are connected together by means of the wires 9, Fig. 55,
one end of which is secured to the connecting piece by the screw 10,
and the other passes through to the top of the ebonite piece, and is
attached to the top of the spring next in succession to that to which
it is fixed below.

One terminal of a coil of 1000 ohms resistance (which is used for
testing purposes) is attached to the line _L_, terminal of the
ebonite base plug, which latter is also connected to the screw 8, on
the circumference of the contact ring 6; the other terminal of the
resistance coil is connected to the earth, _E_ terminal of the base
plug.

A bare copper wire of No. 16 B. W. G. connects the top of the last
contact spring with the set screw _s_; a piece of similar wire jointed
to it is passed round one of the brass collars and connected to the
screw _r_. As a precaution against bad contact, the contact springs
are connected together by bare wires _A_, _B_, _C_. This completes the
connections for the signalling circuit, the earth being formed by the
body of the instrument; _D_ is a hole left in the metal base for the
passage of the insulating wire which connects the earth plate to the
earth _E_ terminal of the base plug.

_Testing Current._--For testing purposes the current from the test
battery arrives by the line wire _L_, and passes thence through the
resistance coil to earth by means of the wire _E_, which is attached
to a zinc earth plate placed in a recess in the jacket of the circuit
closer.

_Action of the Circuit._--The action of the apparatus is as follows:--

_Closer._--On the circuit closer being struck, the weight of the lead
ball _t_ causes the steel rod _p_ to be deflected and brings the brass
ring 6 in contact with one of the springs 5; the signalling current
which up to this moment has been passing through the 1000 ohms coil
to earth, then passes to the contact ring 6 (avoiding the resistance
coil) thence to the spring which is in contact with it, and from there
by means of the wire connections to the set screws _s_ and _r_, and so
to earth through the metal body of the apparatus; the effect of the
resistance coil being thus eliminated, is to strengthen the signalling
current, and thus enable it to work the shutter apparatus, by which
means the firing current is thrown into circuit and the mine exploded.

[Illustration: MATHIESON'S CIRCUIT CLOSER.

PLATE XIII]

_Circuit Breaker._--By altering the mode of connecting the wires, the
above apparatus may be used as a circuit breaker, that is to say, the
signal may be given, and the mine exploded by the cessation of a
passing current, instead of by the closing of the electric circuit.
This system was specially designed for use with platinum wire fuzes,
but is rarely used.

_Circuit Closer of Electro Contact Mines._--When the inertia circuit
closer is employed in connection with electro contact mines, the
circular ebonite piece _m_ is replaced by a similar shaped piece of
brass, and which is in metallic connection through the brass pillars
_l_, _l_, _l_ with the mass of the metal of the apparatus which forms
the earth plate.

The insulated wire of the base plug is connected to one pole of a
platinum wire fuze, the other pole of which is connected by another
wire to the outer metal rim of the disc of the spindle. As long as the
circuit closer remains undisturbed, a break will remain in the circuit,
which is due to the ebonite insulation between the spindle and the
outer metal rim of the disc; but the moment the apparatus is struck,
which causes the spindle to vibrate, the outer metal rim will come in
contact with one of the springs completing the circuit, through the
circular metal portion and the pillars of the circuit closer to earth.

_Adjustment of Circuit Closer._--The sensitiveness of Mathieson's
inertia circuit closer is determined by the distance between the
disc 4 and the springs 5, 5, 5, which is regulated by means of the
adjusting screws 7, 7, 7, which press against the inner faces of the
springs. Owing to the great weight of the leaden ball, when by any
cause the circuit closer is inclined for a length of time, a permanent
set is given to the spindle, thereby destroying the adjustment of the
instrument.

_Improvements in the Inertia Circuit Closer._--To remedy this very
serious defect, a cylinder of india rubber is substituted for the
leaden ball; a circuit closer so fitted is also less affected by the
action of counter mines, which is a very important advantage.

_Mathieson's Spiral Spring Circuit Closer._--A sectional elevation of
this form of circuit closer is shown at Fig. 57. It consists of a brass
base _a_, provided with a grooved flange for carrying a gutta percha
washer, and it has also an hexagonal projection for the purpose of
screwing the circuit closer into the gun-metal mouth of its air-tight
cylinder, or buoy; _b_ is a brass dome enclosing the apparatus for the
purpose of protecting it from injury, and also by means of india rubber
washers to prevent an ingress of water, should the circuit closer case
become injured, and leak; _c_ is a brass collar to which the brass
contact springs _i_, _i_ are attached, and which are regulated by the
set screws _j_, _j_; a brass spiral spring _d_ carries a metal rod _e_,
which supports a brass ball _f_, surrounded by an india rubber band
_h_. A contact disc _g_ is secured to the base of the spindle _e_, but
insulated from it by an ebonite boss; _k_ is an ebonite base plug with
two channels in it, through which the wires _m_, _m^{1}_ pass.

_An Improvement on the Inertia Circuit Closer._--This instrument is
a vast improvement on the inertia apparatus previously described,
being more simple and more certain in its action, a desideratum in
all circuit closers; but notwithstanding, up to the present time
Mathieson's inertia apparatus has been used by our government, to the
exclusion of all other instruments of a similar nature, some of which
were proved to be far superior when subjected to the crucial test of
actual practice.

_Austrian Self-acting Circuit Closer._--This form of circuit closing
apparatus, which is purely a self-acting one, that is to say, a mine so
fitted cannot be fired at will, is shown at Fig. 58.

It consists of several buffers _a_, _a_, _a_, which by means of
strong springs are held in position, their heads projecting outside
the torpedo case _b_; on being pressed in by the contact of a passing
vessel, the ends of these buffers would be forced against a ratchet
wheel _c_, which is also kept in position by means of a spring. Several
strong pieces of wood _d_, _d_ within the case keep the buffers and
their attached arms in the proper direction, and also afford rigidity
to the torpedo case. The brass ratchet wheel _c_ being put in motion
carries round with it a central arrangement _e_, the lower part of
which is shown at Fig. 58, _A_.

This portion consists of a cylinder of brass _f_ divided into two parts
insulated one from the other by a piece of ebonite _g_; on one side of
this cylinder there are three arms of brass, _h_, _i_, and _k_, and on
the other there are two arms, _l_ and _m_, all of which are insulated
from each other.

[Illustration: AUSTRIAN CIRCUIT CLOSER, MERCURY CIRCUIT CLOSER.

PLATE XIV]

The arm _h_ is close to, but insulated from a metal plate _n_, which
latter is permanently connected with the conducting wire leading from
the firing battery, and thus while in a state of rest is electrically
charged; beyond the arm _i_ is a spring _o_, which is connected with
the earth, and in such a position that when the central portion is
moved round, this spring _o_ comes in contact with the arm _i_, and
the plate _n_ with the arm _h_ simultaneously, and the circuit is thus
completed through earth to the battery, but the current of electricity
does not pass through the fuze. The arms _k_, _l_ on the opposite
sides of the cylinder, and consequently insulated one from the
other, are connected with the fuze, and the arm _m_ is connected with
the earth.

On a further pressure of the vessel on the buffer, the arm _i_ is
pushed beyond the spring, and in contact therewith, and consequently
the circuit by earth to the battery is broken, while the contact of the
arm _h_ and plate _n_ is still retained, and the current is passed by
the arm _k_ through the fuze to the arm _l_, and then to earth through
the arm _m_, thus completing the electric circuit of the firing battery
through the fuze, and to exploding the mine.

The spring acts as a circuit breaker, and by means of an intensity
coil in connection with the firing battery, the current is only passed
through the fuze when at the point of greatest intensity.

By detaching the firing battery, the channel defended by such submarine
mines may be rendered safe.

_Fuze only in Circuit at Moment of Firing it._--One of the principal
objects to be gained by the employment of such an arrangement for the
closing of the electric circuit in connection with submarine mines, is
the prevention of premature explosion from induction which might be
caused by the proximity of any atmospheric electricity, the fuze in
this system being entirely cut out of circuit until the moment when it
is necessary to fire it.

The Austrians employed this form of circuit closing instrument during
the war of 1866, and still continue to use it in connection with their
coast defence by submarine mines.

_McEvoy's Mercury Circuit Closer._--At Fig. 59 is represented a
longitudinal section of a circuit closer of this construction.

It is placed in the mine in such a manner that when undisturbed it
maintains an approximately upright position.

It consists of a metal tube _a_ into which the cup _b_ of vulcanite,
or other insulating material is fixed. The cup is contracted at some
distance from the top by the perforated plug _c_, which is also of
insulating material; _d_ is a metal pin fixed into the bottom of the
cup _b_, it is connected with the wire _e_, which is insulated and
passes to the battery; _f_ is a metal plug closing the tube _a_ and the
cup _b_ at the top; _g_ is a wire attached to the plug _f_, and passing
from it to an earth connection. The cup _b_ is filled with mercury up
to the level of the plug _c_. By the contact of a passing vessel the
instrument would be tilted sufficiently to cause the mercury to flow
into contact with the metal plug _f_, thus completing the electric
circuit and exploding the mine.

This form of circuit closer, though not generally adopted, would, on
account of its being less liable to derangement by the motion of the
waves, or by the explosion of an adjacent or counter mine, seem to
fulfil the many requirements of a circuit closer for general service.

_McEvoy's Weight Magneto Circuit Closer._--This form of circuit closer,
which is shown in section and plan at Figs. 60 and 61, is one of
the most important improvements that has ever been effected in such
apparatus, and bids fair to become universally adopted.

A heavy metal conical shaped weight _a_ (Fig. 60), hollowed out in
its base and working in a ball and socket joint _b_, rests on a solid
brass base _c_, and is so arranged that on the apparatus being struck,
the weight _a_ will fall over, pivoting on one of its supports _d_,
_d_; _e_ is a band of india rubber, encircling the weight _a_, for the
purpose of preventing a jar on its falling against the sides of the
brass cylinder _f_, which contains the weight _a_ and joint _b_. A
brass rod _g_, connected to the ball and socket joint, passes through
the base _c_, through a strong spiral spring _h_ (which latter rests on
an adjusting screw _k_), through a piece of ebonite _l_, which supports
the bobbins and core _m_, _m_^{1}; then between these bobbins _m_,
_m_^{1} through an armature _n_, which is pivoted at _p_; and lastly
through a slight spiral spring _o_, which is kept in position by the
adjusting screw _i_.

The armature _n_ is fitted with a small piece of brass _r_, so arranged
that when it (the armature) is in the position shown in Fig. 60, this
piece of brass _r_ does not make contact with the two strips of metal,
_s_, _s_, between which it, _r_, works; but when the armature _n_ is in
contact with the cores of the bobbins _m_, _m_^{1}, then the piece of
brass _r_ makes contact with the metal strips _s_ _s_, and so makes a
short circuit for the electric current. An ordinary telephone _t_, Fig.
61, in which some small shot, bells, &c., are placed, is fixed to the
top of the brass cylinder _f_.

_Action of Circuit Closer._--The action of this apparatus is as
follows:--

On the mine carrying this form of circuit closer being struck by a
passing vessel, the weight _a_ is caused to fall over towards the side
of the brass cylinder _f_, thus allowing the strong spiral spring _h_
to act on the brass rod _g_ in an upward direction, by which means the
armature _n_ is brought into contact with the soft iron cores of the
bobbins _m_, _m_^{1}.

[Illustration: M^{c.}EVOY'S MAGNETO ELECTRO CIRCUIT CLOSER.

PLATE XV]

The connections of the wires are made as follows:--

The line wire _w_ is led through the base of the apparatus and
connected to a piece of brass under the ebonite support _l_, in
connection with one of the wires of the bobbin _m_, the other wire
of which is attached to the metal strip _s_; the wires of the bobbin
_m_^{1} are connected, the one to the metal strip _s__{1}, the other
to a piece of brass under the ebonite support _l_; from this latter
piece of brass a wire _w__{1} is led to the brass screw _x_. The wires
_w__{2}, _w__{3}, from the fuzes are led, the one to the brass screw
_x_, the other to a screw _y_, which forms through the metal of the
apparatus the earth plate. One of the wires of the telephone _t_ is
connected to the brass screw _x_, the other _w__{4} is connected to
the piece of brass to which the line wire _w_ is also attached. While
the circuit closer remains in a state of rest, the current from the
signalling battery flows along the line wire _w_, up the telephone wire
_w__{4}, through the telephone which has a high resistance, then by the
wire _w__{2} through the fuzes, and to earth by the wire _w__{3}.

On the circuit closer being struck, by which cause the armature _n_ is
brought up to the cores of the bobbins _m_, _m_^{1}, and the piece of
brass _r_ in contact with the metal strips _s_, _s__{1}, the signalling
current, instead of circulating through the high resistance of the
telephone _t_, passes round the bobbin _m_, down the metal strip _s_,
across the brass piece _r_, up the metal strip _s__{1}, round the
bobbin _m__{1} (thus forming an electro magnet of _m_, _m__{1}), and by
the wire _w_, direct through the fuzes to earth, and so explodes the
torpedo. The effect of the telephone resistance being cut out, is to
strengthen the signalling current, and enable it to work the shutter
apparatus and so throw the firing battery in circuit and explode the
mine.

The advantages of this circuit closing apparatus are:--

1.--Simplicity.

2.--Compactness.

3.--Increased certainty of action, due to the sustained
contact of the armature _n_, on the apparatus being
struck.

4.--Additional means of testing a system of electrical
submarine mines, which is afforded by the telephone:--

When this form of circuit closer is put in action by a friendly vessel
coming in contact with it, or when experiments are being made, the
signalling current must be reversed, so that no doubt may exist as to
the armature _n_ having dropped, on the apparatus coming to rest.

The telephone test indicates whether the circuit closer is in position
or not, the shot, &c., within the telephone being shaken about by the
movement of the buoyant circuit closer, the noise so created is readily
distinguished by the receiving telephone at the station.

Another form of submarine mine is that known as the "Electro
Mechanical" mine. The difference between this form and an ordinary
mechanical mine is, that the exploding agent is electricity, and that
it may be converted into an electro contact mine if desirable.

_Description of a Russian Electro._--The electro mechanical mine,
used by the Russians during the late Turco-Russian war, is shown in
elevation and section at Figs. 62 and 63.

_Mechanical Submarine Mine, used by them during the late Turco-Russian
War._--_A_ is the conical shaped case; _B_ the loading hole; _C_ the
base plug; _D_, _D_, &c., are five horns, screwed into the head of the
case _A_; these are composed of a glass tube _A_, containing a chlorate
of potash mixture, enclosed in a lead tube _B_, over which is screwed a
brass safety cylinder _C_; when ready for action this latter tube _C_
is removed; directly beneath each of the horns _A_, on the inside of
the case, as at _E_, is a thin brass cylinder, closed at one end by a
piece of wood _d_, and containing several pieces of zinc and carbon,
arranged in the form of a battery, the zinc and carbon wires _z_ and
_x_ being led through the piece of wood _d_; _F_ is a copper cylinder
containing the priming charge of gun-cotton _g_, and detonating fuse
_f_; the terminals of the fuze are connected to two insulated wires,
_w_ and _w__{1}, the former of which is led direct to the loading hole
_B_, and attached on the inside to the five zinc connecting wires _z_,
&c.; the latter is attached to one end of a safety arrangement _S_, the
other end of which is connected to the wire _w__{2}, which is attached
on the inside to the carbon wires _x_, &c.; the safety arrangement _S_
consists of an ebonite cylinder, containing a brass spiral spring fixed
to one end of it, and pressing against a brass plate at the other,
thus preserving a metallic connection between the wires _w__{1}, and
_w__{2}; the mine is rendered inactive by pressing the spring down, and
inserting a piece of ebonite between it and the plate.

_Its Action._--The action of this form of electro mechanical submarine
mine is very simple; the brass safety cylinders _c_, _c_, &c., being
removed on a vessel striking either of the horns, _D_, _D_, &c., the
lead tube _b_ is bent, causing the glass tube _a_ to be broken, and
the mixture contained therein to flow into the cylinder _E_, instantly
generating a current of electricity in the zinc carbon battery, and
exploding the mine.

_Mode of Converting into an Electro Contact or Observation Mine._--To
convert this mine into an electro contact one, it is only necessary to
connect the wires _w__{1} and _w__{2} to other wires leading from the
shore; also by replacing the horns _D_, _D_ by solid brass screw plugs,
the mine may be converted into an ordinary observation one. In this
case the two wires _w_ and _w__{1} attached to the fuze _f_, terminals
would have to be connected to the observation instruments on shore.

_Turkish Vessel sunk._--It was by means of one of these electro
mechanical mines, that the Turkish gunboat _Suna_ was sunk at Soulina.

Firing by observation, that is to say, effecting the ignition of an
electrical submarine mine at the precise moment of a hostile vessel
being vertically over it, through the agency of one or two observers
stationed at a very considerable distance from the mine, should, with
the very perfect self-acting circuit closers that exist at the present
time, be resorted to only in very exceptional cases, or in connection
with the self-acting system.

There are two defects, which are common to all methods of firing
submarine mines by observation, and these are:--

1.--At night time, or in foggy weather, it cannot be
employed.

2.--It is necessary to employ at least two observers,
at a considerable distance apart, who to effect a
proper action at the right moment, must work in perfect
unison. These defects alone are sufficient to explain
the preference given to a self-acting method of closing
the electric circuit at the precise moment of a vessel
being in position over a mine by those governments who
have adopted electrical submarine mines as a means of
coast defence.

_Methods of Firing by Observation._--There are several methods of
firing by observation, of which the following are the ones principally
used:--

1.--By pickets or range stakes.
2.--By cross bearings.
3.--By intersectional arcs fitted with telescopes.
4.--The Prussian system.

_Intersection by Pickets or Range Stakes._--In narrow channels and at
short distances, this system of ascertaining the relative position
of a hostile vessel and a submarine mine may be used, provided that
skilled and careful men are employed to work it. Two or more pickets
or stakes are arranged in front of the firing station in such a manner
that a vessel passing up the channel on the prolongation of these
stakes will be over a mine. This arrangement should of course always be
considered as an extempore one; it was used on several occasions by the
Confederates during the American civil war.

_Firing by Cross Bearings._--The simplest method of so determining
the relative position of a vessel and a submarine mine, and exploding
it at the right moment, is that in which observers are placed on
the prolongation of the mines. This mode is shown at Fig. 64, where
_m__{1}, _m__{2}, _m__{3}, &c., and _n__{1}, _n__{2}, _n__{3}, &c.,
are the mines; _A_ and _B_, the points in prolongation of the mines
where the observers are stationed; _D_ the firing battery, and _s_, and
_s__{1} two hostile vessels.

At the stations _A_ and _B_ firing keys are placed, at the former one
for each separate mine, perfectly distinct and insulated from each
other, at the latter a single key. The pivot points of the series of
keys at _A_ are connected by separate wires to one pole of the firing
battery _D_, the other pole of which is connected by a single cored
insulated cable to the pivot point of the key at _B_; the contact
points of the series of keys at _A_ are connected by separate line
wires as _A m__{1}, _A m__{2}, _A m__{3}, &c., to the different mines,
while the contact point of the key at _B_ is put to earth. Thus it will
be seen that, in the case of the row of mines, _m__{1}, _m__{2}, &c.,
unless the key at _B_, and the key at _A_, of either of those mines
are both pressed down at the same instant, no current can pass, and
therefore none of those mines can be exploded.

[Illustration: RUSSIAN SUBMARINE MINE, FIRING BY OBSERVATION.

PLATE XVI]

In the case of the vessel _S_, though at _C_, she is on the
prolongation of the line _A m__{5}, _C_, and therefore the key of the
mine _m__{5}, is pressed down at _A_, yet not being on the prolongation
of the line _B_, _E_, the key at _B_ is not pressed down, therefore the
firing battery is not thrown in circuit, or the mine _m__{5} exploded,
but when the vessel _s_ reaches the position _N_, that is over the mine
_m__{3}, she being on the prolongation of the lines _A m__{3}, and _B
E_, the key (_m__{3}) at _A_, and the key at _B_ would both be pressed
down, and therefore the mine _m__{3} exploded, and the ship destroyed.
In the case of a vessel passing through an interval between any two
mines at such a distance as to be out of the radius of destructive
effect of either of the mines belonging to the first row (which is
shown at _s__{1},) only the key at _B_ would be pressed down, and thus
the vessel enabled to pass safely through, but only to come to grief
at the second or third row of mines, provided they have been properly
placed, and separate though similar arrangements as in the case of the
line of mines, _m__{1}, _m__{2}, &c. have been made.

_Firing by a Preconcerted Signal._--At Fig. 65 is represented a
somewhat similar, though a much simpler plan of the foregoing system,
by employing a preconcerted signal at the station _B_ in the place of
the firing key and insulated cable, as in the former case. The only
material difference in the arrangement of these two methods, is that
in the latter case the pole of the firing battery at _A_, which in
the former case was connected to the firing key at _B_, is put direct
to earth. As will be readily understood, this latter system requires
great coolness and nerve on the part of the operator at _A_, who has
not only to watch the vessel passing across his intersections, but
also to be on the alert to receive the signal from the observer at
_B_. Should it ever be necessary to adopt this latter system, it will
be found advisable to employ two men at station _A_, one to watch
station _B_, the other to attend to the firing key and intersections.
A separate signal-flag for each line of mines, and also a separate
firing arrangement, would be required. As in many cases it would not
be practicable to have a station in such an advanced position as at
_B_, in Figs. 64 and 65, on account of the danger of its being cut off
by an enemy, another combination becomes necessary. In this instance
the station _B_ is placed on the opposite side of the river, &c.,
to that on which the station _A_ is placed, and a series of firing
keys, instead of a single one, is here used, necessitating a multiple
cable between the stations _A_ and _B_, in the place of single cored
cable; the manner of manipulating this method is very similar to that
previously described.

_Firing by Intersectional Arcs fitted with Telescopes._--The
foregoing methods of firing by cross bearings are replete with
many serious defects, to remedy which, to a considerable extent,
special arrangements have been devised, that is, the employment of
intersectional arcs fitted with telescopes at the stations _A_ and _B_.

Figs. 66 and 67 show the arrangements of these arcs, the former being
the one used at the firing station _A_, the latter at the converging
station _B_. At each station one arc is provided for each row of mines
placed in position. The firing arc Fig. 66 consists of a cast iron
frame _a_, with three feet _b_, _b_, _b_, these being provided with
levelling screws.

To ascertain when this frame is level, a circular spirit level is
attached thereto, a telescope _d_ provided with one horizontal and
three vertical cross wires, supported on Y's, admitting of vertical
motion and attached to an upright _e_. A mill-headed screw _f_ enables
the telescope _d_ to be raised or lowered; the telescope, which is
rigidly connected to a vernier _g_, traversing over a graduated arc
_h_, can be moved rapidly in a lateral direction by means of a rack
and pinion arrangement _i_, and it can be clamped in any position by
means of the screw _h_. Sights are fixed on the telescope in a vertical
plane passing through its axis. To the outer rim of the frame of the
arc, which is smooth, are secured the sights _l l_ (shown on a large
scale at Fig. 68), to give the direction of the mines. These sights are
provided each with a brass point of V form, _m_, and a binding screw,
_n_, in metallic connection with each other, but insulated by means of
an ebonite plate from the rest of the metal of the sight. One end of a
short piece of insulated wire is attached to the binding screw _n_, and
the other passes through a hole in the base of the sight and projects
below it; _o_ is a brass tube rigidly connected to and moving with the
upright carrying the telescope _d_, and projecting in front of this
latter. A brass spring _p_ (see Fig. 69) is attached to, but insulated
from the outer extremity of this tube, and is so arranged as to make
contact with the V point _m_ on the sight, by means of a corresponding
projection fitted to its under side. An insulated wire passing the tube
_o_, the outer end of which is connected to a screw on the spring _p_,
forms a metallic connection between this projection and the firing key.

At Fig. 68 is shown an enlarged view of the front of the sight; in
addition to the V projection _m_, and binding screw _n_, it is fitted
with a capstan-headed screw to bear against the inner rim of the frame,
and a thin wire upright _t_ for giving the alignment of the mine, to
which a disc is attached, on which the number of the mine is affixed.

When the distance between the station and the mine is only about one
mile, an ordinary eyepiece is used in the place of the telescope _d_.

At Fig. 67 is represented the arc employed at the converging station,
which with the exception of there being no tube _o_, and only one
sight, is precisely similar in construction to the one used at the
firing station, and which has been described.

[Illustration: APPARATUS FOR FIRING BY OBSERVATION.

PLATE XVII]

_Application of the Intersectional Arc Method._--The application of the
method of firing by observation, by means of intersectional arcs fitted
with telescopes, is shown at Fig. 70. _C_, _D_, and _E_ are three of
the larger kind of arcs, one being used for each row of mines at the
firing station _A_. At the converging station _B_, one of the smaller
arcs is used for each row of mines, as shown at _F_, _G_, and _H_.
_S_, _S__{1}, _S__{2}, are the signalling apparatus, the _F_ terminals
of which are connected to the sights _l_, _l_, _l_, Fig. 69, of arcs
_C_, _D_, _E_. Firing keys _a_, _a_, _a_ at station _A_ are connected
to each arc, and to three of the cores of the cable connecting the two
stations _A_ and _B_, respectively. At the converging station _B_,
three firing keys _b_, _b_, _b_ are connected to earth and to three
cores of the connecting cable respectively. The remaining core of this
cable is connected to the recording instruments _d_, _e_. The action of
the arcs, &c., will be readily understood from the diagram at Fig. 70.

This arrangement does not interfere with the action of the circuit
closer, as all that is effected by the observing arc circuit is to put
the signalling battery current at the converging station _B_ to earth
instead of at the circuit closer.

_Prussian System of Firing by Observation._--The principle on which
this system is based, depends upon the proposition that if _c d_, in
the triangle shown in Fig. 71, be always kept parallel to _H B_, then
_A c_, _c d_, _d A_ bear exactly the same proportion to each other as
_A B_, _B H_, _H A_ do to one another; so that by means of the small
triangle _A d c_, the lengths of the sides of the large triangle _A
B H_ can be obtained, and hence the position of the point _H_, the
base _A B_ being of course known. In Fig. 71 at _A_ there is a slate
table representing the roadstead, and upon it the exact position of
every torpedo is laid down, corresponding to their position in the
roadstead. At _A_ and _B_, 500 yards apart, telescopes having cross
wires are placed; at _A_ a long narrow straight-edged strip of glass
_A d_ is arranged to move in unison with the telescope at _A_; and by
the application of dynamo electricity, a similarly constructed piece of
glass _c d_ moves in exact unison with the telescope at _B_, and having
its pivot at _C_; that is to say, _C d_ keeps parallel with _B H_, the
line of sight of the observer at _B_.

Then if the observers at _A_ and _B_ have got a ship in their
telescopes, the point of intersection _d_ of the two pieces of glass _A
d_ and _C d_ gives the position of the ship on the slate table at _A_,
and when this point _d_ comes over the position of any one mine on the
slate, it is known that the ship is over that particular mine in the
harbour, and she may be destroyed accordingly, by throwing the firing
battery into circuit.

By the employment of electricity and a mirror, the great defect of this
method, viz., the necessity of employing four people to manipulate it,
would be remedied. The foregoing is a modification of Siemens's method
of ascertaining distances at sea, &c.

_Rules observed in Planting Mines._--In placing a system of submarine
mines in position, the following are some of the chief points to
be attended to, this work depending in a great measure on local
circumstances, and on the method that is to be adopted in exploding and
mooring them:--

1.--The plan of defence must be carefully laid down
on a chart, on a scale of not less than six inches
to the mile, and on this plan are to be marked the
sites of the observing stations, the positions of each
mine, circuit closer, and junction box, with their
corresponding numbers, and also of the electric cables.

2.--The position of each mine having been determined,
should be marked off by buoys.

3.--The utmost care should be taken to lay the electric
cables, so that they shall be as far as possible away
from the mines in the vicinity of which it may be
necessary to take them, so as to lessen the liability
of injury to them, by the explosion of the latter.

4.--The electric cables should be laid parallel, and
never be allowed to cross directly over each other,
otherwise the operation of underrunning them will be
much complicated, also a certain amount of slack should
be allowed to facilitate in picking the cables up for
repair, &c.

5.--Every manner of device is to be used to conceal the
electric cables, such as laying dummies, making detours
inland, &c.

6.--All marks indicating position of the mines to be
removed, after the mines have been placed in position.

7.--The identity of each cable and mine to be very
carefully preserved throughout, by means of a number.

8.--A number of electro contact mines should be
placed in advance of the leading line of mines, at
irregular intervals, to prevent the enemy, having once
ascertained the position of one mine of a line, from
knowing within limits the position of the others of
that line.

[Illustration: SYSTEMS OF DEFENCE BY SUBMARINE MINES.

PLATE XVIII]

In connection with a system of defence by electrical submarine mines,
the following batteries are required:--

1.--Firing battery.
2.--Signalling, or shutter battery.
3.--Testing battery.
4.--Telegraph battery.

_Firing Battery._--The firing battery should be suited to the nature of
the fuze employed, and should possess considerable excess of power to
enable it to overcome accidental defects, such as increased resistance
in the various connections, or defective insulation in the line wire,
&c.

As platinum wire or low tension fuzes are now universally adopted as
the mode of ignition for submarine mines, it will be only necessary
to describe those electrical batteries which are most suitable as an
exploding agent in connection with such fuzes; these are as follows:--

1.--Siemens's dynamo low tension machine.
2.--Von Ebner's Voltaic battery.
3.--Chromic acid or Bichromate Voltaic battery.
4.--Leclanché's Voltaic battery.

_Siemens's Low Tension Dynamo Electrical Machine._--This instrument
consists of an electro magnet and an ordinary Siemens armature, which,
by the turning of a handle, is caused to revolve between the poles of
the electro magnet. The coils of the electro magnet are in circuit with
the wire of the revolving armature, and during rotation the residual
magnetism of the soft iron electro magnet cores at first excites weak
currents which pass into the electro magnet coils, increasing the
magnetism of the core, thus inducing still stronger currents in the
armature wire. This accumulation by mutual action goes on until the
limit of magnetic saturation of the iron cores of the electro magnets
is reached.

By the automatic action of the machine, the powerful current so
produced is sent into the leading wire or cable to the fuze to be
exploded.

In this apparatus the electric current passes continuously through the
line wire until a sufficiently powerful current is generated to heat or
fuze the bridge of the fuze, and so ignite the gun-cotton priming. The
coils of the armature and electro magnets are wound with wire of large
diameter, to a total resistance of 8 to 10 Siemens units, or 7·6 to 9·5
ohms, in about 2,000 windings.

With a platinum wire weighing 1·65 grains per yard, 6-1/2 inches can be
fuzed on short circuit, and 14 inches can be heated to redness.

The total weight of this machine, which is manufactured by Messrs.
Siemens Brothers, is about 60 lbs.

_Advantages of Siemens's Dynamo Electrical Machine._--The advantages of
such a machine over Voltaic apparatus are:--

1.--The absence of chemical agents.

2.--There is less liability to get out of order.

3.--No special knowledge is required to work them, or
to keep them in order.

4.--Greater durability.

The great defect of this and all similar machines is that the electric
force has to be developed by turning a handle for a certain time
before it is possible to generate a current sufficiently powerful to
ignite a fuze, which defect, in connection with a system of defence
by self-acting submarine mines, particularly at night, renders them
inferior to Voltaic batteries, as under such circumstances, an
apparatus is required that will cause an electric current to flow at
any moment when the circuit is completed.

The application of steam power would to a certain extent remedy the
above-mentioned defect, but the cost of such a method, compared to
that of a Voltaic arrangement, would be far too great to allow of its
superseding the latter arrangement.

_Von Ebner's Voltaic Battery._--This form of Voltaic battery, which
may be considered as a modification of that known as Smee's, was
designed by Baron von Ebner, colonel of the Austrian imperial corps of
engineers, for use in connection with the Austrian system of submarine
defence, by self-acting electrical mines.

A section of one of these cells is shown at Fig. 72. It consists of a
glass vessel _a_, to contain the diluted sulphuric acid, within which
is suspended a plate _b_ of platinised lead, which is bent round into
a cylindrical form to fit close around the inner surface of the glass
vessel. In the centre of this latter is hung a porcelain perforated
cup _c_, containing some cut-up zinc and mercury to keep it (the zinc)
amalgamated. The top of each cell is furnished with a porcelain cover,
through which the wires attached to the positive and negative poles of
the cell project.

Due to the large quantity of liquid contained in the cell, the
tendency to alter its internal resistance is retarded; also by the
arrangement of the porcelain cup, above detailed, the consumption
of zinc and mercury, which in an ordinary Voltaic battery is very
considerable, is materially diminished.

_Chromic Acid or Bichromate Battery._--This form of battery is very
similar to Grove's, the difference being that, in the place of the
nitric acid as the exciting liquid, either chromic acid, or a solution
of bichromate of potash, sulphuric acid and water is substituted.

A form of this battery, as designed by Dr. Hertz, is used in connection
with the German system of torpedo defence.

_Leclanché Voltaic Battery._--This form of Voltaic battery was invented
by M. Leclanché, some twelve years ago. At Fig. 73 is shown a cell of
this battery in its original form. The positive pole _a_ consists of a
plate of graphite in a porous pot _b_, and surrounded by a mixture of
peroxide of manganese and graphite. The negative pole _c_ is a rod or
pencil of amalgamated zinc. The whole is enclosed in an outer vessel of
glass _d_ containing a solution of sal ammoniac.

A modified form of the Leclanché cell as used in a firing battery is
shown at Fig. 74. It consists of an ebonite trough or outer vessel _a_
about 16" long, 9" deep, and 2-3/4" wide. The negative pole or zinc
plate _b_ is of similar shape to the trough _a_, but with its base
removed, and does not fit the trough exactly, the space between it and
the trough being left to ensure the former being completely surrounded
by the sal ammoniac solution; the positive pole, or carbon element,
consists of four gas carbon plates _c_ attached together at their head
by means of lead, and enclosed in a flannel bag, in which they are
firmly embedded in the peroxide of manganese mixture; the positive
element is of such a shape that it fits loosely between the sides, and
is nearly of the same height as the zinc plate.

The object of such a form of cell was to obtain an electric current of
large _quantity_, with as few cells as possible, by which means the
loss of power which might occur from the employment of a great number
of small cells is avoided.

_Advantages of a Leclanché Firing Battery._--The advantages of the
Leclanché firing battery are:--

1.--The absence of chemical action when the battery
circuit is not complete, and consequently there is no
waste of material.

2.--Requires little or no looking after.

3.--It may be kept ready for action in store without in
any way deteriorating.

4.--It is comparatively very cheap.

These advantages combine to make a Leclanché battery the most suitable
of any other form of electrical battery for use as the exploding agent
for electrical submarine mines, and it is now universally used for such
purposes.

_Signalling Battery._--The signalling battery should be so constituted
as to be capable of working the electro magnet of the shutter apparatus
effectually when the circuit is closed direct to earth, and yet not so
powerful as by the continuous passage of the current generated by it to
fire the fuze in the mine. In the case of a platinum wire fuze being
in the circuit, plenty of power may be given to the battery without
fear of a premature explosion from this cause, but in the case of a
high tension fuze it is necessary to be very careful in order to guard
against such a contingency.

As in the case of a signalling or shutter battery, the electric current
will be continually flowing, it is necessary to employ a constant
battery, or one that requires least trouble and expense to maintain it
in working order, and it is for this reason that a modified form of
Daniell battery has been adopted to work the shutter apparatus.

_Daniell Signalling Battery._--At Fig. 75 is shown the manner of
arranging a Daniell cell. A glass or porcelain vessel _a_ contains a
saturated solution of sulphate of copper, in which is immersed a copper
cylinder _b_ open at both ends and perforated by holes; at the upper
part of this cylinder there is an annular shelf _d_, also perforated
by holes, and below the level of the liquid; this is for the purpose
of supporting crystals of sulphate of copper for the replacing of that
decomposed as the electrical action proceeds. Inside the cylinder _b_
is a thin porous vessel _c_ of unglazed earthenware; this contains
either water, or a solution of common salt, or dilute sulphuric acid,
in which is placed the cylinder of amalgamated zinc _e_. Two strips of
copper _p_ and _n_, fixed by binding screws to the copper and to the
zinc, serve for connecting the elements in series, or otherwise.

For the purposes of testing, either the Leclanché or Daniell battery
specially arranged, or the Menotti battery, which is really a
modification of the Daniell, may be used.

[Illustration: FIRING BATTERIES, TESTING BATTERIES.

PLATE XIX]

_Description of a Menotti Cell._--A Menotti cell, shown at Fig. 76,
consists of a copper cup containing some crystals of sulphate of copper
and covered with a fearnought diaphragm _a_, placed at the bottom of
an ebonite cell _b_; over this cup is put some sawdust, and resting on
top of this is a disc of zinc _c_ on another piece of fearnought. The
upper portion of the zinc and its connection with the insulated wire
are carefully insulated. Fresh water poured on the sawdust renders the
battery active.

_Description of a Menotti Test Battery._--Fig. 77 represents a plan
of the top of such a test battery with a 20-ohm galvanometer attached
thereto. The connections are made as follows:--

One of the wires _w_ of the object to be tested is attached to the
terminal _f_, which is also connected by an insulated wire to the
copper cup _a_; the other main wire _w__{1} is attached to the terminal
_g_ of the galvanometer; _h_, the other terminal of the galvanometer,
is connected by a short piece of wire _k_ to the terminal _l_ of the
contact key _m_; and the contact point _n_ is in connection with the
zinc plate _c_; thus the current from the battery flows along the wire
_w_ through the object to be tested, back along the wire _w__{1},
through the coils of the galvanometer, along the wire _k_ to the
contact key _m_, and if this is pressed down to the zinc plate _c_, so
completing the circuit.

To steady the needle of the galvanometer a bar magnet is used, which is
inserted in the space _r_. The whole of the apparatus is enclosed in a
leathern case fitted with a cover and strap.

This is a very compact and simple form of test battery, and will be
found extremely useful in boats, &c., when placing mines in position.

_Telegraph Battery._--For the purposes of telegraphing between torpedo
stations, &c., a form of Leclanché battery, known as No. 3 commercial
pattern, is generally used.

_Voltaic Batteries._--The following points in connection with the
use of voltaic batteries, which are taken from Beechey's 'Electro
Telegraphy,' should be carefully observed:--

1.--Each cell of a battery should be carefully
insulated.

2.--The floors and tables in the battery room should be
kept scrupulously clean and dry, so as to prevent the
least leakage or escape of the current.

3.--The plates of a battery should be clean.

4.--Porous cells should be examined, and cracked ones
replaced.

5.--No sulphate of zinc or dirt should be allowed to
collect at the lips of the cells.

In the case of a Daniell battery--

1.--The solutions should be inspected daily, and
crystals of sulphate of copper added as required.

2.--The zinc plate must not touch the porous cell, or
copper will be deposited on it (the zinc).

3.--The battery should be charged with sulphate of zinc
from the first.

4.--The copper solution must be watched and prevented
from rising over the edge of the porous jar, the
tendency of such solutions being to mix with each other
by an action termed _osmosis_.

These being in addition to foregoing general directions for Voltaic
batteries.

_Defects in a Voltaic Battery on its Current becoming Deficient._--On
the electric current of a Voltaic battery becoming deficient, the
following defects should be looked for:--

1.--Solutions exhausted; for instance, sulphate of
copper in a Daniell's entirely or nearly gone, leaving
a colourless solution.

2.--Terminals or connections between the cells
corroded, so that instead of metallic contact there are
oxides of almost insulating resistance intervening in
the circuit.

3.--Cells empty, or nearly so.

4.--Filaments of deposited metals stretching from
electrode (pole) to electrode (pole).

Also intermittent currents are sometimes produced by loose wires or
a broken electrode, which alternately makes and breaks contact when
shaken. Inconstant currents are also sometimes produced when batteries
are shaken. The motion shakes the gases off the electrodes, thus
increasing temporarily the electro-motive force of the battery.

_Firing Keys and Shutter Apparatus._--The following is a description of
the various firing keys and shutter signalling apparatus, which is used
in connection with a system of electrical submarine mines. By means of
the former the firing or other batteries may be thrown into circuit
at will, whilst by means of the latter the firing battery is thrown
in circuit without the aid of an operator, and a signal at the same
instant given, indicating that a certain mine of the system has been
struck.

_Description of a Series of Firing Keys._--At Fig. 78 is shown a plan
and section of a series of firing keys as arranged for firing several
mines by observation.

It consists of a strong wooden frame _a_, of a convenient form for
the purpose of attaching it to the firing table by screws through the
holes _b_, _b_. On this frame a series of keys _c_, _c_, _c_ are fixed
at convenient intervals. These consist of a strong brass spring firmly
screwed to a series of brass plates _d_, _d_, _d_ on the front of the
wooden box _a_. From these latter short copper wires pass through the
woodwork, and of such a length that, when required, the mine wires may
be easily attached by means of binding screws, as shown at _f_. The
inner end of each key is fitted with an ebonite knob (which is shown
at _c_ in the section) to insulate the hand of the operator when using
the key. On the frame, and directly under each of the ebonite knobs,
are arranged a series of metallic points _g_, _g_, _g_, so placed that
on either of the keys _c_ being pressed down, a perfect contact is made
between it and its respective metallic point; _h_, _h_, _h_ are copper
wires leading from the metallic points _g_, _g_, _g_ through the box,
and of such a length that binding screws _f_, _f_, _f_ can be easily
attached to them when necessary.

A single firing key of an improved form is shown at Fig. 79. It
consists of a strong wooden box _a a_, weighted at the bottom with
lead in order to steady the key on the table, &c., on which it may be
placed; on the inside of the bottom of the box is fixed a piece of
ebonite, by which means the metallic point _b_, and the terminal of the
firing key _c_, are insulated from each other; _d d'_ are two terminals
at the end of the box, to which the circuit wires are attached, one
of these terminals is connected in metallic circuit to the firing key
at _c_, the other one to the metallic point _b_; a wooden cover _h_,
fitted with a catch _k_, protects the connections of the wires; by
means of a plate, and catch _e e_, the key can be rendered inactive,
thus preventing the danger of a premature closing of the electric
circuit; by means of a spring _s_ a break is always established between
the key and the metallic point. It is immaterial to which of the two
terminals _d d'_ either wire is connected.

_The Morse Firing Key._--This form of key is so well known in
connection with the Morse telegraph, that it is not necessary to
describe it.

It is usually employed in torpedo work in connection with a testing and
firing table.

_The Shutter Apparatus._--The shutter signalling and firing apparatus
was devised to enable the firing battery current to be thrown in
circuit without the aid of a personal operator, the signalling current
(which is always kept in circuit) at the same instant ringing a bell,
by which is known the particular mine that has been struck.

At Fig. 80 is represented a diagram of such an apparatus. _a_ is an
armature working on a pivot between the two horns of an electro magnet
_b b_, and held in position by a spiral spring _c_; the latter is in
connection with a regulating screw, by which more or less pressure may
be brought to bear in an opposite direction to that of the attractive
action of the electro magnet. A stud _i_ regulates the distance to
which the armature may be drawn back; _d_ is a shutter on which a
reference number for each mine should be indicated, attached to a
lever pivoted at the point _e_, the inner arm of which is just long
enough to catch under the point of the armature _a_; when a current of
sufficient strength is passed through the coils _b b_ of the electro
magnet, the armature _a_ is attracted, releasing the lever attached
to the shutter _d_, which by its own weight falls into the position
shown by the dotted lines. _f_ and _g_ are two mercury cups, the former
being in connection with the signalling current, and the latter with
the firing current. When the lever is horizontal and the shutter drawn
up and ready for action, the circuit of the signalling battery _s_ is
completed through the mercury cup _f_, along an arm _h_ of the lever
to the pivot _e_, and thence to the mine by the line wire _w_. When
the circuit closer is struck by a passing vessel, and consequently the
shutter thrown into the position shown by the dotted lines, another
arm _k_, a prolongation of the lever, falls into the mercury cup _g_,
which latter is in connection with the firing battery _F_. The armature
_a_ is prevented from coming into actual contact with the horns of the
electro magnet by two small studs. The object of this is to prevent any
effect of residual magnetism which might otherwise interfere with the
rapidity of action of the armature when released and drawn back by the
spring _c_.

[Illustration: FIRING KEYS, SHUTTER APPARATUS.

PLATE XX]

_The object of employing Mercury Cups._--Mercury cups were devised in
the place of the springs used in connection with the original design of
a shutter apparatus, for the reason that electrical circuits dependent
on the pressure of springs are always liable to interruption from dirt
or oxide intervening between the points of contact.

_Shutter Apparatus used with a Circuit Breaker._--When the circuit
breaking system is used with the shutter signalling apparatus, the
action of the armature in releasing the lever must be reversed; that is
to say, that when the current is passing and the armature _a_ attracted
to the electro magnet _b b_, the shutter _d_ must be held up, and when
the current ceases, and the armature _a_ drawn back by the spring _c_,
the lever must be released, and the shutter allowed to fall. This is
effected by altering the end of the lever, so that it hooks into,
instead of abutting against the armature _a_.

To each shutter apparatus an electric bell is fitted, by which notice
is given when a circuit closer has been struck. For general service, a
box containing seven such shutter signalling and firing apparatus has
been adopted, a plan of which is represented at Figs. 81, 82 and 83.
The connections of the different circuits are as follows:--

The insulated wire of the upper bobbin of the electro magnet is
connected to the spring of the armature; the pivot of the lever is
connected with the right-hand terminal _B_, or main line connection
on the top of the box; the insulated wire from the lower bobbin is
connected to the middle brass plate _k_ in the front ledge of the
apparatus, the circuit from _B_ to _k_ being thus completed. The front
adjoining brass plate _A_, provided with a terminal, is connected with
the negative pole of the signalling battery, the positive pole being
put to earth.

On a brass plug being put in the hole _l_, the signalling current will
flow to the plate _k_, thence through the lower and upper bobbin to
the spring of the armature, along the latter to the shutter lever, and
from the pivot through the main line wire to the mine. The innermost
brass plates _H H_ are all connected in the same metallic circuit, and
to them are attached by means of the binding screw _D_ the test battery
and galvanometer. Thus on the brass plug being removed from _l_, and
placed in _m_, the signalling battery is cut out of circuit, and the
test battery thrown in. In this way the condition of each individual
mine may be ascertained while the connections of the remaining mines
are left undisturbed. The positive pole of the firing battery (the
negative being to earth) is connected to the terminal _S_ at the
right-hand corner of the lower ledge of the box; the plate to which the
terminal _S_ is fixed is divided at _G_, the left-hand portion being
connected to a bar which runs horizontally the whole length of the
box, and in metallic connection with each mercury cup _g_, Fig. 80. A
brass plug is placed in the hole _G_, and when from any cause the lever
drops, the firing battery will be thrown into circuit, and the mine to
which the lever that has fallen is attached will be exploded.

_Shutter Instrument and Observing Telescope._--Each mine is given a
number, which is put on the disc of the shutter instrument connected
to it, and also on the corresponding tablet _C_. From the brass plate
in connection with the spring _c_, Fig. 80, a wire is taken to the
terminal _f_, Fig. 81, on top of the box. From this terminal a wire is
led to the connections of the observing telescope, and thus the mines
can be fired by judgment if required, without the aid of the circuit
closer.

The signal battery current is always circulating, even when the system
is in a state of rest, but in consequence of the resistance placed in
this circuit, which may be either a resistance coil in the circuit,
added to the resistance of the fuzes, when high tension fuzes are used,
or only the former resistance in the case of low tension fuzes, this
current is too feeble to form an electro magnet; directly, however,
a circuit closer is struck, this resistance is cut out, and thus the
signal battery current becomes sufficiently powerful to work the
electro magnet of that particular mine.

The circuit of the signal battery, and that to the observing telescope,
are broken the instant the lever commences to fall.

To enable the apparatus to be used on the circuit breaking system, a
spare lever _E_ is provided for that purpose with each box.

The object to be gained by a system of testing is to ascertain the
condition of the electrical submarine mines placed in the defence of
a harbour, &c., and should there exist any fault, not only to detect
its exact position and cause, but also its magnitude, so that it may
be at once determined whether it is necessary to remedy the fault, or
whether the electrical apparatus is sufficiently powerful to overcome
the defect.

_Tests._--There are two distinct kinds of tests, viz.:--

1.--Mechanical tests.
2.--Electrical tests.

[Illustration: SHUTTER APPARATUS.

PLATE XXI]

Mechanical tests are applied to ascertain that the mechanical
arrangements of the shutter apparatus, circuit closers, and all similar
appliances work efficiently and easily; that the several parts of the
mine case when put together for service are thoroughly watertight;
that the chains, wire cables, and ropes in connection with the mooring
apparatus are of sufficient strength to perform the work required of
them; that the weights of the anchors, or sinkers, are such as to keep
the mines in position after submersion; and that the case of the mine
be sufficiently strong to enable it to bear the external pressure due
to the depth at which it may be submerged for a considerable time
without any leakage.

The foregoing tests of the mine case and moorings would of course be
performed during the process of manufacture, but to prevent any chance
of failure they should be repeated before being employed on actual
service.

_Electrical Tests._--Electrical tests are those which are applied
to the several component parts of the system, to ascertain that the
electrical conditions necessary to a successful result exist.

The importance of being able to carry out the above in its entirety
is understood when it is remembered that a submarine mine becomes
practically valueless unless it acts efficiently at the single instant
of time that it would be required so to do.

_List of Instruments used in Testing._--The following are some of the
instruments that are employed in connection with a system of electrical
tests:--

1.--Thomson's electrometer.
2.--Thomson's reflecting galvanometer.
3.--Astatic galvanometer.
4.--Differential galvanometer.
5.--Detector galvanometer.
6.--Three coil galvanometer.
7.--Thermo galvanometer.
8.--Siemens's universal galvanometer.
9.--A shunt.
10.--Commutator.
11.--Rheostat.
12.--Resistance coils.
13.--Wheatstone's balance.

Electrometers indicate the presence of a statical charge of
electricity, by showing the force of attraction or repulsion between
two conducting bodies placed near together. This force depending in the
first place on the quantity of electricity with which the conducting
bodies are charged, ultimately depends on the difference of potential
between them; an electrometer is therefore strictly an instrument for
measuring difference of potential.[J]

Sir William Thomson's quadrant electrometer is the most perfect form
of electrometer yet constructed, and the one usually employed in cable
testing. It consists of a very thin flat aluminium needle spread out
into two wings, and hung by a wire from an insulated stem inside a
Leyden jar, which contains a cupful of strong sulphuric acid, the outer
surface of which forms the inner coating of the Leyden jar. A wire
stretched by a weight connects the aforesaid needle with this inner
coating. A mirror, rigidly attached to this needle by a rod, serves
to indicate the deflection of the needle by reflecting the image of
a flame on to a scale. The needle hangs inside four quadrants, which
are insulated by glass stems: each pair of opposite quadrants are in
electrical connection. Above and below the quadrants two tubes, at
the same potential as the needle, serve to screen it and the wires in
connection with it from all induction except that produced by the four
quadrants. Suppose the needle charged to a high negative potential (-),
then if the quadrants are symmetrically placed, it will deflect neither
to the right nor to the left, so long as the near quadrants are at the
same potential. If one of these be positive relatively to the other,
the end of the needle under them will be repelled from the negative
quadrant to the positive one, and at the same time the other end of the
needle will be repelled from in the opposite direction. This motion
will be indicated by the motion of the spot of light reflected by the
mirror, and the number of divisions which the spot of light traverses
on the scale measures in an arbitrary unit the difference of potential
between the + and - quadrants.

The reflecting electrometer being a very delicate instrument, requires
careful handling, and should only be used by a practised electrician.
Its use would therefore be restricted to important stations, and
special tests of a delicate nature.

_Thomson's Reflecting Galvanometer._--A galvanometer is an instrument
intended to detect the presence of a current and measure its magnitude.

The most sensitive galvanometer as yet constructed is the reflecting
galvanometer of Sir William Thomson, a diagram of which is shown at
Fig. 84.

A small piece of magnetised steel watch spring, 3/8ths of an inch long,
is fastened with shellac on the back of a little round concave mirror,
and of about the size of a fourpenny piece. This is suspended by a
piece of unspun silk thread in the centre of a coil of many hundred
turns of fine copper wire insulated with silk, and well protected
between the turns with varnish. The two ends of the coils are soldered
to terminal screws _a_, _b_, so that any conducting wire can be joined
up to it as required. The little mirror hangs in the middle of its
coil, with the magnet lying horizontally. By means of a lamp _L_ placed
behind the screen, the light of which passes through a slit _M_, and is
thrown on the face of the mirror, a spot of light is reflected on the
scale _N_.

When a current passes through the coil, the little magnet is deflected,
and since the magnet is attached to the mirror, which is very light,
both are deflected as forming one body, and the spot of light moves
accordingly along the scale _N_.

A powerful steel magnet _S_ is placed above the coil, and can be moved
up or down, whereby the directive force of the earth may be increased
or weakened. This magnet _S_ is used to steady the spot of light, which
otherwise would shake about, and there would be no certainty about
the measurement. A second magnet _T_ is placed perpendicular to the
magnetic meridian, to adjust the zero of the instrument, i.e., to bring
back the spot of light to a fiducial mark at the centre of the scale
when no current is passing.

This instrument should only be used at important stations, and when
special tests of a delicate nature are required to be applied.

_Astatic Galvanometer._--An astatic galvanometer is that in connection
with which an astatic needle is employed, by the use of which the
sensitiveness of a galvanometer is greatly increased.

An astatic needle is a combination of magnetised needles _with their
poles turned opposite ways_.

At Fig. 85 a diagram of such an instrument is shown. Two magnets _D_
and _C_ are joined, with the north pole of one over the south pole
of the other, forming one suspended system. In the ordinary form of
astatic galvanometer the needles _D_ and _C_ are about two inches long,
and are each covered by a coil, these latter being so joined that the
current must circulate in opposite directions round the two so as to
deflect both magnets similarly. The deflection of the needles _D_ and
_C_ is observed by means of a pointer or glass needle _A_, _B_, rigidly
connected with the astatic system by a prolongation of the brass rod
connecting the needles _D_ and _C_. The coils are flat and of the shape
indicated in Fig. 85, and are also made in two halves, placed side by
side with just sufficient space between them to allow the rod to hang
freely.

This form of galvanometer, though less delicate than the preceding one,
is still a very sensitive one, and should only be applied in the case
of fine and delicate tests.

_Differential Galvanometer._--A differential galvanometer consists of
a magnetic needle surrounded by two separate coils of equal length and
material carefully insulated from each other and wound in opposite
directions. In using it one circuit acts against the other. If a
current of equal strength were passing through each there would be no
deflection of the needle, because the influence in both directions is
equal. If one current were stronger than the other, the needle would be
deflected by the stronger.

This form of galvanometer will be found extremely useful in connection
with a system of electrical tests.

Latimer Clark's double shunt differential galvanometer is the
instrument best adapted for submarine mine tests.

_Detector Galvanometer._--A detector galvanometer is usually made with
a vertical needle, and is employed to detect and roughly estimate the
strength of a current where no particular accuracy is required.

It consists of a magnetic needle pivoted in the centre of a coil of
insulated wire, and having an index needle attached to move with
it, the latter appearing on a dial, divided into 360 equal arcs or
portions: a diagram of such an instrument is shown at Fig. 86.

This instrument should be of small size and portable form, and as
sensitive as it is possible to make it, under such conditions.

_Three Coil Galvanometer._--The three coil galvanometer is provided
with a vertical needle, and is in other respects very similar in
appearance to the detector galvanometer before described. It is formed
with three coils of 2, 10, and 1000 ohms resistance; each coil is
connected with a brass plate on the top of the box which encloses the
whole, and may be switched into circuit by means of a plug at will. The
object of the three resistances is to suit the different resistances
that may occur, with a perfect, or imperfect state of the electrical
combination in connection with each mine. A diagram of this instrument
is shown at Fig. 87, the dotted portions are inside the case.

_Thermo Galvanometer._--A thermo galvanometer is an instrument used to
ascertain the power of a firing battery which is employed to ignite
platinum wire or low tension fuzes.

The form of thermo galvanometer generally used in connection with a
test table, is arranged as follows:--

Two ebonite studs, fitted with brass connecting screws, are fixed
to the lid of a box containing some resistance coils, and placed in
circuit with them; these studs, placed about ·3 of an inch apart, are
arranged to receive a piece of platinum wire which is stretched from
one stud to the other; the firing battery being placed in circuit with
the platinum wire, and the resistance coils, its working power would
then be tested by the fusion of the wire through a given electrical
resistance, as indicated by the resistance coils put in circuit.

Another form of thermo galvanometer, which is very compact and
portable, is shown at Fig. 88. It consists of a wooden box _a_, with
a cover of ebonite _b_, within the box is placed a resistance coil
_c_; _d_ and _e_ are two ebonite standards ·3" apart, the former of
which is connected by a copper wire with the terminal _f_, the latter
to the terminal _g_; the terminal _h_ is similarly connected to the
contact piece _k_, and the terminal _l_ to the firing key _m_, at
_n_; the resistance coil _c_ is connected to the terminal _g_ and to
the copper wire _n_; the platinum wire (of which several lengths are
used, according to the resistance of the coil _c_) is placed between
the standards _d_ and _e_. To test a battery, it is only necessary to
connect it to the terminals _f_ and _h_, when by pressing down the key
_m_ the power of the battery, according as to its fusing or not the
platinum wires, will be ascertained; the use of the terminals _g_ and
_l_ is to cut out the resistance, which is effected by connecting them
by means of a copper wire.

_Siemens's Universal Galvanometer._--Siemens's universal galvanometer
is an instrument combining in itself all the arrangements necessary for
the following operations:--

1.--For measuring electrical resistances.
2.--For comparing electromotive forces.
3.--For measuring the intensity of a current.

The instrument which is shown in elevation and plan at Pl. xxiii.,
Figs. 1 and 2 respectively, consists of a sensitive galvanometer which
can be turned in a horizontal plane, combined with a resistance bridge
(the wire of which bridge instead of being straight is stretched round
part of a circle). The galvanometer has an astatic needle, suspended
by a cocoon fibre, and a flat bobbin frame wound with fine wire. The
needle swings above a cardboard dial divided in degrees; as however,
when using the instrument the deflection of the needle is never read
off, but the needle instead always brought to zero, two ivory limiting
pins are placed at about 20 degrees on each side of zero.

The galvanometer is fixed on a graduated slate disc, round which the
platinum wire is stretched. Underneath the slate disc three resistance
coils of the value of 10, 100, and 1000 Siemens' units are wound on a
hollow wooden block, which protrudes at one side, and on the projection
carries the terminals for the reception of the leading wires from
the battery and unknown resistance. The adoption of three different
resistance coils enables the measuring of large as well as small
resistances with sufficient accuracy.

[Illustration: GALVANOMETERS FOR TESTING.

PLATE XXII]

The whole instrument is mounted on a wooden disc, which is supported
by three levelling screws, so that it may be turned round its axle.
On the same axle a lever is placed which bears at its end an upright
arm, carrying a contact roller. This roller is pressed against the
platinum wire round the edge of the slate disc by means of a spring
acting on the upright arm, and forms the junction between the _A_ and
_B_ resistances of a Wheatstone's bridge, which resistances are formed
by the platinum wire on either side of the contact roller, one of the
three resistance coils forming the third resistance of the bridge.
_G_ is the galvanometer, _k_ a milled head from which the needles
are suspended, and by turning _k_ they can be raised or lowered, _m_
is the head of a screw which arrests or frees the needle when in
motion. _h__{1}, _h__{2}, _h__{3}, _h__{4}, are the terminals of the
respective ends of the three resistance coils, viz., 10, 100, and 1000
units, which are wound on the wooden block _C_; these terminals may be
connected to each other by means of stoppers, and therefore one or
more of the resistances may be brought into circuit as desired, and to
the ends of these terminals the wires of the artificial resistances
are connected as shown on diagrams Pl. xxiv., Figs. 1, 2, 3_a_ and
3_b_; _f_ is the graduated slate disc, round which the platinum wire is
stretched in a slight groove at the edge of the disc, and is inserted
in such manner that about half its diameter protrudes beyond the slate.
The ends of the platinum wire are soldered to two brass terminals _l_
and _l_^{1}, which are placed at the angles formed by the sides of
the gap in the slate disc, and which form the junctures, as in the
ordinary resistance bridge, between _A_, _n_, and the galvanometer on
one side, and _B_, _X_, and the galvanometer on the other side, of the
parallelogram. The terminal _l_ is permanently connected by a thick
copper wire or metal strip to terminal _h__{1}, and the other terminal
_l_^{1} is connected in a similar manner to terminal III.

Slate is adopted for the material of which to make the disc _f_,
because it is found by experience to be the material which is the least
sensitive to variations in the weather or temperature.

The slate disc is graduated on its upper edge through an arc of 300
degrees, zero being in the centre, and the graduations figured up to
150 on each side at the terminals _l_ and _l_^{1} of the bridge wire.

In the centre of the circular plate _E_ of polished wood, supported
upon three levelling screws _b_, _b_, _b_, a metal boss is inserted,
in which turns the vertical pin _a_ which carries the instrument. This
pin, being well fitted to the boss, supports the instrument firmly, but
at the same time allows it to be turned freely round its vertical axis
without losing its horizontal position when once obtained.

On the arm _D D_, which turns on the pin _a_, and somewhat behind the
handle _g_, there is a small upright brass arm _d_ turning between
two screw points _r_, and carrying in a gap at its upper end a small
platinum jockey pulley _e_ turning on a vertical axis. This pulley
forms the movable contact point along the bridge wire, against which it
is kept firmly pressed by means of a spring acting on the arm _d_. The
arm _D D_, which is insulated from the other parts of the apparatus, is
permanently connected with the terminal I. On the top of _d_ a pointer
_Z_ or a vernier is fixed, which laps over the upper edge of the slate
disc and points to the graduations.

To the pin _a_ is attached a circular disc of polished wood _C_,
about one inch thick, and having a groove turned in its edge for the
reception of the insulated wires composing the resistances. The disc
_C_ has a projection _c_, which carries the five insulated terminals
marked I., II., III., IV., V., as shown on Figs. 1 and 2, Pl. xxiii.
Terminals III. and IV. can be connected by a plug, II. and V. by the
contact key _K_. Terminal I. is in connection with the lever _D D_.

Figs. 3 and 4, Pl. xxiii. show the shunt box supplied with the
galvanometer if specially desired; the copper connecting arms _a_,
_a_ are screwed to the terminals II. and IV. By inserting a plug at
_c_ (Fig. 4, Pl. xxiii.), the galvanometer is put out of circuit
altogether, whilst by plugging either of the other holes shunts of the
value of 1/9, 1/99, or 1/999, are introduced into the circuit, and
the effect upon the galvanometer is reduced to 1/10, 1/100, 1/1000,
respectively of what it would have been without the insertion of the
shunt.

Figs. 5 and 6, Pl. xxiii., show a battery commutator allowing to bring
into the circuit four different amounts of battery power. It is placed
in the battery circuit whenever consecutive tests with different
batteries are desired to be made, it being only necessary to change
the place of the stopper in the battery commutator, the terminal screw
_a_ of the battery commutator being connected to terminal V. of the
galvanometer, and the screws _b_, _b_, _b_, _b_ to various sections of
the battery: see diagram of connections, Fig. 4, Pl. xxiv.

The application of the universal galvanometer will be clear from the
diagrams on Pl ii.; instructions, however, for its practical use are
added further on, and also tables for use when measuring conducting
resistances.

As will be seen from diagram, Fig. 1, Pl. xxiv., the proportion between
the unknown resistance X, and the artificial resistance _n_ is, when
the deflection is read off on the side of the slate disc marked _A_:

X : _n_ = 150 + _a_ : 150 - _a_

or, X = ((150 + _a_) / (150 - _a_)) × _n_.

but if read off on the _B_ side of the disc--

X = ((150 - _a_) / (150 + _a_)) × _n_.

The values of these two fractions, for every half degree, will
be found in the columns headed _A_ and _B_ of the table in the Appendix.

[Illustration: SIEMEN'S UNIVERSAL GALVANOMETER.

PLATE XXIII]

[Illustration: SIEMEN'S UNIVERSAL GALVANOMETER.

PLATE XXIII^A]

[Illustration: SIEMEN'S UNIVERSAL GALVANOMETER.

PLATE XXIV]

[Illustration: SIEMEN'S UNIVERSAL GALVANOMETER

PLATE XXIV^A]

_Measuring Electrical Resistances._--For this purpose the instrument is
arranged as a Wheatstone's balance. The connections are made as shown
at Pl. xxiv., Figs. 1 and 5, where _X_ is the unknown resistance.

_a._--The needle _i_ is to be brought to the zero
point of the small cardboard scale by turning the
galvanometer _G_ round its vertical axis, taking care
that the needle moves with perfect freedom.

_b._--The pointer or vernier _Z_ is to be brought, by
means of the handle _g_, to the zero point of the large
scale on the slate disc.

_c._--A plug is to be inserted between the terminals
marked III. and IV.

_d._--The holes 10, 100, and 1000 are, two of them, to
be plugged, and one left open, according to the extent
of the unknown resistance to be measured; either 10 or
100 must be left open if the resistance is small, and
1000 if it is large.

_e._--The two ends of the unknown resistance are to be
connected to terminals II. and IV.

_f._--The two poles of some galvanic battery are to be
connected to terminals I. and V.

When the above-mentioned connections have been made, and on depressing
the key _K_, the battery current is sent into the combination and
deflects the needle, say, to the right-hand or _B_ side of the
instrument, the pointer or vernier _Z_ must then be pushed, by means of
the handle _g_, to the _B_ side of the instrument. If this is found to
increase the deflection of the needle _i_, the pointer _Z_ should be
pushed to the other or _A_ side of the instrument beyond the zero point
of the large scale until the needle remains stationary when the key _K_
is depressed.

The number indicated by the vernier _Z_ should be read off carefully,
and notice taken whether it is on the _A_ or _B_ side of the large
scale. This number must then be referred to the galvanometer table,[K]
when the figure opposite to the number, multiplied by the resistance
unplugged, is the resistance of _X_. The value of the resistance to be
determined will be thus found by a single operation.

Supposing the reading to be 50 on the _A_ side of the large scale, the
resistance _n_ unplugged having been 100 units, we get according to the
before-mentioned law of resistance bridge the following proportion (see
Fig. 5, Pl. xxiv.):--

X : 100 = 150 + 50 : 150 - 50

X = ((150 + 50) / (150 - 50)) × 100

X = 200 units.

For measuring very small resistances a single cell will be found
sufficient; but for large resistances more should be used, say, 15 to
20. If very accurate measurements of small resistances are to be taken,
the screw at the end of the moving arm _D D_ should receive one battery
wire, terminal V. receiving the other.

_Comparing Electromotive Forces._--For this purpose Professor E. du
Bois-Reymond's modification of Poggendorff's compensation method is
used.

The connections are made as shown at Pl. xxiv., Figs. 2 and 6.

For comparing two electromotive forces _E__{1} and _E__{2}, a third
electromotor of higher electromotive force _E__{0} is used, and two
separate tests taken.

The manipulations _a_ and _b_ are to be the same as before.

_c._--The hole between III. and IV. to be left
unplugged.

_d._--Plugs to be inserted in 10, 100 and 1000.

_e._--The two poles of the electromotor of an
electromotive force _E__{0} are to be connected to the
terminals III. and V.

_f._--The poles of the battery whose electromotive
force _E__{1} is to be compared are connected to
terminals I. and IV. in such a manner that the similar
poles of the two electromotors are joined to terminals
I. and III., and to IV. and V. respectively.

When depressing the key _K_ the galvanometer needle will be deflected
and can be brought back to zero by turning the pointer _Z_ either to
the right or to the left. Should for instance the pointer have to be
brought to 30° on the _A_ side we have the following equation--

E_{1} = E_{0} × ((150 - 30) / ( 300 + _n_)) (1),

where _n_ is the resistance of the battery _E__{0}.

The electromotor _E__{2} is now to be inserted in the place of _E__{1},
and the galvanometer needle, when it deflects, again brought back to
zero by moving the pointer _Z_. If for instance the pointer has to be
pushed to 40° on the _B_ side to obtain equilibrium we have--

E_{2} = E_{0} × ((150 + 40) / ( 300 + _n_)) (2).

By eliminating _n_ from equations 1 and 2 we have

E_{1} : E_{2} = (150 - 30) / (150 + 40) = 12 : 19 (3).

The two electromotive forces are in the same proportion as the two
observed distances of the pointer _Z_ from 150° on the _A_ side of the
instrument.

_For measuring the Intensity of a Current._--For this purpose the
instrument is simply used as a sine galvanometer. The connections are
made as shown at Pl. xxiv., Figs. 3_a_ and 7.

The manipulations _a_, _b_, _c_, and _d_ same as in the second case.

_e._--Connect one pole of a battery to terminal II. and
put the other pole to earth.

_f._--Connect the line to terminal IV.

The galvanometer is then to be turned in the same direction as the
needle is deflected until the needle coincides with the zero point.
Whilst this is being done the large scale on the slate disc will move
under the pointer _Z_, which must be left stationary; the sine of the
angle indicated by _Z_ will thus give the value proportionate to the
strength of the current. Should the shunt box be required, it has to be
connected with terminals II. and IV.

Fig. 4 shows the same connections as Fig. 7, but without the shunt box,
and with the battery commutator. Fig. 3_{a} shows diagram of the same
connections but with the key _K_, and Fig. 3_{b} the same without the
key.

_A Shunt._--A "Shunt" is a second path offered to a current traversing
a given circuit, or portion of a circuit, so as to diminish the amount
of the current flowing through that portion of the circuit. In the
diagram shown at Fig. 89 the shunt diminishes the amount of the current
flowing along the circuit between _A_ and _B_.

If only 1/Nth of the current is to pass along the circuit between _A_
and _B_ (of resistance _R_) then the resistance of the shunt must equal
R/(N - 1).

By the aid of shunts it is quite possible to make use of very sensitive
instruments to measure powerful currents.

_Commutators or Switch Plates._--A commutator or switch plate is an
apparatus by which the direction of currents may be changed at will, or
by which they may be opened or closed. Bertin's commutator, which is
represented at Fig. 90, consists of a small base of hard wood on which
is an ebonite plate, this by means of the handle _m_ is turned about a
central axis between two stops _c_ and _c'_. On the disc are fixed two
copper plates, one of which _o_ is always positive, being connected by
the axis and by a plate (+) with the binding screw _P_, which receives
the positive electrode of the battery; the other copper plate _i_,
_e_, bent in the form of a horse-shoe, is connected by friction below
the disc with a plate (-), which plate is connected with the negative
electrode _N_. On the opposite side of the board are two binding screws
_b_, and _b'_, to which are attached two elastic metal plates _r_, and
_r'_.

On the disc being turned as shown in the figure, the current coming by
the binding screw _P_ passes into the piece _o_, the plate _r_, and
finally the binding screw _b_, which by means of a copper wire leads
the current to the apparatus in connection with _b_; then returning to
the binding screw _b'_, the current reaches the plate _r'_, the piece
_i_, _e_, and so to the battery by the binding screw _N_.

If the disc is turned so that the handle _m_ is half way between _c_
and _c'_, the pieces _o_ and _i_, _e_, being no longer in contact with
the plates _r_ and _r'_, the current will not pass. If _m_ is turned as
far as _c_, the plate _o_ will then touch _r'_, and the current pass to
_b'_, and return by _b_, thus reversing its direction.

"Peg" switches are also often used; they are arranged so that the
removal or insertion of a brass peg or plug cuts out, or completes a
circuit.

_Rheostat._--A rheostat is an instrument used for the comparison of
resistances.

[Illustration: SHUNT, COMMUTATOR, RHEOSTAT.

PLATE XXV]

Wheatstone's rheostat, which is shown in elevation at Fig. 91,
consists of two cylinders _A_ and _B_, one of brass and the other of
non-conducting material, so arranged that a copper wire can be wound
off the one on to the other by turning a handle _C_. The surface of
the non-conducting cylinder _B_ has a screw thread cut in it for its
whole length, in which the turns of the copper wire lie, so that
its successive convolutions are well insulated from each other. Two
binding screws _D_, _D'_ connected with the ends of the copper wire are
provided, to which the circuit wires are connected. A scale is attached
at _E_, by means of which the number of convolutions on _B_ can be read
off; and parts of a revolution are indicated on a circle at one end.
The handle _C_ can be shifted from one cylinder to the other.

Supposing the rheostat introduced into a circuit, and the whole of the
copper wire wrapped on the metal cylinder _A_, then, on account of the
large section of this metal cylinder, its resistance may be entirely
neglected, but for every convolution of the wire on the non-conducting
cylinder =B=, a specific resistance is introduced into the circuit.
The amount of resistance can thus be varied as gradually as desired by
winding on and off the cylinder _B_. This instrument is often used in
connection with the thermo galvanometer.

_Resistance Box._--The general arrangement of a resistance box is shown
in the diagram Fig. 92.

Between two terminal binding screws _T_ and _T__{1} secured on a
vulcanite slab are fixed a series of brass junction pieces _a_, _b_,
_c_, _d_; each of these is connected by a resistance coil to its
neighbour, as shown at 1, 2, 3, and 4. A number of brass conical
plugs with insulating handles of vulcanite are provided, which can be
inserted between any two successive junction pieces, as between _T_ and
_a_, or _a_ and _b_.

With all the plugs inserted, the electrical current will flow direct
from _T_ to _T__{1}, the large metallic junction pieces directly
connected by the plugs would offer no sensible resistance; but if all
the plugs were removed, then the current would flow through each of the
coils 1, 2, 3, and 4, and the resistance in the circuit would be the
sum of the resistances of those four coils. With the plugs arranged
as in the figure, the current would flow through coil 4 only, and the
resistance in the circuit would be equal to the resistance of that coil.

_Wheatstone's Balance._--The electrical conductivity of a body is
determined by ascertaining the ratio between the resistance of a
certain length of the conductor in question, having a given section, to
that of a known length of a known section of some substance taken as a
standard.

For this purpose Wheatstone's bridge in connection with a box of
resistance coils is the most convenient method.

At Fig. 94 is shown Wheatstone's balance (Post-office pattern), and
at Fig. 93 the apparatus is reduced into the form of a parallelogram,
which is the usual diagram of Wheatstone's bridge. The theory of the
bridge is as follows:

Four conductors _A B_, _B C_, _A D_, and _D C_ are joined at _A_ and
_C_ to the poles of a battery _Z_; the resistance between _A_ and _B_
is _R_; that between _A_ and _D_ is _r_; that between _D_ and _C_ is
_R__{1}; and that between _B_ and _C_ is _x_, the unknown resistance to
be measured. A convenient constant ratio is chosen for _R__{1} and _r_,
such as equality 1 to 10, 1 to 100, or 1 to 1000; and then _R__{1} is
adjusted until no current flows through the galvanometer _G_; when this
is the case we have R : _r_=R_{1} : _x_, or _x_ = (_r_/R) × R_{1}; so
that if _r_ = R/100, _x_ will be equal to R_{1}/100.

Two keys _a_ and _b_ are inserted; the current is wholly cut off the
four conductors until contact is made at _a_; and then after the
currents in the four conductors have come to their permanent condition,
contact is made at _b_ to test whether any current flows through the
galvanometer. The three resistances _R_, _R__{1} and _r_ and the
resistance of the galvanometer should be small if _x_ is small, and
great if _x_ is great.

The conductors _A B_ and _A D_ of the bridge are each formed of
three resistance coils having a resistance of 10, 100, and 1000 ohms
respectively, inserted between the terminals _B_ and _D_ of the
balance, Fig. 94.

The conductor _D C_ is formed of a set of resistance coils from 1 up
to 4000 ohms, amounting altogether to 11,110 ohms, inserted between
the terminals _D_ and _C_ of the balance; in the balance, a brass plug
being inserted between the terminals _D_ and _D__{1}, they may be
considered as one terminal _D_. The conductor _B C_ is the wire to be
tested, and is connected to the terminals _B_ and _C_ of the balance.

_Measurement of Resistances._--When a resistance is to be measured
that is within the range of the coils in _R__{1}, _R_ and _r_ are
made equal. The needle of the galvanometer will move in a different
direction, either to the right or to the left, according as the
resistance in _R__{1} is greater or less than the line wire _x_. The
needle remains at zero only when the resistance in _R__{1} is equal to
that in _x_. For _r_ : _R_ :: _R__{1} : _x_.

[Illustration: WHEATSTONE'S BRIDGE.

PLATE XXVI]

When the resistance of _x_ is greater than that of _R__{1}, as in an
insulation test, the resistance in _r_ is made _less_ than that in _R_,
in order that _r_ and _R_ may have such a proportion one to the other
as will enable the coils in _R__{1} to balance a resistance in _x_,
greater than their own, that is to say, greater than 11,100 ohms; thus
_r_ : _R_ :: _R__{1} : _x_, or 10 : 1000 :: 10,000 : 1,000,000, the
resistance in the line to be tested would be 1,000,000 ohms, supposing
the values of _r_, _R_ and _R__{1} to be respectively 10, 1000, and
10,000 ohms.

When the resistance to be tested is less than that of the least coil
in _R__{1} (1 ohm), then the resistance in _r_ is made greater than
in _R_. Thus _r_ : _R_ :: _R__{1} : _x_, or 100 : 10 :: 2 : 0·2; the
resistance of the line to be tested would in this case be 1/20 of an
ohm.

_Manipulation._--In all cases the key in connection with the battery
should first be depressed, then the galvanometer key, making very short
contacts by the latter, just sufficient to show the direction of the
deflection, until the coils in _R__{1} are nearly adjusted, otherwise
considerable time will be lost in making a series of tests, owing to
the swing given to the needle, which will take some little time before
it again remains steady at zero. When once the coils in _R__{1} are
adjusted, and a balance obtained, it should be ascertained whether the
needle will remain steady when contact is made and broken.

_Test Tables._--In connection with a system of testing electrical
submarine mines, for the sake of convenience and simplicity it is
necessary to use a table (termed a "Test Table"), on which all the
apparatus used for the purpose of testing are fixed. Several forms of
tables have been designed for such a purpose. At Fig. 95 is shown the
method of arranging such a table.[L]

_A_ is an astatic galvanometer placed between two switch plates, _B_
and _C_; ten other similar switch plates, 1, 2, 3, 4, _D_, 5, 6, 7,
_E_, and 8, are arranged in front of the galvanometer _A_; _F_, _G_,
and _H_ are three terminal plates; _K_ is a box of resistance coils
used in connection with the thermo galvanometer _M_; _L_ is a firing
key, and _N_ a battery commutator; _O_ is a three-coil galvanometer;
_R_ is a Wheatstone balance (Post-office pattern).

The ten switch plates, 1, 2, 3, 4, _D_, &c., are used for the
connection of any particular line to be tested, as well as for the
earth connections and instruments employed in that operation.

_"Sea Cell" Tests._--The arrangement shown in the figure is that
required in connection with the sea cell test, and Mr. Brown's method
of keeping certain earth plates in a bucket instead of in the sea.

If two plates of suitable metal to form a Voltaic battery are placed in
salt water and connected by a metallic conductor, a battery is at once
formed capable of producing considerable deflection on a moderately
delicate galvanometer. Testing by this arrangement has been termed the
"sea cell" test.

_Arranging Earth Plates._--Mr. Brown's, Assistant-Chemist to the War
Department, method of arranging the earth plates is as follows:--

A series of earth plates, such as copper, carbon, tin, zinc, &c., are
placed in a bucket filled with sea water, and which is placed in the
testing room. The water in the bucket is put in connection with the
water of the sea by means of a conducting wire, terminating at one end
with a zinc plate in the bucket, and at the other with a zinc plate in
the sea. By this means the tests made with the different earth plates
in the bucket are identical with those made with corresponding earths
placed absolutely in the sea, and therefore these latter may be done
away with, the sea cell tests being entirely carried out by means of
the bucket earth plates.

In addition to the bucket earth plates there will be several other
earth plates in connection with the testing room, these being placed in
the sea, such as the zinc earth for the firing battery, the zinc earth
for the signalling battery, &c.

_Connections of Switch Plates._--The switch plate _D_ is used for the
connection of any particular mine cable which it may be required to
test. The switch plate _E_ is connected with a zinc earth plate used
for testing the firing battery. This must always be in the sea. The
switch plate 1 is in connection with a zinc earth in the bucket; 2 is
attached to a copper earth plate in the bucket; 3 is attached to a
carbon earth plate in the bucket; 4 to a tin earth plate in the bucket;
5 is used for connection with the zinc signalling earth connection in
the sea; 6 is attached to a copper earth plate used for the sea cell
test, or any other purpose required, in the sea; 7 is attached to a
zinc earth plate in the sea; and 8 is a common zinc earth in the sea.

The terminal plates _G_ and _H_ are used for the connection, for
testing purposes of the negative and positive poles, of the firing
battery, and _F_ is connected with a zinc earth in the sea, for a
similar purpose. These plates are in connection with the resistance
coils _K_ and the thermo galvanometer _M_, employed for testing the
firing battery, the circuit being closed by the firing key _L_. Other
ways of using these plates may of course be adopted if desired. The
resistance coils _K_ range from 0·5 to 100 ohms, and are composed of
wire adapted for the passage of a quantity current. A reversing key is
generally used in connection with a testing battery and the three-coil
galvanometer _O_. This reversing key would consist of two bridges
completely insulated from each other, the upper one attached to the
negative, the lower one to the positive pole of the test battery. In
their normal position both keys press against the upper bridge, and
until one or other of the keys is pressed down no current will pass,
the direction of the current being altered by pressing down a different
key. The point of each key is provided with a terminal and connected,
the one to a zinc earth through the switch plate 8, the other to one
terminal of the three-coil galvanometer when the tests are to be
applied.

The Wheatstone balance _R_ is used in finding the resistances of
electrical cables, balancing fuzes, &c. By means of a commutator, _N_,
the necessary number of cells for any particular test may be thrown in
circuit when required.

_Test of Platinum Wire Fuze for Conductivity._--The platinum wire fuze
may be tested electrically as follows:--

If placed in circuit with a few cells of a Daniell or Leclanché
battery and a detector galvanometer, before the platinum wire bridge
of the fuze is fixed, there should be no deflection of the needle,
for no metallic circuit exists; if it did, such would be fatal to the
efficiency of the fuze. If similarly placed in circuit after the bridge
has been fixed, a considerable deflection of the needle should result,
such deflection being due to the current passing through the metallic
bridge, which to be efficient ought to be the sole medium through which
the circuit is completed.

_Test of Resistance of Platinum Wire Fuze._--The electrical resistance
of a platinum wire fuze is ascertained by means of the Wheatstone's
balance _R_ and galvanometer _A_, Fig. 95. The terminals of the fuze
are connected to the binding screws of the balance, the commutator _N_
and galvanometer _A_ being connected up in circuit. The resistance of
the coils is then adjusted by taking out plugs until the needle of the
galvanometer _A_ is brought to zero, when the sum of the resistances
indicated by the unplugged coils will be equal to that of the fuze. The
resistance of a platinum wire fuze might also be ascertained by means
of a differential galvanometer instead of a Wheatstone balance.

The electrical resistance of 3/10" of fine platinum wire, weighing 1·9
grains to the yard, is 3/10 of an ohm nearly (Schaw).

_Testing High Tension Fuzes._--High tension fuzes require very delicate
and careful management in testing them, due to the high electrical
resistance of such fuzes, which ranges from 1500 to 2000 ohms, combined
with the danger of premature explosion when testing even with a small
number of battery cells. Very sensitive galvanometers, such as the
reflecting galvanometer, should if possible be used, otherwise the mode
of making the tests for conductivity and resistance of a high-tension
fuze is similar to that already given for a platinum wire fuze.

Detonating fuzes should always be placed in an iron case during the
process of testing.

_Insulation Test for Electrical Cables._--To test an electrical cable
for insulation, it should first be put in a tank of water, or in the
sea, and allowed to soak for at least forty-eight hours. The object of
this is to allow the water to penetrate the outer protection of hemp
and iron wires, &c., and to search out and get into any weak places
there may be in the insulation under the armouring. At Fig. 96 is
shown the method of performing this test. _A_ is a tank holding the
electrical cable, which has been in soak for forty-eight hours; _B_ is
an astatic galvanometer; _C_, _Z_ a Leclanché or Daniell battery of
great power; and _C_ is an ordinary firing key. One end of the electric
cable _D_ is connected to the galvanometer _B_ through the firing key
_C_; the other end of the cable is very carefully insulated; one pole
of the battery is connected to the galvanometer _B_, the other is put
to earth in the tank at _F_; should the insulation be perfect, no
deflection of the needle should follow on the key being pressed down.
A very slight deflection might be observed on a moderately sensitive
galvanometer, due to the current passing through the insulation; its
whole length being immersed, the surface through which such a current
would pass would be large, and the sum of the infinitesimally small
quantities escaping over the whole length, would in the aggregate be
sufficient to deflect the needle to a small extent in completing the
circuit of the battery. Should any considerable deflection occur,
it would indicate a defect or leak in the insulation of the cable,
the extent of which would be roughly measured by the amount of such
deflection.

By using a reflecting galvanometer a very much more delicate test
would be obtained, but for the comparatively short lengths of electric
cables used in connection with submarine mines, such accuracy is hardly
necessary.

To test an electric cable for conductivity, it would be only necessary
to expose the metallic conductor _G_, and put it in the water of the
tank. If the conductivity were good, then the whole of the current
would pass through the cable and the needle of the galvanometer would
be violently deflected. If the continuity were broken, no deflection
would be observed.

_Defects observed in the Conductivity of the Cable._--To ascertain the
position of a defect in the insulation of a cable, as indicated by the
tests above described, it would be only necessary to keep a continuous
current flowing through the cable, and gradually take it out of the
tank. If the fault existed at a single point, the deflection of the
needle would be suddenly reduced at the moment of that point of the
cable being lifted out of the water, and therefore its position would
be determined with considerable accuracy. Should several defects exist
as each was lifted out, a sudden reduction of the deflection would
occur.

_Discharge Test._--The conductor of an electrical cable may be broken
without destroying the insulation, and on applying the foregoing
tests, good insulation would be indicated, but no conductivity, and no
information would be given as to the position of the fault. Under such
circumstances the following test must be applied:--

Put one pole of a very powerful battery to earth, and charge one
end of the defective cable, then immediately discharge it through a
reflecting galvanometer, and note the extreme limit of the swing of the
needle, then, charge the other end of the cable in a similar manner,
and discharge it through the same galvanometer, noting as before the
swing of the needle. This should be done three or four times, and the
average of the deflections taken. Then the position of the fault would
be indicated by the proportion between the average deflections in each
case, and the cable might safely be cut at that point. Should the
precise position of the fault not be discovered in thus cutting the
cable, each section should be tested again for conductivity, and that
in which a fault was still found to exist should be again tested by the
discharge as before.

_Test of Electrical Resistance of Cable._--This is effected by
balancing it against the Wheatstone balance, in a similar manner to
that explained for a fuze. The electrical resistance of the conductor
of a cable affords a very correct indication of the quality of the
metal of which it is composed. For a very delicate test the reflecting
galvanometer should be used.

_Electrical Test of Insulated Joints._--Insulated joints and
connections, whether of a permanent or temporary nature, should be
tested electrically, in a precisely similar manner to that explained
for electric cables.

They should be soaked for forty-eight hours, and then tested for
insulation, conductivity, and electrical resistance.

In testing permanent joints special tests are carried out, which are
described by Mr. Culley in his 'Handbook of Practical Telegraphy.'

Voltaic batteries should be subjected to the following tests:--

1.--For potential.
2.--For internal resistance.
3.--For electromotive force.

For the purpose of testing the potential of a battery, one pole should
be put to earth, and with the other one pair of the quadrants of a
Thomson's reflecting galvanometer should be charged; when this is done,
a certain deflection of the spot of light will occur, and the amount
of such deflection, as compared with that produced by a standard cell
applied to the instrument in a similar manner, would give the relative
value of the potential of the battery.

The following method of determining the internal resistance of a
battery is that recommended by Mr. Latimer Clark in his book on
electrical measurements.

The instrument employed is a double shunt differential galvanometer,
a diagram of which is shown at Fig. 97. Connect the battery and a set
of resistance coils in circuit between the terminals _A_ and _D_, and
insert plugs in the resistance coils so that they give no resistance;
insert plugs at _A_ and _C_, and also both the shunt plugs at _A_ and
_D_. The current will now flow through one half of the galvanometer
circuit only, being, however, reduced to 1/100 of its amount by the
shunt _D_; the deflection of the needle must be carefully read. The
plug _A_ must now be removed to _B_, which causes the battery current
to flow through both halves of the galvanometer (each being shunted).
The circuit will now be as shown in the figure, and the needle will
of course be deflected somewhat more than before. Now unplug the
resistance coils which are in circuit with the battery until the
deflection of the needle is reduced to its original amount, and the
resistances unplugged will be equal to the internal resistance of the
battery.

The following is another method of ascertaining the internal resistance
of a battery cell.

A circuit is formed, consisting of the battery cell, a rheostat, and
a galvanometer, and the strength _C_ is noted on the galvanometer.
A second cell is then joined with the first, so as to form one of
double the size, and therefore half the resistance, and then by adding
a length _l_ of the rheostat, the strength is brought to what it
originally was, _C_.

Then if _E_ is the electromotive force, and R the resistance of cell,
_r_ the resistance of the galvanometer, and other parts of the circuit,
the strength _C_ in the one case is C = E / (R + _r_), and in the other
= E / ((1/2)R + _r_ + _l_), and since the strength in both cases is the
same, R = 2_l_, i.e., the internal resistance of the cell is equal to
twice the resistance corresponding to the length _l_ of the rheostat
wire.

The comparative electromotive force of a battery may be determined by
means of a double shunt differential galvanometer in the following
method, as recommended by Mr. Latimer Clark.

"This can only be done relatively in terms of some other standard
battery. First determine the resistance of the standard and of the
other cells to be measured; then insert the shunt plugs at _A_ and _D_,
Fig. 97, and also at _C_ and _B_, and join up the standard cell in
circuit with a resistance coil to the terminals _A_ and _D_, and unplug
the resistance coils until a convenient deflection is obtained, say
15°; note the sum of the resistances in circuit, including that of the
battery galvanometer, resistance coil and connecting wires; now change
the battery for another, and by unplugging the resistance coils bring
the needle again to the same deflection, 15°; having again found the
total resistance in the circuit, the relative electromotive force will
be directly proportional to these resistances."

The electromotive force of a battery may also be measured statically
by means of Thomson's quadrant electrometer, the poles of the battery
being connected with the two chief electrodes of the instrument, in
which arrangement no current will pass, and the electromotive force
will be directly indicated by the difference of potential observed.

In the case of a quantity battery, that is, a battery capable of fusing
a fine platinum wire, its electromotive force and internal resistance
may be determined by means of the resistance coils _K_, and thermo
galvanometer _M_, shown at Fig. 95.

_Tests after Submersion._--After an electrical submarine mine has
been placed in position, it should be immediately tested to ascertain
that all is right, and similar tests should be applied at intervals
to ascertain that the charge remains dry; that the insulation and
conductivity of the electric cable remains the same; and that its
electrical resistance indicates a state of efficiency.

The nature of the tests applied to determine these points will depend
upon the nature of the combination in which the mine is arranged.

The manner of applying the "sea cell" test, by which is ascertained the
condition of a system of electrical submarine mines, will be readily
understood from the following examples.

The arrangements for testing to ascertain whether a charge is dry, or
wet, is shown at Fig. 98.

_z_ is a plate of zinc introduced in the circuit within the charge, and
between the fuze and the shore; another earth plate of carbon _x_ is
connected with the electric cable beyond the fuze, forming the ordinary
earth connection of the system at that point; and at home a copper
earth plate _c_ is used.

First, in the case of a dry charge with the insulation and conductivity
of the cable, good; under these circumstances there would be formed a
sea cell between the earth plates _x_, and _c_, which would produce a
certain deflection of the needle of a galvanometer _g_, which is placed
in the circuit, and in a certain direction.

Secondly, in the case of a charge becoming wet, through leakage,
with the insulation and conductivity of the cable, good; under these
circumstances, a sea cell would be formed between the plates _c_ and
_z_, causing a different deflection of the needle in amount and in
direction, by which it would be at once indicated that the charge had
become wet.

[Illustration: TEST TABLE, DIFFERENTIAL GALVANOMETER.

PLATE XXVII]

_"Sea cell" Test for Insulation._--Again, in the case of the insulation
of the electric cable being damaged to such an extent as to expose
the copper conductor. Under these circumstances there would be
formed a sea cell between the copper earth plate _c_, and the exposed
copper conductor of the cable, by which a certain definite deflection
of the galvanometer would be observed, which deflection would differ
in character from that produced by the copper carbon sea cell, when
the insulation of the cable was good, and the system in working order,
and therefore it would indicate that some change in the electrical
conditions of the system had occurred. The fact that a leak existed in
the insulation would be proved by changing the earth plate at home from
copper to zinc, carbon, tin, &c.

In the case of no deflection being produced on the galvanometer, on
applying the sea cell test, a want of continuity, or inefficient
connections would be indicated.

The foregoing afford examples of the vast utility of the "sea cell"
in connection with a system of electrical tests for submarine mines,
numerous variations of which may be effected by employing a series of
earth plates, of different metals, at the home end of the circuit, in
connection with a carbon and zinc earth plate at the other end. And
the mode of manipulating these tests may, by means of numerous switch
plates, as shown at Fig. 95, be made extremely simple and efficient.

_Armstrong's System of Electrical Testing._--A very simple method of
testing electrical submarine mines, with which low tension fuzes are
used, has been devised by Captain Armstrong, R.E., and is shown at
Fig. 99. _a_ is the electric cable leading from the shore; _b_ the
cable attached to a polarised relay _c_, and connecting the charge
through the fuze _f_ to the earth; _b'_ the cable, attached to another
polarised relay _c'_, and connecting the mine with the circuit closer;
the polarised relay _c_, in the mine, is arranged to be worked by a
positive current, that is to say, the wire surrounding the core is
so wound as to increase the polarity of the electro magnet, near the
armature _d_, when a positive current is passed through it, and to
diminish the polarity when a negative current is passed through the
wire surrounding the core; the polarised relay _c'_ within the circuit
closer is arranged to be worked by a negative current, the coil being
so wound as to produce an influence exactly the reverse of _c_.

Then, a positive current passing along the line wire _a_, the
armature _d_ in the charge will be attracted, while _d'_ will remain
unaffected; again, if a negative current be circulated, the armature
_d'_ within the circuit closer will be attracted, while the armature
_d_ will remain unaffected. Two insulated wires forked together are
wound round each electro magnet, one a thin wire (_g_ and _g'_) having
a considerable resistance, about 1000 ohms, being connected direct to
the earth plates _e_ and _e'_, and the other a thick wire (_h_ and
_h'_) offering a very small resistance, and so arranged that when the
armature is attracted, they may be in contact with and complete the
circuit through the armature to earth.

The thin wire coils are so arranged that a certain number of Leclanché
cells (ten or twelve, as may be desired) will make the electro magnets
act, while with fewer cells the current would be too weak, and would
therefore pass through them to earth without affecting the armature.

By means of the three-coil galvanometer, a table of the deflections,
obtained by the foregoing system of testing, should be carefully
recorded, when the circuit is known to be in good working order, so
that any defect in the circuit would be at once indicated on the
application of the various tests, by the results so obtained differing
from those originally recorded. When a system of submarine mines is
placed in position for the purposes of practice and experiment, every
trouble should be taken to endeavour to fix the exact position of
any defect that may exist, also to ascertain its magnitude, &c., but
in time of war, should a defect exist in the system, no time must be
lost in such operations, but the mine at once lifted, and the fault
repaired, or a fresh one laid in its place, unless the presence of an
enemy or other imperative cause should prevent such work being done.

_Austrian Testing Table._--The following is a description of the
Austrian testing table, and their mode of making electrical tests with
it, in connection with their system of self-acting electrical submarine
mines.

[Illustration: METHODS OF TESTING.--ARMSTRONG,--AUSTRIAN.

PLATE XXVIII]

Its design is shown at Fig. 100; _c z_ represents the battery with one
pole to earth at _e_, and the other in connection with an intensity
coil _a_, through which the current passes to the contact plate _b_.
When it is desired to put the system of mines in connection with the
table, in a state of preparation to be fired by the contact of a
vessel, a plug is inserted between the contact plates _b_ and _f_,
and the current passes through the galvanometer _g_, and electrically
charges the conducting wires connecting the mines with the battery,
through the several binding screws on the contact plates, numbering
1, 2, 3, &c. The fact that the charge has been fired is also at once
indicated on the galvanometer _g_.

_Test to discover an Exploded Charge._--It then becomes necessary to
ascertain which particular mine of the system has been exploded; for
this purpose a separate circuit in connection with a single cell _d_
is employed. This cell is in connection through a galvanometer _g'_ (a
more sensitive instrument than the galvanometer _g_) with the pivot of
the key _h_, and rheotome _R_, which latter is connected, as shown by
the dotted lines, with each individual mine of the system attached to
the contact plates numbered 1, 2, 3, &c. The handle of the rheotome is
moved round, to each number in succession and directly it is placed in
contact with that corresponding to the exploding mine, the electrical
circuit is completed through the exposed end of the fractured wire, and
this is indicated by the galvanometer _g'_. During the testing process
the firing battery _c z_ must be disconnected; this is done by raising
one of the bridges _i i_ with which each group of ten mines is provided.

_Insulation Test._--The rheotome and testing galvanometer _g'_ are
also used to test the insulation of the electric cables connecting
the mines to the testing table. This is done in precisely the same
manner as testing for an exploded mine: the handle of the rheotome is
turned round, and each cable connected in succession with the testing
circuit as before; should the galvanometer _g'_ remain stationary,
the insulation is good; but should a defect of insulation exist, the
current passing through it would act on and deflect the galvanometer,
indicating the particular line in which it exists, and, roughly, its
extent in proportion to the deflection shown; should the fault be
considerable, the defective cable should be at once detached, as the
current lost through it might so diminish the working power of the
firing battery, as to prevent it exploding any of the fuzes attached
to the group in connection with it. By the above arrangement, the
insulation of each line can be tested at any moment required.

In making the delicate test for insulation, which should invariably
be done at leisure, and, if possible, when an enemy's vessels are
not in the vicinity of the mines, a large number of Daniell's or
other cells of suitable form should always be used. To do this,
it would only be necessary to connect such a battery in place of
a single cell permanently arranged, as described, in the testing
circuit, and to proceed with the details of the operation as before.
As the cable would, in actual work, always be charged with the full
power of a firing battery, the value of its insulation to resist an
electrical charge at such a high potential would be an important
point to determine. The fuzes being entirely out of the circuit till
the moment of the action arrives, no danger of a premature explosion
need be apprehended; if a fuze were in such a position as to be fired
prematurely, it would be exploded, in connection with the firing
circuit, independently of the operation of testing the insulation of
the cables.

_To render a Channel Safe._--In order to render the channel safe for a
friendly vessel, it is only necessary to remove the plug from between
the contact plates _b_ and _f_; this disconnects the firing battery
from the circuit.

_Defence of Harbours by Booms, &c._--Booms or cables supported by rafts
may also be employed in the defence of harbours, or rivers, either by
themselves, or in combination with submarine mines; in the latter case,
the booms, &c., may be moored either in advance of the mines, or in
rear of the front row, this last method of mooring them being the most
effective one.

There are a great variety of forms in which a boom may be constructed.
The qualities essential for a good and practicable boom are:--

1.--Great strength.
2.--Great power of resistance.
3.--Convenience in handling.
4.--Easy to manipulate.
5.--Its materials easily procurable.

_Construction of a Boom._--The general construction of a boom consists
of a main cable, buoyed up at intervals by floats. The main cable may
be either wire, chain, or rope, the former being very much superior for
this purpose to chain or rope. The floats consist of balks of timber
built round the main cable and bound together by means of iron hoops
&c. A space is left between each float, by which a certain amount of
flexibility in the boom is obtained, without which it would be of
comparatively little use, as it might be easily overrun.

It must be borne in mind, in constructing all such booms, that the
smaller the proportion of timber used in forming the floats to the
cable, consistent with buoyancy, the stronger will be the structure.

A very important feature in connection with such a mode of defence is
the manner of mooring it; for if it be moored so as to be unyielding,
then its sole power of resisting a vessel charging it is the actual
strength of the materials composing the structure, but if it be moored
so that it is capable of yielding to a sudden blow, this force will
be to some extent absorbed, and resistance of the defence greatly
increased.

The raft employed to support the main cable should be moored by means
of very heavy chains (without anchors) in the direction of the attack,
and with ordinary anchors and cables on the other side.

As a rule, the booms should be moored obliquely to the direction of the
current, where there is any, as the tendency of the current to overrun
the boom when so placed will be less, and also a ship ramming it must
place herself athwart the current to attack the boom at right angles.

_Clearing a Passage through the Torpedo Defences of an Enemy._--The
subject of clearing a passage through the torpedo defences of an
enemy is one fraught with innumerable difficulties, on account of the
varied nature and impracticability of obtaining accurate and _certain_
information of such defences, and thus it is impossible to lay down any
fixed rule or plan for carrying out such an operation.

In fact, it will be only under the most favourable circumstances that
such a service will be successfully accomplished, that is to say,
in the case of a harbour or river defended by submarine mines but
unsupported by guns, or guard boats, or where the electric light is
used.

Numerous methods have been devised from time to time to effect the
destruction of an enemy's submarine defences, among which are the
following:--

1.--Projecting frames, &c., from the bows of a vessel.
2.--Creeping and sweeping by boats.
3.--Countermining.

_Projecting Frames, &c., from the Bows of a Vessel._--This method
was adopted by the Federals during the American civil war of 1861-5,
and in many instances it was the means of saving their ships when
proceeding up rivers which had been torpedoed by the Confederates,
though notwithstanding this precaution several vessels were sunk. The
submarine mines against which this mode of defence was used, were in
nine cases out of ten mechanical ones, and therefore the framework
defence afforded a better means of protection then, than would be the
case now that electrical ground mines and circuit closers are used, as
the framework would catch the circuit closer only, and the vessel would
probably be over the mine when the explosion took place. The Americans
moor their circuit closers in rear of their mines, so that a vessel
fitted with a bow frame or not, coming in contact with the former must
be right over the charge at the instant of explosion.

Against ground electrical mines fired at will, the bow net, &c., is
no protection whatever, still under certain circumstances it would be
found extremely useful.

_Sweeping for Submarine Mines._--This method of clearing a channel of
submarine mines could not possibly be carried out under artillery fire,
but in waters not so defended it would prove of some value.

Where only buoyant mines, or ground mines with circuit closers are
to be cleared away, two or more boats dragging a hawser between them
would be sufficient to discover them, and so lead to their destruction;
but where dummy mines and inverted creepers are moored in addition,
another method of sweeping must be resorted to, viz., that of bringing
an explosive charge of gun-cotton to act on the obstruction grappled,
and thus destroy it. This is effected by lashing a charge to each end
of the sweep, so that whatever is grappled may slide along it, until
caught by hooks, which are attached for this purpose to the centre
of the charge. On grappling an obstruction, the two boats drop their
anchors, one hauling in, the other veering out the sweep, until the
charge is hooked by the obstruction; this being effected, the boats
move out of range, and the charge is fired.

_Creeping for Electrical Cables, &c._--Creeping is the method employed
for picking up the electric cables of the enemy's submarine mines, and
is effected by boats towing an ordinary grappling iron, or specially
prepared creeper on the ground.

In both sweeping and creeping it would be found necessary to employ
a diver, who would ascertain the nature of the grappled obstructions
which could not be easily raised by the boats.

The Lay torpedo boat, which is fully described in the chapter on
offensive torpedoes, is capable of being used for the foregoing
purposes.

_Countermining._--Countermining, that is, the destruction of submarine
mines by the explosion of other mines dropped close to them, will
under certain conditions prove of great use in clearing harbours of
mines. This method could not be operated in waters properly guarded and
swept by artillery fire.

There are two distinct methods of laying out countermines, viz.:--

1.--In a boat, which may be either towed, or hauled out
to its destination, or may be steered, and controlled
by electricity.

2.--By attaching them to buoys so that they are
suspended at the proper depths, and then hauled out by
means of a warp to an anchor which has been previously
placed in position.

Both of the foregoing methods have been successfully manipulated in
practice, the first method, where the boat carrying the countermines is
towed either by a pulling or steam boat being the most practicable one.
A large amount of material would be required for clearing a channel by
means of countermines: for example, if the mines to be attacked require
500-lb. gun-cotton charges to be used, 7-1/2 tons of the explosive,
besides cables, buoys, &c., would be required to clear a passage about
one mile in length and 200 feet in width.

A ship's launch will carry about twelve of these 500-lb. countermines,
with all the gear attached thereto.

Experiments to ascertain the effect of countermining have been carried
out in England and Europe for the last five years, some of which are
given at length in the chapter on "Torpedo Experiments." During the
Turco-Russian war, a portion of the Danube was swept in the ordinary
and most simple manner by the Turks, and five Russian electro contact
buoyant mines were picked up; one other exploded during the process of
dragging it to the surface, but no injury occurred to those at work.

_Destruction of Passive Obstructions._--To clear away booms, or other
passive obstructions, if not possible to cut them away, they may be
destroyed by outrigger boats exploding their torpedoes underneath, and
in contact, or by attaching charges of gun-cotton at intervals, and
then exploding them simultaneously. When a chain is horizontal, and
therefore somewhat taut, a charge of 3-1/2 lbs. of gun-cotton (this
explosive, being the most effective and convenient for such purposes,
should always be used) will be found sufficient to destroy it, no
matter what size, and whether the chain is in or out of the water, the
charge being of course placed in contact with it. Great uncertainty
must always attend the supposed clearance of a channel, or passage
of submarine mines, as was exemplified during the American civil war,
when most of the Northerners' vessels were destroyed while moving over
ground which had been previously carefully dragged, and buoyed, and
this fact, coupled with the tediousness and danger of performing such a
service, proves the enormous value of a system of defence by submarine
mines.

FOOTNOTES:

[Footnote J: 'Electricity and Magnetism,' by Professor F. Jenkins.]

[Footnote K: See Appendix.]

[Footnote L: As constructed by Mr. J. Mathieson, late R.E., at the
Silvertown Telegraph Works, Essex.]

CHAPTER V.

OFFENSIVE TORPEDO WARFARE.

THE term "Torpedo" is applicable more particularly to offensive
submarine mines than to those employed for the purposes of defence, and
therefore by _torpedoes_ will be understood every kind of submarine
explosive weapon designed to be used for active attack against vessels,
&c., no matter how they may be manipulated.

_Offensive Torpedo Warfare still in its Infancy._--Though during the
seventeen or eighteen years that torpedoes have been considered as a
legitimate mode of naval warfare there have occurred three big wars,
in each of which submarine weapons, offensive and defensive, have
played an important part, still the subject of _offensive_ torpedo
warfare must be even now considered as in its infancy, and therefore
any opinions expressed as to the merits and demerits of the various
apparatus in connection therewith can but be based on the theoretical
capabilities of each torpedo, and on the results of experiments carried
out with them during peace time, which latter as a rule are conducted
under far too favourable conditions to be relied upon.

_Their Use during the Civil War in America._--During the American
civil war, the only offensive submarine weapon that was used was
the outrigger or spar torpedo, which in those days was a crude and
imperfect machine, and manoeuvred from boats possessing all the
features which a torpedo boat should _not_ possess. Still under these
unfavourable conditions ships were sunk by such means by both Federals
and Confederates, proving that in future wars this mode of attack,
favoured by the vast and important improvements that have lately been
effected both in connection with the torpedoes and torpedo boats,
should play a prominent part, and prove a most destructive mode of
attack.

_Their Use in the Franco-German and Russo-Turkish Wars._--In the
Franco-German war of 1870-1, offensive torpedo warfare was not
resorted to by either side, the French fleet being deterred from
entering German waters by the submarine mines placed, or at least
supposed to be placed, in position.

From the Russo-Turkish war much light was expected by torpedoists
to be thrown on the subject of torpedo warfare, but alas, little or
nothing was done to settle any of the many vexed questions which exist
in regard to offensive submarine weapons. The torpedo experience of
that struggle tended rather to prove that the vast importance hitherto
attached to torpedo attack was much exaggerated.

One of the causes which led to the failure of offensive submarine
weapons, when employed on active service, seems to be due to the fact
that, owing to the extremely small radius of the destructive effect
of such weapons, it is absolutely necessary for complete success to
explode the mine in actual contact with the attacked vessel; to ensure
which, at night time, in an unknown harbour, with the position of the
vessel attacked somewhat uncertain, and even without the additional
obstacles of guard boats, booms, electric lights, &c., is a service of
infinite difficulty, and one which may easily terminate in a failure.
The foregoing would more especially apply to the spar torpedo attack,
but in an attack with the Whitehead fish, or towing torpedo, there
would be an additional cause of failure, viz., the complicated nature
of their manipulation.

Torpedoes may be divided into four classes, viz.:--

1.--Drifting or floating torpedoes.
2.--Towing torpedoes.
3.--Locomotive torpedoes.
4.--Outrigger or spar torpedoes.

_Drifting or Floating Torpedoes._--By "drifting" or "floating"
torpedoes are meant all those submarine machines which are dependent on
the tide or current of a stream for their action and motion.

During the American civil war this mode of attacking vessels was
constantly employed by the Confederates, and though not successful in
destroying any of the Federal ships, was the means of considerably
hampering the movements of their river flotillas.

Drifting torpedoes might be advantageously used for the destruction of
pontoon bridges, booms, &c., and in this way, had the Turks in their
late war used them, the Russians would have found the crossing of
the Danube a matter of infinite danger and difficulty; in fact, by
a systematic use of such weapons, combined with a little dash on the
part of the Ottoman flotilla on the Danube, that river should have been
to the Russians an impassable barrier. To use these torpedoes most
effectively, especially against a single vessel, a thorough knowledge
of the force and direction of currents should be gained before
proceeding to undertake an operation in which these submarine weapons
are used.

Another point to be remembered is, that if such a torpedo were started
with the flood, for example, towards an enemy, and did not explode,
there would be a chance of its being returned to the starting-place by
the ebb tide.

In this class the following torpedoes seem the most practicable:--

1.--Lewis's drifting torpedo.
2.--McEvoy's drifting torpedo.
3.--American extempore drifting torpedo.

_Description of Lewis's Drifting Torpedo._--"Lewis's" drifting torpedo,
designed for the express purpose of destroying booms or other floating
obstructions placed round a vessel at anchor for the purposes of
defence, is shown at Fig. 101. It consists of a box _a_, containing the
charge and fitted with several detonating fuzes. This box is attached
to one side of a beam _b_, and within 6 inches of one extremity, the
beam being about 20 feet long and 7 inches square; to the opposite
side, of the same end of the beam _b_ a heavy weight _c_, resting in
a shoe _d_, is attached by a long iron rod _e_, which reaches to the
other extremity of the beam, and is there connected to a bell-crank
lever and spring _f_, a pressure on which detaches the weight _c_; a
chain _g_, 18 feet long, connects the weight loosely with the upper
end of the beam, and another chain _h_, 9 feet 6 inches long, connects
it with a point more than 2 feet below the centre of the beam. The
apparatus is so constructed that it floats nearly vertical with the top
of the beam just above the surface of the water.

On the machine drifting against the boom or other obstruction, the
spring or lever _f_ at the upper extremity is pressed down, thus
releasing the weight _c_, which falling, becomes suspended by the two
chains _g_ and _h_, and brings the beam into an inclined position. The
weight of this mass of iron and the chain suspending it are suddenly
brought to bear on the top of the beam, dragging it under water and
clear of the boom, &c. At the same time the lower end, released from
the weight, rises, and the whole apparatus is carried forward by the
current against the side of the vessel, on striking which the torpedo
is exploded.

_Description of McEvoy's Drifting Torpedo._--"McEvoy's" drifting
torpedo is intended to be floated, singly or in groups, by the aid of
tides or currents against vessels at anchor, bridges, &c.

At Fig. 102 is shown a plan of this form of drifting torpedo.

It consists of the body of the torpedo _a_, which contains the charge,
at the side of which is placed the loading hole _b_; _c_ is the tube
containing the priming charge; _d_ is the framework surrounding and
protecting the wheel or screw _e_; _f_ is the fuze pillar, in the
centre of which is a steel rod _g_, and on the top a thin steel plate
_h_ is placed; _i_ is the nipple for the percussion cap; _k_ is a
horizontal bar, turning and resting on top of the fuze pillar _f_; _m_
is the lever for supporting the hammer _n_ when it is set; _l_ is the
screw barrel supporting the wheel or screw _e_; _o_ is a safety pin;
_q_ is the supporting chain, and _p_ the spring for working the hammer
_n_.

By means of a buoy or log of wood, from which the torpedo is suspended,
it can be adjusted so that the explosion shall occur at the requisite
depth.

To prepare the torpedo for use, unscrew the fuze pillar _f_, take off
the horizontal bar _k_, place a percussion cup on the nipple _i_, and
screw it tightly against the end of the steel rod _g_. The fuze pillar
is then ready for use, and should be screwed into the body _a_. Then
fill the torpedo with the explosive and close the loading hole _b_. The
hammer _n_ is then set by drawing it back and bringing the end of the
lever _m_ against it, at the same time running the screw barrel _l_
under the lever _m_, so that its end catches the screw of the barrel,
as shown in the figure. The safety pin _o_ is then put in its place and
secured by a few parts of thread, which by a sharp jerk on the safety
line will be easily broken.

[Illustration: DRIFTING TORPEDOES.

PLATE XXIX]

The horizontal lever _k_, which carries the lever _m_ and propeller
_e_, rotates on the top of the fuze pillar _f_, and is prevented from
rising by means of a screw. The torpedo being let go, the safety pin
_o_ is pulled out by means of a line which is attached to it. The
propeller will not revolve whilst the torpedo is drifting with the
current, but the instant it is stopped by the action of the current
the wheel will be caused to revolve, and after a few revolutions it
will unscrew the barrel from under the end of the lever _k_, and
the latter, dropping the hammer _n_, will be forced by the spring _p_
into contact with the thin steel plate _h_ on the top of the fuze
pillar, which blow is transmitted by means of the steel rod _g_ to the
percussion cap, and the torpedo exploded.

_American Extempore Drifting Torpedo._--This form of drifting torpedo,
which is readily made, was used in great numbers by the Confederates,
and though not successful in sinking any Federal ships, caused their
vessels considerable annoyance and delay.

At Fig. 103 is shown a sketch of this torpedo. It consists of a tin
case containing about 70 lbs. of powder. A stiff wire _a_, _b_ passes
through a hole punctured in a strip of tin _c_, and a stuffing box _d_;
the end _a_ of the wire is covered with fulminate, and so arranged
that the friction caused by its passage through the strip of tin _c_
will ignite it; a number of wires lead from _b_ to pieces of driftwood
on the surface _e_, _e_, _e_, and the case is supported at the proper
depth by a line attached to a section of log.

_Towing Torpedoes._--By towing torpedoes are meant those submarine
machines which are so shaped and arranged, that when towed from a ship
or boat in motion they will diverge to a considerable extent, thus
enabling the towing vessel to pass clear of the ship attacked, and yet
near enough to allow of the torpedo being brought in contact with some
part or other of her hull.

Towing torpedoes were for the first time employed on actual service
during the late Russo-Turkish war, when a modified form of the
well-known Harvey torpedo, designed by a German officer, was used by
the Russians, but in no case was it successful.

In this class of submarine offensive machines may be placed the
following:--

1.--Harvey's towing torpedo.
2.--Menzing's towing torpedo.
3.--The French towing torpedo.

_Harvey's Torpedo._--This form of towing torpedo was invented
conjointly by Captain John Harvey and Commander Frederick Harvey,
R.N., and is intended to be used at sea both as a means of offence and
defence.

At Fig. 104 is shown in elevation the small sized Harvey towing
torpedo, in which all the latest improvements that have been devised
are represented.

_a_ is the case of the torpedo, formed of Muntz's metal, but not
provided, as the original ones were, with an exterior case of wood; by
this alteration greater capacity combined with extreme lightness is
obtained, which undoubtedly much enhances the value of the small size
torpedo which is intended to be carried by and manoeuvred from boats;
_b_ is the principal or after lever, hinged on the top of torpedo at
_c_, and rests, when ready for action, in a crutch formed in the top of
the exploding bolt _d_; _e_ is the foremost lever, hinged at _f_, and
kept in position on the after lever _b_ by a groove formed in it and a
lashing which passes through a slot in the principal lever, as at _g_;
_h_ is the side lever, pivoted at _i_, and exerting a pressure on the
firing bolt _d_ by means of a lanyard which is passed through the bolt
_k_ and over the principal lever _b_; _l_ is the top lever, pivoted
at _m_, and exerting a pressure on the bolt _d_ by means of a lanyard
which is passed through the bolt _n_ and over the principal lever _b_;
this top lever _l_ has been added to ensure the action of the torpedo,
on its striking sideways against a vessel; _o_ and _t_ are handles, to
the former of which the lashings of the levers _h_ and _l_ are secured;
_p_ is the ring used for attaching the buoy rope; _r_, _r_ are two
loading holes, made in the side of the torpedo case, by which a charge
of gun-cotton may be quickly and efficiently stowed; this also is a new
feature in the small size torpedo; _s_ is the rudder formed for the
purpose of controlling the direction of the torpedo when the tow line
is suddenly slacked.

In regard to the large size torpedo, the construction of the case
remains as in the original ones, the improvements being, the
enlargement of the loading and fuze holes, and the addition of the top
lever _l_, as shown at Fig. 104.

The small size torpedo is capable of holding 47 lbs. of water, whilst
the large size one will contain 76 lbs. of water, or about 33 lbs. and
58 lbs. of gun-cotton respectively.

The slings are made of best Italian hemp, and consist of a span of
four legs, which are secured to lugs at the corners of the torpedo and
connected to an iron thimble, which is shown at Fig. 105; this thimble
is made suitable for either wire or hemp rope, and is so arranged that
should the seizing become slack, the parts of the slings cannot become
detached from the thimble.

[Illustration: HARVEY'S TOWING TORPEDO.

PLATE XXX]

The legs of the slings should be so fitted that when stretched
alongside the torpedo they extend 1 foot beyond the stem for the
large torpedo and 8 inches for the small one; the four legs should be
so fitted that when an equal strain is brought on them, the thimble
should be on a level with the upper lugs, and the upper fore span form
an angle of 80° to 85° with the side of the torpedo; this is shown at
Fig. 106. This arrangement gives the best divergence with the least
strain on the tow rope, and is suitable when the torpedo is kept at
short scope, as well as when a long length of tow line is out.

The mode of attaching the foremost and side levers is shown at Fig.
107. Before reeving the lanyards they should be well greased in the
wake of the fair leads, but not where they are made fast. The lanyards
should be made up like a reef point. Care should be taken that the
short arm of the side lever _h_ is brought close into the fair lead,
and its lanyard should be set up sufficiently taut to give a slight
spring in the principal lever _b_ by the strain thus brought on it.
This lever _b_ has a steel fish on the top, in order to prevent it
taking a permanent bend. If the side lever lanyard is properly set up,
the bolt will spring down about 1/8th of an inch when the safety key is
withdrawn, owing to the spring in the lever, and the shrinking of the
lanyard; this brings the muzzle 1/8th of an inch nearer the pin without
disturbing the side lever.

The bolt is so arranged that the torpedo can be fired by either of the
following methods:--

1.--Mechanically.
2.--Electrically at will.
3.--Electrically on contact or at will.

_Mechanically._--In this case the bottom of the inner cylinder, as at
_a_, Fig. 108, is fitted with the ordinary mechanical chemical fuze,
ignition being effected by the breaking of the glass vessel containing
the sulphuric acid on being forced into contact with the needle _n_, by
the action of the levers on the torpedo striking a vessel.

_Electrically at Will._--For this purpose a platinum wire fuze is used,
one terminal being connected to earth through the bolt, the other to a
wire leading up through the core of the bolt, and connected by means of
an ebonite joint with a single cored electrical cable leading from the
torpedo vessel.

_Electrically on Contact, or at Will._--In this case, a resistance
coil is inserted in addition to the fuze, and is so arranged that on
the bolt being forced down a short circuit is formed, cutting out the
resistance coil (about 20 ohms), and thus enabling the battery to fire
the fuze, which, owing to the 20 ohms resistance in the circuit, it was
previously unable to effect. Should the bolt so arranged be required to
be fired at will, it is only necessary to put a more powerful battery
in circuit, and so fire the fuze through the 20 ohms resistance.

_Exploding Bolt._--The exploding bolt is fitted to act with a pressure
of from 30 to 40 lbs. on its head for the large size torpedo, and from
15 to 20 lbs. for the small size one.

The bolts are all the same size, and differ only in the direction
of the slot for the safety key _k_, being port or starboard bolts
accordingly. The muzzle of the exploding bolt stands 1 inch off the pin
when in the safety position, that is, when the safety key rests on the
brass work of the priming case.

The safety key is secured in the slot of the exploding bolt, as shown
at Fig. 108, by eight or nine parts of strong whitey-brown thread
secured to the key, passed round the bolt, and securely knotted; the
parts of the thread should come away with the key, in order that none
of the parts may be worked down the tube by the exploding bolt.

In the event of the large torpedo being cut away in deep water after
the withdrawal of the safety key, it will explode by pressure on the
head of the bolt at about sixty fathoms depth; the small one at about
thirty fathoms.

_Buoys._--The buoys are of two sizes, and are made of solid cork
(such cork only being used as will ensure great floating power after
being immersed for a time); each buoy is built upon a galvanised iron
tube running longitudinally through; on the ends of the tube are
screwed wooden cones, which bind all together, and render the buoy
indestructible.

Two buoys are used for each torpedo, the larger buoys for the large
size torpedo, and the smaller buoys for the small size torpedo. The
buoy rope is of hemp, about five or six fathoms in length and two
inches in circumference, an eye being spliced in the end nearest the
torpedo; to this eye is bent the tow rope, with a single or double
sheet bend forming the knot by which the torpedo is towed; the other
end of the buoy rope is passed through one of the rings in the stern
end of the torpedo (according to whether working in deep or shallow
water), then through the tube of the first buoy, and an overhand knot
made in the rear; then through the next buoy, and a knot in the rear
of that. Recently, Captain Harvey has adopted a large and a small buoy
for each torpedo, the large one being practically sufficient, the
smaller one being added in the event of the other one becoming sodden.

_Brakes._--The brakes are used for the purpose of controlling the tow
ropes; they can be fixed by screws into the deck at the most convenient
place for command, and in a properly constructed torpedo vessel would
be placed below the water line, to prevent exposure of the men working
them. They are so arranged as to admit of the tow rope being quickly
veered, and at the same time are sufficiently powerful to bring the
torpedo to the surface when required. Success greatly depends on the
skilful handling of these brakes, for in conjunction with the cork
buoys they give the operator command of the depth at which the enemy
is to be struck. Unless a very high rate of speed is required, one
handspike will control the tow rope; the other strap can be thrown off
the drum, and the handspike allowed to lie on the deck ready to be
thrown into gear, if necessary. The surface of the drum in contact with
the strap should be powdered with rosin to increase the friction. The
tow rope should be so reeled up that in veering the reel may revolve
towards the men at the handspike. The spindle will contain several tow
ropes, that, in the event of one torpedo being cut away, another can be
immediately bent.

The brake for small torpedo requires only one drum and handspike. It
can be fitted to a steam launch by placing an extra thwart across near
one of the others.

Care should be taken that the riding turns lie fairly over each other,
to prevent a jamb when veering.

The brakes, both large and small, are so made as to ensure durability,
they being considered a part of the ship's furniture.

Brake for safety key line is a small reel on the same principle. When
going a slow speed, it may not be necessary, as the safety key line
can be attended by hand; but when going ten or eleven knots, it will
be found of considerable advantage, both in keeping the bight of the
safety key line from dragging astern, thereby lessening the divergence
of the torpedo, and also in drawing the safety key when a strong stop
is used.

_Arrangements for Launching and Towing the Torpedoes._--A yard across
either the main or mizen mast of a torpedo vessel, from 20 to 25 feet
above the water line, is a very convenient method for launching and
towing. The leading block on the yard, through which the tow rope is
rove, may be fitted to a traveller on the yard with an inhaul and
outhaul, that the distance out from the ship's side may be regulated as
convenient.

In a large vessel, the leading block for tow rope can be fixed to
the end of the quarter-boat's davits. The brakes for commanding the
tow rope should be screwed firmly to the deck. In a vessel properly
constructed for the service, they would be on the lower deck, the tow
rope having been led along the yard, and down each side of the mast.

A leading block for the tow rope is placed on the deck by span or bolt
a few feet in front of the brake. The safety key reel, if used, must
be fixed in a convenient position on deck, that the man attending it
can see how to control it; in a properly constructed vessel he would be
in the pilot house. The safety key line leads through a small leading
block on the ensign staff or some convenient point abaft the lead of
the tow rope, 15 to 20 feet above the water. The leading block on
the yard may be fitted with a lizard, if thought necessary. A sharp
instrument should be kept by the brakes ready to sever the tow rope.

In large men of war, arrangements are made for carrying a loaded
torpedo and two buoys in a convenient position on each side of the
vessel, in such a manner that the tow line can be bent, the exploding
bolt screwed in, the levers adjusted, and the torpedoes and buoys
dropped simultaneously when required.

_Preparing the Torpedoes for Use._--The torpedoes, port and starboard,
loaded and ballasted, having been hoisted out of the torpedo room, are
placed on the deck on their own sides, with their heads forward under
the leading block, and the buoys placed abaft them and strung together;
the exploding bolts are now entered into the torpedoes, and forced down
until their safety keys rest on the brass work, taking care that each
safety key points in the direction of the eye through which its lanyard
has to pass; the levers are now secured by their lanyards, as explained
at pages 120 and 121. The eye at the end of the buoy rope is now rove
through the large or small ring in the stern end of the torpedo. The
tow rope having been previously rove through the leading block on the
deck and on the yard, is rove through the thimble of the slings from
forward aft, and bent, with a single or double sheet bend, to the
eye of the buoy rope. The safety key line having been previously rove
through the leading block on the ensign staff, and the lanyard on the
safety key having been led through the eye of the handle, making a fair
lead with the slit in the bolt, are bent together with a double sheet
bend, and stopped to the eye of the handle by a split yarn of suitable
strength, the yarn having been first secured to the line by a round
turn outside the bend.

The line should also be stopped with another split yarn round all parts
of the slings close up to the thimble, having first made an overhand
knot in the line at a distance a few inches longer than that between
the eye bolt and the thimble.

The crew having been stationed at their respective posts, the handles
having been shipped on the tow reel, the tow line is then reeled up
until the torpedo will launch clear, and swing out under the leading
block on the yard. Hold the torpedo by the handspikes, and take off the
handles of the brake. In swinging out, care should be taken that in
starting from the deck the fore slings do not foul the fore top lever.
The stern of the torpedo can be steadied by keeping a slight strain on
the buoy rope. The safety key line must be kept clear, and not checked,
or it might break the stop and draw out the key before intended. The
buoys must be placed in a proper position and hands stationed by them
to launch them overboard the instant the torpedo takes the water. It
would be better to stop the screw, if circumstances would allow of it,
when lowering the torpedo and buoys into the water, to prevent the
chance of the buoys fouling the screw. The torpedo, on reaching the
water, will _immediately_ diverge clear of the ship; the buoys being
launched, as the strain comes on the buoy rope, they will be towed
clear away from the screw, and full speed may be put on at once. The
men at the handspikes must veer steadily, occasionally checking the
torpedo, that it may be kept near the surface, and not allowed to dive,
which it will do if the tow rope is slacked up altogether, and then a
sudden strain brought on it.

Eventually it will come to the surface, when the bow is pointed up
by the strain on the tow rope; greater the speed the more quickly
will it be brought to the surface. In shallow water this should be
particularly attended to, as in diving it might strike the bottom and
injure the levers, and, if the safety key has been withdrawn, explode;
moreover, it brings an undue strain on the tow rope. The torpedo can
now be gradually veered out to the distance required, the safety key
line so attended that a sufficient strain is kept on it as not to
allow of a long bight of line dragging astern of the torpedo; at the
same time having due regard to the strength of the yarn by which the
line is stopped to the handle of the torpedo. The distance veered must
depend upon the nature of attack. The tow line should be marked with
knots every 10 fathoms: under some circumstances the torpedo would be
close to the ship until passing the enemy; at other times veered to 40
fathoms it will be found most suitable.

The full divergence of 45° is obtained up to 50 fathoms; beyond that
the bight of the tow rope in the water drags the torpedo astern, unless
the tow rope is triced much higher up, which has its disadvantage;
40 to 50 fathoms of tow rope gives the best command of the torpedo,
veering 2 or 3 fathoms of tow line suddenly will always sink the
torpedo some feet below the surface. Should it become necessary to use
the torpedoes with a stern board, they can be so used, but in this case
the port torpedo is used on the starboard, bow and starboard on the
port; all other arrangements being exactly the same. In rough weather,
advantage should be taken of the roll, and the torpedo allowed to swing
out from the yard, and be let go by the run, checking the tow rope
immediately the torpedo is in the water. It is not absolutely necessary
to ease the vessel when launching; the torpedo can be launched at full
speed. In the event of its being found necessary to cut adrift the
torpedo, in consequence of coming suddenly across a friendly vessel,
the tow rope should be cut near the brake, and if the buoy rope has
been rove through the large stern ring, the torpedo will sink and be
lost, the buoy only remaining. If the buoy rope has been rove through
the small stern ring, the torpedo will be suspended by the buoy rope;
and should the safety key not have been withdrawn, can be recovered
with safety.

In the event of wishing to recover it when the buoy rope has been rove
through the large ring, a toggle must be lashed on the tow rope abaft
the leading block on the yard, when it can be recovered by the buoy
rope; as a general rule, however, it will be found best to expend the
torpedo, and not attempt its recovery.

[Illustration: HARVEY'S TOWING TORPEDO.

PLATE XXXI]

[Illustration: SYSTEMS OF ATTACK WITH HARVEY'S TOWING TORPEDO.

PLATE XXXII]

_Recovering the Torpedo._--Should the safety key have been withdrawn,
great caution is necessary. Tongs, shown at Fig. 109, for going round
the upper part of the bolt, to take the place of the safety key,
when once clasped and secured round the bolt, render the torpedo
safe to handle; this could only be done from a boat. With the safety
key in, there is no danger in hoisting it inboard again by its own tow
rope, and hoisting up the buoys at the same time with a grapnel.

_Different Methods of Using the Torpedo._--There are two methods of
employing the torpedo, either of which may be adopted, according to
circumstances.

1.--When it is towed with a length of line varying from
25 to 60 fathoms, and dipped when in position to strike
the attacked vessel.

2.--When it is kept suspended from the yard, &c., and
dropped at the spot, where according to the first
method it would have been dipped.

In the first method, it is not necessary to withdraw the safety key
till just before dipping; in the second method the safety key line is
belayed at about twenty fathoms, and the key withdrawn when the line is
tautened by the ship going ahead.

_Tactics._--Description of the various attacks that may be made with
the Harvey torpedo against a ship at anchor or under way. In the
following diagrams _T_ is the torpedo vessel, _S_ the ship attacked.

[Illustration]

...... The track.
------ The tow rope.
O-o-o The torpedo.

_Attacking a Vessel moored Head and Stern._--In this case the torpedo
vessel steers in for the bow or quarter of the vessel attacked,
according to the direction of the current, and on the side approached
launches the torpedo between the moorings, as at _A_; leaving the tow
rope slack, the torpedo vessel proceeds ahead or astern against the
current, and when at a sufficient distance off, the tow rope is held
fast, which will cause the torpedo to diverge into contact with the
vessel attacked, as shown by Fig. 110.

_Attacking a Vessel at Anchor by Crossing her Bow._--In this case
the torpedo is sufficiently diverged when near to the vessel with a
good scope of tow rope out. After having crossed her bow, proceeding
onwards, the tow rope will be brought obliquely across her cable, and
the torpedo will swing into her, as shown at Fig. 111. It may be here
remarked, that in all cases the depth of the explosion can be obtained
by the sudden slacking of the tow rope; and the tow rope once under
the keel, causes the torpedo to be hauled down near to it before
exploding.

_Attacking a Vessel at Anchor by coming up from Astern on either
Side._--In this case the torpedo is launched when on the quarter of the
vessel attacked, as at _A_, the tow rope left slack. After steaming
ahead some distance, hold fast the tow rope, when, by continuing to
steam on, the torpedo will diverge into contact with the bottom of the
vessel attacked, as shown at Fig. 112. _When skilfully performed_,
the total destruction of the enemy is certain, since the torpedo is
springing from a depth to the surface, and will, in consequence, strike
near her keel. The torpedo vessel can pass at her greatest speed, and,
if thought necessary, near enough to clear away any of the ordinary
obstructions, such as booms, nets, &c.

_Passing Down between Two Lines of Vessels at Anchor._--In this case it
would be impossible to fire at the torpedo vessel, for fear of injury
to their friends. Two or more torpedo vessels following each other with
preconcerted signals would cause great destruction. See Fig. 113.

_Attacking a Vessel in Motion from Right Ahead._--In this case two
torpedoes are launched, port and starboard, each diverging to its full
extent; when passing the vessel attacked, one or the other of the tow
ropes is brought across the cut-water, and by the simultaneous motion
of the two vessels in opposite directions, the torpedo is brought
alongside of or under the bottom of the vessel attacked, as shown at
Fig. 114. The torpedo vessel should keep the masts of her enemy in
one until close to, when either torpedo will be used, according to
the movement of the enemy. At the time of the tow rope taking the
cut-water, the brake is suddenly eased up; the tow rope will then pass
under the bottom, when by checking the tow rope the torpedo will be
hauled under the bottom.

To execute this attack, judgment, skill, and nerve of the highest order
will be required, as the risk of being run down will be imminent.

_The Attack from Astern._--In this case two torpedoes are launched, and
diverged as in the previous case; it is assumed in this instance that
the torpedo vessel can outspeed the vessel attacked, which will enable
her to bring a torpedo under the run of the attacked vessel, as shown
at Fig. 115.

[Illustration: SYSTEMS OF ATTACK WITH HARVEY'S TOWING TORPEDO.

PLATE XXXIII]

[Illustration: SYSTEMS OF ATTACK WITH HARVEY'S TOWING TORPEDO.

PLATE XXXIV]

_If Chased by a Hostile Vessel, and unable to Face her._--In this case
veer a torpedo astern, having first obtained a position a little on
the bow of the chasing vessel. When it is known by the length
of the tow rope out that the torpedo is about abreast of her bow,
hold fast the tow rope, which will cause the torpedo to diverge, and
be brought into contact, as shown at Fig. 116. As a last resort drop
spanned torpedoes.

Torpedoes can be used with a stern board, if necessary. The port
torpedo, in this case, will be launched on the starboard side, and the
starboard on the port side.

It should be here remarked that, although great speed is essential in
the torpedo vessel to come up with the enemy and choose an advantageous
position, it is not advisable to tow the torpedoes, if it can be
avoided, at a greater speed than 11 knots; because the strain brought
upon the towing gear is excessive, and the torpedo would require a
large addition of ballast to keep it sufficiently immersed to attain
the full divergence.

There is, however, one style of attack in which the highest speed can
be maintained, viz. by dropping the torpedo alongside in passing.

This mode of attack is one of the best, particularly under cover of
darkness, against a ship at anchor.

The position of the torpedo is known, and the tow line is never in
contact with the enemy during the operation; a skilled hand at the
brakes is all that is required, the vessel keeping a straight course at
the highest speed, passing as close as possible to the enemy, in order
to clear away all obstructions. The tow rope must not be checked by the
brake too suddenly.

_Defensive Purposes._--The Harvey torpedo may be used as a means of
defence by large ships against a torpedo vessel attacking with that
species of submarine weapon, as the latter would be forced to pass
outside the former vessel's torpedo, and thus decrease the chance of
a successful dip. Again, in the case of an attack by the ram, these
torpedoes afford some protection, as a deterrent.

_Night time._--Though a dark night and tempestuous are favourable to a
surprise, yet in the case of a Harvey torpedo attack it is essential
that the weapon should be seen to dip it at the proper time, therefore
daylight is necessary to this species of torpedo attack.

_Value of the Harvey Torpedo._--The Harvey torpedo is undoubtedly of
considerable value when _ably handled_, yet the skill and judgment
required is very great, and can only be acquired by _constant_
practice.

_Description of the Menzing Towing Torpedo._--This modified form of the
Harvey towing torpedo was designed by Captain Menzing, of the German
navy, to remedy what is considered by the Germans as the chief defect
of that weapon, viz. its liability to injure friendly vessels, and also
to do away with the necessity of using two torpedoes, one for each side
of a ship.

At Fig. 117 is shown a plan and elevation of this towing torpedo.
_a_ is the body of the torpedo, somewhat similar to the Harvey, but
narrower at the stern, and bevelled on both sides towards the bow; _b_
is an iron frame placed in the bow, capable of being turned either to
the right or left; _c_ is the hole for the introduction of the fuze,
and _d_ is the loading hole; _e_ is a rudder placed at the stern of the
torpedo; _f_, _f_ are levers, by pressure against which the torpedo
may be fired mechanically, or electrically at will; these levers are
connected to a block of wood fitted with stops to prevent them being
pushed too far over; _s_ and _p_ are two towing ropes, one on each side
of the torpedo, which pass from its stern through the point of the
frame _b_, and thence to the vessel, these are also connected to the
rudder _e_ in such a manner that on either of the ropes _s_ and _p_
being tautened the rudder _e_ is turned in the opposite direction; _w_
is an electric cable, strong enough to bear the whole pressure of the
torpedo when being towed right aft.

To diverge the torpedo on the starboard quarter of the ship, the line
_s_ must be slackened, and the whole towing strain brought on the rope
_p_, causing the frame _b_ to be pulled over to a knot _k_ in the
rope _p_, made at the proper position to ensure the torpedo towing at
the correct angle from the course of the vessel, and at the same time
causing the rudder _e_ to be turned to starboard; this is shown at Fig.
117 by the dotted lines.

To diverge the torpedo on the port quarter, the towing rope _p_ would
be slackened and the whole strain brought on the rope _s_, and an
action opposite to that already described would be the result.

Two cork buoys are used, similar to those employed with the Harvey
torpedo; one being attached at a distance of 10 feet from the stern of
the torpedo, and the other at such a distance astern that the torpedo
would be placed at a distance below the surface to allow of safety to a
friendly vessel.

[Illustration: GERMAN AND FRENCH TOWING TORPEDOES.

PLATE XXXV]

The torpedo is manipulated in a similar manner to the Harvey, the
circuit being closed at the moment of the first buoy disappearing, at
which time the torpedo would be about ten feet below the surface. The
two buoys are together capable of supporting the torpedo, and thus by
means of the second one it may be picked up, should it be necessary to
cut the towing ropes.

_Description of the French Towing Torpedo._--The towing torpedo used by
the French is represented in section and plan at Fig. 118.

_a_ is the body of the torpedo, formed of wood enclosed in a thin steel
case; _b_ is the head made of cork; _c_ is the case containing the
charge, which is generally 33 lbs. of dynamite, this case is supported
by the bolt _d_ resting on the plate _e_; _f_, _f_ are whiskers, which
are connected to the plate _e_; _g_ and _h_ are hollow tubes, one end
of _g_ being attached to the case _e_, and one end of _h_ to the rear
end of the body of the torpedo _a_, and they are so arranged that when
the case _c_ is released, its weight will draw out the tube _g_, which
slides along the tube _h_ to nearly the full extent of the latter; _k_,
_k_ are bolts, to which the towing sling is attached; _l_ is the fuze,
and _n_ is a small gun used for firing the torpedo at will. The hole
in the plate _e_ through which the bolt _d_ passes is larger than the
latter, so that when the plate is moved backwards by pressure being
applied to the whiskers the bolt is freed from support, and case _c_
attached to it falls.

The modes of firing are as follows:--

1.--The automatic plan of firing is effected by the
tube _h_, after it has fallen a certain distance,
corresponding to a depth of 9 feet for the case _c_,
drawing down by means of a line attached to it a plug
contained in the body _a_, which completes the circuit
of the firing battery.

2.--The plan of releasing the charge at will is
effected by means of the small gun _n_, which is fired
by electricity, and by its firing forces back the plate
_e_, thus releasing the charge, which is then exploded,
as previously explained.

_Locomotive Torpedoes._--By "Locomotive" torpedoes are meant those that
possess within themselves the power to move through the water, when
once started in a given direction.

Of this species of submarine weapons, the following are the most
efficient and are the ones most generally used:--

1.--The Whitehead fish torpedo.

2.--The Lay torpedo.

_Invention and Adoption of the Fish Torpedo._--The idea developed by
the fish torpedo is due to an Austrian marine artillery officer, who
is now dead. In 1864, Mr. Robert Whitehead, then superintendent of
iron works at Fiume, acting upon the suggestions of a Captain Lupuis
of the Austrian army, commenced a series of experiments to ascertain
the practical value of the above idea, the result being a fish torpedo,
commonly called "The Whitehead," which though far inferior to the fish
torpedo of the present day, was then considered to be a fearful and
wonderful weapon.

The Austrians were the first to purchase this weapon, and two years
later, in 1870, Mr. Whitehead came to England, and prosecuted numerous
experiments with his fish torpedo under the supervision of several
English officers, and on the 8th of October of the same year he
succeeded in completely destroying an old hulk moored at the mouth of
the Medway. The fairly successful results of these experiments induced
the English government to purchase the secret and several of Mr.
Whitehead's fish torpedoes, under the following conditions:--

1.--The right of manufacturing them in England.

2.--To be kept fully informed of all improvements, as
soon as made.

3.--The right of using all such improvements.

And the total amount paid to Mr. K. Whitehead at that time was the
sum of seventeen thousand five hundred pounds, which did not include
the sum of two thousand five hundred pounds claimed for the expenses
attendant on the Medway experiments. Since then a large number of
Whitehead's fish torpedoes have been purchased from time to time,
especially during the Turco-Russian war, when some two hundred were
ordered, also great numbers have been manufactured at Woolwich. The
English fish torpedo, as far as can be ascertained, is a vastly
superior weapon to the Whitehead fish torpedo, possessing as it does
increased speed, and therefore far greater accuracy.

Besides Austria and England, nearly all the European governments have
purchased the Whitehead secret and torpedoes, but in the case of some
of them, the last two clauses of the English conditions of purchase
were omitted.

[Illustration: WHITEHEAD'S FISH TORPEDO.

PLATE XXXVI]

The Turkish is the only government that has obtained the Whitehead
secret and torpedoes without paying for it. This was managed as
follows:--

"On the night of the 20th of December, 1877, the Russians made an
attack with Whitehead torpedoes on an Ottoman squadron lying in the
harbour of Batoum, but owing to a want of practical knowledge of the
manipulation of such weapons, no vessels were sunk or damaged, but two
fish torpedoes, one in perfect condition, were found the next morning
high and dry on the beach at that place."

The American government have up to the present time not sanctioned
the purchase of the costly Whitehead torpedo, preferring their own
locomotive torpedo, which will be fully described further on. On a
government purchasing the fish torpedo, a certain number of their
naval or military officers are sent to Fiume in Austria, where Mr. R.
Whitehead's manufactories are situated, and where the necessary very
exhaustive experiments with his torpedoes are carried out, and are
there thoroughly instructed in the manipulation of these machines, and
are also supplied with a double set of drawings of the various parts of
the torpedo. These officers, and all others whom it may be necessary to
initiate into the mysteries of the Whitehead secret, are bound on their
honour not to divulge it.

_Employment of Fish Torpedoes in War._--The fish torpedo has been
employed on actual service on three known occasions only, in two of
which it failed to fulfil its deadly mission.

On the 29th of May, 1877, a Whitehead fish torpedo was fired by H.M.S.
_Shah_ against the Peruvian ironclad _Huascar_, but failed to strike
her, owing to the latter vessel altering her course at the moment of
the torpedo being discharged. The next instance of the employment of
the Whitehead torpedo was that one mentioned at page 132. The last
and only successful attempt yet made occurred on the 26th of January,
1878, when the Russian steamer _Constantine_ fired a Whitehead
torpedo against a Turkish guard vessel off the harbour of Batoum, and
completely destroyed her.

_Description of Torpedo._--A general view of the Whitehead fish torpedo
is shown at Fig. 119. It is divided into three parts, connected
together by screws.

1.--The charge chamber.

2.--The adjustment chamber, in which is placed what is
known as the secret.

3.--The air and engine chamber.

Vertical and horizontal steel fins are fitted for the purpose of
maintaining the torpedo in an upright position whilst passing through
the discharge tube, or frame; the former fins run nearly the whole
length of the weapon, while the latter are considerably shorter. The
motive power of the torpedo is compressed air, forced by means of a
powerful steam air compressing pump into a portion of the steel chamber
(3) at a tension of upwards of 1000 pounds to the square inch, which
is equivalent to about sixty atmospheres, and which by means of a set
of small three cylinder Brotherhood engines, contained in the steel
chamber (3), drives two screw propellers. These engines are capable
of exerting a force of forty indicated horses, and yet only weigh
about thirty-five pounds, from which it will be understood that to
attain these results the workmanship and materials employed in their
manufacture are of the very highest order and fineness.

The torpedo is made of various sizes, ranging from 14' long and 14"
maximum diameter to 19' long and 16" maximum diameter.

_Capabilities of the Fish Torpedo._--The capabilities of the fish
torpedo are as follows:--

1.--If adjusted for a certain depth, from 5 to 15 feet,
and projected from above water, or if started from the
surface, or if discharged from a submerged tube, it
will rapidly attain that depth, and maintain it during
the run.

2.--If fired in still water, it will make a straight
run in the line of projection, provided that an
allowance has been made for the deflection due to
transverse currents.

3.--It can be adjusted to stop after having run any
distance up to its extreme range, and after stopping to
sink, float, or explode.

4.--Its range and speed vary considerably, according to
the pattern of the torpedo.

Pressure of air in engines varies for distance and
speed from 40 atmospheres to 140 atmospheres.

_Placing the Charge._--The explosive is generally placed in what is
termed the cartridge case, which case is similar in shape to the
interior of the charge chamber (1), and is fixed thereto by means of
wooden wedges.

_Ignition._--The method of ignition is mechanical, and is arranged as
follows:--Extending from the nose of the torpedo to the cartridge case
is a tube terminating in a copper case, in which is placed the priming
charge and detonating composition; within this tube is a steel rod
some 2 feet long, fitted with a needle point at its inner end, and its
outer end screwed into a frame; this frame is capable of moving in and
out, and is connected with a spiral spring which tends to force it, and
consequently the steel rod, or striker, inwards. By compressing this
spiral spring, the inner end of the frame is butted against a catch,
by which it is prevented from acting. On this catch being released,
no matter by what means, the spring is brought into action and forces
the frame and steel striker inwards, the needle point of the latter
coming into contact with the detonator fires the priming charge, and so
explodes the torpedo. The foremost extremity of the torpedo, which is
termed the nose piece, is so fitted that it is capable of being forced
inwards, but in a position of rest its inner edge is just clear of
the catch. On a pressure being brought on the nose piece in a direct
line with the length of the torpedo, it will be forced inwards, the
result being the releasing of the catch and explosion of the torpedo.
In addition to the nose piece, horizontal and vertical levers, or
whiskers, may also be used, a slight pressure on either of which
will similarly effect the explosion of the torpedo; also cutters for
penetrating nets, &c., are fitted to the nose piece when desired.

_Safety Wedge and Key._--For safety purposes a wedge is employed, which
when in the safety position prevents the catch from acting; this wedge
is so arranged that it may be withdrawn by the action of the machinery
after the torpedo has run a certain distance, and also may be replaced
by similar means in the safety position on the completion of the run.
As an additional precaution a safety key is used, which is inserted in
the head of the torpedo through the spring of the frame.

_Description of Adjustment Apparatus._--For adjusting the length
of range for withdrawing and replacing the safety wedge, &c., the
following apparatus is employed.

Two cog wheels, a large and a small one, are fixed on the upper part of
the after end of the torpedo, just in front of the screw propellers:
the small wheel is fitted with a certain number of teeth, thirty for
instance, which gears into an endless screw attached to the propeller
in such a manner that one revolution of the propeller moves the wheel
one tooth, therefore thirty revolutions would turn the wheel one
complete revolution. The big wheel is fitted with much larger teeth
than the small one, and by means of a pin on the latter wheel is moved
round one tooth for every complete revolution of the small wheel, and
clamped in this new position by a spring catch, which is also worked by
the pin on the small wheel. In front of these wheels is a stud which
works fore and aft in a slot, and attached to a spring which tends
to draw it to the after end of the slot. This stud is connected by
means of a wire rod to the valve that admits the compressed air to the
engines; when the stud is in the fore part of the slot the valve is
open, and when in the after part it is closed.

_Adjusting Length of Range._--By means of a lever the spring of the
stud is compressed, and the stud moved to the fore part of the slot;
then the big wheel is moved round until a stud on its face is the
required number of teeth above the lever. For every thirty revolutions
of the propeller, and consequently one tooth of the big wheel, a
certain known distance is traversed, which varies according to the
pattern of the torpedo.

_Adjusting Apparatus._--When the propeller has made the number of
revolutions corresponding to the length of range required, and
consequently has moved the big wheel the number of teeth it was set
above the lever, the stud on the big wheel presses against the lever
and so releases the spring in the slot, causing the slot stud to fly
from the fore part to the after part of the slot, by which action
the valve admitting the compressed air to the engines is closed, and
consequently the engines cease to work.

Attached to the axle of the big wheel is a small brass arm, which
is connected by means of a brass rod to the safety wedge, and is
so arranged that after the required number of revolutions of the
propeller, the safety wedge will be drawn out; or it may be drawn out
at the instant of the torpedo leaving the tube, carriage, &c. Also by
means of an additional lever at the fore part of the torpedo, which is
connected by means of a wire rod to the valve that admits the air to
the engines, and by arranging the attachment of the safety wedge to
the brass rod from the big wheel, so that on the wedge being withdrawn
it is released from that brass rod, on the torpedo having completed
its run, the action of closing the valve which admits the air to the
engines causes the additional lever to force the wedge into the safety
position.

_Torpedo to Float at End of Run._--This is due to the difference of
buoyancy at the end of a run from what it was at the commencement,
owing to the compressed air being used in working the engines.

_Torpedo to Sink at End of Run._--This is effected by means of the
adjustment chamber (2), in the after end of which there is a spiral
spring valve, which can be attached to the brass rod on the outside of
the torpedo that works the valve which admits air to the engines, in
such a way that on the valve being closed, and therefore the run of the
torpedo completed, the spiral spring valve is opened, admitting water
to the adjustment chamber (2) of sufficient amount to sink the torpedo.

_To Explode the Torpedo at End of Run._--This is effected by connecting
the vertical firing whisker to the rod which otherwise would be
connected to the safety wedge lever, by which means, on the valve
admitting air to the engines being closed, a force is transmitted
to the vertical whisker instead of to the safety wedge lever, and
consequently the torpedo is exploded.

_Adjusting the Depth._--A small wheel, the face of which is marked in
feet, is placed on the left side of the fore part of the adjustment
chamber (2). To adjust for depth, by means of a key turn the wheel
until the number corresponding to the depth of run required is opposite
the pointer.

The torpedo is maintained at the desired depth by means of certain
mechanical apparatus contained within the adjustment chamber (2), and
which constitutes what is termed the secret of the fish torpedo. This
chamber is connected by screws to the foremost and after chambers of
the torpedo, in such a manner that by means of a number of small holes
bored round the circumference, as shown at (2), Fig. 119, the faces
of the chamber are exposed to the pressure of the water, which varies
with the depth to which the torpedo descends. Within the adjustment
chamber is an endless strong spiral spring, attached to the after face
of the chamber, and so arranged that after being set to a certain
tension, capable of resisting an equivalent pressure on the outside
of the aforesaid face, any increase or decrease in this exterior
pressure will cause the spiral spring to work a rod by which the
horizontal rudders of the torpedo are regulated, and thus the desired
depth for which the spring is set is maintained. The course of the
torpedo is represented by a series of curves, above and below the line,
representing the depth it is set for, these curves gradually decreasing
until at 100 yards' distance from where the torpedo was started the
curves are so small that the path of the torpedo is almost identical to
that of a straight line.

Within this adjustment chamber is also placed an automatic balance,
which also assists to maintain the torpedo at the desired depth, by
reason of its swinging forward on the torpedo descending, and swinging
aft on its rising, which motion is used to regulate the horizontal
rudders. The above is merely a general idea of the arrangement used in
the Whitehead fish torpedo, to enable it to reach and maintain whatever
depth it may be necessary to use it at from 5 to 15 feet.

_Projecting the Torpedo._--The fish torpedo may be projected in various
ways, viz.:--

1.--Through a submerged tube in the stem, or on the
broadside.

2.--From a carriage above the surface.

3.--From the surface.

_Discharging Torpedo through a Submerged Tube in the Stem._--In this
case a tube is fitted to an orifice in the stem; this opening is as
far below the water line as possible, and is closed by a watertight
cap and a sluice valve; the inner end of the tube is fitted with a
watertight door; the torpedo being prepared for action is placed inside
the tube, the inner door closed, and the tube filled with water; then
the watertight cap and sluice valve are opened, and the torpedo started
by means of a piston which is worked by compressed air. This piston can
be worked from deck, and so the torpedo fired at the proper instant.
To prevent the torpedo from slipping out of the tube, a stop is placed
in the fore end of it, which can be withdrawn at the same time as the
compressed air is admitted behind the piston. The torpedo being clear
of the tube, the sluice valve and watertight cap are closed, and the
tube emptied of the water, the projecting piston being at the same time
forced back.

_On the Broadside._--In this case, the discharging tube works inside an
iron casing, through a stuffing box at the inner end, and in a shield
attached to the outer end of the tube. This shield, placed on the fore
side of the orifice, is of such a length as to protect the torpedo from
the pressure of the water passing the vessel. The mode of discharging
the torpedo in this case is similar to that used when projecting it
through the stem.

_Comparison of the Stem and Broadside Methods of Projecting the
Torpedo._--The former method of projecting the torpedo seems the most
suitable to specially built torpedo vessels, but not so to large
ironclads, on account of the difficulty of fitting a tube to the stem
of such a ship, and also that in so doing the efficiency of the vessel
as a ram would be impaired.

In regard to the accuracy of the firing of the above methods, both seem
equally good, though in the case of firing on the broadside it would
be necessary to prepare carefully calculated tables of deflection, any
mistake in the using of which would be fatal to a successful torpedo
shot.

_Projecting a Torpedo from above Water._--In this case an iron carriage
is used, which is fitted with a frame, in which the torpedo rests; the
outer end of this frame is provided with a lip, some few feet long,
by which means the rear end of the torpedo is slightly canted up on
leaving the frame, and any undue strain on the tail of the torpedo is
prevented. The frame is mounted in the iron carriage in such a way that
it can be elevated or depressed by means of a screw, as in the case of
a gun mounted in an ordinary carriage. The torpedo is ejected from the
frame by means of a piston as previously explained, a small reservoir
of air being attached to the carriage, so that it can be used at any
port.

_Firing a Torpedo from the Surface._--The torpedo possesses sufficient
buoyancy to float with a small portion of its upper surface above
water; such being the case, it is only necessary to set the various
adjustments, point it in the required direction, and by hand turn back
the lever on the upper part of the weapon (which opens a communication
between the air chamber and the engines), when it will instantly dart
off and very rapidly attain the depth it is set for.

_Method of Firing a Fish Torpedo from a Boat._--To manipulate a fish
torpedo from a boat, it may be carried in a light frame, which can
be lowered or raised by means of a pair of davits. When required to
discharge the torpedo, the frame containing it is lowered into the
water, so as to bring the torpedo about two feet below the surface, the
head being somewhat lower than the tail.

_Thornycroft's Method of Firing Fish Torpedoes from a Boat._--Another
method, which has been patented by Mr. J. I. Thornycroft, of the firm
of J. I. Thornycroft and Co., steam launch builders, and which is
fitted to the torpedo boats built by them for foreign governments, is
shown in elevation and plan at Figs. 120 and 121.

The apparatus consists of two or more bent levers _A_ securely and
rigidly fixed on a shaft _B_, which works in bearings fixed on the deck
of the vessel _C_ from which the torpedo is to be discharged. On the
ends of the levers _A_ furthest from the shaft _B_ are pivoted other
levers _D_, to which the cradle or case _E_ for sustaining the torpedo
is suspended. The other ends of each of these levers are connected to
the vessel by means of rods or tubes _F_, jointed at each end in such
a way that when the shaft _B_ is made to revolve in its bearings, the
case containing the torpedo is guided over the side of the vessel and
close to it, and is held in a position convenient for discharging the
torpedo, as shown at Fig. 120.

The shaft _B_ may be made to revolve by means of ropes _G_ and pulleys
_H_ attached to the levers _A_, or by hydraulic or steam pressure, as
may be found most convenient.

The torpedo case can be towed alongside the vessel if necessary without
deranging the apparatus. The torpedo case is carried in the angles
of the bent levers, and is stowed away so that neither it nor the
suspending levers project at all beyond the hull of the vessel; also
when lowered, the levers and suspending rods fold over one another so
as to occupy very little space, and the torpedo is suspended close to
the hull.

Also the torpedo during the operation of lowering as well as when in
a firing position remains close to the side of the vessel, thereby
obviating any risk or inconvenience from excessive leverage which would
have a tendency to capsize the boat.

For especially built torpedo launches, the above mode of carrying and
launching the fish torpedo is certainly the best yet devised.

_Woolwich Fish Torpedo._--In the Woolwich torpedo, the engines exert a
force of nearly 60 indicated horses, and work up to 1000 revolutions
per minute; the total weight of the torpedo fully charged (33 lbs. of
gun-cotton) is about 500 lbs.

[Illustration: THORNICROFT'S BOAT APPARATUS FOR FISH TORPEDOES.

PLATE XXXVII]

The Whitehead fish torpedo costs about 380_l._, while the Woolwich one
costs only 300_l._

_The Lay Torpedo Boat._--Priority of invention of this torpedo was on
the 13th of June, 1873, awarded by the Commissioners of Patents to Mr.
John Louis Lay, several other persons having claimed the invention,
among whom was Colonel Von Scheliha, an officer of the Russian army.

This locomotive torpedo, or more properly called torpedo boat, has been
for several years adopted by the American government, during which time
it has undergone a series of exhaustive experiments, which has proved
it to be a most valuable and efficient weapon of offence and defence.
Lately the Russian government have adopted it, and intend using it
extensively in the defence of their harbours, &c.

_General Description of the Torpedo._--At Fig. 122 is shown a
longitudinal section of a Lay torpedo boat constructed and provided
with guiding and controlling apparatus, and with means for propelling
it by ammoniacal gas. Fig. 123 is a horizontal section of the same;
_A_ is the hull or body of the boat, which has conical ends _A_^{1},
_A_^{2}, and is formed of thin plate iron, or steel, or other suitable
material. The section in the end _A_^{1} forms the magazine containing
the charge of dynamite or other explosive material; _A_^{3} is the
section containing the gas reservoir or holder; the compartment _A_^{4}
contains the apparatus for holding and paying out the electric cable;
the compartment _A_^{5} in the end _A_^{2} contains the motor engine,
the steering apparatus, and other parts to be hereinafter described.
All of these compartments or sections are separated from each other by
means of air-tight bulkheads _A_^{6}. The torpedo boat may be propelled
by means of a single screw, double screw, or two screws. In the latter
method, which is shown at Figs. 122 and 123, the propellers _B_ and
_C_ are made to revolve in opposite directions; the shaft _D_ of the
propeller _B_ is hollow or tubular, and the shaft _E_ of the screw
_C_ passes through the same; these screws are actuated by an engine
shown at _F._ _H_, _H_ are the horizontal rudders, or side wings, two
forward and two aft; these wings are mounted on shafts or spindles
passing transversely through the boat; these rudders may be set to
occupy a horizontal position, or a more or less inclined position in
the proper direction, to cause the submerging of the boat by the action
of the water on the said rudders as the boat moves forward, and they
are adjusted before starting. _N_, _N_ are two guide rods, one aft
and one forward, which project up from the boat to enable the operator
to determine its position at any part of its run, and in the case of a
night attack they are provided with lights; the said rods can be raised
or lowered at the will of the operator. _Q_ is the electric cable,
which affords a medium of communication between the operator on shore,
&c., and the torpedo boat, whereby it may be started, stopped, steered,
fired, and has her position ascertained; this cable is carried in the
boat in a coil arranged longitudinally in the air-tight chamber _A_^{4}
in the reel frame _R_, and is payed out as the torpedo progresses
through a tube _S_, projecting aft under the boat and beyond the
rudders and propellers, so that the said cable will not be fouled by
the same; or it may be payed out through a hollow shaft in the centre
of the boat. One end of this cable is connected to a keyboard at the
station on shore or on board of the ship or other structure from which
the torpedo boats are controlled. This keyboard is provided with a
suitable battery or other means for generating the electric current, as
hereinafter described.

The said cable is composed of several wires, each of which is insulated
from the others. One of these wires is connected with the mechanism
for starting and stopping the boat, one is connected with the steering
apparatus, one serves for indicating to the operator at all times the
exact position of the rudder, one is connected with mechanism for
elevating and depressing the said guide rods, and one serves for firing
the charge in the magazine.

The motive power for effecting the necessary movements of the mechanism
or apparatus in performing the above operations is obtained from the
aforesaid engines, which are provided with suitable valves arranged in
combination with electro magnets, shunts, and the devices connected
with the said wires of the cable, as hereinafter set forth.

This form of cable has since been replaced by one which consists of two
wires only, the one for performing all of the necessary operations,
exclusive of the firing or exploding of the magazine, and the other
exclusively for this latter purpose. This improvement is effected by
employing a series of relays or resistance coils, or a multiple, or
compound relay in the boat. The advantages gained by this improved form
of cable are:--

1.--Increased flexibility.

2.--A greater length of cable may be coiled in a given
space.

3.--A thicker coat of insulating material may be used,
thereby more perfectly insulating it.

4.--It is much cheaper.

Two rudders are generally used, one below and one above the boat, as
shown at _U_, Fig. 122. These rudders are operated and controlled by
means of a small auxiliary engine _T_, Fig. 122, which is started,
stopped, and reversed by the electric current conducted through the
cable _Q_ in connection with magnets attached directly to a valve
forming part of the said engine. This valve is so actuated by the
magnets that when the current passes in one direction the engine _T_
will move the rudder to starboard, and when the current acts in the
opposite direction it will turn the rudder to port.

The mechanism for firing the charge in the magazine _A_^{1} is clearly
shown in Fig. 124, and operates as follows:--Projecting from the front
extremity or stem of the boat is a rod or pin _V_, which extends
through a suitable packing box _W_ into the said magazine or charge
chamber; when the boat strikes an object, the said rod is forced
inward into contact with the springs or points _X_, thereby closing
an electrical circuit and igniting a cartridge, shown at _Y_, in the
magazine.

The charge in the magazine can also be fired at any moment by the
operator on shore closing a circuit on the keyboard and thereby
cutting out one of two resistance coils placed in the circuit to
prevent accidental or premature discharge--that is to say, there are
two resistance coils. The battery is not sufficiently powerful to
fire through both resistance coils at the same time. When the boat
strikes an object, the resistance coil in the magazine is cut out by
the driving inward of the rod _V_, as above described; the battery
then fires through the one on the keyboard. On the other hand, if
the operator desires to fire the torpedo boat before she touches the
object of attack, he manipulates the switch to cut out the coil in the
keyboard, the charge then being fired through the coil in the magazine.
This arrangement of the two resistance coils is very effectual in
preventing accidents.

In some instances the magazine is made detachable from the hull of the
boat, so that on striking an object it will descend or drop down in the
water before exploding. This modification is shown at Figs. 125 and 126.

The magazine _A_* is attached at its lower side to the boat by a chain
or other suitable connection. At its upper edge it is held by a rod
_a_*, as shown in Fig. 125. This rod is fitted to slide in dovetailed
bearings, as shown at _b_*, and when this magazine is in its place
on the boat the said rod is engaged with a catch or stop _c_*, but
when the said rod is driven against any object it is forced back and
released from the said catch or stop, and the magazine then drops, as
in Fig. 126, and is fired.

To effect the firing a ball _d_* is used and placed in a tube
containing two springs or plates _e_* and arranged in an upwardly
inclined position, as shown in Fig. 125, one of the said springs being
connected with the cable and the other with a wire that passes through
the cartridge to earth.

While the magazine is in the position shown in Fig. 125 the circuit
is incomplete, but when the magazine drops the said ball falls into
the position shown in Fig. 126; the circuit is then completed, and the
magazine is fired.

The electrical or electro-magnetic apparatus for generating, directing,
and controlling the currents, whereby the above-described operations
are effected, may be of any suitable kind, the following being the form
of apparatus usually employed.

A battery _r_, shown at Fig. 127, consists of any desired or requisite
number of cells constructed and arranged in any suitable manner, and
connected by proper conducting wires with the keyboard _s_. The latter
is provided with a series of pole changers _s_^{1}, _s_^{2}, _s_^{3},
_s_^{4}, and switches _s_^{5}, _s_^{6}, and is shown in Fig. 128.

Each of these pole changers is arranged to effect and control one of
the above-named operations, and is therefore connected with one of the
aforesaid insulated wires forming the cable. For instance, the pole
changer _s_^{1} effects the starting and stopping of the propelling
engine; _s_^{2} controls the steering apparatus; _s_^{3} is connected
with the steering index; _s_^{4} operates or adjusts the aforesaid
guiding rods; and the switches _s_^{5}, _s_^{6} control and effect the
firing of the charge in the magazine.

[Illustration: LAY'S LOCOMOTIVE TORPEDO.

PLATE XXXVIII]

[Illustration: LAY'S LOCOMOTIVE TORPEDO.

PLATE XXXIX]

The connections between these pole changers and switches, and
the apparatus they operate or control on board the boat, are as
follows--that is to say, the said propelling engines have a throttle
valve, which controls the admission of the gas from its generator or
reservoir to the cylinders of the said engine, and in combination
with this valve in the boat there is a shunt and set of electro
magnets. The armature of the latter is connected with a lever, which
is pivoted so that the action of the electric current in one direction
through these magnets will pull one end of the said lever down, and the
action of the current in the other direction will pull its other end
down--that is to say, by reversing the current through these magnets
the movement of the said lever is reversed; and this lever, connected
by suitable means with the slide of the said throttle valve, will open
or close the same, and thereby start or stop the engine as required.

For operating and controlling the above-described steering apparatus,
and indicating the position of the rudder to the operator on shore, the
following devices are employed, in combination with the pole changers
_s_^{2}, _s_^{3} on the keyboard:--The pole changers are geared
together by insulated toothed wheels, which are fixed on the spindles
or axes of the said pole changers, so that the latter work accurately
together and maintain the same relative positions to each other. The
pole changer _s_^{2} is connected by one of the said insulated cable
wires with a shunt on board the boat, which shunt is connected with a
set of magnets arranged in combination with the valve of the engine
that drives the steering apparatus, and which valve is reversed or
opened and closed by the reversal of the currents through the said
magnets, as above described, and the said engine moves the rudder
to port or starboard at the will of the operator. In order that the
operator may know the exact position of the rudder at any moment, a
series of pins or projections fixed on an arc or other portion of the
rudder stock, and arranged in combination with an insulated spring
projecting into the path of the said series of pins, are employed. This
spring is connected by one of the cable wires with the pole changer
_s_^{3} on the keyboard, which is geared with and moves in unison with
the pole changer _s_^{2}, so that the electric current that controls
the steering engine, and the current that returns the indication of the
rudder's position, will both be reversed simultaneously. A separate
battery is connected with the index on the said keyboard, whereby a
constant current is maintained between this index and the indicating
apparatus on the boat.

The current passing from the said spring to the shore is made to
indicate the position of the rudder by the index on the keyboard by
the contrivance shown in Fig. 129. This contrivance consists of a
set of magnets _w_, which have a vibrating armature _w_^{1} pivoted
to oscillate between them. One end of the armature lever is provided
with insulated spring pawls _w_^{2}, which take into ratchet wheels
_w_^{3}. On the same shafts on which these ratchet wheels are fixed are
wheels _w_* formed with insulated teeth and geared with each other. The
shaft of one of these wheels is geared by bevel pinions _w_^{4} with a
vertical shaft _w_^{5}, to which is attached the index needle or finger
_x_**, Fig. 128. Therefore it will be obvious that this index finger
is placed in connection with the aforesaid spring and series of pins
attached to the rudder yoke on board the boat.

Now it will be obvious that when the rudder is turned in either
direction these pins will come successively in contact with the said
spring, and at each contact and separation the circuit will be made and
broken, and an impulse will be transmitted through the cable, whereby a
corresponding movement will be transmitted to the said index finger or
pointer _x_** on the keyboard.

The pole changer _s_^{4} is connected with another of the insulated
wires of the cable, which on board the boat is connected with a shunt
and set of magnets arranged in combination with the aforesaid cylinders
that operate the said guiding rods, so that by sending the current in
one direction the said rods will be raised, and by sending the current
in the opposite direction the said rods will be lowered.

The switch _s_^{5} is connected with another of the said insulated
wires of the cable, which forms the circuit, including the aforesaid
two resistance coils.

By adjusting this switch the operator completes the circuit through the
two resistance coils, and then, but not till then, the charge can be
exploded, either by the operator, or by the action of the firing pin or
rod when the same is driven in and cuts out the other resistance coils
as above described. The resistance coil _X_^{1}, Fig. 124, is connected
to the binding screws 9, 10 by the wires 7 and 8. These binding screws
are in metallic connection with the two springs _X_, but otherwise they
are carefully insulated. One pole of the fuze _Y_ is connected to the
binding screw 10, the other put to earth through the body of the boat,
as at _E_; the main wire 11 is connected to the binding screw 9. Now
when the operator cuts out the resistance coil at the firing station,
which is done by moving the switch _s_^{6}, the electric current is
sufficiently powerful to ignite the fuze _Y_ through the resistance
coil _X_^{1}, so that at any moment the torpedo may be exploded by
the operator on shore, or by the contact between the torpedo and the
attacked vessel the rod _V_ will be driven in, and, coming in contact
with the springs _X_, will bridge over the space that originally
existed between them and so cut out the resistance coil _X_^{1}, and
the torpedo will be exploded automatically.

_Capabilities of the Lay Torpedo Boat._--The capabilities of the Lay
torpedo boat are as follows:--

1.--It may be launched from the shore, a vessel,
or a structure, and be kept under observation, and
accurately guided or directed to the ship or other
object to be attacked; and it may be exploded at any
desired moment, or it may be caused to return to the
original point of departure without being fired.

2.--It may be totally and instantaneously submerged to
prevent its destruction or capture by the enemy, and it
may be raised to the surface, as soon as the danger has
passed, in a condition fit for immediate action.

3.--It may be used as a tug or towing boat to take out
a number of torpedoes, which may be sunk and exploded
when desired.

4.--It may be used in connection with certain apparatus
to clear away obstructions found to prevent the
entrance of ships into harbours, and it may also be
used to clear harbours of mines, &c.

_Launching the Lay Torpedo Boat._--For facilitating the launching and
controlling of the Lay torpedo boats, a structure or submarine fort
is used. This structure may be square, or oblong, and may be made to
carry any number of the torpedo boats. The body is constructed of plate
or sheet iron of suitable strength and stiffened with angle iron, or
otherwise, and divided longitudinally or transversely into watertight
compartments, into which the water is admitted to sink the said
structure. At the top or upper side, cylinders or tubes are placed,
each of which is capable of containing and launching one of the torpedo
boats. At the forward end of each tube is a door, or cover secured to a
rod or shaft fitted to turn in suitable bearings; this rod or shaft is
provided with an arm which is connected to the piston rod of an engine
worked by gas contained in a reservoir, or by other suitable means.
The slide or other valve which controls the admission of the gas,
&c., to this engine is arranged in connection with electro magnets,
connected by a suitable cable with a keyboard on shore, or wherever
the operator's station may be. By sending an electric current through
this cable in one direction through the electro magnets, the door is
closed; and by sending such a current in the opposite direction it is
opened. The cables carried in the torpedo boats, and through which the
mechanism on board each torpedo boat is operated and controlled, are
also in this case connected with the keyboard, which must be provided
with a number of sets of pole changers and switches, or equivalent
devices, corresponding with the number of boats to be controlled by
means of the said keyboard.

This apparatus will form a very convenient adjunct to fortifications or
stations liable to be attacked by sea. The said fort may be prepared
for use by placing torpedo boats in the said tubes, and may be kept
floating until the enemy's ships have arrived closely enough to
permit the determination of the point where the said fort can be most
advantageously located for operating against the said ships. The fort
is then towed to this point, or taken as near as possible thereto on
rails, and towed the remainder of the distance. It is then submerged,
and will be ready for immediate operation. The said fort is provided
with suitable valves for the admission of water to sink the same, and
with means for forcing in air through the pipe _P_* to expel the water
when the fort is to be raised.

When it is desired to launch either of the said torpedo boats, the door
of its tube or cylinder is first opened by sending a current through
the cable that controls the door, as above described. Then the current
is sent through the boat's cable to start her propelling engines. The
said boat will then emerge from the cylinder or tube and will rise to
the surface, or as near the surface as may be desired, and may then be
directed and controlled by the operator at the keyboard, as previously
described. And one after another of the said torpedo boats may be thus
launched and exploded, without giving to the enemy any clue to the
point or position from which they are being sent.

[Illustration: LAY'S LOCOMOTIVE TORPEDO.

PLATE XL]

_Launching the Torpedo from a Ship._--The method of launching the Lay
torpedo boat from an ironclad or other large ship is shown at Fig.
130. The tubes or cylinders _S_ in which the torpedo boats _A_ are
held are, in the apparatus shown at Fig. 130, closed at their inner
ends by plates, or covers _S_^{1}, which are provided with suitable
water-tight and insulating packing boxes _S_^{2} for the passage of the
electric cables of the said torpedo boats, each cable being connected
with the keyboard, which is placed in any convenient part of the ship,
and at their outer ends the said tubes are furnished with strong and
well-fitted slide valves, or sluice gates _S_^{3}, which are opened
by screws, connected by gearing with a hand wheel, and shaft _S_^{4},
_S_^{5}, for the admission and exit of the said torpedo boats. Also
these cylinders are provided with packing pieces at their sides,
arranged to be pressed by screws or otherwise up to the sides of the
torpedo boats in these cylinders, and thereby hold them firmly and
immovably in rough weather.

_The Method of Sinking and Raising a Lay Torpedo Boat._--The apparatus
by which this is effected is shown at Fig. 131, which is a longitudinal
section of a portion of a torpedo boat. The hull _A_ of the torpedo
boat is provided with a water chamber _l_, which has holes or apertures
_l_^{1} in the bottom of the same, and is also provided with an air
cock at _l_^{2}. In connection with this chamber is arranged a small
cylinder _m_, provided with a piston _m_^{1}, whose rod _m_^{2} is
attached to the lever of the said cock. A spiral spring _m_^{3} is
provided to resist the inward movement of the said piston. The said
small cylinder _m_ is connected by a pipe _m_^{4} with a valve chest,
in which is arranged a slide valve _m_^{5}. The said slide valve is
connected by a rod or rods to the lever or levers _m_^{6}, whose
fulcrum is at _m_*, and the said levers are connected by the links
or rods _m_^{7} with the armatures of electro magnets _n_, which are
included in the circuit of the cable, whereby the boat is controlled
from the keyboard at the station; _o_ is a pipe extending from the said
valve chest to the aforesaid water chamber _l_; _p_ is a feed pipe by
which gas is conducted from the reservoir or generator to the valve
chamber.

When it is desired to sink the torpedo boat an electric current is sent
in one direction through the said magnets, and thereby operates the
slide valve to admit gas to the cylinder _m_ in front of the piston
_m_^{1}, which is thus forced inward and opens the air cock _l_^{2}.
The opening of this cock permits the escape of the air from the water
chamber _l_, and consequently the entrance of water through the
apertures _l_^{1}, and the boat then immediately sinks.

When it is desired to raise the boat a current is sent in the opposite
direction through the said electro magnets, thereby operating the said
valve and piston in such a manner as to close the cock _l_^{2} and
open the port _o_^{1} and the pipe _o_, thereby allowing the gas to
pass from the valve chamber into the compartment _l_; this gas by its
pressure expels the water from the said compartment, and the boat then
having its normal buoyancy restored immediately rises to the surface.

_The Lay Torpedo Boat used as a Tug to take out a Number of Small
Torpedoes._--This arrangement is shown at Figs. 132 and 133. The
small vessels or torpedoes are designed to be first sunk and then
exploded, chiefly for clearing harbour or the like of mines or other
obstructions. These results are accomplished by means of the following
devices and arrangements, that is to say, each of the small vessels
or torpedoes _F_ is provided with apparatus which is included in an
electrical circuit formed by a suitable insulated cable _G_, extending
throughout the train of small vessels or torpedoes _F_. One vessel of
this train, preferably the rear one, is connected with the station by
an electrical cable _H_, which is payed out from a coil or coils, or
a reel or reels, in the said vessel as the same travels through the
water. This cable _H_ connects with the cable _G_, which is connected
with the towing boat _A_, and passes through the series of boats
_F_ to the said cable _H_. One wire of the said cable is arranged
in combination with sealed or covered apertures in the bottom of a
compartment or compartments of these small vessels _F_, as shown at
_I_, the covers of these apertures being so formed as to be ruptured
or destroyed by the explosion of a cartridge or cartridges placed in
the said compartment or compartments. When a current of electricity is
sent through the aforesaid wire of the cable it will explode the said
cartridges and open the apertures, thereby admitting water into the
said compartments so that the vessel _F_ will sink.

The cable _G_ that passes through the train of torpedoes or vessels _F_
is so arranged that when a current passes through the other wire of the
said cable it will fire cartridges placed in the charge chambers or
magazines of the said small vessels, as shown at _J_. The part of the
cable or towing line _G_, which connects the towing boat _A_ with the
train of small boats or torpedoes _F_, is attached to a hook or other
device, which can be disengaged by sending a current through the cable
_K_, connecting the boat _A_ with the shore or other station. It will
be understood that when being used for this purpose the said boat _A_
is not or need not be charged with explosive material.

[Illustration: LAY'S LOCOMOTIVE TORPEDO.

PLATE XLI]

The aforesaid towing boat _A_ takes the train of torpedoes _F_ to any
required position. It is then disengaged from the train, leaving the
said small vessels or torpedoes _F_ floating in such position. Then by
sending a current first through one wire of the cable _H_ the boats _F_
are first sunk by the explosion of the cartridges and opening of the
apertures, as above described. They may then be discharged immediately
by sending a current through the other wire of said cable _H_ and
firing the cartridges in their magazines, or they may be left submerged
to form mines which may be exploded at any desired moment.

The said small vessels or torpedoes may be provided with vertical rods
to indicate their position to the operator at the station; these rods
are shown at _L_, and they should be made hollow to allow the air in
the water compartments or chambers to escape to permit the water to
enter the same when the vessels _F_ are to be sunk; or other suitable
provision may be made for the escape of the air from these compartments.

The said vessels _F_ are preferably made cylindrical with conical ends,
and are provided with suitable insulating and water-tight packing
boxes, as shown at _F_^{1} for the cable _G_ to pass through at the
stem and stern of each vessel.

_The Lay Torpedo in Clearing Obstructions._--For this purpose the
torpedo boat is provided with an apparatus, shown at Figs. 134 and
135, in combination with the electric cable, whereby the said boat
is controlled and guided, and there is arranged in the boat _A_ a
compartment _A_^{3}, from which extends down into the water a line
or rod _U_, provided at its outer end with a hook or claw _U_^{1},
properly formed to take hold of any chain or bar with which it may come
in contact. In the said compartment _A_^{3}, and upon the upper end of
the said line or rod _U_, is placed a small case or cylinder _U_^{2}
containing a charge of dynamite or other explosive material and a
cartridge or fulminating cap, or a bottle of sulphuric acid, surrounded
with a certain quantity of chlorate of potash and sugar. This case
or cylinder _U_^{2} is shown detached and drawn to an enlarged scale
at Fig. 135, and it will be seen that the said case is provided with
a tube 1 containing a cartridge, or a phial filled with explosive
substance at 2, and a ball or weight at 3. The said case is fitted
to slide upon the said line or rod _U_, and when placed at the upper
end thereof and not held or retained will slide to the lower end of
the same. In the said compartment _A_^{3} is arranged at _U_^{4} an
electro-magnetic apparatus, included in the circuit of the said cable,
and connected with a bolt or catch which in its normal position holds
the said explosive case and prevents its running down on the grappling
line or rod _U_. This explosive case is also provided at its lower end
with a grappling hook _U_^{5}.

When the grappling hook _U_^{1}, on the lower or outer end of the line
or rod _U_, engages with any obstruction the boat will be stopped, and
this stoppage will be indicated on the keyboard. The operator by this
indication is apprised of the stoppage of the boat by an obstruction,
and by sending a current through the cable by means of a switch
provided for this purpose on the keyboard he can immediately release
the explosive case _U_^{2}, which runs down the line or rod _U_, and
engages by its grappling hook _U_^{5} with the hook _U_^{1}. The line
or rod _U_ is then disengaged from the boat _A_, and the explosive
case _U_^{2} turns or falls over. As it turns over the ball or weight
3 contained in the tube 1 drops on the said phial 2, fractures it, and
thereby allows the acid to mix with the explosive or fulminating charge
and explode the case _U_^{2}. This explosion will rupture or destroy
the obstructing chain or bar, so that the ironclad ships or other
vessels can pass freely and safely into the harbour or beyond the point
where it was intended to stop them.

_Used to clear away Mines and Electric Cables._--For this purpose there
is an implement _V_ provided, Fig. 136, somewhat of an anchor form, but
with four or any desired number of arms _V_^{2} extending outward at
a suitable angle from its shank _V_^{1}. In the neck of each of these
arms are fitted two small plain or toothed discs _V_^{3}, which are so
arranged as to present their teeth to any object lying in the angle or
corner formed by and between the arms _V_^{2} and shank _V_^{1} of the
said implement, as shown at _W_.

In using this implement it may be attached to a line or cable coiled
in the torpedo boat, which, in this case, is used without being
charged with explosive material, and is sent in advance of any ship
that has to enter or pass through the suspected water. This line must
be arranged in combination with a detaching apparatus controlled by
electro-magnetic apparatus included in the circuit of the cable which
connects the torpedo boat with the keyboard at the operating station.

[Illustration: LAY'S LOCOMOTIVE TORPEDO.

PLATE XLII]

By sending a current from the station the operator releases the said
implement or its line from the detaching hook or holding device. The
said implement then sinks to the bottom; then the said boat returns
to the ship, paying out the said line as she so returns. The end of
this line is then taken by a steam tug or other vessel, and the said
grappling implement is thereby dragged along through the water over
which the ships are to advance, thus breaking any wires or cables that
may be in its course. This operation is shown at Fig. 137, in which _A_
is the towing boat, _K_ the controlling cable, _V_ the said implement,
_V_* the line attached to the implement _V_, _X_ _X_ submerged mines,
and _X_^{1} _X_^{1} are the mine cables.

In some instances it may not be practicable to reach the enemy's
ship or other object of attack directly from the station to which
the torpedo boat is connected, and from which it is controlled. In
this case a small boat, &c., is used in addition, which should be so
arranged as to present to the enemy's view as slight a surface as
possible. This mode of attack is shown at Fig. 138, where _A_ is the
torpedo boat, and _N_ is the small auxiliary boat. This boat _N_ is
provided with a keyboard and battery like that described at page 144,
and the electric cable _L_, carried on and payed out from the torpedo
boat _A_, is connected with the keyboard. The boat _N_ is also attached
to and towed by the torpedo boat _A_ by the tow line _O_; and the
torpedo boat is steered and guided by means of the said keyboard in the
boat _N_. The auxiliary boat is designed to contain two men, who lie
down, one at the bow, the other in any convenient position abaft him;
the latter has control of the keyboard, while the former by the aid of
a telescope keeps the torpedo boat in view, and transmits his orders to
the man at the keyboard. On arriving at such a distance from the enemy
as to render an attack practicable, the tow line _O_ is disengaged,
and the torpedo boat _A_, guided and controlled, and fired from the
boat _N_. The torpedo boat being exploded, the auxiliary boat can be
rowed back to the station or ship to which it belongs. By this means
the range of action of the torpedo boat is greatly extended, and with
comparatively slight danger to those employed in making the attack.

A more recent form of the Lay torpedo boat is shown at Figs. 139, 140,
and 141, where Fig. 139 is a plan or top view of such a boat, Fig. 140
is a side elevation of the same, and Fig. 141 is a midship section on
the line _x x_. _A_ is the hull of the boat, _a_ is the main or central
portion of the said hull, _b_, _b_ are side or auxiliary portions of
the same. These parts _a_ and _b_ may be oval or circular in transverse
section; they are constructed of thin steel or other suitable sheet
metal, and secured together by riveting or bolting. The side or
auxiliary portion _b_ form the reservoirs or chambers for the gas; they
also serve to contain the propelling engines. _c_ is the magazine, _d_
the chamber or compartment for containing the coiled cable, _e_ is the
compartment containing the electrical steering and other apparatus, _f_
is the firing rod or pin, _g_ is the water ballast chamber, _h_ is the
cable, _i_ the paying-out tube, _j_, _j_ are the screws or propellers
which rotate in opposite directions, and _k_, _k_ are the sight or
guiding rods.

The parts of the apparatus or mechanism whereby the various operations
of the torpedo boat are effected are connected to the cable and
controlled by electric currents transmitted from the station through
the cable, as previously described. The Lay torpedo boat weighs about 1
ton, its length is 23 feet, and speed 12 knots per hour.

_Spar or Outrigger Torpedo._--By a spar or outrigger torpedo is meant a
torpedo which is carried at the end of a pole or spar projecting from a
boat or vessel, and which may be fired either by contact or at will.

This system of submarine offence has up to the present time been the
only one that has successfully stood the crucial test of actual warfare.

During the civil war in America the spar torpedo attack was resorted to
by the Confederates and Federals, principally by the former, the result
being the loss of two large men of war and severe injury to several
other ships composing the Federal fleet, and the loss of one vessel of
war belonging to the Southerners.

The spar torpedo was also used on several occasions by the Russians in
their attacks on the Turkish ships in the war of 1877-8, but in only
one attempt was it the means of sinking a Turkish vessel.

_Description of McEvoy's Duplex Spar Torpedo._--At Fig. 142 is shown a
sketch of Captain McEvoy's improved patent duplex spar torpedo, which
is the form most generally used at the present time, and which seems to
fulfil all the requirements of such a submarine weapon, viz.:--

1.--Handiness, at the same time capable of containing a
charge of gun-cotton sufficient in contact to destroy
the most powerful vessel afloat.

2.--Certainty of action.

3.--Capable of being fired either on contact or at will.

4.--Mode of attaching the spar simple and very secure.

[Illustration: LAY'S LOCOMOTIVE TORPEDO.

PLATE XLIII]

In Fig. 142, _a_ is the case, capable of containing some 33 lbs. of
gun-cotton; _b_ is the tube through which the three wires _w_, _w_^{1},
and _w_^{2} are led; _c_ is the socket in which the wooden or steel
spar is introduced and secured, _d_ is the striker, which is attached
to a brass contact plate within the head of the case _a_ in such a
manner that any pressure either on the head or side of the striker _d_
will force the aforesaid plate in contact with the two studs to which
the battery wires are attached; _e_ is a cradle affixed to the striker
_d_ to ensure its action on contact being made by the torpedo with the
attacked vessel; the explosive is inserted at _f_, the socket _c_ being
made to screw on and off.

When a hollow steel spar is used, the battery wires are sometimes led
through the interior of the torpedo and the spar, by which means they
are well protected; the only objection to this method of leading the
wires being the probability of injury to them, should the spar be
broken on contact, or by a shot.

_McEvoy's Arrangement of Torpedo Wires._--At Fig. 143 is shown the
arrangement of wires as devised by Captain McEvoy, whereby the spar
torpedo may be exploded at will or on contact. _c_ and _z_ are the
poles of the firing battery, to which are attached respectively the
wires _d_ and _d_^{2}; _f_ is the fuze, which is placed in the centre
of the charge, and to the poles of which the wire _d_^{2} is attached,
the other end of this wire being connected with the stud _s_; to the
stud _s_^{1} is attached the other end of the wire _d_, and at the
point _c_ in the same wire is inserted a contact breaker; another wire
_d_^{1} is connected to the wires _d_ and _d_^{2} at the points _r_
and _r_^{2} respectively, and at the point _k_ in this same wire is
inserted a firing key, which latter is shown in section at Fig. 144,
from which the mode of connecting the two ends of the wires and of
using the key will be at once apparent. The contact breaker is somewhat
similar to the firing key, but there is no spring in it, contact being
made or broken by screwing the two parts together or apart. The object
of the contact breaker is to prevent the torpedo being exploded by
contact, and so to place the control of the weapon entirely in the
hands of the operator. As will be seen from Fig. 143, if contact is
broken at _c_, it is impossible to fire the torpedo unless the firing
key _k_ be pressed in; but should contact be made at _c_, then either
by means of the firing key _k_, or by the torpedo striking the hostile
vessel, its ignition will be effected.

The foregoing method of arranging the spar torpedo wires is certainly
very neat and effective, and is at the present time in extensive use.
As yet it has not been adopted by the English government, they still
preferring to fire the spar torpedo at will alone.

The different methods of manipulating the spar torpedo from boats will
be described in the following chapter.

_General Remarks on Offensive Torpedoes._--The torpedoes that have been
described in this chapter are the only ones that at the present time
can be considered as having been proved to be practically useful, and
which in future wars may be employed against ships with some chance of
success.

The spar, the Whitehead fish, and the Harvey towing torpedo have each
been subjected to the test of actual service, the former weapon being
the only one that has under those conditions been successfully used.
Taking this fact into consideration, also the high pitch of excellence
that has been attained in the construction of steam torpedo boats, and
also the results of the numerous exhaustive experiments that have been
from time to time carried out in England, America, and Europe, with
various modifications of the locomotive, towing, and spar torpedoes,
there can be no two opinions as to which of the numerous species of
offensive submarine weapons is the most practicable and effective, and
that is the spar or outrigger torpedo.

To manipulate successfully locomotive and towing torpedoes in an attack
against hostile vessels, the operators must be not only unusually
fearless and self-possessed, but also must possess a thorough practical
knowledge of the complicated method of working and manoeuvring those
weapons--in fact, they must be specialists; whilst in the case of the
spar torpedo, which may be fired by contact, it is only necessary to
employ men capable of handling a boat well, and possessed of dash and
pluck, to ensure an attack by such means being generally successful.
Of course under some circumstances, such as in a general action, when
the locomotive and towing torpedoes are manipulated from specially
constructed torpedo vessels, they will prove of great value, and the
fish torpedo fired from a boat, in close proximity to the attacked
vessel, in smooth water, and unmolested, would sink a vessel which
under the same circumstances, owing to her being protected by booms,
might prove impregnable to a spar torpedo attack; but such favourable
conditions will not often occur in war time.

[Illustration: M^{c.} EVOY'S DUPLEX SPAR TORPEDO.

PLATE XLIV]

As an offensive submarine weapon of defence, the Lay torpedo boat
should prove of real value; and also manoeuvred from specially
constructed vessels, it seems capable of being used in a variety of
ways. As yet little is known of this weapon, all the experiments
carried out with it having been confined to America; but now that
Russia has adopted it, and one or two have also been secured by the
Peruvians, its practical value will become more generally known.

CHAPTER VI.

TORPEDO VESSELS, BOATS, AND SUBMARINE BOATS.

_EMPLOYMENT of Torpedo Ships._--Torpedo ships, that is to say,
sea-going vessels, very fast, handy and impregnable, specially
designed to carry and operate offensive submarine weapons, such as
locomotive, towing, and the spar torpedoes, especially the former, are
now considered as a necessary and valuable adjunct to a fleet, their
special work being to give the coup de grâce to disabled ironclads
in a general action; they will also be used to attack the ships of
a blockading force, and against rival torpedo vessels. As a general
rule these torpedo ships will be armed with the ram and torpedoes
only, heavy guns being dispensed with, though the Nordenfelt and other
machine guns will be considered necessary.

_The German Torpedo Vessel Uhlan._--This torpedo vessel was built in
Germany by the Stettin Engine Company, and launched in 1876.

She is armed with a contact torpedo charged with dynamite carried on a
10-foot ram, lying deeply under the water line. To protect the vessel
from the effects of the discharge of the torpedo, she is built with two
complete parts, sliding one within the other, and having a considerable
extent of intermediate space between them. This space is filled with a
tough and elastic material (cork and marine glue), which even in the
case of the bows being carried away, would afford a second line of
resistance. The _Uhlan_ carries an engine of one thousand indicated
horse power. The steam is supplied by Belleville's tubular generator.
These engines occupy by far the greater space of the vessel, only a
very small portion being left for her crew and coal. This great power
of the engines is necessitated by the fact that she has to be driven
at a very high speed, at the same time she has a very great draught,
also the greatest facility of steering has to be attained; hence the
proportion of width to length, 25 to 70 feet. In order to save the
crew at the worst, a raft is constructed, which is also filled with a
mixture of cork and marine glue, and is placed near the helm. The mode
of operating with the _Uhlan_ is as follows:--

The dynamite torpedo is affixed to the point of the ram by the aid of
divers. The rudder is then fixed, and the crew opening a wide port on
the vessel's side, jump on the aforesaid raft. The steamer then rushes
forward, and explodes its torpedo in contact with the hostile vessel.
The crew hold on to the torpedo ship, and in case she is not injured
board her again and repeat the manoeuvre, if necessary.[M]

This is a novel form of torpedo boat, but does not seem to be a very
practicable method of torpedo attack.

_Admiral Porter's Torpedo Ship Alarm._--The _Alarm_ torpedo ship was
built from plans designed by Admiral David D. Porter, U.S.N. Her
total length, which includes a ram 32 feet long, is 172 feet; her
beam is 27 feet 6 inches, and her draught of water is 11 feet. She is
built of iron on the bracket plate system, that is to say, she has a
double hull, one shell being constructed inside the other. Her double
bottom is divided into a number of water-tight compartments. The whole
interior of the vessel is also built in compartments, which may be
hermetically closed, so that in case of both the shells being ruptured,
it would still be impossible to fill the entire ship with water. She is
steered by the same apparatus which propels her, viz. the Fowler wheel,
which is illustrated at Fig. 145.

This wheel turns on a vertical shaft, and its paddles are feathered by
an eccentric cam in such a manner that at one part of their revolution
they have a pushing and drawing action on the water, while at another
part they present only their edges. In fact it is simply a feathering
paddle wheel, turned horizontally instead of vertically. By suitably
turning the cam wheel, which is done from the helm, the feathering of
the paddles is caused to occur at different points; and in this way
the vessel may be turned, or rather her stern twisted around, as if
on a pivot. At the same time, by suitably adjusting the paddles, the
ship goes ahead, or astern, the engine meanwhile running in the same
direction.

By the apparatus above described it is considered that the _Alarm_ is
afforded not only a means of speed, but of being handled with the
utmost readiness, which latter is absolutely essential in such a
vessel, as she must always meet her antagonist bows on.

The steering is accomplished from the wheel house located aft on the
deck, or below deck, as all the appliances in the wheel house for
steering, &c., are duplicated below. By means of a hand lever beneath
the wheel, steam is admitted to a small auxiliary engine which works
the cam that adjusts the paddles. Then by turning the horizontal hand
wheel in either direction, the helmsman controls the movement of
the cam, as desired. Just above the wheel is a dial with a pointer,
which enables him to note the position of the paddles, and so adjust
them as ordered. Inside the wheel house there are also devices for
communicating with the men working the bow gun, and with those managing
the torpedoes.

_Her Armament--Engines._--At Fig. 146 is shown the spar and mode of
working it. It consists of a long hollow iron cylinder lying on its
supports between decks. Its outboard end rests in a kind of trough, and
to this extremity the torpedo is fixed. The spar is controlled by means
of tackles and a steam winch. The side spars are 18 feet, and the bow
spar 32 feet in length. If the hostile vessel is defended by torpedo
guards, by means of a mechanical contrivance the torpedo signals the
fact, and is not exploded until the vessel has forced the obstructions.
The engines of the _Alarm_ are compound, with four cylinders, the
condenser being placed between them. There are four cylindrical tubular
boilers with an aggregate heating surface of 4,600 square feet. Her
speed is about 16 knots. Her upper deck is only 3 feet above the water.
She is fitted with an electric light, and also with machine guns on her
broadside.[N]

This is undoubtedly a most formidable vessel, both as a ram and a
torpedo ship, and if capable of performing all that is expected of her,
will prove a valuable addition to the United States Navy.

[Illustration: THE "ALARM" TORPEDO SHIP.

PLATE XLV]

_Captain Ericsson's Torpedo Vessel "Destroyer."_--This torpedo vessel
was devised and built by Captain John Ericsson. The _Destroyer_ is
130 feet long, 11 feet deep, and 12 feet beam, extreme; both ends of
her hull are precisely alike, and terminate with very fine wedges.
The rudder is attached to a vertical wrought iron post welded to a
prolongation of the keel, just abaft the propeller, as shown at Fig.
147. The tillers consist of thin plates of iron riveted on opposite
sides of the rudder, a few inches from its bottom. These tillers are
operated by straight rods connected to the pistons of horizontal
hydraulic cylinders of 5 inches diameter, which are attached to the
sides of the keel. The steering gear by the above arrangement is placed
10 feet below the water line, while the top of the rudder is 6 feet
below the same, and thus perfect security is afforded to this most
important feature of a torpedo vessel. The intention of the designer
in constructing this vessel is to render her so far impregnable, that
in attacking bow on she can defy the opponent's fire, at the same
time offering absolute protection to her commander and steersman, and
also protecting the base of her funnel. The leading feature of the
construction of the hull of the _Destroyer_ is its being provided
with an intermediate curved deck, which extends from stem to stern,
and which is composed of plate iron strongly ribbed, and perfectly
water-tight. This intermediate deck supports a heavy solid armour
plate, fixed transversely to the line of keel, and 32 feet from the
bow, inclined at an angle of 45°, and supported on its after side by
a wood backing 4 feet 6 inches in thickness. Behind this formidable
shield the steering wheel is manipulated, a wire rope extending from
its barrel to a four-way cock placed near the stern, by means of which
water pressure is admitted alternately to the hydraulic cylinders,
previously mentioned, the motion of whose pistons actuate the rudder.
The lower division of the vessel is ventilated by powerful blowers, and
contains the machinery; it also affords a safe retreat for the crew
during the attack. The upper division is filled with blocks of cork,
excepting a small part near the bow, occupied by the aforesaid armour
plate and wood backing.

The deck house is 70 feet long, and composed of plate iron, riveted
water-tight to the upper part of the hull. As there are no openings in
the sides of this deck house, the vessel may be run with her upper deck
under water.

_Armament of the "Destroyer."_--The _Destroyer_ is to be armed with
torpedoes somewhat similar to the projectile torpedo, drawings of
which were submitted by Captain Ericsson, the inventor, to Emperor
Napoleon III. in 1854. The present weapon is composed of a solid block
of light wood, the explosive charge being contained in a metallic
vessel inserted at its forward end. Instead of being circular, as was
the case with the original torpedo, its transverse section is square,
with parallel top and bottom and vertical sides, forming very sharp
wedges at both ends, cased with steel plates. The extreme length of
the _Destroyer_ torpedo is 23 feet. Ignition is effected by means of a
percussion fuze placed in the head of the weapon.

_Operating the Torpedo._--The method of operating the torpedo is that
of inserting it into a horizontal tube near the bottom of the vessel,
provided with valves for keeping out the sea during the process of
insertion, as shown at Fig. 148. When near the hostile vessel, this
valve is opened, and the torpedo expelled by a piston actuated by steam
power, the expulsion being effected without recourse to gunpowder
or other explosive agent. The area of the actuating piston of the
_Destroyer_ is 314 square inches, while the sectional area of the
projectile is only 196 square inches; this difference in size of the
two areas is a special and important feature of the invention, as will
be understood from the following: the tension of the acting medium in
the _Destroyer_ exceeds 200 lbs. per square inch, therefore the torpedo
will be pushed out by a force of (314 × 200) / 196 = 320 lbs. per
square inch, and as the distance passed by the piston while impelling
the torpedo is 30 feet, an energy of nearly 2,000,000 foot-pounds will
be imparted to the projectile.

When making an attack, it is intended that the vessel should at the
instant of firing her torpedo reverse her engines, this retrograde
motion being greatly assisted by the recoil, which must attend the
discharge of a body weighing some 1,400 lbs. impelled by the aforesaid
enormous force, and moving through a distance of 30 feet before
reaching the water.[O]

Certainly this new system of submarine attack seems feasible, but it
has yet to prove, in common with all other new inventions, whether its
theoretical capabilities are also practical ones. At Fig. 149 is shown
a general view of this novel torpedo vessel under weigh.

[Illustration: THE "DESTROYER" TORPEDO SHIP.

PLATE XLVI]

_Torpedo Boats._--In offensive torpedo warfare, whether using the
spar, locomotive, or towing torpedo, especially in the case of the
former class of submarine weapons, to ensure a successful attack it
is absolutely essential to operate those weapons from steam boats,
which are capable of fulfilling as near as possible the conditions
herein enumerated:--

1.--They should be capable of steaming at least 18
knots per hour.

2.--Their engines should be noiseless, and easily
managed.

3.--They should be extremely handy.

4.--No smoke should enable their approach to be
detected, or glare from their fires.

5.--That it should be possible to raise steam in them
in a few minutes.

6.--They should be built in water-tight compartments,
and covered fore and aft to prevent being swamped.

7.--The crews should be protected as far as practicable
from rifle fire.

In addition to the foregoing, for the purpose of rendering these craft
capable of defending themselves against the attack of guard boats, and
also of being employed as such, and on river expeditions, &c., they
should be built sufficiently strong to enable them to carry a small gun
either in the bows or stern; this would apply more especially to those
torpedo boats which are part of a ship's stores.

During the last four years a very large number of torpedo boats have
been built, which more or less fulfil the aforesaid conditions, nearly
the whole of which have been constructed by the two English firms, viz.
Messrs. Thornycroft and Co. and Messrs. Yarrow and Co., and to the
latter firm is due the honour of constructing the fastest vessel as yet
in the world.

Up to the present time, a specially built torpedo boat has on only one
occasion been used on active service, viz. at the attack on a Turkish
monitor on the 20th of June, 1877, which is detailed at length in the
following chapter. This boat was one of Messrs. Thornycroft and Co.'s
launches, and from all accounts she behaved wonderfully well under the
most untoward circumstances.

_Thornycroft Torpedo Launches._--Messrs. Thornycroft and Co., of
Chiswick, London, have during the last six years built a large number
of torpedo launches for the English government and for several of the
principal European governments.

_Norwegian Launch._--The first torpedo boat ever built by this firm was
the one shown at Fig. 150, for the Norwegian government. This boat was
57 feet in length by 7 feet 6 inches beam, drew 3 feet of water, and
the stipulated speed was 16 English statute miles, or nearly 14 knots
per hour; which speed was not to be ascertained by a mere measured mile
trial, but was to be 16 miles through the water in a run of one hour's
duration.

The hull of the vessel was constructed entirely of steel plates and
angle bars, and, as may be seen from the diagram, was divided into six
water-tight compartments, _A_, _B_, _C_, _D_, _E_, _F_.

The compartments marked _A_ and _F_ in the stem and stern were for
stores; those marked _B_ and _E_ were fitted with seats for the crew,
and were provided with movable steel covers, so that on going into
action, or during rough weather, they might be completely covered.

The compartments _C_ and _D_ are for the steersman and the machinery
respectively, and were covered completely by steel plating 3/16 of
an inch in thickness--a thickness sufficient to withstand Snider or
Martini-Henry bullets, fired from a distance of twenty paces.

The compartment _D_ was furnished with a hood, having slits 1/4 of
an inch wide, all round, through which the steersman could see with
sufficient distinctness to direct his course easily. Motion was
communicated from the wheel to the tiller by means of steel wire ropes,
which it was originally intended should be encased in wrought iron
tubes.

The possibility however of these tubes being bent by a shot, and so
jamming the wire ropes, led to this arrangement being abandoned, and
the ropes were simply run through eyes at intervals along the side.

The armament consisted of a cylindro-conical shaped torpedo towed from
the top of the funnel, round which a ring was fitted with two pulleys
for the towing rope, the strain being taken off by means of two stays
attached forward.

The length of this torpedo was 13 feet and the diameter 9 inches, and
with a speed of 11 knots it has diverged to about 40 degrees from the
direction of the boat's motion when running in smooth water.

The torpedo is worked by means of a small winch and brake fixed on
the after part of the engine room skylight; davits are provided for
dropping the torpedo overboard.

The engines were compound, of the usual inverted double cylinder direct
acting type, capable of developing about 90 indicated horse power, and
were fitted with a surface condenser, so that the vessel could run in
salt water, without danger of injuring her boiler.

A small tank contained a supply of fresh water, to make good
deficiencies arising through leakage, and from steam escaping at the
safety valves, &c.

The circulating, air, and feed pumps were driven by a separate engine.

The boiler was of the locomotive type, the shell being made of Bessemer
steel; the fire box and its stays of copper, and the tubes of solid
drawn brass.

On the official trial, which took place on the Thames on the 17th of
October, 1873, the number of revolutions done in the hour was found
to be 27,177, and the number required to do a mile in still water was
1578. The distance run in the hour was then, 27,177/1578 = 17·22, or
very nearly 17-1/4 miles.

The steam pressure during the trial averaged 85 lbs. per square inch,
and the vacuum 25-1/2 inches.

_Swedish and Danish Boats._--Boats of the same size and similar in all
particulars to the foregoing one--excepting the engines, which are
improved by driving the air pump, feed pump, and circulating pumps off
the main engines, and abolishing the auxiliary engine, which performed
these duties in the case of the Norwegian boat--were made for the
Swedish and Danish governments. The result was an increase of speed to
17·27 miles in the case of the Swedish boat, and to 18·06 miles, or
15-5/8 knots, in the case of the Danish boat.

There is no information regarding the armament of the Swedish boat, but
the Danish boat was armed with two spindle-shaped torpedoes 12 feet
long and 11-1/2 inches diameter, somewhat like the Whitehead torpedo.
They were placed on deck longitudinally near the funnel, so as to
facilitate launching, and were arranged to be towed from an upright
pole 8 feet high, placed about 6 feet from the stem.

A small winch was fixed on either side aft, to pay out the towing line,
and to bring back the torpedo. By these arrangements the torpedo could
be projected at a large angle from the direction of the boat's motion,
and at considerable velocity. The speed of the boat when towing one of
these torpedoes is about 10 knots.

_Austrian and French Boats._--The next size of torpedo vessel is that
supplied to the Austrian and French governments, which is shown at
Fig. 151. The dimensions are:--length, 67 feet; beam, 8 feet 6 inches;
draught of water, 4 feet 3 inches. The guaranteed speed in the case of
the Austrian boat was 15 knots in a run of one hour's duration, and in
the case of the French boats 18 knots, in a run of two hours' duration.
These boats were built of somewhat thicker plating than the 57 feet
type, and the armour was extended.

They were divided into six water-tight compartments, and they differed
from the Scandinavian boats in having the spaces forward and aft of the
machinery permanently decked, instead of being covered with movable
steel covers only.

The machinery was somewhat similar to that in the Scandinavian boats,
excepting that the engines were capable of developing 200 indicated
horse power, and that the air was supplied to the furnace by being
forced into an air-tight stoke hole, instead of being forced directly
under the fire grate.

The armament of these vessels consisted of two torpedoes attached to
the end of wooden poles, 4-1/2 inches diameter and about 43 feet long,
connected to the battery by insulated wires, and arranged to be fired
either by coming in contact with the enemy's vessel or at any distance
from it, at the will of the operator.

The torpedoes themselves were simply copper cases, of sufficient size,
in the case of the Austrian boat, to contain 11,000 cubic centimetres
of explosive, and in the case of the French boats, to contain 25
kilogrammes of dynamite.

The mode of arranging the wires is similar to that explained at page
155. The method of manipulating the torpedo poles consists of two tubes
riveted together at right angles, so as to form something like the
letter T. The torpedo pole is put through the horizontal tube, which is
free to move round the centre of the vertical tube, and the vertical
tube is free to move through a quarter circle at right angles to the
centre line of the vessel.

In attacking in front, the vertical tube is laid over till it is
parallel to the water surface, and the horizontal tube is allowed to
incline sufficiently far to allow of the end of the pole, when run out,
to be depressed from 8 to 10 feet below the water-line. It is held in
this position by a pair of blocks attached to the top of a short mast.

In attacking on the broadside, the vertical tube is laid over till it
assumes a position such as to allow of the pole, when swung round, to
touch an enemy's vessel at about 8 or 10 feet below the water line.

The speed trials of the Austrian boat took place on the 11th of
September, 1875, when she did 24,700 revolutions on her hour's run
on the Thames, and the number of revolutions required to do a knot
in still water was found to be 1357. This gives the distance run in
the hour as 18·202 knots, or 3·202 knots over the contract speed. The
steam pressure averaged 105 lbs. per square inch, and the vacuum 25-1/2
inches during the run.

In the case of the French boats, the total number of revolutions done
in the two hours' run in the roadstead off Cherbourg was 49,818, and
the number required to do a knot in still water was found to be 1382,
so that the distance run in the two hours was 36·05 knots, or just over
the contract speed. During the two hours, the average steam pressure
was 108 lbs. per square inch, and the vacuum 25 inches.

The Austrian boat was sent to her destination on board a steamer, but
the French boats, under the command of an experienced captain, steamed
by themselves from Chiswick to Cherbourg, not crossing at the nearest
points and running along the shore, but going boldly from Dover direct
to Cherbourg.

Shortly after the arrival of the French boats in Cherbourg, they were
altered so as to attack in front only, as the French authorities found
that these small vessels were better adapted for resisting the effects
of an explosion at the bow than at any other part.

The arrangement adopted is shown at Fig. 152, and consisted of a steel
pole about 40 feet in length, having one end about 6 inches diameter,
and solid, and the other about 1-1/2 inches diameter, and hollow; this
pole was mounted at its solid end on small pulleys, which ran upon two
ropes stretched fore and aft of the vessel; the other end, to which
the torpedo was attached, was led over a pulley fixed on the bow.
Ropes passing over pulleys to a windlass in the after compartment were
attached to the inboard end, and by turning the windlass the pole was
drawn backwards or forwards as required.

It will be observed that as the pole is drawn forward, the inboard end
being constrained to move in a line parallel to the deck, the outer end
is depressed in the water, and is so adjusted that when the pole is run
out to its full extremity, the torpedo is depressed to about 8-1/2 feet
below the water level.

_Dutch and Italian Boats._--The third size of boat built by this
firm for the Dutch and Italian governments are 76 feet long and 10
feet beam, and are guaranteed to do a speed of 18 knots. These boats
are similar in design to the Austrian and French boats previously
described, but differ from them in having engines of 250 indicated
horse power, and in having more free board forward, so as to make them
better sea boats.

The Dutch type are armed with the outrigger torpedo, as fitted to the
French boats, and the Italian type with the Whitehead fish torpedo.

_The "Lightning" Type of Boat._--Now comes the _Lightning_ type of
vessel, which is shown at Fig. 153. This vessel, built for the English
government, is 84 feet long over all, 10 feet 10 inches beam, and
draws about 5 feet of water. The machinery on board the _Lightning_
is similar in design to that already described, and is capable of
indicating 350 horse power. The hull of the _Lightning_ is made of
heavier plating than usually employed, and her lines are fuller, as
she is intended for use in a tolerably rough sea if necessary; and
in order that she may be able to remain at sea for some time, cabin
accommodation on a scale larger than in any of the other boats is
provided for the officers and crew. The steering gear is arranged so
that the vessel may be steered from the deck, or from the conning
tower, and the usual telegraph gear is fitted to communicate from the
deck, or from the conning tower, to the engine room.

The top of the conning tower is supported on three screws, so arranged
that it may be raised or lowered, and the space for sight adjusted
according to the range of vision required, or the risk to be run from
the enemy's missiles.

The _Lightning_ is armed with fish torpedoes, which are discharged from
her deck forward by means of a discharging apparatus.

The torpedoes are charged with air, by means of one of Mr.
Brotherhood's air-compressing pumps.

The _Lightning_ on her preliminary runs attained a speed on the
measured mile of 19·4 knots per hour, a speed which will be somewhat
reduced when she has her torpedoes, &c., on board, but which will then
be over 18 knots per hour.

Several torpedo boats have been built and are in process of
construction by this firm for the English government.

[Illustration: THORNYCROFT'S TORPEDO BOATS.

PLATE XLVII]

_French Boats._--The next size of boats is the 87 feet type, as shown
at Fig. 154. Of this type of torpedo launch several have been built and
are now under construction for the French government.

These vessels are 10 feet 6 inches beam; draught of water about 5
feet. They are built of heavier plating than the _Lightning_, and are
guaranteed to maintain a speed of 18 knots. The propellers in these
boats are placed in front of the rudder, so as to give increased
readiness in steering. In order to prevent oxidation as far as
possible, the plates and frames below the water line are galvanised. A
spark-catching apparatus is fitted to the base of the funnel, so as to
prevent the position of the boat being betrayed to the enemy at night.

The armament of these vessels consist of an outrigger arrangement
similar to that described at page 167. They are also well adapted for
the Whitehead torpedo. They are also provided with a strong buffer in
the bows for deadening the shock, in the event of their coming into
contact with an enemy's vessel at too high a rate of speed.

_"Second Class" Boats and Mode of Manipulating the Fish Torpedoes
from them._--Another type of Thornycroft torpedo boats, several of
which have been built for continental governments, and which is termed
"Second class," is shown at Fig. 155. These boats are 60 feet long, 7
feet 6 inches beam, and draw some 3 feet of water; their guaranteed
speed being 16 knots per hour. The mode of carrying the Whitehead fish
torpedo, and manipulating it from such a boat by means of Mr. J. I.
Thornycroft's invention, which has been fully described at page 140, is
shown at Figs. 155 and 156, where Fig. 155 represents both torpedoes
housed, and Fig. 156 one torpedo in the firing position, the other one
being housed.

Four of this type of Thornycroft torpedo boats were attached to H.M.S.
_Hecla_ during her recent cruise in the Mediterranean, and have been
very favourably reported on as follows:--They do not suffer from the
blows of the sea, nor from the strains incident upon hoisting in and
out; nor yet when they are suspended ready for lowering, in which
latter position they have frequently remained for twenty-four hours;
that under careful management they are perfectly safe in a heavy sea,
and they possess good manoeuvring powers.

The Thornycroft torpedo frames were found to perform well the services
for which they are intended. When proceeding at ordinary speed they
are nearly noiseless, and cannot be seen on a dark night at a distance
of 100 yards.

_The Thornycroft Propeller._--All the torpedo boats built by this firm
are fitted with the propeller invented by Mr. Thornycroft, and which
bears his name. It is a modification of what is known as the Dundonald
propeller, the principal difference being that in the Dundonald
propeller the blades are inclined backward in straight lines, while in
the Thornycroft propeller they are curved.

_Experiment at Cherbourg._--The following account of an experiment
which took place at Cherbourg in March 1877, whereby to test the
efficiency of a Thornycroft torpedo boat in exploding a spar torpedo
under the bottom of a vessel proceeding ahead at the time, is taken
from the _Times_, under date the 13th of March, 1877.

[Illustration: THORNYCROFT'S TORPEDO BOATS.

PLATE XLVIII]

"Admiral Jaurez, who commands the squadron, ordered a disabled ship,
the _Bayonnaise_, during a rather rough sea, to be towed out by a
steamer belonging to the navy. A second lieutenant, M. Lemoinne, was
sent for, and informed that he had been selected to make the experiment
of launching the Thornycroft against the _Bayonnaise_ while both were
in full sail. He accepted the mission without hesitation, picked out
two engine men and a pilot, and went down with them into the interior
of the Thornycroft, of which only a small part was above water; this
visible portion being painted of a greyish colour, so as to be easily
confused with the sea. The torpedo was placed so as to project from
the bow of the vessel, at the extremity of which were two lateen
sailyards about three metres in length. The towing steamer then took
up its position in front of the squadron, and the Thornycroft also
assumed the position assigned for it; an interval of three or four
marine miles separating the torpedo boat and the _Bayonnaise_. On a
signal being given, both were set in motion, the steamer advancing
in a straight line, and the Thornycroft obliquely, so as to take the
_Bayonnaise_ in flank. The steam tug went at 14 knots an hour, going at
full speed in order to escape the Thornycroft. The latter went at 19
knots an hour, a rate not attained by any vessel in the squadron. The
chase lasted about an hour, the squadron keeping in the rear, so as to
witness the operations. At the end of that time the distance between
the Thornycroft and the _Bayonnaise_ had sensibly diminished, and at
a given moment the former, in order to come up with the latter at the
requisite distance, had to slacken speed to 8 knots an hour. The
whole squadron watched this last phase of the struggle with breathless
interest, and people asked themselves whether the shock of the torpedo
would not infallibly destroy the little vessel which bore it. It was
feared that the lives of the second lieutenant, Lemoinne, and his
three companions were absolutely sacrificed. However, the two vessels
got visibly nearer. All at once the Thornycroft put on a last spurt,
and struck the _Bayonnaise_ with its whole force on the starboard
bow. The sea was terribly agitated, a deafening report was heard, and
the _Bayonnaise_, with a rent as big as a house, sank with wonderful
rapidity. As for the Thornycroft, rebounding by the shock about fifteen
metres off, even before the explosion occurred, it went round and round
for a few moments, and quietly resumed the direction of the squadron.
No trace remained of the _Bayonnaise_; it was literally swallowed up by
the sea."

The experiment was a most complete success, the torpedo boat not being
in the least degree injured.

_The Power of Flotation of a Thornycroft Boat after being pierced by
a Rifle Shot._--On the 5th of July, 1877, Messrs. Thornycroft and Co.
made an experiment with one of their torpedo boats to ascertain under
what conditions flotation is still retained after the boat has been
pierced by a rifle shot.

The torpedo boat experimented on was similar to the one which has been
described at page 169. A Martini-Henry was fired through her side,
about a foot under water in the stoke hole. Whilst at anchor the water
entered in sufficient quantity to fill an ordinary size bucket in
twenty-five seconds, but when she was driven ahead less water entered,
and on the speed of 10 knots being reached, little or no water entered.
The hole was a little more than three quarters of an inch in diameter.

The engagement on the Danube between the torpedo boat _Schootka_
and some Turkish vessels, in which the former vessel was pierced by
bullets, but yet did not sink, led to the above experiment being
carried out.

_Efficiency of Thornycroft's Engines._--As a practical proof of the
efficiency of the engines supplied by Messrs. Thornycroft and Co.
to their torpedo boats, a similar engine has been used for over two
years to work the various machines in connection with their works at
Chiswick.

_Torpedo Boats built by Messrs. Yarrow and Co._--Messrs. Yarrow and
Co., of the Isle of Dogs, London, are also very well-known torpedo
boat builders, and have during the last four years constructed a
considerable number of such vessels for the English and different
continental governments, and, as has been before stated, they are the
constructors of the fastest vessel in the world.

_Dutch Torpedo Launch._--In 1875 this firm built a torpedo launch for
the Dutch government, specially designed for ocean purposes. It was 66
feet long, 10 feet beam, and 5-1/2 feet deep. She was driven by a pair
of inverted direct acting engines. The boiler was of the locomotive
type, with a working pressure of 140 lbs. per square inch, and capable
of exerting a force of some 200 indicated horses.

_Russian Torpedo Boat._--This firm also constructed for the Russian
government two torpedo steamers 85 feet in length. The guaranteed
speed of these vessels being 20 knots per hour. In 1878 the Russian
government ordered one hundred exactly similar boats to be constructed,
mostly at St. Petersburg, thus proving the high estimation held by that
government of Messrs. Yarrow and Co.'s torpedo boats.

_Description of a Yarrow Torpedo Launch._--Figs. 157, 158, and 159 show
an elevation, section, and plan of a torpedo boat, Yarrow type, a large
number of which have been built for the Russian and other continental
governments.

The length of this boat is 75 feet, its beam 10 feet, and draught of
water 3 feet. She is built of steel of the best quality, no other
metal possessing the requisite strength and stiffness for scantling,
and plates of such lightness. It is divided into eight compartments by
seven transverse bulkheads, the forward and after compartments being
used for stores, the two central ones enclosing the machinery, while
the steersman and operator are placed in the compartment immediately
abaft the engines.

The steersman's head projects above the deck, and is protected by a
rifle proof steel truncated cone, the top part of which is movable like
the visor of a helmet. The hull is decked over from end to end with a
curved shield, the midship plating of which is capable of resisting
rifle shots, even at close quarters; its curved form being well adapted
for giving the maximum strength to the structure, and quickly frees
itself from any large body of water.

[Illustration: YARROW'S TORPEDO BOATS.

PLATE XLIX]

The propelling machinery consists of a pair of inverted compound
condensing engines. The revolutions per minute at full speed are about
470, and the indicated horse power about 280. The propeller is of
steel. The funnel is fixed at one side of the centre line, to be out of
the way of the bow torpedo pole and gear.

This type of torpedo boat attains a speed of from 17-1/2 to 18-1/2
knots per hour.

The armament of some of these boats consists of three spar torpedoes, a
bow, and two quarter ones. The bow pole, which is strong and heavy, is
hauled out and in by means of a small auxiliary engine.

Boats similar to these, but of larger dimensions, viz. 84 feet long and
11 feet beam, have also been constructed by this firm. Speed from 19 to
20 knots per hour.

_English Torpedo Boats._--The following account of two torpedo
boats which had been originally built by this firm for the Russian
government, but, owing to the proclamation issued by the English
government at this time prohibiting torpedo boats leaving England, were
seized by the Customs authorities when on the point of completion, and
were ultimately purchased by the English government, is an extract from
the _Times_ under date the 4th of July, 1878.

"These vessels are each 85 feet long with 11 feet beam, and draw,
when fully equipped for service, an average of 3 feet of water. They
are strongly constructed of steel, and are fitted with compound
surface condensing engines capable of indicating 420 horse power. The
high pressure steam cylinder of these engines is 12-1/2 inches in
diameter, and the low pressure 21-1/2 inches, both having a 12 inch
stroke. These boats are at present known by their builders' numbers,
one being No. 419 and the other No. 420. The former is propelled by a
three-bladed screw, 5 feet 6 inches diameter and 5 feet pitch; and the
latter by a two-bladed screw of similar proportions. Messrs. Yarrow
adopt supplementary engines for driving the air pump, circulating
pump, and feed pumps; they consider this plan preferable to that of
working these pumps direct off the main engine, as is sometimes done.
One advantage in having separate pumping engines is that, whether the
vessel is in motion or stationary, a powerful means is available for
pumping her out, should the necessity arise. It is estimated by her
builders that if the air pump and circulating pump were both utilised
for this purpose, the water could be pumped out as fast as it could
enter either of these vessels through one hundred holes made in the
skin by Martini-Henry rifle bullets. If this is the case, these craft
may be deemed safe from sinking so long as their machinery is working
efficiently. The boiler is of the locomotive type, placed in the
forward part of each vessel, and has a closed stoke hole. In connection
with the boiler a very important improvement has been introduced by
Messrs. Yarrow. This consists in a means of rendering the closed
stoke hole safe for the men in the event of the collapse of a boiler
tube--a contingency which cannot be absolutely guarded against. Its
efficiency was proved beyond all question upon a previous trial of
one of these boats. This was No. 419, which was tried on the 24th of
May last under the supervision of the Admiralty officials. Upon that
occasion an accidental rupture of one of the boiler tubes occurred
nearly at the close of the runs over the measured mile, which so far
had been very successful. When the boiler tube gave way the steam
rushed out of the foremost hatchway from the compartment in which the
smoke box end of the boiler is situated, and soon after from the two
funnels. The men in the stoke hole, however, being shut off from the
boiler, were uninjured, and remained at their post several minutes
after the first outburst of steam. The accident, although an untoward
event, was considered by the Admiralty officials as affording a highly
satisfactory proof of the efficiency of Mr. Yarrow's invention.

"The engines are placed amidships, and each vessel has spacious cabin
accommodation aft, as it is intended that they may be used either as
despatch or torpedo boats. For the latter purpose the cabin framings
above deck are removed and replaced by steel plating. They are steered
from the cabin, there being a look-out for the steersman just above
deck level. The deck is clear of all obstructions, the two funnels
being placed one on either side. They are fitted with balanced rudders
and steer well, answering their helms very quickly."

The trials of these two torpedo boats are taken from the _Engineer_
under date the 19th of July, 1878. At that time these boats completely
eclipsed in speed everything that had hitherto been done. At Fig. 160
is shown in elevation this type of torpedo launch.

"The trials were personally conducted by Mr. Yarrow, under the
superintendence of the authorities from Whitehall, and consisted in
a two hours' run without stopping, during which time the boats were
tested at the measured mile at Long Reach. Each boat was run six times
over the mile, three runs with the tide and three runs against it. The
boats and machinery are similar in every respect, excepting that No.
419 is fitted with a three-bladed propeller, and No. 420 a two-bladed
one, their diameters and pitch being the same in both cases. The
weights on board were accurately weighed, and amounted to 6 tons in
each boat, including coals, water, crew, and ballast.

"_Trial of No. 419._

Min. Sec. Knots per hour.

1st run down occupied 2 36 23·076
1st run up " 3 20 18·000
2nd run down " 2 35 23·226
2nd run up " 3 16 18·367
3rd run down " 2 32 23·684
3rd run up " 3 14 18·557
Mean of the six runs, 20·818 knots per hour.
Mean steam pressure, 115 lbs. per square inch.
Vacuum, 23-1/2 inches.
Mean revolutions of main engines per minute, 456.

"_Trial of No. 420._

Min. Sec. Knots per hour.

1st run down occupied 2 33-1/2 23·452
1st run up " 3 25-1/2 17·518
2nd run down " 2 32-1/2 23·606
2nd run up " 3 21 17·910
3rd run down " 2 32 23·684
3rd run up " 3 24 17·647
Mean of the six runs, 20·636 knots per hour.
Mean steam pressure, 115 lbs. per square inch.
Vacuum, 24 inches.
Mean revolutions per minute, 466.

"The highest speeds were obtained by No. 419, during the third runs up
and down, the mean of which give 21·12 knots, which is equal to 24-1/3
statute miles per hour, during which time the engines were making 470
revolutions per minute. At the close of the runs, the bearings were
found to be in first-class condition, and there was not the least sign
of anything getting warm during any part of the trials."

_Spanish Torpedo Boat._--The following description of a torpedo boat
built by this firm for the Spanish government, enumerating all the
improvements that have of late been effected in the construction of
such vessels by members of this firm, is taken from the _Engineering_
under date the 21st of February, 1879.

"The alterations have a twofold character, and have reference to the
arrangements for discharging the products of combustion from the
furnaces and to those for steering the vessel. In brief, the boat is
funnelless and is fitted with two rudders, one at each end. The main
object in dispensing with the funnel is to enable the torpedo boat
to approach as closely as possible to an enemy without being seen,
a secondary, although still an important, consideration, being the
absence of any obstruction to the steersman's view, such as a funnel on
deck. The outlets for the smoke in the present instance are two ports,
one on either side of the vessel, and placed about 15 feet in from the
bow. Each of these smoke ports is fitted with a damper, and the smoke
can be turned through either or both of the passages as desired. The
control of these dampers is given to the steersman, who, on approaching
an enemy, can direct the products of combustion through the port on
the unexposed side of the vessel. The emission of smoke by day and of
the glare and sparks by night are thus to a very large extent hidden
from view, thus enabling the torpedo boat to approach very closely to
the point of attack without being observed. The outlets are fitted
with valves which are kept open by the blast, but which close on being
struck by a passing wave. Should the vessel have to be out when a heavy
sea is running the ports are closed, and a spare funnel is rigged up on
deck, on one side. Although the smoke ports are placed forward in this
boat, it is intended to place them aft in the next that Messrs. Yarrow
build, as that arrangement will obviate the inconvenience at present
experienced by those on deck from the heated gases of the furnace being
carried along it at times by the wind, when on a certain course.

[Illustration: YARROW'S TORPEDO BOATS.

PLATE L]

"The steering powers of the boat have next had attention from Messrs.
Yarrow, and they have sought to remedy the defective steering common to
these large quick-speed torpedo craft. To do this they have fitted the
vessel under notice with two balanced rudders, one of which is placed
forward about 10 feet from the bow, and the other in its usual position
at the stern with the screw abaft it. Both rudders are connected
with the same steering gear, and are operated simultaneously by one
steersman. The forward rudder can be raised out of the water into a
casing inside the boat if desired by means of a screw cut on the upper
part of its spindle. By the same means, by unscrewing the collar on the
spindle, the rudder can be released and dropped into the water should
the necessity arise for so doing, by reason of its becoming fouled or
damaged. In trials which have been made with this double-steering
system, it has been found that when steaming at high speeds the forward
rudder has a much greater control over the motion of the boat than the
stern one. The reason assigned for this is that at high speeds the
forward part of the boat is lifted out of the water, and consequently
offers a diminished side resistance to any turning motion brought to
bear upon it.

"The boat in which these improvements have been introduced is 86 feet
long by 11 feet beam and 5 feet 6 inches deep. She is fitted with
compound engines having 22 inch and 12-1/2 inch cylinders, with a 12
inch stroke, and making 520 revolutions per minute when running at full
speed. She is propelled by a three-bladed screw 5 feet 6 inches in
diameter and 5 feet pitch. Put through some evolutions with the view of
testing her steering powers, the double rudder arrangement was found to
answer exceedingly well, and she turned a circle of a diameter equal
to about three times her own length in 1 minute 15 seconds. She turned
equally well either going ahead or astern, and in fact her steering
capabilities were satisfactorily demonstrated. The new arrangement for
carrying off the smoke also answered very well, with the exception
that the heated gases occasionally swept the deck, which objectionable
result will be avoided in future boats."

These boats are to be armed with spar torpedoes, and with the Whitehead
fish torpedo, the cradles and fittings for which are shown at Fig. 161.

_The Fastest Vessel in the World._--Another type of torpedo boat, of
which one of the same dimensions has been built by this firm for the
English government, is shown at Fig. 162. This vessel is as yet the
fastest vessel in the world. The trials with this boat were made in
March of this year, and were as follows:--

Runs. Time, Knots Knots
Min. sec. per hour. per hour.

First 2 37 = 22·93}
Second 3 2 = 19·78} Mean of first pair = 21·35

Third 2 33 = 23·53}
Fourth 2 55 = 20·57} Mean of second pair = 22·05

Fifth 2 30 = 24·00}
Sixth 2 56 = 20·45} Mean of third pair = 22·23

giving as a mean 21·93 knots per hour, or 25-1/4 statute miles. The
boat was fully equipped for active service, i.e. with a load of 6-3/4
tons on board. It was found during the trial that at speeds of 17 and
19 knots the vibration of the boat was considerable, but when running
over 20 knots it was hardly perceptible; the excessive vibration taking
place when the revolutions of the engines became a multiple of the
natural vibration of the boat.

Torpedo boats are at the present time being built by this firm for the
English, French, Spanish, Austrian, and Italian governments.

_Russian Torpedo Boats, built by Mr. S. Schibau, Prussia._--Mr. S.
Schibau, of Elbing, Eastern Prussia, in 1878 constructed ten torpedo
boats for the Russian government, similar to the one shown at Fig 163.

These boats are each 66 feet long, and 11 feet 3 inches beam. They are
built of steel plates about an eighth of an inch thick. Their engines
consist of three cylinder compounds, with surface condensers; and they
run at 380 revolutions per minute, at full speed, driving a screw 4
feet in diameter. They have been variously armed, some with the spar,
some with the Whitehead fish, and some with the Harvey towing torpedo.
Their speed is about 18 knots per hour.

_Messrs. Herreshoff's Torpedo._--Messrs. Herreshoff, of Rhode Island,
U.S.A., have also constructed several torpedo boats. One of these,
built for the English government, is shown in section at Fig. 164.
This boat is 59 feet 6 inches long, 7 feet 6 inches beam, and 5 feet 6
inches deep; she draws about 1 foot 3 inches of water.

[Illustration: RUSSIAN TORPEDO BOAT, HERRESHOFF'S TORPEDO BOAT.

PLATE LI]

"The vessel is constructed with five water-tight bulkheads, and her
hull is of composite construction below the water line, having a
steel framing covered with wood planking. The upper part of the hull
is wholly of steel, the plates being 1/16 inch thick, the top sides
sloping inwards and the upper work forming a protective superstructure
for the crew and machinery. She is propelled by a screw which is placed
beneath the vessel in a central position, and which is driven by a
direct acting condensing engine placed in the forward part of the boat.
The diameters of the steam cylinders are 10-1/2 inches and 6 inches
respectively, with 10 inch stroke, and they are of 100 horse power
estimated. There is an independent feed pump and air pump. The stoke
hold is enclosed and is supplied with air by a Sturtevant blower, which
is driven by an independent engine of 2-1/2 horse power. The propeller
is a two-bladed screw 38 inches in diameter and 5 feet pitch, the
screw shaft being 23 feet in length. The vessel is steered by means
of a balanced rudder placed a short distance from the stern and under
the ship, the helmsman being located in a stern cabin with a protected
look-out raised just above the deck. The hull and machinery together
weigh 6 tons, but with the working crew of four men and fuel, stores,
and two torpedoes on board, boat weighs about 7-1/2 tons.

"Steam is supplied by a Herreshoff coil boiler, which constitutes
another novelty in this boat. This boiler consists of a circular
combustion chamber, which in the present instance is 4 feet in diameter
internally, and within which is a coil of about 300 feet of 2 inch pipe
coiled to nearly the diameter of the chamber. This coil is continued at
the top so as to form a kind of dome under the cover of the combustion
chamber. By the side of the boiler is a separator, into which the
steam passes before it goes to the engine. The water from the feed
pump is admitted at the top of the coil, and during its course to the
bottom the greater portion of it becomes converted into steam. Having
passed through the entire length of the coil, the steam and water are
discharged together into the separator in such a manner that the water
is entirely separated from the steam, and can be blown off as required.
The steam is taken from the top of the separator, and returns through
a short coil placed inside the combustion chamber, where it becomes
superheated, and is led thence to the engines. It is claimed for this
boiler that it cannot explode destructively, inasmuch as there is
but a very small quantity of water in it at any time, and that it is
distributed along the entire length of the coil. A rupture at any point
would only be attended by a moderate blowing off of steam. The rapid
circulation of the water is found to prevent the deposit of salts, the
surplus water not converted into steam carrying with it all impurities.
A good working pressure can be obtained within a few minutes of
lighting the fire, and the boiler can be blown off in a few seconds.
The large combustion chamber enables the full economy of the fuel to be
realised."[P]

This vessel is guaranteed for a speed of 16 knots per hour. She can
be propelled ahead or astern with equal speed, and can be brought to
a dead stop when going full speed within a distance equal to her own
length. Her turning powers are equally good. Her armament will probably
be the fish torpedo.

_Ordinary Torpedo Boat._--The most efficient and simple method of
fitting and working a spar torpedo from an ordinary steam launch or
pinnace is shown at Fig. 165. This method will be readily understood
from the figure; the dotted lines show the position of the spar and
upright, when rigged in. The speed of this type of torpedo boat ranges
from 6 to 9 knots. Occasions would no doubt occur in time of war when a
torpedo attack by such boats would be a feasible matter, and therefore
everything should be done to render these boats fit for that special
service.

_Defects._--The most important defects of such craft are:--

1.--The noise created by their engines, thus
rendering an undetected approach to a hostile vessel
impracticable.

2.--Their liability to be swamped by the explosion of
the torpedo.

Of course there are many minor defects, but above are the principal
ones, both of which might, to a considerable extent, be modified.

_Torpedo Boat Attacks._--It is impossible to attempt more than a
very general idea of how to conduct a torpedo boat attack, as so
much depends upon the circumstances, ever changing, under which each
particular attack would have to operate.

The spar and the fish torpedo are the submarine weapons that can best
be manipulated from boats, the towing torpedo requiring a more roomy
craft than the torpedo boat generally is to operate it from with any
chance of success.

_Methods of Protecting Ships from Boat Torpedo Attacks._--The principal
methods that exist at the present time of protecting a ship from a boat
torpedo attack are as follows:--

1.--Booms by themselves, or supporting nets hung
vertically, surrounding the ship at a distance of 10 or
15 feet from the side of the vessel.

2.--A crinoline of wire, or chain, fixed by stays to
the vessel's side, but capable of being lifted out of
the water if required.

3.--The above methods supplemented by guard boats, and
a cordon of boats.

4.--A cordon of boats, that is, boats connected at
certain distances by means of hawsers, or chain cables,
and at a distance of some 200 or 300 yards from the
vessel, supplemented by guard boats, but without other
protection.

5.--Electric lights and torpedo guns. These latter are
small guns capable of penetrating the side of a torpedo
boat and of being depressed at a very small angle.

As it is against these defences that torpedo boats would have to
contend, therefore they have been described previous to explaining the
mode of conducting a torpedo boat attack.

The first two methods of defence are of course quite impracticable when
the attacked vessel is one of a blockading squadron, and it is against
such vessels that a torpedo boat attack will generally be used and
oftenest be successful.

In the case of a vessel forced to anchor in a harbour which is
accessible to the torpedo boats of the enemy, by the application of
either of the first two methods, supplemented by guard boats and
electric lights, she would undoubtedly be almost impregnable against a
torpedo boat attack, even were the boats armed with the fish torpedo,
though she would of course not be in that state of readiness which
is essential to a man-of-war's efficiency. As a general rule, no
man-of-war should anchor unless absolutely necessary in the vicinity
of an enemy's ports, and then should retain the power of moving in any
direction in the quickest space of time possible, using the electric
light and guard boats as a means of protection.

An attack by boats armed with the spar torpedo must always partake of
the nature of a forlorn hope, this especially applying to the boats
themselves, the crews of which, provided they are supplied with good
life belts, would seem to run a far greater risk of a wetting and a
prison than of being shot.

Not less than four torpedo boats should compose the attacking force.
The crews of the boats, consisting of only those actually required,
should fully understand "_that the hostile vessel is to be torpedoed_,"
i.e. they are not to give up the attack on the vessel opening fire,
nor in the case of one or more of the torpedo boats being sunk, but
to remember that one boat is sufficient to effectually carry out the
object of the attack, viz. the sinking of the ship.

In making the attack, one boat should be directed on each bow, and
one on each quarter, the final rush being as combined as possible.
There must not be the _slightest hesitation_, and each boat must make
_direct_ for her point of attack.

The cause of the Russians failing so often in their torpedo boat
attacks during the war of '77 may be traced to the absence of anything
like a system, and to their giving up the attack directly they supposed
themselves discovered.

When using the towing torpedo, two boats only could be used, and they
should make the attack, either coming down from ahead, one on each side
of the vessel, or coming up from the stern, one on each side of the
vessel, or by the boats crossing the bow and stern of the vessel in
different directions.

In the case of the fish torpedo the attack must be conducted in a
different manner, the object in this case being to get within a certain
distance only of the vessel undetected, and from thence send the
missile on its deadly course. The distance should not be more than 500
yards; the closer up to 200 yards the better. In connection with such
an attack, the torpedo boats might be supported by guard boats, whose
particular duty it would be to engage the enemy's guard boats and so
leave the torpedo boats free to do their particular work.

It has been suggested to use the electric light from the bows
of torpedo boats, but this would do away with one of the chief
characteristics of such boats, viz. their invisible and unknown
approach, on which the whole success of the attack in a great measure
depends.

_Fosberry's Patent Torpedo Boat Protective._--To enable torpedo
vessels and boats to remain afloat after being struck by shot from
mitrailleuses, rifles, and other arms usually employed against such
craft, and at the same time to retain their structural lightness,
Colonel G. V. Fosberry, of the English army, has designed the following
method, which is based upon the discovery that when india-rubber or
the like is placed and secured on a metal plate, and is penetrated
or punctured by a rifle bullet or similar projectile, which also
passes through the metal plate, the hole or orifice so formed in the
india-rubber will, after the projectile has passed through it and the
metal plate, immediately be closed by the elasticity of the surrounding
portions, so that no water can follow the projectile through the
said hole or orifice. India-rubber or other elastic material, or
a combination of such materials, in the form of sheets, belts, or
coats, is placed upon or around those portions of the hull of the boat
which are to be protected. Vulcanised or mineralised india-rubber
is the material usually employed by Colonel Fosberry. Between the
metal plates and the india-rubber covering an intermediate substance,
generally kamptulicon, is interposed, which is cemented or riveted to
the said metal plates, and to which the india-rubber is attached. This
intermediate substance, which is the feature of the invention, must be
of such a nature that it may be caused to adhere closely and tightly
to all parts of the metal, and also to the india-rubber covering, while
the same are unperforated, but when the said india-rubber covering and
the metal plate under the same are perforated by a bullet, the portion
of the said intermediate substance adjacent to the perforation must
be detached from the elastic covering and metal plate, and leave the
former free to act like a valve, and close up over the hole so that no
water may enter; and this intermediate substance, as applied by the
inventor in the immediate vicinity of the perforation, will by the
effect of the shot be so broken up and detached from the india-rubber
covering as to allow the same to recover its original position
independently of the new shape or position of the injured and deformed
metal plate.

Should the india-rubber be placed upon the metal plates and be so
attached to the said plates as to adhere and conform to them in
or after their deformation, a hole made in the india-rubber would
remain open; on the other hand, should the india-rubber without any
intermediate substance be attached to the metal plate in such a manner
that it will recover its position after perforation, water would
penetrate between the metal and the india-rubber, and by the pressure
of this water the india-rubber would be liable to be detached from
a large area of the metal plate, and so become ineffective or even
dangerous to the boat. Moreover, if the india-rubber is fixed directly
upon the metal plates, in the case of a shot passing completely through
the boat, that is to say, passing into the boat at one side and out at
the other side, a large portion of the india-rubber adjacent to the
hole made by the shot in leaving the boat will be torn or destroyed,
but this will not be the case in boats constructed according to Colonel
Fosberry's patent.

The French government have recently applied this invention to one of
their torpedo boats with very successful results, thereby proving that
it is not merely a theoretical idea.

_Submarine Boats._--Submarine boats, if they could be constructed to
fulfil the conditions hereinafter enumerated which are essential to a
perfect boat of that nature, would for many reasons be a very important
point solved in connection with torpedo operations, and therefore it is
most extraordinary that a practicable submarine boat has not yet been
designed and built.

_Bushnell's Submarine Boat._--The first submarine vessel built for
torpedo purposes was designed and constructed by David Bushnell in
1775. This vessel, operated by a Sergeant Esra Lee, was employed in an
attempt in 1776 or thereabouts on the _Eagle_, an English man-of-war,
which proved unsuccessful, owing to the sergeant not being thoroughly
versed in the management of his curious craft. She was soon afterwards
sunk in the Hudson river, but was subsequently recovered by the
inventor, though never used again. This vessel was capable of holding
one person, and air sufficient to support him thirty minutes without
receiving fresh air, and is fully described in 'Barnes's Submarine
Warfare.'

_Qualifications essential to a Submarine Boat._--A submarine boat
should possess the following qualifications:--

1.--It should be of sufficient displacement to carry
the machinery necessary for propulsion, and the men and
materials for performing the various operations.

2.--It should be of such a form that it may be easily
propelled and steered.

3.--It should have sufficient interior space for the
crew to work in.

4.--It should be capable of carrying sufficient pure
air to support its crew for a specified time, or of
having the means of purifying the air within the boat,
and exhausting the foul air.

5.--It should be able to rise and sink at will to the
required depth, either when stationary or in motion.

6.--It should be so fitted that the crew possess the
means of leaving the boat without requiring external
assistance.

7.--It should carry a light sufficient to steer by, and
to carry on the various operations.

8.--It should possess sufficient strength to prevent
any chance of its collapsing at the greatest depth to
which it may be required to manipulate it.

The results of former experiments with such boats prove that manual
power, which was the original mode of propulsion, is not the motive
power best adapted to such a boat; compressed air, gas as used in the
Lay torpedo boat, and steam, are all of them far preferable to the
original method, but which of these modern ones is the most practicable
has yet to be decided.

The most difficult point to be overcome in connection with a submarine
boat is that of steering it correctly when beneath the surface of the
water.

_Confederate Submarine Boat._--The Confederate submarine torpedo
boat that sunk the Federal vessel of war _Housatonic_ on the 17th
of February, 1864, was built of boiler iron, 35' long, 3' beam
(extreme), 5' high in the centre. She carried a crew of nine men. She
was propelled by means of a screw propeller worked by eight of the
crew, her greatest speed being four knots an hour in smooth water.
She carried a sufficient quantity of air to enable the crew to remain
submerged for the space of two to three hours. Two fins were fitted on
the outside for rising and falling at will, when in motion. There were
two manholes provided, fitted with bull's-eyes. This boat was intended
to pass under a vessel's bottom, towing a torpedo after her, which was
arranged to explode on contact. She was the means of drowning fourteen
men before she made her last attempt, when nine others were added to
the above list. In her successful attack on the _Housatonic_, she was
armed with the bow spar torpedo, and was sunk, owing to her running
into the hole formed by the explosion of her torpedo. About three
years after the American civil war was over, this submarine boat was
recovered. Divers went down, and found her lying alongside the hull of
the _Housatonic_, with the remains of the nine men in her.

_French Submarine Boat "Plongeur."_--The boat termed the _Plongeur_
was designed by Admiral Bougois and M. Brune, and was exhibited at
the Paris Exhibition of 1867. She was 26' long, 9' deep, and fitted
with centre and bilge keels. She carried two small tanks containing
compressed air, and four large tanks were placed at the bottom of the
boat for the purpose of sinking her, these latter tanks communicating
with the water outside and the air tanks. She also was fitted with a
compass for steering by, a water gauge to show the depth of submersion,
and an air gauge to show the pressure of air in the boat. Rectangular
valves were placed at the bottom of the boat for entrance or exit
therefrom, for the use of divers, and to affix torpedoes to a ship's
bottom. On the top a circular opening for entrance and exit was
arranged, also an iron cupola fitted with bull's-eyes. She was also
fitted with an apparatus for spraying water through the air in the
interior of the boat on its becoming foul, and escape valves for
releasing any foul air were placed at the top of the boat. The water
tanks were filled by means of pumps, and emptied by means of the
compressed air. She was propelled by a three-bladed screw worked by
four men. Her rate of progression was about four knots per hour. The
anchors consisted of two 15 inch shot, fitted with wire rope cables,
working through watertight stuffing boxes.

This vessel has been subjected to some experiments, but with what
results is not generally known.

One of the most important uses to which a submarine boat would be put
in connection with torpedo operations would be "to discover the exact
position and number of an enemy's submarine mines, and if necessary
destroy them," the former being an operation in the present day quite
impossible to perform, and the latter one rarely to be depended on.

FOOTNOTES:

[Footnote M: Extract from 'European Ships of War,' &c., by J. W. King,
U.S.N., page 312.]

[Footnote N: Extract from _Engineering_, under date April 13, 1877.]

[Footnote O: Extract from letter of Captain Ericsson that appeared in
_Engineer_, under date Nov. 8, 1878.]

[Footnote P: Extract from the Engineering of the 10th of January, 1879.]

CHAPTER VII.

TORPEDO OPERATIONS.

A REVIEW, however brief, of the numerous torpedo operations that have
of late years been carried out in actual war, must prove not only of
great interest, but of material aid to those who may be desirous of
studying this branch of naval warfare, for the experience so gained
ought alone to be the basis on which a system of submarine offence and
defence should be constructed.

No new torpedo invention should be adopted, however theoretically
perfect it may be, until it has been subjected to a very severe
practical test, under conditions as nearly analogous to those that
would occur on active service as it would be possible to obtain. The
vast importance of a carefully planned and executed system of submarine
_defence_ is an established fact, and it only remains to discover what
are the best weapons for, and most practicable mode of manipulating a
system of submarine offence, to establish torpedo warfare in all its
branches as a necessary function of naval warfare.

It would be a mere waste of time to dwell on the Anglo-French and
American wars of the beginning of this century (1797-1812); though
during that period various attempts were made by Fulton and others
to destroy hostile vessels by means of submarine infernal machines,
inasmuch as they all partook more or less of the nature of experiments,
and were all failures, but come at once to the Crimean war (1854-1856),
when what may be termed a systematic employment of torpedoes for
harbour defence was first employed.

CRIMEAN WAR (1854-56).

_Defence of Sebastopol Harbour, &c._--The Russians employed a large
quantity of submarine mines, both electrical and mechanical,
principally the latter, in their defence of the harbours of Sebastopol,
Sveaborg, and Cronstadt.

According to General Delafield, U.S.A., the arrangement of the
mechanical mines was entirely new, the conception and idea of an
eminent Russian chemist, Professor Jacobi.

_Electrical Mines._--No mention is made by the General of the
employment of electrical mines, but the fact of a hulk being captured
by the Allies at Yenikale, with a number of torpedoes on board, and
all the arrangements necessary to explode them by electricity, such as
Voltaic piles, electric fuzes, several miles of conducting wire, &c.,
is sufficient proof of this type of submarine mine being extensively
used by the Russians in their harbour defences.

Many of their mechanical mines were picked up by the Allies, several of
which were found to have their safety caps on. Owing to this neglect,
and the smallness of the charge of the torpedoes (only some 25 lbs. of
gunpowder), it is not to be wondered at that no serious injury was done
to any ships of the allied squadron.

Deterred most probably by the failures of Bushnell, Fulton, and others
in previous years with the submarine and other torpedo boat attacks,
nothing of this description was attempted by either side.

_Russian Mechanical Mines._--The Russian mechanical mines consisted
of barrels of powder fitted with fuzes, so arranged that a blow would
smash a glass tube containing sulphuric acid, causing the acid to mix
with some chlorate of potash, resulting in combustion and the explosion
of the mine.

AUSTRO-ITALIAN WAR (1859).

_Defence of Venice by Von Ebner._--During this brief struggle,
defensive torpedo operations were carried out under the direction of
Colonel Von Ebner, of the Imperial Austrian Engineers.

The harbour of Venice was protected by a most elaborate system of
submarine mines, devised by the above-named officer. Though the
importance of his system was proved by the fact of no attempt being
made on Venice, yet no opportunity was afforded of _practically_
testing its efficiency.

AMERICAN CIVIL WAR (1861-65).

_Cause of the Present Importance of the Torpedo._--The prominent
position the torpedo now holds as a most important and legitimate
function of naval warfare is owing without doubt to the successful and
extensive employment of them on the part of the Confederates during
this long and bloody struggle.

_Reasons which induced the Confederates to employ Torpedoes._--The
numerous harbours and navigable rivers in the possession of the
Southerners, the few ships of war at their disposal, the overwhelming
fleet of the Northerners, and the introduction for the first time of
ironclads in naval warfare, are the principal causes which forced the
Confederates to resort to torpedoes as a means of offence and defence.

Though a few rude and extempore submarine mechanical mines were met
with by the Federals during the earliest part of the war, it was not
until many months after the commencement of hostilities that the
Confederates, finding themselves quite unable to cope with their rivals
on the sea, set to work in earnest to organise a system of submarine
warfare on a grand scale.

_Torpedo Corps formed, &c.--Loss of "Cairo."_--By October, 1862, a
secret service torpedo corps, with headquarters at Richmond, was in
full swing, and the principal harbours and rivers of the Confederates
were systematically protected by means of electrical and mechanical
mines, also a scheme of offence by drifting and spar torpedoes was in
preparation, and in December of the same year they experienced the
first-fruits of their labour by the total destruction of the Federal
war steamer _Cairo_.

The following brief review of the numerous torpedo operations carried
out by both sides, and the effect their use had on the war, will be
sufficient to enable the general reader to gain some idea of the vast
importance of this submarine weapon in future warfare.

Fuller and more detailed accounts will be found in Commander S.
Barnes's, U.S.N., Colonel Von Scheliha's, and Captain H. Steward's
torpedo works.

_Every Species of Torpedo used--Frame Torpedoes at Charleston,
&c.--Federal Ship Disasters--Small Effect of Electrical Mines--Loss of
the "Commodore Jones," &c._--Every species of submarine mine seems to
have been used by the Southerners for their harbour and river defence,
the most effectual of which were the barrel, frame, and Singer's
torpedoes. These were all mechanical, fired by means of sensitive
concussion fuzes. At Charleston and elsewhere the frame torpedo, which
also acted as an obstruction, was largely used, and where this species
of mine was known to be laid, the Northerners never attempted to force
a passage. Out of some thirty or forty Federal ships sunk or injured by
torpedoes, by far the larger proportion of such disasters was effected
by means of the barrel and Singer's mines. Though electrical mines were
very extensively used on the St. James River and at Charleston, &c.,
yet only one Federal steamer, the _Commodore Jones_, was sunk, and only
one other, the _Commodore Barney_, was injured.

_Case of the "New Ironsides."_--The Federal ship _New Ironsides_, at
the attack on Charleston in 1863, was anchored for one hour and a half
exactly over a 5000 lbs. electrical mine, which despite all the efforts
of the Confederates could not be exploded. The reason of this was owing
to the deterioration of the primer, due to too constant testing.

_Welden Railway._--A notable instance of the effect of torpedoes on the
war was the saving of the Welden line of communication in December,
1864. The Welden Railway was the principal artery of communication
to Richmond for the Confederates. To intercept this, by destroying
the railway bridges, a fleet of nine Federal gunboats was sent up the
Roanoke river; when nearly arrived at their destination, and though
every precaution in the shape of bow projecting spars, creeping, &c.,
was taken, seven of the vessels were either sunk or severely injured by
submarine mines. Thus the expedition ended in a most disastrous failure.

_General Butler's Attack on Richmond._--Again, in April, 1864, General
Butler's attack on Richmond utterly failed, owing to the Federal fleet
being unable to co-operate with him, the destruction of the _Commodore
Jones_ completely checking any further advance of Admiral Lee's ships,
thus allowing the Confederates to employ the garrisons of their river
batteries in their land line of entrenchments.

_More than One Line of Torpedoes required._--The capture of the Spanish
fort at Mobile in April, 1865, by a Federal fleet under Admiral Lee,
proves the necessity of employing more than one line of torpedoes,
where the safety of a position depends almost entirely on those means
of defence, as this one did. Here, though several Federal vessels were
either sunk or severely damaged, yet the fort was captured.

_Boat Torpedo Attacks._--In regard to boat torpedo attacks, the
Confederates were only successful in two out of many attempts made by
them to sink Federal vessels.

_The "Housatonic" and "Minnesota."_--These successes were the complete
destruction of the Housatonic by a submarine boat, fitted with a spar
torpedo, and serious injury caused to the _Minnesota_ by the explosion
of a contact spar torpedo, carried by an ordinary gig, commonly termed
"David's." In the former instance the attacking boat was sunk,[Q] in
the latter instance she was uninjured.

_Destruction of the "Albemarle."_--On the part of the Federals,
Lieutenant Cushing with a steam launch fitted with a Wood and Lay
torpedo, succeeded in sinking the Confederate ram _Albemarle_. The
boat in this instance was swamped by the column of water thrown up on
the explosion of the torpedo, she having been driven full speed at the
Albemarle.

_Ship Spar Torpedoes._--On both sides, spar torpedoes fitted to the
bows of ships, and also on rafts slung over the bows, were somewhat
extensively used, but on no occasion were they the means of injuring or
sinking any vessels.

To increase the difficulties of the Northerners in searching for
submarine mines, the Southerners laid down a great number of dummy
torpedoes, also erected false torpedo stations, and laid false wires.

It must always be borne in mind, in connection with the torpedo
operations above detailed, that the apparatus were very crude, and the
operators at the commencement inexperienced.

PARAGUAYAN WAR (1864-68).

_Torpedoes employed by the Paraguayans._--During their protracted
struggle with the Brazilians, the Paraguayans employed submarine mines
for the protection of their river forts, &c.

_Loss of the "Rio Janeiro"--Brazilian Fleet entrapped._--On the 2nd
of September, 1866, the Brazilian ironclad _Rio Janeiro_, after
being well-battered by the guns of the Curupaity fort, was sunk by a
torpedo. Later on, near the same place, a whole fleet of Brazilian war
ships were entrapped by the Paraguayans, between two rows of submarine
mines, but owing to faulty arrangements they escaped unharmed.

AUSTRIAN WAR (1866).

_Venice, Pola, &c., protected by Torpedoes._--During this war,
torpedoes for the defence of Venice, Pola, &c., were extensively used
by the Austrians, under the direction of Baron von Ebner, but as in '59
no opportunity was afforded of proving their practical worth, though
morally they were of great value, the Austrian harbours so defended
being considered impregnable by the enemy, and therefore no attempt was
made to force them.

FRANCO-GERMAN WAR (1870-71).

Little or nothing in the matter of torpedo operations was attempted by
the Germans, and on the part of the French nothing whatever.

_Germans employed Submarine Mines._--Electrical and mechanical mines
were placed in several of the German harbours, the former containing
about 200 lbs. of dualine, the latter some 80 lbs. of gunpowder. The
only attempt to destroy French ships by means of offensive torpedoes
was made by the German vessel the _Grille_, off Rügen, which resulted
in failure.

In laying down and in picking up after the war was over their
mechanical mines, several exploded, killing some ten to fifteen men.

_Boats necessary._--Towards the end of the war, the Germans were
constructing special torpedo boats, believing that such were necessary
for the complete defence of harbours. This war added another proof of
the moral worth of submarine mines; the French fleet not daring to
approach German waters _supposed_ to be defended by such means.

RUSSO-TURKISH WAR (1877-78).

_Superiority of Turkey to Russia in the matter of Ships._--On the
Danube, in the Black Sea, and Mediterranean, where the principal naval
portion of the war was carried out, Turkey was possessed of a fleet
of ships infinitely superior to Russia, both in point of numbers and
strength, and therefore, to enable her to hold her own against this
vast superiority of the Turks, the Russians resorted to an extensive
employment of torpedoes, for both offensive and defensive purposes.

_Russian Torpedoes._--For many years previous to the outbreak of
hostilities in April, 1877, the Russians had been studying the subject
of torpedo warfare in all its branches, a certain number of their
naval and military officers and men having every year passed through
a regular course of torpedo study, at a school specially formed for
such a purpose; they had also laid in large stores of submarine mines,
spar torpedoes, and were in possession of the Whitehead and towing
torpedoes, and also several electric lights, and a few months after war
was declared they obtained a fast Thornycroft torpedo boat.

_Turkish Torpedoes._--On the other hand, the Turks were only in
possession of a number of those huge, unwieldy 500 lbs. buoyant mines,
and one electric light; circuit closers, contact mines, boats (steam or
otherwise) fitted for use with torpedo, or offensive torpedoes, being
conspicuous by their absence.

Thus it will be seen that in the matter of submarine offence and
defence, the Russians were as superior to the Turks as the latter were
to the former in the matter of ships.

_Turkish Defensive Torpedo Operations._--The defensive torpedo
operations carried out by the Ottoman naval officers and men were as
follows:--

The harbour of Batoum in the Black Sea was protected by a few 500 lbs.
buoyant mines, arranged to be fired by observation.

The mouth of the Bosphorus and the Dardanelles were similarly defended.
For this work great praise is due to those who executed the work, for
the very strong current and great depth met with in those waters would
render such a service a work of great difficulty, even when properly
constructed mooring boats, and men trained to such, were employed, both
of which in this particular instance were absent.

Soulina, one of the mouths of the Danube, and Suda Bay (Candia) were
also protected by similar means.

_Russian Defensive Torpedo Operations._--The Russian defensive torpedo
operations were very extensive, their principal harbours in the
Baltic, as well as those in the Black Sea, were carefully defended by
electro-contact mines of the latest type; so also they protected their
numerous bridges across the Danube, double and sometimes treble rows
of such mines being moored on either side, and in addition they also
placed several mines in the Danube, on the chance of destroying the
Turkish Danube flotilla.

_Destruction of Turkish Gunboat "Suna" by a Russian Submarine
Mine._--The only instance that occurred during this war of a vessel
being sunk by a stationary submarine mine was that of the Turkish
gunboat _Suna_, at Soulina, in October, 1877, on the occasion of the
unsuccessful attack on that place made by the combined Russian and
Roumanian flotilla.

About 6 A.M. on the morning of the attack, a "loftcha" containing two
of the enemy's electro-contact mines, fitted for laying down, was
captured by the Turks, from which it was evident that the Russians had
been employed during the night in torpedoing the reach immediately
above the Turkish defences. However, not heeding this very practical
warning, the Pacha in command of the Soulina squadron ordered the
_Kartal_ (a paddle-wheel tug vessel) and the _Suna_ (an old wooden
gunboat) to reconnoitre up the river; they accordingly started, the
_Kartal_ leading the way. At 8.5 A.M., about fifteen minutes after the
two vessels had left their moorings, an explosion was heard, and almost
at the same instant the unfortunate gunboat _Suna_ was observed to go
down head foremost, her masts only remaining above water. The _Kartal_,
which at the time of the catastrophe was some distance in advance, at
once turned back to the assistance of her consort, and managed to save
a number of the gunboat's crew, this work having to be performed under
a galling fire from the allied flotilla. Owing to this day being the
"Feast of Bairam," the unfortunate gunboat was dressed with masthead
flags, thus four Turkish ensigns fell into the hands of the enemy, the
Pacha refusing permission for any attempt to be made to save them. The
reason that the _Kartal_ escaped the fate of her consort was due to her
only drawing some 5 feet of water, while the _Suna_ drew at least 8
feet.

The gunboat struck the mine that sunk her on her port bow, the effect
of the explosion being to completely smash in that side of her bow,
dismount her foremost guns, and carry away her foremast just above the
deck (the mast remained standing, though inclined forward); the second
lieutenant of the _Suna_, who was at the time of the explosion standing
on her fore bridge, was thrown off and killed, and some twelve of
the crew were killed and wounded. To complete the destruction of the
_Suna_, another torpedo was exploded under her port quarter by the
Russians. The torpedo that was used on this occasion is detailed at
page 68.

_Offensive Torpedo Operations._--The numerous boat torpedo attacks made
by the Russians against the Turkish fleet will now be considered. The
following accounts have been carefully compiled from two sources, viz.
an article written by Captain Chardonneau, which appeared in the 'Revue
Maritime et Coloniale,' 1878, and which has been recently translated
for the Journal of the Royal United Service Institution by Lieutenant
J. Meryon, R.N., and notes taken by the author during his service with
the Imperial Ottoman Navy (1877-78).

1ST AFFAIR.

_The Batoum Attack._--The first torpedo boat attack occurred on the
night of the 12th-13th of May at Batoum.[R]

On the night of the attack there were lying in the harbour several
vessels of the Ottoman fleet, including ironclads, transports,
despatch-boats, &c. These vessels were totally unprotected by guard
boats, booms, electric lights, &c., and only the usual number of
sentries were posted, the Turks at that time not quite believing in
such boat attacks, thus offering peculiar advantages for a torpedo
attack.

Four torpedo boats formed the attacking force, viz. the _Tchesme_,
_Sinope_, _Navarino_, and the _Soukoum Kalé_.

These boats were carried by a ship of the Maritime Company of Odessa,
named _Grand Duke Constantine_. She was an iron screw steamer,
able to steam about 10 knots per hour, and fitted to hoist up the
above-mentioned torpedo boats. She was armed with four 4-pounders, and
torpedoes.

Early in the evening of the 12th the _Constantine_ left Poti, and
proceeded off the harbour of Batoum, her captain (Lieutenant de
Vaisseau Makaroff) deeming it advisable to lay to seven miles from the
harbour, the supposition that the Turks had placed submarine mines off
the entrance being the cause of his so doing.

About 11 P.M. the four torpedo boats started to the attack, Makaroff
being in command of one of them. They were all painted sea green,
and possessed a high speed. The night being dark, and having been
despatched some distance off, they reached the entrance in somewhat
straggling order. The _Tchesme_, commanded by Lieutenant Zatzarennyi,
and armed with a towing torpedo, was the first to enter the harbour,
and, without waiting for her consorts, dashed at the Ottoman fleet, and
succeeded in getting close to a large Turkish paddle-wheel transport,
and her commander dipping his torpedo, struck the ship under her
quarter; but that little something which so often causes a failure in
this mode of warfare occurred, and no explosion followed the pressing
down of the firing key, much to the chagrin and disgust of Zatzarennyi.
As might be supposed, by this time an alarm had been raised, and guns,
rifles, &c., were fired in and from every direction, causing the
torpedo boats to beat a precipitate and hasty retreat. Fortunately the
Turks were not possessed of any steamboats, nor were any of their ships
ready to dash out, or the defeat would have been a far more disastrous
one than was the case. Neither of the boats were damaged, nor any of
the crews injured.

The failure of this first attempt was due in a great measure to the
mode of attack, no system or unanimity of action on the part of the
four commanders being observable; and also to the somewhat half-hearted
support given to the _Tchesme_, for had her three consorts only dashed
at the Turkish ships as boldly, one at least of the Ottoman fleet would
have been sunk, the only defence resorted to being their guns and small
arms.

The moral effect of torpedoes was displayed here, causing the
_Constantine_ to lay too far off the entrance to the harbour, thus
decreasing the chance of her boats making a successful attack.

The Russian version finishes up by saying, "although this first
endeavour was unsuccessful, the authors of it were received at
Sebastopol with enthusiasm."

2ND AFFAIR.

_The Matchin Attack._--The second attempt was made on the 25th-26th of
May on two Turkish monitors, the _Fettu Islam_ and the _Duba Saife_,
and a small river steamer, the _Kilidj Ali_, lying at anchor off
Matchin.[S]

Four Russian torpedo boats were sent to the attack, viz. the
_Czarowitch_, Lieutenant Doubasoff; the _Xénie_, Lieutenant Chestakoff;
the _Djiquite_, Midshipman Persine; and the _Czarevna_, Midshipman
Bali. The total number of officers and men carried by these boats on
this occasion was forty-six.

The night of the attack was rainy, but not completely dark, since the
moon was above the horizon during nearly the whole of the expedition.

The force left Brailoff at one o'clock on the morning of the 26th,
and advanced in two columns up the river, finding great difficulty in
stemming the strong current.

A boat from the _Duba Saife_, rowing guard some 500 yards in advance of
the squadron, observed the approach of the Russian boats, but allowed
them to pass on their voyage of destruction without attempting to
stop them, or alarm the vessels. On reaching within 150 yards of the
_Duba Saife_, Dubasoff in the _Czarowitch_ was challenged, and failing
to give the correct answer was immediately fired at; but, nothing
daunted by the hail of shot and bullets, he dashed on, and succeeded
in exploding one of his spar torpedoes on the port side of the _Duba
Saife_, just under her quarter, a column of water and _débris_ being
thrown up to a height of 120 feet, which partly filled his boat, but
notwithstanding managed to get safely away. The monitor not sinking as
soon as expected, Chestakoff in the _Xénie_ dashed in, and completed
the work of destruction, the unfortunate ship sinking in a very few
minutes after this last explosion. The _Djiquite_ was struck in the
stern, and had to be run ashore for repairs, but eventually all four
boats reached Brailoff in safety. The Russians allowed to neither
killed nor wounded, which, when the time they were exposed to the fire
of the three Turkish ships (about twenty minutes), the number of men
(forty-six) engaged, and their very close quarters, seems miraculous.

The _Duba Saife_, thus lost to the Turks, carried two 12 cm. Krupp
guns, and a crew of some sixty officers and men, few of whom were
saved. Lieutenants Dubasoff and Chestakoff were decorated with the
4th Class of the Cross of Saint George, and three seamen received the
insignia of the Order of Military Merit.

This attack was conducted in a most gallant manner, and far more
systematically than the Batoum affair. If instead of holding one of the
boats in reserve, which was part of Dubasoff's plan, and the remaining
three attacking one vessel, the force had divided itself into two
parties, and had made a simultaneous attack on both the monitors, the
probability is that the _Fettu Islam_ would have shared the fate of her
consort.

The officer of the Turkish guard boat was tried by court-martial,
but what his ultimate fate was is not generally known. He certainly
deserved nothing less than death.

3RD AFFAIR.

_The Soulina Attack._--The third attempt took place on the 9th-10th
of June, 1877, on a Turkish squadron lying at anchor off Soulina.[T]
This squadron consisted of the three ironclads _Feteh Bulend_,
_Moocardemikhair_, and _Idglalieh_, and a tug, _Kartal_.

The Russian attacking force consisted of six torpedo boats, viz. the
No. 1, Lieutenant Poutschin; the No. 2, Lieutenant Rojdestvenski; the
_Tchesme_, Lieutenant Zatzarennyi; the _Sinope_, the _Navarino_, and
the _Soukoum Kalé_. The No. 2 was a specially constructed torpedo
boat, 68 feet long, and very fast. All were armed with spar torpedoes,
with the exception of the _Tchesme_, which carried a towing torpedo.
The boats were convoyed from Odessa by the _Constantine_, some being
carried, and some being towed; another steamer, the _Vladimir_,
supported her. The Turkish squadron were anchored in quarter line,
about one mile from the harbour; the _Kartal_, under weigh, being used
as an advance guard, and a few boats rowing guard close to the ships
being _the only means of protection_ adopted by the Turks. Passive
obstructions, such as booms, nets, crinolines, &c., were not thought
of, much less used.

On arriving about five miles from Soulina, the boats were formed into
two groups, the first consisting of the No. 1, the No. 2, and the
_Tchesme_, and despatched on their way. The working of their engines
was scarcely heard, and all lights were carefully hidden by tarpaulins.

The first casualty that happened was the disabling of the _Tchesme_,
by the electric wire of her towing torpedo fouling the screw, this
obliging her to return to the _Constantine_. Aided by good fortune,
and by the darkness of the night, the No. 1 and the No. 2 succeeded
in getting close to (30 yards) one of the Turkish vessels, the
_Idglalieh_, before being discovered, when they were at once hailed,
and, not answering, a tremendous fire of big guns and rifles was
directed on them from the _Idglalieh_, which was promptly followed by
that of the whole squadron, though from the other ships nothing of the
boats could be seen.

According to the Russians, the No. 2 succeeded in exploding her
torpedo close to, if not in contact with, a Turkish vessel, but from
eyewitnesses on board the squadron only one explosion was heard, viz.
that of Lieutenant Poutschin's torpedo. Any way, no damage whatever
was experienced by the Ottoman squadron. The No. 1 came down on the
_Idglalieh's_ starboard bow, fouled her cable, and swung alongside,
exploding one of her torpedoes in so doing, but with no other result
than a wetting to those of the ironclad's crew, who were on the
forecastle. Alongside Poutschin remained for some minutes, but at last
managed to get clear, and then was either sunk by the _Idglalieh's_
fire, or, as he avers, on finding his screw foul, he sunk his boat,
rather than let her fall into the hands of the Turks. Poutschin and
four of his crew were picked up, after being some hours in the water,
by the squadron's boats.

The No. 2 seems to have suffered severely, her funnel being bent, the
axle of the steering wheel damaged, sixteen rivets were started, and
the iron keel plate had dropped some 18 inches, and finally the lower
part of her rudder broken, and one of the blades of her screw bent aft;
part of this damage was no doubt the effect of the explosion of her
torpedo, which was probably not in position, but unless she ran over
some loose stones of the Soulina breakwater, the damage to her keel and
rudder cannot be accounted for.

The second group of boats had followed up the first, but on hearing the
noise of the explosions and roar of the guns and rifles they returned
to the _Constantine_.

That ship, on observing the firing, endeavoured to close the land, but
she grounded, and remained until daylight in a difficult position, but
at last got afloat, and returned to Odessa with five out of her six
torpedo boats.

Lieutenant Rojdestvenski, the Commander of the No. 2, received the 4th
Class of the Cross of Saint George, and three seamen the insignia of
the Order of Military Merit.

On the part of the No. 1 and No. 2, this was a most gallant affair,
though unsuccessful, but as regards the remainder of the boats the less
said the better.

Had the Turkish squadron slipped the instant the alarm was given, and
steamed full speed in the direction of Odessa, the _Constantine_ and
her convoy might have been cut off. Both the _Moorcademikhair_ and
_Feteh Bulend_ were 13 knot ships, and therefore considerably faster
than the enemy. But, as usual, the Turks were far too dilatory to take
advantage of the occasion.

4TH AFFAIR.

_The Rustchuk Attack._--The fourth torpedo attack was made on the
afternoon of the 20th of June, 1877, on a Turkish monitor off Rustchuk.

The only Russian torpedo boat sent to the attack on this occasion was
a Thornycroft named the _Choutka_, commanded by Lieutenant Skrydloff,
and accompanied by a celebrated Russian artist, Verechtckaguine by
name. The instant the torpedo boat was observed, so well directed and
steady a fire was kept up by the monitor that both the lieutenant and
the artist were badly wounded, and the electric wires of the torpedo
severed, thus obliging the _Choutka_ to beat a retreat. According to
the Russian account, the monitor was struck by the boat's torpedo
spar, but the above seems the more likely version. This was certainly
a most audacious attack, and had the Turks only succeeded in hitting
the _Choutka_ with her big gun, it would have ended fatally for the
Russians; as it was, the boat was struck by several bullets, but none
of the crew were wounded.

5TH AFFAIR.

_The Aluta Attack._--The fifth attack was made on the 30th of June,
1877, on a Turkish monitor off the mouth of the Aluta, in the river
Danube. This attempt, like the last, took place in broad daylight. Four
Russian boats were sent forward, but in spite of the captain of the
Turkish vessel doing all he could to run the boats down, none of them
succeeded in getting sufficiently near the vessel to enable a torpedo
to be placed in contact. The captain of the monitor took the precaution
to rig his lower booms out, and so managed to keep the enemy's boats
at a respectful distance, they imagining that mines were fixed to the
ends of the booms. After two hours of this dodging about, the Russians,
finding the case hopeless, abandoned the attack.

The Russian account states--1st, that the captain of the monitor was an
Englishman; 2nd, that the vessel was protected by nets and torpedoes
lashed to the extremities of her booms--both of which statements are
radically wrong.

The torpedo boats forming the attack were the _Choutka_, Midshipman
Niloff, and the _Mina_, Sub-Lieutenant Arens, both armed with the spar
torpedo.

Unless indeed the Russians acted up to the old proverb which says
"Discretion is the best part of valour," it is difficult to understand
how four small easily handled boats could have been for one hour
endeavouring to strike a ship (which ship was at the same time being
manoeuvred with a view of running them down) without either effecting
their object or being sunk or damaged in the attempt.

The Russians, though unsuccessful, behaved gallantly. Midshipman Niloff
was severely wounded, but no mention is made as to the number of the
crew that were killed and wounded, or of the damage received by the
boats. Niloff received the 4th Class of the Cross of St. George, and
Arens the Order of Military Merit.

The Turkish captain, Ali Bey, behaved most pluckily and skilfully. The
only wonder is that both the boats were not sunk by the monitor's fire.

6TH AFFAIR.

_The Soukoum Kaleh Attack._--The sixth attempt was made on the
23rd-24th of August, 1877, on a Turkish ironclad, the _Assari Shefket_,
at the time lying at anchor off Soukoum Kaleh.[U] Four torpedo boats
composed the attacking force, viz. the _Sinope_, Lieutenant Pisarefski;
the _Torpedoist_, Midshipman Nelson Hirst; the _Navarino_, Lieutenant
Vichnevetski; and the _Tchesme_, Lieutenant Zatzarennyi, the latter
officer being in command. These boats had been brought to the entrance
of the harbour by the _Constantine_, and were despatched on their
mission of destruction about half past ten.

An eclipse of the moon occurred on this night, and, taking advantage of
this fact, the four Russian torpedo boats dashed into the harbour at
full speed and made for the Turkish vessel.

Fortunately for the safety of his ship and lives of his crew, the
captain of the Turkish ironclad had several boats rowing guard round
his ship, and otherwise everything on board in readiness for immediate
action. On the attacking flotilla nearing the guard boats, blue lights
were burnt, rifles fired, &c., and the alarm given to those on the
look-out in the _Assari Shefket_. The moment the enemy were within
range, such a well-directed and heavy fire was poured on them that
the attack was completely foiled. One of the Russian torpedoes was
exploded, but failed to do more than throw a quantity of water up.
The next morning a pole with torpedo fixed on it was found by the
Turks, and on the strength of this and the numerous fragments of wood
similarly found, one if not more of the enemy's boats it was supposed
must have been sunk, or much knocked about.

This was a much better planned and executed attack, but was
unsuccessful owing to the extreme vigilance of the Turks.

This attempt will always be remembered by the Turks, on account of the
general order that appeared in the papers on the part of the Russians,
in which "the brilliant exploit and successful destruction of the
Turkish ironclad _Assari Shefket_" was set forth at great length; she
at the time that this appeared being quietly at anchor off the dockyard
at Stamboul, not having received any damage whatever.

7TH AFFAIR.

_The Second Batoum Attack._--The seventh attempt was made on the night
of the 27th-28th of December, 1877, on several Turkish men-of-war
anchored in the harbour of Batoum (the scene of the first Russian
torpedo attempt and failure). Four boats composed the attacking force,
viz. the _Tchesme_, Lieutenant Zatzarennyi, in command, armed with a
Whitehead fish torpedo, containing 32 kilog. of gun-cotton, fitted
to fire from a tube under the boat's keel; the _Sinope_, Lieutenant
Stchelinski, armed with a similarly charged fish torpedo, fitted to
fire from a raft, which was towed by the boat, and two other boats,
armed with spar and towing torpedoes.

The means employed at Batoum for the safeguard of the Ottoman fleet
there against such an attack was that of guard boats and a barrier
formed of logs of wood, with planks secured to them, so arranged by
means of weights that the planks remained perpendicular to the surface
of the water when in position.

Owing to the extreme darkness of the night, the Russians managed to
evade the guard boats, and when, as they imagined, some 60 to 65
yards from a Turkish ironclad, the _Tchesme_ and _Sinope's_ Whitehead
fish torpedoes were started on their deadly mission; but, owing most
probably to the want of practice of manipulating these somewhat
delicate instruments, also to the darkness, and the slight swell there
was on at the time, both missed their mark, and were landed high and
dry on the beach astern of the ship.

One of these weapons was perfect, the other minus her fore compartment,
this having been knocked off by the torpedo colliding with some hard
object. No explosion was heard or seen by the Turks.

This was the second time that the fish torpedo had been employed on
actual service, and, as in the previous instance, failed.

The guard boats and barrier of the Turks seem to have been of little
avail.

8TH AFFAIR.

_The Final Attack._--The eighth and last attempt was made on the night
of the 25th-26th of January, 1878.

This was originally intended to be an attack on the Turkish fleet at
Batoum, but on entering that harbour the two Russian torpedo boats,
the _Tchesme_, Lieutenant Zatzarennyi, and the _Sinope_, Lieutenant
Stchelinski, were met by a Turkish revenue steamer, against which the
boats discharged their Whitehead torpedoes, resulting in her complete
destruction, at the same time arousing the squadron, and causing the
boats to beat a retreat.

Though the vessel destroyed was not a frigate, yet the expedition
was successful in so far as proving that it is possible to project
Whitehead fish torpedoes from boats at a distance of 70 to 90 yards
from an enemy's ship, on a dark night, and strike her with them.

This concludes the whole of the offensive torpedo operations that were
carried out during the war, of which two out of eight attempts were
successful, which is without doubt a fair percentage.

There seems every probability that the present struggle between Chili
and Peru, in the Pacific, will afford torpedoists further experience of
the various offensive torpedoes, when subjected to the test of active
service.

FOOTNOTES:

[Footnote Q: See page 185.]

[Footnote R: A Turkish port, situated on the east coast of the Black
Sea, capable of holding several large ships when anchored head and
stern, but otherwise only a few.]

[Footnote S: A town situated on the south bank of the Danube, about
eight miles from Brailoff.]

[Footnote T: One of the principal mouths of the Danube.]

[Footnote U: A place taken from the Russians in the early part of the
war, situated on the east coast of the Black Sea.]

CHAPTER VIII.

ON EXPLOSIVES.

EXPLOSION may be defined as the sudden or extremely rapid conversion of
a solid or liquid body of small bulk into gas or vapour, occupying very
many times the volume of the original substance, and which in addition
is highly expanded by the heat generated during the action.

This sudden or very rapid expansion of volume is attended by an
exhibition of force which is more or less violent, according to
the constitution of the original body and the circumstances of the
explosion.

Any substance capable of undergoing such a change on the application of
heat or other disturbing cause is called an "explosive."

_Explosive Force._--Explosive _force_ is _directly_ proportional to
the heat of combustion and the volume of gas, and _inversely_ to the
specific heat of the mixed products.

Explosive _effect_ is _directly_ proportional to the volume of gas
produced and the temperature of the explosion, and _inversely_ as the
time required for the change to take place.

_Explosive Effect and Force compared._--Explosive effect depends upon
the rapidity with which the conversion is effected, while the same
amount of explosive force may act suddenly or gradually.

As before stated, explosions are more or less violent according to the
_circumstances_ under which they take place. These may be considered as
follows:--

1.--The physical state of the explosive substance.

2.--The external conditions under which the explosive body is fired.

3.--The mode of firing.

_The Physical State of the Explosive Substance._--Numerous instances
may be cited to show the influence the physical condition of an
explosive body has upon its explosion.

Thus, gunpowder may, by merely varying the size, shape, and density of
the grain, be made to ignite rapidly but burn comparatively slowly, or
be made to ignite more slowly, but once inflamed to burn very rapidly.

Again, gun-cotton in a loose, uncompressed state, will, if ignited,
only flash off; if it is spun into threads or woven into webs, its rate
of combustion may be so much reduced that it can be used in gunnery
or for a quick fuze; while if powerfully compressed and damp it burns
slowly. Wet gun-cotton requires a primer of dry gun-cotton and a
fulminate fuze to explode; dry, it may be exploded by a fulminate fuze,
&c.

Then nitro-glycerine, when exploded by 15 grains of fulminate of
mercury, and at a temperature above 40° F., is very violently
detonated; below 40° F. it freezes and cannot be similarly exploded.

To obtain the full effect of all explosives, confinement is absolutely
necessary.

The more rapid the explosion the less confinement required, approaching
in the case of some explosives to so small an amount that it need not,
for practical purposes, be considered.

Thus a charge of nitro-glycerine or gun-cotton, when detonated in the
open air, will destroy wrought iron rails, large blocks of stones,
balks of timber, &c.

In the case of the former body, the confinement of the atmosphere is
sufficient.

In the latter, the mechanical cohesion due to compression is sufficient
restraint.

Abel states that if the film of atmosphere surrounding the
nitro-glycerine, not exceeding 1/1000 inch in thickness, be removed,
the explosive effect is much lessened.

A large charge of gunpowder fired in the ordinary way under water
requires a strong case to retain the gases until the action has become
general, or, owing to its slow rate of burning, the case would be
broken before the whole of the charge had been ignited, and part of the
charge drowned.

This is often to be noticed when firing fine-grained powder in heavy
guns.

Igniting the charge at several points diminishes the confinement needed.

_Mode of Firing._--The application of heat, directly or indirectly, is
the principal means of causing an explosion.

The flame from a percussion cap or primer, or a platinum wire heated to
incandescence by an electric current, will _directly_ ignite a charge.
Friction, concussion, &c., will _indirectly_ ignite a charge due to the
conversion of mechanical energy into heat.

It would appear that when one explosive body is used as a means of
firing another, the resultant explosion is due to the blow suddenly
formed by the gas of the firing charge acting percussively upon the
mass to be exploded. If such were the case, then the most powerful
explosive would be the best agent for causing an explosion. But it is
not so.

For example, nitro-glycerine, which is far more powerful than fulminate
of mercury, requires more than 1000 grains to explode gun-cotton, while
only 15 grains of the latter is needful for the same work, &c.

A small quantity of an explosive substance which is sensitive to
friction or percussion is often used to ignite the original charge.

_Detonation._--The instantaneous explosion of the whole mass of a body
is defined as "detonation."

The essential difference between an explosion and a detonation is the
comparative suddenness of the transformation of the solid or liquid
explosive substance into gas and vapour.

Some explosive bodies, such as the fulminates, &c., always detonate,
while the detonation of others depends on the mode of firing.

Nitro-glycerine always explodes violently, but when fired with an
initiatory charge of fulminate of mercury it is much more powerful than
when fired with gunpowder.

Compressed gun-cotton in the air-dry state can be detonated by 2 grains
of fulminate of mercury embedded in the material, but when it contains
3 per cent. of water over and above the 2 per cent. which exists
normally in the air-dry substance, 15 grains of the fulminate will not
always do so.

_Theory of Detonation._--The theory of detonation is not yet thoroughly
understood. That it is not alone due to the heat caused by the impact
of the mechanical energy of the particles of gas, set free from the
initiatory charge on the principal mass, is proved by the fact of its
being possible to detonate wet gun-cotton.

Professor Bloxam terms detonation to be "sympathetic" explosion.

Experiments carried on in England by Professor Abel, and in France by
MM. Champion and Pellet, tend to show that it is due to the vibratory
action of the detonating agent.

Thus a glass may withstand a strong blow, though a particular note or
vibration will smash it.

All explosive compounds and mixtures, including gunpowder, are
susceptible of violent explosion through the agency of a detonation.

_Roux and Sarrau._--Roux and Sarrau divide explosions into two orders:--

1st order.--Detonations.

2nd order.--Simple explosions.

Simple explosions are produced by direct inflammation, or by a small
charge of gunpowder.

Detonations are obtained from nitro-glycerine, gun-cotton, &c., by
exploding with fulminate of mercury.

They state that fulminate of mercury does not detonate gunpowder; but
if the exploding charge is a small amount of nitro-glycerine, itself
detonated by fulminate of mercury, then an explosion of the first order
is obtained.

The relative effects were approximately measured by determining the
quantities necessary to rupture small cast iron shells of supposed
equal strength.

_Results of their Experiments._--The following are some of the
results:--

+---------------+---------------------------+
| | Explosive Effect. |
| +---------------------------+
| | 2nd Order. | 1st Order. |
+---------------+-------------+-------------+
|Gunpowder | 1·00 | 4·34 |
|Gun-cotton | 3·00 | 6·46 |
|Nitro-glycerine| 4·80 | 10·13 |
+---------------+-------------+-------------+

According to the above table, nitro-glycerine is more than ten times,
and gun-cotton more than six times, as powerful as gunpowder fired in
the ordinary way (2nd order).

The want of reciprocity between two detonating agents is shown in
a remarkable degree by the following experiments, carried out by
Professor Abel:--

1.--The detonation of 1/4 ounce of gun-cotton (the
smallest quantity that can be thus applied) induced the
simultaneous detonation of nitro-glycerine, enclosed
in a vessel of sheet tin, and placed at a distance of 1
inch from the gun-cotton.

2.--The detonation of 1/2 ounce of gun-cotton produces
the same effect with an intervening space of 3 inches
between the substances.

3.--The detonation of 2 ounces of nitro-glycerine in
_close contact_ with compressed gun-cotton failed to
accomplish the detonation of the latter, which was
simply dispersed in a fine state of division, in all
the instances but one, in a large number of experiments.

Explosive agents are divided into explosive mixtures and compounds.

In the former the ingredients are mechanically mixed, and can be
separated by mechanical means.

In the latter the ingredients are chemically combined, and can only be
separated by chemical change.

_Torpedo Explosive Agents._--The explosive agents that are practically
the most important, as far as their employment as torpedo charges are
concerned, are as follows:--

_Explosive Mixtures._--A.--Explosive mixtures.

1.--Gunpowder. } Nitrate class
2.--Ammonium picrate, or picric powder. }

_Explosive Compounds._--B.--Explosive compounds.

1.--Nitro-glycerine.
2.--Dynamite (No. 1).
3.--Gun-cotton.
4.--Fulminate of mercury.

A.--EXPLOSIVE MIXTURES.

_Gunpowder._--This explosive mixture is composed of seventy-five parts
of nitre (saltpetre), fifteen parts of charcoal, and ten parts of
sulphur.

On being ignited, the oxygen which is feebly held by the nitrogen
combines with the carbon, forming carbonic oxide gas, whilst the
sulphur unites with the potassium of the nitre, the whole combination
being accompanied by a great evolution of heat and expansion of gas,
and the nitrogen is set free.

_Properties, &c._--A spark, friction between hard bodies, or a
temperature of 572° F., are any of them sufficient to cause an
explosion of gunpowder.

Slight moisture, due to damp air, &c., produces caking and
deterioration.

Wetting causes permanent destruction.

Frost does not injure it.

It can be fired by ordinary methods.

It can be transported and handled with safety and great ease.

It is not a suitable explosive agent for torpedoes, on account of its
liability to be injured by damp, as well as its not being sufficiently
violent, though for the sake of convenience, &c., it is often employed
for such work.

The effect produced by the explosion of a charge of gunpowder,
ignited by the ordinary method, is that of an uplifting rather than a
shattering effect.

This evil may be greatly remedied, when gunpowder is used as the charge
of a torpedo, by firing it with a detonator, by which means its fullest
explosive effect is developed.

_Picric Powder._--The picrates are salts of picric acid.

Picric acid is formed by the action of nitric acid on carbolic acid.

The picrate employed by Professor Abel is prepared from picric acid and
ammonium. This preparation, or salt mixed with nitre (saltpetre), forms
Abel's picric powder.

_Properties, &c._--It is prepared for use in a similar manner to
gunpowder, and it can be handled in the same way.

It is less violent than dynamite or gun-cotton, though much more so
than gunpowder.

It is difficult to explode it by blows or friction.

If flame be applied to it, the part touched burns, but the combustion
does not become general.

This explosive agent will probably be used for spar torpedoes, when
gun-cotton or dynamite are not employed.

B.--EXPLOSIVE COMPOUNDS.

_Nitro-glycerine._--Nitro-glycerine is formed by the action of nitric
acid upon glycerine at a low temperature.

The manufacture of this compound consists, first, in the slow mixture
of the glycerine with the acid, at a low temperature; secondly, in
washing the nitro-glycerine from the excess of acid with water.

The nitric acid before use is mixed with a certain proportion of strong
sulphuric acid, so that the water formed during the reaction may be
taken up, and thus any dilution of the nitric acid is prevented.

Nitro-glycerine is composed of carbon, hydrogen, nitrogen, and oxygen,
as indicated by the equation _C_{3}H_{5}N_{3}O_{9}_.

_Properties, &c._--At ordinary temperatures nitro-glycerine is an oily
liquid, having a specific gravity of 1·6. Freshly made it is creamy
white and opaque, but clears and becomes colourless on standing for a
certain time, depending on the temperature.

It does not mix with, nor is it affected by, water. It has a sweet,
aromatic taste, and produces a violent headache if placed upon the
tongue.

The opaque, freshly made nitro-glycerine does not freeze until the
temperature is lowered to 3°-5° below zero, F., but, when cleared, it
freezes at 39°-40° F. Nitro-glycerine freezes to a white crystalline
mass, and in this state it can be thawed by placing the vessel
containing it in water, at a temperature not over 100° F.

If flame is applied to freely exposed nitro-glycerine, it burns slowly
without explosion.

Nitro-glycerine in a state of decomposition becomes very sensitive,
exploding violently when struck, even when unconfined.

Pure nitro-glycerine does not spontaneously decompose at any ordinary
temperature, but if it contains any free acid, then decomposition
may happen. When pure, it is not sensitive to friction, or moderate
percussion. If struck with a hammer, only the particle receiving the
blow explodes, the remainder being scattered.

The firing point of nitro-glycerine is about 356° F., though it begins
to decompose at a lower temperature.

The mode of firing nitro-glycerine usually employed is that of a
fulminate of mercury detonating fuse.

Nitro-glycerine in the frozen state cannot be fired even by large
charges of fulminate.

In one instance, 1600 lbs. of liquid nitro-glycerine exploded in a
magazine containing 600 lbs. of the same substance in a frozen state,
but failed to fire the latter, only breaking it up and scattering it in
every direction.

_Dynamite._--This explosive compound is merely a preparation in which
nitro-glycerine is itself presented for use, its explosive properties
being those of the nitro-glycerine contained in it, as the absorbent is
an inert body.

Dynamite is formed of seventy-five parts of nitro-glycerine absorbed by
twenty-five parts of a porous siliceous earth or "kieselguhr."

The best substitute for "kieselguhr" is ashes of bog-head coal.

Dynamite is a loose, soft, readily moulded substance, of a buff colour.

The preparation of dynamite is very simple.

The nitro-glycerine is mixed by means of wooden spatulas with the fine
white powder (kieselguhr) in a leaden vessel.

It freezes at 39°-40° F., and when solidly frozen cannot be exploded,
but if in a pulverised state it can be exploded, though with diminished
violence.

It can be easily thawed, by placing the vessel containing it in hot
water.

Friction or moderate percussion does not explode it.

Its firing point is 356° F.

If flame be applied to it, it burns with a strong flame.

It is fired by means of fulminate of mercury, and its explosive force
is about seven times that of gunpowder.

For ground and buoyant mines, where actual contact between the hostile
vessel and the torpedo will be rarely achieved, this being next to
nitro-glycerine the most violent of all known explosive agents, and
being cheaply and readily procured, is the very best explosive for such
torpedoes.

That it is not generally adopted is owing to its containing a large
proportion of that seemingly dangerous substance, nitro-glycerine,
which makes the handling of dynamite a somewhat hazardous operation.

According to Professor Abel, there are now as many as fifteen dynamite
factories in different parts of the world (including a very extensive
one in Scotland) working under the supervision of Mr. Nobel, the
originator of the nitro-glycerine industry; and six or seven other
establishments exist where dynamite or preparations of very similar
character are also manufactured.

The total production of dynamite in 1867 was only eleven tons, while in
1878 it amounted to 6140 tons.

This explosive compound is most extensively used for general blasting
purposes all over the world, and for this purpose, owing to its
cheapness and the convenience in manipulating it, is far superior to
compressed gun-cotton.

Gun-cotton is formed by the action of concentrated nitric acid
on cotton, its composition being indicated by the formula
_CH_{7}(NO_{2})_{3}O_{5}_.

Professor Abel's process for manufacturing pulped and compressed
gun-cotton is as follows:--

Cotton waste is the form of cotton used; it is picked and cleaned,
thoroughly dried at 160° F., and then allowed to cool.

The strongest nitric and sulphuric acids are employed, mixed in the
proportion of one part of the former to three of the latter by weight.
These are mixed in large quantities, and stored in cast-iron tanks.

The cotton in 1-lb. charges is immersed in the acid mixture, which is
contained in a trough surrounded by cold water. After being subjected
to the action of the acid for a short space of time, the cotton is
taken up, placed upon a perforated shelf, and as much as possible of
the acid squeezed out of it. It is then put into jars, covered with
fresh acid, and the jars placed in fresh water, remaining there for
twenty-four hours.

To remove the acid, the gun-cotton from the jars is thrown into a
centrifugal strainer, by which nearly all the acid is expelled. It is
then diffused quickly in small quantities through a large volume of
water, and again passed through a centrifugal machine.

The next process is that of thoroughly washing the gun-cotton, for the
purpose of removing the traces of the acid still adhering to it. By
pulping, which operation is performed in pulping engines or beaters,
the washing is expeditious and thorough.

A _beater_ is an oblong tub in which is placed a revolving wheel
carrying strips of steel on its circumference. From the bottom under
the wheel project similar steel strips.

The action of this machine is as follows:--

By the rotation of the wheel, the gun-cotton which is suspended in
water circulates around the tub, and is drawn between the two sets of
steel projections, by which it is reduced to a state of _pulp_.

The bottom of the tub is movable, and thus the space through which the
gun-cotton must pass may be contracted, as the operation proceeds.

The pulping being complete, the contents are run into _poachers_ for
the final washing.

A _poacher_ is a large oblong wooden tub. On one side at the middle is
placed a wooden paddle-wheel, which extends half way across the tub.

In the poacher the pulped gun-cotton is stirred for a long time with a
large quantity of water. The revolution of the paddle-wheel keeps up a
constant circulation, and care is taken that no deposit occurs in any
part of the tub.

Having converted the cotton into gun-cotton, reduced it to a state of
pulp, and thoroughly washed it, the next process is to separate the
water from the pulp, and compress it into cakes or discs.

This is accomplished by means of two presses, the first of which has 36
hollow cylinders, in which perforated plungers work upwards.

These plungers having been drawn down, the cylinders are filled with
the water-laden pulp, and their tops covered with a weight; the
plungers are then forced up by hydraulic power, compressing the pulp,
and forcing the water to escape through their perforations.

The second one is used to more solidly compress the cylindrical masses
of gun-cotton formed by the action of the first press, a pressure of 6
tons to the inch being in this case applied.

About 6 per cent. of moisture still remains in the discs, which can be
readily removed by drying.

_Properties._--Cotton converted into gun-cotton is little changed in
appearance, though the latter is harsher to the touch than the former.

If a flame be applied to dry loose gun-cotton, it flashes up, without
explosion; if compressed it burns rapidly, but quietly.

Moist compressed gun-cotton under the same circumstances burns away
slowly.

Gun-cotton containing 12 to 14 per cent. of water is ignited with much
difficulty on applying a highly heated body. As it leaves the hydraulic
press upon being converted from the pulped state to masses, it contains
about 15 per cent. of water; in this condition it may be thrown on to
a fire or held in a flame without exhibiting any tendency to burn;
the masses may be perforated by means of a red-hot iron, or with a
drilling tool, and they may with perfect safety be cut into slices by
means of saws revolving with great rapidity. If placed upon a fire and
allowed to remain there, a feeble and transparent flame flickers over
the surface of the wet gun-cotton from time to time as the exterior
becomes sufficiently dry to inflame; in this way a piece of compressed
gun-cotton will burn away very gradually indeed.

To test the safety of wet gun-cotton, the following two experiments
among many have been made:--

Quantities of wet gun-cotton, 20 cwt. each, packed in one instance in
a large, strong wooden case, and in the other in a number of strong
packing cases, were placed in small magazines, very substantially built
of concrete and brickwork. Large fires were kindled around the packages
in each building, the doors being just left ajar. The entire contents
of both buildings had burned away, without anything approaching
explosive action, in less than two hours.

This comparatively great safety of wet gun-cotton, coupled with the
fact that its detonation in that state may be readily accomplished
through the agency of a small quantity of dry gun-cotton, termed a
"primer," which, by means of a fulminating fuze, or detonator, is
made to act as the initiative detonating agent, gives it important
advantages over other violent explosive agents, when used for purposes
which involve the employment of a considerable quantity of the
material, on account of the safety attending its storage and necessary
manipulation.

From experiments conducted by engineer officers in Austria, it was
found that if boxes containing dry compressed gun-cotton are fired into
from small arms, even at a short range, the gun-cotton is generally
inflamed, but never exploded, the sharpness of the blow essential to
effect an explosion, which the bullet might otherwise give, being
diminished by its penetration through the side of the box before
reaching the explosive. Wet gun-cotton, containing even as little as 15
per cent. of water, is never inflamed on these conditions.

Dynamite, on the other hand, is invariably detonated when struck by a
bullet on passing through the side of the box.

Gun-cotton is insoluble in and unaffected by water.

The firing point of gun-cotton is about 360° F.

The temperature of explosion of gun-cotton is about 8700° F., being
more than double that of gunpowder. Gun-cotton is not sensitive to
friction or percussion.

If not perfectly converted or thoroughly washed, gun-cotton is liable
to spontaneous decomposition, which under favourable conditions may
result in explosion.

Compressed gun-cotton is free from such danger, as it may be kept
and used saturated with water. It is stored in the wet state, care
being taken that it is not exposed to a temperature that will freeze
the water in the cakes, as if this occurs they are liable to be
disintegrated by the expansion of the water in freezing.

Gun-cotton is the agent most extensively used for all kinds of
military engineering and submarine operations in Great Britain, it
being especially manufactured by the English government for that
express purpose; but in other countries it is not so manufactured, and
therefore, as it is little used for other than military purposes, it
is not to any extent privately manufactured, as is the case with other
explosives, such as dynamite, dualine, lithofracteur, &c., and thus, in
case of war, would be somewhat difficult to obtain out of England.

Compared with dynamite, it is not so violent, and occupies more space,
weight for weight, and also requires a more complicated means of
detonating it. On the other hand, gun-cotton is infinitely safer to
store and manipulate, and is not so subject to detonation by concussion
(not being so sensitive) as dynamite.

_Fulminate of Mercury._--Fulminate of mercury is formed by the
action of mercuric nitrate and nitric acid upon alcohol. The mode of
preparation is as follows:--

Dissolve one part of mercury in twelve parts of nitric acid, and pour
this solution into twelve parts of alcohol.

Pour this mixture into a vessel which is placed in hot water until it
darkens and becomes turbid and begins to evolve dense white fumes,
then remove it from the water. The reaction goes on, with strong
effervescence and copious evolution of dense white ethereal vapours. If
red fumes appear, cold alcohol should be added to check the violence of
the action.

The operation should be performed at a distance from a fire or flame,
and in a strong draught, so that the vapours may be carried off.

When the liquid clears, and the dense white fumes are no longer given
off, further action is stopped by filling up with cold water. The
fulminate settles to the bottom of the vessel as a grey crystalline
precipitate. The liquid is then poured off, and the fulminate washed
several times by decantation or upon a filter.

Dry fulminate of mercury explodes violently when heated to 367° F.,
when forcibly struck by the electric spark, &c.

When wet it is inexplosive, and therefore it is always kept wet, being
dried in small amounts when required for use.

Fulminate of mercury is applied in many ways, either pure or mixed with
other substances, as in percussion caps, percussion powder, primers,
detonators, &c.

For the purpose of detonating nitro-glycerine or its preparations, 15
grains of the fulminate are sufficient, but to detonate gun-cotton
25 grains are necessary. The fulminate in detonating fuzes should
be enclosed in a copper case or cap, and must never be loose. The
fulminate should be wet when charging the detonators, as it is very
dangerous to handle when dry.

Great care is requisite in handling this explosive compound.

In addition to the foregoing explosive compounds and mixtures, the
following explosive agents have also been employed for the purposes of
submarine operations, though only to a small extent.

_Dualin._--Dualin is a nitro-glycerine preparation formed by mixing
sawdust and saltpetre with that substance.

This preparation, inferior to dynamite, was employed by the Germans as
the explosive agent for their submarine mines during the Franco-German
war (1870-71).

_Lithofracteur._--Lithofracteur is also a preparation
of nitro-glycerine. It is composed of the following
materials:--Nitro-glycerine, kieselguhr, coal, soda, saltpetre, and
sulphur.

This explosive agent, also inferior to dynamite, is used, though not
very extensively, by the French for their submarine mines.

_Horsley's Powder._--Horsley's powder is a chlorate mixture formed of
potassium, chlorate, and galls. This explosive mixture was formerly
used by Captain Harvey for his towing torpedo, but has recently been
discarded for compressed gun-cotton.

_Abel's Detonation Experiments._--The following are the results of
experiments carried out by Professor Abel, C.B., F.R.S., on the subject
of detonation:--

1.--A fuze containing rather more than 1 ounce of
gunpowder, strongly confined, exploded in contact with
a mass of compressed gun-cotton, _only inflames it_,
although the explosion of the fuze is apparently a
sharp one.

2.--45 grains of fulminate of mercury, exploded
unconfined on the surface of a piece of compressed
gun-cotton, only inflames or disperses it.

3.--A fuze containing 9 grains of fulminate of mercury,
strongly confined, exploded in contact with compressed
gun-cotton, or dynamite, detonates it with certainty.

4.--An equal quantity of fulminate of mercury,
similarly confined, does not detonate _uncompressed_
gun-cotton in which it is imbedded, but merely
disperses and inflames it.

5.--150 grains of compressed gun-cotton, detonated in
proximity to dynamite, _detonates the latter_.

6.--3 ounces of dynamite, and very much larger
quantities, detonated in contact with compressed
gun-cotton, only disperses it.

7.--A wrought-iron rail can be destroyed by detonating
8 ounces of compressed gun-cotton placed unconfined on
the rail.

8.--A piece of wet gun-cotton, quite uninflammable,
removed from a fire, and detonated upon a block of
granite, using a small primer of dry gun-cotton,
shatters the block.

9.--A submerged charge of wet gun-cotton, open on all
sides to the water, and merely confined around the
dry initiative, or primer, by means of a net, can be
exploded.

_Explosive Agents in Torpedoes._--The explosive agents that at the
present time are most generally used in torpedoes are gunpowder,
gun-cotton in the wet compressed state, and dynamite, and these may be
compared as to their properties and their explosive effects.

_Gunpowder._--Gunpowder is a familiar material, in general use for
all military purposes. It can be handled and transported with safety
and ease, and it can be fired by ordinary methods. But for submarine
purposes it has the disadvantage of being very easily injured by water,
so that it is absolutely necessary to enclose it in water-tight cases.

_Gun-cotton._--Gun-cotton is free from liability to accidents, and in
this matter, and the safety of its manufacture, it compares favourably
with gunpowder.

It is peculiarly adapted to submarine work, being unaffected by water.
And as it may be kept in water, ready for use, it can be safely carried
on board ship in large quantities. It is far more violent in its
action when detonated than gunpowder. The chief objection to its use
is, that being applied only for special purposes, it is not readily
obtained. Also it requires a peculiar and somewhat complicated mode of
firing it.

_Dynamite._--Dynamite is more easily manufactured than the two
foregoing explosives. The fact of it containing nitro-glycerine, which
has a bad reputation, has militated against its use as a torpedo
explosive agent, though for blasting purposes it is most extensively
used. Though not directly affected by water, its firing is hindered
when diffused through water. Another disadvantage is its high freezing
point. Like gun-cotton, it requires special means to fire it, though
much simpler, and also is much more powerful than gunpowder. The
explosive effect of dynamite or gun-cotton is a rending or a shattering
one, while that of gunpowder is an uplifting or heaving one.

Again, it is necessary when using gunpowder that the object be in the
line of least resistance, but with dynamite or gun-cotton the effect is
nearly equal in every direction, therefore for submarine operations,
either dynamite or gun-cotton is the explosive agent that should be
invariably used.

_Size of Torpedo Charges._--For permanent mines, a charge of 700 lbs.
to 1000 lbs. of gun-cotton is quite sufficient, though too large a
charge cannot be employed, except as regards the matter of convenience.

For buoyant mines, 500 lbs. to 700 lbs. of gun-cotton is an ample
charge, and for contact mines, 200 lbs. to 300 lbs. of gun-cotton is
sufficient. In spar torpedoes, where lightness is a consideration,
gun-cotton charges of 30 lbs. to 50 lbs. will be found ample, and
similarly in the case of the towing or locomotive torpedoes. Of course,
with regard to such a submarine weapon as the Lay torpedo boat, any
size charge may be carried, according to the wish of the builder.

_Torpedo Explosions illustrated._--At Fig. 166 is represented a sketch
of a torpedo explosion, from a photograph taken at the moment the
column of water was at its greatest elevation. The torpedo contained
432 lbs. of gun-cotton, and was exploded under 27 feet of water.

The height of the column thrown up measured 81 feet, and the diameter
at the base 132 feet.

[Illustration: SUBMARINE MINE EXPLOSION.

PLATE LII]

[Illustration: SUBMARINE MINE EXPLOSIONS.

PLATE LIII]

At Fig. 165 is shown a sketch of two submarine mine explosions from
an instantaneous photograph; the schooner which is shown in
the sketch happened to be passing at the moment of explosion, thus
affording a comparison as to the size of the columns of water thrown up.

The column on the left was due to the explosion of a submarine mine
containing 100 lbs. gunpowder at a depth of 10 feet below the surface.
That on the right was the result of an explosion of a similar mine, but
at a depth of 41 feet below the surface. Its extreme height was 400
feet.

CHAPTER IX.

TORPEDO EXPERIMENTS.

THE following are some of the more important torpedo experiments that
have been carried out in England and Europe, to investigate the subject
of submarine explosions as applied to ships and to mines, &c., these
experiments extending over a space of thirteen years.

_Experiment at Chatham, England, 1865._--This experiment was carried
out to ascertain the effect of gunpowder torpedoes on the bottom of a
wooden ship.

Target:--H.M.S. _Terpsichore_, a wooden sloop of war.

Torpedo:--150 lbs. of fine-grained powder. Two were used. They
were placed on the ground, about 13' below the ship's keel, and 2'
horizontally clear of her side.

Effect of explosion:--A hole of about 4' radius was made, about 19'
nearly vertical from the charge; the _Terpsichore_ sinking a few
minutes after the explosion.

_Experiment in Austria._--The object of this experiment was to
ascertain the effect of a very large charge of gun-cotton exploded at
some distance from the side of a wooden vessel.

Target:--A wooden sloop.

Torpedo:--400 lbs. of gun-cotton, placed 10' below the surface of the
water, and 24' horizontally from the bottom of the vessel.

Effect of explosion:--Complete destruction of the vessel.

_Experiments at Carlscrona, Sweden, 1868._--These experiments were
made to investigate the effect of submarine contact mines, charged
with dynamite, against a strong wooden vessel, as well as against
a double-bottomed iron vessel. They were carried out under the
supervision of Lieut.-Colonel Zethations, of the Royal Swedish Navy.

Target:--The hull of a 60 gun frigate, which had been built in 1844;
it had been cut down to the battery deck, and the copper removed.
Her timbers and planking were quite sound; timbers of oak about
13" square, and 1" apart; planking of Swedish pine, 5-1/2"; bottom
strengthened inside with wrought-iron diagonal bands, 6" by 1-1/4";
inside planking running half way up to the battery deck of oak; 6"
thick. This completes the wooden target.

On the port side a quadrangular opening was made, and fitted with a
construction representing a strong double iron bottom, firmly fastened
to an oaken frame that had been put on inside, on the four sides of the
opening, and with through-going bolts, 1" in diameter, to the timbers.

Torpedoes:--No. 1.--13 lbs. dynamite, enclosed in 1/12" iron case. It
was placed on the starboard side, amidships, 7' below the water line,
and 2' 2" from the bottom of the ship.

No. 2.--16 lbs. dynamite, enclosed in a glass vessel. It was placed on
the starboard side, 7-3/4' below the water line, 3' from the bottom of
the ship, and 40' from her stern.

No. 3.--16 lbs. dynamite, enclosed in 1/12" iron case. It was placed on
the port side, 5-3/4' below the water line, 2' from the bottom of the
ship, and 30' from her stern.

No. 4.--10 lbs. dynamite, in a case as above. It was placed on the port
side, 6-1/2' below the water line, 2-1/6' from the bottom of the ship,
and 70' from her stern.

No. 5.--13 lbs. dynamite, in case as above. It was placed 7-1/3' below
the water line, 2-1/6' from the centre of the _iron_ bottom.

These five torpedoes were fired at the same moment.

Effect of explosion:--The hull of the ship was lifted about a foot, and
sunk in 1-1/2 minutes.

No. 1 Mine.--Timbers broken and thrown inside, into the hold, on a
space of about 15' × 8'; three more timbers on one side of this hole
broken; inside oak planking rent off on a length of 14'; two iron bands
torn up and bent, one of them broken in two places; outside planking
torn off on a space of 21' × 12'; several planks still higher up broken.

No. 2 Mine.--Timbers blown away on a space of about 8' square; inside
planking torn off on a length of 20'; two iron bands broken, and torn
up and bent; and outside planking rent off on a space of 19' × 12'.

No. 3 Mine.--Timbers blown away on a space of 10-1/2' × 12' at one end,
and 6' at the other; inside planking off for a length of 14'; one iron
band torn up, and one broken; outside planking off on a space of 18' ×
25' × 15'.

No. 4 Mine.--Timbers blown away on a space 4' × 16'; on the sides of
this hole, ten timbers were broken; two iron bands torn up, and one
broken; inside planking off for a length of 20'; outside planking off
for a space of 20' × 23' × 10', and 13 feet.

No. 5 Mine.--The gas sphere of this mine had hit the middle of the
outside plates on one of the angle-iron ribs. This rib was torn from
the timbers and bent up, nearly 2' in the middle, but not broken. There
was an oval hole in the outside plates 4' × 3' between two ribs, which
ribs, with the plates on edge riveted to them, were bulged out about
5 inches. The inner plate, one large piece was blown up in a vertical
position, after having cut all the bolts and rivets, sixty of 1", and
thirty of 3/4", save those that fastened the lower side to the oaken
frame and timbers. On a length of 30' and height of 20', the bottom, on
all sides of the iron construction, had been bent inwards; the greatest
bend was about 5"; three deck beams above had been broken.

By the joint effect of all the mines, almost all the iron deck beam
knees had been rent from the side, and there was an opening between
deck and hull on both sides for a length of about 130 feet.

_Experiment at Kiel._--Target:--A large gun-boat, greatly strengthened
internally by solid balks of timber.

Torpedo:--200 lbs. gunpowder. It was placed nearly under her keel, at a
distance of 15 feet.

Effect of explosion:--Complete destruction of the vessel.

_Experiment in England, 1874._--Target:--A rectangular iron case 20'
long, 10' high, and 8' wide, divided into six compartments by means of
one longitudinal bulkhead midway between the front and rear faces of
the target, and two athwartship bulkheads equidistant from the ends of
the target. Thickness of front and rear faces 11/16", of longitudinal
bulkhead 1/4", of athwartship bulkheads 3/8".

Torpedo:--100 lbs. of gunpowder, enclosed in a spar torpedo case and
fired by two detonators. It was exploded in contact with the target,
7-1/2' below the surface of the water, and 7' from top of target.

Effect of explosion on the target:--"Front of centre compartment
destroyed and top blown off. Plate representing inner skin destroyed.
Back of centre compartment (rear face of the target) much bulged, and
penetrated; the hole measured 36' × 15". Large portions of the target
were thrown to a height of 150 to 200 feet, and from 80 to 100 yards'
distance."

The effect of explosion on a ship's pinnace, which had been placed
16 feet from and at right angles to the front face of the target,
with steam up, and canopy and shield in position, was that a large
quantity of water was thrown back in the boat, putting the fires out,
and filling the boat up to her thwarts, but otherwise the boat was
uninjured.

_Experiments at Copenhagen, Denmark, in 1874._--The object of these
experiments was to ascertain if a ship's armoured side would be
seriously injured by a torpedo exploded in contact with it.

1ST EXPERIMENT.

Target:--1" thick, and 2' × 2', supported in a horizontal position on a
substructure consisting of 8" timber resting on two pieces of 6" timber
under two sides, and completely supported by earth up to lower edge of
substructure.

Torpedo:--33 lbs. of dynamite, enclosed in a square wooden case 2-1/4"
high, and 5·5" × 5·5"; it was placed on the middle of the earth with 8"
of earth tamping; this tamping representing the resistance of a thin
stratum of water.

Effect of explosion:--The plate was broken into four pieces, and
substructure crushed.

2ND EXPERIMENT.

Target:--2" thick, and 2' × 2-1/2', supported in a horizontal position
on a substructure as above, but resting on four piles of 6" x 6" timber.

Torpedo:--8·9 lbs. of dynamite, enclosed in a wooden case 4" high, and
5" × 10". It was laid with one edge on the plate, the other edge 3"
above the plate; same tamping as above.

Effect of explosion:--The plate broken into three pieces, and
substructure crushed.

3RD EXPERIMENT.

Target:--5" thick, and 3' 8" × 4' 7", supported in a horizontal
position on a substructure as above, but eight piles of 6" × 6" timber
used. Plate bolted to the structure with eights.

Torpedo:--44·4 lbs. of dynamite, enclosed in a wooden case, of same
thickness as the Harvey torpedo, and 4" × 13" × 21"; it was placed with
surface against the plate, one edge 2" and the other 5-1/2" from the
plate; tamping as before.

Effect of explosion:--Plate bulged 3-1/4" in the middle; substructure
completely crushed.

4TH EXPERIMENT.

Target:--5" thick, and 3' 8" × 4' 7"; this was the same plate as used
in the previous experiment, laid with bulge uppermost on two beams
under the short sides.

Torpedo:--44·4 lbs. of dynamite, enclosed in a cylindrical tin box
7-1/2" × 2'; it was placed on top of plate 11" from one side and with
ends 9-1/2" from edge of plate; tamping as before.

Effect of explosion:--A corner of the plate broken off.

5TH EXPERIMENT.

Target:--Same plate placed vertically in the earth.

Torpedo:--44·4 lbs. of dynamite, enclosed in a cylindrical tin box 8·5"
× 18"; it was placed on timber, so as to rest against the face and
centre of the plate; tamping as usual.

Effect of explosion:--Plate broken into four pieces, two of which were
large; pieces hurled over parapet, one fell at a distance of 400 feet.

_Experiments at Carlscrona, Sweden, in 1874-75._--These experiments
were carried out by the Swedish torpedo authorities, to ascertain the
effect of different sized charges of dynamite and gunpowder, enclosed
in divers cases, and exploded at various distances from a target which
represented in all respects, with the exception of the armour, a
section of the side of H.M.S. _Hercules_ before the boiler room, she
being at that time one of the most powerful vessels afloat.

Target:--32' in length, and fitted into the side of an old line of
battle ship. Similar in shape to a wing tank, and comprised a double
bottom in four water-tight compartments, a wing passage in two
water-tight compartments, and two large water-tight compartments in
rear of all. It extended from 2' above the water line to within about
5' of the vessel's keel. The thickness of the plates forming the
target were:--outer bottom, lower portion 13/16"; part where torpedo
took effect, 3/4". Inner bottom, and wing passage bulkhead, 1/2".
Vertical and longitudinal frames, both solid and bracket, 7/16". The
longitudinal frames were bracket frames, with the exception of the
second, which was solid and water-tight, with its outer edge about 8'
below the water line. The vertical frames, of which there were seven,
were placed 4' apart, the central one being solid and water-tight,
the others being bracket frames. The ship was moored in 42 feet of
water; the charges were detonated, one fuze being used in all but No. 3
experiment, when five fuzes were employed.

1ST EXPERIMENT.

Torpedo:--33 lbs. of dynamite, enclosed in cylindrical steel case, no
air space; height 10·75", diameter 10·75", and thickness 1/32". It was
placed 25·5' from the target, opposite No. 7 frame, and 9·25' below the
surface of the water.

Effect of explosion:--Ship appeared to be lifted bodily. A rivet in the
midship longitudinal bulkhead of fore compartment was loosened. The
torpedo was fired from the ship, and the shock felt was not very great.

2ND EXPERIMENT.

Torpedo:--47·2 lbs. of dynamite, in cylindrical steel case, no air
space; height 12", diameter 12", and thickness 1/32". It was placed
25·5' from No. 5 frame, 9·25' below the surface of the water.

Effect of explosion:--Ship appeared to be lifted bodily. A leak was
started in the outer bottom opposite to charge, caused by the loosening
of five rivets.

3RD EXPERIMENT.

Torpedo:--112 lbs. of gunpowder, rifle small grain, enclosed in
cylindrical steel case placed inside an iron case, with an air space
all round; steel case, 9-1/2" × 22-1/2" × 1/32"; iron case 33" × 25" ×
1/4". It was placed 12' from No. 5 frame, 9·25' below the surface.

Effect of explosion:--Centre of ship lifted bodily, as if her back was
broken; ship then rolled heavily to port. On board fire engines and
troughs displaced several feet: shores and struts started, showing
that the shock was considerable. The outer bottom on each side of
the centre dividing plate indented to a depth of 1 to 1-1/2 inches;
numerous rivets started, and some sheared. The leak was considerable,
owing to the number of rivets that were started. The strength of
the plates was not considered to be materially affected by the
indentations; the rivets, 239 in number, were replaced; and the target
prepared for the next experiment.

4TH EXPERIMENT.

Torpedo:--33 lbs. of dynamite, enclosed as in first experiment. It was
placed 15' from No. 7 frame, 9·25' below the surface of the water.

Effect of explosion:--Ship rolled slightly to port. A bolt securing the
midship transverse bulkhead to beam was sheared. No damage done to the
target.

5TH EXPERIMENT.

Torpedo:--66 lbs. of dynamite, enclosed in steel cylindrical case, no
air space, 13·5" × 13" × 1/32". It was placed 21' from No. 3 frame,
9·25' below the surface of the water.

Effect of explosion:--A rivet in outer bottom, above water line at
fore end of target, was sheared. A few rivets in outer bottom opposite
charge, and two in after compartment, were started, but no leak was
perceptible. Several shores slightly displaced.

6TH EXPERIMENT.

Torpedo:--33 lbs. of dynamite, enclosed as in first experiment. It was
placed 12·75' from No. 7 frame, 9·25' below the surface of the water.

Effect of explosion:--Ship not lifted as much as was the case in No.
3 experiment; but explosion much sharper. On board, fire engines were
capsized, and vertical shores displaced. Outer bottom opposite charge
indented to a depth of about 1/2 an inch, other parts less bulged, and
many rivets started.

7TH EXPERIMENT.

Torpedo:--33 lbs. of dynamite, enclosed as in first experiment. It was
placed 4' from No. 4 frame, 9·25' below the surface of the water.

Effect of explosion:--Effect very great; ship hurled suddenly to
starboard. On going on board two minutes after the explosion, the
fore compartment was found full, the after compartment became full
ten minutes later. Shores and struts were considerably displaced,
and there was evidence that the ship had sustained a severe shock.
Outer bottom injured over an area 14' × 16', the plates being split
in all directions; one piece, 5' square, was torn completely off,
and an irregular hole was formed in the outer skin 14' × 12'. In the
inner bottom below the wing passage bulkhead a piece 6' × 9' was
blown completely out; the wing passage bulkhead was torn from the
longitudinal frame and split from top to bottom. The inner skin above
the upper longitudinal frame was torn from the latter, and forced in
and upwards, but was not otherwise damaged. The vertical bracket frames
Nos. 3 and 4, the latter opposite the torpedo, were destroyed, but the
solid frame No. 5 was almost uninjured. The outer bottom, where it was
not torn off, was forced in 7', or 4' beyond where the _inner_ bottom
had been.

8TH EXPERIMENT.

Torpedo:--660 lbs. of gunpowder, enclosed in a buoyant cylindrical
1/4" iron case. It was placed 32·3' from No. 4 frame, 29·25" below the
surface of the water.

Effect of explosion:--The ship and target had been thoroughly repaired,
and were in good condition when this experiment was made; the ship was
in this case moored in 65 feet of water. No effect was produced on the
target by the explosion.

9TH EXPERIMENT.

Torpedo:--19 lbs. of dynamite, enclosed in a cylindrical steel case
with arched ends. It was placed 10·5' from No. 3 frame, 9·25' below the
surface of the water.

Effect of explosion:--Effect produced apparently equal to that by No. 3
charge of 112 lbs. of gunpowder at 12'; indentation being from 1/2 to
1-1/4 inches in the outer skin opposite the torpedo.

10TH EXPERIMENT.

Torpedo:--19 lbs. of dynamite, enclosed in a case similar to that used
in the 9th experiment. It was placed 3·3' from No. 7 frame, 9·25' below
the surface of the water.

Effect of explosion:--Hole produced in outer skin, 6·5' × 2' to 5';
inner skin only bulged and slightly cracked in two places. Above the
longitudinal frame, a bulge was made in the outer skin 8' × 7', with
the above-mentioned hole; below the longitudinal frame the indentation
was 14' × 5' and 2·1" deep, with two horizontal cracks 10' x 13', and
several inches broad.

11TH EXPERIMENT.

Torpedo:--112 lbs. of gunpowder, enclosed in a cylindrical case of
3/64" steel, placed in a 3/16" steel case, with 223 lbs. of buoyancy.
Ignition effected by a glass igniting bottle. It was placed 5·75' from
No. 5 frame, 9·25' below the surface of the water.

Effect of explosion:--There was but little upcast of water outside the
ship, but a great upcast through the ship. She immediately lurched to
starboard, and on boarding her five minutes after, the target was found
full of water.

The effect on the target was as follows, above the 2nd longitudinal
frame, where strengthened by the wing passage bulkhead:--Outer bottom
blown away from the 4th to the 6th frames for a length of 8 feet and a
height of 4-1/2 feet, and bent in 6-1/2 feet. Inner bottom bent in and
broken through between the 4th and 5th frames, with an irregular hole
8' square, and between the 5th and 6th frames, a similar sized hole.
Wing passage bulkhead was bent in 2" to 3", and riven for a length of
29'; in the water-tight middle bulkhead athwartships the rivets in two
vertical joints were completely torn away.

Between the 2nd and 3rd longitudinal frames, and below the wing passage
bulkhead, both the inner and outer bottoms were completely blown away
for a length of 12 feet and a height of 4 feet. The vertical and
horizontal frames between the two bottoms had kept their position
unchanged, and excepting that the bracket plate by frame No. 6 was
bent, cracked, and torn away, the damage they had sustained was limited
to some comparatively slight bending. The open hole formed in the
target measured 76 square feet in outer bottom, and 60 square feet in
inner bottom.

Comparing the effect of this torpedo with the 7th, 33 lbs. of dynamite;
with the latter charge the breach was made at the cost of the bottom
plates as well as the vertical and longitudinal frames, which were
completely torn asunder and strained; with the gunpowder charge,
only the bottom plates were broken through, whilst the plates whose
directions were nearly parallel to the lines of explosive effect were
but little affected.

_Experiments at Portsmouth, England, 1874-75._--The object of these
experiments was to ascertain the effect of 500 lbs. gun-cotton
torpedoes exploded at various distances from a target representing the
double bottom of H.M.S. _Hercules_.

They were carried out in Stokes Bay, under the supervision of officers
belonging to the torpedo department of the Royal Engineers, and a
torpedo committee, composed of naval and military officers.

The _Oberon_, the vessel chosen for these experiments, was fitted
with a double bottom, representing as nearly as possible that of the
_Hercules_ without the armour; also with a surface condenser, and its
connections; a donkey Kingston feed-valve; and athwartship water-tight
bulkheads, which divided the ship into seven water-tight compartments.
The outer skin was composed of 3/16" and 7/8" iron plates. In her
starboard side at different points were fixed forty-four crusher
gauges, and over each side were suspended six shots, each fitted with a
crusher gauge.

Displacement of the _Oberon_ about 1100 tons.

The ship was anchored head and stern. Her mean draught of water during
the experiments was 11 feet.

1ST EXPERIMENT.

Torpedo:--500 lbs. of gun-cotton, in discs saturated with water, and
enclosed in an iron cylindrical case, 34" × 30" × 1/4", with arched
ends; the primer consisted of two dry discs, and two detonators. It was
placed 101' horizontal from the target, and opposite the condenser on
the starboard side; 47' below the surface of the water, on the ground.

Effect of explosion:--No damage was done to the hull, or condenser, but
light articles, such as bunker plates, gratings, tank lids, &c., were
displaced.

2ND EXPERIMENT.

Torpedo:--As in first experiment. It was placed on the ground, 80'
horizontal and opposite the condenser on the starboard side, 48' below
the surface of the water.

Effect of explosion:--No damage was done to the hull, of condenser,
but the bunker plates, gratings, &c., were displaced to a greater
extent than in the previous experiment.

3RD EXPERIMENT.

Torpedo:--As before. It was placed on the ground, 60' horizontal, and
opposite the condenser on the starboard side; 47' below the surface of
the water.

Effect of explosion:--No damage was done to the hull. Flanges of the
condenser inlet pipe were cracked, and several of the joint bolts were
broken. The condenser had been thrown up bodily, and had torn away its
holding down bolts; but it was not as well secured as it would have
been had it formed part of the machinery of a ship.

4TH EXPERIMENT.

Torpedo:--As before. It was placed on the ground, 50' horizontal, and
opposite the condenser on the starboard side; 48' below the surface of
the water.

Effect of explosion:--Outer bottom on starboard indented over a length
of about 100', being forced in between the frames; maximum indentation,
3/4". Many bracket frames were disturbed, and outer angle iron of
water-tight longitudinal was started for a length of 30', and made to
leak slightly. The shell of the condenser was cracked in two places,
3' and 5' in length. Bolts securing condenser, and flanges of pipes
and valves, were all more or less damaged. Condenser was rendered
unserviceable.

5TH EXPERIMENT.

Torpedo:--Same charge as before, but the primer consisted of four dry
discs, and two detonators. It was placed 28·5' horizontal, opposite
No. 9 frame, on the starboard side, 36' from the stern; 48' below the
surface of the water, and 22' from the ground.

Effect of explosion:--Bow observed to be lifted several feet. Several
angle irons and bracket frames were cracked, and numerous rivets in
outer bottom were broken off. The outer bottom on the starboard side
was indented between the frames, and brackets were disturbed over a
space of 100 feet; inner bottom uninjured.

6TH EXPERIMENT.

Torpedo:--As in previous experiment. It was placed on the ground, 28·5'
horizontal, opposite No. 36 frame on the starboard side, and 30 feet
from the stern; 49·5' below the surface of the water.

Effect of explosion:--Several plates in the outer bottom were cracked,
and outer bottom made to leak in several places, owing to the
fractures in the plates, rivets being started, and seams being opened.
Considerably more damage was effected than in previous experiment, but
inner bottom still remained uninjured.

7TH EXPERIMENT.

Torpedo:--As in the 5th experiment. It was placed on the ground,
immediately under the edge of the outer bottom, 39-3/4' from the
target, and opposite No. 18 frame, 70' from the stern; 50' below the
surface of the water.

Effect of explosion:--Outer and inner bottom broken entirely asunder
at No. 19 frame on the starboard side, and between Nos. 16 and 17 on
the portside. A fracture was caused in the outer bottom extending from
the shelf plate to upper edge of strake next the keel on the starboard
side, and from the shelf plate to upper edge of flat keel plate on the
port side. A fracture was also caused in the inner skin extending from
the topside to the outer edge of the garboard strake on the starboard
side, and from the topside to upper edge of garboard strake on the port
side; this including a fracture of the keel at No. 17. The vertical
keel, the longitudinals, as well as numerous bracket plates and angle
irons, were broken, and about 2000 rivets in the outer bottom were
rendered defective.

The outer bottom was indented over a considerable length, the
indentation being greatest between the frames, and the maximum being
8 inches. The inner bottom was not indented or damaged, with the
exception of the fractures before mentioned.

_Experiments at Pola, Austria, 1875._--These experiments were carried
out to determine the effect of very heavy charges of dynamite on an
iron pontoon fitted with a double bottom, similar to that of H.M.S.
_Hercules_.

Target:--An iron pontoon 60' long and 40' beam, with circular ends and
fitted with a double bottom, also a condenser and two Kingston valves.

1ST EXPERIMENT.

Torpedo:--617 lbs. of dynamite. It was 62' horizontally from the keel,
53' actual distance from the side, and opposite amidships, 40·5' below
the surface of the water, and 20' from the ground.

Pontoon:--Draught of water 19', and moored in 62' of water.

Effect of explosion:--The pontoon moved away bodily a distance of 13
feet; a few rivets in the outer bottom were started, and the outer skin
was slightly indented between the frames; the maximum indentation being
1·5". No other damage was sustained by the hull. Several of the screws
securing the flanges of the Kingston valves were slightly loosened.

2ND EXPERIMENT.

Torpedo:--585 lbs. of dynamite. It was placed 60' horizontally from the
keel, 48' actual distance from the side, and opposite amidships; 36'
below the surface of the water, and 42' from the ground.

Pontoon:--Draught of water 19·5', and moored in 74' of water.

Effect of explosion:--The pontoon, which had been more rigidly moored
than in the previous experiment, was moved bodily away a distance of 4
feet. Many rivets were loosened, and a few connecting the angle irons
were sheared; also the outer skin was slightly indented. No damage was
done to the condenser or Kingston valves.

_Experiment in the Sea of Marmora, 1875._--This experiment was carried
out by Turkish officers attached to their naval school at Halki, an
island in the Sea of Marmora, about eight miles from Stamboul. It
consisted in destroying a Turkish schooner by the explosion of an
100-lb. gun-cotton mine in contact with her, moored in 58 feet of
water, and 10 feet beneath the surface.

_Experiment at Carlscrona, Sweden, 1876._--This experiment was a
continuation of those previously carried out in 1874-75, and which have
been detailed at page 224, &c.

Target:--The same as had been used for the previous experiments
(1874-75), and which had been thoroughly repaired.

EXPERIMENT.

Torpedo:--660 lbs. of gunpowder, enclosed in a buoyant cylindrical 1/4"
steel case with domed ends, and contained in an inner 1/16" steel
case. It was ignited by two Von Ebner fuzes placed in a charge of 1/4
lb. of gunpowder and enclosed in a glass bottle. It was placed 5'
horizontally from the water line, 23·75' actual distance from target,
and opposite No. 5 (middle) frame of target, 29' below the surface of
the water.

Effect of explosion:--The ship was moored in 54' of water. She was
lifted by the explosion, rolled over to port, and then settled to
starboard, sundry large pieces of timber being thrown up in the
air. The outer bottom of the target was broken through above the
second longitudinal frame, from the fourth to the seventh frames
laterally, and from the top of the target to the second longitudinal
frame vertically, the hole made measuring about 9' high by 12' wide,
or about 100 square feet in area. The inner bottom was also broken
through between the top of the target and second longitudinal frame,
and between the fourth and seventh vertical frames, the hole made
being about 75 square feet in area. The bracket frames within the
damaged area were but little damaged. The wing passage bulkhead was
broken through opposite to Nos. 5 and 7 frames, the holes made being
respectively 18 and 17 square feet in area. Through these holes the
force of the explosion had made its way to the horizontal iron deck,
forming the top of the target, which was completely broken through a
little abaft No. 5 frame, the hole made measuring about 100 square feet
in area. A piece of this iron deck, weighing, with the iron fastenings
attached to it, about 1650 lbs., was thrown 16' against the upper deck
beams. The target below the second longitudinal frame was comparatively
but little injured. The outer bottom was indented and cracked in one
or two places, but the inner bottom was uninjured. In addition to the
damage to the target, the ship herself sustained serious injury, eleven
of the lower deck beams, with their knees being broken (six being
broken completely across). The main keel immediately under the target
was also opened at the scarf, and the back of the ship was apparently
broken. The hull had given out laterally to such an extent as to
prevent the ship being taken into dock.

_Experiments at Portsmouth, England, 1876._--The object of the
following experiments was to determine the effect of comparatively
small charges of gunpowder and gun-cotton exploded in actual contact
with an ironclad, as would be the case in a torpedo attack either with
locomotive towing or spar torpedoes.

Target:--the same as used in the experiments of 1874-5, which have
been detailed at page 229, &c., viz., the _Oberon_ fitted to represent
H.M.S. _Hercules_ without the armour. Her mean draught was 11', and
she was moored in 26-1/2' of water. The _Oberon_ had been placed in a
thorough state of repair.

1ST EXPERIMENT.

Torpedo:--60 lbs. of gun-cotton in slabs, saturated with water. Total
weight of charge 75 lbs. It was enclosed in a 1/4" iron case with cast
iron ends. It was placed at 15' actual distance from the nearest side
of the case to the target, and opposite No. 4 frame on the port side,
10' below the surface of the water.

Effect of the explosion:--The effect upon the vessel was unappreciable.
This charge represented the large Whitehead fish torpedo, and its
position corresponded to that of this torpedo when striking a net at a
small angle with the keel.

2ND EXPERIMENT.

Torpedo:--The Harvey towing torpedo, charged with 66 lbs. of gunpowder,
primed with gunpowder, and fired by means of an electric fuze. It was
placed at 3' actual distance from the target, measuring from the centre
of the torpedo, and opposite No. 4 solid frame on the starboard side,
the vertical axis of the torpedo being at right angles to the vessel's
side, 9-1/4' below the surface of the water.

Effect of explosion:--This and the two following torpedoes were fired
simultaneously. The outer bottom was blown in from the upper edge of
the flat keel plate to the underside of the water-tight longitudinal,
and fore and aft from No. 2 to No. 6 frames; an area 16' × 8-5/6'. Flat
keel plates were broken between No. 2 and No. 4 frames, and the 4th
strake of the bottom plating was broken, and the frames for that space
blown in. Two holes were blown through the inner bottom, measuring
respectively 2' × 2' and 7' × 1', making the total area of the inner
bottom destroyed, 11 square feet.

3RD EXPERIMENT.

Torpedo:--33 lbs. of granulated gun-cotton, saturated with water; total
weight of charge being about 41 lbs. It was enclosed in a 1/4" iron
case, 12-1/2" × 12" × 12-1/2", the primer being 2-1/2 lbs. of slab
gun-cotton, included in the 33 lbs. It was placed at 4' actual distance
from the target, measuring from the centre of the case, and opposite
No. 30-1/2 solid frame on the starboard side; 9-1/4' below the surface
of the water.

Effect of explosion:--Outer bottom blown in from upper edge of the
lower longitudinal to the lower edge of the upper longitudinal between
Nos. 28 and 32 frames; an area of 18 × 11 feet. The butts of the flat
keel were started and the plating broken across No. 30-1/2 frame from
the flat keel plate to the upper deck. Shelf plate at Nos. 30-1/2 and
32-1/2 frames was broken. Nos. 29, 30, and 31 frames were blown in from
first to third longitudinal; lower longitudinal from No. 28 to 31 also
blown in. Two holes were blown through the inner bottom, measuring
respectively 6 × 1·5' and 5' × ·25', making the total area of inner
bottom destroyed 10 square feet. A steam launch with steam up and
outrigger torpedo gear in place, one pole being rigged out, was placed
with the stem of the boat 22' horizontally from the torpedo. She was
uninjured and shipped very little water.

4TH EXPERIMENT.

Torpedo:--31 lbs. 14 oz. of gun-cotton in slabs, saturated with water,
total weight about 40 lbs. It was enclosed in a 1/4" iron case 12-1/2"
× 12-1/2" × 6"; primer being 20 oz. of gun-cotton, included in the
31 lbs. 14 oz. It was placed at 4' actual distance from the target
measuring from the centre of the case, and opposite No. 30-1/2 solid
frame on the port side; 9-1/4' below the surface of the water.

Effect of explosion:--Outer bottom and frames injured in a similar
manner to that described in the third experiment. Outer angle irons of
the 1st, 2nd, and 3rd longitudinals were started in the wake of the
broken place. A hole was blown through the inner bottom, measuring 9·5'
× 1', or about 10 square feet in area. The bolts of the outer bottom
plate of stern post much open, and at Nos. 16 and 17 on the port side
the upper two strakes were buckled and the shelf plate started.

A steam launch, arranged in the same manner as in the fourth
experiment, was uninjured, and shipped but little water.

_Experiments with Countermine._--The following experiments have been
carried out in England and other countries to ascertain some reliable
data for countermining operations.

1ST EXPERIMENT.

_Experiments in the Medway, England, 1870._--Countermine:--432 lbs. of
compressed gun-cotton, enclosed in a 3/16" iron case. It was moored at
a depth of 37' below the surface of the water.

Submarine mines:--A series of similar cases containing coal dust, &c.,
were moored at distances of 50' to 100' from the countermine, and 37
feet below the surface.

Effect of explosion:--The submarine mine at 80' distance was completely
destroyed; the dome of its circuit closer was dented in.

2ND EXPERIMENT.

Countermine:--As before, but moored 27' below the surface.

Submarine mines:--As before, but moored at distances of 70' to 120'
from the countermine, and 27' below the surface.

Effect of explosion:--The submarine mine case at 120' distance was
dented, but remained water-tight; the copper guard of fuze piece
collapsed, and the earth connection of the fuzes was ruptured; the dome
of its circuit closer was dented.

3RD EXPERIMENT.

Countermine:--As before, but moored 47' below the surface.

Submarine mines:--As before, but moored at distances of 70' to 200'
from the countermine.

Effect of explosion:--The submarine mine case at 200' distance was
dented, but it did not leak.

1ST EXPERIMENT.

_Experiments at Stokes Bay, England, 1873._--Countermine:--500 lbs. of
gun-cotton, enclosed in a 3/16" iron case. It was placed on the ground,
in 47' of water.

Submarine mines:--Six ground mines, 1/4" thick cases, fitted with
circuit, 10' below the surface, at distances of 100' to 200' from the
countermine.

Effect of explosion:--Submarine mines at 100' and 120' distance were
destroyed, and their circuit closers thrown out of adjustment;
submarine mines at 140' and 170' distance were much bulged, and leaked,
and their circuit closer spindles were bent; submarine mine at 200'
distance was uninjured, but its circuit closer was thrown out of
adjustment.

2ND EXPERIMENT.

Countermine:--100 lbs. of gun-cotton enclosed in case, thickness No. 12
B. W. G. It was moored 10' below the surface, in 35' of water.

Submarine mines:--Five similar mines placed at same depth, at distances
of 50' to 150' from the countermine.

Effect of explosion:--The submarine mine at 50' distance showed
continued or dead earth, two screws broken, and its case dented; the
other mines were uninjured.

1ST EXPERIMENT.

_Experiments at Carlscrona, Sweden, 1874._--Countermines:--226 lbs. of
dynamite, enclosed in a case 17-1/2" × 20" × 1/8". It was moored 9-3/4'
below the surface, the depth of water being 41 feet.

Submarine mines:--(_a_) cast iron ground 600 lb. mines, dome shaped,
48-3/4" × 21-1/2" × 2"; (_b_) cylindrical cases, wrought iron, empty,
11-1/2" × 11-1/2" × 1/8"; (_c_) cylindrical cases, wrought iron,
charged, 11-1/2" × 11-1/2" × 1/8"; (_d_) cylindrical cases, wrought
iron, 30-1/4" × 30-1/4" × 1/8"; (_e_) spherical cases, wrought iron,
32-1/2" × 1/8"; (_f_) spherical cases, tinned steel, 12" × 1/8".

Effect of explosion:--(_b_) mine, at 34' distance, was destroyed, and
one at 92' distance was slightly bulged; (_c_) mine, 58' distance,
mouthpiece injured and case leaky; (_d_) mine, 244' distance, a rivet
started.

2ND EXPERIMENT.

Countermine:--As before, but moored at 29-1/4' below the surface; depth
of water, 41 feet.

Submarine mines:--As before.

Effect of explosion:--(_a_) mine, at 146' distance, split in two; (_b_)
mine, 34' distance, destroyed; at 49' distance, fractured; at 68'
distance, indented but not fractured; (_c_) mine, 58' distance, case
much bulged, and leaky; (_d_) mine, at 244' distance, rivets started,
case half full of water; at 195' distance, sunk, several rivets
started; (_e_) mine, at 195' distance, bolt loosened; (_f_) mine, at
68' distance, not injured.

3RD EXPERIMENT.

Countermine:--453 lbs. of dynamite, enclosed in a case, 24-1/2" ×
28-1/4" × 1/8". It was moored 9-3/4' below the surface; depth of water
as before.

Submarine mines:--As before.

Effect of explosion:--(_b_) mine, at 49' distance, sunk and not
recovered; at 58' distance, very much indented; (_c_) mine, at 58'
distance, case much indented and leaky; (_f_) mine, at 48-1/2'
distance, uninjured.

4TH EXPERIMENT.

Countermine:--As before, but moored 29-1/4' below the surface.

Effect of explosion:--(_a_) mine, at 195' distance, completely stove
in; (_c_) mine, at 58' distance, case indented but charge dry; (_e_)
mine, at 175' distance, slightly leaky; (_f_) mine, at 48-1/2'
distance, upper half indented in three places. It was also discovered
during the above experiments that submarine mines charged with dynamite
can be caused to explode by the detonation of a charge of the same
explosive, at distances from it considerably beyond those at which
the cases themselves are damaged by a similar charge. To prevent the
foregoing, it is necessary to pack the dynamite very carefully, using
at the same time special precautions.

CHAPTER X.

THE ELECTRIC LIGHT--TORPEDO GUNS--DIVING.

ELECTRIC lights combined with fast steam launches as guard boats
and specially constructed torpedo guns, such as the Nordenfelt and
Hotchkiss machine guns, are at the present time the only _truly
practicable_ means afforded to a man-of-war of defending herself
against the attack of torpedo boats, whether these latter are armed
with the spar, fish, or towing torpedo; the torpedo gun sinking the
boats after the electric light and guard boats have detected their
approach and position.

As has been before stated, nets, shields, booms, &c., placed around
a vessel of war, must, however slightly constructed, affect to a
considerable degree her efficiency, by decreasing her power of moving
quickly in any desired direction, which is essential to the utility of
such a vessel in time of war; and thus on electric lights, guard boats,
and torpedo guns must the safety of ships in future wars really depend,
when attacked by torpedo boats.

_The Electric Light._--The phenomenon of the _Voltaic arc_ was first
discovered by Sir Humphry, then Mr., Davy at the beginning of the
present century. The following is an account of the matter as given by
him in his "Elements of Chemical Philosophy":--

"The most powerful combination that exists, in which number of
alternations is combined with extent of surface, is that constructed
by the subscription of a few zealous cultivators and patrons of
science in the laboratory of the Royal Institution. It consists of
200 instruments, connected together in regular order, each composed
of ten double plates arranged in cells of porcelain, and containing
in each plate thirty-two square inches; so that the whole number of
double plates is 2,000, and the whole surface 128,000 square inches.
This battery, when the cells were filled with sixty parts of water,
mixed with one part of nitric acid, and one part of sulphuric acid,
afforded a series of brilliant and impressive effects. When pieces
of charcoal about an inch long and one-sixth of an inch in diameter
were brought near each other (within the thirtieth or fortieth part of
an inch), a bright spark was produced, and more than half the volume
of the charcoal became ignited to whiteness, and by withdrawing the
points from each other, a constant discharge took place through the
heated air, in a space equal at least to four inches; producing a most
brilliant ascending arch of light, broad, and conical in form in the
middle. When any substance was introduced into this arch, it instantly
became ignited. Platina melted as readily in it as wax in the flame
of a common candle; quartz, the sapphire, magnesia, lime, all entered
into fusion; fragments of diamond, and points of charcoal and plumbago,
rapidly disappeared, and seemed to evaporate in it, even when the
connection was made in a receiver exhausted by the air pump; but there
was no evidence of their having previously undergone fusion."

The philosopher also showed that, when the Voltaic or electric arc is
produced in the exhausted receiver of an air pump, the phenomena are
as brilliant in character, and the charcoal points can be more widely
separated, thus proving that the electric light is quite independent of
the oxygen of the air for its support.

Owing to the crude nature of the Voltaic batteries of that day, and
also to the great expense of maintaining a large battery of that
nature, nothing practical resulted from Davy's discovery of the
electric or Voltaic arc. Professor Faraday, the great physicist, by
his discovery of the principle of magneto-electricity, has enabled
the electric light to be brought into practical use. As early as
1833 Pixii applied the principle practically in the construction of
a magneto-electric machine with revolving magnets; he was followed
by Laxton, Clark, Nollet, Holmes, and others, who made machines with
fixed magnets. In 1854 Dr. Werner Siemens, of Berlin, introduced the
"Siemens' Armature," which, from its compact form, permitted a very
high velocity of rotation in an intense magnetic field, giving powerful
alternating currents, which, when required, were commutated into one
direction.

The latest improvement has been that from the magneto-electric to
the dynamo-electric machine. It is due to both Dr. Siemens and Sir
C. Wheatstone. Induced currents are directed through the coils of
the electro-magnets which produce them, increasing their magnetic
intensity, which in its turn strengthens the induced currents, and so
on, accumulating by mutual action until a limit is reached.

_Siemens' Electric Light._--The following is a description of
Messrs. Siemens Brothers' dynamo-electric light apparatus, which,
for use on board ship against boat torpedo attacks, &c., is equal,
if not superior, to any similar apparatus yet produced, and which
is extensively used in the German and other European navies. This
apparatus was one of many others experimented on by Dr. Tyndal and Mr.
Douglas, M.I.C.E., for the Trinity House.

Dr. Tyndal says: "I entirely concur in the recommendation of Mr.
Douglas, that the Siemens machine recently tried at the South Foreland
be adopted for the Lizard. From the first I regarded the performance of
this handy little instrument as wonderful. It is simple in principle,
and so moderate in cost that a reserve of power can always be
maintained without much outlay. By coupling two such machines together,
a great augmentation of the light is moreover obtainable."

_Principle._--When a closed electrical circuit is moved in the
neighbourhood of a magnetic pole, so as to cut the lines of magnetic
force, a current is generated in the circuit, the direction of which
depends upon whether the magnetic pole is N or S; it also depends on
the direction of motion of the circuit, and according to the law of
Lenz, the current generated is always such as to oppose the motion of
the closed circuit.

All magneto-electric and dynamo-electric machines are based on the
principle stated above, and are subject to many modifications.

The name _dynamo_-electric machine is given to it, because the electric
current is not induced by a _permanent magnet_, but is accumulated by
the mutual action of electro-magnets and a revolving wire cylinder or
armature. It is found that, as the dynamic force required to drive the
machine increases, so also does the electric current; it is therefore
called a dynamo-electric machine.

_Description._--In the machine here described, of which Fig.
164 is an elevation, Fig. 173 a part elevation, and Fig. 165 a
longitudinal section, the electric current is produced by the rotation
of an insulated conductor of copper wire or armature coiled in
several lengths, 8, 12, 16, &c., up to 28, and in several layers,
longitudinally, upon a cylinder with a stationary iron core _nn' ss'_,
so that the whole surface of the armature is covered with longitudinal
wires and closed at both ends, as in Fig. 165. This revolving armature
is enclosed to the extent of two-thirds of its cylindrical surface by
curved soft iron bars _NN__{1}, _SS__{1}.

[Illustration: Fig. 164.]

The curved bars are the prolongations of the cores of the
electro-magnets _E E E E_. They are held firmly together by screws to
the sides or bottom of the cast iron frame of the machine, making it
compact and strong.

The coils of the electro-magnet form with the wires of the revolving
armature one continuous electric circuit, and, when the armature is
caused to rotate, an electric current (which at first is very feeble)
is induced by the remanent magnetism in the soft iron bars and directed
through the collecting brushes into the electro-magnet coils, thus
strengthening the magnetism of the iron bars,[V] which again induce a
still more powerful current in the revolving armature.

The electric current thus becomes stronger and stronger, and the
armature therefore revolves in a magnetic field of the highest
intensity, the limit of which is governed by the limit of saturation of
the soft iron.

At each revolution the maximum magnetic effect upon each convolution
of the armature is produced just after it passes through the middle of
both magnetic fields, which are in a vertical plane passing through the
axis of the machine (i. e. _N__{1}_S__{1} in Fig. 173). The minimum
effect is produced when in a plane at right angles to it, i. e.
horizontal.

[Illustration: Fig. 165.]

According to the law of Lenz already referred to, when a circuit starts
from a neutral position on one side of an axis towards the pole of a
magnet, it has a direct current induced in it, and the other part of
the circuit which approaches the opposite pole of the magnet has an
inverse current induced in it; these two induced currents are, however,
in the same direction as regards circuit. A similar current will also
be induced in all the convolutions of wire in succession as they
approach the poles of the magnets.

These currents, almost as soon as they are induced, are collected by
terminal rollers or brushes _B_, usually the latter, placed in contact
with the commutator in the position which gives the strongest current.
The position giving the strongest current gives also the least spark,
so that when there are no sparks at the commutator the best lighting
effect is produced. Fig. 166 shows position of brushes when the
armature revolves in the direction indicated by the arrow.

The circumference of the revolving armature is divided into an
even number of equal parts, each opposite pair being filled with
convolutions of insulated wire wound parallel to the axis of the
armature.

The ends of these wires are brought to a commutator and connected to
the segments either by screws or by soldering.

The brushes collect the electric currents as they are induced, which is
nearly constant and continuous.

The collecting brushes are combs of copper wire placed tangentially to
the cylindrical commutator, and press lightly upon it with an elastic
pressure.

[Illustration: Fig. 166.]

_Power and Light produced._--An increase of the armature speed produces
a corresponding increase in the current produced, but not in the same
proportion. The current increases more rapidly than the speed, and
could be made to reach any intensity but for considerations explained
below. With increase of current there is also increase of heat.

The speed for continuous work must not be taken too high, because the
heat developed at high velocities might destroy the insulation of the
coils of the electro-magnet. The speed given for this machine produces
no such injurious heating effect.

The strength of the current is also influenced by the resistance of the
electric lamp and its leading wires. With an electric lamp in a circuit
of proper resistance the armature should revolve at the rate given in
the following Table. The heating will then reach its maximum, which
is very moderate, in about three hours after which there will be no
further change.

------------------------------------------------------------------
TABLE.
-------+---------------------+---------------------+--------------
Size. |Number of revolutions|Intensity of light in|HP (actual) to
| of armature. | standard candles. | drive.
-------+---------------------+---------------------+--------------
Medium | 800 to 850 | 4,000 to 6,000 | 3-1/2 to 4
-------+---------------------+---------------------+--------------

The intensity of the unassisted light is given in standard candles. The
standard here used is a stearine candle consuming 10 grammes per hour.

_Regulation._--From the fact that a closed circuit rotating in a
magnetic field experiences resistance to its motion which a broken
circuit does not, motive power to any extent is only required when
the circuit is closed. An interruption of the current is therefore
equivalent to removing the load from the motor, which for mechanical
reasons may be injurious to it and for electrical reasons to the dynamo
machine.

The sudden interruption of the circuit of the large machine produces
an electric tension so dangerously high as to strain or destroy the
insulation of the machine. When contact is again made after such
interruption, the increase of speed resulting from the interruption
causes a momentary current of great intensity, accompanied by sparks at
the commutator.

In order that the light may be quite steady the speed should be as
uniform as possible. As too high an increase of speed may result in
temporary extinction of the light, it ought never to be permitted. The
motor should therefore be provided with a good and sensitive governor,
that will keep the speed perfectly uniform however the steam and load
may vary. A large and heavy fly-wheel is also very useful in keeping
the speed nearly uniform during change of load.

Although the circuit, when the machine is in full action, should never
be suddenly interrupted, interruption arising from the extinction
of the light is _not_ dangerous, because it is always preceded by a
decrease in the strength of the current. When it is desired to divert
the current into another circuit it is advisable to stop the machine.
Although in practice with small machines this is rarely done, with
large machines it is necessary.

_Self-acting Shunt._--For great security, especially with the two
machines coupled together, where the electric current is strong and
the light equivalent to about 14,000 candles, it is advisable to insert
in the circuit a self-acting shunt.

[Illustration: Fig. 167.]

This is placed between the lamp and machine and connected to both
leading wires. Its principle is as follows:--

The terminal _M_, Fig. 167, is joined by a short connecting wire to
one terminal of the machine. The terminal _L M_ is connected to the
remaining terminal of the machine and also to one of the lamp terminals.

The terminal _L_ is connected to the other terminal of the lamp.

The shunt contains a small electro-magnet _E_ mounted upon a square
wooden slab or baseboard with its armature a, a contact c, and, below
the slab, a resistance coil _W_, which is equal to the resistance of
the electric arc of the light, about 1 S. _u._[W]

As long as the lamp is burning well, the current circulates in the
coils of the electro-magnet, and the armature _a_ being strongly
attracted, there is no contact at _c_. The resistance coil _W_ is
therefore not in electrical circuit. When the light is extinguished the
current in the coils of the electro-magnet ceases, and the armature is
withdrawn by the spring _f_ making contact at _c_. This offers to the
electric current a path through _W_ of equal resistance to that of the
lamp, and the current is subjected to scarcely any change, so that the
motor has practically no cause to alter its rate.

When the carbon points of the lamp again touch, the electric current
returns to them, breaking contact at _c_, re-establishing the former
conditions.

_Direction of Rotation._--The armature may revolve in either direction.
If it becomes necessary to drive it in the opposite direction to that
for which the machine has been made, it is only necessary to reverse
the brushes, placing their points in the direction of motion, and to
change two of the wire connections, which operations can be effected in
a few minutes. Fig. 166 shows the position of brushes for one direction
of rotation and Fig. 168 that for the other.

[Illustration: Fig. 168.]

_Conducting or Leading Wires._--The leading wires are usually of copper
of high electrical conductivity. They must be insulated from one
another the whole of their length and not placed too close together.
As their resistance affects the intensity of the light very much, the
section must be carefully proportioned to the distance of the lamp from
the machine.

The best practical result is obtained when their resistance together
with that of the lamp is equal to the total internal resistance of the
dynamo machine. Wires of various sizes are therefore required.

Decrease in strength of the current caused by a leading wire of too
high resistance can be overcome by a higher velocity, which is obtained
only by increased motive power, but if the wire is much too small, it
will become heated. The proper remedy is to increase the sectional area
of the leading wire.

Bright sparks should never be allowed to appear at the commutator and
brushes, as sparks result from a rapid burning of the metallic parts.
They can easily be avoided by properly inclining the two arms which
carry the brushes.

The position of the brushes yielding the least spark at the commutator
is that giving the highest intensity of light in the electric arc.

The commutator should, while in motion, be freely oiled, to prevent the
brushes wearing away too rapidly. The sticky oil should from time to
time be removed by washing with paraffine oil or benzoline.

_Wear and Tear._--The chances of stoppage so common to the old forms of
electric light apparatus have in this form been reduced to a minimum,
and now do not exceed those that arise with machines generally. The
Trinity House Report states that the Siemens' machine worked well for
a month without any necessity for stopping. The brushes are the only
parts which wear away, and they are very easily replaced.

In thick weather they should be connected in what is called parallel
circuit (or parallel arc, or for "quantity"), because it has been
found that when they are so arranged the intensity of the electric
light produced exceeds by some twenty per cent. the intensity of the
sum of the two when worked separately. Thus the two machines, giving
respectively a candle power of 4,446 and 6,563 when worked separately
(total 11,009), have given when coupled up in parallel circuit a light
equivalent to 13,179 candles; just as in telegraphy it has been found
that the rate of sending can be increased from 20 to 25 per cent. when
the apparatus is coupled up in parallel arc. For this reason it is
usual to employ two machines of medium size instead of one machine of
large size. The intense light so produced is also much more uniform
than from one large machine.

_Automatic Electric Lamp._--Automatic electric lamps have been
constructed with spring clockwork to cause the carbons to approach one
another to a certain point, when, by means of an electro-magnet, the
clockwork is checked, and the carbon points are allowed to burn away
to such a distance that, by the decrease of current, the clockwork is
released and the carbons caused to approach again. With such lamps the
clockwork has been a source of trouble, and it is liable to get out of
order.

_Siemens' Patent Electric Lamp._--The lamp here described is actuated
without clockwork; it also automatically separates the carbons after
they have approached too closely or touch, and, by this combined action
of approaching and separating, the carbon points are kept at a proper
distance apart, and a steady light is obtained.

The working parts are represented in the diagram Fig. 169, and at Fig.
170 is shown the size employed on board ship.

_E_ is the horse-shoe magnet with the armature _A_ placed in front of
its poles a short distance from them. A regulating screw _b_ with the
spiral spring _f_ is attached to the lever _A'_, forcing it against
the stop _d_, and withdrawing the armature from the poles of the
electro-magnet. When a current traverses the coils of the latter of
sufficient strength to attract the armature and overcome the tension
of the spring _f_, contact is made at _c_, which diverts the current
from those coils. The consequent release of the armature breaks contact
at _c_, the armature is again attracted, and this action is repeated,
producing a vibrating motion of the lever and armature, which continues
as long as there is sufficient current to overcome the tension of the
spring.

[Illustration: Fig. 169.]

The spring pawl _s_ at the upper end of the lever _A'_, and oscillating
with it, actuates a ratchet-wheel _u_, which is in gear with a train
of wheels and the carbon holders; it thus opposes their tendency to
approach by pushing them apart, tooth by tooth, until the current is
so much weakened by the increased length of electric arc that the
armature and lever cease to oscillate enough to move the teeth of the
ratchet-wheel, and it rests near the stop _d_.

While in this position the spring pawl is released from the
ratchet-wheel and the preponderating weight of the upper carbon holder
causes the carbon points to approach again. Increase of current follows
decrease of resistance, the armature again oscillates, and this cycle
of action is continuously repeated.

When in action the movements of the carbons are scarcely perceptible,
but when, by any external cause, the carbons are separated so as to
extinguish the light, they immediately run together until they touch,
when they ignite and separate to a proper working distance by means of
the electro-magnet above described.

The only operation requiring attention in the use of this lamp is the
adjustment of the tension of the spring _f_. When this tension is once
regulated to the current at disposal, the lamp will continue to give a
steady light as long as the current remains uniform.

The relative rate of consumption of the two carbon points differs. The
positive carbon burns away rather more than twice as quickly as the
negative carbon.

[Illustration: Fig. 170.]

The duration of the light depends mainly on the lengths and sizes of
the carbons.

Provision is made in this lamp that the rack which supports the
negative carbon may be made to gear either into the teeth of the same
pinion as that of the positive carbon, or into one of about half the
size. By these means the light, when once focussed in a reflector,
will remain in focus as long as the carbons last, whether permanent or
reversed currents are employed.

Besides its twofold application, the lamp is very compact, is simple in
construction, and therefore not likely to get out of order, and it is
capable of being regulated with great precision.

There is no spring to be wound up. The contact need not be cleaned, as
the sparks are scarcely perceptible.

By removing two screws in the outside casing, all the chief working
parts can be easily removed and inspected.

Carbons are made from the hard carbon deposited in the interior of
gas retorts, also from graphite. Various sizes, both square and round
in section, of from 5 to 20 mm. in diameter, are used in the electric
lamp according to the intensity of the electric current. Those commonly
employed are from 10 to 12 mm. in diameter.

The carbons supplied with the Siemens patent lamp are coated with a
thin film of copper. This enhances the cost somewhat, but it greatly
improves the result, as the carbons burn longer, and do not split, when
so coated.

By coating them the resistance is diminished, except at the points, so
that all the heat is concentrated in the electric arc, and a brighter
light is the result.

When two dynamo machines are coupled together (see page 248), to give a
very powerful current, the sizes up to 20 mm. are required.

The consumption varies a little, but the average is from 3 to 4 inches
per hour.

[Illustration: Fig. 171.]

_Concentration of Light._--Two kinds of concentrating apparatus are
supplied in combination with the automatic lamp, both of which are
capable of giving a powerful parallel beam, which will reach to an
enormous distance, and are well adapted for naval purposes. The one
kind consists of a parabolic reflector of stout metal, its concave
surface being silvered and burnished. The apparatus is mounted with a
ball-and-socket joint upon a wooden stand, as shown in Fig. 171.

The other kind is the Fresnel catadioptric lens or holophote, Fig. 172,
which may be substituted for the reflector, and gives a more powerful
beam than one given by reflection. The lens is surrounded by a metal
case or lantern, in which is placed the electric lamp upon a slide
for focussing. Behind the carbon points a hemispherical reflector is
placed, to catch all the back rays, and reflect them back through the
lamp focus. The entire lantern is capable of revolving on horizontal
rollers, and swings upon pivots. Two handles are placed at the back to
manipulate it.

[Illustration: Fig. 172.]

As the electric arc is much too bright to be looked into with the naked
eye, both concentrating apparatus are supplied with a lens, called a
focus or flame observer, by means of which an image of the burning
carbons is thrown upon small screens at the back, so that the lamp can
be easily adjusted without fatigue to the eye. The focus observer is
shown on the lamp in holophote, Fig. 172.

_Precautions._--Before starting the apparatus, the electric lamp
terminals and those of the dynamo machine must be _connected up_ by
means of the leading wires provided with each set of apparatus. The
terminals are marked _C_ and _Z_ respectively, and they should be
connected, _C_ of machine to _C_ of the lamp, and _Z_ of the machine to
_Z_ of the lamp, in order that the electric current may be sent in the
proper direction through the carbons of the lamp. Should it, however,
be found that the top carbon (which should consume twice as fast as
that of the bottom one) does not consume so fast as the bottom one, it
may be assumed that the dynamo machine has reversed its poles, and the
leading wires will consequently require changing across. This reversal
of poles, though possible, is of _very rare_ occurrence.

[Illustration: Fig. 173.]

The dynamo-electric machine should not be driven without its proper
leading wires to lamp and lamp being connected up, or at least
an external resistance equivalent to that of the lamp (which is
approximately one Siemens' unit) must be inserted. In other words, the
machine must not be driven when a wire of small resistance connects the
two terminals _C_ and _Z_. This is expressed more briefly by saying the
machine must not be _short-circuited_. If it is short-circuited when
in motion the electric current becomes so powerful that it will leap
from segment to segment of the commutator, where very bright and large
sparks will be seen, and if continued would destroy the insulation,
thus weakening the current generated.

The leading wires should never be disconnected suddenly while the
machine is revolving at its full speed, as such a sudden interruption
will produce an intense spark, which will burn the ends of the wire
where the contact is suddenly broken. When it becomes necessary to
disconnect the wires, the belt should be pushed on to the loose pulley
by means of the striking gear, or the steam engine should be stopped.

It may be here stated that all connections should be cleaned bright and
screwed tightly, to ensure perfect metallic contacts being made.

_Coupling two Machines._--At Fig. 174 is shown a diagram of how to make
the connections when coupling two machines in parallel circuit. _MM'_,
_m_, _m'_, represent the ends of the wires of the electro-magnets;
_BB'_ are the branches; _C_ and _Z_ are the terminals of each machine
respectively.

[Illustration: Fig. 174.]

The three ways in which the various wire connections of these machines
are joined up, and which are enough for all ordinary purposes, are
given below in paragraphs (_a_), (_b_), and (_c_).

(_a_) When the machine is working _singly_ and revolving in the
direction indicated in Fig. 166, the following connections are made:--

_M_ is connected with _B_,
_M'_ " _B'_,
_m_ " _Z_,
_m'_ " _C_,

and the leading wires of the lamp are connected with _C_ and with _Z_
as explained.

(_b_) When working _singly_ and revolving in the direction indicated in
Fig. 168:--

_M_ is connected to _B'_,
_M'_ " _B_,
_m_ " _Z_,
_m'_ " _C_.

Thus the only change necessary when the machine is to be driven in the
opposite direction to that for which it is made, is to disconnect at
_B_ the wire from _M_ to _B_ and at _B'_ the wire from _M'_ to _B'_,
and to cross them. The machine will then be connected as above (_b_).

(_c_) When working _two_ machines in parallel circuit, as in Fig. 174,
they must be connected as follows (that on the left of the page being
called the first machine, and that on the right the second machine):--

_C_ of first to _C_ of the second.
_Z_ " _Z_ "
_M_ " _B_ "
_B_ " _M_ "
_M'_ " _B'_ "
_B'_ " _M'_ "

and then connect _C_ and _Z_ of the second machine with the leading
wires of the lamp.

The connections _m_ to _Z_ and _m'_ to _C_ in each machine are the same
as in cases (_a_) and (_b_). They do not require to be altered, and may
therefore be left out of consideration in all three cases (_a_), (_b_),
and (_c_). The whole of the connections here indicated can be quickly
made by means of a cross-bar commutator or switch, which is supplied
with the machines in cases where such changes are likely to be required
frequently. This is usually attached to a wall, leading wires being
taken to it from the dynamo machines separately, and others from the
switch being led to the electric lamps.

The leading wires from machine to lamp should, whenever possible, be
kept _separate_, to prevent them rubbing together and making contact. A
distance of two inches is quite sufficient to prevent accidents of any
kind.

When the leading wires are erected in places where they are likely to
rub and chafe against hard substances, it is advisable to enclose each
wire separately in india-rubber tubing at all the points where they are
likely to be rubbed. This becomes very important on board ship, where
everything is in motion, and special care is in consequence required.

Some dynamo machines are coupled direct to the crank shaft of the steam
engines; they require the same kind of attention as others, that is to
say, they should be driven at a uniform speed, should be well oiled as
well as the steam-engine, and they should be kept clean and free from
sharp grit.

_Application._--The electric light used in the case of a _direct_
attack by torpedo boats, without the assistance of guard boats, will
not prove of much assistance, on account of the very small space
covered by the beam of light, and therefore if the direction of attack
is not exactly known, the beam of light must be kept continually
sweeping round the horizon on the chance of picking out the attacking
boats, and thus, while flashing in one direction, they may be
approaching in another, and effect their deadly mission.

Every man-of-war should be fitted with at least three electric lights,
whereby the above-mentioned want of space covered would be to a
considerable degree obviated.

If a powerful beam of light be thrown in a particular direction, and
there kept stationary, all boats or vessels crossing its path at a
distance not exceeding 1600 yards from the ship using the electric
light, would become distinctly visible to observers placed behind the
light; these vessels remaining visible as long as they continue in such
a position that the beam of light acts as a background to them. Under
very favourable circumstances, the distance at which the above effect
may be observed is much increased.

The parabolic reflector extends only about an arc of 33° at 540 yards'
distance from the light.

One defect of this form of reflector is, that it is rapidly dimmed by
spray, rain, and by the particles given off by the carbons.

The catadioptric lens, or holophote, gives a far more powerful but a
more concentrated beam than the parabolic reflector. By means of such
a beam of light, a torpedo boat may be discerned at about one mile
distance. By adding divergent lens to the holophote, a less powerful
and less concentrated beam of light will be thrown out; in this case
about 20° of surrounding water would be well illuminated at about 900
yards' distance, while without the divergent lens there would be only
about 5° so illuminated but far more brilliantly.

The distance at which objects can be detected by the electric light
depends on their size and _colour_, more particularly on the latter.

The observer should as a rule be well removed from the light.

In the case of an electric light being thrown on the observer, the
vessel, &c., using it would to that observer be invisible, the
light only being seen; also when directed on any particular object,
surrounding objects would be thrown into shade.

The electric light will be found very useful for signal purposes by
fitting a plane mirror in front of the catadioptric lens; so arranged
that it be turned to any desired angle to the axis of the beam of
light. By altering the angle of the mirror, the reflected beam of
light can be swept from the horizon on one side, through the zenith,
to the horizon on the other side. The time of passing the zenith being
equivalent to the long and short flashes of the usual night signal code.

In addition to using the electric light to detect the approach of
torpedo boats, it may be used by the boats themselves to prevent the
attacked vessel from discerning them.

In turret ships, electric lights may be so arranged that the instant an
object is brought into the field of the beam of light, the turret guns
will be bearing on it.

One great disadvantage of electric lights is the impossibility of
protecting them from the enemy's fire, and this is a defect that cannot
be eradicated, though it may be lessened, by manipulating them from the
tops of a ship.

_Torpedo Guns._--Hitherto by torpedo guns has been meant small guns
mounted on carriages so constructed that a shot may be fired into
the water only a few feet from the ship's side, or mitrailleuses,
Gatlings, &c. Here the term is applied only to machine guns, which are
constructed to fire either volleys, or, extremely rapidly, single shot,
each shot of which would be capable of _penetrating_ and _sinking_
torpedo boats, such as Messrs. Yarrow and Thornycroft are daily
launching from their yards. Of such weapons there are at present only
two, viz., the "Nordenfelt" and "Hotchkiss" gun. The former has, after
very exhaustive experiments, been adopted by the English, Austrian,
Swedish, and other naval authorities, while the latter has been adopted
by the French government.

_Nordenfelt Torpedo Gun._--This gun, as it at present is constructed,
consists of four barrels of 1 inch calibre.

The barrels are fixed in a horizontal plane, and are not moved during
the firing; and the movement of the lever, the loading, the firing,
and the extracting are all performed in the same plane, so that the
_elevation_ of the gun is not disturbed by the firing.

The gun is fed by means of hoppers, each of which contains ten rounds
per barrel, _i. e._, forty shots.

The continuous supply of cartridges, as well as the firing and
extracting, are all performed by one motion of the lever, thus enabling
the gunner to use his left hand to lay the gun.

A volley of four shots can be fired at the same moment, or one shot can
be fired separately. Eight shots can be fired in 1-1/4 seconds; twenty,
thirty, or forty shots can be fired at a rapidity of two hundred shots
per minute without difficulty.

The recoil being taken up by the whole framework of the gun does not in
the least disturb the aim.

The entire mechanism of the gun can be opened up without undoing a
single screw, in less than 20 seconds.

All the four spiral firing springs can be taken out, without opening
the rest of the mechanism, in 1-1/2 seconds.

All the parts of the mechanism are made interchangeable, so that
reserved parts can at any time be substituted. The gun can be placed on
half cock, so that the strikers do not act; and for further security
the lever can be locked. The carrier block, without which the gun
cannot be fired, is loose, and can be taken away, in case it becomes
necessary to abandon a gun, which is thus made useless to the enemy.

The bullets are solid steel, weighing about 1/2 lb. At 1760 yards at
right angles this gun will penetrate a 3/16 inch steel plate, which
represents the thickness of the plates of a torpedo boat.

At 200 yards at right angles it will penetrate one 3/16 inch steel
plate placed in front of a 1/2 inch steel plate with a space of 3 feet
between them, this target representing the plates and boiler of a
torpedo boat.

At the same distance, at 30° angle against the line of fire, it will
penetrate a 1/2", 1/4", or 3/16" steel plate.

The holes in some instances are from 6 to 11 inches in length, and
2-1/2 inches in height. Angle of depression 20°, of elevation 30°, and
of direction 360°.

Weight of the gun 3-3/4 cwt., and weight of carriage 2-1/2 cwt.

_Hotchkiss Torpedo Gun._--This gun consists of a group of five barrels,
revolving on a central shaft, a breech block, containing the firing
mechanism, a feeding hopper, and the necessary hand crank for training
and firing. The gun is mounted on trunnions attached to a vertical
column, which rests in a suitable socket bolted to the ship's side; by
this means a universal motion is obtained.

The essential difference between this and the Nordenfelt gun is, that
the _barrels_ and mechanism are put into rotatory motion.

Another point of difference is that single shots only can be fired, and
not a volley, as in the Nordenfelt gun.

With the Hotchkiss gun, only some thirty shots can be fired in one
minute at an advancing torpedo boat. The weight of the Hotchkiss steel
shot is about 1 lb., but owing to the low velocity of the gun, its
penetrative power is little more than that of the Nordenfelt 1/2 lb.
bullet.

The object to be gained in firing at an attacking torpedo boat is to
sink her, and not merely to kill or disable her crew, for supposing the
attack to be made with a contact spar torpedo, and the boat to have
reached within 300 yards' distance from the ship, then, even if all
the crew (probably two or three men) were disabled or killed, the boat
would, if not sunk, still carry out its work of destruction; therefore
the projectiles to be used under such circumstances should be only
those capable of penetrating a torpedo boat's plates, _i. e._, solid
steel shot, not shells.

_Diving._--In laying down and in picking up submarine mines, divers
will be found extremely useful; also in clearing a passage in a
river, &c., of an enemy's torpedoes in time of war. During the late
Turco-Russian war, the harbour of Soukoum Kaleh taken by the Turks was
_popularly_ supposed to have been cleared of its mines by native divers
(Lazees), but as the torpedoes so captured were never seen at Stamboul,
it must have been a stretch of imagination; probably such would have
been done, had there been any mines in the harbour to clear away.

The following is a general description of Messrs. Siebe and Gorman's
improved diving apparatus.

The apparatus consists of

1. An air-pump.
2. The diving dress.
3. The breast-plate.
4. The helmet.
5. The boots.
6. The crinoline.

_Air-pump._--This improved air-pump consists of two double action
cylinders, each cylinder capable of supplying about 135 cubic inches
per revolution. The advantage of this air-pump is, that it can supply
air to two divers, working independently and at different levels,
each diver being in direct connection with one of the cylinders. The
air-pipes are in lengths of 45 feet and 30 feet, made of vulcanised
india-rubber with a galvanised iron wire imbedded; this protects from
corrosion, and allows the air to pass through the pipes with less
friction.

_Diving Dress._--The diving dress is made of solid sheet india-rubber,
covered on both sides with tanned twill; it has a double collar, the
inner one to pull up round the neck, and the outer one of vulcanised
india-rubber to go over the breast-plate and form a water-tight joint.
The cuffs are also of vulcanised india-rubber, and fit tightly round
the wrist, making, when secured by the vulcanised india-rubber rings, a
water-tight joint, at the same time leaving the diver's hand free.

_Breast-plate._--The breast-plate is made of tinned copper, and has a
valve in front, by which the diver can regulate the pressure of air
inside his dress and helmet. The outer edge of the breast-plate is of
brass, and is secured by screws to the outer collar of the dress.

_Helmet._--The helmet is made of tinned copper, and has a segment
bayonet screw at the neck, corresponding to that of the breast-plate,
which enables the helmet to be removed from the breast-plate by
one-eighth of a turn. It has three strong plate glasses in brass
frames, protected by guards; two oval at sides, and a round one on the
front; the front one can be unscrewed, to enable the diver to give
and take orders. At the side is an outlet valve, which, by inserting
a finger, the diver can close, and so rise to the surface. The valve
allows the foul air to escape, and prevents the entrance of the water.
An elbow tube is securely fitted on the helmet, to which is fixed an
inlet valve, to which the air-pipe is attached. The inlet valve is
made that the air can enter, but in case of a break in the air-pipe it
cannot escape.

The front and back weights are of lead, heart-shaped, and weigh about
40 lbs. each.

_Boots._--The boots are made of stout leather, with leaden soles, and
are secured over the instep by a couple of buckles and straps. Each
boot should weigh at least 20 lbs.

_Crinoline._--The crinoline or shackle is used for deep water; it is
placed round the body and tied in the front of the stomach: being
supported by braces, it affords protection to the stomach, and enables
the diver to breathe more freely.

_Ladder._--An iron ladder should be provided with stays to bear against
the side of the boat from which the diving is carried on, to which may
be attached (if working in deep water) an ordinary rope ladder, with
ash rounds, and weighted at the end. Some divers have the ladder only
20 feet long, to the last round a rope with a weight attached, which
rests on the ground; by that means they descend.

_Directions for using the Apparatus._--The ladder having been fixed,
the position of the pump should be decided on, and it should be
securely lashed by means of the ropes attached to the handles down to a
stage, into which the _screw-eyes_ should be fastened if necessary; the
pump should be placed out of the way of the divers, the men attending
on them, and all the men employed. The best position for the pump is
facing the head of the ladder, and about six feet from it.

While the diver is dressing, the pump should be prepared for use,
the winch handles should be taken out of the pump case, the nipples
protecting the crank axles removed, the nuts being replaced on their
screws. The nuts for the ends of the crank axles are taken off, the
fly-wheel placed on the shaft, and the winch handles put on, and
secured by the nuts, which are screwed home with the spanner. The pump
is always worked in its case.

The flaps covering the pressure gauges and that at the back of the
pump case should be opened, the screw on the overflowing nozzle of the
cistern removed, and the cistern filled with water; the caps of the air
delivery pipes should be removed, the necessary lengths of air-pipe
should be put together carefully with washers in place, and all the
screws must be worked home by means of the _two_ double-ended spanners.
The air-pipes should be tested by holding the palm of the hand to the
end of the pipe, till the pressure shown on the pressure gauge is
considerably above that corresponding to the depth the diver is to
descend.

_Dressing the Diver--Crinoline only for Deep Water._--The diver having
taken off his own clothes, puts on a guernsey, a pair of drawers,
very carefully adjusted outside the guernsey, and securely fastened
by the tape round the waist, to prevent them from slipping down, and
then a pair of inside stockings. If the water be cold, the diver may
put on two or more of each of the above articles. He then puts on the
crinoline and woollen cap, drawing the latter well over his ears; some
divers find relief from putting cotton saturated with oil in their ears.

The _shoulder pad_ is then put on, and tied under the diver's arms.
He then gets into the diving-dress, which in cold weather should be
slightly warmed, drawing it well up to his waist; he next puts his arms
into the sleeves, an assistant opening the cuffs by means of the cuff
expanders, or by inserting the first and second fingers of both hands,
taking care to keep his fingers straight. The diver, by pushing, forces
his hand through the cuff. He puts on a pair of outside stockings and a
canvas overall to preserve the dress from injury.

The diver then sits down, and the inner collar of the dress is drawn
well up and tied round the neck with a piece of spun yarn, and the
breast-plate put on, great care being taken that the india-rubber of
the outer collar is not torn in putting it over the projecting screws
of the breast-plate. The four pieces of the breast-plate band, which
with the thumbscrews had been previously placed for safety in one of
the boots, are then put over the outer collar, and secured to the
projecting screws by means of the thumbscrews; the centre screw of each
plate should be tightened first. It will generally be sufficient if the
thumbscrews be screwed up hand-tight, the spanner being only used when
necessary. The canvas overall is now adjusted and the boots are put on.

The rings are passed over the cuffs, and the sleeves of the overall are
drawn down to cover them. If gloves are to be used, the rings will be
put on over them, as well as the cuffs. The helmet (without the front
bull's-eye) is then put on; before doing so, the attendant should blow
through the outlet valve of the helmet; he can do so by placing his
head in the interior, and placing his mouth to the hole where the air
escapes. Blow strongly; if in proper working order, the valve will
vibrate. A loop of the life line is placed round the diver's waist, the
line brought up in front of the man's body, and secured with a piece of
small rope passing round his neck, or to the stud on the helmet. The
waist-belt is buckled on with the knife on the left side, the end of
the air-pipe being passed from the front, through the ring on the belt
on the man's left, and up to the inlet valve on the helmet, to which it
is secured; the upper part of the pipe is then made fast by a lashing
to the stud on the left of the helmet. The diver then steps on the
ladder, and two men are told off to _man the pump_.

The weights are then put on, the front weight first, the clips being
placed over the studs on the breast-plate. The back weights are then
put on, and the clip lashings over the hooks on the helmet, and the two
are secured to the diver's body by means of the lashing from the back
weight, which is passed round the waist, through the thimble beneath
the front weight, and tied to the other end of the lashing at the back
weight.

When the signalman is sure that all is right, and that the diver
understands all the signals, he gives the word _Pump_, and screws the
centre bull's-eye into the helmet securely; this done, he takes hold of
the life line and "pats" the top of the helmet, which is the signal for
the diver to descend.

_Signals employed._--The signalman is the responsible person, and must
be very vigilant all the time the diver is down; occasionally he will
give one pull on the life line, and the diver should return the signal
by one pull signifying "all right;" if the signal be not returned, the
diver must be hauled up, but if the diver wishes to work without being
interrupted by signal, he gives one pull on the line, independently,
for "All right; let me alone." If the signalman feels any irregular
jerks, such as might be occasioned by the diver falling into a hole, he
should signal to know if he is all right, and if he does not receive
any reply, he should haul him up immediately. If the diver from any
cause is unable to ascend the ladder, and wishes to be pulled up, he
gives four sharp pulls on the life line. If while being hauled up the
diver gives one pull, it signifies "All right; don't haul me any more."
The diver should be hauled up slowly and steadily. If the signalman
wishes the diver to come to the surface, he gives four sharp pulls on
the line, on which the diver should answer "All right," return to the
foot of the ladder, and signal to be hauled up.

_One_ pull on the air-pipe signifies that the diver wants more air.
_Two_ pulls on the life line and _two_ pulls on the air-pipe in rapid
succession, signify that the diver is foul and cannot release himself,
and requires the help of another diver; on receiving such a signal, no
attempt should be made to haul the diver to the surface.

The above signals are to be invariably used; but other signals may be
arranged as is most convenient for any particular work, as a great
variety can be made with the life line and air-pipe. The diver can
communicate with the surface by means of a slate.

Further information on this subject, especially with regard to the
foregoing diving apparatus, will be found in Messrs. Siebe and Gorman's
"Manual for Divers."

FOOTNOTES:

[Footnote V: In wrought iron there is always some residual magnetism;
there is therefore no necessity to start the magnetism with a permanent
magnet.]

[Footnote W: Siemens' unit.]

CHAPTER XI.

ELECTRICITY.

_THEORY of Electricity._--The theory most readily understood, and which
most satisfactorily explains the various electrical phenomena, is as
follows:--

"That every substance and every atom of the world is pervaded by a
peculiar, subtle, imponderable fluid which is termed _Electricity_,
but which is not known to exist, or remains in a state of _electrical
equilibrium_, until evoked by certain causes."

The effect of causing a disturbance of this equilibrium is to increase
the normal, or natural, electricity in some particles, and to equally
decrease it in other particles, i.e. what one loses the other gains.
An excess of natural electricity is denoted by the term _positive_,
or mathematical symbol (+) while a deficiency is denoted by the term
_negative_, or symbol (-).

_Like electricities repel each other._

That is to say, two bodies charged with an excess of, or positive,
electricity, being brought together repel each other, neither wishing
to increase the excess that has been evoked in them.

Similarly in the case of two bodies charged with a deficiency of, or
negative, electricity, neither wish to add to the deficiency already
there.

In both these cases there can be no tendency to electrical equilibrium,
which is the principle at work. In the former case, there being already
too much, more will but increase the disturbance.

In the latter case, further deficiency will but add to the irregularity.

_Unlike electricities attract each other._

That is to say, if two bodies, one charged with positive, or having an
excess of electricity, the other charged with negative, or having a
deficiency of electricity, be brought together, they will attract each
other; both being desirous of altering their existing state, the one
by decreasing its excess, and the other by decreasing its deficiency of
electricity.

In this case, there will be a tendency to equilibrium, caused
by attraction. The earth is supposed to be a vast reservoir of
electricity, from which a quantity can be drawn to fill up a
deficiency, and which is always ready to receive an excess from
other bodies. Every body in nature has its own natural quantity
of electricity, and when an object is negatively electrified, or
has a deficiency in its normal quantity, there is a tendency to
receive a supply from any convenient source. Such an object would
receive electricity from the earth if means were afforded; and a
body _positively_ electrified, would tend to part with its excess in
the same manner. Where such facilities for establishing electrical
equilibrium are afforded, the result is the passage of a _current_ of
electricity.

_Conductors._--Sensible effects can be produced by electricity at great
distances from the source, provided there be a medium of communication,
that is, good _conductors_ to transfer it. When a glass rod is rubbed
with a piece of silk, it becomes charged with an excess of, or
positive, electricity, and at the same time the silk becomes charged
with negative electricity.

The glass rod will retain the positive electricity upon it for some
time, unless touched with the wet hand, a wet cloth, a metal, &c., when
it will instantly cease to be electrified. The electricity is then said
to have been conducted away, and the bodies which allow it to run off
the glass are called _conductors_ of electricity. Metals, water, the
human body, charcoal, damp wood, and many other bodies are conductors.

Those bodies which conduct electricity hardly at all, such as the air,
silk, glass, sealing wax, gutta percha, india rubber, &c., are termed
_nonconductors_ or _insulators_.

Strictly speaking, all substances _conduct_ electricity in some degree,
and a _nonconductor_ is merely a _bad_ conductor.

In the following table the bodies are arranged in their order of
conductivity, i.e. each substance conducts better than that which
precedes it; the first-named body is the best insulator, and the
last-named one is the best conductor.

Dry air.
Ebonite.
Paraffin.
Shellac.
India rubber.
Gutta percha.
Resin.
Sulphur.
Sealing wax.
Glass.
Silk.
Wool.
Dry paper.
Porcelain.
Dry wood.
Stone.
Pure water.
Rarefied air.
Sea water.
Saline solutions.
Acids.
Charcoal, or Coke.
Mercury.
Lead.
Tin.
Iron.
Platinum.
Zinc.
Gold.
Copper.
Silver.

Though two substances are near one another in the above list, they do
not necessarily approach one another in their power of conducting. For
instance, taking the conducting power of pure silver as represented by
the number 100, then

Pure Copper will be equal to 99·9,
Gold will be equal to 78·0,
while Zinc will be only equal to 29·0,

and pure water, which is half-way down the list, will offer 6,754
millions more resistance than silver to the passage of the electric
current.

The metals being the best known conductors, are usually employed as the
means of transferring the electric current from one place to another.

_Electric Circuit._--The conditions attending this operation are
different from those of any other known method of transmission.

A complete _circuit_ must always be formed by the electric current,
i.e. it cannot start from one place _A_, travel to another place _B_,
and cease there, but the current must be completed before it can be
said to have reached _B_. There cannot be a current of electricity
without a means of recombination, which recombination must be at the
_source_, or place of original disturbance.

This "place of disturbance" or _source_ must be considered as having
two sides, i.e. at some spot the normal or natural electrical
equilibrium is disturbed, and electricity is separated into too much
(positive) on one side, and too little (negative) on the other side.
If then no means of recombination be afforded, the electricities
remain separated, and no current exists; but if a _conductor_ be made
to connect the two sides, electricity is set in motion, and a current
established. Originally to form a circuit between two stations _A_ and
_B_, a conducting wire and a return wire were necessary, but in 1837
Steinway discovered that the earth itself answered all the purposes of
a return wire, in fact under favourable conditions much better. Thus,
to form a circuit between _A_ and _B_, a conducting wire is required,
and a buried metal plate at _A_ and _B_, the earth by these means
taking the place of the return wire.

The aforesaid metal plates are technically termed _earth plates_.
The greater the size of the earth plates (up to certain limits), the
deeper they are buried, and the better the conducting power of the soil
surrounding them, the better conductors the plates become, or the less
resistance the earth portion of the circuit offers. If either plate
be not in communication with the earth, or else be separated from the
wire, the circuit is not complete, or, as it is termed, "it is broken,"
and no current will flow, the signal not made, torpedo not fired, &c.

_"Short" Circuit._--Due to the fact that recombination, or a tendency
to equilibrium, is always at work when electricity has been evoked, the
conducting path along which the electric current flows must be covered
with a nonconducting substance, or, as it termed, "insulated," or else
the current would not perform its duty, but escape to earth, and so
form what is termed a "short circuit."

A current of electricity always chooses the _easiest path_ to effect
recombination, or electrical equilibrium.

_Insulators, &c._--On land, telegraph wires are as a rule laid above
the ground, and therefore require supporting at every few yards; this
is done by means of posts, and as these are formed of substances which
are conductors of electricity, the wires require to be insulated
from them. The insulators generally employed for such purposes are
cup-shaped pieces of porcelain, or pottery, fixed to the head of
the telegraph posts. By means of these insulators, the current of
electricity is prevented from escaping to the earth by the post
conductors.

A certain amount of leakage, or loss of electricity, must occur at each
of these posts, as there is no such thing as a perfect insulator. When
the wires are laid on the ground or under ground, or under water, they
are insulated by covering them with gutta percha, india rubber, &c.,
and any loss of current is thus prevented.

_Methods of generating Electricity._--For the purposes of torpedo
warfare there are two methods of evoking electricity, viz.--

1.--By _chemical action_.

2.--By _friction_.

_By Chemical Action._--_Chemical action_ is the chief source of free
electricity, the representative of which is the galvanic, or Voltaic,
battery.

The electricity so generated is also termed dynamical electricity, due
to there being a constant electric current, so long as the poles of the
battery producing it are kept closed; the electricity being thus in a
_dynamic_ or moving state.

By chemical action is signified that which occurs when two or more
substances so act upon one another as to produce a third substance
differing altogether from the original ones in its properties, or when
one substance is brought under such conditions that it forms two or
more bodies differing from the original ones in their properties.

_Definition and Properties of a Voltaic Cell._--The _Voltaic_ cell
consists of an insulating jar, containing a liquid, in which are
placed two plates or pieces of dissimilar metals; the liquid must be
composed of two or more chemical elements, one of which at least tends
to combine with one or other of the metals, or _with both in different
degrees_.

By a Voltaic _battery_ is meant a number of cells above one; this term,
however, is often applied to a single cell when working by itself.

A "_simple_ Voltaic cell," "element," or "couple," consists of two
metals placed in a conducting liquid. If two metals--for instance, zinc
and copper--are placed in water slightly acidulated, without touching
each other, no effect is apparent; but if they be made to touch,
bubbles of hydrogen gas are formed over the copper plate, and continue
forming these until the plates are separated. After being in contact
for some time, the copper plate will be found unaltered in weight,
but the zinc plate will have lost weight, and the portion so lost
will be found in the liquid in the form of sulphate of zinc. The same
effects are also produced by connecting the two plates by means of some
conducting substance, instead of placing them in contact.

Zinc is invariably employed as one of the metal plates, on account of
the ease with which it dissolves in dilute acids; and the greatest
results are obtained when the second metal plate is not acted upon
at all by the liquid, for then the whole effect due to the oxidation
of the zinc plate is obtained; but when the second plate is also
chemically acted upon, then only the effect due to the difference
between the two chemical actions is obtained, for, as will be explained
further on, they each act in directly opposite directions.

_Voltaic Current._--The Voltaic current makes its appearance under the
general laws of electrical action.

When a body charged with an _excess_ of, or _positive_, electricity,
is connected with the earth, electricity is transferred _from_ the
charged body to the earth; and similarly when a body is charged with
a _deficiency_ of, or _negative_, electricity, is connected with the
earth, electricity is transferred _from_ the earth to the body.

Generally whenever two conductors in different electrical conditions
are put in contact, electricity will flow from one to the other.
That which determines the direction of the transfer is the relative
_potential_ of the two conductors. Electricity always flows from a body
at _higher potential_ to one at _lower potential_, when the two are in
contact, or connected by a conductor. When no transfer of electricity
takes place under these conditions, the bodies are said to be at the
_same potential_, which may be either _high_ or _low_. The _potential_
of the earth is assumed to be _zero_.

_Definition of Potential._--"The _potential of a body or point, is
the difference between the potential of the body or point, and the
potential of the earth_."

Difference of potential for electricity is analogous to difference
of level for water. Now, since, when a metal is placed in a vessel
containing a liquid, electricity is produced, the liquid becomes of a
different potential to the metal, each being electrified in an opposite
way; and therefore, as above stated, there being a _difference_ of
potentials, electricity will tend to flow from one to the other.

This is evidence of a _force_ being in action, for there can be no
motion without some force to produce it.

_Electro-motive Force._--_Electro-motive force_ is the name given to a
peculiar force to which is due the property of producing a difference
of potentials. When it is said that zinc and water produce a definite
electro-motive force, what is meant is, that by their contact a certain
definite difference of potentials is produced.

The _electro-motive force_ of a Voltaic element may be termed its
_working_ power, in the same way as the pressure of steam is the
working power of a steam engine, though this is not to be considered as
the real source of power, which, as will be seen, is uncertain. Due
to the difference of potential of the metal and the liquid, a current
of electricity will flow from one to the other, causing the chemical
decomposition of the liquid, and the reaction may be taken as the
origin of the power employed.

But while the expenditure of energy (which is necessary to produce a
_force_) is accounted for by taking the chemical action as the source
of power, the preceding cause of this chemical action, viz. the flowing
of the current of electricity due to the difference of potential of the
metal and the liquid, must also have first involved the expenditure of
energy; thus the real source of power is very uncertain.

_Electrolytes._--As before stated, a Voltaic cell consists of two
plates of dissimilar metals, which must be immersed in a liquid
composed of two or more chemical elements, one of which at least will
combine with one or other of the metals, or both in a different degree.
Those liquids which are thus decomposed by the passage of a current of
electricity are termed _electrolytes_.

The elements, then, forming the electrolyte may have chemical affinity
for both metals, though in a greater degree for one than the other.

"Oxygen" is the most important element of an electrolyte, and to the
_affinity for oxygen of the metals_ is the magnitude of the result and
effect.

_Terms Electro-positive and Electro-negative._--All metals have a
definite relation to each other as to the potential which any one may
have when brought into contact with another. Thus, when zinc is brought
into contact with copper, the former has a potential positive to the
latter, i.e. a current of electricity will tend to flow from the zinc
to the copper. The metals may be so placed in a list that each one
would be positive to any of those that follow it; it is then said to be
electro-positive to them, and they are electro-negative to it. As those
metals which are electro-positive to others have a greater affinity for
oxygen, and those that are electro-negative to others a less affinity
for this element, the terms electro-positive and electro-negative
signify, in effect, greater or less affinity for this element.
Conversely, oxygen will combine more readily with the former than with
the latter.

The following list shows the commoner metals arranged in
electro-chemical order.

+ Zinc.
Lead.
Tin.
Iron.
Antimony.
Copper.
Silver.
--Gold.

Take the case of a Voltaic cell composed of zinc and copper plates
immersed in water.

The passage of electricity through the water will decompose it into its
elements hydrogen and oxygen, the latter having an affinity for both
the plates, but considerably more so for the zinc plate.

Then, an electro-motive force will be generated at each metal, and
these forces will act in opposition to each other, but the greater
strength of the one will overcome the weaker, and the real power of the
electric current will be the difference between the two.

_Definition of "Elements."_--The battery plates are termed the positive
and negative _elements_. A Voltaic battery has two _poles_--a positive
and a negative--which are the terminations of the plates.

_Direction of Current._--The course of the current in a Voltaic cell
is as follows:--_Within_ it leaves the electro-positive plate (or
element), and flows to the electro-negative plate, but _outside_ the
cell (or as it were on its return path) it flows from the positive
_pole_ to the negative _pole_. The current always leaves the battery
by the positive _pole_, and thus the copper is the negative _element_,
but the positive _pole_, because the current leaves the battery by it;
and the zinc is the positive element because the current begins there,
_within_ the cell, and the negative _pole_ because it ends there,
_outside_.

The positive pole is the terminal of the negative plate, and _vice
versâ_. There is but one current from a battery, viz. a positive one;
what is called a negative current is merely the positive current
passing in the reverse direction from the same pole, that is, the
positive pole.

_Single and Double Fluid Batteries._--Galvanic batteries may be divided
into single fluid and double fluid batteries. The simplest form of
galvanic cell practically in use is a single fluid cell, consisting of
a zinc and a copper element, immersed in water slightly acidulated by
the addition of a little sulphuric acid. In a battery of several cells,
the zinc and copper plates are generally soldered together in pairs,
and placed in a long stoneware or glass trough, divided into separate
cells by means of partitions. By filling the cells with sand, this
battery is made more portable, the plates being thus supported, and the
liquid prevented from splashing about during transit.

In this form it is called the _common sand battery_.

_Action in a Single Fluid Cell._--The following process goes on in the
single fluid cell when the circuit is closed--that is, when the battery
is set to work.

The water (composed of hydrogen and oxygen) is decomposed by the
passage of the electric current, and oxide of zinc is formed. The
oxygen of the water having greater affinity for the zinc, leaves the
hydrogen. The zinc during the process is being consumed, as coal is
consumed when it burns, while combining with the oxygen of the air.
This oxide of zinc combines with the sulphuric acid, and forms sulphate
of zinc; this salt is found to accumulate in solution in the liquid
of the cell. At the same time the hydrogen of the water goes to the
negative or copper plate, and gathers over it in bubbles.

The process will be better seen by the accompanying plan of the
chemical decomposition and recombinations.

Sulphuric Acid }
Zinc } }Sulphate of zinc found at
{ Oxygen } Oxide of Zinc } positive plate.
Water{ Hydrogen Hydrogen found at negative plate.

No _single fluid_ cell can give a constant electro-motive force because
of the _polarisation_ of the plates.

_Definition of the term Polarisation._--The word _polarisation_ means
that the plates become coated with the products of the decomposition
of the _electrolyte_, producing a diminution of current. In the above
described battery, the hydrogen gathers on the surface of the copper
plate, and an _electro-motive force_ is set up which counteracts
the electro-motive force producing the current--the copper plate is
said to be _polarised_. By the bubbles of hydrogen collecting on the
face of the negative plate, the _surface_ in contact with the liquid
is gradually decreased; thus the plate becomes practically smaller,
and a single fluid cell which at starting gave a good current soon
shows that it is really weakened. The consequence is that the zinc is
consumed extravagantly as well as the acid, and the cell working with
poor results. Also the _resistance_ of the cell is increased, due
to the sulphuric acid, which is added to the water to increase its
conductivity, being gradually used up, by combining with the oxide (see
plan) and forming sulphate of zinc. Liquids are very bad conductors
of electricity; the greater part of the ordinary internal resistance
of a battery arises from this cause. The common sand battery is the
worst of all batteries as regards constancy of electro-motive force,
the _polarisation_ being greater in this battery than any other because
the gas cannot readily escape. The common copper and zinc cell is the
next in order of demerit. The _Smee_ single fluid cell, in which the
negative plate is a platinum instead of a copper one, is better than
the copper zinc cell, because the free hydrogen does not stick to the
rough surface of the platinum plate so much as to the copper.

_Double Fluid Batteries._--All the defects of the single fluid battery,
which are as follows--

1. Diminution of electro-motive force,

2. Inconstancy,

3. Increase of internal resistance,

are remedied in the _double fluid_ battery, of which the _Daniell's
cell_ was the first invented, and is a good example. Of this kind of
cell many forms are in use, but the principle is the same throughout.
There is a positive and negative element, and the cell is divided
into two receptacles for the two fluids. In the most constant form
of Daniell cell, the zinc is plunged into a semi-saturated solution
of sulphate of zinc, the copper in a saturated solution of sulphate
of copper, and these two solutions are separated either by a porous
barrier, or by taking advantage of the different specific gravities of
the two solutions. By a _saturated_ solution is meant a liquid which
has dissolved as much of the substance as it possibly can.

_The Chemical Action of a Daniell Cell._--The chemical action of this
form of Daniell cell is as follows:--

The zinc electrode combines with oxygen; the oxide thus formed
combines with sulphuric acid and forms sulphate of zinc. Oxide of
copper is separate from the sulphate; and the copper in this oxide
is separated from the oxygen. The oxygen of the water is separated
at the zinc electrode from the hydrogen, and at the other electrode
this hydrogen recombines with the oxygen from the oxide of copper.
This alternate decomposition and recombination of the elements of
water can neither increase nor decrease the E.M.F. of the cell, the
actions being equal and opposite. The result of the series of actions
above described is that the sulphuric acid and oxygen of the sulphate
of zinc are transmitted to the zinc, combine with it, and form fresh
sulphate of zinc; the sulphuric acid and oxygen of the sulphate of
copper are transmitted to the zinc set free by the above process, and
reconvert it into sulphate of zinc; the copper of the sulphate of
copper is transmitted to the copper electrode, and remains adhering
to it. The whole result is therefore the substitution of a certain
quantity of sulphate of zinc for an equivalent quantity of sulphate of
copper, together with a deposition of copper on the copper or negative
electrode.[X] The following is a plan of the process:--

Zinc............} } .{ Sulphate of Zinc found
} Oxide of Zinc..} . { at positive plate.
Water { Oxygen..} }.
{ Hydrogen.................}......}
{ Sulphuric Acid.....} } Water.
Sulphate of { { Oxygen..}
Copper { Oxide of Copper { { Copper at negative
{ Copper....{ plate.

_Description of the "Callaud" and "Marié-Davy" Batteries._--The Voltaic
batteries in general use for the different purposes of torpedo warfare
have been fully described in Chapter IV., and therefore it will be
only necessary here to explain the construction of the "Callaud" and
"Marié-Davy" batteries, these being much used abroad in connection with
telegraphy.

The _Callaud_ cell, named from the inventor, is a modification of the
Daniell cell, and is also called a _gravity_ battery, the liquids
being simply prevented from mixing by the law of gravity forbidding
the heavier of the two from rising through the lighter. It consists
of a thin plate of copper, which is laid on the bottom of a good
_insulating_ jar having an _insulated_ wire leading up the side, and
on this plate are placed crystals of sulphate of copper. A solution of
sulphate of zinc is then poured in, and on the top is fitted a zinc
plate, which forms the positive element. The vessel must not be shaken,
or the sulphate of copper when dissolving will mix with the solution
above it.

The _Marié-Davy_ cell consists of a carbon electrode in a paste of
proto-sulphate of mercury and water contained in a porous pot, and a
zinc electrode in dilute sulphuric acid, or in sulphate of zinc.

_The Circuit._--In connection with the manipulation of batteries,
there is one important item to consider, viz. the _resistance_ in the
_circuit_, which may be divided into _external_ and _internal_.

_Resistances._--The _external_ resistance in practice is that which
exists in the conducting line, and the various instruments connected
with it.

The _internal_ resistance is that which exists in the battery itself.
All known conductors oppose a sensible _resistance_ to the passage
of an electric current, and the strength of the current, or in other
words, the quantity of electricity passing per second from one point to
another, when a constant difference of potentials is maintained between
them, depends on the _resistance_ of the wire on the conductor joining
them. A bad conductor does not let the electricity pass so rapidly as a
good conductor, that is, it offers more _resistance_.

Resistance in a wire of constant section and material is _directly_
proportional to the _length_, and _inversely_ proportional to the _area
of the cross section_.

The electrical resistance of a conductor must not be considered as
analogous to mechanical resistance, such as the friction which water
experiences in passing through a pipe, for this frictional resistance
_is not_ constant when different quantities of water are being forced
through the pipe, whereas electrical resistance is constant whatever
quantity of electricity be forced through the conductor.

_Application of Ohm's Law._--_Ohm's law_, which governs the strength of
the current, is expressed by the equation

C = E / R or R = E / C or E = CR.

Where C is the strength of the current;

E is the E.M.F. or difference of potentials;

and R is the resistance of the circuit. */

In words, _Ohm's law_ means that the strength of the current is
_directly_ proportional to the E.M.F., and _inversely_ proportional to
the resistance of the circuit.

As before stated, the resistance of the circuit consists of an
_external_ and an _internal_ resistance, therefore when these
resistances are separately considered, the equation C = E / R must be
converted into C = E / (_x_ + _r_), where _x_ is the external, and _r_
the internal, resistance.

The resistance of the battery or the _internal resistance_ depends on
the size of the plates and the distance between them, that is, it is
_directly_ proportional to the distance, and _inversely_ proportional
to the size.

The _electro-motive_ force of a battery is dependent generally on
the number of cells joined in _series_, and not on the _size_ of the
plates. The cells of a battery may be joined in two ways, as follows:--

1. In series: that is, by connecting the negative
element of one cell to the positive element of another,
and so on.

2. In multiple arc: that is, by connecting negative to
negative, and positive to positive; which is the same
as increasing the size of the cells.

If the conductor between the battery poles be such that the _external_
resistance _x_ may be practically left out, then C = E / _r_, and no
change in the strength of the current will be effected by adding any
number of cells in series, as _r_ will increase equally with _E_, and
therefore _C_ will remain the same; but if under the same conditions
the cells be joined in _multiple arc_, then _r_ will decrease as _E_
increases, and therefore _C_ will be increased.

Thus with a short circuit of small external resistance, the strength of
the current will be increased by increasing the size of the plates, or
by joining the cells in multiple arc, but not in series.

If the conductor between the poles of the battery be such that the
external resistance _x_ becomes very great, then C = E / (_x_ + _r_),
where _x_ is very great compared to _r_. By joining the cells in
multiple arc _r_ is decreased, but _E_ and _x_ remain the same, and
therefore _C_ is not materially altered, as _x_ is very great compared
to _r_. By connecting the cell in series, _r_ is increased, and so is
_E_, but as _r_ is still very small compared to _x_, the strength of
the current _C_ is increased.

Thus with a long circuit of great _external_ resistance, the strength
of the current will be increased by joining the cells in series, but
not in multiple arc.

When the external resistance _x_ is neither very large nor very small
in comparison with the battery or internal resistance _r_, then the
strength of the current _C_ will be increased by adding the cells in
series, and also in multiple arc. By the former process the E.M.F.
_E_ is increased more than the resistance of the circuit _R_ or (_x_
+ _r_), and by the latter process, the E.M.F. _E_ is unaltered, whilst
the circuit resistance (_x_ + _r_) is decreased. All the above may be
practically demonstrated by the employment of suitable _galvanometers_.

_Frictional Electricity._--_Frictional_ electricity is produced by the
friction of two insulators. There is _no difference whatever in kind_
between "Voltaic" and "frictional" electricity.

_Comparison with Voltaic Electricity._--The electricity generated by
friction possesses a great electro-motive force, producing on even
a small conductor a large charge, whereas the electricity generated
by the galvanic cell possesses a very small electro-motive force,
and produces only a small charge on a small conductor. But when the
conductor is large, the electricity produced by the galvanic cell will
almost instantaneously charge the conductor to the maximum potential
it can produce, the galvanic cell developing an immense quantity of
electricity by the chemical reaction; whereas the quantity developed
by friction between two insulators is so small, that if it be diffused
over a large conductor the potential of the conductor will be very
little increased.

The late Professor Faraday has proved that one cell of a Voltaic
pile possesses the same quantity of electricity as an ordinary sized
frictional machine after being wound round 800,000 times, thus
showing the contrast between the qualities of frictional and Voltaic
electricity.

The electricity of the frictional machine and that of the galvanic
battery may be made to produce the same effect, there being no
difference in kind between them. Frictional electricity can be made
to pass in a current, but it is comparatively feeble. Again, Voltaic
electricity can be made to produce a spark, but under ordinary
circumstances it scarcely amounts to anything.

_Description of a Frictional Electric Machine._--A frictional
electrical machine consists of a vulcanite or glass disc or cylinder,
which is made to revolve between cushions or rubbers of leather or
silk. By the friction the (silk) rubbers become negatively, and the
glass disc or cylinder positively, electrified. The revolving disc
immediately after contact with the fixed rubbers passes close by a
series of brass points, which are connected with a _condenser_. These
points collect the positive electricity of the glass, the rubbers
being put to earth. The positive electricity which the glass loses is
supplied through the rubber; a stream of negative electricity flows
from the rubbers to the earth during the charging of the conductor or
condenser; in other words, the positive electricity flows from the
earth to the rubber, whence it crosses to the glass disc and so to the
condenser.

_Definition of a "Condenser."_--A _condenser_ is an arrangement for
accumulating a large quantity of electricity on a comparatively small
surface.

_The "Leyden Jar."_--The _Leyden jar_, which is the original type of
the condenser, or accumulator, consists of a glass jar coated inside
and out, up to within a few inches of the mouth, with tinfoil pasted
on, but having no connection with each other. The mouth is usually
closed by means of a wooden stopper, through which a brass rod passes,
to the head of which is affixed a brass knob, &c., the rod and knob
being metallically connected with the _inner_ coating by means of a
chain.

The "Leyden jar" may be charged either by connecting the _outer_
coating to earth (the rubbers of the machine being also to earth),
and the _inner_ coating to the conductor of the machine; or else by
connecting the outer coating to the rubbers, and the inner coating to
the conductor, a complete circuit being necessary to charge the jar as
highly as the frictional electrical machine will admit of.

The _conductor_ of the machine being charged, also forms a kind of
Leyden jar, the conductor in this case being the inner coating, the
air, the _dielectric_, and the nearest surrounding conductors, such as
the walls of the room, &c., being the outer coating.

_Meaning of "Dielectric."_--By _dielectric_ is meant a non-conducting
medium, which in the case of the "Leyden jar" is the glass.

_Frictional Electricity very little used for Torpedo
Purposes._--Frictional electricity is now seldom used in connection
with torpedo warfare, as on account of its very great power, or
electro-motive force, a very perfectly insulated cable must be
employed, which is somewhat difficult to obtain; it is also necessary
to employ a condenser, which requires a certain time to charge. For
these and other reasons, frictional electricity has been abandoned for
the far more practical Voltaic electricity.

_Magnetism._--A _magnet_ is a piece of steel, which has the peculiar
property, among others, of attracting iron to its ends.

Certain kinds of iron ore, termed the _loadstone_, have the same
properties. The word "_magnet_" is taken from the country Magnesia,
where the loadstone was first discovered.

Magnetism in a body is considered to be a peculiar condition caused by
electrical action. Both electricity and magnetism have the power of
communicating their properties to other bodies without being in contact
with them, i.e. _inducing_ the power, which on the bodies being placed
far apart becomes insensible.

_The "Poles" of a Magnet._--Every magnet has two _poles_, called the
_north_ and _south_ poles. A magnetic steel needle if pivoted on an
upright point, or suspended from its centre, will fix itself, pointing
north and south; in England the end of the needle pointing to the north
is termed the north pole, but in France it is termed the south pole.
The reason of this difference is owing to the fact that the north pole
of one magnet attracts the south pole of another, and therefore, as the
earth is considered as one vast magnet, the end of the magnetic needle
attracted to the north pole of earth magnet should be the south pole of
the magnet; thus the French south pole in a magnet is the English north
pole, and _vice versâ_.

_Permanent Magnets._--A piece of steel when magnetised is termed a
_permanent_ magnet, because it retains its magnetism for a considerable
length of time; but soft iron cannot be permanently magnetised.

A piece of soft iron rendered magnetic by induction retains a portion
of its magnetism for some time after it has been removed from the
magnetic field, by reason of what is called its _coercive force_. This
remnant of magnetisation is called _residual magnetism_.

_Effect of an Electrical Current on a Magnetic Needle._--A magnetic bar
or needle pivoted on its centre will point north and south, but if an
electric current is caused to flow along a wire parallel to and either
over or under the magnetic needle, the latter will be turned from
its position, and remain so as long as the current continues; on the
current ceasing the needle will resume its original position.

The magnetic needle can be turned either to the east or the west,
according to the direction and course of the electrical current.

Thus:--

Current from S. to N. _over_ deflects to W.
Current from N. to S. _under_ deflects to W.
Current from N. to S. _over_ deflects to E.
Current from S. to N. _under_ deflects to E.

The Galvanometer, the "Mirror," and "Thomson's reflector" all depend on
this principle for their usefulness. These instruments have been fully
described in Chapter IV.

_The Electro-Magnet._--If a piece of insulated wire be coiled round a
rod of soft iron, and a current of electricity be made to pass through
the coil, the iron core becomes magnetic as long as the current passes;
when the current ceases the magnetism disappears.

During the passage of the electric current, the iron core possesses all
the properties of a magnet. Therefore if a piece of iron were placed
near its poles it would be attracted and released from attraction as
often as the current passed or ceased; and supposing such a piece
of iron to be retained by a spring, &c., a series of movements,
attraction, and drawing back would be effected.

A piece of iron so arranged is termed an _armature_, and the instrument
is called an _electro-magnet_.

The coil of wire must be carefully insulated, or else the electric
current will pass through the iron core to earth instead of performing
its proper work.

An electro-magnet is much more powerful than a steel magnet of equal
dimensions, and depends on the strength of the current by which the
magnetism is induced, and the number of turns of wire round the core.
The north and south poles of an electro-magnet are determined by the
direction in which the current flows through the wire.

At the _south_ pole the current passes _with_ the hands of a watch, and
at the _north_ pole _against_ the hands of a watch.

_Definition of the "Ohm."_--The "ohm" is the standard used for
electrical resistance; it is obtained by observing what effect is
produced by a current of electricity on a certain conductor in a
certain time.

The ohm is a small coil of German silver wire representing the
resistance overcome by a current in a certain time.

FOOTNOTES:

[Footnote X: Jenkins' 'Electricity.']

APPENDIX.

_McEvoy's Single Main System._--Hitherto in connection with a system
of electrical submarine mines, it has been necessary to employ either
a single cable between each submarine mine and the torpedo station, or
a single cable, termed a "multiple cable," containing a limited number
of insulated wires, leading from the station, and branching off from a
junction box to each mine, by which considerable cost and complication
is incurred. To remedy the above serious defects of such a system, and
also to simplify the arrangement of electrical tests, Captain McEvoy
has devised and patented the following apparatus; at the firing, or
torpedo station, the end of the single main cable, that is, the single
core cable leading to the junction box, is connected to a make and
break contact apparatus, by which, by the movement of a dial or pointer
around a fixed centre, a battery can be successively put in connection
with the wire, and disconnected from it, in a somewhat similar manner
to Wheatstone's step by step dial telegraphs. In the junction box at
the opposite end of the single core main cable is an electro-magnetic
apparatus for working a dial or pointer in exact unison with the
aforesaid dial or pointer at the torpedo station. This junction box
dial or pointer serves as a contact maker to put the wire of the main
cable successively in contact with the branch wires leading to the
several torpedoes, as it is caused to turn with a step by step motion
by the sending of a succession of currents from the firing station.

As the contact maker completes the circuit between the main cable and
one of the branch wires, the current passes from the cable through the
wire, and through the fuze of that particular torpedo to "earth"; but
when any one or other of the torpedoes is to be exploded, the circuit
between the main cable and the torpedo wire being completed, it is
only necessary to send a current through the main cable of sufficient
strength to ignite the fuze, and so explode the mine.

The strength of the current used for giving the aforesaid step by step
motion to the junction box dial or pointer is not sufficient to cause
the ignition of the fuzes in the torpedoes.

Again, if it be desired that the torpedoes should be so arranged that
when any of them are struck by a passing vessel, the fact of its having
been struck should be instantly signalled to the firing station. The
dial apparatus in the junction box is arranged so that at one point of
its revolution, termed the "zero point," all the torpedo branch wires
are in circuit with the main cable, and that then a constant current
is passing from the firing station through all the circuit closers,
and out through resistance coils to "earth." In this case, if one of
the circuit closers be struck, and therefore short circuit formed, the
current passes direct to earth without going through the aforesaid
resistance, and the fact of its having done so is at once indicated by
a galvanometer at the firing point, by the movement of which a bell is
rung at the station. The operator can then explode such torpedo at once
by merely switching in the firing battery.

At the same time the passage of the strong firing current may fuze a
connection in the junction apparatus, by which the exploded torpedo
is detached, i.e. the direct "earth" connection of such a torpedo is
cut off, and the remaining submarine mines are left in proper working
order; this effect may also be arrived at by other means.

_General Description of Apparatus._--The following is a general
description of this exceedingly clever and useful invention:--

At Fig. 168 is shown a diagram view of the apparatus.

_A_ is the instrument at the firing point on the shore or vessel; _B_
is the cable wire led to a submerged box situated near the spot where
the several torpedoes are grouped; _C_ is the instrument enclosed in
the submerged box; _D_, _D_ are insulated wires led away from the box
to the several torpedoes, there being a separate wire for each torpedo.

Each of the wires _D_ is coupled to one or other of a series of
metallic contact pieces _E_ ranged in a circle round the axis of
a metallic pointer _F_, which can be turned with a step by step
motion and successively brought into electrical contact with the
several contact pieces _E_. The axis of the pointer is in electrical
communication with the wire of the cable. The wire from the cable is
first led to the coils of an electro magnet _G_, and thence passes to
the axis of the pointer. _H_ is a magnetic armature in front of the
electro magnet _G_; when a positive current of sufficient strength
is sent through the cable the armature is rocked in one direction,
and when a negative current is sent, it is rocked in the opposite
direction. From the armature motion is transmitted to a pawl which
works into the teeth of a ratchet wheel on the axis of the pointer _F_,
so that by sending a succession of reversed currents of sufficient
strength through the cable, the pointer _F_ is turned with a step by
step motion and is successively brought into electrical contact with
the several contact pieces _E_.

[Illustration: M^{c.}EVOY'S SINGLE MAIN SYSTEM

PLATE LIV.]

In the instrument, at the firing point _a_ is a handle, by the turning
of which a step by step motion is given to the pointer of a dial _b_
and a simultaneous movement to the pointer _F_ of the instrument _C_
in the submerged box. When the handle _a_ has made a half turn it
couples one pole of the battery to the cable and the other to the earth
connection, and when it has made a complete turn the connections are
reversed. The pointer of the dial _b_ then moves forward from
one division of the dial to the next, and simultaneously the pointer
_F_ is turned in unison with it. The operator at the firing point can
therefore always see which of the torpedoes is in electrical connection
with the wire of the cable, and he can test each torpedo in succession
by moving a handle, say at _h_, to cause the current passing back from
the torpedo to pass through a galvanometer at _e_, and by the movement
of the needle of the galvanometer it can be seen whether the resistance
of the circuit through this torpedo is in its normal and proper working
state.

When the pointer of the dial _b_ is brought to zero, or as it is marked
in the drawing to "signal," then the pointer _F_ of the apparatus _C_
is in electrical communication with a contact point which is coupled to
all of the branch wires _D_, and usually the apparatus is left in this
condition, the handle _a_ being then locked and prevented from turning
by a bolt actuated by a handle at _G_.

The current from the battery at the firing point then passes to earth
through the resistances in all of the torpedoes. If now any one or
other of the torpedoes is struck by a passing vessel and the wire from
its fuze put directly to earth, so that the current passes freely to
earth instead of having first to pass through the resistance, the fact
of the current passing freely to earth is notified at the firing point
by the movement of the needle of a galvanometer _d_; the movement of
the needle of this galvanometer effects an electrical connection by
which a small battery is caused to sound a bell at _c_. The operator at
the firing point can then if he pleases at once fire the torpedo that
has been struck by moving a handle at _f_ and coupling up to the wire
of the cable a battery of greater strength; the strong firing current
will pass to earth through the fuze of the torpedo that has been
struck, and will ignite this fuze, but will not affect the fuzes of the
other torpedoes, as to pass through these fuzes it has also to pass
through resistances which impede its passage and reduce its strength,
so that the portion of the current which passes to earth through them
is not of sufficient strength to ignite the fuzes.

When the fuze of any one or other of the torpedoes is exploded by the
passing of a strong firing current through it, the wire leading from
the box _C_ to this torpedo is simultaneously cut off from electrical
connection with the contact pin _E_ to which it was previously
connected, and this pin is put to earth through a resistance either
somewhat greater or less than the resistances in the torpedoes, so that
the firing of one or more of the torpedoes does not interfere with the
power of being able to turn the pointer _F_ of the apparatus _C_ in
unison with the pointer of the dial _b_.

Afterwards the operator at the firing point can ascertain which of the
torpedoes has been fired by passing the pointer of the dial _b_ to
each of the divisions of the dial in succession, and ascertaining by
the galvanometer a the resistance of the circuit through each of the
torpedoes, so that he at once ascertains which torpedo has been put to
earth through the greater or less resistance.

The cutting off of the wire _D_ from its contact _E_ when a strong
current is passed through it may be effected by the wire being coiled
around an iron core forming an electro magnet, which when a strong
current is passed through the wire is of sufficient strength to shift
the position of a contact apparatus and then effect the required
alterations in the connections, but which is not of sufficient strength
to effect any change when the weaker currents used for the signalling
and testing operations are passed through the wire.

It will be evident that with the above described apparatus any one or
other of the torpedoes can if desired be exploded by the operator at
the firing point whenever he desires to do so. To effect this he would
by turning the handle _a_ bring the pointer of the dial _b_ opposite to
the division of this dial; that would indicate that the cable had been
brought into electrical communication with the torpedo required to be
exploded, and then when it is ascertained by previously adjusted sight
points that the vessel is above the torpedo, he can fire the torpedo by
passing a strong firing current to the cable.

In this way the apparatus can be used for firing any one or other of a
group of sunken torpedoes, or if the torpedoes are buoyant ones, they
need not be fitted with apparatus for putting the wire from their fuze
directly to earth whenever the torpedo is struck by a passing vessel.
The same arrangement of apparatus can also be used for firing any one
or other of a number of mines or torpedoes on land and for separately
testing the firing mechanism of each mine whenever desired.

Captain McEvoy's single main system will shortly undergo a series of
experiments under the supervision of the English torpedo authorities at
Chatham, which will most probably result in its adoption by the English
government, and also by the principal continental powers.

TABLE[Y]

SHOWING THE VALUE OF THE FRACTIONS A AND B FOR EVERY HALF DEGREE.

-------+-------------+-------------+
| A | B |
Arc. |150 + [alpha]|150 - [alpha]|
+-------------+-------------+
[alpha]|150 - [alpha]|150 + [alpha]|
-------+-------------+-------------+
145 | 59·00 | 0·017 |
144·5 | 53·54 | 0·019 |
144 | 49·00 | 0·020 |
143·5 | 45·15 | 0·022 |
143 | 41·86 | 0·024 |
142·5 | 39·00 | 0·026 |
142 | 36·50 | 0·028 |
141·5 | 34·29 | 0·029 |
141 | 32·33 | 0·031 |
140·5 | 30·58 | 0·033 |
140 | 29·00 | 0·035 |
139·5 | 27·57 | 0·036 |
139 | 26·27 | 0·038 |
138·5 | 25·09 | 0·040 |
138 | 24·00 | 0·042 |
137·5 | 23·00 | 0·044 |
137 | 22·08 | 0·045 |
136·5 | 21·22 | 0·047 |
136 | 20·43 | 0·049 |
135·5 | 19·69 | 0·051 |
135 | 19·00 | 0·052 |
134·5 | 18·35 | 0·054 |
134 | 17·75 | 0·056 |
133·5 | 17·18 | 0·058 |
133 | 16·65 | 0·060 |
132·5 | 16·14 | 0·062 |
132 | 15·67 | 0·064 |
131·5 | 15·22 | 0·066 |
131 | 14·79 | 0·068 |
130·5 | 14·38 | 0·070 |
130 | 14·00 | 0·071 |
129·5 | 13·63 | 0·073 |
129 | 13·28 | 0·075 |
128·5 | 12·95 | 0·077 |
128 | 12·64 | 0·079 |
127·5 | 12·33 | 0·081 |
127 | 12·04 | 0·083 |
126·5 | 11·76 | 0·085 |
126 | 11·50 | 0·087 |
125·5 | 11·24 | 0·089 |
125 | 11·00 | 0·091 |
124·5 | 10·76 | 0·093 |
124 | 10·54 | 0·095 |
123·5 | 10·32 | 0·097 |
123 | 10·11 | 0·099 |
122·5 | 9·91 | 0·101 |
122 | 9·72 | 0·103 |
121·5 | 9·53 | 0·105 |
121 | 9·35 | 0·107 |
120·5 | 9·17 | 0·109 |
120 | 9·00 | 0·111 |
119·5 | 8·84 | 0·113 |
119 | 8·68 | 0·115 |
118·5 | 8·52 | 0·117 |
118 | 8·37 | 0·119 |
117·5 | 8·23 | 0·121 |
117 | 8·09 | 0·123 |
116·5 | 7·96 | 0·126 |
116 | 7·82 | 0·128 |
115·5 | 7·69 | 0·130 |
115 | 7·57 | 0·132 |
114·5 | 7·45 | 0·134 |
114 | 7·33 | 0·136 |
113·5 | 7·22 | 0·139 |
113 | 7·11 | 0·141 |
112·5 | 7·00 | 0·143 |
112 | 6·89 | 0·145 |
111·5 | 6·79 | 0·147 |
111 | 6·69 | 0·150 |
110·5 | 6·59 | 0·152 |
110 | 6·50 | 0·154 |
109·5 | 6·41 | 0·156 |
109 | 6·32 | 0·158 |
108·5 | 6·23 | 0·160 |
108 | 6·14 | 0·163 |
107·5 | 6·06 | 0·165 |
107 | 5·97 | 0·168 |
106·5 | 5·89 | 0·170 |
106 | 5·82 | 0·172 |
105·5 | 5·74 | 0·174 |
105 | 5·67 | 0·176 |
104 | 5·52 | 0·182 |
103·5 | 5·45 | 0·183 |
103 | 5·38 | 0·186 |
102·5 | 5·31 | 0·188 |
102 | 5·25 | 0·190 |
101·5 | 5·18 | 0·193 |
101 | 5·12 | 0·195 |
100·5 | 5·06 | 0·198 |
100 | 5·00 | 0·200 |
99·5 | 4·94 | 0·202 |
99 | 4·88 | 0·205 |
98·5 | 4·82 | 0·207 |
98 | 4·77 | 0·209 |
97·5 | 4·71 | 0·212 |
97 | 4·66 | 0·215 |
96·5 | 4·61 | 0·217 |
96 | 4·55 | 0·220 |
95·5 | 4·50 | 0·222 |
95 | 4·45 | 0·224 |
94·5 | 4·40 | 0·227 |
94 | 4·36 | 0·230 |
93·5 | 4·31 | 0·232 |
93 | 4·26 | 0·235 |
92·5 | 4·22 | 0·237 |
92 | 4·17 | 0·240 |
91·5 | 4·13 | 0·242 |
91 | 4·08 | 0·245 |
90·5 | 4·04 | 0·247 |
90 | 4·00 | 0·250 |
89·5 | 3·96 | 0·253 |
89 | 3·92 | 0·255 |
88·5 | 3·88 | 0·258 |
88 | 3·84 | 0·260 |
87·5 | 3·80 | 0·263 |
87 | 3·76 | 0·266 |
86·5 | 3·72 | 0·269 |
86 | 3·69 | 0·271 |
85·5 | 3·65 | 0·274 |
85 | 3·62 | 0·276 |
84·5 | 3·58 | 0·279 |
84 | 3·54 | 0·282 |
81·5 | 3·38 | 0·296 |
81 | 3·35 | 0·299 |
80·5 | 3·31 | 0·302 |
80 | 3·28 | 0·304 |
79·5 | 3·25 | 0·307 |
79 | 3·22 | 0·310 |
78·5 | 3·19 | 0·313 |
78 | 3·17 | 0·316 |
77·5 | 3·14 | 0·319 |
77 | 3·11 | 0·322 |
76·5 | 3·08 | 0·325 |
76 | 3·05 | 0·327 |
75·5 | 3·03 | 0·330 |
75 | 3·00 | 0·333 |
74·5 | 2·973 | 0·336 |
74 | 2·947 | 0·339 |
73·5 | 2·921 | 0·342 |
73 | 2·896 | 0·345 |
72·5 | 2·871 | 0·348 |
72 | 2·846 | 0·351 |
71·5 | 2·822 | 0·354 |
71 | 2·797 | 0·357 |
70·5 | 2·773 | 0·360 |
70 | 2·750 | 0·364 |
69·5 | 2·726 | 0·367 |
69 | 2·703 | 0·370 |
68·5 | 2·680 | 0·373 |
68 | 2·658 | 0·376 |
67·5 | 2·636 | 0·379 |
67 | 2·614 | 0·382 |
66·5 | 2·592 | 0·386 |
66 | 2·571 | 0·389 |
65·5 | 2·550 | 0·392 |
65 | 2·529 | 0·395 |
64·5 | 2·509 | 0·398 |
64 | 2·488 | 0·402 |
63·5 | 2·468 | 0·405 |
63 | 2·448 | 0·408 |
62·5 | 2·428 | 0·412 |
62 | 2·409 | 0·415 |
61·5 | 2·389 | 0·418 |
59 | 2·296 | 0·435 |
58·5 | 2·278 | 0·439 |
58 | 2·261 | 0·442 |
57·5 | 2·243 | 0·446 |
57 | 2·226 | 0·449 |
56·5 | 2·208 | 0·453 |
56 | 2·191 | 0·456 |
55·5 | 2·174 | 0·460 |
55 | 2·158 | 0·463 |
54·5 | 2·141 | 0·467 |
54 | 2·125 | 0·471 |
53·5 | 2·109 | 0·474 |
53 | 2·093 | 0·478 |
52·5 | 2·077 | 0·481 |
52 | 2·061 | 0·485 |
51·5 | 2·045 | 0·489 |
51 | 2·030 | 0·492 |
50·5 | 2·015 | 0·496 |
50 | 2·000 | 0·500 |
49·5 | 1·985 | 0·504 |
49 | 1·970 | 0·508 |
48·5 | 1·955 | 0·511 |
48 | 1·941 | 0·515 |
47·5 | 1·926 | 0·519 |
47 | 1·913 | 0·523 |
46·5 | 1·898 | 0·527 |
46 | 1·884 | 0·531 |
45·5 | 1·870 | 0·535 |
45 | 1·857 | 0·538 |
44·5 | 1·843 | 0·542 |
44 | 1·830 | 0·546 |
43·5 | 1·816 | 0·550 |
43 | 1·803 | 0·554 |
42·5 | 1·790 | 0·558 |
42 | 1·777 | 0·562 |
41·5 | 1·765 | 0·567 |
41 | 1·752 | 0·571 |
40·5 | 1·739 | 0·575 |
40 | 1·727 | 0·579 |
39·5 | 1·714 | 0·583 |
39 | 1·702 | 0·587 |
36·5 | 1·643 | 0·609 |
36 | 1·631 | 0·613 |
35·5 | 1·620 | 0·617 |
35 | 1·608 | 0·622 |
34·5 | 1·597 | 0·626 |
34 | 1·586 | 0·630 |
33·5 | 1·575 | 0·635 |
33 | 1·564 | 0·639 |
32·5 | 1·553 | 0·644 |
32 | 1·542 | 0·648 |
31·5 | 1·531 | 0·653 |
31 | 1·521 | 0·657 |
30·5 | 1·510 | 0·662 |
30 | 1·500 | 0·667 |
29·5 | 1·489 | 0·671 |
29 | 1·479 | 0·676 |
28·5 | 1·469 | 0·681 |
28 | 1·459 | 0·685 |
27·5 | 1·449 | 0·690 |
27 | 1·439 | 0·695 |
26·5 | 1·429 | 0·700 |
26 | 1·419 | 0·705 |
25·5 | 1·409 | 0·709 |
25 | 1·400 | 0·714 |
24·5 | 1·390 | 0·719 |
24 | 1·380 | 0·724 |
23·5 | 1·371 | 0·729 |
23 | 1·362 | 0·734 |
22·5 | 1·352 | 0·739 |
22 | 1·343 | 0·744 |
21·5 | 1·334 | 0·749 |
21 | 1·325 | 0·754 |
20·5 | 1·316 | 0·760 |
20 | 1·307 | 0·765 |
19·5 | 1·298 | 0·770 |
19 | 1·290 | 0·775 |
18·5 | 1·281 | 0·780 |
18 | 1·272 | 0·786 |
17·5 | 1·264 | 0·791 |
17 | 1·255 | 0·796 |
16·5 | 1·247 | 0·802 |
16 | 1·238 | 0·807 |
15·5 | 1·230 | 0·813 |
15 | 1·222 | 0·818 |
14·5 | 1·214 | 0·823 |
14 | 1·206 | 0·829 |
13·5 | 1·198 | 0·835 |
13 | 1·189 | 0·841 |
12·5 | 1·181 | 0·847 |
12 | 1·173 | 0·852 |
11·5 | 1·166 | 0·858 |
11 | 1·158 | 0·863 |
10·5 | 1·150 | 0·869 |
10 | 1·143 | 0·875 |
9·5 | 1·135 | 0·881 |
9 | 1·127 | 0·887 |
8·5 | 1·120 | 0·893 |
8 | 1·112 | 0·899 |
7·5 | 1·105 | 0·905 |
7 | 1·097 | 0·911 |
6·5 | 1·090 | 0·917 |
6 | 1·083 | 0·923 |
5·5 | 1·076 | 0·929 |
5 | 1·068 | 0·935 |
4·5 | 1·061 | 0·942 |
4 | 1·054 | 0·948 |
3·5 | 1·047 | 0·954 |
3 | 1·040 | 0·960 |
2·5 | 1·033 | 0·967 |
2 | 1·027 | 0·974 |
1·5 | 1·020 | 0·980 |
1 | 1·013 | 0·987 |
0·5 | 1·006 | 0·993 |
-------+-------------+-------------+

A SYNOPSIS OF THE PRINCIPAL EVENTS THAT HAVE OCCURRED IN CONNECTION
WITH THE HISTORY OF THE TORPEDO.

FOOTNOTES:

[Footnote Y: See page 92.]

ERRATA.

On Page 7 (line 11) insert words "could be destroyed" after "anchor."

On Page 284, (Middle of page) "Fig. 176" should be "Fig. 168."

On Page 285 (4th line from bottom) "e" should be "d."

INDEX.

Abel, experiments by Professor, 207
Abel's detonation experiments, 216
---- high tension fuzes, 37
---- mechanical primer, 23
Action, chemical, 269
---- ----, in a Daniell cell, 274
---- ---- single fluid cell, 273
Adjustments of Whitehead's fish torpedo, the, 136
Admiral Porter's torpedo ship _Alarm_, 159
---- ----, the armament of, 160
Adoption of the fish torpedo, the invention and, 131
Advantages of electrical submarine mines, the, 28
---- ---- mechanical mines, the, 17
Agents, torpedo explosive, 217
Air pump, the, 260
_Alarm_, Admiral Porter's torpedo ship, 159
_Albemarle_, destruction of the, 191
Aluta, the Russian torpedo boat attack off the, 200
American Civil War, the, 189
---- ----, mechanical mines in the, 16
---- ----, torpedoes during the, 115
---- ----, submarine mines during the, 27
---- extempore drifting torpedoes, 119
Apparatus, directions for using the diving, 261
----, firing keys and shutter, 80
----, Siemens' electric light, 241
---- ----, conducting wires for, 247
---- ----, rotation of armatures in, 246
---- ----, wear and tear of, 247
----, the shutter, 82
---- used with a circuit breaker, shutter, 83
Application of Ohm's law, the, 276
---- ---- the electric light, the, 256
Arcs, firing by intersectional, 71
_Argus_, Fulton's attempt against the, 6
Armatures in Siemens' electric light apparatus, rotation of, 246
Armoured cables, single cored, 43
Armstrong's system of electrical testing, 107
Arrangement of earth plates, Brown's, 100
---- ---- wires in McEvoy's spar torpedo, 155
Arrangements, Steward's safety cock, 25
Astatic galvanometer, the, 87
Attack with Harvey's torpedoes, methods of, 127
Attacks, boat torpedo, 191
---- ----, methods of protecting ships against, 180
Austrian method of mooring, the, 56
---- ---- testing, the, 109
---- self-acting circuit closers, 64
---- testing table, the, 108
---- torpedo experiments, 220
---- ---- launches, Thornycroft's, 165
---- war, torpedo operations during the, 192
Austro-Italian war, torpedo operations during the, 188
Automatic arrangements, 10
---- electric lamps, 248

B.
Balance, Wheatstone's, 97
---- ----, manipulation of, 99
---- ----, measurement of resistances by, 98
Barrel torpedoes, 19
Batoum, Russian torpedo boat attack at, 195, 202
Batteries, bichromate, 77
----, double fluid, 274
----, firing, 75
Batteries, Leclanché's Voltaic, 77
----, Menotti test, 79
----, signalling, 78
---- ----, Daniell's, 78
----, single and double fluid, 272
----, telegraph, 79
----, Voltaic, 79
----, Von Ebner's, 76
Battery test for electro-motive force, Voltaic, 105
---- ---- internal resistance, Voltaic, 104
---- ---- potential, Voltaic, 104
Beardslee's high tension fuze, 36
---- joint, 46
Bearings, firing by cross, 70
Bichromate batteries, 77
Boat, Bushnell's submarine, 2, 184
----, Confederate submarine, 185
----, experiment at Cherbourg, torpedo, 170
----, French submarine, a, 185
----, Lay torpedo, the, 141
---- ----, capabilities of the, 147
---- ----, clearing obstructions with the, 151
---- ----, improved form of the, 153
---- ----, launching the, 147
---- ----, method of sinking and raising the, 149
---- ----, used as a tug, 150
---- ---- to clear away mines, 152
----, _Lightning_, Thornycroft's torpedo, 168
----, torpedo, attack at Batoum, 195, 202
---- ---- Rustchuk, 200
---- ---- Soukoum Kaleh, 201
---- ---- Soulina, 198
---- ---- off Matchin, 196
---- ---- the Aluta, 200
---- ----, the final, 203
---- ----, attacks, 180, 191
---- ----, methods of protecting ships against, 180
---- ----, protective, Fosberry's patent, 182
Boats, submarine, 183
---- ----, qualifications essential to, 184
----, torpedo, 162
---- ----, English, 173
---- ----, Herreshoff's, 178
---- ----, ordinary type of, 179
---- ----, Schibau's Russian, 178
---- ----, Spanish, 175
---- ----, Thornycroft's, 163
---- ----, Yarrow's, 172
Booms, construction of, 110
----, defence of harbours by, 110
Boots for divers, 261
Boxes, junction, 51
---- ----, for multiple cables, 52
---- ---- single cored cables, 52
----, resistance, 97
Brakes for Harvey's torpedoes, 123
Breaker, the circuit, 62
Breast-plate for divers, 260
Brook's torpedoes, 19
Brown's arrangement of earth plates, 100
Buoys for Harvey's torpedoes, 122
Bushnell, the inventor of torpedoes, 2
Bushnell's drifting torpedoes, 2
---- mode of ignition, 2
---- submarine boat, 2, 184

C.
Cable, Colt's electric, 7
---- cutters, Fulton's, 5
Cables, circuit closer, 42
----, creeping for electric, 112
----, defects observed in the conductivity of, 103
----, Hooper's, 41
----, insulated electric, 38
----, insulation test for electric, 102
----, jointing electric, 44
----, junction boxes for multiple, 52
---- ---- single cored, 52
----, land service, 43
----, multiple, 42
----, sea service, 43
----, Siemens' electric, 40
----, Silvertown electric, 41
----, single cored armoured, 42
---- ---- unarmoured, 43
----, special, 43
----, test of electrical resistance of, 104
_Cairo_, the loss of the, 189
Calland and Marié-Davy batteries, description of the, 275
Capabilities of Lay's torpedo boat, 147
---- ---- Whitehead's fish torpedo, 134
Carlscrona, experiments with countermines at, 237
----, torpedo experiments at, 220, 224, 232
Case, conical-shaped torpedo, 32
----, cylindrical-shaped torpedo, 32
----, form and construction of torpedo, 31
----, spherical-shaped torpedo, 32
Cell, action in a single fluid, 273
----, chemical action of a Daniell, 274
----, definition and properties of a Voltaic, 269
----, description of a Menotti, 78
----, tests for insulation, sea, 106
---- ----, sea, 100
Charges, size of torpedo, 218
Chatham, torpedo experiments at, 220
Chemical action, 269
---- fuzes, 23
---- ----, defects of, 24
Cherbourg, torpedo boat experiment at, 170
Circuit breakers, 62
---- closer cables, 43
---- closers, Austrian self-acting, 64
---- ----, electro-contact mine, 63
---- ----, Mathieson's inertia, 61
---- ----, improvements in, 63
---- ---- spiral spring, 63
---- ----, McEvoy's mercury, 65
---- ---- weight magneto, 66
---- ----, the use of, 60
----, closing the electric, 60
---- resistances, 276
----, short, 268
----, the electric, 267
Civil war, torpedo operations during the American, 189
----, torpedoes in the American, 115
Clearing a passage through torpedo defences, 111
Coil galvanometer, the three, 88
Colt, experiments by Colonel, 7
Colt's electric cable, 7
---- reflector, 7
_Commodore Jones_, the loss of the, 189
Commutators or switch plates, 96
Comparing electro-motive forces, 94
Composition, Rain's detonating, 23
Compounds, explosive, 208
Concentration of the electric light, 251
Condenser, definition of a, 279
Conductivity of cables, defects observed in the, 103
----, test of platinum wire fuze for, 101
Conductors, 266
Confederate submarine boat, 185
Connections of switch plates, 100
Construction of booms, 110
---- ---- torpedo case, 31
Copenhagen, torpedo experiments at, 223
Countermining, 112
Countermines, experiments with, 235
---- ---- at Carlscrona, 237
---- ---- Stokes Bay, 236
---- ---- in the Medway, 236
Coupling dynamo-electric machines, methods of, 254
Creeping for electric cables, 112
Crimean war, submarine mines during the, 27
---- ----, torpedo operations during the, 187
Crinoline for divers, 261
Cross bearings, firing by, 70
Current, direction of, 272
----, measuring the intensity of a, 95
----, the Voltaic, 270

D.
Daniell's signalling battery, 78
Defects observed in the conductivity of cables, 103
---- of chemical fuses, 24
---- electrical submarine mines, 29
Defence of harbours by booms, 110
----, ship, 10
Defences, clearing a passage through torpedo, 111
Defensive purposes, Harvey's torpedo for, 129
---- torpedo operations, Russian, 193
---- ----, Turkish, 193
---- ---- warfare, 13
Definition and properties of a Voltaic cell, 269
---- of a condenser, 279
---- potential, 270
---- the ohm, 281
---- ---- term explosion, 204
---- ---- explosive force, 204
---- ---- polarization, 273
Description of a frictional electric machine, 278
---- ---- series of firing keys, 81
---- ---- Yarrow's torpedo boat, 172
---- ---- Calland's and Marié-Davy's batteries, 275
---- ---- Siemens' electric light apparatus, 241
---- ---- Whitehead's fish torpedo, 133
_Destroyer_, Ericsson's torpedo vessel, 160
Destruction of passive obstructions, the, 113
---- ---- the _Albemarle_, 191
---- ---- _Duba Saife_, 197
---- ---- _Suna_, 194
Detector galvanometer, the, 88
Detonating composition, Rain's, 23
Detonation, 206
---- experiments, Abel's, 216
----, theory of, 206
Dielectric, gutta percha as a, 38
----, meaning of, 279
Differential galvanometer, the, 88
Direction of current, 272
Directions for using the diving apparatus, 261
Discharge test, the, 103
Disconnector, the, 53
Diver, dressing the, 262
Divers, boots for, 261
----, breast plate for, 260
----, crinoline for, 261
----, helmet for, 260
----, ladder for, 260
Diving, 259
---- dress, the, 260
----, signals employed in, 263
_Dorothea_, Fulton's destruction of the, 4
Double fluid batteries, 274
---- ----, single and, 272
Drifting torpedoes, 116
---- ----, American extempore, 119
---- ----, Bushnell's, 2
---- ----, Fulton's, 5
---- ----, Lewis's, 117
---- ----, McEvoy's, 118
Dualin, 216
_Duba Saife_, destruction of the, 197
Duplex spar torpedo, McEvoy's, 154
---- ----, arrangement of wires in, 155
Dutch torpedo launches, Thornycroft's, 168
---- ----, Yarrow's, 172
Dynamite, 211
Dynamo-electric machines, methods of coupling, 254
---- machine, Siemens' low tension, 75

E.
Earth plates, Browne's arrangement of, 100
Effect compared, explosive force and, 204
Efficiency of Thornycroft's boat engines, 171
Electric cables, creeping for, 112
---- ----, Hooper's, 41
---- ----, insulated, 38
---- ----, insulation test for, 102
---- ----, jointing, 44
---- ----, Siemens', 40
---- ----, Silvertown, 41
---- circuit, closing the, 60
Electric circuit, the, 267
---- fuses, 33
---- lamps, automatic, 248
---- ----, Siemens' patent, 248
---- light apparatus, Siemens', 241
---- ----, conducting wires for, 247
---- ----, light produced by, 244
---- ----, rotation of armatures in, 246
---- ----, wear and tear of, 247
---- ----, application of the, 256
---- ----, concentration of the, 251
---- ----, precautions in manipulating, 252
---- ----, self-acting shunt for Siemens', 245
---- ----, the, 239
---- machine, description of a frictional, 278
---- machines, methods of coupling dynamo, 254
Electrical resistance of cables, test of the, 104
---- resistances, measuring, 93
---- submarine mines, 10, 27
---- ----, advantages of, 28
---- ----, defects of, 22
---- ----, mooring, 54
---- ----, rules for using, 29
---- test of insulated joints, 104
---- testing, Armstrong's system of, 107
---- tests, 85
Electricity, frictional, 278
----, methods of generating, 269
----, theory of, 265
Electro-contact mines, circuit closers for, 63
Electrolytes, 271
Electro-positive and electro-negative, the terms, 271
Electro-magnet, the, 281
Electro-mechanical mines, Russian, 68
Electrometers, 86
----, Thomson's quadrant, 86
Electro-motive force, 270
---- ----, Voltaic battery test for, 105
---- forces, comparing, 94
Employment of torpedo ships, the, 158
Engines, efficiency of Thornycroft's boat, 171
England, torpedo experiments in, 222
English service platinum wire fuse, the, 33
---- torpedo boats, Yarrow's, 173
Ericsson's torpedo vessel _Destroyer_, 160
Experiment at Cherbourg, torpedo boat, 170
---- with a torpedo boat, flotation, 171
Experiments, Abel's detonation, 216
---- by Professor Abel, 207
---- ---- Roux and Sarrau, 207
----, Colt's torpedo, 7
----, Fulton's practical, 5
----, torpedo, at Carlscrona, 220, 224, 232
---- ---- Chatham, 220
---- ---- Copenhagen, 223
---- ---- Kiel, 222
---- ---- Pola, 231
---- ---- Portsmouth, 229, 233
---- ----, Fulton's French, 3
---- ----, in Austria, 220
---- ---- England, 222
---- ---- Turkey, 232
---- with countermines, 235
---- ---- at Carlscrona, 237
---- ---- Stokes Bay, 236
---- ---- in the Medway, 236
Explosion, definition of the term, 204
Explosive agents, torpedo, 217
---- compounds, 208
---- force and effect compared, 204
---- ----, definition of the term, 204
---- mixtures, 208
---- substance, physical state of the, 204
Explosions, illustrated torpedo, 218
Extempore drifting torpedoes, American, 119
---- high tension fuzes, 37
---- ----, Fisher's, 37
---- mechanical mine, 21

F.
Failure of offensive torpedoes, the, 8
Fastest vessel in the world, the, 177
Final Russian torpedo boat attack, the, 203
Firing batteries, 75
---- by cross bearings, 70
---- ---- intersectional arcs, 71
---- ---- observation, 69
---- ---- preconcerted signal, 71
---- Harvey's torpedoes, mode of, 121
---- keys, 80
---- ----, description of a series of, 81
---- ----, Morse, 81
----, mode of, 205
---- ----, in 1829, 6
---- Whitehead torpedoes, Thornycroft's method of, 140
Fish torpedo, adjustments of Whitehead's, 136
---- ----, description of the, 133
---- ----, invention and adoption of the, 131
---- ----, methods of projecting the, 138
---- ----, the mode of ignition of the, 135
Fish torpedoes in war, employment of, 133
---- ----, Thornycroft's method of firing, 140
---- ----, Woolwich, 140
Fisher's extempore high tension fuze, 37
Floating torpedoes, 116
Flotation experiment with a torpedo boat, 171
Fluid batteries, double, 274
---- ----, single and double, 272
Fluid cell, action in a single, 273
Force compared, explosive effect and, 204
----, definition of the term explosive, 204
----, electro-motive, 270
----, Voltaic battery test for electro-motive, 105
Forces, comparing electro-motive, 94
Fore and aft mooring, 56
Form of Lay's torpedo boat, an improved, 153
---- ---- torpedo case, 31
Fosberry's patent torpedo boat protective, 182
Frame torpedoes, 18
Frames, projecting, 111
Franco-German war, torpedo operations during the, 192
---- ----, torpedoes in the, 13
French submarine boat _Plongeur_, 185
---- torpedo launches, Thornycroft's, 165, 169
---- towing torpedoes, 131
Frictional electric machine, description of a, 278
---- electricity, 278
Fulminate of mercury, 215
Fulton, Robert, 2
Fulton's attempt against the _Argus_, 6
---- block ship, 5
---- cable cutters, 5
---- destruction of the _Dorothea_, 4
---- drifting torpedoes, 5
---- failures, 2
---- French torpedo experiments, 3
---- harpoon torpedoes, 5
---- practical experiments, 5
---- return to America, 4
---- spar torpedoes, 5
---- stationary submarine mines, 5
Fuzes, Abel's, 37
----, Beardslee's, 35
----, chemical, 23
----, defects of chemical, 24
----, electric, 33
----, extempore, 37
----, extempore, Fisher's, 37
---- for conductivity, test of platinum wire, 101
----, high tension, 34
----, improved form of Jacobi's, 24
----, McEvoy's percussion, 24
----, percussion, 23
----, platinum wire, 33
----, ----, English service, 33
----, ----, McEvoy's, 34
----, sensitive, 23
----, Statham's, 35
----, test of resistance of platinum wire, 101
----, testing high tension, 102
----, Von Ebner's, 36

G.
Galvanometer, astatic, 87
----, detector, 88
----, differential, 88
----, tables, Siemens' universal, 287
----, thermo, 89
----, Thomson's reflecting, 87
----, three coil, 88
----, universal, Siemens', 89
Generating electricity, methods of, 269
German torpedo vessel _Uhlan_, the, 158
Gun, the Nordenfelt torpedo, 257
----, Hotchkiss torpedo, 259
Gun-cotton, 212
Gunpowder, 208
Guns, torpedo, 257
Gutta-percha as a dielectric, 38

H.
Harbours by booms, defence of, 110
Harpoon torpedoes, Fulton's, 5
Harvey's towing torpedo, 119
---- ----, brakes for, 123
---- ----, buoys for, 122
---- ----, for defensive purposes, 129
---- ----, launching, 123
---- ----, methods of attack with, 127
---- ----, mode of firing, 121
---- ----, tactics with, 127
---- ----, the value of, 129
Helmet for divers, 260
Herreshoff's torpedo boats, 178
High tension fuzes, 102
Hooper's electric cables, 41
---- material, 39
Horsley's powder, 216
Hotchkiss torpedo gun, the, 259

I.
Ignition, Bushnell's mode of, 2
---- of Whitehead's fish torpedo, mode of, 135
Illustrated torpedo explosions, 218
Improved form of Lay's torpedo, an, 153
India rubber tube joint, the, 45
Inertia circuit closer, Mathieson's, 61
---- ----, improvements in, 63
Instrument and observing telescope, shutter, 84
Instruments used in testing, 85
Insulated electric cables, 38
---- joints, electrical test of, 104
Insulation, sea cell tests for, 106
---- test for electric cables, 102
Insulators, 268
Intensity of a current, measuring the, 95
Internal resistance, Voltaic battery test for, 104
Intersectional arcs, firing by, 71
Invention and adoption of the fish torpedo, the, 131
Italian torpedo launches, Thornycroft's, 168

J.
Jacobi's fuze, improved form of, 24
Jar, the Leyden, 279
Jointing electric cables, 44
Joints, Beardslee's, 46
----, electrical test of insulated, 104
----, india rubber tube, 45
----, Mathieson's, 45
----, McEvoy's, 46
----, Nicholl's metallic, 45
----, rules to be observed in forming, 51
----, Siemens' permanent, 47
_Jones_, the loss of the _Commodore_, 189
Junction boxes, 51
---- ---- for multiple cables, 52
---- ---- single cored cables, 52
---- ----, T, 53

K.
Keys, firing, 80
---- ----, description of a series of, 81
---- ----, Morse, 81
Kiel, torpedo experiments at, 222
Knowledge, theoretical, 8

L.
Ladder for divers, 261
---- mooring, 55
Lamps, automatic electric, 248
----, Siemens' patent electric, 248
Land service cables, 43
Launch, description of a Yarrow torpedo, 172
---- for placing moorings, steam, 58
Launches, Thornycroft's torpedo, 163
---- ---- Austrian and French torpedo, 165
---- ---- Dutch and Italian torpedo, 168
---- ---- French torpedo, 169
---- ---- Norwegian torpedo, 163
---- ---- Swedish and Danish torpedo, 165
----, Yarrow's Dutch torpedo, 173
---- ---- Russian torpedo, 172
Launching Harvey's torpedo, mode of, 123
---- Lay's torpedo boat, 147
Law, the application of Ohm's, 276
Lay's torpedo boat, 141
---- ----, an improved form of, 153
---- ----, capabilities of, 147
---- ----, launching, 147
---- ----, method of sinking and raising, 149
---- ----, used as a tug, 150
---- ----, in clearing obstructions, 151
---- ----, to clear away mines, 152
Leclanché's Voltaic battery, 77
Lewis's drifting torpedo, 117
Leyden jar, the, 279
Light, Siemens' electric, 241
---- ----, conducting wires for, 247
---- ----, concentration of, 251
---- ----, precautions in manipulating, 252
---- ----, rotation of armatures in, 246
---- ----, wear and tear of, 247
----, the electric, 239
---- ----, application of, 256
_Lightning_, Thornycroft's torpedo boat, 168
Lithofracteur, 216
Locomotive torpedoes, 131
Loss of the _Cairo_, 189
---- ---- _Commodore Jones_, 189

M.
Machine, description of a frictional electric, 278
----, Siemens' low tension dynamo-electric, 75
Machines, methods of coupling dynamo-electric, 254
Magnet, the electro, 281
Magnetism, 279
Magneto circuit closer, McEvoy's weight, 66
Magnets, permanent, 280
Main system, McEvoy's single, 283
Manipulation of Wheatstone's balance, the, 98
Marié-Davy battery, description of the, 275
Matchin, Russian torpedo boat attack at, 196
Material, Hooper's insulating, 39
Mathieson's cement safety plug, 21
---- circuit closer, inertia, 61
---- ----, improvements in, 63
---- ----, spiral spring, 63
---- joint, 45
McEvoy's drifting torpedo, 118
---- duplex spar torpedo, 154
---- improved Singer's mine, 20
---- joint, 46
---- mechanical mine, 22
---- ---- primer, 21
---- ---- Turk's head, 53
---- mercury circuit-closer, 65
---- papier maché safety plug, 22
---- percussion fuzes, 24
---- platinum wire fuzes, 34
---- single main system, 283
---- weight magneto circuit-closer, 66
Measurement of resistance by Wheatstone's balance, 98
Measuring electrical resistances, 93
---- the intensity of a current, 95
Mechanical mines, 10, 16
---- ----, advantages of, 17
---- ----, best kinds of, 17
---- ----, extempore, 21
---- ----, for coast defence, 16
---- ----, in the American war, 16
---- ----, McEvoy's, 22
---- ---- improved Singer's, 20
---- ----, mooring, 26
---- ----, Russian electro, 68
---- ----, Singer's, 19
Mechanical primer, Abel's, 23
---- ----, McEvoy's, 21
---- tests, 85
Medway, experiments with countermines in the, 236
Menotti cell, description of the, 78
---- test batteries, 79
Menzing's towing torpedo, 130
Mercury circuit-closer, McEvoy's, 65
----, fulminate of, 215
Metallic joint, Nicholl's, 45
Method of carrying fish torpedoes, Thornycroft's, 140
---- ---- sinking and raising Lay's torpedo, 149
---- ---- testing, the Austrian, 109
Methods of attack with Harvey's torpedoes, 121
---- ---- coupling dynamo-electric machines, 254
---- ---- generating electricity, 269
---- ---- protecting ships against torpedo attacks, 180
---- ---- projecting Whitehead's fish torpedo, 135
Mines, submarine, electrical, 10, 27
---- ----, advantages of, 28
---- ----, defects of, 29
---- ----, mooring, 54
---- ----, in the American war, 27
---- ----, electro-contact, circuit-closers for, 63
---- ----, Fulton's stationary, 5
---- ----, mechanical, 10, 16
---- ----, advantages of, 17
---- ----, extempore, 21
---- ----, McEvoy's, 22
---- ----, improved Singer's, 20
---- ----, mooring, 26
---- ----, Russian electro, 68
---- ----, Singer's, 19
---- ----, rules to be observed in planting, 74
---- ----, sweeping for, 112
Mixtures, explosive, 208
Mode of firing Harvey's torpedoes, 121
---- ----, in 1829, 6
Monitor _Duba Saife_, destruction of the Turkish, 197
Mooring, Austrian method of, 56
---- electrical submarine mines, 54
----, fore and aft, 56
----, ladder, 55
----, launch for placing, 58
Mooring mechanical mines, 26
----, single rope, 56
Morse firing keys, 81
Multiple cables, 43
---- ----, junction boxes for, 52

N.
Nicholl's metallic joint, 45
Nitro-glycerine, 209
Nordenfelt torpedo gun, the, 257
Norwegian torpedo launches, Thornycroft's, 163

O.
Observation, firing by, 69
---- ----, Prussian system of, 73
Observing telescope, shutter apparatus and, 84
Obstructions, destruction of passive, 113
----, Lay's torpedo in clearing away, 151
Offensive torpedo operations, Russian and Turkish, 195
---- ---- warfare still in its infancy, 115
---- torpedoes, failure of, 8, 11
---- ----, general remarks on, 156
Ohm, definition of the, 281
Ohm's law, application of, 276
Operations, torpedo, 187
---- ----, during the American civil war, 189
---- ---- Austrian war, 192
---- ---- Austro-Italian war, 188
---- ---- Crimean war, 187
---- ---- Franco-German war, 192
---- ---- Paraguayan war, 191
---- ---- Russo-Turkish war, 192
---- ---- defensive, Russian, 193
---- ----, Turkish, 193
---- ---- offensive, Turkish and Russian, 195
Ordinary type of torpedo boat, the, 179
Ottoman fleet, cause of failure of the, 14
Outrigger torpedoes, spar or, 154

P.
Papier maché safety plug, McEvoy's, 22
Paraguayan war, torpedo operations during the, 191
Passage through torpedo defences, clearing a, 111
Passive obstructions, destruction of, 113
Patent electric lamp, Siemens', 248
---- torpedo boat protective, Fosberry's, 182
Percussion fuzes, 23
---- ----, McEvoy's, 24
Permanent joint, Siemens', 47
---- magnets, 280
Physical state of the explosive substance, the, 204
Picric powder, 209
Planting submarine mines, rules to be observed in, 74
Plates, Brown's arrangement of earth, 100
----, connections of switch, 100
Platinum wire fuze for conductivity, test of, 101
---- ----, test of resistance of, 101
---- ---- fuzes, 33
---- ----, English service, 33
---- ----, McEvoy's, 34
_Plongeur_, French submarine boat, 185
Plug, Mathieson's cement safety, 21
----, McEvoy's papier maché safety, 22
Pola, torpedo experiments at, 231
Polarization, definition of the term, 273
Porter's torpedo ship _Alarm_, Admiral, 159
Portsmouth, torpedo experiments at, 229, 233
Potential, definition of, 270
----, Voltaic battery test for, 104
Powder, Horsley's, 216
----, picric, 209
Precautions in manipulating the electric light, 252
Primer, Abel's mechanical, 23
----, McEvoy's, 21
Projecting frames for torpedo ship defence, 111
---- Whitehead's fish torpedo, methods of, 138
Propeller, Thornycroft's screw, 170
Properties of a Voltaic cell, definition and, 269
Prussian system of firing by observation, the, 73

Q.
Quadrant electrometers, Thomson's, 86
Qualifications essential to submarine boats, the, 184

R.
Rain's detonating composition, 23
Reflecting galvanometer, Thomson's, 87
Reflector, Colt's, 7
Remarks on offensive torpedoes, general, 156
Resistance boxes, 97
---- of cables, test of electrical, 104
---- platinum wire fuze, test of, 101
----, Voltaic battery test for internal, 104
Resistances by Wheatstone's balance, measurement of, 98
----, circuit, 276
----, measuring electrical, 93
Rheostat, the, 96
Rope mooring, single, 56
Rotation of armatures in Siemens' electric light apparatus, 246
Roux and Sarrau, experiments by, 207
Rules in connection with submarine mines, 29
---- to be observed in forming cable joints, 51
---- ---- planting mines, 74
Russian and Turkish offensive torpedo operations, 194
---- defensive torpedo operations, 193
---- electro-mechanical mines, 68
---- torpedo boat attack at Batoum, 115, 202
---- ---- Matchin, 196
---- ---- Rustchuk, 200
---- ---- Soukoum Kaleh, 201
---- ---- Soulina, 198
---- ---- off the Aluta, 200
---- ----, the final, 203
---- ---- boats, Schibau's, 178
---- ---- launch, Yarrow's, 172
---- torpedoes, 193
Russo-Turkish war, torpedo operations during the, 192
---- ----, torpedoes during the, 14, 115
Rutschuk, Russian torpedo attack at, 200

S.
Safety cock arrangement, Steward's, 25
---- plug, Mathieson's cement, 21
---- ---- McEvoy's papier maché, 22
Schibau's Russian torpedo boats, 178
Science of torpedo warfare, the, 15
Sea cell test for insulation, 106
---- ---- tests, 100
---- service cables, 43
Second class torpedo launches, Thornycroft's, 169
Self-acting circuit closer, the Austrian, 64
Sensitive fuzes, 23
Service cables, land, 43
---- ----, sea, 43
---- platinum wire fuze, English, 33
Ship _Alarm_, Admiral Porter's torpedo, 159
---- defence, 10
----, Fulton's block, 5
Ships against torpedo attacks, methods of protecting, 180
----, employment of torpedo, 158
Shunt, definition of a, 95
---- for Siemens' electric light, self-acting, 245
Shutter apparatus, firing keys and, 80
---- ----, the, 82
---- used with a circuit breaker, 83
---- instrument and observing telescope, 84
Siemens' electric cables, 40
---- ---- light apparatus, 241
---- ----, conducting wires for, 247
---- ----, description of, 241
---- ----, power and light produced by, 244
---- ----, rotation of armatures in, 246
---- ----, self-acting shunt for, 245
---- ----, wear and tear of, 247
---- low tension dynamo machine, 75
---- patent electric lamp, 248
---- permanent joints, 47
---- universal galvanometer, 89
---- ---- tables, 287
Signal, firing by preconcerted, 71
Signals employed in diving, 263
Silvertown electric cables, 41
Singer's mechanical mine, 19
---- ----, McEvoy's improved, 20
Single and double fluid batteries, 272
---- cored armoured cables, 43
---- ---- unarmoured cables, 43
---- fluid cell, action in a, 273
---- main system, McEvoy's, 283
---- rope moorings, 56
Size of torpedo charges, 218
Soukoum Kaleh, Russian torpedo attack at, 201
Soulina, Russian torpedo attack at, 198
Spanish torpedo boats, Yarrow's, 175
Spar or outrigger torpedoes, 154
---- torpedo, McEvoy's duplex, 154
---- torpedoes, Fulton's, 5
Special cables, 43
Spherical shaped torpedo case, the, 32
Spiral spring circuit closer, Mathieson's, 63
Stake torpedoes, 18
State of the explosive substance, the physical, 204
Statham's high tension fuze, 35
Stationary mines, Fulton's, 5
Steward's safety cock arrangement, 25
Stokes Bay, experiments with countermines at, 236
Submarine boat, Bushnell's, 2, 184
---- ----, Confederate, 185
---- ----, French, 185
---- boats, 183
---- ----, qualifications essential to, 184
---- mines 13
---- ----, during the Crimean and American wars, 27
---- ----, rules for using, 29
---- ----, sweeping for, 112
---- ----, electrical, 27
---- ----, advantages of, 28
---- ----, defects of, 29
---- ----, mooring, 54
Submersion, tests after, 106
Success in torpedo warfare, elements of, 16
_Suna_, destruction of the Turkish vessel, 194
Swedish torpedo launch, Thornycroft's, 165
Sweeping for submarine mines, 112
Switch plates, commutators or, 96
---- ----, connections of, 100
Synopsis, 290
System, McEvoy's single main, 283
---- of electrical testing, Armstrong's, 107
---- ---- firing by observation, Prussian, 73
---- ---- tests, object of, 84

T.
T junction box, the, 53
Table, the Austrian testing, 108
Tables, Siemens' universal galvanometer, 287
----, test, 99
Tactics with Harvey's torpedoes, 127
Telegraph batteries, 79
Telescope, shutter instrument and observing, 84
Tension dynamo machines, Siemens' low, 75
---- fuses, testing high, 102
Term torpedo, definition of the, 115
Terms electro-positive and electro-negative, the, 271
Test battery, the Menotti, 79
----, discharge, 103
---- for electrical cables, insulation, 102
---- of electrical resistance of cables, 104
---- ---- insulated joints, electrical, 104
---- ---- platinum wire fuze for conductivity, 101
---- ---- resistance, 101
---- tables, 99
Testing, Armstrong's system of electrical, 107
----, Austrian method of, 109
---- high tension fuzes, 102
----, instruments used in, 85
---- table, Austrian, 108
Tests after submersion, 106
----, electrical, 85
---- for insulation, sea cell, 106
----, mechanical, 85
----, object of a system, 84
----, sea cell, 100
Theoretical knowledge of torpedoes, 8
Theory of detonation, the, 206
---- ---- electricity, the, 265
Thermo galvanometer, the, 89
Thomson's quadrant electrometer, 86
---- reflecting galvanometer, 87
Thornycroft's boat engines, efficiency of, 171
---- method of carrying fish torpedoes, 140
---- propeller, 170
---- torpedo launches, 163
---- ----, Austrian and French, 165
---- ----, Danish and Swedish, 165
---- ----, Dutch and Italian, 168
---- ----, French, 169
---- ----, Norwegian, 163
---- ----, second class, 169
Three coil galvanometer, 88
Torpedo attacks, boat, 180, 191
---- ----, methods of protecting ships against, 180
---- boat, Lay's, 141
---- ----, capabilities of, 147
---- ----, an improved form of, 153
---- ---- attack, Russian, at Batoum, 195, 202
---- ---- ---- ---- Matchin, 196
---- ---- ---- ---- Rustchuk, 200
---- ---- ---- ---- Soukoum Kaleh, 201
---- ---- ---- ---- Soulina, 198
---- ---- ----, off the Aluta, 200
---- ---- ----, the final, 203
---- ---- experiment at Cherbourg, 170
---- ---- for flotation, 171
---- ---- _Lightning_, Thornycroft's, 168
---- ---- protective, Fosberry's patent, 182
---- boats, 162
---- ----, Herreshoff's, 178
---- ----, ordinary type of, 179
---- ----, Schibau's Russian, 178
---- ----, Yarrow's, 172
---- ----, description of a, 172
---- ---- Dutch, 172
---- ---- English, 173
---- ---- Russian, 172
---- ---- Spanish, 175
---- case, form and construction of, 31
---- ----, conical shaped, 32
---- ----, cylindrical shaped, 32
---- ----, spherical shaped, 32
---- charges, size of, 218
---- defences, clearing a passage through, 111
---- experiments at Carlscrona, 220, 224, 232
---- ---- Chatham, 220
---- ---- Copenhagen, 223
---- ---- Kiel, 222
---- ---- Pola, 231
---- ---- Portsmouth, 229, 233
---- ---- in Austria, 220
---- ---- England, 222
---- ---- Turkey, 232
---- explosive agents, 217
Torpedo guns, 257
---- ----, Hotchkiss, 259
---- ----, Nordenfelt, 257
---- invention and adoption of the fish, 131
---- launches, Thornycroft's, 163
---- operations, 187
---- ---- during the Austro-Italian war, 188
---- ---- Crimean war, 187
---- ---- Franco-German war, 192
---- ---- Paraguayan war, 191
---- ---- Russo-Turkish war, 192
---- ----, Russian defensive, 193
---- ----, Turkish defensive, 193
---- ---- and Russian offensive, 195
---- ship _Alarm_, Admiral Porter's, 159
---- ---- _Destroyer_, Ericsson's, 160
---- ---- _Uhlan_, the German, 158
---- ships, employment of, 158
---- spar, McEvoy's duplex, 154
---- ---- or outrigger, 154
----, the term, 115
---- warfare, defensive, 13
---- ----, elements of success, 16
---- ----, science of, 15
---- ---- still in its infancy, offensive, 115
----, Whitehead's fish, 133
---- ----, adjustments of, 136
---- ----, capabilities of, 134
---- ----, methods of projecting, 138
----, Woolwich fish, the, 140
----, American extempore drifting, 119
----, barrel, 19
----, Brook's, 19
----, Bushnell's drifting, 2
---- ----, invention of, 2
----, drifting, 116
----, floating, 116
----, frame, 18
----, Fulton's drifting, 5
---- ---- harpoon, 5
---- ---- spar, 5
----, general remarks on offensive, 156
---- in war, the employment of fish, 133
----, Lewis's drifting, 117
----, locomotive, 131
----, McEvoy's drifting, 118
----, moral effect of, 9
----, offensive, 11
---- ----, failure of 8
----, stake 18
----, towing 119
---- ----, French, 131
---- ----, Harvey's, 119
---- ----, methods of attack with, 127
---- ----, the value of, 129
---- ----, Mensing's, 130
----, turtle 19
Turkey, torpedo experiments in, 232
Turkish defensive torpedo operations, 193
---- monitor _Duba Saife_, destruction of the, 197
---- offensive torpedo operations, 195
---- ship _Suna_, loss of the, 194
---- torpedoes, 193
---- war, torpedoes during the Russo-, 115
Turk's head, McEvoy's mechanical, 53
Turtle torpedoes, 19

U.
_Uhlan_, the German torpedo vessel, 158
Unarmoured cables, single cored, 43
Universal galvanometer, Siemens', 89
---- ----, tables, 287
Use of circuit closers, the, 60

V.
Vessel _Destroyer_, Ericsson's torpedo, 160
---- in the world, the fastest, 177
---- _Uhlan_, the German torpedo, 158
Voltaic batteries, 79
---- battery, Leclanché's, 77
---- ----, Von Ebner's, 76
---- ----, test for electro-motive force, 105
---- ---- internal resistance, 104
---- ---- potential, 104
---- cell, definition and properties of a, 269
---- current, the, 70
Von Ebner's high tension fuze, 36
---- ---- Voltaic battery, 6

W.
War, employment of fish torpedoes in, 133
----, torpedo operations during the American civil, 189
---- ---- Austrian, 192
---- ---- Austro-Italian, 188
---- ---- Crimean, 187
---- ---- Franco-German, 192
---- ---- Paraguayan, 191
---- ---- Russo-Turkish, 192
----, torpedoes during the American civil, 115
---- ----, Russo-Turkish, 115
Warfare, defensive torpedo, 13
----, elements of success in torpedo, 16
----, science of torpedo, 15
---- still in its infancy, offensive torpedo, 115
Wars, submarine mines in the Crimean and American, 27
Wear and tear of Siemens' electric light apparatus, 247
Welden railway saved by torpedoes, the, 190
Wheatstone's balance, 97
---- ----, manipulation of, 99
---- ----, measurement of resistances by, 98
Whitehead's fish torpedo, 133
---- ----, adjustments of, 136
---- ----, capabilities of, 134
---- ----, methods of projecting, 138
---- ----, mode of ignition of, 135
Wire fuze for conductivity, test of platinum, 101
---- ----, test of resistance of platinum, 101
Wire fuzes, platinum, 33
---- ----, English service, 33
---- ----, McEvoy's, 34
Wires in McEvoy's spar torpedo, arrangement of, 155
Woolwich fish torpedo, the, 140

Y.
Yarrow's torpedo boats, 172
---- ----, English, 173
---- ----, Spanish, 175
---- ---- launch, description of a, 172
---- ---- launches, Dutch, 172
---- ----, Russian, 172

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* * * * *

Transcriber's Notes:

Obvious punctuation errors have been repaired. Varied hyphenation was
retained. The errors noted in the book's errata section have been
repaired in the text except for the final one for page 285 where the
transcriber could not find a "e" to change to a "d" at that location.

Text uses both fuse and fuze. "Fuze" is usually used in the English
language to mean more complicated fuses.

Inconsistencies in italic usage was retained. For example, on page 98,
"R" is referenced originally without italics in an equation and after
on the same page is italicized when mentioned.

Page 17, "principle" changed to "principal" (principal ones being)

Page 77, "16'" changed to "16"" (about 16" long, 9" deep)

Page 114, "Northerners'" changed to "Northerners'" (most of the
Northerners' vessels)

Page 132, "torpedos" changed to "torpedoes" (Whitehead's fish torpedoes
have)

Page 134, "14" changed to "140" (140 atmospheres)

Page 162, equal sign added to equation ((314 × 200) / 196 = 320 lbs)

Page 168, "THORNICROFT'S" changed "THORNYCROFT'S" on Plate XLVII.

Page 170, "THORNICROFT'S" changed "THORNYCROFT'S" on Plate XLVIII.

Page 199, "Poustchin" changed to "Poutschin" (Alongside Poutschin
remained for some)

Page 208, "spaces" changed to "space" (intervening space of)

Page 212, subscript for O in chemical formula was unreadable. "5" was
presumed and added. (the formula _CH_{7}(NO_{2})_{3}O_{5}_)

Page 240, "Seimens" changed to "Siemens" (due to both Dr. Siemens)

Page 241, "Seimens" changed to "Siemens" (that the Siemens machine)

Page 271, this paragraph seems to be missing a word but was retained as
printed as the word could not be presumed by research.

"Oxygen" is the most important element of an
electrolyte, and to the _affinity for oxygen of the
metals_ is the magnitude of the result and effect.

Page 298, "Calland" changed to "Callaud" (Calland and Marié-Davy)

Page 302, "dislectric" changed to "dielectric" (Gutta-percha as a
dielectric)

Page 11, advertising page, "Portsmouth." added to publisher line at
bottom of page. Original ended with (_Griffin & Co Publishers, 2, The
Hard,_)

*** End of this LibraryBlog Digital Book "Torpedoes and Torpedo Warfare" ***

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