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Title: Inventions of the Great War
Author: Bond, A. Russell (Alexander Russell), 1876-
Language: English
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[Illustration: Oil-tempering the lining of a Big Gun (See page 76)]


INVENTIONS OF THE GREAT WAR

by

A. RUSSELL BOND

Managing Editor of "Scientific American,"
Author of "On the Battle-Front of Engineering," etc.

With Many Illustrations



[Illustration]

New York
The Century Co.
1919

Copyright, 1918, 1919, by
The Century Co.

Published, June, 1919



PREFACE


The great World War was more than two-thirds over when America entered
the struggle, and yet in a sense this country was in the war from
its very beginning. Three great inventions controlled the character
of the fighting and made it different from any other the world has
ever seen. These three inventions were American. The submarine was
our invention; it carried the war into the sea. The airplane was an
American invention; it carried the war into the sky. We invented the
machine-gun; it drove the war into the ground.

It is not my purpose to boast of American genius but, rather, to show
that we entered the war with heavy responsibilities. The inventions we
had given to the world had been developed marvelously in other lands.
Furthermore they were in the hands of a determined and unscrupulous
foe, and we found before us the task of overcoming the very machines
that we had created. Yankee ingenuity was faced with a real test.

The only way of overcoming the airplane was to build more and better
machines than the enemy possessed. This we tried to do, but first
we had to be taught by our allies the latest refinements of this
machine, and the war was over before we had more than started our
aërial program. The machine-gun and its accessory, barbed wire (also
an American invention), were overcome by the tank; and we may find
what little comfort we can in the fact that its invention was inspired
by the sight of an American farm tractor. But the tank was a British
creation and was undoubtedly the most important invention of the war.
On the sea we were faced with a most baffling problem. The U-boat
could not be coped with by the building of swarms of submarines. The
essential here was a means of locating the enemy and destroying him
even while he lurked under the surface. Two American inventions, the
hydrophone and the depth bomb, made the lot of the U-boat decidedly
unenviable and they hastened if they did not actually end German
frightfulness on the sea.

But these were by no means the only inventions of the war. Great
Britain showed wonderful ingenuity and resourcefulness in many
directions; France did marvels with the airplane and showed great
cleverness in her development of the tank and there was a host of
minor inventions to her credit; while Italy showed marked skill in the
creation of large airplanes and small seacraft.

The Central Powers, on the other hand, were less originative but showed
marked resourcefulness in developing the inventions of others. Forts
were made valueless by the large portable Austrian guns. The long range
gun that shelled Paris was a sensational achievement, but it cannot be
called a great invention because it was of little military value. The
great German Zeppelins were far from a success because they depended
for their buoyancy on a highly inflammable gas. It is interesting to
note that while the Germans were acknowledging the failure of their
dirigibles the British were launching an airship program, and here in
America we had found an economical way of producing a non-inflammable
balloon gas which promises a great future for aërial navigation.

The most important German contribution to the war--it cannot be
classed as an invention--was poison gas, and it was not long ere they
regretted this infraction of the rules of civilized warfare adopted at
the Hague Conference; for the Allies soon gave them a big dose of their
own medicine and before the war was over, fairly deluged them with
lethal gases of every variety.

Many inventions of our own and of our allies were not fully developed
when the war ended, and there were some which, although primarily
intended for purposes of war, will be most serviceable in time of
peace. For this war was not one of mere destruction. It set men to
thinking as they had never thought before. It intensified their
inventive faculties, and as a result, the world is richer in many ways.
Lessons of thrift and economy have been taught us. Manufacturers have
learned the value of standardization. The business man has gained an
appreciation of scientific research.

The whole story is too big to be contained within the covers of a
single book, but I have selected the more important and interesting
inventions and have endeavored to describe them in simple language for
the benefit of the reader who is not technically trained.

        A. RUSSELL BOND

New York, May, 1919



CONTENTS


  CHAPTER                                           PAGE

     I  THE WAR IN AND UNDER THE GROUND                3

    II  HAND-GRENADES AND TRENCH MORTARS              20

   III  GUNS THAT FIRE THEMSELVES                     41

    IV  GUNS AND SUPER-GUNS                           62

     V  THE BATTLE OF THE CHEMISTS                    85

    VI  TANKS                                        107

   VII  THE WAR IN THE AIR                           123

  VIII  SHIPS THAT SAIL THE SKIES                    148

    IX  GETTING THE RANGE                            169

     X  TALKING IN THE SKY                           184

    XI  WARRIORS OF THE PAINT-BRUSH                  209

   XII  SUBMARINES                                   232

  XIII  GETTING THE BEST OF THE U-BOAT               253

   XIV  "DEVIL'S EGGS"                               276

    XV  SURFACE BOATS                                298

   XVI  RECLAIMING THE VICTIMS OF THE SUBMARINES     310

        INDEX                                        339



LIST OF ILLUSTRATIONS


  Oil-tempering the lining of a big gun                 _Frontispiece_

                                                                FACING
                                                                 PAGE

  Lines of zig-zag trenches as viewed from an aëroplane              8

  French sappers using stethoscopes to detect the mining
      operations of the enemy                                        9

  A 3-inch Stokes mortar and two of its shells                      36

  Dropping a shell into a 6-inch trench mortar                      36

  The Maxim machine-gun operated by the energy of the recoil        37

  Colt machine-gun partly broken away to show the operating
      mechanism                                                     37

  The Lewis gun which produces its own cooling current              44

  The Benèt-Mercié gun operated by gas                              44

  Browning machine-gun, weighing 34-1/2 pounds                      45

  Browning machine-rifle, weight only 15 pounds                     45

  Lewis machine-guns in action at the front                         52

  An elaborate German machine-gun fort                              53

  Comparative diagram of the path of a projectile from the German
      super-gun                                                     60

  One of our 16-inch coast defence guns on a disappearing mount     61

  Height of gun as compared with the New York City Hall             61

  The 121-mile gun designed by American ordnance officer            68

  American 16-inch rifle on a railway mount                         69

  A long-distance sub-calibered French gun on a railway mount       76

  Inside of a shrapnel shell and details of the fuse cap            77

  Search-light shell and one of its candles                         77

  Putting on the gas-masks to meet a gas cloud attack               84

  Even the horses had to be masked                                  85

  Portable flame-throwing apparatus                                 85

  Liquid fire streaming from fixed flame-throwing apparatus         92

  Cleaning up a dugout with the "fire-broom"                        93

  British tank climbing out of a trench at Cambrai                 112

  Even trees were no barrier to the British tank                   113

  The German tank was very heavy and cumbersome                    113

  The speedy British "Whippet" tank that can travel at a speed of
      twelve miles per hour                                        120

  The French high-speed "baby" tank                                120

  Section through our Mark VIII tank showing the layout of the
      interior                                                     121

  A Handley-Page bombing plane with one of its wings folded
      back                                                         128

  How an object dropped from the Woolworth Building would
      increase its speed in falling                                129

  Machine-gun mounted to fire over the blades of the propeller     136

  Mechanism for firing between the blades of the propeller         136

  It would take a hundred horses to supply the power for a small
      airplane                                                     137

  The flying-tank                                                  144

  An N-C (Navy-Curtiss) seaplane of the type that made the first
      flight across the Atlantic                                   145

  A big German Zeppelin that was forced to come down on French
      soil                                                         148

  Observation car lowered from a Zeppelin sailing above the
      clouds                                                       149

  Giant British dirigible built along the lines of a Zeppelin      156

  One of the engine cars or "power eggs" of a British dirigible    156

  Crew of the C-5 (American coastal dirigible) starting for
      Newfoundland to make a transatlantic flight                  157

  The curious tail of a kite balloon                               160

  Observers in the basket of an observation balloon                160

  Enormous range-finders mounted on a gun turret of an American
      warship                                                      161

  British anti-aircraft section getting the range of an enemy
      aviator                                                      176

  A British aviator making observations over the German lines      177

  Radio headgear of an airman                                      192

  Carrying on conversation by radio with an aviator miles away     192

  Long distance radio apparatus at the Arlington (Va.) station     193

  A giant gun concealed among trees behind the French lines        212

  Observing the enemy from a papier-mâché replica of a dead horse  213

  Camouflaged headquarters of the American 26th Division in
      France                                                       220

  A camouflaged ship in the Hudson River on Victory Day            221

  Complex mass of wheels and dials inside a German submarine       240

  Surrendered German submarines, showing the net cutters at the
      bow                                                          241

  Forward end of a U-boat                                          256

  A depth bomb mortar and a set of "ash cans" at the stern of
      an American destroyer                                        257

  A depth bomb mortar in action and a depth bomb snapped as it
      is being hurled through the air                              260

  Airplane stunning a U-boat with a depth bomb                     261

  The false hatch of a mystery ship                                268

  The same hatch opened to disclose the 3-inch gun and crew        268

  A French hydrophone installation with which the presence of
      submarines was detected                                      269

  Section of a captured mine-laying U-boat                         272

  A paravane hauled up with a shark caught in its jaws             273

  A Dutch mine-sweeper engaged in clearing the North Sea of
      German mines                                                 288

  Hooking up enemy anchored mines                                  289

  An Italian "sea tank" climbing over a harbor boom                300

  Deck of a British aircraft mothership or "hush ship"             301

  Electrically propelled boat or surface torpedo, attacking a
      warship                                                      304

  Hauling a seaplane up on a barge so that it may be towed         305

  Climbing into an armored diving suit                             320

  Lowering an armored diver into the water                         320

  A diver's sea sled ready to be towed along the bed of the sea    321

  The sea sled on land showing the forward horizontal and after
      vertical rudders                                             321

  The diving sphere built for deep sea salvage operations          324

  The pneumatic breakwater                                         325



  INVENTIONS
  OF THE GREAT WAR



CHAPTER I

THE WAR IN AND UNDER THE GROUND


For years the Germans had been preparing for war. The whole world
knew this, but it had no idea how elaborate were their preparations,
and how these were carried out to the very minutest detail. When the
call to arms was sounded, it was a matter of only a few hours before a
vast army had been assembled--fully armed, completely equipped, ready
to swarm over the frontiers into Belgium and thence into France. It
took much longer for the French to raise their armies of defense, and
still longer for the British to furnish France with any adequate help.
Despite the heroic resistance of Belgium, the Entente Allies were
unprepared to stem the tide of German soldiers who poured into the
northern part of France.

So easy did the march to Paris seem, that the Germans grew careless
in their advance and then suddenly they met with a reverse that sent
them back in full retreat. However, the military authorities of Germany
had studied not only how to attack but also how to retreat and how
to stand on the defensive. In this, as in every other phase of the
conflict, they were far in advance of the rest of the world, and after
their defeat in the First Battle of the Marne, they retired to a strong
position and hastily prepared to stand on the defensive. When the
Allies tried to drive them farther back, they found that the German
army had simply sunk into the ground. The war of manoeuver had given
way to trench warfare, which lasted through long, tedious months nearly
to the end of the great conflict.

The Germans found it necessary to make the stand because the Russians
were putting up such a strong fight on Germany's eastern frontier.
Men had to be withdrawn from the western front to stem the Russian
tide, which meant that the western armies of the kaiser had to cease
their offensive activities for the time being. The delay was fatal
to the Germans, for they had opposed to them not only brave men but
intelligent men who were quick to learn. And when the Germans were
ready to resume operations in the West, they found that the Allies also
had sunk into the ground and had learned all their tricks of trench
warfare, adding a number of new ones of their own.

The whole character of the war was changed. The opposing forces were
dead-locked and neither could break through the other's lines. The idea
of digging into the ground did not originate with this war, but never
before had it been carried out on so extensive a scale. The inventive
faculties of both sides were vainly exercised to find some way of
breaking the dead-lock. Hundreds of new inventions were developed. The
history of war from the days of the ancient Romans up to the present
time was searched for some means of breaking down the opposing lines.
However, the dead-lock was not broken until a special machine had been
invented, a traveling fort. But the story of that machine is told in
another chapter.

At the outset the Allies dug very shallow ditches, such as had been
used in previous wars. When it was found that these burrows would have
to be occupied for weeks and months, the French and British imitated
the Germans and dug their trenches so deep that men could walk through
them freely, without danger of exposing their heads above ground; and
as the ditches grew deeper, they had to be provided with a firing-step
on which the riflemen could stand to fire over the top of the trenches.
The trenches were zig-zagged so that they could not be flanked,
otherwise they would have made dangerous traps for the defenders; for
had the enemy gained one end of the trench, he could have fired down
the full length of it, killing or wounding every man it contained. But
zig-zagging made it necessary to capture each turn separately. There
were lines upon lines of these trenches. Ordinarily there were but
three lines, several hundred feet apart, with communicating trenches
connecting them, and then several kilometers[1] farther back were
reserve trenches, also connected by communicating trenches with the
front lines.

      [1] A kilometer is, roughly, six tenths of a mile; or six
          miles would equal ten kilometers.

Men did not dare to show themselves out in the open near the
battle-front for a mile or more behind the front-line trenches, for the
enemy's sharp-shooters were always on the watch for a target. The men
had to stay in the trenches day and night for two or more weeks at a
time, and sleeping-accommodations of a very rough sort were provided
for them in dugouts which opened into the trenches. The dugouts of the
Allies were comparatively crude affairs, but the Germans spent a great
deal of time upon their burrows.


UNDERGROUND VILLAGES

When the French first swept the Germans back out of their trenches
along the Aisne, they were astonished to find how elaborate were
these underground dwellings. They found that the ground was literally
honeycombed with rooms and passageways. Often the dugouts were two
stories in depth and extended as much as sixty feet below the level
of the ground. In fact, all along this part of the front, the Germans
had a continuous underground village in which thousands of men were
maintained. The officers' quarters were particularly well fitted up,
and every attention was given to the comfort of their occupants. There
were steel door-mats at the entrances of the quarters. The walls were
boarded and even papered. The bedrooms were fitted with spring beds,
chiffoniers, and wash-stands, and all the rooms were lighted with
electric lamps. There were spacious quarters for the men, with regular
underground mess halls and elaborate kitchens. There were power-plants
to furnish steam for the operation of pumps and for the lighting-plants
and for other purposes.

[Illustration: (C) Underwood & Underwood

Lines of Zig-Zag Trenches as viewed from an Airplane]

There was a chalk formation here in which were many large natural
caves. One enormous cave was said to have held thirty thousand
soldiers, and in this section the Germans kept large reserve forces. By
digging far into the ground, the German troops secured protection from
shell-fire; in fact, the horrible noise of battle was heard only as a
murmur, down in these depths. With characteristic thoroughness, the
Germans built their trench system for a long stay; while the Allies,
on the other hand, looked upon _their_ trenches as merely temporary
quarters, which would hold the enemy at bay until they could build up
armies large enough to drive the invaders out of the country. The
construction of the trenches along some parts of the battle-line was
particularly difficult, because of the problem of drainage. This was
especially true in Flanders, where the trenches in many cases were
below water-level, and elaborate pumping-systems had to be installed
to keep them dry. Some of them were concrete-lined to make them
waterproof. In the early stages of the war, before the trenches were
drained, the men had to stand in water for a good part of the time,
and the only way they could get about at all in the miry trenches was
by having "duck-boards" in them. Duck-boards are sections of wooden
sidewalk such as we find in small villages in this country, consisting
of a couple of rails on which crosspieces of wood are nailed. These
duck-boards fairly floated in the mud.

[Illustration: Courtesy of "Scientific American"

French Sappers using Stethoscopes to detect the Mining Operations of
the Enemy]

Some of the trenches were provided with barbed wire barriers or gates
calculated to halt a raiding-party if it succeeded in getting into the
trench. These gates were swung up out of the way, but when lowered they
were kept closed with a rather complicated system of bolts which the
enemy would be unable to unfasten without some delay; and while he
was struggling to get through the gate, he would be a target for the
bullets of the defenders.


HIDING RAILROADS IN DITCHES

Because of the elaborate system of trenches, and the distance from the
front line to that part of the country where it was safe to operate
in the open, it was necessary to build railways which would travel
through tunnels and communicating trenches to the front lines. These
were narrow-gage railroads and a special standard form of track section
was designed, which was entirely of metal, something like the track
sections of toy railroads. The tracks were very quickly laid and taken
up at need. The locomotives had to be silent and smokeless and so a
special form of gasolene locomotive was invented to haul the little
cars along these miniature railroads to the front lines. Usually the
trench railroads did not come to the very front of the battle-line, but
their principal use was to carry shell to the guns which were located
in concealed positions. Railroad or tramway trenches could not be
sharply zig-zagged but had to have easy curves, which were apt to be
recognized by enemy airplanes, and so they were often concealed under
a covering of wire strewn with leaves.


PERISCOPES AND "SNIPERSCOPES"

But while the armies were buried underground, it was necessary for them
to keep their eyes upon each other so that each might be ready for
any sudden onslaught of the other. Snipers were always ready to fire
at any head that showed itself above the parapet of the trench and so
the soldiers had to steal an idea from the submarines and build them
periscopes with which they could look over the top of their trenches
without exposing themselves. A trench periscope was a very simple
affair, consisting of a tube with two mirrors, one at the top and one
at the bottom, set at such an angle that a person looking into the side
of the tube at the bottom could see out of the opposite side of the
tube at the top.

Observation posts were established wherever there was a slight rise in
the ground. Sometimes these posts were placed far in advance of the
trenches and sometimes even behind the trenches where it was possible
to obtain a good view of the opposing lines. Sometimes a tunnel would
be dug forward, leading to an outlet close to the enemy's lines, and
here an observer would take his position at night to spy with his ears
upon the activities of the enemy. Observers who watched the enemy by
day would often not dare to use periscopes, which might be seen by the
enemy and draw a concentrated fire of rifles and even shell. So that
every manner of concealment was employed to make the observation posts
invisible and to have them blend with their surroundings. Observers
even wore veils so that the white of their skin would not betray them.

[Illustration: Redrawn from Military Map Reading by permission of E. C.
McKay

FIG. 1. A "sniperscope" with which a sharpshooter could take aim
without showing his head above the parapet]

Snipers were equally ingenious in concealing themselves. They
frequently used rifles which were connected with a dummy butt and
had a periscope sighting-attachment. This attachment was called a
"sniperscope." The rifle-barrel could be pushed through a loophole in
the parapet and the sniper standing safely below the parapet could hold
the dummy butt to his shoulder and aim his rifle with perfect accuracy
by means of the periscope. It was next to impossible to locate a sniper
hidden in this way. One method of doing it was to examine rubbish, tin
cans, or any object that had been penetrated by a bullet and note the
direction taken by the bullet. This would give a line leading toward
the source of the shot, and when a number of such lines were traced,
they would cross at a spot where the sniper or his gun was stationed,
and a few shell would put the man out of business. Dummy heads of
papier mâché were sometimes stuck above the parapet to draw the fire of
enemy snipers and the bullet-holes which quickly appeared in them were
studied to discover the location of the snipers.

[Illustration: Redrawn from Military Map Reading by permission of E. C.
McKay

FIG. 2. A fixed rifle stand arranged to be fired after dark]

Sometimes fixed rifles were used. These were set on stands so that
they could be very accurately trained upon some important enemy post.
Then they could be fired in the dark, without aiming, to disturb night
operations of the enemy. Often a brace of rifles, as many as six, would
be coupled up to be fired simultaneously, and by operating a single
lever each gun would throw out the empty cartridge shell and bring a
fresh one into position.


STEEL BRIER PATCHES

The most important defense of a trench system consisted in the barbed
wire entanglements placed before it. Barbed wire, by the way, is
an American invention, but it was originally intended for the very
peaceful purpose for keeping cattle within bounds. Long ago it was
used in war, but never to the extent to which it was employed in this
world struggle. The entanglements were usually set up at night and were
merely fences consisting of stout posts driven into the ground and
strung with barbed wire running in all directions, so as to make an
impenetrable tangle. Where it was possible to prepare the entanglements
without disturbance and the position was an important one, the mass of
barbed wire often extended for a hundred yards or more in depth. Just
beyond the entanglements trip-wires were sometimes used. A trip-wire
was a slack wire which was laid on the ground. Before being laid, the
wire was tightly coiled so that it would not lie flat, but would catch
the feet of raiders and trip them up. Each side had "gates" in the
line through which this wire could quickly be removed to let its own
raiding-parties through. Sometimes raiders used tunnels, with outlets
beyond the barbed wire, but they had to cut their way through the metal
brier patches of their opponents.

Early in the war, various schemes were devised for destroying the
entanglements. There were bombs in the form of a rod about twelve
feet long, which could be pushed under the wire and upon exploding
would tear it apart. Another scheme was to fire a projectile formed
like a grapnel. The projectile was attached to the end of a cable
and was fired from a small gun in the same way that life-lines are
thrown out to wrecks near shore. Then the cable would be wound up on a
winch and the grapnel hooks would tear the wire from its fastenings.
Such schemes, however, did not prove very practicable, and it was
eventually found that a much better way of destroying barbed wire was
to bombard it with high-explosive shell, which would literally blow the
wire apart. But it required a great deal of shelling to destroy these
entanglements, and it was really not until the tank was invented that
such obstructions could be flattened out so that they formed no bar to
the passage of the soldiers.

The Germans not only used fixed entanglements, but they had large
standard sections of barbed wire arranged in the form of big
cylindrical frames which would be carried easily by a couple of men and
could be placed in position at a moment's notice to close a gap in the
line or even to build up new lines of wire obstruction.


MINES AND COUNTER-MINES

In the earlier stages of the war it proved so impossible to capture a
trench when it was well defended by machine-guns that efforts were made
to blow up the enemy by means of mines. Tunnels were dug reaching out
under the enemy's lines and large quantities of explosives were stored
in them. At the moment when it was intended to make an assault, there
would be a heavy cannonading to disconcert the enemy, and then the mine
would be touched off. In the demoralizing confusion that resulted, the
storming-party would sweep over the enemy. Such mines were tried on
both sides, and the only protection against them was to out-guess the
other side and build counter-mines.

If it were suspected, from the importance of a certain position and the
nature of the ground, that the enemy would probably try to undermine
it, the defenders would dig tunnels of their own toward the enemy at a
safe distance beyond their own lines and establish listeners there to
see if they could hear the mining-operations of their opponents. Very
delicate microphones were used, which the listeners would place on the
ground or against the walls of their tunnel. Then they would listen
for the faintest sound of digging, just as a doctor listens through
a stethoscope to the beating of a patient's heart or the rush of air
through his lungs. When these listening-instruments picked up the noise
of digging, the general direction of the digging could be followed
out by placing the instrument at different positions and noting where
the noise was loudest. Then a counter-mine would be extended in that
direction, far enough down to pass under the enemy's tunnel, and at the
right moment, a charge of TNT (trinitrotoluol) would be exploded, which
would destroy the enemy's sappers and put an end to their ambitious
plans.

A very interesting case of mining was furnished by the British when
they blew up the important post of Messines Ridge. This was strongly
held by the Germans and the only way of dislodging the enemy was to
blow off the top of the ridge. Before work was started, geologists
were called upon to determine whether or not the ground were suitable
for mining-operations. They picked out a spot where the digging was
good from the British side, but where, if counter-mines were attempted
from the German side, quicksands would be encountered and tunneling
of any sort would be difficult. The British sappers could, therefore,
proceed with comparative safety. The Germans suspected that something
of the sort was being undertaken, but they found it very difficult to
dig counter-mines. However, one day their suspicions were confirmed,
when the whole top of the hill was blown off, with a big loss of German
lives. In the assault that followed the British captured the position
and it was annexed to the British lines.



CHAPTER II

HAND-GRENADES AND TRENCH MORTARS


In primitive times battles were fought hand-to-hand. The first
implements of war were clubs and spears and battle-axes, all intended
for fighting at close quarters. The bow and arrow enabled men to fight
at a distance, but shields and armor were so effective a defense
that it was only by hand-to-hand fighting that a brave enemy could
be defeated. Even the invention of gunpowder did not separate the
combatants permanently, for although it was possible to hurl missiles
at a great distance, cannon were so slow in their action that the
enemy could rush them between shots. Shoulder firearms also were
comparatively slow in the early days, and liable to miss fire, and it
was not until the automatic rifle of recent years was fully developed
that soldiers learned to keep their distance.

When the great European war started, military authorities had come to
look upon war at close quarters as something relegated to bygone days.
Even the bayonet was beginning to be thought of little use. Rifles
could be charged and fired so rapidly and machine-guns could play
such a rapid tattoo of bullets, that it seemed impossible for men to
come near enough for hand-to-hand fighting, except at a fearful cost
of life. In developing the rifle, every effort was made to increase
its range so that it could be used with accuracy at a distance of a
thousand yards and more. But when the Germans, after their retreat in
the First Battle of the Marne, dug themselves in behind the Aisne, and
the French and British too found it necessary to seek shelter from
machine-gun and rifle fire by burrowing into the ground, it became
apparent that while rifles and machine-guns could drive the fighting
into the ground, they were of little value in continuing the fight
after the opposing sides had buried themselves. The trenches were
carried close to one another, in some instances being so close that the
soldiers could actually hear the conversation of their opponents across
the intervening gap. Under such conditions long-distance firearms were
of very little practical value. What was needed was a short-distance
gun which would get down into the enemy trenches. To be sure, the
trenches could be shelled, but the shelling had to be conducted from a
considerable distance, where the artillery would be immune to attack,
and it was impossible to give a trench the particular and individual
attention which it would receive at the hands of men attacking it at
close quarters.

Before we go any farther we must learn the meaning of the word
"trajectory." No bullet or shell travels in a straight line. As soon
as it leaves the muzzle of the gun, it begins to fall, and its course
through the air is a vertical curve that brings it eventually down to
the ground. This curve is called the "trajectory." No gun is pointed
directly at a target, but above it, so as to allow for the pull of
gravity. The faster the bullet travels, the flatter is this curve or
trajectory, because there is less time for it to fall before it reaches
its target. Modern rifles fire their missiles at so high a speed that
the bullets have a very flat trajectory. But in trench warfare a flat
trajectory was not desired. What was the use of a missile that traveled
in a nearly straight line, when the object to be hit was hiding in
the ground? Trench fighting called for a missile that had a very high
trajectory, so that it would drop right into the enemy trench.


HAND-ARTILLERY

Trench warfare is really a close-quarters fight of fort against fort,
and the soldiers who manned the forts had to revert to the ancient
methods of fighting an enemy intrenched behind fortifications.
Centuries ago, not long after the first use of gunpowder in war, small
explosive missiles were invented which could be thrown by hand. These
were originally known as "flying mortars." The missile was about the
size of an orange or a pomegranate, and it was filled with powder and
slugs. A small fuse, which was ignited just before the device was
thrown, was timed to explode the missile when it reached the enemy.
Because of its size and shape, and because the slugs it contained
corresponded, in a manner, to the pulp-covered seeds with which a
pomegranate is filled, the missile was called a "grenade."

Grenades had fallen out of use in modern warfare, although they had
been revived to a small extent in the Russo-Japanese war, and had
been used with some success by the Bulgarians and the Turks in the
Balkan wars. And yet they had not been taken very seriously by the
military powers of Europe, except Germany. Germany was always on the
lookout for any device that might prove useful in war, and when the
Germans dug themselves in after the First Battle of the Marne, they had
large quantities of hand-grenades for their men to toss over into the
trenches of the Allies. These missiles proved very destructive indeed.
They took the place of artillery, and were virtually hand-thrown
shrapnel.

The French and British were entirely unprepared for this kind of
fighting, and they had hastily to improvise offensive and defensive
weapons for trench warfare. Their hand-grenades were at first merely
tin cans filled with bits of iron and a high explosive in which a
fuse-cord was inserted. The cord was lighted by means of a cigarette
and then the can with its spluttering fuse was thrown into the enemy
lines. As time went on and the art of grenade fighting was learned, the
first crude missiles were greatly improved upon and grenades were made
in many forms for special service.

There was a difference between grenades hurled from sheltered positions
and those used in open fighting. When the throwers were sheltered
behind their own breastworks, it mattered not how powerful was the
explosion of the grenade. We must remember that in "hand-artillery" the
shell is far more powerful in proportion to the distance it is thrown
than the shell fired from a gun, and many grenades were so heavily
charged with explosives that they would scatter death and destruction
farther than they could be thrown by hand. The grenadier who cast one
of these grenades had to duck under cover or hide under the walls of
his trench, else the fragments scattered by the exploding missile might
fly back and injure him. Some grenades would spread destruction to a
distance of over three hundred feet from the point of explosion. For
close work, grenades of smaller radius were used. These were employed
to fight off a raiding-party after it had invaded a trench, and the
destructive range of these grenades was usually about twenty-five feet.

Hand-grenades came to be used in all the different ways that artillery
was used. There were grenades which were filled with gas, not only
of the suffocating and tear-producing types, but also of the deadly
poisonous variety. There were incendiary grenades which would set fire
to enemy stores, and smoke grenades which would produce a dense black
screen behind which operations could be concealed from the enemy.
Grenades were used in the same way that shrapnel was used to produce
a barrage or curtain of fire, through which the enemy could not pass
without facing almost certain death. Curtains of fire were used not
only for defensive purposes when the enemy was attacking, but also to
cut off a part of the enemy so that it could not receive assistance
and would be obliged to surrender. In attacks upon the enemy lines,
grenades were used to throw a barrage in advance of the attacking
soldiers so as to sweep the ground ahead clear of the enemy.

The French paid particular attention to the training of grenadiers. A
man had to be a good, cool-headed pitcher before he could be classed as
a grenadier. He must be able to throw his grenade with perfect accuracy
up to a distance of seventy yards, and to maintain an effective
barrage. The grenadier carried his grenades in large pockets attached
to his belt, and he was attended by a carrier who brought up grenades
to him in baskets, so that he was served with a continuous supply.


LONG-DISTANCE GRENADE-THROWING

All this relates to short-distance fighting, but grenades were also
used for ranges beyond the reach of the pitcher's arm. Even back in
the sixteenth century, the range of the human arm was not great enough
to satisfy the combatants and grenadiers used a throwing-implement,
something like a shovel, with which the grenade was slung to a greater
distance, in much the same way as a lacrosse ball is thrown. Later,
grenades were fitted with light, flexible wooden handles and were
thrown, handle and all, at the enemy. By this means they could be slung
to a considerable distance. Such grenades were used in the recent war,
particularly by the Germans. The handle was provided with streamers
so as to keep the grenade head-on to the enemy, and it was usually
exploded by percussion on striking its target. These long-handled
grenades, however, were clumsy and bulky, and the grenadier required a
good deal of elbow-room when throwing them.

[Illustration: FIG. 3. A rifle grenade fitted to the muzzle of a rifle]

A much better plan was to hurl them with the aid of a gun. A rifle made
an excellent short-distance mortar. With it grenades could be thrown
from three to four hundred yards. The grenade was fastened on a rod
which was inserted in the barrel of the rifle and then it was fired out
of the gun by the explosion of a blank cartridge. The butt of the rifle
was rested on the ground and the rifle was tilted so as to throw the
grenade up into the air in the way that a mortar projects its shell.


STRIKING A LIGHT

The lighting of the grenade fuses with a cigarette did very well
for the early tin-can grenades, but the cigarettes were not always
handy, particularly in the heat of battle, and something better had
to be devised. One scheme was to use a safety-match composition on
the end of a fuse. This was covered with waxed paper to protect it
from the weather. The grenadier wore an armlet covered with a friction
composition such as is used on a safety-match box. Before the grenade
was thrown, the waxed paper was stripped off and the fuse was lighted
by being scratched on the armlet. In another type the fuse was lighted
by the twisting of a cap which scratched a match composition on a
friction surface. A safety-pin kept the cap from turning until the
grenadier was ready to throw the grenade.

The Mills hand-grenade, which proved to be the most popular type used
by the British Army, was provided with a lever which was normally
strapped down and held by means of a safety-pin. Fig. 4 shows a
sectional view of this grenade. Just before the missile was thrown,
it was seized in the hand so that the lever was held down. Then the
safety-pin was removed and when the grenade was thrown, the lever would
spring up under pull of the spring _A_. This would cause the pin _B_
to strike the percussion cap _C_, which would light the fuse _D_. The
burning fuse would eventually carry the fire to the detonator _E_,
which would touch off the main explosive, shattering the shell of the
grenade and scattering its fragments in all directions. The shell of
the grenade was indented so that it would break easily into a great
many small pieces.

[Illustration: FIG. 4. Details of the Mills hand grenade]

There were some advantages in using grenades lighted by fuse instead
of percussion, and also there were many disadvantages. If too long a
time-fuse were used, the enemy might catch the grenade, as you would
a baseball and hurl it back before it exploded. This was a hazardous
game, but it was often done.

[Illustration: FIG. 5. A German parachute grenade]

Among the different types of grenades which the Germans used was
one provided with a parachute as shown in Fig. 5. The object of the
parachute was to keep the head of the grenade toward the enemy, so that
when it exploded it would expend its energies forward and would not
cast fragments back toward the man who had thrown it. This was a very
sensitive grenade, arranged to be fired by percussion, but it was so
easily exploded that the firing-mechanism was not released until after
the grenade had been thrown. In the handle of this grenade there was
a bit of cord about twenty feet long. One end of this was attached to
a safety-needle, _A_, while the other end, formed into a loop, was
held by the grenadier when he threw the grenade. Not until the missile
had reached a height of twelve or thirteen feet would the pull of the
string withdraw the needle _A_. This would permit a safety-hook, _B_,
to drop out of a ring, _C_, on the end of a striker pellet, _D_. When
the grenade struck, the pellet _D_ would move forward and a pin, _E_,
would strike a cap on the detonator _F_, exploding the missile. This
form of safety-device was used on a number of German grenades.

[Illustration: FIG. 6. British rifle grenade with a safety-device which
is unlocked by the rush of air against a set of inclined vanes, _D_,
when the missile is in flight]

The British had another scheme for locking the mechanism until after
the grenade had traveled some distance through the air. Details of this
grenade, which was of the type adopted to be fired from a rifle, are
shown in Fig. 6. The striker _A_ is retained by a couple of bolts, _B_,
which in turn are held in place by a sleeve, _C_. On the sleeve is a
set of wind-vanes, _D_. As the grenade travels through the air, the
wind-vanes cause the sleeve _C_ to revolve, screwing it down clear of
the bolts _B_, which then drop out, permitting the pin _A_ to strike
the detonator _E_ upon impact of the grenade with its target.

[Illustration: FIG. 7. Front, side, and sectional views of a
disk-shaped German grenade]

[Illustration: FIG. 8. A curious German hand grenade shaped like a hair
brush]

The Germans had one peculiar type which was in the shape of a disk. In
the disk were six tubes, four of which carried percussion caps so that
the grenade was sure to explode no matter on which tube it fell. The
disk was thrown with the edge up, and it would roll through the air.
Another type of grenade was known as the hair-brush grenade because it
had a rectangular body of tin about six inches long and two and three
quarter inches wide and deep, which was nailed to a wooden handle.


MINIATURE ARTILLERY

Hand-artillery was very effective as far as it went, but it had its
limitations. Grenades could not be made heavier than two pounds in
weight if they were to be thrown by hand; in fact, most of them were
much lighter than that. If they were fired from a rifle, the range was
increased but the missile could not be made very much heavier. TNT is
a very powerful explosive, but there is not room for much of it in a
grenade the size of a large lemon. Trench fighting was a duel between
forts, and while the hand-artillery provided a means of attacking the
defenders of a fort, it made no impression on the walls of the fort.
It corresponded to shrapnel fire on a miniature scale, and something
corresponding to high-explosive fire on a small scale was necessary
if the opposing fortifications were to be destroyed. To meet this
problem, men cast their thoughts back to the primitive artillery of
the Romans, who used to hurl great rocks at the enemy with catapults.
And the trench fighters actually rigged up catapults with which
they hurled heavy bombs at the enemy lines. All sorts of ingenious
catapults were built, some modeled after the old Roman machines. In
some of these stout timbers were used as springs, in others there were
powerful coil springs. It was not necessary to cast the bombs far. For
distant work the regular artillery could be used. What was needed was a
short-distance gun for heavy missiles and that is what the catapult was.

[Illustration: Press Illustrating Service

A 3-inch Stokes mortar and two of its shells]

[Illustration: Press Illustrating Service

Dropping a shell into a 6-inch trench mortar]

But the work of the catapult was not really satisfactory. The machine
was clumsy; it occupied too much space, and it could not be aimed very
accurately. It soon gave way to a more modern apparatus, fashioned
after the old smooth-bore mortars. This was a miniature mortar, short
and wide-mouthed. A rifled barrel was not required, because, since
the missile was not to be hurled far, it was not necessary to set it
spinning by means of rifling so as to hold it head-on to the wind.


GIANT PEA-SHOOTERS

Better aim was secured when a longer-barreled trench mortar came to
be used. In the trench, weight was an important item. There was no
room in which to handle heavy guns, and the mortar had to be portable
so that it could be carried forward by the infantry in a charge. As
the walls of a light barrel might be burst by the shock of exploding
powder, compressed air was used instead. The shell was virtually blown
out of the gun in the same way that a boy blows missiles out of a
pea-shooter. That the shell might be kept from tumbling, it was fitted
with vanes at the rear. These acted like the feathers of an arrow to
hold the missile head-on to its course.

[Illustration: Courtesy of "Scientific American"

The Maxim Machine-gun Operated by the Energy of the Recoil]

[Illustration: Courtesy of "Scientific American"

Colt Machine-gun partly broken away to show the Operating Mechanism

Gas from port _A_ pushes down piston _B_, rocking lever _C_, which
compresses coil-spring _D_. The cartridge fed into the gun by wheel
_E_, is extracted by _F_, raised by _G_ to breech _H_, and rammed in by
bolt _I_. _J_, piston firing-hammer.]

The French in particular used this type of mortar and the air-pump was
used to compress the air that propelled the shell or aërial torpedo,
or else the propelling charge was taken from a compressed-air tank.
Carbon-dioxide, the gas used in soda-water, is commonly stored in
tanks under high pressure and this gas was sometimes used in place
of compressed air. When the gas in the tank was exhausted the latter
could be recharged with air by using a hand-pump. Two or three hundred
strokes of the pump would give a pressure of one hundred and twenty to
one hundred and fifty pounds per inch, and would supply enough air to
discharge a number of shell. The air was let into the barrel of the
mortar in a single puff sufficient to launch the shell; then the tank
was cut off at once, so that the air it contained would not escape and
go to waste.


THE STOKES MORTAR

However, the most useful trench mortar developed during the war was
invented by Wilfred Stokes, a British inventor. In this a comparatively
slow-acting powder was used to propel the missile, and so a thin-walled
barrel could be used. The light Stokes mortar can easily be carried
over the shoulder by one man. It has two legs and the barrel itself
serves as a third leg, and the mortar stands like a tripod. The two
legs are adjustable, so that the barrel can be inclined to any desired
angle. It took but a moment to set up the mortar for action in a trench
or shell-hole.

[Illustration: FIG. 9. Sectional view of a 3-inch Stokes mortar showing
a shell at the instant of striking the anvil]

[Illustration: FIG. 10. A 6-inch trench mortar shell fitted with
tail-vanes]

Curiously enough, there is no breech-block, trigger or fire-hole in
this mortar. It is fired merely by the dropping of the missile into the
mouth of the barrel. The shell carries its own propelling charge, as
shown in Fig. 9. This is in the form of rings, _A_, which are fitted
on a stem, _B_. At the end of the stem are a detonating cap and a
cartridge, to ignite the propellant, _A_. At the bottom of the mortar
barrel, there is a steel point, _E_, known as the "anvil." When the
shell is dropped into the mortar, the cap strikes the anvil, exploding
the cartridge and touching off the propelling charge, _A_. The gases
formed by the burning charge hurl the shell out of the barrel to a
distance of several hundred yards.

The first Stokes mortar was made to fire a 3-inch shell, but the mortar
grew in size until it could hurl shell of 6-inch and even 8-1/2-inch
size. Of course, the larger mortars had to have a very substantial
base. They were not so readily portable as the smaller ones and they
could not be carried by one man; but compared with ordinary artillery
of the same bore they were immeasurably lighter and could be brought to
advanced positions and set up in a very short time. The larger shell
have tail-vanes, as shown in Fig. 10, to keep them from tumbling when
in flight.



CHAPTER III

GUNS THAT FIRE THEMSELVES


Many years ago a boy tried his hand at firing a United States Army
service rifle. It was a heavy rifle of the Civil War period, and the
lad did not know just how to hold it. He let the butt of the gun rest
uncertainly against him, instead of pressing it firmly to his shoulder,
and, in consequence, when the gun went off he received a powerful kick.

That kick made a deep impression on the lad, not only on his flesh but
on his mind as well. It gave him a good conception of the power of a
rifle cartridge.

Years afterward, when he had moved to England, the memory of that kick
was still with him. It was a useless prank of the gun, he thought, a
waste of good energy. Why could not the energy be put to use? And so he
set himself the task of harnessing the kick of the gun.

A very busy program he worked out for that kick to perform. He planned
to have the gun use up its exuberant energy in loading and firing
itself. So he arranged the cartridges on a belt and fed the belt into
the gun. When the gun was fired, the recoil would unlock the breech,
take out the empty case of the cartridge just fired, select a fresh
cartridge from the belt, and cock the main spring; then the mechanism
would return, throwing the empty cartridge-case out of the gun,
pushing the new cartridge into the barrel, closing the breech, and
finally pulling the trigger. All this was to be done by the energy of
a single kick, in about one tenth of a second, and the gun would keep
on repeating the operation as long as the supply of cartridges was fed
to it. The new gun proved so successful that the inventor was knighted,
and became Sir Hiram Maxim.


A DOCTOR'S TEN-BARRELED GUN

But Maxim's was by no means the first machine-gun. During the Civil War
a Chicago physician brought out a very ingenious ten-barreled gun, the
barrels of which were fired one after the other by the turning of a
hand-crank. Although Dr. Gatling was a graduate of a medical school,
he was far more fond of tinkering with machinery than of doling out
pills. He invented a number of clever mechanisms, but the one that made
him really famous was that machine-gun. At first our government did
not take the invention seriously. The gun was tried out in the war,
but whenever it went into battle it was fired not by soldiers but by
a representative of Dr. Gatling's company, who went into the army to
demonstrate the worth of the invention. Not until long after was the
Gatling gun officially adopted by our army. Then it was taken up by
many of the European armies as well.

Although many other machine-guns were invented, the Gatling was
easily the best and most serviceable, until the Maxim invention made
its appearance, and even then it held its own for many years; but
eventually it had to succumb. The Maxim did not have to be cranked:
it fired itself, which was a distinct advantage; and then, instead of
being a bundle of guns all bound up into a single machine, Maxim's was
a single-barreled gun and hence was much lighter and could be handled
much more easily.


A GUN AS A GAS-ENGINE

Another big advance was made by a third American, Mr. John M. Browning,
who is responsible for the Colt gun. It was not a kick that set
Browning to thinking. He looked upon a gun as an engine of the same
order as an automobile engine, and really the resemblance is very
close. The barrel of the gun is the cylinder of the engine; the bullet
is the piston; and for fuel gunpowder is used in place of gasolene. As
in the automobile engine, the charge is fired by a spark; but in the
case of the gun the spark is produced by a blow of the trigger upon a
bit of fulminate of mercury in the end of the cartridge.

[Illustration: Courtesy of "Scientific American"

The Lewis Gun which produces its own cooling current]

[Illustration: Courtesy of "Scientific American"

The Benèt-Mercié Gun operated by gas]

Explosion is the same thing as burning. The only way that the explosion
of gunpowder differs from the burning of a stick of wood is that the
latter is very slow, while the former goes like a flash. In both cases
the fuel turns into great volumes of gas. In the case of the gun the
gas is formed almost instantly and in such quantity that it has to
drive the bullet out of the barrel to make room for itself. In the
cartridge that our army uses, only about a tenth of an ounce of
smokeless powder is used, but this builds up so heavy a pressure of gas
that the bullet is sent speeding out of the gun at a rate of half a
mile a second. It travels so fast that it will plow through four feet
of solid wood before coming to a stop.

[Illustration: (C) Committee on Public Information

Browning Machine Rifle, weight only 15 pounds]

[Illustration: (C) Committee on Public Information

Browning Machine-Gun, weighing 34-1/2 pounds]

Now it occurred to Browning that it wouldn't really be stealing to
take a little of that gas-power and use it to work the mechanism of
his machine-gun. It was ever so little he wanted, and the bullet would
never miss it. The danger was not that he might take too much. His
problem was to take any power at all without getting more than his
mechanism could stand. What he did was to bore a hole through the side
of the gun-barrel. When the gun was fired, nothing happened until the
bullet passed this hole; then some of the gas that was pushing the
bullet before it would blow out through the hole. But this would be a
very small amount indeed, for the instant that the bullet passed out of
the barrel the gases would rush out after it, the pressure in the gun
would drop, and the gas would stop blowing through the hole. With the
bullet traveling at the rate of about half a mile in a second, imagine
how short a space of time elapses after it passes the hole before
it emerges from the muzzle, and what a small amount of gas can pass
through the hole in that brief interval!

The gas that Browning got in this way he led into a second cylinder,
fitted with a piston. This piston was given a shove, and that gave a
lever a kick which set going the mechanism that extracted the empty
cartridge-case, inserted a fresh cartridge, and fired it.


GETTING RID OF HEAT

The resemblance of a machine-gun to a gasolene-engine can be
demonstrated still further. One of the most important parts of an
automobile engine is the cooling-system. The gasolene burning in the
cylinders would soon make them red-hot, were not some means provided
to carry off the heat. The same is true of a machine-gun. In fact,
the heat is one of the biggest problems that has to be dealt with. In
a gasolene-engine the heat is carried off in one of three ways: (1)
by passing water around the cylinders; (2) by building flanges around
the cylinders to carry the heat off into the air; and (3) by using a
fan to blow cool air against the cylinders. All of these schemes are
used in the machine-gun. In Dr. Gatling's gun the cooling-problem was
very simple. As there were ten barrels, one barrel could be cooling
while the rest were taking their turn in the firing. In other words,
each barrel received only a tenth of the heat that the whole gun was
producing; and yet Gatling found it advisable to surround the barrels
for about half their length with a water-jacket.

In the Maxim gun a water-jacket is used that extends the full length
of the barrel, and into this water-jacket seven and a half pints of
water are poured. Yet in a minute and a half of steady firing at a
moderate rate, or before six hundred rounds are discharged, the water
will be boiling. After that, with every thousand rounds of continuous
fire a pint and a half of water will be evaporated. Now the water
and the water-jacket add a great deal of weight to the gun, and this
Browning decided to do away with in his machine-gun. Instead of water
he used air to carry off the heat. The more surface the air touches,
the more heat will it carry away; and so the Colt gun was at first made
with a very thick-walled barrel. But later the Colt was formed with
flanges, like the flanges on a motor-cycle engine, so as to increase
the surface of the barrel. Of course, air-cooling is not so effective
as water-cooling, but it is claimed for this gun, and for other
machine-guns of the same class, that the barrel is sufficiently cooled
for ordinary service. Although a machine-gun may be capable of firing
many hundred shots per minute, it is seldom that such a rate is kept
up very long in battle. Usually, only a few rounds are fired at a time
and then there is a pause, and there is plenty of time for the barrel
to cool. Once in a while, however, the gun has to be fired continuously
for several minutes, and then the barrel grows exceedingly hot.


EFFECT OF OVERHEATING

But what if the gun-barrel does become hot? The real trouble is not
that the cartridge will explode prematurely, but that the barrel will
expand as it grows hot, so that the bullet will fit too loosely in the
bore. Inside the barrel the bore is rifled; that is, there are spiral
grooves in it which give a twist to the bullet as it passes through,
setting it spinning like a top. The spin of the bullet keeps its nose
pointing forward. If it were not for the rifling, the bullet would
tumble over and over, every which way, and it could not go very far
through the air, to say nothing of penetrating steel armor. To gain
the spinning-motion the bullet must fit into the barrel snugly enough
to squeeze into the spiral grooves. Now there is another American
machine-gun known as the Hotchkiss, which was used to a considerable
extent by the French Army. It is a gas-operated gun, something like the
Colt, and it is air-cooled. It was found in tests of the Hotchkiss gun
that in from three to four minutes of firing the barrel was expanded so
much that the shots began to be a little uncertain. In seven minutes of
continuous firing the barrel had grown so large that the rifling failed
to grip the bullet at all. The gun was no better than an old-fashioned
smooth-bore. The bullets would not travel more than three hundred
yards. It is because of this danger of overheating that the Colt and
the Hotchkiss guns are always furnished with a spare barrel. As soon as
a barrel gets hot it is uncoupled and the spare one is inserted in its
place. Our men are trained to change the barrel of a colt in the dark
in a quarter of a minute.

But a gun that has to have a spare barrel and that has to have its
barrel changed in the midst of a hot engagement is not an ideal weapon,
by any means. And this brings us to still another invention--that,
too, by an American. Colonel I. N. Lewis, of the United States Army,
conceived of a machine-gun that would be cooled not by still air but by
air in motion. This would do away with all the bother of water-jackets.
It would keep the gun light so that it could be operated by one man,
and yet it would not have to be supplied with a spare barrel.

Like the Colt and the Hotchkiss, the Lewis gun takes its power from the
gas that comes through a small port in the barrel, near the muzzle. In
the plate facing page 44 the port may be seen leading into a cylinder
that lies under the barrel. It takes about one ten-thousandth part of a
second for a bullet to pass out of the barrel after clearing the port,
but in that brief interval there is a puff of gas in the cylinder which
drives back a piston. This piston has teeth on it which engage a small
gear connected with a main-spring. When the piston moves back, it winds
the spring, and it is this spring that operates the mechanism of the
gun. The cartridges, instead of being taken from a belt or a clip, are
taken from a magazine that is round and flat. There are forty-seven
cartridges in the magazine and they are arranged like the spokes of
a wheel, but in two layers. As soon as forty-seven rounds have been
fired, the shooting must stop while a new magazine is inserted. But to
insert it takes only a couple of seconds.


USING THE BULLET TO FAN THE GUN

The most ingenious part of the Lewis gun is the cooling-system. On
the barrel of the gun are sixteen flanges or fins. These, instead of
running around the gun, run lengthwise of the barrel. They are very
light fins, being made of aluminum, and are surrounded by a casing of
the same metal. The casing is open at each end so that the air can flow
through it, but it extends beyond the muzzle of the barrel, and there
it is narrowed down. At the end of the barrel there is a mouthpiece so
shaped that the bullet, as it flies through, sucks a lot of air in its
wake, making a strong current flow through the sixteen channels formed
between the fins inside the casing. This air flows at the rate of about
seventy miles per hour, which is enough to carry off all the heat that
is generated by the firing of the cartridges. The gun may be regulated
to fire between 350 and 750 rounds per minute, and its total weight is
only 25-1/2 pounds.

[Illustration: Lewis Machine-guns in action at the front]

America can justly claim the honor of inventing and developing the
machine-gun, although Hiram Maxim did give up his American citizenship
and become a British subject. By the way, he is not to be confused with
his younger brother, Hudson Maxim, the inventor of high explosives,
who has always been an American to the core. Of course we must not get
the impression that only Americans have invented machine-guns. There
have been inventors of such weapons in various countries of Europe,
and even in Japan. Our own army for a while used a gun known as the
Benèt-Mercié, which is something like the Hotchkiss. This was invented
by L. V. Benèt, an American, and H. A. Mercié, a Frenchman, both living
in St. Denis, France.


THE BROWNING MACHINE-GUN

When we entered the war, it was expected that we would immediately
equip our forces with the Lewis gun, because the British and the
Belgians had found it an excellent weapon and also because it was
invented by an American officer, who very patriotically offered it
to our government without charging patent royalties. But the army
officials would not accept it, although many Lewis guns were bought by
the navy. This raised a storm of protest throughout the country until
finally it was learned that there was another gun for which the army
was waiting, which it was said would be the very best yet. The public
was skeptical and finally a test was arranged in Washington at which
the worth of the new gun was demonstrated.

[Illustration: Courtesy of "Scientific American"

An elaborate German Machine-Gun Fort]

It was a new Browning model; or, rather, there were two distinct
models. One of them, known as the heavy model, weighed only 34-1/2
pounds, this with its water-jacket filled; for it was a water-cooled
gun. Without its charge of water the machine weighed but 22-1/2 pounds
and could be rated as a very light machine-gun. However, it was classed
as a heavy gun and was operated from a tripod. The new machine used
recoil to operate its mechanism. The construction was simple, there
were few parts, and the gun could very quickly be taken apart in case
of breakage or disarrangement of the mechanism. But the greatest care
was exercised to prevent jamming of cartridges, which was one of the
principal defects in the other types of machine-guns. In the test this
new weapon fired twenty thousand shots at the rate of six hundred per
minute, with interruptions of only four and a half seconds, due partly
to defective cartridges.

There was no doubt that the new Browning was a remarkable weapon. But
if that could be said of the heavy gun, the light gun was a marvel. It
weighed only fifteen pounds and was light enough to be fired from the
shoulder or from the hip, while the operator was walking or running. In
fact, it was really a machine-rifle. The regular .30-caliber service
cartridges were used, and these were stored in a clip holding twenty
cartridges. The cartridges could be fired one at a time, or the entire
clip could be fired in two and a half seconds. It took but a second to
drop an empty clip out of the gun and replace it with a fresh one. The
rifle was gas-operated and air-cooled, but no special cooling-device
was supplied because it would seldom be necessary to fire a shoulder
rifle fast enough and long enough for the barrel to become overheated.

After the Browning machine-rifle was demonstrated it was realized that
the army had been perfectly justified in waiting for the new weapon.
Like the heavy Browning, the new rifle was a very simple mechanism,
with few parts which needed no special tools to take them apart or
reassemble them; a single small wrench served this purpose. Both the
heavy and the light gun were proof against mud, sand, and dust of
the battle-field. But best of all, a man did not have to have highly
specialized training before he could use the Browning rifle. It did
not require a crew to operate one of these guns. Each soldier could
have his own machine-gun and carry it in a charge as he would a rifle.
The advantage of the machine-rifle was that the operator could fire
as he ran, watching where the bullets struck the ground by noting the
dust they kicked up and in that way correcting his aim until he was on
the target. Very accurate shooting was thus made possible, and the
machine-rifle proved invaluable in the closing months of the war.

Browning is unquestionably the foremost inventor of firearms in the
world. He was born of Mormon parents, in Ogden, Utah, in 1854, and
his father had a gun shop. As a boy Browning became familiar with the
use of firearms and when he was but fourteen years of age he invented
an improved breech mechanism which was later used in the Winchester
repeater. Curiously enough, it was a Browning pistol that was used
by the assassin at Serajevo who killed the Archduke of Austria and
precipitated the great European war, and it was with the Browning
machine-gun and rifle that our boys swept the Germans back through the
Argonne Forest and helped to bring the war to a successful end.


THE MACHINE-GUN IN SERVICE

Although the machine-gun has been used ever since the Civil War, it was
not a vital factor in warfare until the recent great conflict. Army
officials were very slow to take it up, because they did not understand
it. They used to think of it as an inferior piece of light artillery,
instead of a superior rifle. The Gatling was so heavy that it had to
be mounted on wheels, and naturally it was thought of as a cannon. In
the Franco-Prussian War the French had a machine-gun by which they
set great store. It was called a _mitrailleuse_, or a gun for firing
grape-shot. It was something like the Gatling. The French counted on
this machine to surprise and overwhelm the Germans. But they made the
mistake of considering it a piece of artillery and fired it from long
range, so that it did not have a chance to show its worth. Only on one
or two occasions was it used at close range, and then it did frightful
execution. However, it was a very unsatisfactory machine, and kept
getting out of order. It earned the contempt of the Germans, and later
when the Maxim gun was offered to the German Army they would have none
of it. They did not want to bother with "a toy cannon."

It really was not until the war between Russia and Japan that military
men began to realize the value of the machine-gun. As the war went on,
both the Russians and the Japanese bought up all the machine-guns they
could secure. They learned what could be done with the aid of barbed
wire to retard the enemy while the machine-guns mowed them down as they
were trying to get through.

A man with a machine-gun is worth a hundred men with rifles; such is
the military estimate of the weapon. The gun fires so fast that after
hitting a man it will hit him again ten times while he is falling to
the ground. And so it does not pay to fire the gun continuously in one
direction, unless there is a dense mass of troops charging upon it.
Usually the machine-gun is swept from side to side so as to cover as
wide a range as possible. It is played upon the enemy as you would play
the hose upon the lawn, scattering a shower of lead among the advancing
hosts.


MACHINE-GUN FORTS

It used to be thought that the Belgian forts of armored steel and
concrete, almost completely buried in the ground, would hold out
against any artillery. But when the Germans brought up their great
howitzers and hurled undreamed-of quantities of high explosives on
these forts, they broke and crumbled to pieces. Then it was predicted
that the day of the fort was over. But the machine-gun developed a new
type of warfare. Instead of great forts, mounting huge guns, little
machine-gun forts were built, and, they were far more troublesome than
the big fellows.

To the Germans belongs the credit for the new type of fort, which
consisted of a small concrete structure, hidden from view as far
as possible, but commanding some important part of the front.
"Pill-boxes," the British call them, because the first ones they ran
across were round in shape and something like a pill-box in appearance.
These pill-boxes were just large enough to house a few men and a
couple of machine-guns. Concealment was of the utmost importance;
safety depended upon it. Airplanes were particularly feared, because a
machine-gun emplacement was recognized to be so important that a whole
battery of artillery would be turned upon a suspected pill-box.

Some of the German machine-gun forts were very elaborate, consisting
of spacious underground chambers where a large garrison of gunners
could live. These forts were known as _Mebus_, a word made from the
initials of "_Maschinengewehr Eisen-Bettungs Unterstand_," meaning a
machine-gun iron-bedded foundation.

It was the machine-gun that was responsible for the enormous
expenditure of ammunition in the war. Before a body of troops dared
to make a charge, the ground had to be thoroughly searched by the big
guns for any machine-gun nests. Unless these were found and destroyed
by shell-fire, the only way that remained to get the best of them was
to crush them down with tanks. It was really the machine-gun that drove
the armies into trenches and under the ground.

[Illustration: Comparative diagram of the path of a projectile from the
German Super-gun]

But a machine-gun did not have to be housed in a fort, particularly
a light gun of the Lewis type. To be sure, the Lewis gun is a little
heavy to be used as a rifle, but it could easily be managed with a rest
for the muzzle in the crotch of a tree, and a strong man could actually
fire the piece from the shoulder. The light machine-gun could go right
along with a charging body of troops and do very efficient service,
particularly in fighting in a town or village, but it had to be kept
moving or it would be a target for the artillery. In a certain village
fight a machine-gunner kept changing his position. He would fire for
a few minutes from one building and then shift over to some other. He
did this no less than six times, never staying more than five minutes
at a time in the same spot. But each one of the houses was shelled
within fifteen minutes of the time he opened fire from it, which shows
the importance that the Germans attached to machine-gun fire.

[Illustration: Courtesy of "Scientific American"

One of our 16-inch Coast Defence Guns on a disappearing mount]

[Illustration: Height of gun as compared with the New York City Hall]



CHAPTER IV

GUNS AND SUPER-GUNS


When the news came that big shells were dropping into Paris from a gun
which must be at least seventy miles away, the world at first refused
to believe; then it imagined that some brand-new form of gun or shell
or powder had been invented by the Germans. However, while the public
marveled, ordnance experts were interested but not astonished. They
knew that it was perfectly feasible to build a gun that would hurl
a shell fifty, or seventy-five, or even a hundred miles, without
involving anything new in the science of gunnery.


SHOOTING AROUND THE EDGE OF THE EARTH

But if such ranges were known to be possible, why was no such
long-distance gun built before? Simply because none but the Germans
would ever think of shooting around the edge of the earth at a target
so far away that it would have to be as big as a whole city to be
hit at all. In a distance of seventy miles, the curve of the earth
is considerable. Paris is far below the horizon of a man standing at
St. Gobain, where the big German gun was located. And if a hole were
bored from St. Gobain straight to Paris, so that you could see the city
from the gun, it would pass, midway of its course, three thousand,
seven hundred and fifty feet below the surface of the earth. With the
target so far off, it was impossible to aim at any particular fort,
ammunition depot, or other point of military importance. There is
always some uncertainty as to just where a shell will fall, due to
slight differences in quality and quantity of the powder used, in the
density of the air, the direction of the wind, etc. This variation is
bad enough when a shell is to be fired ten miles, but when the missile
has to travel seventy miles, it is out of the question to try to hit a
target that is not miles in extent.

Twenty years before the war our Ordnance Department had designed a
fifty-mile gun, but it was not built, because we could see no possible
use for it. Our big guns were built for fighting naval battles or for
the defense of our coasts from naval attacks, and there is certainly
no use in firing at a ship that is so far below the horizon that we
cannot even see the tips of its masts; and so our big guns, though
they were capable of firing a shell twenty-seven miles, if aimed high
enough, were usually mounted in carriages that would not let them shoot
more than twelve or fifteen miles.

The distance to which a shell can be hurled depends to a large extent
upon the angle of the gun. If the gun is tilted up to an angle of 15
degrees, the shell will go only about half as far as if it were tilted
up to 43-1/2 degrees, which is the angle that will carry a shell to
its greatest distance. If the long-range German gun was fired at that
angle, the shell must have risen to a height of about twenty-four miles.


BEYOND THE EARTH'S ATMOSPHERE

Most of the air that surrounds our globe lies within four miles of
the surface. Few airplanes can rise to a greater height than this,
because the air is so thin that it gives no support to the wings of
the machine. The greatest height to which a man has ever ascended is
seven miles. A balloon once carried two men to such a height. One
of them lost consciousness, and the other, who was nearly paralyzed,
succeeded in pulling the safety-valve rope, with his teeth. That
brought the balloon down, and their instruments showed that they had
gone up thirty-six thousand feet. What the ocean of air contains above
that elevation, we do not know, but judging by the way the atmosphere
thins out as we rise from the surface of the earth, we reckon that nine
tenths of the air lies within ten miles of the surface of the earth. At
twenty-four miles, or the top of the curve described by the shell of
the German long-range guns, there must be an almost complete vacuum.

If only we could accompany a shell on its course, we should find a
strange condition of affairs. The higher we rose, the darker would the
heavens become, until the sun would shine like a fiery ball in a black
sky. All around, the stars would twinkle, and below would be the glare
of light reflected from the earth's surface and its atmosphere, while
the cold would be far more intense than anything suffered on earth. Up
at that height, there would be nothing to indicate that the shell was
moving--no rush of air against the ears. We should seem detached from
earth and out in the endless reaches of space.

It seems absurd to think that a shell weighing close to a quarter
of a ton could be retarded appreciably by mere air. But when we
realize that the shell left the gun at the rate of over half a mile a
second--traveling about thirty times faster than an express-train--we
know that the air-pressure mounts up to a respectable figure. The
pressure is the same whether a shell is moving through the air or the
air is blowing against the shell. When the wind blows at the rate of
100 to 120 miles per hour, it is strong enough to lift houses off their
foundations, to wrench trees out of the ground, to pick up cattle and
carry them sailing through the air. Imagine what it would do if its
velocity were increased to 1,800 miles per hour. That is what the shell
of a big gun has to contend with. As most of the air lies near the
earth, the shell of long-range guns meet with less and less resistance
the higher they rise, until they get up into such thin air that there
is virtually no obstruction. The main trouble is to pierce the blanket
of heavy air that lies near the earth.


WAYS OF INCREASING THE RANGE

The big 16-inch guns that protect our coasts fire a shell that weighs
2,400 pounds. Nine hundred pounds of smokeless powder is used to propel
the shell, which leaves the muzzle of the gun with a speed of 2,600
feet per second. Now, the larger the diameter of the shell, the greater
will be its speed at the muzzle of the gun, because there will be a
greater surface for the powder gases to press against. On the other
hand, the larger the shell, the more will it be retarded by the air,
because there will be a larger surface for the air to press against.
It has been proposed by some ordnance experts that a shell might be
provided with a disk at each end, which would make it fit a gun of
larger caliber. A 10-inch shell, for instance, could then be fired from
a 16-inch gun. Being lighter than the 16-inch shell, it would leave the
muzzle of the gun at a higher speed. The disks could be so arranged
that as soon as the shell left the gun they would be thrown off, and
then the 10-inch shell, although starting with a higher velocity than a
16-inch shell, would offer less resistance to the air. In that way it
could be made to cover a much greater range. By the way, the shell of
the German long-range gun was of but 8.2-inch caliber.

Another way of increasing the range is to lengthen the gun. Right here
we must become acquainted with the word "caliber." Caliber means the
diameter of the shell. A 16-inch gun, for instance, fires a shell of
16-inch caliber; but when we read that the gun is a 40-or 50-caliber
gun, it means that the length of the gun is forty or fifty times the
diameter of the shell. Our biggest coast-defense guns are 50-caliber
16-inch guns, which means that they are fifty times 16 inches long, or
66-2/3 feet in length. When a gun is as long as that, care has to be
taken to prevent it from sagging at the muzzle of its own weight. These
guns actually do sag a little, and when the shell is fired through the
long barrel it straightens up the gun, making the muzzle "whip" upward,
just as a drooping garden hose does when the water shoots through it.

[Illustration: Courtesy of "Scientific American"

The 121-Mile Gun designed by American Ordnance Officers]

Now the longer the caliber length of a gun, the farther it will send
a shell, because the powder gases will have a longer time to push the
shell. But we cannot lengthen our big guns much more without using
some special support for the muzzle end of the gun, to keep it from
"whipping" too much. It is likely that the long-range German gun was
provided with a substantial support at the muzzle to keep it from
sagging.

[Illustration: (C) Underwood & Underwood

American 16-Inch Rifle on a Railway Mount]

Every once in a while a man comes forth with a "new idea" for
increasing the range. One plan is to increase the powder-pressure. We
have powders that will produce far more pressure than an ordinary gun
can stand. But we have to use powders that will burn comparatively
slowly. We do not want too sudden a shock to start with, but we wish
the powder to give off an enormous quantity of gas which will keep
on pushing and speeding up the shell until the latter emerges from
the muzzle. The fifty-mile gun that was proposed twenty years ago was
designed to stand a much higher pressure than is commonly used, and it
would have fired a 10-inch shell weighing 600 pounds with a velocity of
4,000 feet per second at the muzzle.

The Allies built no "super-guns," because they knew that they could
drop a far greater quantity of explosives with much greater accuracy
from airplanes, and at a much lower cost. The German gun at St. Gobain
was spectacular and it did some damage, but it had no military value
and it did not intimidate the French as the Germans had hoped it would.


A GUN WITH A RANGE OF A HUNDRED AND TWENTY MILES

But although we built no such gun, after the Germans began shelling
Paris our Ordnance Department designed a gun that would fire a shell to
a distance of over 120 miles! There was no intention of constructing
the gun, but the design was worked out just as if it were actually
to be built. It was to fire a shell of 10-inch caliber, weighing 400
pounds. Now, an Elswick standard 10-inch gun is 42 feet long and its
shell weighs 500 pounds. Two hundred pounds of powder are used to
propel the shell, which leaves the muzzle with a velocity of 3,000
feet per second. If the gun is elevated to the proper angle, it will
send the shell 25 miles, and it will take the shell a minute and
thirty-seven seconds to cover that distance. But the long-range gun our
ordnance experts designed would have to be charged with 1,440 pounds
of powder and the shell would leave the muzzle of the gun with a
velocity of 8,500 feet per second. It would be in the air four minutes
and nine seconds and would travel 121.3 miles. Were the gun fired from
the Aberdeen Proving Grounds, near Baltimore, Maryland, its shell would
travel across three states and fall into New York Bay at Perth Amboy.
At the top of its trajectory it would rise 46 miles above the earth.

But the most astonishing part of the design was the length of the gun,
which worked out to 225 feet. An enormous powder-chamber would have
to be used, so that the powder gases would keep speeding up the shell
until it reached the required velocity at the muzzle. The weight of the
barrel alone was estimated at 325 tons.

It would have to be built up in four sections screwed together and
because of its great length and weight it would have to be supported on
a steel truss. The gun would be mounted like a roller lift-bridge with
a heavy counter-weight at its lower end so that it could be elevated or
depressed at will and a powerful hydraulic jack would be required to
raise it.

The recoil of a big gun is always a most important matter. Unless a gun
can recoil, it will be smashed by the shock of the powder explosion.
Usually, heavy springs are used to take up the shock, or cylinders
filled with oil in which pistons slide. The pistons have small holes
in them through which the oil is forced as the piston moves and this
retards the gun in its recoil. But this "super-gun" was designed to
be mounted on a carriage running on a set of tracks laid in a long
concrete pit. On the recoil the gun would run back along the tracks,
and its motion would be retarded by friction blocks between the
carriage and the tracks and also by a steel cable attached to the
forward end of the carriage and running over a pulley on the front wall
of the pit, to a friction drum.

The engraving facing page 68 gives some idea of the enormous size of
the gun. Note the man at the breech of the gun. The hydraulic jack is
collapsible, so that the gun may be brought to the horizontal position
for loading, as shown by the dotted lines. The cost of building this
gun is estimated at two and a half million dollars and its 400-pound
shell would land only about sixty pounds of high explosives on the
target. A bombing-plane costing but thirty thousand dollars could land
twenty-five times as big a charge of high explosives with far greater
accuracy. Aside from this, the gun lining would soon wear out because
of the tremendous erosion of the powder gases.


THE THREE-SECOND LIFE OF A GUN

Powder gases are very hot indeed--hot enough to melt steel. The greater
the pressure in the gun, the hotter they are. It is only because
they pass through the gun so quickly, that they do not melt it. As a
matter of fact, they do wear it out rapidly because of their heat and
velocity. They say that the life of a big gun is only three seconds.
Of course, a shell passes through the gun in a very minute part of a
second, but if we add up these tiny periods until we have a total of
three seconds, during which the gun may have fired two hundred rounds,
we shall find that the lining of the barrel is so badly eroded that the
gun is unfit for accurate shooting, and it must go back to the shops
for a new inner tube.


ELASTIC GUNS

We had better go back with it and learn something about the manufacture
of a big gun. Guns used to be cast as a solid chunk of metal. Now
they are built up in layers. To understand why this is necessary, we
must realize that steel is not a dead mass, but is highly elastic--far
more elastic than rubber, although, of course, it does not stretch nor
compress so far. When a charge of powder is exploded in the barrel of a
gun, it expands in all directions. Of course, the projectile yields to
the pressure of the powder gases and is sent kiting out of the muzzle
of the gun. But for an instant before the shell starts to move, an
enormous force is exerted against the walls of the bore of the gun,
and, because steel is elastic, the barrel is expanded by this pressure,
and the bore is actually made larger for a moment, only to spring back
in the next instant. You can picture this action if you imagine a gun
made of rubber; as soon as the powder was fired, the rubber gun would
bulge out around the powder-chamber, only to collapse to its normal
size when the pressure was relieved by the discharge of the bullet.

Now, every elastic body has what is called its elastic limit. If you
take a coil spring, you can pull it out or you can compress it, and
it will always return to its original shape, unless you pull it out
or compress it beyond a certain point; that point is its elastic
limit. The same is true of a piece of steel: if you stretch it beyond
a certain point, it will not return to its original shape. When the
charge of powder in a cannon exceeds a certain amount, it stretches the
steel beyond its elastic limit, so that the bore becomes permanently
larger. Making the walls of the gun heavier would not prevent this,
because steel is so elastic that the inside of the walls expands beyond
its elastic limit before the outside is affected at all.

Years ago an American inventor named Treadwell worked out a scheme for
allowing the bore to expand more without exceeding its elastic limit.
He built up his gun in layers, and shrunk the outer layers upon the
inner layers, just as a blacksmith shrinks a tire on a wheel, so that
the inner tube of the gun would be squeezed, or compressed. When the
powder was fired, this inner layer could expand farther without danger,
because it was compressed to start with. The built-up gun was also
independently invented by a British inventor. All modern big guns are
built up.


HOW BIG GUNS ARE MADE

The inside tube, known as the lining, is cast roughly to shape, then
it is bored out, after which it is forged by the blows of a powerful
steam-hammer. Of course, while under the hammer, the tube is mounted on
a mandrel, or bar, that just fits the bore. The metal is then softened
in an annealing furnace, after which it is turned down to the proper
diameter and re-bored to the exact caliber. The diameter of the lining
is made three ten-thousandths of an inch larger than the inside of the
hoop or sleeve that fits over it. This sleeve, which is formed in the
same way, is heated up to 800 degrees, or until its inside diameter is
eight tenths of an inch larger than the outside diameter of the lining.
The lining is stood up on end and the sleeve is fitted over it. Then it
is cooled by means of water, so that it grips the lining and compresses
it. In this way, layer after layer is added until the gun is built up
to the proper size.

[Illustration: Photograph from Underwood & Underwood

A Long-distance Sub-calibered French Gun on a Railway Mount]

Instead of having a lining that is compressed by means of sleeves or
jackets, many big guns are wound with wire which is pulled so tight
as to compress the lining. The gun-tube is placed in a lathe, and
is turned so as to wind up the wire upon it. A heavy brake on the wire
keeps it drawn very tight. This wire, also, is put on in layers, so
that each layer can expand considerably without exceeding its elastic
limit. Our big 16-inch coast-defense guns are wound with wire that
is one tenth of an inch square. The length of wire on one gun is
sufficient to reach all the way from New York to Boston with fifty or
sixty miles of wire left over.

[Illustration: Courtesy of "Scientific American"

Inside of a Shrapnel Shell and Details of the Fuse Cap

Search-light Shell and one of its Candles]


GUNS THAT PLAY HIDE-AND-SEEK

A very ingenious invention is the disappearing-mount which is used
on our coast fortifications. By means of this a gun is hidden beyond
its breastworks so that it is absolutely invisible to the enemy. In
this sheltered position it is loaded and aimed. It is not necessary
to sight the gun on the target as you would sight a rifle. The aiming
is done mathematically. Off at some convenient observation post,
an observer gets the range of the target and telephones this range
to the plotting-room, where a rapid calculation is made as to how
much the gun should be elevated and swung to the right or the left.
This calculation is then sent on to the gunners, who adjust the
gun accordingly. When all is ready, the gun is raised by hydraulic
pressure, and just as it rises above the parapet it is automatically
fired. The recoil throws the gun back to its crouching position behind
the breastworks. All that the enemy sees, if anything, is the flash of
the discharge.

Now that airplanes have been invented, the disappearing-mount has lost
much of its usefulness. Big guns have to be hidden from above. They are
usually located behind a hill, five or six miles back of the trenches,
where the enemy cannot see them from the ground, and they are carefully
hidden under trees or a canopy of foliage or are disguised with paint.

The huge guns recently built to defend our coasts are intended to fire
a shell that will pierce the heavy armor of a modern dreadnought. The
shell is arranged to explode after it has penetrated the armor, and
the penetrating-power is a very important matter. About thirty years
ago the British built three battle-ships, each fitted with two guns
of 16-1/4-inch caliber and 30-caliber length. In order to test the
penetrating-power of this gun a target was built, consisting first of
twenty inches of steel armor and eight inches of wrought-iron; this
was backed by twenty feet of oak, five feet of granite, eleven feet
of concrete, and six feet of brick. When the shell struck this target
it passed through the steel, the iron, the oak, the granite, and the
concrete, and did not stop until it had penetrated three feet of the
brick. We have not subjected our 16-inch gun to such a test, but we
know that it would go through two such targets and still have plenty of
energy left. Incidentally, it costs us $1,680 each time the big gun is
fired.


THE FAMOUS FORTY-TWO-CENTIMETER GUN

One of the early surprises of the war was the huge gun used by the
Germans to destroy the powerful Belgian forts. Properly speaking,
this was not a gun, but a howitzer; and right here we must learn the
difference between mortars, howitzers, and guns. What we usually mean
by "gun" is a piece of long caliber which is designed to hurl its
shell with a flat trajectory. But long ago it was found advantageous
to throw a projectile not at but upon a fortification, and for this
purpose short pieces of large bore were built. These would fire at a
high angle, so that the projectile would fall almost vertically on the
target.

As we have said, the bore of a gun is rifled; that is, it is provided
with spiral grooves that will set the shell spinning, so as to keep
its nose pointing in the direction of its flight. Mortars, on the
other hand, were originally intended for short-range firing, and their
bore was not rifled. In recent years, however, mortars have been made
longer and with rifled bores, so as to increase their range, and such
long mortars are called "howitzers." The German 42-centimeter howitzer
fired a shell that was 2,108 pounds in weight and was about 1-1/2 yards
long. The diameter of the shell was 42 centimeters, which is about
16-1/2 inches. It carried an enormous amount of high explosive, which
was designed to go off after the shell had penetrated its target. The
marvel of this howitzer was not that it could fire so big a shell
but that so large a piece of artillery could be transported over the
highroads and be set for use in battle. But although the 42-centimeter
gun was widely advertised, the real work of smashing the Belgian forts
was done by the Austrian "Skoda" howitzers, which fired a shell of
30.5-centimeter (12-inch) caliber, and not by the 42-centimeter gun.
The Skoda howitzer could be taken apart and transported by three
motor-cars of 100 horse-power each. The cars traveled at a rate of
about twelve miles per hour. It is claimed the gun could be put
together in twenty-four minutes, and would fire at the rate of one shot
per minute.


FIELD-GUNS

So far, we have talked only of the big guns, but in a modern battle
the field-gun plays a very important part. This fires a shell that
weighs between fourteen and eighteen pounds and is about three inches
in diameter. The shell and the powder that fires it are contained in a
cartridge that is just like the cartridge of a shoulder rifle. These
field-pieces are built to be fired rapidly. The French 75-millimeter
gun, which is considered one of the best, will fire at the rate of
twenty shots per minute, and its effective range is considerably over
three miles. The French supplied us with all 75-millimeter guns we
needed in the war, while we concentrated our efforts on the manufacture
of ammunition.


GUNS THAT FIRE GUNS

During the War of the Revolution, cannon were fired at short range, and
it was the custom to load them with grape-shot, or small iron balls,
when firing against a charging enemy, because the grape would scatter
like the shot of a shot-gun and tear a bigger gap in the ranks of the
enemy than would a single solid cannon-ball. In modern warfare, guns
are fired from a greater distance, so that there will be little danger
of their capture. It is impossible for them to fire grape, because
the ranges are far too great; besides, it would be impossible to aim
a charge of grape-shot over any considerable distance, because the
shot would start spreading as soon as they left the muzzle of the gun
and would scatter too far and wide to be of much service. But this
difficulty has been overcome by the making of a shell which is really a
gun in itself. Within this shell is the grape-shot, which consists of
two hundred and fifty half-inch balls of lead. The shell is fired over
the lines of the enemy, and just at the right moment it explodes and
scatters a hail of leaden balls over a fairly wide area.

It is not a simple matter to time a shrapnel shell so that it will
explode at just the right moment. Spring-driven clockwork has been
tried, which would explode a cap after the lapse of a certain amount
of time; but this way of timing shells has not proved satisfactory.
Nowadays a train of gunpowder is used. When the shell is fired, the
shock makes a cap (see drawing facing page 77) strike a pin, _E_, which
ignites the train of powder, _A_. The head of the shell is made of two
parts, in each of which there is a powder-fuse. There is a vent, or
short cut, leading from one fuse to the other, and, by the turning of
one part of the fuse-head with respect to the other, this short cut
is made to carry the train of fire from the upper to the lower fuse
sooner or later, according to the adjustment. The fire burns along
one powder-train _A_, and then jumps through the short cut _B_ to the
other, or movable train, as it is called, until it finally reaches,
through hole _C_, the main charge _F_, in the shell. The movable part
of the fuse-head is graduated so that the fuse may be set to explode
the shell at any desired distance. In the fuse-head there is also a
detonating-pin _K_, which will strike the primer _L_ and explode the
shell when the latter strikes the ground, if the time-fuse has failed
to act.

When attacking airplanes, it is important to be able to follow the
flight of the shell, so some shrapnel shell are provided with a
smoke-producing mixture, which is set on fire when the shell is
discharged, so as to produce a trail of smoke.

[Illustration: (C) Committee on Public Information

Putting on the Gas Masks to Meet a Gas Cloud Attack]

In meeting the attack of any enemy at night, search-light shell are
sometimes used. On exploding they discharge a number of "candles,"
each provided with a tiny parachute that lets the candle drop
slowly to the ground. Their brilliant light lasts fifteen or twenty
minutes. Obviously, ordinary search-lights could not be used on the
battle-field, because the lamp would at once be a target for enemy
batteries, but with search-light shell the gun that fires them can
remain hidden and one's own lines be shrouded in darkness while the
enemy lines are brilliantly illuminated.



CHAPTER V

THE BATTLE OF THE CHEMISTS


Some years ago the nations of the world gathered at the city of The
Hague, in Holland, to see what could be done to put an end to war.
They did not accomplish much in that direction, but they did draw up
certain rules of warfare which they agreed to abide by. There were some
practices which were considered too horrible for any civilized nation
to indulge in. Among these was the use of poisonous gases, and Germany
was one of the nations that took a solemn pledge not to use gas in war.

[Illustration: (C) Kadel & Herbert

Even the Horses had to be Masked]

[Illustration: Photograph by Kadel & Herbert

Portable Flame-throwing Apparatus]

Eighteen years later the German Army had dug itself into a line of
trenches reaching from the English Channel to Switzerland, and facing
them in another line of trenches were the armies of France and England,
determined to hold back the invaders. Neither side could make an
advance without frightful loss of life. But a German scientist came
forth with a scheme for breaking the dead-lock. This was Professor
Nernst, the inventor of a well-known electric lamp and a man who had
always violently hated the British. His plan was to drown out the
British with a flood of poisonous gas. To be sure, there was the pledge
taken at The Hague Conference, but why should that stand in Germany's
way? What cared the Germans for promises now? Already they had broken
a pledge in their violation of Belgium. Already they had rained
explosives from the sky on unfortified British cities (thus violating
another pledge of The Hague Conference); already they had determined to
war on defenseless merchantmen. To them promises meant nothing, if such
promises interfered with the success of German arms. They led the world
in the field of chemistry; why, they reasoned, shouldn't they make use
of this advantage?


POURING GAS LIKE WATER

It was really a new mode of warfare that the Germans were about to
launch and it called for much study. In the first place, they had to
decide what sort of gas to use. It must be a gas that could be obtained
in large quantities. It must be a very poisonous gas, that would act
quickly on the enemy; it must be easily compressed and liquefied so
that it could be carried in containers that were not too bulky; it must
vaporize when the pressure was released; and it must be heavier than
air, so that it would not be diluted by the atmosphere but would hug
the ground. You can pour gas just as you pour water, if it is heavier
than air. A heavy gas will stay in the bottom of an unstoppered bottle
and can be poured from one bottle into another like water. If the gas
is colored, you can see it flowing just as if it were a liquid. On the
other hand, a gas which is much lighter than air can also be kept in
unstoppered bottles if the bottles are turned upside down, and the gas
can be poured from one bottle into another; but it flows up instead of
down.

Chlorine gas was selected because it seemed to meet all requirements.
For the gas attack a point was chosen where the ground sloped gently
toward the opposing lines, so that the gas would actually flow down
hill into them. Preparations were carried out with the utmost secrecy.
Just under the parapet of the trenches deep pits were dug, about a
yard apart on a front of fifteen miles, or over twenty-five thousand
pits. In these pits were placed the chlorine tanks, each weighing
about ninety pounds. Each pit was then closed with a plank and this
was covered with a quilt filled with peat moss soaked in potash, so
that in case of any leakage the chlorine would be taken up by the
potash and rendered harmless. Over the quilts sandbags were piled to a
considerable height, to protect the tanks from shell-fragments.

Liquid chlorine will boil even in a temperature of 28 degrees below
zero Fahrenheit, but in tanks it cannot boil because there is no room
for it to turn into a gas. Upon release of the pressure at ordinary
temperatures, the liquid boils violently and big clouds of gas are
produced. If the gas were tapped off from the top of the cylinder, it
would freeze on pouring out, because any liquid that turns into a gas
has to draw heat from its surroundings. The greater the expansion, the
more heat the gas absorbs, and in the case of the chlorine tanks, had
the nozzles been set in the top of the tank they would very quickly
have been crusted with frost and choked, stopping the flow.

But the Germans had anticipated this difficulty, and instead of
drawing off the gas from the top of the tank, they drew off the liquid
from the bottom in small leaden tubes which passed up through the
liquid in the tank and were kept as warm as the surrounding liquid.
In fact, it was not gas from the top of the tank, but liquid from the
bottom, that was streamed out and this did not turn into gas until it
had left the nozzle.


WAITING FOR THE WIND

Everything was ready for the attack on the British in April, 1915. A
point had been chosen where the British lines made a juncture with
the French. The Germans reckoned that a joint of this sort in the
opponent's lines would be a spot of weakness. Also, they had very
craftily picked out this particular spot because the French portion of
the line was manned by Turcos, or Algerians, who would be likely to
think there was something supernatural about a death-dealing cloud.
On the left of the Africans was a division of Canadians, but the main
brunt of the gas was designed to fall upon the Turcos. Several times
the attack was about to be made, but was abandoned because the wind
was not just right. The Germans wished to pick out a time when the
breeze was blowing steadily--not so fast as to scatter the gas, but yet
so fast that it would overtake men who attempted to run away from it.
It was not until April 22 that conditions were ideal, and then the new
mode of warfare was launched.

Just as had been expected, the Turcos were awe-struck when they saw,
coming out of the German trenches, volumes of greenish-yellow gas,
which rolled toward them, pouring down into shell-holes and flowing
over into the trenches as if it were a liquid. They were seized with
superstitious fear, particularly when the gas overcame numbers of them,
stifling them and leaving them gasping for breath. Immediately there
was a panic and they raced back, striving to out-speed the pursuing
cloud.

For a stretch of fifteen miles the Allied trenches were emptied,
and the Germans, who followed in the wake of the gas, met with no
opposition except in the sector held by the Canadians. Here, on
the fringe of the gas cloud, so determined a fight was put up that
the Germans faltered, and the brave Canadians held them until
reinforcements arrived and the gap in the line was closed.

The Germans themselves were new at the game or they could have made a
complete success of this surprise attack. Had they made the attack on
a broader front, nothing could have kept them from breaking through
to Calais. The valiant Canadians who struggled and fought without
protection in the stifling clouds of chlorine, were almost wiped out.
But many of them who were on the fringe of the cloud escaped by wetting
handkerchiefs, socks, or other pieces of cloth, and wrapping them
around their mouths and noses.

The world was horrified when it read of this German gas attack,
but there was no time to be lost. Immediately orders went out for
gas-masks, and in all parts of England, and of France as well, women
were busy sewing the masks. These were very simple affairs--merely
a pad of cotton soaked in washing-soda and arranged to be tied over
the mouth and nose. But when the next attack came, not long after the
first, the men were prepared in some measure for it, and again it
failed to bring the Germans the success they had counted upon.

One thing that the Germans had not counted upon was the fact that the
prevailing winds in Flanders blow from west to east. During the entire
summer and autumn of 1915, the winds refused to favor them, and no gas
attacks were staged from June to December. This gave the British a long
respite and enabled them not only to prepare better gas-masks, but also
to make plans to give the Hun a dose of his own medicine.

[Illustration: (C) Kadel & Herbert

Liquid Fire Streaming from Fixed Flame-throwing Apparatus]


WHEN THE WIND PLAYED A TRICK ON THE GERMANS

There were many disadvantages in the use of gas clouds, which developed
as the Germans gathered experience. The gas started from their own
lines in a very dense cloud, but the cloud grew thinner and thinner as
it traveled toward the enemy, and lost a great deal of its strength.
If the wind were higher than fifteen miles an hour, it would swirl the
gas around and dissipate it before it did much harm to the opposing
fighters. If the wind were light, there were other dangers. On one
occasion in 1916 a cloud of gas was released upon an Irish regiment.
The wind was rather fickle. It carried the gas toward the British
trenches, but before reaching them the cloud hesitated, the wind
veered around, and soon the gas began to pour back upon the German
lines. The Germans were entirely unprepared for this boomerang attack.
Many of the Huns had no gas-masks on, and those who had, found that the
masks were not in proper working-order. As a result of this whim of the
winds, eleven thousand Germans were killed.

[Illustration: Courtesy of "Scientific American"

Cleaning Up a Dugout with the "Fire Broom"]

While chlorine was the first gas used, it was evident that it was not
the only one that could be employed. British chemists had suspected
that the Germans would use phosgene, which was a much more deadly gas,
and in the long interval between June and December, 1915, masks were
constructed which would keep out not only the fumes of chlorine but
also the more poisonous phosgene. In one of their sorties the British
succeeded in capturing some valuable notes on gas attacks, belonging to
a German general, which showed that the Germans were actually preparing
to use phosgene. This deadly gas is more insidious in its action than
chlorine. The man who inhales phosgene may not know that he is gassed.
He may experience no ill effects, but hours afterward, particularly if
he has exercised in the meantime, he may suddenly fall dead, owing to
its paralyzing action on the heart.


FREEING THE BRITISH TRENCHES OF RATS

Phosgene was not used alone, but had to be mixed with chlorine, and the
deadly combination of the two destroyed all life for miles behind the
trenches. However, the British were ready for it. They had been drilled
to put on their masks in a few seconds' time, on the first warning of
a gas attack. When the clouds of chlorine and phosgene came over No
Man's Land, they were prepared, and, except for casualties among men
whose masks proved defective, the soldiers in the trenches came through
with very few losses. All animal life, however, was destroyed. This
was a blessing to the British Tommy, whose trenches had been overrun
with rats. The British had tried every known method to get rid of
these pests, and now, thanks to the Germans, their quarters were most
effectively fumigated with phosgene and every rat was killed. If only
the "cooties" could have been destroyed in the same way, the Germans
might have been forgiven many of their offenses.

The disadvantages in the use of gas clouds became increasingly
apparent. What was wanted was some method of placing the gas among the
opponents in concentrated form, without wasting any of it on its way
across from one line to the other. This led to the use of shell filled
with materials which would produce gas. There were many advantages in
these shell. They could be thrown exactly where it was desired that
they should fall, without the help of the fickle winds. When the shell
landed and burst, the full effect of its contents was expended upon
the enemy. A gas cloud would rise over a wood, but with shell the wood
could be filled with gas, which, once there, would lurk among the trees
for days. Chemicals could be used in shell which could not be used in a
cloud attack. The shell could be filled with a liquid, or even with a
solid, because when it burst the filling would be minutely pulverized.
And so German chemists were set to work devising all sorts of fiendish
schemes for poisoning, choking, or merely annoying their opponents.


GAS THAT MADE ONE WEEP

One of the novel shell the Germans used was known as the "tear-gas"
shell. This was filled with a liquid, the vapor of which was very
irritating to the eyes. The liquid vaporized very slowly and so its
effect would last a long time. However, the vapor did not permanently
injure the eyes; it merely filled them with tears to such an extent
that a soldier was unable to see and consequently was confused and
retarded in his work. The "tear-gas" shell were marked with a "T" by
the Germans and were known as "T-shell."

Another type of shell, known as the "K-shell," contained a very
poisonous liquid, the object of which was to destroy the enemy quickly.
The effect of this shell was felt at once, but it left no slow vapors
on the ground, and so it could be followed up almost immediately by an
attack. Later on, the Germans developed three types of gas shell--one
known as the "Green Cross," another as the "Yellow Cross," and the
third as the "Blue Cross." The Green Cross shell was filled with
diphosgene, or a particularly dangerous combination of phosgene in
liquid form, which would remain in pools on the ground or soak into the
ground and would vaporize when it became warm. Its vapors were deadly.
One had always to be on his guard against them. In the morning, when
the sun warmed the earth and vapors were seen to rise from the damp
soil, tests were made of the vapors to see whether it was mere water
vapor or diphosgene, before men were allowed to walk through it.

These vapors were heavier than air and would flow down into a trench,
filling every nook and cranny. If phosgene entered a trench by a direct
hit, the liquid would remain there for days, rendering that part of the
trench uninhabitable except by men in gas-masks. The infected part of
the trench, however, was cut off from the rest of the trench by means
of gas-locks. In other words, blankets were used to keep the gas out,
and usually two blankets were hung so that a man in passing from one
part of the trench to another could lift up the first blanket, pass
under it, and close it carefully behind him before opening the second
blanket which led into the portion of the trench that was not infected.

The Germans had all sorts of fiendish schemes for increasing the
discomfort of the Allies. For instance, to some of their diphosgene
shell they added a gas which caused intense vomiting.

The Yellow Cross shell was another fiendish invention of the Huns. It
was popularly known as "mustard gas" and was intended not to kill but
merely to discomfort the enemy. The gas had a peculiar penetrating
smell, something like garlic, and its fumes would burn the flesh
wherever it was exposed to them, producing great blisters and sores
that were most distressing. The material in the shell was a liquid
which was very hard to get rid of because it would vaporize so slowly.
On account of the persistence of this vapor, lasting as it did for
days, these gas shell were usually not fired by the Germans on lines
that they expected to attack immediately.


THE SNEEZING-SHELL

The Blue Cross shell was comparatively harmless, although very
annoying. It contained a solid which was atomized by the explosion of
the shell, and which, after it got into the nostrils, caused a violent
sneezing. The material, however, was not poisonous and did not produce
any casualties to speak of, although it was most unpleasant. A storm of
Blue Cross shell could be followed almost immediately by an attack,
because the effect of the shell would have been dissipated before
the attackers reached the enemy who were still suffering from the
irritation of their nostrils.


GAS-MASKS

As the different kinds of gas shell were developed, the gas-masks
were improved to meet them. In every attack there were "duds" or
unexploded shell, which the chemists of the Allies analyzed. Also, they
were constantly experimenting with new gases, themselves, and often
could anticipate the Germans. The Allies were better able to protect
themselves against gas attacks than the Germans, because there was a
scarcity of rubber in Germany for the manufacture of masks. When it was
found that phosgene was going to be used, the simple cotton-wad masks
had to give way to more elaborate affairs with chemicals that would
neutralize this deadly gas. And later when the mustard gas was used
which attacked the eyes, and the sneezing-gas that attacked the nose,
it was found necessary to cover the face completely, particularly the
eyes; and so helmets of rubber were constructed which were tightly
fitted around the neck under the coat collar. The inhaled air was
purified by passage through a box or can filled with chemicals and
charcoal made of various materials, such as cocoanut shells, peach
pits, horse-chestnuts, and the like. Because the Germans had no rubber
to spare, they were obliged to use leather, which made their masks
stiff and heavy.


GLASS THAT WILL NOT SHATTER

One of the greatest difficulties that had to be contended with was the
covering of the eyes. There was danger in the use of glass, because it
was liable to be cracked or broken, letting in the deadly fumes and
gassing the wearer. Experiments were made with celluloid and similar
materials, but the finest gas-masks produced in the war were those made
for our own soldiers, in which the goggles were of glass, built up in
layers, with a celluloid-like material between, which makes a tough
composition that will stand up against a very hard blow. Even if it
cracks, this glass will not shatter.

The glasses were apt to become coated on the inside with moisture
coming from the perspiration of the face, and some means had to be
provided for wiping them off. The French hit upon a clever scheme of
having the inhaled air strike the glasses in a jet which would dry off
the moisture and keep the glasses clear. Before this was done, the
masks were provided with little sponges on the end of a finger-piece,
with which the glasses could be wiped dry without taking the masks off.

But all this time, the Allies were not merely standing on the
defensive. No sooner had the Germans launched their first attack than
the British and French chemists began to pay back the Hun in kind.
More attention was paid to the shell than the cloud attack, and soon
gas shell began to rain upon the Germans. Not only were the German
shell copied, but new gases were tried. Gas shell were manufactured in
immense quantities.

Then America took a hand in the war and our chemists added their help,
while our factories turned out steady streams of shell. If Germany
wanted gas warfare, the Allies were determined that she should have it.
Our chemists were not afraid to be pitted against the German chemists
and the factories of the Allies were more than a match for those of
the Central Powers. When the Germans first started the use of gas,
apparently they counted only their own success, which they thought
would be immediate and overwhelming. They soon learned that they must
take what they gave. The Allies set them a pace that they could not
keep up with.

When the armistice brought the war to a sudden stop, the United States
alone was making each day two tons of gas for every mile of the
western front. If the war had continued, the Germans would have been
simply deluged. As it was, they were getting far more gas than they
could possibly produce in their own factories and they had plenty of
reason to regret their rash disregard of their contract at The Hague
Conference. One gas we were making was of the same order as mustard gas
but far more volatile, and had we had a chance to use it against the
Germans they would have found it very difficult to protect themselves
against its penetrating fumes.


BATTLING WITH LIQUID FIRE

Somewhat associated with gas warfare was another form of offensive
which was introduced with the purpose of breaking up the dead-lock
of trench warfare. A man could protect himself against gas by using
a suitable mask and clothing, but what could he do against fire? It
looked as if trench defenders would have to give up if attacked with
fire, and so, early in the war, the Germans devised apparatus for
shooting forth streams of liquid fire, and the Allies were not slow to
copy the idea.

The apparatus was either fixed or portable, but it was not often
that the fixed apparatus could be used to advantage, because at best
the range of the flame-thrower was limited and in few places were
the trenches near enough for flaming oil to be thrown across the
intervening gap. For this reason portable apparatus was chiefly used,
with which a man could send out a stream for from a hundred to a
hundred and fifty feet. On his back he carried the oil-tank, in the
upper part of which there was a charge of compressed air. A pipe led
from the tank to a nozzle which the man held in his hand, using it to
direct the spray.

There was some danger to the operator in handling a highly inflammable
oil. The blaze might flare back and burn him, particularly when he
was lighting the stream, and so a special way of setting fire to the
spray had to be devised. Of course, the value of the apparatus lay
in its power to shoot the stream as far as possible. The compressed
air would send the stream to a good distance, but after lighting, the
oil might be consumed before it reached the desired range. Some way
had to be found of igniting the oil stream far from the nozzle or as
near the limit of its range as possible. And so two nozzles were used,
one with a small opening so that it would send out a fine jet of long
range, while the main stream of oil issued from the second nozzle.
The first nozzle was movable with respect to the second and the two
streams could be regulated to come together at any desired distance
from the operator within the range of the apparatus. The fine stream
was ignited and carried the flame out to the main stream, setting fire
to it near the limit of its range. In this way a flare-back was avoided
and the oil blazed where the flame was needed. The same sort of double
nozzle was used on the stationary apparatus and because weight was not
a consideration, heavier apparatus was used which shot the stream to a
greater distance.

But flame-throwing apparatus had its drawbacks: there was always the
danger that the tank of highly inflammable oil might be burst open by a
shell or hand-grenade and its contents set on fire. The fixed apparatus
was buried under bags of sand, but the man who carried flame-throwing
apparatus on his back had to take his chances, not knowing at what
instant the oil he carried might be set ablaze, turning him into a
living, writhing, human torch. Because of this hazard, liquid fire did
not play a very important part in trench warfare; to set fire to the
spray at its source with a well directed hand-grenade was too easy.


THE "FIRE BROOM"

There were certain situations, however, in which liquid fire played a
very important part. After a line of trenches had been captured it was
difficult to clear out the enemy who lurked in dugouts and underground
passages. They would not surrender, and from their hidden recesses they
could pour out a deadly machine-gun fire. The only way of dislodging
them was to use the "fire broom." In other words, a stream of liquid
fire was poured into the dugout, burning out the men trapped in it.
If there were a second exit, they would come tumbling out in a hurry.
If not, they would be burned to death. After the first sweep of the
"broom," if there were any survivors, there would not be any fight left
in them, and they would be quick to surrender before being subjected to
a second dose of fire.



CHAPTER VI

TANKS


There is no race-horse that can keep up with an automobile, no deer
that can out-run a locomotive. A bicyclist can soon tire out the
hardiest of hounds. Why? Because animals run on legs, while machines
run on wheels.

As wheels are so much more speedy than legs, it seems odd that we do
not find this form of locomotion in nature. There are many animals that
owe their very existence to the fact that they can run fast. Why hasn't
nature put them on wheels so that when their enemy appears they can
roll away, sedately, instead of having to jerk their legs frantically
back and forth at the rate of a hundred strokes a minute?

But one thing we must not overlook. Our wheeled machines must have a
special road prepared for them, either a macadam highway or a steel
track. They are absolutely helpless when they are obliged to travel
over rough country. No wheeled vehicle can run through fields broken by
ditches and swampy spots, or over ground obstructed with boulders and
tree-stumps.

But it is not always possible or practicable to build a road for the
machines to travel upon, and it is necessary to have some sort of
self-propelled vehicle that can travel over all kinds of ground.

Some time ago a British inventor developed a machine with large wheels
on which were mounted the equivalent of feet. As the wheels revolved,
these feet would be planted firmly on the ground, one after the other,
and the machine would proceed step by step. It could travel over
comparatively rough ground, and could actually walk up a flight of
stairs. We have a very curious walking-machine in this country. It is
a big dredge provided with two broad feet and a "swivel chair." The
machine makes progress by alternately planting its feet on the ground,
lifting itself up, chair and all, pushing itself forward, and sitting
down again.

Although many other types of walking-machines have been patented,
none of them has amounted to very much. Clearly, nature hopelessly
outclasses us in this form of propulsion.

Years ago it occured to one ingenious man that if wheeled machines must
have tracks or roads for their wheels to run on, they might be allowed
to lay their own tracks. And so he arranged his track in the form of an
endless chain of plates that ran around the wheels of his machine. The
wheels merely rolled on this chain, and as they progressed, new links
of the track were laid down before them and the links they had passed
over were picked up behind them. A number of inventors worked on this
idea, but one man in particular, Benjamin Holt, of Peoria, Illinois,
brought the invention to a high state of perfection. He arranged a
series of wheels along the chain track, each carrying a share of the
load of the machine, and each mounted on springs so that it would
yield to any unevenness of the ground, just as a caterpillar conforms
itself to the hills and dales of the surface it creeps over. In fact,
the machine was called a "caterpillar" tractor because of its crawling
locomotion.

But it was no worm of a machine. In power it was a very elephant. It
could haul loads that would tax the strength of scores of horses.
Stumps and boulders were no obstacles in its path. Even ditches could
not bar its progress. The machine would waddle down one bank and up the
other without the slightest difficulty. It was easily steered; in fact,
it could turn around in its own length by traveling forward on one of
its chains, or traction-belts, and backward on the other. The machine
was particularly adapted to travel on soft or plowed ground, because
the broad traction-belts gave it a very wide bearing and spread its
weight over a large surface. It was set to work on large farms, hauling
gangs of plows and cultivators. Little did Mr. Holt think, as he
watched his powerful mechanical elephants at work on the vast Western
wheat-fields, that they, or rather their offspring, would some day play
a leading role in a war that would rack the whole world.

       *       *       *       *       *

But we are getting ahead of our story. To start at the very beginning,
we must go back to the time when the first savage warrior used a plank
of wood to protect himself from the rocks hurled by his enemy. This
was the start of the never-ending competition between arms and armor.
As the weapons of offense developed from stone to spear, to arrow, to
arquebus, the wooden plank developed into a shield of brass and then
of steel; and then, since a separate shield became too bothersome to
carry, it was converted into armor that the warrior could wear and so
have both hands free for battle. For every improvement in arms there
was a corresponding improvement in armor.

After gunpowder was invented, the idea of armor for men began to
wane, because no armor could be built strong enough to ward off the
rifle-bullet and at the same time light enough for a man to wear. The
struggle between arms and armor was then confined to the big guns and
the steel protection of forts and war-ships.

But not so long ago the machine-gun was invented, and this introduced
a new phase of warfare. Not more than one rifle-bullet in a thousand
finds its mark on the battle-field. The Boers in the battle of Colenso
established a record with one hit in six hundred shots. In the
excitement of battle men are too nervous to take careful aim and they
are apt to fire either too high or too low, so that the mortality is
not nearly so great as some would expect. But with the machine-gun
there is not this waste of ammunition, because it fires a stream of
bullets, the effect of which can readily be determined by the man who
operates the volley. The difference between the machine-gun fire and
rifle fire is something like the difference between hitting a tin
can with a stone or with a stream of water. It is no easy matter to
score a hit with the stone; but any one can train a garden hose on the
can, because he can see where the water is striking and move his hose
accordingly until he covers the desired spot. In the same way, with the
machine-gun, it is much easier to train the stream of bullets upon the
mark, and, having once found the mark, to hold the aim. That is one
reason why the destruction of a machine-gun is so tremendous; another,
of course, being that it will discharge so many more shots per minute
than the common rifle.

[Illustration: (C) Underwood & Underwood

British Tank Climbing out of a Trench at Cambrai]

In the Russo-Japanese War, the Russians played havoc with the attacking
Japanese at Port Arthur by using carefully concealed machine-guns,
and the German military attachés were quick to note the value of
the machine-gun. Secretely they manufactured large numbers of
machine-guns and established a special branch of service to handle
the guns, and they developed the science of using them with telling
effect. And so, when the recent great war suddenly broke out, they
surprised the world with the countless number of machine-guns they
possessed and the efficient use to which they put them. Thousands of
British soldiers in the early days of the war fell victims to these
death-dealing machines. Two or three men with a machine-gun could defy
several companies of soldiers, especially when the attackers had to cut
their way through barbed wire entanglements. It was clearly evident
that something must be done to defend the men against the machine-gun;
for to charge against it meant, simply, wholesale slaughter.

[Illustration: (C) Underwood & Underwood

Even Trees were no Barrier to the British Tank]

[Illustration: Press Illustrating Service

The German Tank was very heavy and cumbersome]

At first the only means of combating the machine-guns seemed to be
to destroy them with shell-fire; but they were carefully concealed,
and it was difficult to search them out. Only by long-continued
bombardment was it possible to destroy them and tear away the barbed
wire sufficiently to permit of a charge. Before an enemy position was
stormed it was subjected to the fire of thousands of guns of all
calibers for hours and even days.

But this resulted in notifying the enemy that a charge was ere long to
be attempted at a certain place, and he could assemble his reserves for
a counter-attack. Furthermore, the Germans learned to conceal their
machine-guns in dugouts twenty or thirty feet underground, where they
were safe from the fire of the big guns, and then, when the fire let
up, the weapons would be dragged up to the surface in time to mow down
the approaching infantry.

It was very clear that something would have to be done to combat the
machine-gun. If the necessary armor was too heavy for the men to carry,
it must carry itself. Armored automobiles were of no service at all,
because they could not possibly travel over the shell-pitted ground of
No Man's Land. The Russians tried a big steel shield mounted on wheels,
which a squad of soldiers would push ahead of them, but their plan
failed because the wheels would get stuck in shell-holes. A one-man
shield on wheels was tried by the British. Under its shelter a man
could steal up to the barbed wire and cut it and even crawl up to a
machine-gun emplacement and destroy it with a hand-grenade. But this
did not prove very successful, either, because the wheels did not take
kindly to the rough ground of the battle-field.

       *       *       *       *       *

And here is where we come back to Mr. Holt's mechanical elephants. Just
before the great war broke out, Belgium--poor unsuspecting Belgium--was
holding an agricultural exhibit. An American tractor was on exhibition.
It was the one developed by Mr. Holt, and its remarkable performances
gained for it a reputation that spread far and wide. Colonel E.
D. Swinton of the British Army heard of the peculiar machine, and
immediately realized the advantages of an armored tractor for battle
over torn ground. But in the first few months of the war that ensued,
this idea was forgotten, until the effectiveness of the machine-gun
and the necessity for overcoming it recalled the matter to his mind.
At his suggestion a caterpillar tractor was procured, and the military
engineers set themselves to the task of designing an armored body to
ride on the caterpillar-tractor belts. Of course the machine had to be
entirely re-designed. The tractor was built for hauling loads, and not
to climb out of deep shell-holes; but by running the traction-belts
over the entire body of the car, and running the forward part of the
tractor up at a sharp angle the engineers overcame that difficulty.

In war, absolute secrecy is essential to the success of any invention,
and the British engineers were determined to let no inkling of the new
armored automobiles reach the enemy. Different parts of the machines
were made in different factories, so that no one would have an idea of
what the whole would look like. At first the new machine was known as
a "land-cruiser" or "land-ship"; but it was feared that this very name
would give a clue to spies, and so any descriptive name was forbidden.
Many of the parts consisted of rolled steel plates which might readily
be used in building up vessels to hold water or gasolene; and to give
the impression that such vessels were being constructed the name "tank"
was adopted. The necessity of guarding even the name of the machines
was shown later, when rumors leaked out that the tanks were being built
to carry water over the desert regions of Mesopotamia and Egypt.
Another curious rumor was that the machines were snow-plows for use in
Russia. To give some semblance of truth to this story, the parts were
carefully labeled, "For Petrograd."

Probably never was a military secret so well guarded as this one, and
when, on September 15, 1916, the waddling steel tractors loomed up
out of the morning mists, the German fighters were taken completely
by surprise. Two days before, their airmen had noticed some peculiar
machines which they supposed were armored automobiles. They had no
idea, however, that such formidable monsters were about to descend upon
them.

The tanks proceeded leisurely over the shell-torn regions of No Man's
Land, wallowing down into shell-holes and clambering up out of them
with perfect ease. They straddled the trenches and paused to pour down
them streams of machine-gun bullets. Wire entanglements were nothing
to them; under their weight steel wire snapped like thread. The big
brutes marched up and down the lines of wire, treading them down into
the ground and clearing the way for the infantry. Even trees were no
barrier to these tanks. Of course they did not attack large ones, but
the smallish trees were simply broken down before their onslaughts.
As for concrete emplacements for machine-guns, the tanks merely rode
over them and crushed them. Those who attempted to defend themselves in
the ruins of buildings found that the tanks could plow right through
walls and bring them down in a shower of bricks and stone. There was no
stopping these monsters, and the Germans fled in consternation before
them.

There were two sizes of tanks. The larger ones aimed to destroy the
machine-gun emplacements, and they were fitted up with guns for firing
a shell. The smaller tanks, armed with machine-guns, devoted themselves
to fighting the infantry. British soldiers following in the wake of
the bullet-proof tank were protected from the shots of the enemy and
were ready to attack him with bayonets when the time was ripe. But the
tanks also furnished an indirect protection for the troops. It was not
necessary for the men to conceal themselves behind the big tractors.
Naturally, every Hun who stood his ground and fought, directed all
his fire upon the tanks, leaving the British infantry free to charge
virtually unmolested. The success of the tank was most pronounced.

In the meantime the French had been informed of the plans of their
allies, and they set to work on a different design of tractor. It
was not until six months later that their machines saw service. The
French design differed from the British mainly in having the tractor
belt confined to the wheels instead of running over the entire body
of the tank. It was more blunt than the British and was provided
at the forward end with a steel cutting-edge, which adapted it to
break its way through wire entanglements. At each end there are two
upward-turning skids which helped the tank to lift itself out of a
hole. The larger machines carried a regular 75-millimeter (3-inch)
field-gun, which is a very formidable weapon. They carried a crew of
one officer and seven men.

Life in a tank is far from pleasant. The heat and the noise of
machinery and guns are terrific. Naturally, ventilation is poor and the
fumes and gases that accumulate are most annoying, to say the least.
Sometimes the men were overcome by them. But war is war, and such
discomforts had to be endured.

But the tank possessed one serious defect which the Germans were not
slow to discover. Its armor was proof against machine-gun fire, but
it could not ward off the shells of field-guns, and it was such a
slow traveler that the enemy did not find it a very difficult task to
hit it with a rapid-fire gun if the gunner could see his target. And
so the Germans ordered up their guns to the front lines, where they
could score direct hits. Only light guns were used for this purpose,
especially those whose rifling was worn down by long service, because
long range was not necessary for tank fighting.

[Illustration: (C) Underwood & Underwood

The Speedy British "Whippet" Tank that can travel at a speed of twelve
miles per hour]

[Illustration: (C) Underwood & Underwood

The French High-Speed "Baby" Tank]

When the Germans began their final great drive, it was rumored that
they had built some monster tanks that were far more formidable than
anything the Allies had produced. Unlike the British, they used the
tanks not to lead the army but to follow and destroy small nests of
French and British that were left behind. When the French finally
did capture one of the German tanks, which had fallen into a quarry,
it proved to be a poor imitation. It was an ugly-looking affair,
very heavy and cumbersome. Owing to the scarcity of materials for
producing high-grade armor, it had to make up in thickness of plating
what it lacked in quality of steel. The tank was intended to carry a
crew of eighteen men and it fairly bristled with guns, but it could
not manoeuver as well as the British tank; for when some weeks later a
fleet of German tanks encountered a fleet of heavy British tanks, the
Hun machines were completely routed.

[Illustration: Courtesy of "Automotive Industries"

Section through our Mark VIII Tank showing the layout of the interior
with the locations of the most important parts in the fighting
compartment in the engine room]

It was then that the British sprang another surprise upon the Germans.
After the big fellows had done their work, a lot of baby tanks appeared
on the scene and chased the German infantry. These little tanks could
travel at a speed of twelve miles an hour, which is about as fast as an
ordinary man can run. "Whippets," the British called them, because they
were like the speedy little dogs of that name. They carried but two
men, one to guide the tank and the other to operate the machine-gun.
The French, too, built a light "mosquito" tank, which was even smaller
than the British tank, and fully as fast. It was with these machines,
which could dart about quickly on the battle-field and dodge the
shell of the field-guns, and which were immune to the fire of the
machine-gun, that the Allies were able to make progress against the
Germans.

When the Germans retired, they left behind them nests of machine-guns
to cover the withdrawal of their armies. These gunners were ordered to
fight to the very end. They looked for no mercy and expected no help.
Had it not been for the light tanks, it would have been well nigh
impossible to overcome these determined bodies of men without frightful
losses.

Since America invented the machine-gun and also barbed wire, and
since America furnished the inspiration for the tank with which to
trample down the wire entanglements and stamp out the machine-guns,
naturally people expected our army to come out with something better
than anything produced by our allies. We did turn out a number of
heavy machines patterned after the original British tank, with armor
that could stand up against heavy fire, and we also produced a small
and very speedy tank similar to the French "baby" tank, but before we
could put these into service the war ended. The tanks we did use so
effectively at St.-Mihiel and in the Argonne Forest were supplied by
the French.



CHAPTER VII

THE WAR IN THE AIR


We Americans are a peace-loving people, which is the very reason why we
went into the war. We had to help down the power that was disturbing
the peace of the world. We do not believe in conquests--at least of the
type that Germany tried to force--and yet there are certain conquests
that we do indulge in once in a while.

Eleven years before Germany undertook to conquer Europe two young
Americans made the greatest conquest that the world has ever seen. The
Wright brothers sailed up into the heavens and gained the mastery of
the air. They offered their conquest to the United States; but while
we accepted their offering with enthusiasm at first, we did not know
what to do with the new realm after we got it. There seemed to be no
particular use in flying. It was just a bit too risky to be pleasant
sport, and about all we could see in it was an exhibition for the
circus or the county fair.

Not so in Europe, however. Flying meant something over there--there
where the frontiers have ever bristled with big guns and strong
fortifications, and where huge military forces have slept on their
arms, never knowing what dreadful war the morning would bring forth.
The war-lovers hailed the airplane as a new instrument with which to
terrorize their neighbors; the peace-lovers saw in it another menace to
their homes; it gave them a new frontier to defend. And so the military
powers of Europe took up the airplane seriously and earnestly and
developed it.

At first military authorities had rated the airplane chiefly as a
flying scout. Some bomb-dropping experiments had been made with it,
but it proved very difficult to land the bombs near the target, and,
besides, machines of those days were not built to carry very heavy
loads, so that it did not seem especially profitable to attack the
enemy from the skies. As for actual battles up among the clouds, they
were dreamed of only by the writers of fiction. But wild dreams became
stern realities in the mighty struggle between the great powers of the
world.


EYES IN THE SKY

As a scouting-machine the airplane did prove to be far superior to
mounted patrols which used to perform scout-work. In fact, it changed
completely the character of modern warfare. From his position high up
in the heavens the flying scout had an unobstructed view of the country
for miles and he could see just what the enemy was doing. He could see
whether large forces of men were collecting for an attack. He could
watch the course of supply-trains, and judge of their size. He could
locate the artillery of the enemy and come back with information which
in former times a scout posted in a tall tree or even in a captive
balloon could not begin to acquire. Surprise attacks were impossible,
with eyes in the sky. The aviator could help his own batteries by
signaling to them where to send their shell, and when the firing began
he would spot the shots as they landed and signal back to the battery
how to correct its aim so as to drop the shell squarely on the target.

The French sprang a surprise on the Germans by actually attacking the
infantry from the sky. The idea of attack from overhead was so novel
that armies did not realize the danger of exposing themselves behind
the battle-front. Long convoys of trucks and masses of infantry moved
freely over the roads behind the lines and they were taken by surprise
when the French began dropping steel darts upon them. These were about
the size of a pencil, with pointed end and fluted tail, so that they
would travel through the air like an arrow. The darts were dropped by
the hundred wherever the airmen saw a large group of the enemy, and
they struck with sufficient velocity to pierce a man from head to foot.
But steel darts were not used very long. The enemy took to cover and
then the only way to attack him was to drop explosives which would blow
up his shelter.

At the outset, air scouts were more afraid of the enemy on the ground
than in the sky. The Germans had anti-aircraft guns that were fired
with accuracy and accounted for many Allied planes. In those days,
airplanes flew at comparatively low altitudes and they were well
within the reach of the enemy's guns. But it was not long before the
airplanes began to fight one another. Each side was very much annoyed
by the flying scouts of its opponents and after a number of pistol
duels in the sky the French began to arm their planes with machine-guns.

Two months after the war started the first airplane was sent crashing
to earth after a battle in the sky. The fight took place five thousand
feet above the earth, between a French and a German machine. The
German pilot was killed and the plane fell behind the French lines,
carrying with it a Prussian nobleman who died before he could be pulled
out of the wreckage. The war had been carried into the skies. But if
scouts were to fight one another, they could not pay much attention
to scouting and spotting and it began to be realized that there were
four distinct classes of work for the airplane to do--scouting,
artillery-spotting, battling, and bombing. Each called for special
training and its own type of machine. As air fighting grew more
specialized these classes were further subdivided, but we need not go
into such refinements.


AIR SCOUTS AND THEIR DANGERS

The scouting-airplane usually carried two men, one to drive the machine
and the other to make observations. The observer had to carry a camera,
to take photographs of what lay below, and he was usually equipped
with a wireless outfit, with which he could send important information
back to his own base. The camera was sometimes fitted with a stock
like that of a gun, so that it could be aimed from the shoulder. Some
small cameras were shaped so that they could be held in the hand like
a pistol and aimed over the side of the fuselage, or body, of the
airplane; but the best work was done with large cameras fitted with
telescopic lenses, or "telephoto" lenses, as they are called. Some of
these were built into the airplane, with the lens opening down through
the bottom of the fuselage.

[Illustration: (C) Underwood & Underwood

A Handley-Page Bombing Plane with One of its Wings Folded Back]

The scouting-airplane carried a machine-gun, not for attack, but for
defense. It had to be a quick climber and a good dodger, so that it
could escape from an attacking plane. Usually it did not have to go
very far into the enemy country, and it was provided with a large
wing-spread, so that if anything happened to the engine, it could
_volplane_, or glide back, to its own lines. As the scouting-planes
were large, they offered a big target to anti-aircraft guns, and so
the work of the air scout was to swoop down upon the enemy, when,
of course, the machine would be traveling at high velocity, because
it would have all the speed of falling added to that which its own
propeller gave it.

[Illustration: How an object dropped from the Woolworth Building would
increase its speed in falling]

It was really a very difficult matter to hit a rapidly moving airplane;
and even if it were hit, there were few spots in which it could be
mortally wounded. Hundreds of shots could go through the wings of an
airplane without impairing its flying in the least. The engine, too,
could be pretty well peppered with ordinary bullets without being
disabled. As for the men in the machine, they furnished small targets,
and even they could be hit in many places without being put entirely
out of business. And so the dangers of air scouting were not so great
as might at first be supposed.

One of the most vulnerable spots in the airplane was the gasolene-tank.
If that were punctured so that the fuel would run out, the airplane
would have to come to the ground. Worse still, the gasolene might take
fire and there was nothing the aviator dreaded more than fire. There
were occasions in which he had to choose between leaping to earth and
burning to death, and the former was usually preferred as a quicker and
less painful death. In some of the later machines the gasolene-tank
could be pitched overboard if it took fire, by the throwing of a lever,
and then the aviator could glide to earth in safety.


THE SELF-HEALING GASOLENE-TANK

One of the contributions which we made to military aëronautics was a
gasolene-tank that was puncture-proof. It was made of soft rubber with
a thin lining of copper. There are some very soft erasers on the market
through which you can pass a lead pencil and never find the hole after
it has passed through, because the rubber has closed in and healed
the wound. Such was the rubber used in the gasolene-tank. It could be
peppered with bullets and yet would not leak a drop of gasolene, unless
the bullet chanced to plow along the edge of the tank and open a long
gash.

The Germans used four different kinds of cartridges in their aircraft
guns. The first carried the ordinary bullet, a second type had for its
bullet a shell of German silver filled with a phosphor compound. This
was automatically ignited through a small opening in the base of the
shell when it was fired from the gun and it left a trail of smoke by
which the gunner could trace its course through the air and correct his
aim. At night the bright spot of light made by the burning compound
would serve the same purpose. Such a bullet, if it hit an ordinary
gasolene-tank, would set fire to its contents. The bullet would plow
through the tank and out at the opposite side and there, at its point
of exit, is where the gasolene would be set on fire. Such incendiary
bullets were repeatedly fired into or through the rubber tanks and the
hole would close behind the bullet, preventing the contents from taking
fire. The two other types of bullets referred to were an explosive
bullet or tiny shell which would explode on striking the target and
a perforating steel bullet which was intended to pierce armor or
penetrate into vital parts of an airplane engine.

Machines with which artillery-spotting was done were usually manned
by a pilot and an observer, so that the latter could devote his
entire attention to noting the fire of the guns and signaling ranges
without being hampered by having to drive the machine. These machines
were usually of the pusher type, so that the observer could have an
unobstructed view. They did not have to be fast machines. It was really
better for them to move slowly. Had it been possible for them to stop
altogether and hover over the spot that was being shelled, it would
have been a distinct advantage. That would have given the observer a
chance to note with better accuracy the fall of the shell. Like the
scout, the spotter had to be a fast climber, so that it could get out
of the range of enemy guns and run away from attacking planes.


GIANTS OF THE SKY

The largest war-planes were the bomb-dropping machines. They had to be
capable of carrying heavy loads of explosives. They were usually slow
machines, speed being sacrificed in carrying-capacity.

The Germans paid a great deal of attention to big bomb-dropping
machines, particularly after their Zeppelins proved a failure. Their
huge Gothas were built to make night raids on undefended cities. The
Italians and the British retaliated with machines that were even
larger. At first the French were inclined to let giant planes alone.
They did not care to conduct long-distance bombing-raids on German
cities because their own important cities were so near the battle-front
that the Germans could have done those places more harm than the French
could have inflicted. Later they built some giant machines, although
not so large as those of the Italians and the British.

The large triplane Capronis built by the Italians held a crew of
three men. They were armed with three guns and carried 2750 pounds of
explosives. That made a useful load of 4000 pounds. The machine was
driven by three engines with a total of 900 horse-power.

The big British plane was the Handley-Page, which had a wing-spread of
125 feet and could carry a useful load of three tons. These enormous
machines conducted their raids at night because they were comparatively
slow and could not defend themselves against speedy battle-planes. The
big Italian machines used "search-light" bombs to help them locate
important points on the ground beneath. These were brilliant magnesium
torches suspended from parachutes so that they would fall slowly and
give a broad illumination, while the airplane itself was shielded from
the light by the parachute.

But these giants were not the only bombing-machines. There were smaller
machines that operated over the enemy's battle-line and dropped bombs
on any suspicious object behind the enemy lines. These machines had to
be convoyed by fast battle-planes which fought off hostile airmen.


HOW FAST IS A HUNDRED AND FIFTY MILES PER HOUR?

In naval warfare the battle-ship is the biggest and heaviest ship
of the fleet, but in the air the battle-planes are the lightest
and the smallest of the lot. They are one-man machines, as a rule,
little fellows, but enormously speedy. Speed is such an important
factor in aërial warfare that there was a continuous struggle between
the opposing forces to produce the faster machine. Airplanes were
constantly growing speedier, until a speed of 150 miles per hour was
not an uncommon rate of travel. It is hard to imagine such a speed as
that, but we may gain some idea if we consider a falling object. The
observation platform of the Woolworth Building, in New York, is about
750 feet above the ground. If you should drop an object from this
platform you would start it on a journey that would grow increasingly
speedy, particularly as it neared the ground. By the time it had
dropped from the sixtieth story to the fifty-ninth it would have
attained a speed of nearly 20 miles per hour. (We are not making any
allowances for the resistance of the air and what it would do to check
the speed.) As it passed the fiftieth story it would be traveling as
fast as an express-train, or 60 miles per hour. It would finally reach
the ground with a speed equal to that of a fast battle-plane--150 miles
per hour.

The battle-plane was usually fitted with a single machine-gun that was
fixed to the airplane, so that it was brought to bear on the target
by aiming the entire machine. In this the plane was something like a
submarine, which must point its bow at its intended victim in order to
aim its torpedo. The operator of the battle-plane simply drove his
machine at the enemy and touched a button on his steering-lever to
start his machine-gun going.


SHOOTING THROUGH THE PROPELLER

Now, the fleetest machines and the most easily manoeuvered are those of
the tractor type, that is, the ones which have the propeller in front;
but having the propeller in front is a handicap for a single-seater
machine, for the gun has to be fired through the propeller and the
bullets are sure to hit the propeller-blades. Nevertheless the French
did fire right through the propeller, regardless of whether or not
the blades were hit; but at the point where they came in line with
the fire of the gun they were armored with steel, so that there was
no danger of their being cut by the bullets. It was calculated that
not more than one bullet in eighteen would strike the propeller-blade
and be deflected from its course, which was a very trifling loss;
nevertheless, it was a loss, and on this account a mechanism was
devised which would time the operations of the machine-gun so that the
shots would come only when the propeller-blades were clear of the line
of fire.

[Illustration: Machine-Gun mounted to Fire over the Blades of the
Propeller]

[Illustration: Courtesy of "Scientific American"

Mechanism for Firing Between the Blades of the Propeller

The cam _B_ on the propeller shaft lifts the rod _C_, rocking the angle
lever _D_ which moves the rod _E_ and operates the firing-piece _F_.
Firing may be stopped by means of lever _H_ and Bowden wire _G_. _I_ is
the ejection-tube for empty cartridges.]

[Illustration: It would take a Hundred Horses to Supply the Power for a
Small Airplane]

A cam placed on the propeller-shaft worked the trigger of the
machine-gun. This did not slow up the fire of the machine-gun. Quite
the contrary. We are apt to think of the fire of the machine-guns as
very rapid, but they usually fire only about five hundred rounds per
minute, while an airplane propeller will make something like twelve
hundred revolutions per minute. And so the mechanism was arranged to
pull the trigger only once for every two revolutions of the propeller.


FIGHTING AMONG THE CLOUDS

There was no service of the war that began to compare with that of
the sky fighter. He had to climb to enormous heights. Air battles
took place at elevations of twenty thousand feet. The higher the
battle-plane could climb, the better, because the man above had a
tremendous advantage. Clouds were both a haven and a menace to him.
At any moment an enemy plane might burst out of the clouds upon
him. He had to be ready to go through all the thrilling tricks of a
circus performer so as to dodge the other fellow and get a commanding
position. If he were getting the worst of it, he might feign death and
let his machine go tumbling and fluttering down for a thousand feet or
so, only to recover his equilibrium suddenly and dart away when the
enemy was thrown off his guard. He might escape into some friendly
cloud, but he dared not hide in it very long, lest he get lost.

It is a peculiar sensation that comes over an aviator when he is flying
through a thick mass of clouds. He is cut off from the rest of the
world. He can hear nothing but the terrific roar of his own motor and
the hurricane rush of the wind against his ears. He can see nothing but
the bluish fog of the clouds. He begins to lose all sense of direction.
His compass appears to swing violently to and fro, when really it is
his machine that is zig-zagging under his unsteady guidance. The more
he tries to steady it, the worse becomes the swing of the compass. As
he turns he banks his machine automatically, just as a bicyclist does
when rounding a corner. He does this unconsciously, and he may get
to spinning round and round, with his machine standing on its side.
In some cases aviators actually emerged from the clouds with their
machines upside down. To be sure, this was not an alarming position
for an experienced aviator; at the same time, it was not altogether a
safe one. A machine was sometimes broken by its operator's effort to
right it suddenly. And so while the clouds made handy shelters, they
were not always safe harbors.

To the battle-plane fell the task of clearing the air of the enemy. If
the enemy's battle-planes were disposed of, his bombing-planes, his
spotters, and his scouts could not operate, and he would be blind. And
so each side tried to beat out the other with speedier, more powerful,
and more numerous battle-planes. Fast double-seaters were built with
guns mounted so that they could turn in any direction.


THE FLYING TANK

The Germans actually built an armored battle-plane known as the flying
tank. It was a two-seater intended mainly for attacking infantry and
was provided with two machine-guns that pointed down through the floor
of the fuselage. A third gun mounted on a revolving wooden ring could
be used to fight off hostile planes. The bottom and sides of the
fuselage or body of the airplane from the gunner's cockpit forward
were sheathed with plates of steel armor. The machine was a rather
cumbersome craft and did not prove very successful. A flying tank was
brought down within the American lines just before the signing of the
armistice.


AMERICA'S HELP

Our own contribution to the war in the air was considerable, but we had
hardly started before the armistice brought the fighting to an end.
Before we entered the war we did not give the airplane any very serious
consideration. To be sure, we built a large number of airplanes for the
British, but they were not good enough to be sent to the front; they
were used merely as practice planes in the British training-schools. We
knew that we were hopelessly outclassed, but we did not care very much.
Then we stepped into the conflict.

"What can we do to help?" we asked our allies, and their answer gave us
a shock.

"Airplanes!" they cried. "Build us airplanes--thousands of them--so
that we can drive the enemy out of the air and blind his armies!"

It took us a while to recover from our surprise, and then we realized
why we had been asked to build airplanes. The reputation of the United
States as a manufacturer of machinery had spread throughout the world.
We Americans love to take hold of a machine and turn it out in big
quantities. Our allies were sure that we could turn out first-class
airplanes, and many of them, if we tried.

Congress made an appropriation of six hundred and forty million dollars
for aëronautics, and then things began to hum.


A BIRTHDAY PRESENT TO THE NATION

The heart of an airplane is its engine. We know a great deal about
gasolene-engines, especially automobile engines; but an airplane engine
is a very different thing. It must be tremendously powerful, and at the
same time extremely light. Every ounce of unnecessary weight must be
shaved off. It must be built with the precision of a watch; its vital
parts must be true to a ten-thousandth part of an inch. It takes a very
powerful horse to develop one horse-power for a considerable length
of time. It would take a hundred horses to supply the power for even
a small airplane, and they would weigh a hundred and twenty thousand
pounds. An airplane motor of the same power would weigh less than three
hundred pounds, which is a quarter of the weight of a single horse.
It was this powerful, yet most delicate, machine that we were called
upon to turn out by the thousand. There was no time to waste; a motor
must be designed that could be built in the American way, without any
tinkering or fussy hand-work.

Two of our best engineers met in a hotel in Washington on June 3,
1917, and worked for five days without once leaving their rooms. They
had before them all the airplane knowledge of our allies. American
engine-builders offered up their trade secrets. Everything was done
to make this motor worthy of America's reputation. There was a race
to have the motor finished by the Fourth of July. Sure enough, on
Independence Day the finished motor was there in Washington--the
"Liberty motor," a birthday present to the nation.

Of course that did not mean that we were ready at once to turn out
Liberty motors by the thousand. The engine had to undergo many tests
and a large number of alterations before it was perfectly satisfactory
and then special machinery had to be constructed before it could be
manufactured in quantity. It was Thanksgiving Day before the first
manufactured Liberty was turned out and even after that change upon
change was made in this little detail and that. It was not until a year
after we went to war that the engine began to be turned out in quantity.

There was nothing startlingly new about the engine. It was a composite
of a number of other engines, but it was designed to be turned out in
enormous quantities, and it was remarkably efficient. It weighed only
825 pounds and it developed over 420 horse-power. Some machines went
up as high as 485 horse-power. An airplane engine weighing less than 2
pounds per horse-power is wonderfully efficient. Of course the Liberty
was too heavy for a light battle-plane (a heavy machine, no matter how
powerful, cannot make sharp turns), but it was excellent for other
types of airplanes and large orders for Liberty engines were made by
our allies. Of course we made other engines as well, and the planes to
carry them. We built large Caproni and Handley-Page machines, and we
were developing some remarkably swift and powerful planes of our own
when the Germans thought it about time to stop fighting.


FLYING BOATS

So far we have said nothing about the seaplanes which were used in
large numbers to watch for submarines. These were big flying boats in
which speed was not a very important matter. One of the really big
machines we developed, but which was not finished until after the war,
was a giant with a 110-foot span and a body or hull 50 feet long.
During the war seaplanes carried wireless telephone apparatus with
which they could call to destroyers and submarine-chasers when they
spotted a submarine. They also carried bombs which they could drop on
U-boats, and even heavy guns with which they could fire shell.

A still later development are the giant planes of the N. C. type with a
wing-spread of 126 feet and driven by four Liberty motors. They carry a
useful load of four and a half tons.

[Illustration: (C) Underwood & Underwood

The Flying-tank--an Armored German Airplane designed for firing on
troops on the march]

Early in the war, large guns were mounted on airplanes, but the shock
of the recoil proved too much for the airplane to stand. However,
an American inventor produced a gun which had no recoil. This he
accomplished by using a double-end gun, which was fired from the
middle. The bullet or shell was shot out at the forward end of the
gun and a dummy charge of sand was shot out at the rear end. The sand
spread out and did no damage at a short distance from the gun, but care
had to be taken not to come too close. These non-recoil guns were made
in different sizes, to fire 1-1/2-inch to 3-inch shell.


THE AUTOMATIC SEAPLANE

Another interesting development was the target airplane used for the
training of aërial gunners. This was a small seaplane with a span of
only 18-1/2 feet, driven by a 12-horse-power motor, the whole machine
weighing but 175 pounds. This was sent up without a pilot and it would
fly at the rate of forty to fifty miles per hour until its supply of
gasolene gave out, when it would drop down into the sea. It afforded a
real target for gunners in practice machines.

[Illustration: (C) Underwood & Underwood

An N-C (Navy-Curtiss) Seaplane of the type that made the first flight
across the Atlantic]

Early in the war an American inventor proposed that seaplanes be
provided with torpedoes which they could launch at an enemy ship. The
seaplane would swoop down out of the sky to within a short distance of
the ship, drop its projectile, and fly off again, and the torpedo would
continue on its course until it blew up the vessel. It was urged that
a fleet of such seaplanes protected by a convoy of fast battle-planes
could invade the enemy harbors and destroys its powerful fleet. It
seemed like a rather wild idea, but the British actually built such
torpedo-planes and tested them. However, the German fleet surrendered
before it was necessary to blow it up in such fashion.


AIRPLANES AFTER THE WAR

With the war ended, all the Allied powers have large numbers of
airplanes on their hands and also large numbers of trained aviators.
Undoubtedly airplanes will continue to fill the skies in Europe and we
shall see more and more of them in this country. Even during the war
they were used for other purposes than fighting. There were ambulances
on wings--machines with the top of the fuselage removable so that a
patient on a stretcher could be placed inside. A French machine was
furnished with a complete hospital equipment for emergency treatment
and even for performing an operation in case of necessity. The flying
hospital could carry the patient back to the field or base hospital
after treatment.

Mail-carrying airplanes are already an old story. In Europe the big
bombing-machines are being used for passenger service between cities.
There is an air line between Paris and London. The airplanes carry from
a dozen to as many as fifty passengers on a single trip. In some cities
here, as well as abroad, the police are being trained to fly, so that
they can police the heavens when the public takes to wings. Evidently
the flying-era is here.



CHAPTER VIII

SHIPS THAT SAIL THE SKIES


Shortly after the Civil War broke out, Thaddeus S. C. Lowe, an
enthusiastic American aëronaut, conceived the idea of sending up scout
balloons to reconnoiter the position of the enemy. These balloons
were to be connected by telegraph wires with the ground, so that they
could direct the artillery fire. The idea was so novel to the military
authorities of that day that it was not received with favor. Balloons
were looked upon as freak inventions, entirely impracticable for the
stern realities of war; and as for telegraphing from a balloon, no one
had ever done that before.

[Illustration: (C) Underwood & Underwood

A big German Zeppelin that was forced to come down on French soil]

But this enthusiast was not to be daunted, and he made a direct appeal
to President Lincoln, offering to prove the practicability of this
means of scouting. So he took his balloon to Washington and made an
ascent from the grounds of the Smithsonian Institution, while the
President came out on the lawn south of the White House to watch the
demonstration. In order to test him, Mr. Lincoln took off his hat,
waved his handkerchief, and made other signals. Lowe observed each
act through his field-glasses and reported it to the President by
telegraph. Mr. Lincoln was so impressed by the demonstration that he
ordered the army to use the observation balloon, and so with some
reluctance the gas-bag was introduced into military service, Professor
Lowe being made chief aëronautic engineer. Under Lowe's direction the
observation balloons played an important part in the operations of the
Union Army.

[Illustration: Courtesy of "Scientific American"

Observation Car lowered from a Zeppelin sailing above the clouds]

On one occasion a young German military attaché begged the privilege
of making an ascent in the balloon. Permission was given and when
the German officer returned to earth he was wildly enthusiastic in
praise of this aërial observation post. He had had a splendid view
of the enemy and could watch operations through his field-glasses
which were of utmost importance. Realizing the military value of the
aircraft, he returned to Germany and urged military authorities to
provide themselves with captive balloons. This young officer was Count
Ferdinand von Zeppelin, who was destined later to become the most
famous aëronautic authority in the world and who lived to see Germany
equipped with a fleet of balloons which were self-propelling and could
travel over land and sea to spread German frightfulness into England.
He also lived to see the virtual failure of this type of war-machine
in the recent great conflict, and it was possibly because of his deep
disappointment at having his huge expensive airships bested by cheap
little airplanes that Count von Zeppelin died in March, 1917. However,
he was spared the humiliation of seeing a fleet of Zeppelins lose their
way in a fog and fall into France, one of them being captured before
it could be destroyed, so that all its secrets of construction were
learned by the French.


THE WEIGHT OF HYDROGEN

Before we describe the Zeppelin airships and the means by which they
were eventually overcome, we must know something about the principles
of balloons. Every one knows that balloons are kept up in the air by
means of a very light gas, but somehow the general public fails to
understand why the gas should hold it up. Some people have a notion
that there is something mysterious about hydrogen gas which makes it
resist the pull of gravity, and that the more hydrogen you crowd into
the balloon the more weight it will lift. But hydrogen has weight and
feels the pull of gravity just as air does, or water, or lead. The only
reason the balloon rises is because it weighs less than the air it
displaces. It is hard to think of air as having weight, but if we weigh
air, hydrogen, coal-gas, or any other gas, in a vacuum, it will tip
the scales just as a solid would. A thousand cubic feet of air weighs
80 pounds. In other words, the air in a room ten feet square with a
ceiling ten feet high, weighs just about 80 pounds. The same amount of
coal-gas weighed in a vacuum would register only 40 pounds; while an
equal volume of hydrogen would weigh only 5-1/2 pounds. But when we
speak of volumes of gas we must remember that gas, unlike a liquid or
a solid, can be compressed or expanded to almost any dimensions. For
instance, we could easily fill our room with a ton of air if the walls
would stand the pressure; or we could pump out the air, until there
were but a few ounces of air left. But in one case the air would be so
highly compressed that it would exert a pressure of about 375 pounds
on every square inch of the wall of the room, while in the other case
its pressure would be almost infinitesimal. But 80 pounds of air in
a room of a thousand cubic feet would exert the same pressure as the
atmosphere, or 15 pounds on every square inch. And when we say that a
thousand cubic feet of hydrogen weighs only a little over 5 pounds, we
are talking about hydrogen at the same pressure as the atmosphere.

Since the hydrogen is sixteen times lighter than air, naturally it
will float in the air, just as a piece of wood will float in water
because it is lighter than the same volume of water. If we surrounded
the thousand cubic feet of hydrogen with a bag so that the gas will
not diffuse into the air and mix with it, we shall have a balloon
which would float in air provided the bag and the hydrogen it contains
do not weigh more than eighty pounds. As we rise from the surface of
the earth, the air becomes less and less dense, or, in other words,
it becomes lighter, and the balloon will keep on rising through the
atmosphere until it reaches a point at which its weight, gas-bag and
all, is exactly the same as that of an equal volume of air.

But there are many conditions that affect the height to which the
balloon will ascend. The higher we rise, the colder it is apt to
become, and cold has a tendency to compress the hydrogen, collapsing
the balloon and making it relatively heavier. When the sun beats upon a
balloon, it heats the hydrogen, expanding it and making it relatively
lighter, and if there is no room for this expansion to take place
in the bag, the bag will burst. For this reason, a big safety-valve
must be provided and the ordinary round balloon is open at the bottom
so that the hydrogen can escape when it expands too much and the
balloonist carries ballast in the form of sand which he can throw over
to lighten the balloon when the gas is contracted by a sudden draft of
cold air.

Although a round balloon carries no engine and no propeller, it can be
guided through the air to some degree. When an aëronaut wishes to go
in any particular direction, he sends up his balloon by throwing out
ballast or lowers it by letting out a certain amount of gas, until
he reaches a level at which he finds a breeze blowing in the desired
direction. Such was the airship of Civil War times, but for military
purposes it was not advisable to use free balloons, because of the
difficulty of controlling them. They were too liable to fall into the
hands of the enemy. All that was needed was a high observation post
from which the enemy could be watched, and from which observations
could be reported by telegraph. The balloon was not looked upon as a
fighting-machine.


ZEPPELIN'S FAILURES AND SUCCESSES

But Count Zeppelin was a man of vision. He dreamed of a real ship
of the air--a machine that would sail wherever the helmsman chose,
regardless of wind and weather. Many years elapsed before he actually
began to work out his dreams, and then he met with failure after
failure. He believed in big machines and the loss of one of his
airships meant the waste of a large sum of money, but he persisted,
even though he spent all his fortune, and had to go heavily in debt.
Every one thought him a crank until he built his third airship and
proved its worth by making a trip of 270 miles. At once the German
Government was interested and saw wonderful military possibilities in
the new craft. The Zeppelin was purchased by the government and money
was given the inventor to further his experiments.

That was not the end of his failures. Before the war broke out,
thirteen Zeppelins had been destroyed by one accident or another.
Evidently the building of Zeppelin airships was not a paying
undertaking, although they were used to carry passengers on short
aërial voyages. But the government made up money losses and Zeppelin
went on developing his airships.

Of course, he was not the only one to build airships, nor even the
first to build a dirigible. The French built some large dirigibles, but
they failed to see any great military advantage in ships that could
sail through the air, particularly after the airplane was invented,
and so it happened that when the war started the French were devoting
virtually all their energies to the construction of speedy, powerful
airplanes. As for the British, they did not pay much attention to
airships. The idea that their isles might be attacked from the sky
seemed an exceedingly remote possibility.


RIGID, SEMI-RIGID, AND FLEXIBLE BALLOONS

Count Zeppelin always held that the dirigible balloons must be rigid,
so that they could be driven through the air readily and would hold
their shape despite variations in the pressure of the hydrogen. The
French, on the other hand, used a semi-rigid airship; that is, one
in which a flexible balloon is attached to a rigid keel or body. The
British clung to the idea of an entirely flexible balloon and they
suspended their car from the gas-bag without any rigid framework to
hold the gas-bag in shape. In every case, the balloons were kept taut
or distended by means of air-bags or ballonets. These air-bags were
placed inside the gas-bags and as the hydrogen expanded it would force
the air out through valves, but the hydrogen itself would not escape.
When the hydrogen contracted, the air-bags were pumped full of air so
as to maintain the balloon in its fully distended condition. Additional
supplies of compressed hydrogen were kept in metal tanks.

[Illustration: (C) Underwood & Underwood

Giant British Dirigible built along the lines of a Zeppelin]

[Illustration: (C) Underwood & Underwood

One of the engine cars or "power eggs" of a British Dirigible]

In the Zeppelin balloon, however, the gas was contained in separate
bags which were placed in a framework of aluminum covered over with
fabric. Count Zeppelin did not believe in placing all his eggs in one
basket. If one of these balloons burst or was injured in any way,
there was enough buoyancy in the rest of the gas-bags to hold up the
airship. As the Zeppelins were enormous structures, the framework had
to be made strong and light, and it was built up of a latticework of
aluminum alloy. Aluminum itself was not strong enough for the purpose,
but a mixture of aluminum and zinc and later another alloy known
as duralumin, consisting of aluminum with three per cent of copper
and one per cent of nickel, provided a very rigid framework that
was exceedingly light. Duralumin is four or five times as strong as
aluminum and yet weighs but little more.

[Illustration: Photograph by International Film Service

Crew of the C-5 (American Coastal Dirigible) starting for Newfoundland
to make a Transatlantic Flight]

The body of the Zeppelin is not a perfect circle in section, but is
made up in the form of a polygon with sixteen sides, and the largest of
the Zeppelins used during the war contained sixteen compartments, in
each of which was placed a large hydrogen gas-bag. A super-Zeppelin,
as the latest type is called, was about seventy-five feet in diameter
and seven hundred and sixty feet long, or almost as long as three New
York street blocks. In its gas-bags it carried two million cubic feet
of hydrogen and although the whole machine with its fuel, stores, and
passengers weighed close to fifty tons, it was so much lighter than the
air it displaced that it had a reserve buoyancy of over ten tons.


KEEPING ENGINES CLEAR OF THE INFLAMMABLE HYDROGEN

As hydrogen is a very inflammable gas, it is extremely dangerous to
have an internal-combustion engine operating very near the gas-bags. In
the super-Zeppelins the engines were placed in four cars suspended from
the balloon. There was one of these cars forward, and one at the stern,
while near the center were two cars side by side. In the rear car there
were two engines, either of which could be used to drive the propeller.
By means of large steering rudders and horizontal rudders, the machine
could be forced to dive or rise or turn in either direction laterally.
The pilot of the Zeppelin had an elaborate operating-compartment
from which he could control the rudders, and he also had control
of the valves in the ballonets so that by the touch of a button he
could regulate the pressure of gas in any part of the dirigible.
There were nineteen men in the crew of the Zeppelin--two in the
operating-compartment, and two in each of the cars containing engines,
except for the one at the stern in which there were three men. The
other men were placed in what was known as the "cat walk" or passageway
running inside the framework under the gas-bags. These men were given
various tasks and were supposed to get as much sleep as they could, so
as to be ready to replace the other men at need.

The engine cars at each side of the balloon were known as power eggs
because of their general egg shape. At the center of the Zeppelin the
bombs were stored, and there were electro-magnetic releasing-devices
operated from the pilot's room by which the pilot could drop the bombs
whenever he chose. The Zeppelin also carried machine-guns to fight
off airplanes. Gasolene was stored in tanks which were placed in
various parts of the machine, any one of which could feed one or all
of the engines, and they were so arranged that they could be thrown
overboard when the gasolene was used up, so as to lighten the load of
the Zeppelin. Water ballast was used instead of sand, and alcohol was
mixed with the water to keep it from freezing. The machine which came
down in French territory and was captured before it could be destroyed
by the pilot, found itself unable to rise because in the intense cold
of the upper air the water ballast had frozen, and it could not be let
out to lighten the load of the Zeppelin.

[Illustration: Photograph from Kadel & Herbert

The Curious Tail of a Kite Balloon]

[Illustration: British Official Photograph from Kadel & Herbert

Observers in the Basket of an Observation-Balloon]


THE ZEPPELIN'S TINY ANTAGONISTS

The one thing above all others that the Zeppelin commander feared
was the attack of airplanes. In the early stages of the war, it
was considered unsafe for airplanes to fly by night because of the
difficulty of making a landing in the dark. Later this difficulty
was overcome by the use of search-lights at the landing-fields. The
airplane would signal its desire to land and the search-lights would
point out the proper landing-field for it. So that after the first few
months of the war Zeppelins were subjected to the danger of airplane
attack. Of course, on a dark night it was very difficult for an
airplane to locate a Zeppelin, because the huge machine could not be
seen and the throb of its engines was drowned out by the engines of the
airplane itself. Nevertheless, Zeppelins were occasionally located
and destroyed by airplanes.

[Illustration: Photograph by Kadel & Herbert

Enormous Range-finders mounted on a Gun Turret of an American Warship]

The danger of the Zeppelin lay in the fact that it was supported by
an enormous volume of very inflammable gas and the airplane needed
but to set fire to this gas to cause the destruction of the giant of
the air. And so the machine-guns carried by airplanes were provided
with explosive, flaming bullets. A burst of flame within the gas-bag
would not set the gas on fire, because there would be no air inside to
feed the fire, but surrounding the gas-bag there was always a certain
leakage of hydrogen which would mix with the air in the compartment and
this would produce an explosive mixture which needed but the touch of
fire to set it off. The Zeppelin was provided with a ventilating-system
to carry off these explosive gases, but they could never be disposed
of very effectively, and, as a consequence, a number of Zeppelins were
destroyed by the tiny antagonists that were sent up by the British and
the French. To fight off these assailants the Germans provided their
Zeppelins with guns which would fire shrapnel shell. It is difficult
for a Zeppelin to use machine-guns against an airplane because the
latter would merely climb above the Zeppelin and would be shielded by
the balloon itself. And so the Germans put a gun emplacement on top of
the balloon both forward and aft. There was a deck extending along the
top of the balloon which was reached by a ladder running up through
the center of the airship. But it was impossible to ward off the fleet
little antagonists, once the dirigible was discovered. True, a Zeppelin
could make as much as seventy miles per hour, but the fastest airplanes
could travel twice as fast as that.


SUSPENDING AN OBSERVER BELOW THE ZEPPELIN

One ingenious scheme that was tried was to suspend an observation car
under the Zeppelin. The car was about fourteen feet long and five feet
in diameter, fitted with a tail to keep it headed in the direction it
was towed. It had glass windows forward and there was plenty of room
in it for a man to lie at full length and make observations of things
below. The car with its observer could be lowered a few thousand feet
below the Zeppelin, so that the observer could watch proceedings below,
while the airship remained hidden among the clouds. The observer was
connected by telephone with the chart-room of the Zeppelin and could
report his discoveries or even act as a pilot to direct the course of
the ship.

But despite everything that could be done, the Zeppelin eventually
proved a failure as a war-vessel because it was so very costly to
construct and operate and could so easily be destroyed, and the Germans
began to build huge airplanes with which bombing-raids could be
continued.

Strange to say, however, although the Germans were ready to admit the
failure of their big airship, when the war stopped the Allies were
actually building machines patterned after the Zeppelin, but even
larger, and expected to use them for bombing-excursions over Germany.
This astonishing turn of the tables was due to the fact that America
had made a contribution to aëronautics that solved the one chief
drawback of the Zeppelin.


A BALLOON GAS THAT WILL NOT BURN

When we entered the war against Germany, our allies placed before
us all their problems and among them was this one of the highly
inflammable airship. Could we not furnish a substitute for hydrogen
that would not burn? It was suggested to us that helium would do if we
could produce that gas cheaply and in sufficient quantity. Now, helium
has a history of its own that is exceedingly interesting.

Every now and then the moon bobs its head into our light and we have a
solar eclipse. But our satellite is not big enough to cut off all the
light of the big luminary and the fiery atmosphere of the sun shows
us a brilliant halo all around the black disk of the moon. Long ago,
astronomers analyzed this flaming atmosphere with the spectroscope,
and by the different bands of light that appeared they were able to
determine what gases were present in the sun's atmosphere. But there
was one band of bright yellow which they could not identify. Evidently
this was produced by a gas unknown on earth, and they called it
"helium" or "sun" gas.

For a quarter of a century this sun gas remained a mystery; then one
day, in 1895, Sir William Ramsay discovered the same band of light
when studying the spectrum of the mineral cleveite. The fact that
astronomers had been able to single out an element on the sun ninety
million miles away before our chemists could find it right here on
earth, produced a mild sensation, but the general public attached no
special importance to the gas itself. It proved to be a very light
substance, next to hydrogen the lightest of gases, and for years it
resisted all attempts at liquefaction. Only when Onnes, the Dutch
scientist, succeeded in getting it down to a temperature of 450 degrees
below zero, Fahrenheit, did the gas yield to the chill and condense
into a liquid. The gas would not burn; it would not combine with any
other elements, and apparently it had no use on earth, and it might
have remained indefinitely a lazy member of the chemical fraternity had
not the great world conflict stirred us into frenzied activity in all
branches of science in our effort to beat the Hun.

Because the gas had no commercial value, there was only a small amount
of helium to be found in the whole world. Not a single laboratory in
the United States had more than five cubic feet of it and its price
ranged from $1,500 to $6,000 per cubic foot. At the lowest price it
would cost $3,000,000,000 to provide gas enough for one airship of
Zeppelin dimensions and it seemed absurd even to think of a helium
airship.


AMERICAN CHEMISTS TO THE RESCUE

Just before the war it was discovered that there is a considerable
amount of helium in the natural gas of Oklahoma, Texas, and Kansas,
and Sir William Ramsey suggested that our chemists might study some
method of getting helium from this source. The only way of separating
it out was to liquefy the gases by subjecting them to extreme cold. All
gases turn to liquid if they are cooled sufficiently, and then further
cold will freeze them solid. But helium can stand more cold than any
other and this fact gave the clue to its recovery from natural gas.
The latter was frozen and one after another the different elements
condensed into liquid, until finally only helium was left. This sounds
simple, but it is a difficult matter to get such low temperature
as that on a large scale and do it economically. To be of any real
service in aëronautics helium would have to be reduced in cost from
fifteen hundred dollars to less than ten cents per cubic foot. Several
different kinds of refrigerating-machinery were tried and finally just
before the war was brought to a close by the armistice we had succeeded
in producing helium at the rate of eight cents per cubic foot, with
the prospect of reducing its cost still further. A large plant for
recovering helium was being built. The plant will have been completed
before this book is published, and it will be turning out helium for
peaceful instead of military airships.

The reduction in the cost of helium is really one of the most
important developments of this war. By removing the fire risk from
airships we can safely use these craft for aërial cruises or for quick
long-distance travel over land and sea. For, even in time of peace,
sailing under millions of cubic feet of hydrogen is a serious matter.
Although no incendiary bullets are to be feared, there is always the
danger of setting fire to the gas within the exhaust of the engines.
Engines have had to be hung in cars well below the balloon proper.
But with helium in the gas-bags the engines can be placed inside the
balloon envelop and the propellers can operate on the center line of
the car.

In the case of one Zeppelin, the hydrogen was set on fire by an
electric spark produced by friction on the fabric of one of the
gas-bags, and so even with the engine exhausts properly screened there
is danger. The helium airship, however, would be perfectly safe from
fire and passengers could smoke on deck or in their cabins within the
balloon itself without any more fear of fire than they would have on
shipboard. Wonderful possibilities have been opened by the production
of helium on a large and economical scale, and the airship seems
destined to play an important part in transportation very soon. As this
book is going to press, we learn of enormous dirigibles about to be
built in England for passenger service, which will have half again as
great a lifting-power as the largest Zeppelins. The final chapter of
the story of dirigibles is yet to be written, but in concluding this
chapter it is interesting to note that the world's greatest aëronautic
expert got his first inspiration from America and finally that America
has now furnished the one element which was lacking to make the
dirigible balloon a real success.



CHAPTER IX

GETTING THE RANGE


Every person with a good pair of eyes in his head is a range-finder. He
may not know it, but he is, just the same, and the way to prove it is
to try a little range-finding on a small scale.

Use the top of a table for your field of operations, and pick out
some spot within easy reach of your hand for the target whose range
you wish to find. The target may be a penny or a small circle drawn
on a piece of white paper. Take a pencil in your hand and imagine it
is a shell which you are going to land on the target. It is not quite
fair to have a bird's-eye view of the field, so get down on your knees
and bring your eyes within a few inches of the top of the table. Now
close one eye and making your hand describe an arc through the air,
like the arc that a shell would describe, see how nearly you can bring
the pencil-point down on the center of the target. Do it slowly, so
that your eye may guide the hand throughout its course. You will be
surprised to find out how far you come short, or overreach the mark.
You will have actually to grope for the target. If by any chance you
should score a hit on the first try, you may be sure that it is an
accident.

Have a friend move the target around to a different position, and try
again. Evidently, with one eye you are not a good range-finder; but now
use two eyes and you will score a hit every time. Not only can you land
the pencil on the penny, but you will be able to bring it down on the
very center of the target.

The explanation of this is that when you bring your eyes to bear upon
any object that is near by, they have to be turned in slightly, so
that both of them shall be aimed directly at that object. The nearer
the object, the more they are turned in, and the farther the object,
the more nearly parallel are the eyes. Long experience has taught you
to gage the distance of an object by the feel of the eyes--that is, by
the effort your muscles have to make to pull the eyes to a focus--and
in this way the eyes give you the range of an object. You do not know
what the distance is in feet or inches, but you can tell when the
pencil-point has moved out until it is at the same focus as the target.

The experiment can be tried on a larger scale with the end of a
fishing-rod, but here you will probably have to use a larger target.
However, there is a limit to which you can gage the range. At a
distance of, say, fifteen or twenty feet, a variation of a few inches
beyond or this side of the target makes scarcely any change in the
focus of the eyes. That is because the eyes are so close together. If
they were farther apart, they could tell the range at much greater
distances.


SPREADING THE EYES FAR APART

Now the ordinary range-finder, used in the army and in the navy, is an
arrangement for spreading the eyes apart to a considerable distance.
Of course the eyes are not actually spread, but their vision is. The
range-finder is really a double telescope. The barrel is not pointed
at an object, but it is held at right angles to it. You look into the
instrument at the middle of the barrel and out of it at the two ends.
A system of mirrors or prisms makes this possible. The range-finder
may be a yard or more in length, which is equivalent to spreading your
eyes a yard or more apart. Now, the prisms or object-glasses at the
ends of the tube are adjustable, so that they will turn in until they
focus directly on the target whose range you wish to find, and the
angle through which these glasses are turned gives a measure of the
distance of the target. The whole thing is calculated out so that the
distance in feet, yards, or meters, or whatever the measure may be, is
registered on a scale in the range-finder. Ordinarily only one eye is
used to look through the range-finder, because the system of mirrors is
set to divide the sight of that one eye and make it serve the purposes
of two. That leaves the other eye free to read the scale, which comes
automatically into view as the range-finder is adjusted for the
different ranges.

On the battle-ships enormous range-finders are used. Some of them are
twenty feet long. With the eyes spread as far apart as that and with a
microscope to read the scale, you can imagine how accurately the range
can be found, even when the target is miles away. But on land such big
range-finders cannot conveniently be used; they are too bulky. When it
is necessary to get the range of a very distant object, two observers
are used who are stationed several hundred yards apart. These observers
have telescopes which they bear upon the object, and the angle through
which they have to turn the telescope is reported by telephone to the
battery, where, by a rapid calculation, it is possible to estimate the
exact position of the target. Then the gun is moved up or down, to the
right or to the left, according to the calculation. The observers have
to creep as near to the enemy as possible and they must be up high
enough to command a good view of the target. Sometimes they are placed
on top of telegraph poles or hidden up a tall tree, or in a church
steeple.


GETTING THE OBSERVER OFF THE GROUND

This was the method of getting the range in previous wars and it was
used to a considerable extent in the war we have just been through. But
the great European conflict brought out wonderful improvements in all
branches of fighting; and range-finding was absolutely revolutionized,
because shelling was done at greater ranges than ever before, but
chiefly because the war was carried up into the sky.

A bird's-eye observation is much more accurate than any that can be
obtained from the ground. Even before this war, some observations were
taken by sending a man up in a kite, particularly a kite towed from
a ship, and even as far back as the Civil War captive balloons were
used to raise an observer to a good height above the ground. They were
the ordinary round balloons, but the observation balloon of to-day is
a very different-looking object. It is a sausage-shaped gas-bag that
is held on a slant to the wind like a kite, so that the wind helps to
hold it up. To keep it head-on to the wind, there is a big air-bag that
curls around the lower end of the sausage. This acts like a rudder,
and steadies the balloon. Some balloons have a tail consisting of a
series of cone-shaped cups strung on a cable. A kite balloon will
ride steadily in a wind that would dash a common round balloon in
all directions. Observers in these kite balloons are provided with
telephone instruments by which they can communicate instantly with the
battery whose fire they are directing. But a kite balloon is a helpless
object; it cannot fight the enemy. The hydrogen gas that holds it up
will burn furiously if set on fire. In the war an enemy airplane had
merely to drop a bomb upon it or fire an incendiary bullet into it,
and the balloon would go up in smoke. Nothing could save it, once it
took fire, and all the observers could do was to jump for their lives
as soon as they saw the enemy close by. They always had parachutes
strapped to them, so they could leap without an instant's delay in case
of sudden danger. At the very first approach of an enemy airplane, the
kite balloon had to be hauled down or it would surely be destroyed, and
so kite balloons were not very dependable observation stations for the
side which did not control the air.

As stated in the preceding chapter, just before the fighting came to
an end, our army was preparing to use balloons that were not afraid of
flaming bullets, because they were to be filled with a gas that would
not burn.


MAKING MAPS WITH A CAMERA

Because airplanes filled the sky with eyes, everything that the army
did near the front had to be carefully hidden from the winged scouts.
Batteries were concealed in the woods, or under canopies where the
woods were shot to pieces, or they were placed in dugouts so that they
could not be located. Such targets could seldom be found with a kite
balloon. It was the task of airplane observers to search out these
hidden batteries. The eye alone was not depended upon to find them.
Large cameras were used with telescopic lenses which would bring the
surface of the earth near while the airplane flew at a safe height.
These were often motion-picture cameras which would automatically make
an exposure every second, or every few seconds.

[Illustration: (C) Underwood & Underwood

British Anti-aircraft Section getting the Range of an Enemy Aviator]

When the machine returned from a photographing-expedition, the
films were developed and printed, and then pieced together to form
a photographic map. The map was scrutinized very carefully for any
evidence of a hidden battery or for any suspicious enemy object. As
the enemy was always careful to disguise its work, the camera had to
be fitted with color-screens which would enable it to pick out details
that would not be evident to the eye. As new photographic maps were
made from day to day, they were carefully compared one with the
other so that it might be seen if there was the slightest change in
them which would indicate some enemy activity. As soon as a suspicious
spot was discovered, its position was noted on a large-scale military
map and the guns were trained upon it.

[Illustration: (C) Kadel & Herbert

A British Aviator making Observations over the German Lines]


CORRECTING THE AIM

It is one thing to know where the target is and another to get the
shell to drop upon it. In the firing of a shell a distance of ten or
twenty miles, the slightest variation in the gun will make a difference
of many yards in the point where the shell lands. Not only that, but
the direction of the wind and the density of the air have a part to
play in the journey of the shell. If the shell traveled through a
vacuum, it would be a much simpler matter to score a hit by the map
alone. But even then there would be some differences, because a gun
has to be "warmed up" before it will fire according to calculation.
That is why it is necessary to have observers, or "spotters" as they
are called, to see where the shell actually do land and tell the
gun-pointers whether to elevate or depress the gun, and how much to
"traverse" it--that is, move it sideways. This would not be a very
difficult matter if there were only one gun firing, but when a large
number of guns are being used, as was almost invariably the case in the
war, the spotter had to know which shell belonged to the gun he was
directing.

One of the most important inventions of the war was the wireless
telephone, which airplanes used and which were brought to such
perfection that the pilot of an airplane could talk to a station
on the earth without any difficulty, from a distance of ten miles;
and in some cases he could reach a range of fifty miles. With the
wireless telephone, the observer could communicate instantly with the
gun-pointer, and tell him when to fire. Usually thirty seconds were
allowed after the signal sent by the observer before the gun was fired,
and on the instant of firing, a signal was sent to the man in the
airplane to be on the lookout for the shell. Knowing the position of
the target, the gun-pointer would know how long it would take the shell
to travel through the air, and he would keep the man in the airplane
posted, warning him at ten seconds, five seconds, and so forth, before
the shell was due to land.

In order to keep the eyes fresh for observation and not to have them
distracted by other sights, the observer usually gazed into space until
just before the instant the shell was to land. Then he would look for
the column of smoke produced by the explosion of the shell and report
back to the battery how far wide of the mark the shell had landed. A
number of shell would be fired at regular intervals, say four or five
per minute, so that the observer would know which shell belonged to the
gun in question.

There are different kinds of shell. Some will explode on the instant of
contact with the earth. These are meant to spread destruction over the
surface. There are other shell which will explode a little more slowly
and these penetrate the ground to some extent before going off; while
a third type has a delayed action and is intended to be buried deep in
the ground before exploding, so as to destroy dugouts and underground
positions. The bursts of smoke from the delayed-action shell and the
semi-delayed-action shell rise in a slender vertical column and are not
so easily seen from the sky. The instantaneous shell, however, produces
a broad burst of smoke which can be spotted much more readily, and
this enables the man in the airplane to determine the position of the
shell with greater accuracy. For this reason, instantaneous shell were
usually used for spotting-purposes, and after the gun had found its
target, other shell were used suited to the character of the work that
was to be done.


MINIATURE BATTLE-FIELDS

Observation of shell-fire from an airplane called for a great deal of
experience, and our spotters were given training on a miniature scale
before they undertook to do spotting from the air. A scaffolding was
erected in the training-quarters over a large picture of a typical bit
of enemy territory. Men were posted at the top of this scaffolding so
that they could get a bird's-eye view of the territory represented
on the map, and they were connected by telephone or telegraph with
men below who represented the batteries. The instructor would flash a
little electric light here and there on the miniature battle-field, and
the observers had to locate these flashes and tell instantly how far
they were from certain targets. This taught them to be keen and quick
and to judge distance accurately. Airplane observing was difficult and
dangerous, and often impossible. On cloudy days the observer might be
unable to fly at a safe height without being lost in the clouds. Then
dependence had to be placed upon observers stationed at vantage-points
near the enemy, or in kite balloons.


SPOTTING BY SOUND

When there is no way of seeing the work of a gun, it is still possible
to correct the aim, because the shell can be made to do its own
spotting. Every time a shell lands, it immediately announces the fact
with a loud report. That report is really a message which the shell
sends out in all directions with a speed of nearly 800 miles per
hour--1,142 feet per second, to be exact. This sound-message is picked
up by a recorder at several different receiving-stations. Of course it
reaches the nearest station a fraction of a second before it arrives
at the next nearest one. The distance of each station from the target
is known by careful measurement on the map, and the time it takes for
sound to travel from the target to each station is accurately worked
out. If the sound arrives at each station on schedule time, the shell
has scored a hit; but if it reaches one station a trifle ahead of time
and lags behind at another, that is evidence that the shell has missed
the target and a careful measure of the distance in time shows how
far and in what direction it is wide of the mark. In this way it was
possible to come within fifty or even twenty-five yards of the target.

This sound-method was also used to locate an enemy battery. It was
often well nigh impossible to locate a battery in any other way. With
the use of smokeless powder, there is nothing to betray the position
of the gun, except the flash at the instant of discharge, and even the
flash was hidden by screens from the view of an airplane. Aside from
this, when an airplane came near enough actually to see one of these
guns, the gun would stop firing until the airplane had been driven off.
But a big gun has a big voice, and it is impossible to silence it.
Often a gun whose position has remained a secret for a long time was
discovered because the gun itself "peached."

The main trouble with sound-spotting was that there were usually so
many shell and guns going off at the same time that it was difficult
if not impossible to distinguish one from another. Sometimes the voice
of a hidden gun was purposely drowned by the noise of a lot of other
guns. After all, the main responsibility for good shooting had to fall
on observers who could actually see the target, and when we think of
the splendid work of our soldiers in the war, we must not forget to
give full credit to the tireless men whose duty it was to watch, to
the men on wings who dared the fierce battle-planes of the enemy, to
the men afloat high in the sky who must leap at a moment's notice from
under a blazing mass of hydrogen, and finally to the men who crept out
to perilous vantage-points at risk of instant death, in order to make
the fire of their batteries tell.



CHAPTER X

TALKING IN THE SKY


In one field of war invention the United States held almost a monopoly
and the progress Americans achieved was epoch-making.

Before the war, an aviator when on the wing was both deaf and dumb.
He could communicate with other airplanes or with the ground only by
signal or, for short distances, by radiotelegraphy, but he could not
even carry on conversation with a fellow passenger in the machine
without a speaking-tube fitted to mouth and ears so as to cut out
the terrific roar of his own engine. Now the range of his voice
has been so extended that he can chat with fellow aviators miles
away. This remarkable achievement and many others in the field of
radio-communication hinge upon a delicate electrical device invented by
Deforest in 1906 and known as the "audion." For years this instrument
was used by radiotelegraphers without a real appreciation of its
marvelous possibilities, and, as a matter of fact, in its earlier crude
form it was not capable of performing the wonders it has achieved since
it was taken over and developed by the engineers of the Bell Telephone
System.


THE AUDION

Although the audion is familiar to all amateur radio-operators, we
shall have to give a brief outline of its construction and operation
for the benefit of those who have not had the opportunity to dabble in
wireless telegraphy.

The audion is a small glass bulb from which the air is exhausted to
a high degree of vacuum. The bulb contains three elements. One is a
tiny filament which is heated to incandescence by a battery, so that
it emits negatively charged electrons. The filament is at one side of
the bulb and at the opposite side there is a metal plate. When the
plate and the filament are connected with opposite poles of a battery,
there is a flow of current between them, but because only negative
electrons are emitted by the filament, the current will flow only
in one direction--that is, from the plate to the filament. If the
audion be placed in the circuit of an alternating-current generator,
it will let through only the current running in one direction. Thus it
will "rectify" the current or convert alternating current into direct
current.

But the most important part of the audion, the part for which Deforest
is responsible, is the third element, which is a grid or flat coil of
platinum wire placed between the filament and the plate. This grid
furnishes a very delicate control of the strength of the electric
current between plate and filament. The slightest change in electric
power in the grid will produce large changes of power in the current
flowing through the audion. This makes it possible to magnify or
amplify very feeble electric waves, and the extent to which the
amplifying can be carried is virtually limitless, because a series
of audions can be used, the current passing through the first being
connected with the grid of the next, and so on.


TALKING FROM NEW YORK TO SAN FRANCISCO

There is a limit to which telephone conversations can be carried on
over a wire, unless there is some way of adding fresh energy along the
line. For years all sorts of experiments were tried with mechanical
devices which would receive a telephone message and send it on with
a fresh relay of current. But these devices distorted the message so
that it was unintelligible. The range of wire telephony was greatly
increased by the use of certain coils invented by Pupin, which were
placed in the line at intervals; but still there was a limit to which
conversation could be carried on by wire and it looked as if it would
never be possible to telephone from one end of this big country of ours
to the other. But the audion supplied a wonderfully efficient relay and
one day we awoke to hear San Francisco calling, "Hello," to New York.

Used as a relay, the improved audion made it possible to pick up very
faint wireless-telegraph messages and in that way increased the range
of radio outfits. Messages could be received from great distances
without any extensive or elaborate aërials, and the audion could be
used at the sending-station to magnify the signals transmitted and send
them forth with far greater power.

Having improved the audion and used it successfully for long-distance
telephone conversation over wires, the telephone company began to
experiment with wireless telephony. They believed that it might be
possible to use radiotelephony in places where wires could not be laid.
For instance, it might be possible to talk across the Atlantic.

But before we go farther, just a word of explanation concerning
radiotelegraphy and radiotelephony for the benefit of those who have
not even an elementary knowledge of the subject.


SIMPLE EXPLANATION OF RADIOTELEGRAPHY

Suppose we should set up two stakes in a pond of water, at some
distance from each other, and around each we set a ring-shaped cork
float. If we should move one of these floats up and down on its stake,
it would produce ripples in the water which would spread out in all
directions and finally would reach the opposite stake and cause the
float there to bob up and down in exactly the same way as did the float
moved by hand. In wireless telegraphy the two stakes are represented by
antennæ or aërials and the cork floats are electric charges which are
sent oscillating up and down the antennæ. The oscillations produced at
one aërial will set up electro-magnetic waves which will spread out in
all directions in the ether until they reach a receiving-aërial, and
there they will produce electric oscillations similar to the ones at
the transmitting-antenna.

Telegraph signals are sent by the breaking up of the oscillations at
the transmitting-station into long and short trains of oscillations
corresponding to the dots and dashes of ordinary wire telegraphy. In
other words, while the sending-key is held down for a dash, there
will be a long series of oscillations in the antenna, and for the dot
a short series, and these short and long trains of waves will spread
out to the receiving-aërial where they will reproduce the same series
of oscillations. But only a small part of the energy will act on the
receiving-aërial because the waves like those on the pond spread in all
directions and grow rapidly weaker. Hence the advantage of an extremely
delicate instrument like the audion to amplify the signals received.

The oscillations used in wireless telegraphy these days are very rapid,
usually entirely too rapid, to affect an ordinary telephone receiver,
and if they did they would produce a note of such high pitch that it
could not be heard. So it is customary to interrupt the oscillations,
breaking them up into short trains of waves, and these successive
trains produce a note of low enough pitch to be heard in the telephone
receiver. Of course the interruptions are of such high frequency that
in the sending of a dot-and-dash message each dot is made up of a great
many of the short trains of waves.

Now in radiotelephony it is not necessary to break up the oscillations,
but they are allowed to run continuously at very high speed and act as
carriers for other waves produced by speaking into the transmitter;
that is, a single speech-wave would be made up of a large number of
smaller waves. To make wireless telephony a success it was necessary
to find some way of making perfectly uniform carrier-waves, and
then of loading on them waves of speech. Of course, the latter are
not sound-waves, because they are not waves of air, but they are
electro-magnetic waves corresponding exactly to the sound-waves of
air and at the receiving-end they affect the telephone receiver in
the same way that it is affected by the electric waves which are sent
over telephone wires. The telephone engineers found that the audion
could be used to regulate the carrier-waves and also to superpose the
speech-waves upon them, and at the receiving-station the audion was
used to pick up these waves, no matter how feeble they might be, and
amplify them so that they could be heard in a telephone receiver.


TALKING WITHOUT WIRES

Attempts at long-distance talking without wires were made from Montauk
Point, on the tip of Long Island, to Wilmington, Delaware, and they
were successful. This was in 1915. The apparatus was still further
improved and then the experiment was tried of talking from the big
Arlington station near Washington to Darien, on the Isthmus of Panama.
This was a distance of twenty-one hundred miles, and speech was
actually transmitted through space over that great distance. That
having proved successful, the next attempt was to talk from Arlington
to Mare Island and San Diego, on the Pacific Coast, a distance of over
twenty-five hundred miles. This proved a success, too, and it was
found possible even to talk as far as Honolulu.

[Illustration: (C) G. V. Buck

Radio Head-gear of an Airman]

[Illustration: (C) G. V. Buck

Carrying on Conversation by Radio with an Aviator Miles Away]

The engineers now felt confident that they could talk across the
Atlantic to Europe, and so in October of 1915 arrangements were made to
conduct experiments between Arlington and the Eiffel Tower in Paris.
Although the war was at its height, and the French were straining every
effort to hold back the Germans at that time, and although there were
constant demands for the use of radiotelegraphy, the French showed
such an appreciation of science that they were willing to lend their
aid to these experiments. The Eiffel Tower could be used only for
short periods of time, and there was much interference from other
high-powered stations. Nevertheless, the experiment proved perfectly
successful, and conversation was carried on between our capital and
that of France, a distance of thirty-six hundred miles. At the same
time, an operator in Honolulu, forty-five hundred miles away, heard the
messages, and so the voice at Arlington carried virtually one third of
the way around the globe. After that achievement, there was a lull in
the wireless-telephone experiments because of the war.

But there soon came an opportunity to make very practical use of all
the experimental work. As soon as there seemed to be a possibility that
we might be drawn into the war, the Secretary of the Navy asked for the
design of apparatus that would make it possible for ships to converse
with one another and with shore stations. Of course all vessels are
equipped with wireless-telegraph apparatus, but there is a decided
advantage in having the captain of one ship talk directly with the
captain of another ship, or take his orders from headquarters, with an
ordinary telephone receiver and transmitter. A special equipment was
designed for battle-ships and on test it was found that ships could
easily converse with one another over a distance of thirty-five miles
and to shore stations from a distance of a hundred and seventy-five
miles. The apparatus was so improved that nine conversations could be
carried on at the same time without any interference of one by the
others.

[Illustration: (C) American Institute of Electrical Engineers

Long Distance Radio Apparatus at the Arlington (Va.) Station, with
enlarged view of the Type of Vacuum Tube used]

When it became certain that we should have to enter the war, there came
a call for radiotelephone apparatus for submarine-chasers, and work was
started on small, compact outfits for these little vessels.


RADIOTELEPHONES FOR AIRPLANES

Then there was a demand for radiotelephone apparatus to be used on
airplanes. This was a much more complicated matter and called for a
great deal of study. The way in which problem after problem arose and
was solved makes an exceedingly interesting narrative. It seemed almost
absurd to think that a delicate radiotelegraph apparatus could be made
to work in the terrific noise and jarring of an airplane. The first
task was to make the apparatus noise-proof. A special sound-proof room
was constructed in which a noise was produced exactly imitating that of
the engine exhaust of an airplane engine. In this room, various helmets
were tried in order to see whether they would be proof against the
noise, and finally a very suitable helmet was designed, in which the
telephone receiver and transmitter were installed.

By summer-time the work had proceeded so far that an airplane equipped
with transmitting-apparatus could send spoken messages to an operator
on the ground from a distance of two miles. The antenna of the airplane
consisted of a wire with a weight on the lower end, which hung down
about one hundred yards from the body of the machine. But a trailing
antenna was a nuisance in airplane manoeuvers, and it was also found
that the helmet which was so satisfactory in the laboratory was not
just the thing for actual service in an airplane. It had to fit very
tightly around the ears and the mouth, and as the airplane went to
high altitudes where the air-pressure was much lower than at the
ground level, painful pressures were produced in the ears which were
most annoying. Aside from that, in actual warfare airplanes have to
operate at extreme heights, where the air is so rare that oxygen must
be supplied to the aviators, and it was difficult to provide this
supply of oxygen with the radio helmet tightly strapped to the head of
the operator. But after considerable experiment, this difficulty was
overcome and also that of the varying pressures on the ears.

Another great difficulty was to obtain a steady supply of power on
the airplane to operate the transmitting-apparatus. It has been
the practice to supply current on airplanes for wireless-telegraph
apparatus by means of a small electric generator which is revolved by
a little propeller. The propeller in turn is revolved by the rush of
air as it is carried along by the plane. But the speed of the airplane
varies considerably. At times, it may be traveling at only forty miles
per hour, and at other times as high as one hundred and sixty miles per
hour, so that the little generator is subjected to great variations of
speed and consequent variations of voltage. This made it impossible
to produce the steady oscillations that are required in wireless
telephony. After considerable experiment, a generator was produced with
two windings, one of which operated through a vacuum tube, somewhat
like an audion, and to resist the increase of voltage produced by the
other winding.

Then another trouble developed. The sparks produced by the magneto
in the airplane motor set up electro-magnetic waves which seriously
affected the receiving-instrument. There was no way of getting rid of
the magneto, but the wires leading from it to the engine were incased
in metal tubes which were grounded at frequent intervals, and in that
way the trouble was overcome to a large extent. The magnetos themselves
were also incased in such a way that electro-magnetic waves would not
be radiated from them.

Instead of using trailing wires which were liable to become entangled
in the propeller, the antenna was extended from the upper plane to the
tail of the machine, and later it was found that by using two short
trailing antennæ one from each tip of the wings, the very best results
could be obtained. Still another development was to embed the antenna
wires in the wings of the plane.

It was considered necessary, if the apparatus was to be practicable,
to be able to use it over a distance of two thousand yards, but in
experiments conducted in October, 1917, a couple of airplanes were able
to talk to each other when twenty-three miles apart, and conversations
were carried on with the ground from a distance of forty-five miles.
The conditions under which these distances were attained were
unusual, and a distance of three miles was accepted as a standard for
communication between airplanes. The apparatus weighed only fifty-eight
pounds and it was connected with both the pilot and the observer so
that they could carry on conversations with each other and could both
hear the conversation with other airplanes or the ground. As a matter
of fact, airplanes with standard apparatus are able to talk clearly
to a distance of five miles and even to a distance of ten miles when
conditions are favorable, and they can receive messages from the ground
over almost any distance.

A similar apparatus was constructed for submarine-chasers with
a standard range of conversation of over five miles. Apparatus
was manufactured in large quantities in this country and all our
submarine-chasers were equipped with it, as well as a great many
of our airplanes and seaplanes, and we furnished radio-apparatus
sets to our allies which proved of immense value in the war. This
was particularly so in the case of submarine detection, when it was
possible for a seaplane or a balloon to report its findings at once
to submarine-chasers and destroyers, and to guide them in pursuit of
submarines.

The improved audion holds out a wonderful future for radiotelephony.
For receiving, at least, no elaborate aërial will be needed, and with a
small loop of wire, an audion or two, and simple tuning-apparatus any
one can hear the radio gossip of the whole world.


TELEGRAPHING TWELVE HUNDRED WORDS PER MINUTE

Some remarkable advances were made in telegraphy also. During the
war and since, messages have been sent direct from Washington to all
parts of the world. In the telegraph room operators are connected by
wire with the different radio stations along the coast and they can
control the radio transmitters, sending their messages without any
repeating at the radio stations. Long messages are copied off on a
machine something like a type-writer, which, however, does not make
type impressions, but cuts perforations in a long sheet of paper. The
paper is then run through a transmitter at a high speed and the message
is sent out at a rate of as much as twelve hundred words a minute. At
the receiving-station, the message is received photographically on a
strip of paper. The receiving-instrument has a fine quartz thread in
it, which carries a tiny mirror. A beam of light is reflected from the
mirror upon the strip of sensitized paper. The radio waves twist the
quartz thread ever so slightly, which makes the beam of light play back
and forth, but of course the motion is greatly magnified. In this way
a perfect record is made of the message in dots and dashes, which are
translated into the corresponding letters of the alphabet.


DETECTING RADIO SPIES

There is another radio invention which we contributed during the war,
that proved of utmost service in thwarting German spies and which
is going to prove equally valuable in time of peace. Although a war
invention, its peacetime service will be to save lives. It is a very
simple matter to rig up a wireless-telegraph system that will send
messages to a considerable distance, and simpler still to rig up a
receiving-set. European governments have always discouraged amateur
radiotelegraphy, but in this country restrictions used to be so
slight that almost any one could set up and use a radio set, both for
receiving and for transmitting. When we entered the war we were glad
that amateurs had been encouraged to play with wireless, because we had
hundreds of good radio operators ready to work the sets which the army
and the navy needed.

But this was a disadvantage, too. Many operators were either Germans
or pro-Germans and were only too willing to use their radio experience
in the interest of our enemies. It was a simple matter to obtain
the necessary apparatus, because there was plenty of it to be had
everywhere. They could send orders to fellow workers and receive
messages from them, or they could listen to dispatches sent out by
the government and glean information of great military and naval
importance. The apparatus could easily be concealed: a wire hung inside
a chimney, a water-pipe, even a brass bedstead could be used for the
receiving-aërial. It was highly important that these concealed stations
be located, but how were they to be discovered?


THE WIRELESS COMPASS

This problem was solved very nicely. The audion had made it possible to
receive radio signals on a very small aërial. In place of the ordinary
stationary aërial a frame five feet square was set up so that it could
be turned to any point of the compass. A few turns of copper-bronze
wire were wound round it. This was called the "wireless compass."
It was set up on the roof of the radio station and concealed within
a cupola. The shaft on which it was mounted extended down into the
operating-room and carried a wheel by which it could be turned. On the
shaft was a circular band of aluminum engraved with the 360 degrees of
the circle, and a couple of fixed pointers indicated true north and
south. Now when a signal was received by the aërial, if it struck the
frame edgewise the radio waves would reach one side before they would
the other. Taking a single wave, as shown by the drawing, Fig. 11, we
see that while the crest of the wave is sweeping over one side of the
frame, the trough of the wave is passing the other side. Two currents
are set up in the radio compass, one in the wires at the near side of
the compass, and another in the wires at the far side of the compass.
As these currents are of the same direction, they oppose each other and
tend to kill each other off, but one of the currents is stronger than
the other because the crest of the wave is sweeping over that side,
while the trough of the wave is passing over the other. The length
of the wave may be anything, but always one side will be stronger than
the other, and a current equal in strength to the difference between
the two currents goes down into the operating-room and affects the
receiver. Now when the compass is set at right angles to the oncoming
wave, both sides are affected simultaneously and with the same
strength, so that they kill each other off completely, and no current
goes down to the receiver. Thus the strength of the signal received can
be varied from a maximum, when the compass is parallel to the oncoming
waves, to zero, when it is at right angles to them.

[Illustration: Courtesy of the "Scientific American"

FIG. 11. The radio compass turned parallel to an oncoming
electro-magnetic wave]

To find out where a sending-station is, the compass is turned until the
loudest sound is heard in the receiver and then the compass dial shows
from what direction the signals are coming. At the same time, another
line on the signals will be found by a second station with another
compass. These directions are traced on a map; and where they meet, the
sending-station must be located.

With this apparatus it was possible to locate the direction of the
station within a degree.

After the station had been located as closely as possible in this
way, a motor-truck was sent out in which there was a concealed radio
compass. The truck would patrol the region located by the fixed
compasses, and with it the position of the concealed station could be
determined with perfect accuracy. The building would be raided and its
occupants jailed and the radio equipment confiscated.

Even receiving-sets were discovered with the portable compass, but to
find them was a far more difficult task. For the receiving of messages
from distant points without a conspicuous aërial an audion would have
to be used and this would set up feeble oscillations which could be
picked up under favorable conditions by the portable compass.


PILOTING SHIPS INTO PORT

And now for the peace-time application of all this. If the compass
could be used to find those who tried to hide, why could it not also be
used to find those who wished to be found?

Every now and then a ship runs upon the rocks because it has lost its
bearings in the fog. But there will be no excuse for such accidents
now. A number of radio-compass stations have been located around the
entrance and approach to New York Harbor. Similar stations have been,
or soon will be, established at other ports. As soon as a ship arrives
within fifty or a hundred miles of port she is required to call for
her bearings. The operator of the control station instructs the ship
to send her call letters for thirty seconds, and at the same time
notifies each compass station to get a bearing on the ship. This each
does, reporting back to the control station. The bearings are plotted
on a chart and inside of two minutes from the time the ship gives her
call letters, her bearing is flashed to her by radio from the control
station.

[Illustration: Courtesy of the "Scientific American"

FIG. 12. Approaches to New York Harbor showing location of three radio
compass stations and how position of a ship sending signals from A may
be determined]

The chart on which the plotting is done is covered with a sheet of
glass. Holes are pierced through the glass at the location of each
compass station. See Fig. 12. On the chart, around each station,
there is a dial marked off in the 360 degrees of the circle. A thread
passes through the chart and the hole in the glass at each station.
These threads are attached to weights under the chart. When a compass
station reports a bearing, the thread of that station is pulled out and
extended across the corresponding degree on the dial. The same is
done as each station reports and where the threads cross, the ship must
be located.

Not only can the direction-finder be used to pilot a ship into a
harbor, but it will also serve to prevent collisions at sea, because
a ship equipped with a radio compass can tell whether another ship is
coming directly toward her.

And so as one of the happy outcomes of the dreadful war, we have an
apparatus that will rob sea-fogs of their terrors to navigation.



CHAPTER XI

WARRIORS OF THE PAINT-BRUSH


When the great European war broke out, it was very evident that the
Entente Allies would have to exercise every resource to beat the foe
which had been preparing for years to conquer the world. But who ever
imagined that geologists would be called in to choose the best places
for boring mines under the enemy: that meteorologists would be summoned
to forecast the weather and determine the best time to launch an
offensive; that psycologists would be employed to pick out the men with
the best nerves to man the machine-guns and pilot the battle-planes?
Certainly no one guessed that artists and the makers of stage scenery
would play an important part in the conflict.

But the airplane filled the sky with eyes that at first made it
impossible for an army to conceal its plans from the enemy. And then
there were eyes that swam in the sea--cruel eyes that belonged to
deadly submarine monsters, eyes that could see without being seen, eyes
that could pop up out of the water at unexpected moments, eyes that
directed deadly missiles at inoffensive merchantmen. They were cowardly
eyes, too, which gave the ship no opportunity to strike back at the
unseen enemy. A vessel's only safety lay in the chance that out in the
broad reaches of the ocean it might pass beyond the range of those
lurking eyes. It was a game of hide-and-seek in which the pursuer and
not the pursued was hidden. Something had to be done to conceal the
pursued as well, but in the open sea there was nothing to hide behind.


HIDING IN PLAIN SIGHT

There is such a thing as hiding in plain sight. You can look right at
a tree-toad without seeing him, because his colors blend perfectly
with the tree to which he is clinging. You can watch a green leaf
curl up and shrivel without realizing that the curled edge is really
a caterpillar, cunningly veined and colored to look just like a dying
leaf; and out in the woods a speckled bird or striped animal will
escape observation just because it matches the spotted light that
comes through the underbrush. Nature is constantly protecting its
helpless animals with colored coats that blend with the surroundings.

Long ago clumsy attempts at concealment were made when war-vessels
were given a coat of dark-gray paint which was supposed to make them
invisible at a distance. Actually the paint made them more conspicuous;
but, then, concealment did not count for very much before the present
war.

It was the eyes of the submarines that brought a hurry call for the
artists, and up to them was put the problem of hiding ships in plain
sight. A new name was coined for these warriors of the paint-brush:
_camoufleurs_ they were called, and their work was known as
_camouflage_.


MATCHING THE SKY

Of course, no paint will make a ship absolutely invisible at a short
distance, but a large vessel may be made to disappear completely from
view at a distance of six or seven miles if it is properly painted.

To be invisible, a ship must reflect as much light and the same shade
of light as do its surroundings. If it is seen against the background
of the sea, it must be of a bluish or a greenish tint, but a submarine
lies so low in the water that any object seen at a distance is
silhouetted against the sky, and so the ship must have a coat of paint
that will reflect the same colors as does the sky. Now, the sky may
be of almost any color of the rainbow, depending upon the position of
the sun and the amount of vapor or dust in the air. Fortunately in the
North Sea and the waters about the British Isles, where most of the
submarine attacks took place, the weather is hazy most of the time,
and the ship had to be painted of such a color that it would reflect
the same light as that reflected by a hazy sky. With a background of
haze and more or less haze between the ship and the periscope of the
U-boat, it was not a very difficult matter to paint a ship so that it
would be invisible six or seven miles away. One shade of gray was used
to conceal a ship in the North Sea and an entirely different shade was
used for the brighter skies of the Mediterranean.

[Illustration: (C) International Film

A Giant Gun Concealed Among Trees Behind the French Lines]

In this way, the artists made it possible for ships to sail in
safety much nearer the pursuer who was trying to find them, and by just
so much they reduced his powers of destruction. But still the odds were
too heavy against the merchantman. Something must be done for him when
he found himself within the seven-mile danger-zone. Here again the
artists came to the rescue.

[Illustration: (C) Committee on Public Information

Observing the Enemy from a Papier-Mâché Replica of a Dead Horse]

Before merchant ships were armed, a submarine would not waste a torpedo
on them, but would pound them into submission with shell. Even after
ships were provided with guns, submarines mounted heavier guns and
unless a ship was speedy enough to show a clean pair of heels, the
pursuing U-boat would stand off out of range of the ship's guns and
pour a deadly fire into it. But the ships, too, mounted larger guns and
the submarines had to fall back upon their torpedoes.


GETTING THE RANGE FOR THE TORPEDO

In order to fire its torpedo with any certainty, the U-boat had to get
within a thousand yards of its victim. A torpedo travels at from thirty
to forty miles per hour. It takes time for it to reach its target
and a target which is moving at, say, fifteen knots, will travel
five hundred yards while a thirty-knot torpedo is making one hundred
yards. And so before the U-boat commander could discharge his torpedo,
he had to know how fast the ship was traveling and how far away it
was from him. He could not come to the surface and make deliberate
observations, but had to stay under cover, not daring even to keep his
eye out of water, for fear that the long wake of foam trailing behind
the periscope would give him away. All he could do, then, was to throw
his periscope up for a momentary glimpse and make his calculations very
quickly; then he could move to the position he figured that he should
occupy and shoot up his periscope for another glimpse to check up his
calculations. On the glass of this periscope, there were a number of
graduations running vertically and horizontally. If he knew his victim
and happened to know the height of its smoke-stacks or the length of
the boat, he noted how many graduations they covered, and then by a set
formula he could tell how far he was from the boat. At the same time he
had to work out its rate of travel and note carefully the course it
was holding before he could figure where his torpedo must be aimed.

There was always more or less uncertainty about such observations,
because they had to be taken hastily, and the camoufleurs were not
slow to take advantage of this weakness. They increased the enemy's
confusion by painting high bow-waves which made the ship look as if it
were traveling at high speed. They painted the bow to look like the
stern, and the stern to look like the bow, and the stacks were painted
so that they appeared to slant in the opposite direction, so that it
would look as if the vessel were headed the other way. U-boats came to
have a very wholesome respect for destroyers and would seldom attack a
ship if one of these fast fighting-craft was about, and so destroyers
were painted on the sides of ships as scarecrows to frighten off the
enemy.


MAKING STRAIGHT LINES LOOK CROOKED

We say that "seeing is believing," but it is not very hard to deceive
the eye. The lines in Fig. 13 look absolutely parallel, and they are;
but cross-hatch the spaces between them, with the hatching reversed in
alternate spaces, as in Fig. 14, and they no longer look straight.
Take the letters on the left, Fig. 15. They look all higgledy-piggledy,
but they are really straight and parallel, as one can prove by laying
a straight-edge against them, or by drawing a straight line through
each letter, as shown at the right, Fig. 16. Such illusions were used
on ships. Stripes were painted on the hull that tapered slightly, from
bow to stern, so that the vessel appeared to be headed off at an angle,
when it was really broadside to the watcher at the other end of the
periscope.

[Illustration: FIG. 13. Parallel lines that look straight]

[Illustration: FIG. 14. Parallel lines that do not look straight]

[Illustration: Courtesy of the Submarine Defense Association

FIG. 15. Letters that look all higgledy-piggledy, but are really
straight]

There are color illusions, too, that were tried. If you draw a red
chalk-mark and a blue one on a perfectly clean blackboard, the red
line will seem to stand out and the blue one to sink into the black
surface of the board, because your eye has to focus differently for
the two colors, and a very dazzling effect can be had with alternating
squares of blue and red. Other colors give even more dazzling effects,
and some of them, when viewed at a distance, will blend into the very
shade of gray that will make a boat invisible at six miles. When
U-boat commanders took observations on a ship painted with a "dazzle"
camouflage, they saw a shimmering image which it was hard for them
to measure on the fine graduations of their periscopes. Some ships
were painted with heavy blotches of black and white, and the enemy
making a hasty observation would be apt to focus his attention on the
dark masses and overlook the white parts. So he was likely to make a
mistake in estimating the height of the smoke-stack or in measuring the
apparent length of a vessel.


A JOKE ON THE PHOTOGRAPHER

Early in the submarine campaign one of our boats was given a coat of
camouflage, and when the vessel sailed from its pier in the North
River, New York, the owners sent a photographer two or three piers down
the river to photograph the ship as she went by. He took the picture,
but when the negative was developed, much to his astonishment he found
that the boat was not all on the plate. In the finder of his camera,
he had mistaken a heavy band of black paint for the stern of the ship,
quite overlooking the real stern, which was painted a grayish white.
The artist had fooled the photographer and at a distance of not more
than two or three hundred yards!


SEEING BEYOND THE HORIZON

The periscope of a submarine that is running awash can be raised about
fifteen feet above the water, which means that the horizon as viewed
from that elevation is about six miles away, and if you draw a circle
with a six-mile radius on the map of the Atlantic, you will find that
it is a mere speck in the ocean; but a U-boat commander could see
objects that lay far beyond his horizon because he was searching for
objects which towered many feet above the water. The smoke-stacks of
some vessels rise a hundred feet above the water-line, and the masts
reach up to much greater altitudes. Aside from this, in the early days
of the war steamers burned soft coal and their funnels belched forth
huge columns of smoke which was visible from twenty to thirty miles
away.

When this was realized, efforts were made to cut down the
superstructure of a ship as much as possible. Some vessels had their
stacks cut down almost to the deck-line, and air-pumps were installed
to furnish the draft necessary to keep their furnaces going. They
had no masts except for slender iron pipes which could be folded
down against the deck and could be erected at a moment's notice, to
carry the aërials of the wireless system. Over the ship from stem to
stern was stretched, a cable, familiarly known as a "clothes-line,"
upon which were laid strips of canvas that completely covered the
superstructure of the ship. These boats lay so low that they could not
be seen at any great distance, and it was difficult for the U-boats to
find them. They were slow boats; too slow to run away from a modern
submarine, but because of their lowly structure, they managed to elude
the German U-boats. When they were seen, the U-boat commanders were
afraid of them. They were suspicious of anything that looked out of the
ordinary, and preferred to let the "clothes-line ships" go.

[Illustration: (C) Committee on Public Information

        From Western Newspaper Union

Camouflaged Headquarters of the American 26th Division in France]


THE BRITISH MYSTERY SHIPS

The Germans had some very unhealthy experiences with the "Q-boats"
or "mystery ships" of the British. These were vessels rigged up much
like ordinary tramp steamers, but they were loaded with wood, so that
they would not sink, and their hatches were arranged to fall open at
the touch of a button, exposing powerful guns. They also were equipped
with torpedo-tubes, so that they could give the U-boat a dose of its
own medicine. These ships would travel along the lanes frequented by
submarines, and invite attack. They would limp along as if they had
been injured by a storm or a U-boat attack, and looked like easy prey.
When a submarine did attack them, they would send out frantic calls for
help, and they had so-called "panic" parties which took to the boats.
Meantime, a picked crew remained aboard, carefully concealed from
view, and the captain kept his eye upon the enemy through a periscope
disguised as a small ventilator, waiting for the U-boat to come within
range of certain destruction. Sometimes the panic party would lure the
submarine into a favorable position by rowing under the stern as if to
hide around the other side of the ship. At the proper moment, up would
go the white ensign--the British man-of-war flag--the batteries would
be unmasked, and a hail of shell would break loose over the Hun. Many a
German submarine was accounted for by such traps.

[Illustration: (C) Underwood & Underwood

A Camouflaged Ship in the Hudson River on Victory Day]

Submarines themselves used all sorts of camouflage. They were
frequently equipped with sails which they would raise to disguise
themselves as peaceful sloops, and in this way they were able to steal
up on a victim without discovery. Sometimes they would seize a ship and
hide behind it in order to get near their prey.


CAMOUFLAGE ON LAND

But the call for the wielders of the paintbrush came not only from the
sea. Their services were needed fully as much on land, and the making
of land camouflage was far more interesting because it was more varied
and more successful. Besides, it called for more than mere paint; all
sorts of tricks with canvas, grass, and branches were used. Of course,
the soldiers were garbed in dust-colored clothing and shiny armor was
discarded. The helmets they wore were covered with a material that cast
no gleam of light. In every respect, they tried to make themselves of
the same shade as their surroundings. Like the Indians, they painted
their faces. This was done when they made their raids at night. They
painted their faces black so that they would not show the faintest
reflection of light.


A PAPER HORSE

The most interesting camouflage work was done for the benefit of
snipers or for observers at listening-posts close to the enemy
trenches. It was very important to spy on the enemy and discover his
plans, and so men were sent out as near his lines as possible, to
listen to the conversation and to note any signs of unusual activity
which would be likely to precede a raid. These men were supplied with
telephone wires which they dragged over No Man's Land, and by which
they could communicate their discoveries to headquarters. Some very
ingenious listening-posts were established. In one case a papier-mâché
duplicate of a dead horse was made, which was an exact facsimile of an
animal that had been shot and lay between the two lines. One night, the
carcass of the horse was removed and the papier-mâché replica took its
place. In the latter a man was stationed with telephone connection back
to his own lines. Here he had an excellent chance to watch the enemy.

On another occasion a standing tree, whose branches had been shot away,
was carefully photographed and an exact copy of it made, but with a
chamber inside in which an observer could be concealed. One night while
the noise of the workmen was drowned by heavy cannonading, this tree
was removed and its facsimile was set up instead, and it remained for
many a day before the enemy discovered that it was a fake tree-trunk.
It provided a tall observation post from which an observer could direct
the fire of his own artillery.


FOOLING THE WATCHERS IN THE SKY

In the early stages of the war, it seemed impossible to hide anything
from the Germans. They had eyes everywhere and were able to anticipate
everything the Allies did. But the spies that infested the sky were
the worst handicap. Even when the Allies gained control of the air,
the control was more or less nominal because every now and then an
enemy observer would slip over or under the patrolling aëroplanes and
make photographs of the Allies' lines. The photographs were carefully
compared with others previously taken, that the slightest change in
detail might be discovered. Airplane observers not only would be ready
to drop bombs on any suspicious object or upon masses of troops moving
along the roads, but would telephone back to their artillery to direct
its fire upon these targets. Of course, the enemy knew where the roads
were located and a careful watch was kept of them.

The French did not try to hide the roads, but they concealed the
traffic on the roads by hanging rows of curtains over them. As these
curtains hung vertically and were spaced apart, one would suppose that
they would furnish little concealment, but they prevented an observer
in an aëroplane from looking down the length of a road. All the road he
could see was that which lay directly under his machine, because there
he could look between the curtains; if he looked obliquely at the road,
the curtains would appear to overlap one another and would conceal
operations going on under them.

In one case, the Germans completely covered a sunken road with canvas
painted to represent a road surface. Under this canvas canopy, troops
were moved to an important strategic point without the slightest
indication of such a movement.


HIDING BIG GUNS

Nature's tricks of camouflage were freely used in the hiding of the
implements of war on land. Our big guns were concealed by being painted
with leopard spots and tiger stripes, the color and nature of the
camouflage depending upon the station they were to occupy. In many
cases, they were covered with branches of trees or with rope netting
overspread with leaves. So careful was the observation of the air
scouts that even the grass scorched by the fire of the gun had to be
covered with green canvas to prevent betrayal of the position of the
gun.


ROADS THAT LED NOWHERE

In the making of an emplacement for a gun it was of the utmost
importance that no fresh upturned earth be disclosed to the aërial
observers. Even foot-paths leading to it had to be concealed. Plans
were carefully made to cover up all traces of the work before the work
was begun. Where it was impossible to conceal the paths, they were
purposely made to lead well beyond the point where the emplacement was
building, and, still further to deceive the enemy, a show of work was
sometimes undertaken at the end of the path. Wherever the sod had to
be upturned, it was covered over with green canvas. The earth that was
removed had to be concealed somewhere and the best place of concealment
was found to be some old shell-hole which would hold a great deal of
earth without any evidence that would be apparent to an observer in an
aëroplane. If no shell-hole were handy, the excavated material had to
be hauled for miles before a safe dumping-ground could be found. As far
as possible everything was sunk below the earth level. Big pits were
dug in which the mortars were placed, or if a shell-hole were empty,
this was used instead.


SHADOWLESS BUILDINGS

Any projection above the ground was apt to cast a shadow which would
show up on the observer's photographs. This was a difficulty that was
experienced in building the hangars for airplanes. The roofs of these
sheds were painted green so as to match the sod around them, but as
they projected above their surroundings, they cast shadows which made
them clearly evident to the enemy. This was overcome by the building
of shadowless hangars; that is, hangars with roofs that extended all
the way to the ground at such an angle that they would cause no shadow
except when the sun was low. In some cases, aëroplanes were housed in
underground hangars, the approach to which was concealed by a canvas
covering. As for the machines themselves, they scorned the use of
camouflage. Paint was little protection to them. Some attempt was made
to use transparent wings of _cellon_, a material similar to celluloid,
but this did not prove a success.


THE PHOTOGRAPHIC EYE

Although camoufleurs made perfect imitations of natural objects and
surroundings, they were greatly concerned to find that the flying
observers could see through their disguises. To the naked eye the
landscape would not show the slightest trace of any suspicions object,
but by the use of a color-screen to cut out certain rays of light, a
big difference would be shown between the real colors of nature and
the artist's copies of them. For instance, if a roof painted to look
like green grass were viewed through a red color-screen, it would look
brown; while the real grass, which apparently was of exactly the same
shade as the roof, would look red. It had not been realized by the
artists who had never studied the composition of light, that there is
a great deal of red in the green light reflected by grass, and that if
they were to duplicate this shade of green, they must put a certain
amount of red paint in their imitation grass roofs. Air scouts did not
depend upon their eyes alone, but used cameras so that they could study
their photographs at their leisure and by fitting the cameras with
different color-screens, they could analyze the camouflage and undo the
patient work of the artist.


A CALL FOR THE PHYSICIST

To meet this situation, another man was summoned to help--the
physicist, who looks upon color merely as waves of ether; who can pick
a ray of light to pieces just as a chemist can analyze a lump of sugar.
Under his expert guidance, colors of nature were imitated so that they
would defy detection. Aside from this, the physicist helped to solve
the tricks of the enemy's camoufleurs.

But the physicist had barely rolled up his sleeves and got into the
fray when the armistice was signed which put an end to the shams as
well as to the realities of the great war. While the work of camouflage
was not completed, we owe an inestimable debt to the men who knew how
to fake scenery and to their learned associates who count the wave
lengths of light, and although their trade was a trade of deception and
shams, there was no sham about the service they rendered.


MAKING SHIPS VISIBLE

While in war safety lies in invisibility, in peace the reverse is
true. Now that the war is over, it may seem that the work of the
camoufleurs can find no useful application; but it was impossible
to learn how to make objects invisible without also learning how to
make them conspicuously visible. As a consequence, we know now how to
paint a ship so that it will show up more clearly in foggy weather,
thereby reducing the danger of collision. We know, too, how to paint
light-ships, buoys, etc., so that they will be much more conspicuous
and better guides to mariners, and how to color railroad signals
and road signs so that they will be more easily seen by locomotive
engineers and automobile drivers.



CHAPTER XII

SUBMARINES


It was an American invention that dragged America into the war--an
American invention in the hands of barbarians and put to unspeakably
barbarous use.

After seeing how the Huns used the submarine we are not so sure that
we can take much pride in its invention. But if any blame attaches to
us for developing the submarine, we made amends by the way in which we
fought the German U-boat and put an end to German frightfulness on the
sea. Of course, the credit for Germany's defeat is not for a moment
claimed by Americans alone, but it must be admitted that we played an
important part in overcoming the menace of the U-boat.

There is no question that the submarine was an American invention.
To be sure, we can look into ancient books and find suggestions for
navigating under the surface of the sea, but the first man who did
actually build a successful submarine was David Bushnell, back in
the Revolutionary War. After him came Robert Fulton, who carried the
invention farther. He built and operated a submarine for the French
Government, and, in more recent years, the submarine became a practical
vessel of war in the hands of John P. Holland and Simon Lake, both
Americans. However, we are not interested, just now, in the history of
the submarine, but rather in the development of this craft during the
recent war.

With Great Britain as an enemy, Germany knew that she was hopelessly
outclassed on the sea; but while "Britannia ruled the waves," she did
not rule the depths of the sea, and so Germany decided to claim this
realm for her own. Little attention did she pay to surface vessels.
Except in the Dogger Bank engagement and the Battle of Jutland, the
German first-class vessels did not venture out upon the open sea, and
even the lighter craft merely made occasional raids under cover of
fog or darkness, only to cut and run as soon as the British vessels
appeared. The submarine boat, or _unterseeboot_ as the Germans called
it, was virtually the only boat that dared go out into the high seas;
consequently, the Germans specialized upon that type of craft and under
their close attention it grew into a highly perfected war-vessel. But
the Germans were not the only ones to develop the submarine, as we
shall see.


CONSTRUCTION OF THE U-BOATS

When the great war broke out, the German U-boat was a comparatively
small craft, less than 150 feet long, with its main hull only 12 feet
in diameter. It could make a speed of 12 knots on the surface and only
9 when submerged. But as the war progressed, it grew larger and larger,
until it attained a length of over 300 feet and its speed was increased
to 12 knots when submerged and 18 knots on the surface.

Figs. 16 to 18 show the construction of one of the early U-boats. The
later boats were built after the same general plan, but on a bigger
scale.

[Illustration: Courtesy of the "Scientific American"

FIG. 16. Sectional view of one of the earlier German U-Boats]

[Illustration: Courtesy of the "Scientific American"

FIG. 17. Sectional plan view of a German U-Boat of the type used at the
beginning of the war]

It is not always safe to judge a thing by its name; to do so is apt to
lead to sad mistakes. One would naturally suppose, from its name, that
a submarine is a boat that lives under water, like a fish. But it is
not a fish; it is an air-breathing animal that prefers to stay on the
surface, only occasionally diving under to hide from danger or to steal
upon its prey. During the war, the German U-boats did not average three
hours per day under the surface! Because they were intended to run on
the surface they had to be built in the form of a surface vessel, so as
to throw off the waves and keep from rolling and pitching too much in a
seaway. But they also had to be built to withstand the crushing weight
of deep water, and as a cylinder is much stronger than a structure of
ordinary boat shape, the main hull was made circular in section and of
heavy plating, strongly framed, while around this was an outer hull of
boat shape, as shown in Fig. 18.


PUTTING HOLES IN A TANK TO KEEP IT FULL

The space between the inner and outer hulls was used for water ballast
and for reservoirs of oil to drive the engines; and, strange as it
may seem, the oil-tanks were always kept full by means of holes in
the bottom of them. As the oil was consumed by the engines, water
would flow into the reservoir to take its place, and the oil, being
lighter than water, would float on top. The false hull was of light
metal, because as it was open to the sea, the pressure on the inside
was always the same as that on the outside. The reservoirs of oil
and the water-ballast tanks protected the inner hull of the vessel
from accidental damage and from hostile shell and bombs. There were
water-ballast tanks inside the inner hull as well, as shown in the
cross-sectional view, Fig. 18. The water in the ballast-tanks was blown
out by compressed air to lighten the U-boat and the boat was kept on an
even keel by the blowing out or the letting in of water in the forward
and after tanks.

[Illustration: Courtesy of the "Scientific American"

FIG. 18. Transverse section through conning-tower, showing the interior
(circular) pressure-resisting hull and the lighter exterior hull, which
is open to the sea]

A heavy lead keel was attached to the bottom of the boat, to keep it
from rolling too much. In case of accident, if there were no other way
of bringing the boat to the surface, this keel could be cast loose.

At the forward end, where the torpedo-tubes were located, there was a
torpedo-trimming tank. Torpedoes are heavy missiles and every time one
was discharged the boat was lightened, and the balance of the submarine
was upset. To make up for the loss of weight, water had to be let into
the torpedo-trimming tank.

A submarine cannot float under-water without swimming; in other words,
it must keep its propellers going to avoid either sinking to the bottom
of the sea or bobbing up to the surface. To be sure, it can make itself
heavier or lighter by letting water into or blowing water out of its
ballast-tanks, but it is impossible to regulate the water ballast so
delicately that the submarine will float submerged; and should the boat
sink to a depth of two hundred feet or so, the weight of water above it
would be sufficient to crush the hull, so it is a case of sink or swim.
Usually enough ballast is taken on to make the submarine only a little
lighter than the water it displaces; and then to remain under, the
vessel must keep moving, with its horizontal rudders tilted to hold it
down. The horizontal rudders or hydroplanes of the U-boat are shown in
Fig. 17, both at the bow and at the stern.

The main hull of the vessel was literally filled with machinery. In
the after part of the boat were the Diesel oil-engines with which the
U-boat was propelled when on the surface. There were two engines, each
driving a propeller-shaft. It was impossible to use the engines when
the vessel was submerged, not because of the gases they produced--these
could easily have been carried out of the boat--but because every
internal-combustion engine consumes enormous quantities of air. In a
few minutes the engines would devour all the air in the hull of the
submarine and would then die of suffocation. And so the engines were
used only when the submarine was running awash or on the surface, and
then the air consumed by them would rush down the hatchway like a
hurricane to supply their mighty lungs.


ENGINES THAT BURN HEAVY OIL

The oil-engines were strictly a German invention. In the earlier
days of the submarine gasolene-engines were used, but despite every
precaution, gasolene vapors occasionally would leak out of the
reservoirs and accumulate in pockets or along the floors of the hull,
and it needed but a spark to produce an explosion that would blow up
the submarine. But Rudolph Diesel, a German, invented an engine which
would burn heavy oils.

[Illustration: (C) Underwood & Underwood

Complex Mass of Wheels and Dials inside a German Submarine]

In the Diesel engine there are no spark-plugs and no magneto: the
engine fires itself without electrical help. Air is let into the
cylinder at ordinary atmospheric pressure, or fifteen pounds per square
inch. But it is compressed by the upward stroke of the piston to
about five hundred pounds per square inch. When air is compressed it
develops heat and the sudden high compression to over thirty times its
normal pressure raises the temperature to something like 1000 degrees
Fahrenheit. Just as this temperature is reached, a jet of oil is blown
into the cylinder by air under still higher pressure. Immediately the
spray of oil bursts into flame and the hot gases of combustion drive
the piston down. Because of the intense heat almost any oil, from light
gasolene to heavy, almost tarlike oils, can be used. As heavy oils do
not throw off any explosive vapors unless they are heated, they make a
very safe fuel for submarines.

[Illustration: Photograph by International Film Service

Surrendered German Submarines, showing the Net Cutters at the Bow]

To drive the U-boat when no air was to be had for the engines,
electric motors were used. There was one on each propeller-shaft and
the shafts could be disconnected from the oil-engines when the motors
were driving. The motors got their power from storage batteries in the
stern of the submarine and under the floors forward. The motors when
coupled to and driven by the engines generated current which was stored
in the storage batteries. The submarine could not run on indefinitely
underwater. When its batteries were exhausted it would have to come
to the surface and run its engines to store up a fresh charge of
electricity. The electric motors gave the boat a speed of about nine
knots.

In addition to the main engines and motors, there was a mass of
auxiliary machinery. There were pumps for compressing air to blow the
ballast-tanks and to discharge the torpedoes. There was a special
mechanism for operating the rudder and hydroplanes, and all sorts of
valves, indicators, speaking-tubes, signal lines, etc. The tiny hull
was simply crammed with mechanism of all kinds and particularly in the
early boats there was little room for the accommodation of the officers
and crew. The officers' quarters were located amidships, and forward
there were the folding berths of the crews. In the later boats more
space was given the men. The large U-boats carried a crew of forty and
as the hazards of submarine warfare increased, more attention had to be
paid to the men.


FAT MEN NOT WANTED

Oddly enough, small, slender men were preferred for submarine duty, not
because of lack of space, but because it was apt to be very cold in a
submarine, particularly in the winter-time. The water cooled off the
boat when the submarine was traveling submerged, and the motors gave
off little heat; while when the vessel was running on the surface the
rush of wind to supply the engines kept the thermometer low. This meant
that the men had to pile on much clothing to keep warm, which made
them very bulky. The hatchway was none too large and a fat man, were
he bundled up with enough clothing to keep him warm, would have a hard
time squeezing through.

In the center of the vessel was the main hatchway, leading up to the
conning-tower, which was large enough to hold from three to five men.
This was the navigating-room when the vessel was running submerged,
and above it was the navigating-bridge, used when the submarine was on
the surface. In the conning-tower there was a gyroscopic compass; a
magnetic compass would not work at all inside the steel hull of the
U-boat. And here were the periscopes or eyes of the submarine, rising
from fifteen to twenty feet above the roof of the conning-tower. There
were usually two periscopes. They could be turned around to give the
man at the wheel a view in any direction and they were used sometimes
even when the vessel was running on the surface, to give a longer range
of vision.


THE BLINDNESS OF THE SUBMARINE

Now, a submarine cannot see anything underwater. The commander cannot
even see the bow of his boat from the conning-tower, and until he
gets near enough to the surface to poke his periscope out of water
he is absolutely blind and must feel his way about with compass and
depth-gage. It was always an anxious moment for the U-boat commander,
when he was coming up, until his periscope broke out of the water and
he could get his bearings; and even that was attended with danger,
for his periscope might be seen. Of course a periscope is a very
insignificant object on the broad sea, but when a submarine is moving
its periscope is followed by a wake which is very conspicuous, and so
the U-boat ran a chance of being discovered and destroyed before it
could dive again to a safe depth. Later, telescoping periscopes were
used, which could be raised by means of a hand-lever. The submarine
would run along just under the surface and every now and then it would
suddenly raise its periscope for an observation and drop it down again
under cover if there was danger nigh. This was much simpler and quicker
than having a six-or eight-hundred-ton boat come up to the surface and
dive to safety. He might even collide with a vessel floating on the
surface, but to lessen this danger submarines were furnished with ears
or big microphone diaphragms at each side of the hull by which a ship
could be located by the noise of its propellers.

In the bow were the torpedo-tubes and the magazine of torpedoes. At
first there were only two torpedo-tubes, but later the number was
increased to four. These were kept constantly loaded, so that the
projectiles could be launched in rapid succession, if necessary,
without a pause for the insertion of a fresh torpedo. In some
submarines tubes were provided in the stern also so that the boat could
discharge a torpedo at its enemy while running away from him.

Each tube was closed at the outer end by a cap and at the inside end
by a breech-block. The tube was blown clear of water by means of
compressed air, and of course the outer cap was closed when the breech
was open to let in a torpedo. Then the breech was closed, the cap
opened, and the torpedo was discharged from the tube by a blast of air.


THE TORPEDO

A torpedo is really a motor-boat, a wonderfully constructed boat,
fitted with an engine of its own that is driven by compressed air
and which drives the torpedo through the water at about forty miles
per hour. The motor-boat is shaped like a cigar and that used by the
Germans was about fifteen feet long and fourteen inches in diameter. We
used much larger torpedoes, some of them being twenty-two feet long.
Ours have a large compressed-air reservoir and will travel for miles;
but the Germans used their torpedoes at short ranges of a thousand
yards and under, cutting down the air-reservoir as much as possible
and loading the torpedo with an extra large explosive charge.

We found in the Diesel engine that when air is highly compressed it
becomes very hot. When compressed air is expanded, the reverse takes
place, the air becomes very cold. The air that drives the motor of the
torpedo grows so cold that were no precautions taken it would freeze
any moisture that might be present and would choke up the engine
with the frost. And so an alcohol flame is used to heat the air. The
air-motor is started automatically by release of a trigger as the
torpedo is blown out of the torpedo-tube. By means of gearing, the
motor drives two propellers. These run in opposite directions, so as to
balance each other and prevent any tendency for the torpedo to swerve
from its course. The torpedo is steered by a rudder which is controlled
by a gyroscope, and it is kept at the proper depth under water by
diving-rudders which are controlled by a very sensitive valve worked
by the weight of the water above it. The deeper the water, the greater
the weight or pressure; and the valve is so arranged that, should the
torpedo run too far under, the pressure will cause the diving-rudders
to tilt until the torpedo comes up again; then if the torpedo rises
too high, the valve will feel the reduction of pressure and turn the
rudders in the other direction.

The business end of a torpedo is a "war-head" packed with about four
hundred pounds of TNT. At the nose of the torpedo is a firing-pin,
with which the war-head is exploded. Ordinarily, the firing-pin does
not project from the torpedo, but there is a little propeller at the
forward end which is turned by the rush of water as the torpedo is
driven on its course. This draws out the firing-pin and gets everything
ready for the TNT to explode as soon as the firing-pin is struck. But
the firing-pin is not the only means of exploding the torpedo. Inside
there is a very delicate mechanism that will set off the charge at the
least provocation. In one type of torpedo a steel ball is provided
which rests in a shallow depression and the slightest shock, the
sudden stopping or even a sudden swerve of the torpedo, would dislodge
the ball and set off the charge. Hence various schemes, proposed by
inventors, for deflecting a torpedo without touching the firing-pin,
would have been of no value at all.


GUNS ON SUBMARINES

As torpedoes are expensive things, the U-boats were supplied with
other means of destroying their victims. The Germans sprang a surprise
by mounting guns on the decks of their submarines. At first these
were arranged to be lowered into a hatch when the boat was running
submerged, but later they were permanently mounted on the decks so that
they would be ready for instant use. They were heavily coated with
grease and the bore was swabbed out immediately when the boat came to
the surface, so that there was no danger of serious rust and corrosion.
The 3-inch gun of the early months of the war soon gave way to heavier
pieces and the latest U-boats were supplied with guns of almost 6-inch
caliber and there was a gun on the after deck as well as forward.

The U-boats depended upon radiotelegraphy to get their orders and
although they did not have a very wide sending-range, they could
receive messages from the powerful German station near Berlin. The
masts which carried the radio aërials could be folded down into
pockets in the deck. From stem to stern over the entire boat a cable
was stretched which was intended to permit the U-boat to slide under
nets protecting harbor entrances, and in later boats there were
keen-toothed knives at the bow which would cut through a steel net.
During the war German and Austrian U-boats occupied so much attention
that the public did not realize the part that the Entente Allies were
playing under the sea. America, Great Britain, France, and Italy
made good use of submarines, operating them against enemy vessels,
blockading enemy ports, and actually fighting enemy submarines.


A STEAM-DRIVEN SUBMARINE

The British in particular did splendid work with the submarine and
developed boats that were superior to anything turned out by the
Germans. For instance, they developed a submarine which is virtually a
submersible destroyer. It is 340 feet long and it can make a speed of
24 knots on the surface. The most remarkable part of this boat is that
its engines are driven by steam. Its boilers are fired with oil fuel.
There are two smoke-stacks which fold down when it submerges. Of course
when running under-water the vessel is driven by electricity and it
makes a speed of 10 knots. It carries three 4-inch guns, two forward
and one aft, and its displacement submerged is 2700 tons as against 800
tons for the largest German submarines.


A SUBMARINE THAT MOUNTS A TWELVE-INCH GUN

Still more remarkable is the big "super-submarine" designed by the
British to bombard the forts of the Dardanelles, but unfortunately it
was built too late to be used there. This submarine carries a gun big
enough for a battle-ship. It is of 12-inch caliber and weighs 50 tons.
Of course a big gun like that could not be fired athwart the submarine.
It might bowl the little vessel over, even though it was a 1700-ton
submarine. The gun is mounted to fire fore and aft, with a deviation
of only a few degrees to one side or the other, so that the shock of
the recoil is taken by the length instead of the beam of the submarine.
It fires a shell weighing 620 pounds and a full charge is not used,
so that the extreme range is only about 15,000 yards. This submarine
monitor would have been a very difficult target for the Turkish
gunners to hit.

When the war came to an end and the German submarines surrendered to
the Entente Allies at Harwich, there was considerable public curiosity
as to whether or not an examination of the U-boats would disclose any
wonderful secrets. But they contained nothing that the Allies did not
already know, and one British officer stated that the plans of the
German submarines had often fallen into their hands long before a
U-boat of the same type was captured!



CHAPTER XIII

GETTING THE BEST OF THE U-BOAT


The U-boat commander who sallied forth from the harbor of Wilhelmshaven
in the early days of the war had nothing to fear. He was out to murder,
not to fight. His prey was always out in the open, while he could kill
without exposing more than his eye above water. Not even a sporting
chance was allowed his victims, particularly when he chose unarmed
merchantmen for his targets. He could come up boldly to the surface
and shell a ship into submission. This was cheaper than torpedoing
the vessel, because torpedoes are expensive. If the ship were speedy
it might run away; or if the U-boat came up too close to its intended
prey, the latter might run it down. That happened occasionally and it
was the only danger that the _Herr Kommandant_ had to fear.

If a destroyer suddenly appeared, the U-boat could dive into the
shelter of the sea. If the water were not too deep, it could lie on
the bottom for two or more days if need be. There was plenty of air in
the hull to sustain life for many hours, and then the compressed air
used for blowing the ballast-tanks could be drawn upon. In the U-boat
there were potash cartridges to take up the carbon-dioxide, and tanks
of pure oxygen to revitalize the air. If the submarine were damaged,
it was not necessary for it to come to the surface to effect repairs.
There were air-locks through which a diver could be let out of the
boat. He was fitted with oxygen and potash cartridges, so that he did
not need to be connected by an air-hose with the boat, but could walk
around it freely to mend injured rudders or to clear the propeller of
entanglements.

Even the small submarines of those early days were capable of taking
long voyages. Setting his course at a comfortable pace of 10 knots, the
U-boat commander could count on enough fuel to carry him 1600 miles,
and if need be he could slow down to 8 knots and by using certain of
his water-ballast tanks for additional oil-reservoirs, extend his
cruising-radius to nearly 3000 miles. The big 800-ton U-boats that
were built later had a radius of 5000 miles at an 8-knot speed. And so
when the British closed the English Channel with nets and mines, _Herr
Kommandant_ was not at all perturbed; he could sail around the British
Isles if he chose and make war upon transatlantic shipping. When
harbors were walled off with nets, he could remain outside and sink
vessels that were leaving or entering them.


SUBMARINE-CHASERS

A real menace came when the U-boat commander popped his periscope out
of the sea and saw several little motor-boats bearing down upon him.
They seemed harmless enough, but a moment's inspection showed them
to be armed with guns fully as powerful as those he carried. It was
useless to discharge a torpedo at so speedy and small a foe. A torpedo
has to have a fairly deep covering of water, else its course will be
disturbed by surface waves; and the submarine-chasers drew so little
water that a torpedo would pass harmlessly under them. It was useless
for the U-boat commander to come up and fight them with his guns. They
would have been upon him before he could do that, and their speed and
diminutive size made them very difficult targets to hit. Besides, he
dared not risk a duel of shell, for he knew that if the precious inner
hull of his boat were punctured, he could not seek refuge under water;
and if he could not hide, he was lost. The little armed mosquito craft
swarmed about the harbor entrances, ready to dash at any submarine that
showed itself. They could travel twice as fast as the submarine when
it was submerged and half again as fast as when it was running on the
surface.

Submarines had to take to cover when these chasers were about. _Herr
Kommandant_ did not even dare to take a look around through his
periscope, because the streak of foam that trailed in its wake would
betray him and immediately the speedy motor-boats would take up the
chase; and they had a disagreeable way of dropping bombs which, even
if they did not sink the submarine, might produce such a concussion as
to spring its seams. His foes had discovered one of his most serious
defects. He was blind under-water and they were making the most of this
handicap.

[Illustration: (C) Underwood & Underwood

Forward End of a U-boat. Note the Four Torpedo Tubes Behind the Officer]

Groping along under-water by dead-reckoning was not any too safe a
procedure near land, because he was liable at any moment to crash into
an uncharted rock or maybe into the wreck of some submarine victim. He
could not correct his bearings without coming to the surface, and, in
the black depths of the sea, a slight miscalculation might send him
to his doom. As was explained in the previous chapter, he had to keep
moving, because he could not remain suspended under water.

[Illustration: (C) Press Illustrating Service

A Depth-bomb Mortar and a Set of "Ash Cans" at the Stern of an American
Destroyer]

He was more helpless than a ship sailing in the densest of fogs. A ship
can stop and listen to sound-signals, or even to the beating of the
surf on the shore, or it can take soundings to locate its position; and
yet it is no uncommon occurrence for a ship to run ashore in a fog. How
much easier it is for a submarine to lose its bearings when obliged to
travel by dead-reckoning, particularly in the disconcerting excitement
of the chase! To avoid the danger of collision with surface vessels,
the commander chose to run at a depth of sixty-five feet. That was the
upper limit of his safety-zone. A depth of over two hundred feet was
his lower limit, because, as stated before, the water-pressure at that
depth would crush in his hull or at least start its seams. If the
bottom were smooth and sandy, and not too deep, he could settle gently
upon it and wait for darkness, to make his escape.

But while he lay on a sandy bottom, he was still in danger. Trawlers
were sweeping the bottom with nets. He might be discovered; and then if
he did not come up and surrender, a bomb would let in the sea upon him.


A HINT FROM NATURE

While he could not see under water, his adversaries could. They had
taken a hint from nature. The fish-hawk has no difficulty in spying
his submarine prey. Flying high above the water, he can see his
victims at a considerable depth, and wait his chance to pounce upon
an unwary fish that comes too near the surface. It is said that the
British trained sea-gulls to hunt submarines. Sea-gulls will follow a
ship far out to sea for the sake of feeding on refuse that is thrown
overboard. British submarines encouraged the birds to follow them, by
throwing out bait whenever they came to the surface. Of course the
birds could see the submarine even when it was submerged, and if they
pursued it, they were always rewarded with plenty of food. The gulls
drew no fine distinction between Hun and Briton, and so it came that
_Herr Kommandant_ often groped his way along in the dark sea, totally
oblivious of the fact that he was attended by an escort of feathered
folk who kept the British chasers informed of his presence.

In this connection it is interesting to note that the British trained
sea lions to hunt submarines. The animals were taught at first to swim
to a friendly submarine, locating it by the sound of its propellers.
They were always rewarded with fish. These sea lions were muzzled so
that they could not go fishing on their own account. Then they learned
to locate enemy submarines and pointed them out by swimming directly
toward them and diving down to them.

But there were human eyes, as well, that spied upon the U-boat. Fast
seaplanes patrolled the waters, searching constantly for any trace of
submarine. Its form could be vaguely outlined to a depth of from fifty
to seventy-five feet, unless the sea were choppy, and once it was
discovered, chasers or trawlers were signaled to destroy it with bombs
or to entangle it in nets. Often a submarine would be discovered by a
leak in its oil-tank which would leave a tell-tale trail. Sometimes
when the U-boat itself could not be discerned, there would be slight
shimmer, such as may be seen above a hot stove, caused by refraction of
light in its wake. This was easily recognized by trained observers.

[Illustration: (C) Press Illustrating Service

A Depth-bomb Mortar in Action and a Depth-bomb snapped as it is being
hurled through the air]

Even better aërial patrols were the small dirigibles known as Blimps.
They are a cross between a balloon and an airplane, for they have the
body and the power-plant of an airplane, but the planes are replaced by
a gas-bag. Blimps could cruise leisurely and search the sea thoroughly.
They could stop and hover directly over a submarine and drop explosives
upon it with great accuracy. And so _Herr Kommandant_ could take no
comfort in hiding under a blanket of waves unless the blanket were so
thick as to conceal his form completely from the eyes overhead. This
made it imperative to leave the shallower waters near shore and push
out into the deep sea, where the small chasers could not pursue him.
But he could not shake off his pursuers. Stream-trawlers are built
to ride the heaviest gales and they took up the chase out into the
ocean.

[Illustration: Courtesy of "Scientific American"

Airplane Stunning a U-boat with a Depth-bomb]

There was a decided advantage for the U-boat in moving out to sea. It
had a wider field of activity and could more easily escape from its
pursuers. But on the other hand, its prey also had an advantage. Out in
the open ocean they were not obliged to follow the usual ship lanes and
it was more difficult for a submarine to intercept them. There it took
more U-boats to blockade a given area.


A GAME OF HIDE-AND-SEEK

Then, it ceased to be quite so one-sided a game when merchantmen began
to carry guns. That made it necessary for the submarine commander to
creep up on his victims stealthily, and depend upon his torpedoes. He
had to get within a thousand yards of the ship and preferably within
five hundred yards, in order to be sure of hitting it. If the ship
could travel faster than he could, he had to do this without betraying
his presence. But ship-captains soon learned that their safety lay in
zig-zagging. When _Herr Kommandant_ reached the point from which he
had planned to attack, he would raise his telescopic periscope out of
the water, expecting to see his victim within good torpedo range, only
to find it sailing safely on another tack. Again, he would have to take
observations and make another try, probably with no better luck. It was
a game of hide-and-seek in which the merchant ship had a good chance of
making its escape, particularly when blotches of camouflage paint made
it difficult for him to get the range, as described in Chapter XI.

[Illustration: Courtesy of the Submarine Defense Association

FIG. 19. How a ship hid behind smoke produced on its own stern, with
different directions of wind]

Slower ships could be attacked without all this manoeuvering, provided
the submarine's guns outranged those of the ship. And so U-boats
were provided with larger and larger guns, which made it possible
for them to stand off and pound the merchantmen while out of reach
of the vessel's guns. But ships found a way of hiding on the surface
of the sea. A vessel would spout forth volumes of dense black smoke
which would obliterate it from view. (See Fig. 19.) If the wind was
quartering, the ship would change its course and dodge behind the
sheltering pall of smoke. Not only was the smoke produced on the
vessel itself, but smoke-boxes were cast overboard to form a screen
behind the vessel. These smoke-boxes contained a mixture of coal-tar
and phosphorus and other chemicals which would produce incomplete
combustion. They were ignited by the rubbing of a phosphorus compound
on a priming-composition, and then cast adrift to pour out dense
volumes of heavy smoke. (See Fig. 20.) Behind this screen, the ship
could dodge and zig-zag and if her speed were greater than that of the
submarine, her chances of escape were very good.

[Illustration: Courtesy of the Submarine Defense Association

FIG. 20. How a ship hid behind a screen of smoke produced by throwing
smoke-boxes overboard]

Another annoyance that _Herr Kommandant_ experienced was, when he
lifted his periscopic eye above water, to find it so smeared with a
sticky substance that he could not see. His foes had strewn the water
with tar-oil that had spread in a thin film over a surface miles in
extent. This blinded him at first, but before long he was equipped
with a jet for washing off the periscope glass and that little
annoyance was overcome.

But the craft most dreaded by the U-boat commander were the destroyers.
These light, high-powered, heavily armed vessels could travel twice as
fast as he could on the surface and three times as fast as he could
submerged. Shells were invented which would not ricochet from the
surface of the sea, but would plow right through the water, where they
struck and hit the submarine below water-level.


DEATH-DEALING "ASH CANS"

However, it was not shell-fire that he dreaded, but the big "ash cans"
loaded with TNT which were timed to explode far under water, and which
would crush his boat or start its seams. It was not necessary for these
bombs to hit the U-boat. When they went off they would send out a wave
of pressure that would crush the boat or start its seams even if it
were a hundred feet and more from the point of the explosion. Within
limits, the deeper the explosion the wider would its destructive area
be.

The timing-mechanism of some depth bombs consisted merely of a float
on the end of a cord. When the bomb was thrown overboard this float
remained on the surface until the cord was pulled out to its full
length, when there would be a yank on the firing-trigger and the charge
would explode. In other depth bombs there was a valve operated by the
pressure of the water. When the bomb sank to the depth for which the
valve was set, the pressure of the water would force the valve in,
exploding a cartridge which set off the charge. So powerful were these
depth bombs that the destroyer had to travel at high speed to get out
of range of the explosion.

Depth bombs were rolled off the stern of the destroyer and also thrown
out from the sides of the vessel by means of mortars. Some of the
mortars were Y-shaped and held a depth bomb in each arm of the Y. When
a blank 3-inch shell was exploded at the base of the gun, both bombs
would be hurled from the ship, one to port and the other to starboard.
In this way the destroyer could drop the bombs in a "pattern" of wide
area. _Herr Kommandant_ gained a wholesome respect for these terriers
of the sea. It was suicide to show himself anywhere near a destroyer.
In a moment the speedy boat would be upon him, sowing depth bombs
along his course. His chances of escaping through this hail of high
explosives were remote indeed.

The ships that he was most eager to destroy were either too speedy for
him to catch, unless they happened to come his way, or else they were
herded in large convoys protected by these dreaded destroyers. The
convoy proved a most baffling problem for _Herr Kommandant_. He dared
not attack the convoy by daylight. In a fog he might take a chance at
picking off one of the ships, but even that was very risky. He could
trail the convoy until dusk and then under cover of darkness draw near
enough to discharge a torpedo, but in the daytime he must keep his
distance because there were eyes in the sky watching for him. At the
van and rear of the convoy there were kite balloons high in the sky,
with observers constantly watching for periscopes, and for U-boats that
might be lurking under the surface.

As the destroyers gained in experience, the difficulties of the U-boat
attack grew greater and its work grew more and more perilous. The crew
grumbled and grew mutinous. The morale of the men was shaken. We can
imagine the horror of plunging hurriedly into the depths of the sea,
and rushing along blindly under the surface, dodging this way and that,
while terrific explosions of depth bombs stagger the submarine and
threaten to crush it, and there is the constant expectation that the
next explosion will tear the thin shell of the U-boat and let in the
black hungry water. The tables were turned. Now, if never before, _Herr
Kommandant_, the hunter, knew what it felt like to be hunted.

[Illustration: (C) Underwood & Underwood

The False Hatch of a Mystery Ship and--]

[Illustration: The same Hatch opened to disclose the 3-Inch Gun and
Crew]

It takes an exceptional man to go through such a harrowing experience
with unshattered nerves. On at least one occasion, a submarine that
was being depth-bombed came suddenly to the surface. The hatch flew
open and the crew rushed out, holding up their hands and crying,
"_Kamerad_." The U-boat was uninjured, but the shock of a depth bomb
explosion had put the electric-lighting system out of commission, and
the crew, unnerved by the explosion and terrified by the darkness, had
overpowered their officers and brought the boat to the surface.

[Illustration: A French Hydrophone Installation with which the presence
of Submarines was detected]


EYES IN THE SEA

There were other craft that _Herr Kommandant_ had to look out for. His
were not the only submarines in the sea. His foes also were possessed
of submarines. They could not see under water any better than he could,
but they could fight on the surface as well as he, and they could
creep up on him even as he crept up on his prey. As a French submarine
commander puts it: "The U-boats used to enjoy the advantage of
remaining themselves invisible while all the surface and aërial craft
which were sent in pursuit of them were boldly outlined against the sky
and visible to them. This is one of the reasons we used submarines to
ambush U-boats." Submarines were also used to accompany the convoys,
so that the U-boat commander had to watch not only for the eyes of the
ship's lookouts and the eyes in the kite balloons, but also for the
periscope eyes that swam in the sea.


TRAILING U-BOATS BY SOUND

The troubles of the submarine-commander were multiplying. All over
the world inventors were plotting his destruction. As long as we
depended upon our eyes to ferret him out, the sea was a safe refuge,
provided he dived deep enough, but when we began to use our ears as
well, he found himself in a very serious predicament. Although light is
badly broken up in its passage through water, sound-waves will travel
through water much better than in air. The first listening-devices used
were crude affairs and did not amount to much, particularly when the
U-boats muffled their motors and engines so that they were virtually
noiseless. But the French invented a very sensitive sound-detector. It
consisted of a lot of tiny diaphragms set in a big hemisphere. There
were two of these hemispheres, one at each side of the boat. When
sound-waves struck these hemispheres, the diaphragms would respond. At
the focus of each hemisphere there was a megaphone receiver; one of
these carried the sound to the operator's right ear and the other to
his left. He would turn a megaphone around until he found the diaphragm
that produced the loudest sound. This gave him the direction of the
sound-wave. Then the boat would be steered in that direction. He knew
that it was aimed properly when the sound coming to his right ear was
just as loud as that which came into his left ear.

A still better hydrophone was developed by a group of American
inventors. The details of this cannot yet be disclosed, but we know
that it was adopted at once by our allies. A very sensitive receiver
was used which could detect a U-boat miles away and determine its
direction accurately. Under ideal conditions the range of the device
was from fifteen to twenty-five miles, but the average was from three
to eight miles. If two or more boats fitted with sound-detectors were
used, they could determine the position of the U-boat perfectly. One
drawback was that the vessel would have to stop so that the noise of
its own engines would not disturb the listener, but this was largely
overcome by trailing the detector a hundred feet or more from the stem
of the ship. The sounds were then brought in by an electric cable to
the listener in the ship.

These sound-detectors were placed on Allied submarines as well as
surface vessels and they were actually tried out on balloons and
dirigibles, so that they could follow a U-boat after it had submerged
too deeply to be followed by sight.

[Illustration: Courtesy of the "Scientific American"

FIG. 21. Chart of an actual pursuit of a U-boat which ended in the
destruction of the submarine]

[Illustration: Section of a captured Mine-laying U-boat, showing how
the mines were laid]

Many U-boats were chased to their doom by the aid of the American
hydrophone. Fig. 21 illustrates a very dramatic chase. The full line
shows the course of the U-boat as plotted out by hydrophones and the
broken line the course of the submarine-chasers. The dots represent
patterns of depth bombs dropped upon the U-boat. Try as he would, the
_Herr Kommandant_ could not shake off his pursuers. At one time, as the
listeners stopped to take observations, they heard hammering in the
U-boat as if repairs were being made. The motors of the submarine would
start and stop, showing clearly that it was disabled. More depth bombs
were dropped and then there was perfect silence, which was soon broken
by twenty-five revolver-shots. Evidently the crew, unable to come to
the surface, had given up in despair and committed suicide.

[Illustration: (C) Underwood & Underwood

A Paravane hauled up with a Shark caught in its jaws]

The Adriatic Sea was an ideal place for the use of the hydrophone. The
water there is so deep that submarines dared not rest on the bottom,
but had to keep moving, and so they could easily be followed. Across
the sea, at the heel of the boot of Italy, a barrage of boats was
established. U-boats would come down to this barrage at night and,
when within two or three miles of the boats, dive and pass under them.
But when hydrophones were used that game proved very hazardous. Our
listeners would hear them coming when they were miles away. Then they
would hear them shift from oil-to electric-drive and plunge under the
surface. Darkness was no protection to the U-boats. The sound-detector
worked just as well at night as in the daytime and a group of three
boats would drop a pattern of bombs that would send the U-boat to the
bottom.

On one occasion after an attack it was evident that the submarine had
been seriously injured. Its motors were operating, but something must
have gone wrong with its steering-gear, or its ballast-chambers may
have been flooded, because it kept going down and soon the listeners
heard a crunching noise as it was crushed by the tremendous pressure of
the water.

And so U-boat warfare grew more and more terrible for _Herr
Kommandant_. The depths of the sea were growing even more dangerous
than the surface. On every hand he was losing out. He had tried to
master the sea without mastering the surface of the sea. But he can
never really master who dares not fight out in the open. For a time,
the German did prevail, but his adversaries were quick to see his
deficiencies and, by playing upon these, to rob the terror of the sea
of his powers. And as _Herr Kommandant_ looks back at the time when he
stepped into the lime-light as the most brutal destroyer the world has
ever seen, he cannot take much satisfaction in reflecting that the sum
total of his efforts was to spread hatred of Germany throughout the
world, to summon into the conflict a great nation whose armies turned
the tide of victory against his soldiers, and finally to subject his
navy, second only to that of Great Britain, to the most humiliating
surrender the world has ever seen.



CHAPTER XIV

"DEVIL'S EGGS"


In modern warfare a duel between fixed forts and floating forts is
almost certain to end in a draw. Because the former are fixed they make
good targets, while the war-ship, being able to move about, can dodge
the shell that are fired against it. On the other hand, a fort on land
can stand a great deal of pounding and each of its guns must be put out
of action individually, before it is subdued, while the fort that is
afloat runs the risk of being sunk with a few well-directed shots.

But fortifications alone will not protect a harbor from a determined
enemy. They cannot prevent hostile ships from creeping by them under
cover of darkness or a heavy fog. To prevent this, the harbor must be
mined, and this must be done in such a way that friendly shipping can
be piloted through the mine-field, while hostile craft will be sure to
strike the mines and be destroyed.

The mines may be arranged to be fired by electricity from shore
stations, in which case they are anchored at such a depth that ships
can sail over them without touching them. If a hostile vessel tried to
dash into the harbor, the touch of a button on shore would sink it when
it passed over one of the mines. But the success of electrically fired
mines would depend upon the "seeing." In a heavy fog they would prove
no protection.

Another way of using electric mines is to have telltale devices which
a ship would strike and which would indicate to the operator on shore
that a vessel was riding over the mines and would also let him know
over which particular mines it was at the moment passing. No friendly
vessel would undertake to enter the harbor in a fog or after dark and
the operator would not hesitate to blow up the invader even if he could
not see him.

However, the ordinary method of mining a harbor is to lay fields
of anchored mines across the channels and entrances to the
harbor--sensitive mines that will blow up at the slightest touch of
a ship's hull--and leave tortuous passages through the fields for
friendly shipping. Of course pilots have to guide the ships through the
passages and lest enemy spies learn just where the openings are the
mine-fields must be shifted now and then.

The mines are, therefore, made so that they can be taken up by friendly
mine-sweepers who know just how to handle them, and planted elsewhere.
These are defensive mines, but there are other mines that are not
intended to be moved. They are planted in front of enemy harbors to
block enemy shipping and they are made so sensitive or of such design
that they will surely explode if tampered with.


THE MINE THAT DOES ITS OWN SOUNDING

A favorite type of mine used during the war was one which automatically
adjusted itself to sink to the desired depth. Submerged mines are more
dangerous to the enemy because they cannot be seen and avoided. They
should float far enough under the surface to remain hidden and yet not
so deep that a shallow-draft ship can pass over them without hitting
them. As the sea bottom may be very irregular, it is impossible to
tell how long the anchor cable should be without sounding the depth of
the water at every point at which a mine is planted. But the automatic
anchor takes care of this. Very ingeniously it does its own sounding
and holds the mine down to the depth for which it is set. The mine
cable is wound up on a reel in the anchor and the mine is held fast to
the anchor by a latch. The anchor is of box-shape or cylindrical form,
with perforations in it. At first it sinks comparatively slowly, but as
it fills with water it goes down faster. Attached to the anchor is a
plummet or weight, connected by a cord to the latch. The length of this
cord determines the depth at which the mine will float.

[Illustration: Courtesy of the "Scientific American"

FIG. 22. How the mine automatically adjusts itself to various depths of
water]

The operation of the mine is shown in Fig. 22. When it is thrown
overboard (1) it immediately turns over so that the buoyant mine _A_
floats on the surface (2). While the anchor is slowly filling and
sinking, the plummet _B_ runs out (3). If the mines are to float at a
depth of, say, ten feet, this cord must be ten feet long. As soon as it
runs out to its full length (4) it springs a latch, _C_, releasing the
mine _A_. Then the mine cable _D_ pays out, as the anchor _E_ sinks,
until the plummet _B_ strikes bottom (5). As soon as the plummet cord
slackens a spring-pressed pawl is released and locks the mine-cable
reel, so that as the anchor continues to sink it draws the mine down
with it, until it touches bottom (6), and as the anchor was ten feet
from the bottom when the plummet touched bottom and locked the reel,
the mine must necessarily be dragged down to a depth of ten feet below
the surface.

The mine itself, or the "devil's egg" as it is called, is usually a
big buoyant sphere of metal filled with TNT or some other powerful
explosive; and projecting from it are a number of very fragile prongs
which if broken or even cracked will set off the mine. There is a
safety-lever or pin that makes the mine harmless when it is being
handled, and this must be withdrawn just before the mine is to be
launched. In some mines the prongs are little plungers that are
withdrawn into the mine-shell and held by a cement which softens after
the mine is submerged and lets the plungers spring out. When the
plungers are broken, water enters and, coming in contact with certain
chemicals, produces enough heat to set off a cartridge which fires the
mine.


PICKING INFERNAL MACHINES OUT OF THE SEA

The enemy mine-fields were often located by seaplanes and then
mine-sweepers had to undertake the extremely hazardous task of raising
the mines or destroying them. If they were of the offensive type, it
was much better to destroy them. But occasionally, when conditions
permitted, mine-sweepers undertook to raise the mines and reclaim them
for future use against the enemy. The work of seizing a mine and making
it fast to the hoisting-cable of the mine-sweeper was usually done from
a small rowboat. Raising the first mine was always the most perilous
undertaking, because no one knew just what type of mine it was and how
to handle it with safety, or whether there was any way in which it
_could_ be made harmless. There were some mines, for instance, that
contained within them a small vial partly filled with sulphuric acid.
The mine carried no prongs, but if it were tilted more than twenty
degrees the acid would spill out and blow up the mine. Such a mine
would be exceedingly difficult if not impossible to handle from a boat
that was rocked about by the waves.

After the first mine of the field was raised and its safety-mechanism
studied, the task of raising the rest was not so dangerous. A water
telescope was used to locate the mine and to aid in hooking the
hoisting-cable into the shackle on the mine. The hook was screwed
to the end of a pole and after the mine was hooked, the pole was
unscrewed and the cable hauled in, bringing up the "devil's egg"
bristling with death. Care had to be taken to keep the bobbing boat
from touching the delicate prongs until the safety-device could be set.

However, this painstaking and careful method of raising mines was
not often employed. Shallow-draft mine-sweepers would run over the
mine-field, dragging a cable between them. The cable would be kept down
by means of hydrovanes or "water kites" deep enough to foul the anchor
cables of the mines. The "water kites" were V-shaped structures that
were connected to the cable in such a way that they would nose down
as they were dragged through the water and carry the cable under. The
action is just the reverse of a kite, which is set to nose up into the
wind and carry the kite up when it is dragged through the air. By means
of the cable the anchor chain of the mine was caught and then the mine
with its anchor was dragged up. If the mine broke loose from its anchor
it could be exploded with a rifle-shot if it did not automatically
explode on fouling the cable.


FLOATING MINES

When England entered the war she mined her harbors because, although
she had the mastery of the sea, she had to guard against raids of enemy
ships carried out in foggy and dark weather. But the mines were no
protection against submarines. They would creep along the bottom under
the mines. Then cable nets were stretched across the harbor channels
to bar the submarines, but the U-boats were fitted with cutters which
would tear through the nets, and it became necessary to use mines set
at lower depths so that the submarines could not pass under them; and
nets were furnished with bombs which would explode when fouled by
submarines. In fact, mines were set adrift with nets stretched between
them, to trap submarines. Floating mines were also used by the Germans
for the destruction of surface vessels and these were usually set
adrift in pairs, with a long cable connecting them, so that if a vessel
ran into the cable the mines would be dragged in against its hull and
blow it up.

The laws of war require that floating mines be of such a design that
they will become inoperative in a few hours; otherwise they might
drift about for weeks or months or years and be a constant menace to
shipping. Sometimes anchored mines break away from their moorings and
are carried around by ocean currents or are blown about by the winds.
A year after the Russo-Japanese War a ship was blown up by striking a
mine that had been torn from its anchorage and had drifted far from the
field in which it was planted. No doubt there are hundreds of mines
afloat in the Atlantic Ocean which for many years to come will hold out
the threat of sudden destruction to ocean vessels; for the Germans knew
no laws of war and had no scruples against setting adrift mines that
would remain alive until they were eaten up with rust.

[Illustration: Courtesy of the "Scientific American"

FIG. 23. Ocean currents of the North Atlantic showing the probable path
of drifting mines]

The chart on the next page shows the course of ocean currents in the
North Atlantic as plotted out by the Prince of Monaco, from which it
may be seen that German mines will probably make a complete circuit of
the North Atlantic, drifting down the western coast of Europe, across
the Atlantic, around the Azores, and into the Gulf Stream, which will
carry them back to the North Sea, only to start all over. (See Fig.
23.) Some of them will run up into the Arctic Ocean, where they will be
blown up by striking icebergs and many will be trapped in the mass of
floating seaweed in the Sargasso Sea. But many years will pass before
all danger of mines will be removed. In the meantime, the war has left
a tremendous amount of work to be done in raising anchored mines and
destroying them.


EGG-LAYING SUBMARINES

Early in the war the British were astonished to find enemy mine-fields
in their own waters, far from any German ports. They could not have
been planted by surface mine-layers, unless these had managed to
creep up disguised as peaceful trawlers. This seemed hardly likely,
because these fields appeared in places that were well guarded. Then
it was discovered that German U-boats were doing this work. Special
mine-laying U-boats had been built and one of them was captured with
its cargo of "devil's eggs."

A sectional view of the mine-laying U-boat is shown opposite page 272.
In the after part of the boat were mine-chutes in each of which three
mines were stored. A mine-laying submarine would carry about a score of
mines. These could be released one at a time. The mine with its anchor
would drop to the bottom. As soon as it struck, anchor-arms would be
tripped and spread out to catch in the sand or mud, while the mine
cable would be released and the mine would rise as far as the cable
would allow it. The U-boat commander would have to know the depth
of water in which the mines were to be laid and adjust the cables to
this depth in advance. This could not be done while the U-boat was
submerged. With the mines all set for the depth at a certain spot,
the U-boat commander had to find that very spot to lay his "eggs,"
otherwise they would either lie too deep to do any harm to shipping, or
else they would reach up to the surface, where they might be discovered
by the Allied patrols. As he had to do his navigating blindly, by
dead-reckoning, it was very difficult for him to locate his mine-fields
properly.

But the Germans did not have a monopoly on submarine mine-laying.
The British also laid mines by submarine within German harbors and
channels, right under the guns of Heligoland, and many a U-boat was
destroyed by such mines within its home waters.

[Illustration: (C) Press Illustrating Service

A Dutch Mine-sweeper engaged in clearing the North Sea of German Mines]


PARAVANES

On the other hand, the Allies had a way of sailing right through
fields of enemy mines with little danger. Our ships were equipped
with "paravanes" which are something like the "water kites" used by
mine-sweepers, and they are still used in the waters of the war
zone. Paravanes are steel floats with torpedo-shaped bodies and a
horizontal plane near the forward end. At the tail of the paravane,
there are horizontal and vertical rudders which can be set to make
the device run out from the side of the vessel that is towing it, and
at the desired depth below the surface. Two paravanes are used, one
at each side of the ship, and the towing-cables lead from the bow
of the vessel. Thus there are two taut cables that run out from the
ship in the form of a V and at such a depth that they will foul the
mooring-cable of any mine that might be encountered. The mine cable
slides along the paravane cable and in this way is carried clear
of the ship's hull. When it reaches the paravane it is caught in a
sharp-toothed jaw which cuts the mine cable and lets the mine bob up to
the surface. The mine is then exploded by rifle or machine-gun fire.

[Illustration: Courtesy of "Scientific American"

Hooking Up Enemy Anchored Mines]

In some forms of paravane there is a hinged jaw which is operated from
the ship to shear the cable. The jaw is repeatedly opened and closed by
a line that runs to a winch on the ship. This winch winds up the line
until it is taut and then the line is permitted to slip, letting the
jaw open, only to close again as the winch keeps on turning and winding
up the line.

Guarded by steel sharks on each side, their jaws constantly working,
a ship can plow right through a field of anchored mines with little
danger. To be sure, the bow might chance to hit a mine, when, of
course, there would be an explosion; but the ship could stand damage
here better than anywhere else and unless the bow actually hit the
mine, one or other of the paravanes would take care of it and keep it
from being dragged in against the hull of the vessel.


PENNING IN THE U-BOATS

According to German testimony, mines were responsible for the failure
of the U-boat. However, it was not merely the scattered mine-fields
sown in German waters that brought the U-boat to terms, but an enormous
mine-field stretching across the North Sea from the Orkney Islands
to the coast of Norway. Early in the war, U-boats had been prevented
from entering the English Channel by nets and mines stretched across
the Straits of Dover. As the submarine menace grew, it was urged that
a similar net be stretched across the North Sea to pen the U-boats
in. But it seemed like a stupendous task. The distance across at the
narrowest point is nearly two hundred and fifty miles. It would not
have been necessary to have the net come to the surface. It could just
as well have been anchored so that its upper edge would be covered with
thirty feet of water. Surface vessels could then have sailed over it
without trouble and submarines could not have passed over it without
showing themselves to patrolling destroyers. It would not have been
necessary to carry the net to the bottom of the sea. A belt of netting
a hundred and fifty feet wide would have made an effective bar to the
passage of U-boats. As U-boats might cut their way through the net, it
was proposed to mount bombs or mines on them which would explode on
contact and destroy any submarine that tried to pass. However, laying a
net two hundred feet long even when it is laid in sections, is no small
job, but when the net is loaded with contact mines, the difficulty of
the work may be well imagined.

And yet had it been thought that the net would be a success it would
have been laid anyhow, but it was argued that seaweed would clog the
meshes of the net and ocean currents would tear gaps in it. Even if it
had not been torn away, the tidal currents would have swept it down and
borne it under so far that U-boats could have passed over it in safety
without coming to the surface.


A WALL OF MINES

When America entered the war, we were very insistent that something
must be done to block the North Sea, and we proposed that a barrage of
anchored mines be stretched across the sea and that these mines be set
at different levels so as to make a "wall" that submarines could not
dive under. This would do away with all the drawbacks of a net. Ocean
currents and masses of seaweed could not affect individual mines as
they would a net. Furthermore, an American inventor had devised a new
type of mine which was peculiarly adapted to the proposed mine barrage.
It had a firing-mechanism that was very sensitive and the mine had
twice the reach of any other.

At length the British mine-laying forces were prevailed upon to join
with us in laying this enormous mine. It was one of the biggest and
most successful undertakings of the war. It was to be two hundred
and thirty miles long and twelve miles wide on the average, reaching
from the rocky shores of the Orkney Islands to Norway. There was
plenty of deep water close to the coast of Norway and it was against
international law to lay mines within three miles of the shores of a
neutral nation, so that the U-boats might have had a clear passage
around the end of the barrage. But as it was also against the law for
the U-boats to sail through neutral waters, Norway laid a mine-field
off its coast to enforce neutrality, and this was to join with that
which the British and we were to lay. Most of the mine-laying was to be
done by the United States and we were to furnish the mines.

The order to proceed with the work was given in October, 1917, and
it was a big order. A hundred thousand mines were to be made and to
preserve secrecy, as well as to hurry the work as much as possible,
it was divided among five hundred contractors and subcontractors. The
parts were put together in one plant and then sent to another, where
each mine was filled with three hundred pounds of molten TNT. To carry
them across the ocean small steamers were used, so that if one should
be blown up by a submarine the loss of mines would not be very great.
There were twenty-four of these steamers, each carrying from twelve
hundred to eighteen hundred mines and only one of them was destroyed
by a submarine. The steamers delivered their loads on the west coast
of Scotland and the mines were taken across to the east coast by rail
and motor canal-boats. Here the mines were finally assembled, ready for
planting. Seventy thousand mines were planted, four fifths of them by
American mine-layers and the rest by the British.


MINE RAILROADS ON SHIPS

To handle the mines the ships were specially fitted with miniature
railroads for transporting the mines to the launching-point, so that
they could be dropped at regular intervals without interruption. Each
anchor mine was provided with flanged wheels that ran on rails. The
mines were carried on three decks and each deck was covered with a
network of rails, switches, and turn-tables, while elevators were
provided to carry the mines from one deck to another. The mines, like
miniature railroad cars, were coupled up in trains of thirty or forty
and as each mine weighed fourteen hundred pounds, steam winches had to
be used to haul them. At the launching-point the tracks ran out over
the stern of the boat and here a trap was provided which would hold
only one mine at a time. By the pulling of a lever the jaws of the trap
would open and the mine would slide off the rails and plunge into the
sea.

The mines were dropped every three hundred feet in lines five hundred
feet apart, as it was unsafe for the mine-layers to steam any closer to
one another than that. The mines were of the type shown in Fig. 22 and
automatically adjusted themselves to various depths. The depth of the
water ran down to twelve hundred feet near the Norwegian coast. Never
before had mines been planted at anywhere near that depth.

It was dangerous work, because the enemy knew where the mines were
being planted, as neutral shipping had to be warned months in advance.
The mine-layers were in constant danger of submarine attack, although
they were convoyed by destroyers to take care of the U-boats. There was
even danger of a surface attack and so battle-cruisers were assigned
the job of guarding the mine-layers. The mine-layers steamed in line
abreast, and had one of them been blown up, the shock would probably
have been enough to blow up the others as well. Enemy mines were sown
in the path of the mine-layers, so the latter had to be preceded by
mine-sweepers. Navigation buoys had to be planted at the ends of the
lines of mines and the enemy had a habit of planting mines near the
buoys or of moving the buoys whenever he had a chance. But despite all
risks the work was carried through.

The barrier was not an impassable one. With the mines three hundred
feet apart, a submarine might get through, even though the field was
twenty-five miles broad, but the hazards were serious. Before the
first lines of mines had been extended half-way across, its value
was demonstrated by the destruction of several U-boats, and as the
safety-lane was narrowed down the losses increased. It is said that
altogether twenty-three German submarines met their doom in the great
mine barrage. U-boat commanders balked at running through it, and
U-boat warfare virtually came to a standstill. According to Captain
Bartenbach, commander of submarine bases in Flanders, three U-boats
were sunk by anchored mines for every one that was destroyed by a depth
bomb.



CHAPTER XV

SURFACE BOATS


The war on the submarine was fought mainly from the surface of the
sea and from the air above the sea, and naturally it resulted in many
interesting naval developments.

As described in Chapter XIII, the first offensive measure against the
U-boat was the building of swarms of speedy motor-boats which drove the
invaders away from harbors and into the open sea. To follow the U-boats
out into rough water larger submarine-chasers were built, but even they
could not cope with the enemy far from the harbors.


MOTOR TORPEDO-BOATS

The Italians made excellent use of speedy motor-boats in the protected
waters of the Adriatic Sea. One type of motor-boat was equipped with
two torpedo-tubes in the bow. Small 14-inch torpedoes were used, but
as each torpedo carried two hundred pounds of high explosive, the
motor-boat was a formidable vessel if it crept in close enough to
discharge one of these missiles at its foe.

On one occasion, a patrol of these little boats sighted a couple of
Austrian dreadnoughts headed down the coast, surrounded by a screen
of ten destroyers. Favored by the mist, two of the motor-boats crept
through the screen of destroyers, and torpedoed the battle-ships. Then
they made good their escape. A destroyer that pursued one of the boats
decided that the game was not worth while when it was suddenly shaken
up by the explosion of a depth bomb dropped from the motor-boat.


THE SEA TANK

The Italians showed a great deal of naval initiative. They were forever
trying to trap the Austrian fleet or to invade its harbors. Like all
other naval powers, the Austrians protected their harbors with nets and
mines. It was impossible for submarines to make an entrance and the
ports were too well fortified to permit an open attack on the surface.
Nevertheless, the Italians did break through the harbor defenses on one
or two occasions and sank Austrian war-vessels. Again it was with a
small boat that they did the trick.

The nets which the Austrians stretched across their harbor entrance
were supported on wooden booms or logs which served as floats. These
booms offered an effective bar to small boats which might attempt to
enter the harbor under cover of darkness. But the Italians found a way
to overcome this obstruction. They built a flat-bottomed motor-boat
which drew very little water. Running under the boat were two endless
chains, like the treads of a tank. In fact, the boat came to be known
as a "sea tank." The chains were motor-driven and had spiked sprockets,
so that when a boom was encountered they would bite into the wood and
pull the boat up over the log, or maybe they would drag the log down
under the boat. At any rate, with this arrangement it was not very
difficult to pass the boom and enter the harbor. At the rear the chains
were carried back far enough to prevent the propeller from striking
when the boat had passed over the log.

[Illustration: Courtesy of "Scientific American"

An Italian "Sea-tank" climbing over a Harbor Boom]

[Illustration: (C) Underwood & Underwood

Deck of a British Aircraft Mothership or "Hush ship"]


THE AWKWARD "EAGLES"

A curious boat that we undertook to furnish during the war was a cross
between a destroyer and a submarine-chaser. After the submarine had
been driven out to sea its greatest foe was undoubtedly the destroyer,
and frantic efforts were made to turn out as many destroyers as
possible. But it takes time to build destroyers and so a new type of
boat was designed, to be turned out quickly in large numbers. A hundred
and ten "Eagles" (as these boats are called) were ordered, but the
armistice was signed before any of them were put into service; and
it is just as well that such was the case, for in their construction
everything was sacrificed to speed of production. As a consequence they
are very ugly boats, with none of the fine lines of a destroyer, and
they roll badly, even when the sea is comparatively peaceful. They are
five-hundred-ton boats designed to make eighteen knots, which would not
have been fast enough to cope with U-boats, because the latter could
make as high a speed as that themselves, when traveling on the surface,
and the two 4-inch guns of the Eagles would have been far outranged by
the 5.9-inch guns of the larger U-boats.


SEAPLANE TOWING-BARGES

When the war on the U-boat was carried up into the sky, many new naval
problems cropped up, particularly when German submarines chose to work
far out at sea. Big seaplanes were used, but they consumed a great deal
of fuel in flying out and back, cutting down by just so much their
flying-radius at the scene of activities. A special towing-barge was
used. These barges had trimming-tanks aft, which could be flooded so
that the stern of the barge would submerge. A cradle was mounted to run
on a pair of rails on the barge. The body of the seaplane was lashed
to this cradle and then drawn up on the barge by means of a windlass.
This done, the water was blown out of the trimming-tanks by means of
compressed air and the barge was brought up to an even keel. The barge
with its load was now ready to be towed by a destroyer or other fast
boat to the scene of operations. There water was again let into the
trimming-tanks and the seaplane was let back into the water. From the
water the seaplane arose into the air in the usual way.

Unfortunately, when the sea is at all rough it is exceedingly difficult
for a seaplane to take wing, particularly a large seaplane. A better
starting-platform than the sea had to be furnished. At first some
seaplanes were furnished with wheels, so that they could be launched
from platforms on large ships; and then, to increase the flying-radius,
seaplanes were discarded in favor of airplanes. Once these machines
were launched, there was no way for them to get back to the ship. They
had to get back to land before their fuel was exhausted.

On the large war-vessels a starting-platform was built on a pair of
long guns. Then the war-ship would head into the wind and the combined
travel of the ship and of the airplane along the platform gave speed
enough to raise the plane off the platform before it had run the full
length of the guns. But as long as aviators had no haven until they
got back to land, there were many casualties. Eager to continue their
patrol as long as possible, they would sometimes linger too long
before heading for home and then they would not have enough fuel
left to reach land. Many an aviator was lost in this way, and finally
mother-ships for airplanes had to be built.

[Illustration: Courtesy of "Scientific American"

Electrically Propelled Boat or Surface Torpedo, Attacking a Warship,
under Guidance of an Airplane Scout]


THE "HUSH SHIPS"

The British Navy had constructed a number of very fast cruisers to deal
with any raiders the Germans might send out. These cruisers were light
vessels capable of such high speeds that they could even overtake a
destroyer. They were 840 feet long and their turbines developed 90,000
horse-power. The construction of these vessels was for a long time kept
a profound secret and it was not until the German fleet surrendered
that photographs of them were allowed to be published. Because of
this secrecy the boats were popularly known as "hush ships." They
were not armored; it was not necessary to load them down with armor
plate, because their protection lay in speed and they were designed
to fight at very long range. In fact, they were to carry guns that
would outrange those of the most powerful dreadnoughts. Our largest
naval guns are of 16-inch caliber, but the "hush ships" were each to
carry two _18-inch guns_. The guns were monsters weighing 150 tons
each and they fired a shell 18 inches in diameter and 7 feet long to
a distance of 30 miles when elevated to an angle of 45 degrees. The
weight of the shell was 3600 pounds and it carried 500 pounds of high
explosive or more than is carried in the largest torpedoes.

At the 32-mile range the shell would pass through 12 inches of
face-hardened armor and at half that range it would pass through armor
18 inches thick, and there is no armor afloat any heavier than this.

[Illustration: Courtesy of "Scientific American"

Hauling a Seaplane up on a Barge so that it may be Towed at High Speed
by a Destroyer]


MOTHER-BOATS FOR AIRPLANES

Armed with such powerful guns as these, the "hush ships" would have
been very formidable indeed; but when the guns were mounted on one
of the cruisers, the _Furious_, they were found too powerful for the
vessel. It was evident that the monsters would very seriously rack
their own ship. So the guns were taken off the cruiser and it was
turned into a mother-ship for airplanes. A broad, unobstructed deck
was built on the ship which provided a runway from which airplanes
could be launched, and this runway was actually broad enough to permit
airplanes to land upon it. Under the runway were the hangars in which
the airplanes were housed. Other "hush ships" were also converted into
airplane mother-boats and there were special boats built for this very
purpose, although they were not able to make the speed of the "hush
ships." One of these special boats had funnels that turned horizontally
to carry off the furnace smoke over the stern and leave a perfectly
clear flying-deck, 330 feet long.


TORPEDO-PROOF MONSTERS

As for the 18-inch guns, they were put to another use. Early in the war
the British had need for powerful shallow-draft vessels which could
operate off the Flanders coast and attack the coast fortifications that
were being built by the Germans. The ships that were built to meet this
demand were known as monitors, because like the famous "monitor" of our
Civil War they carried a single turret. These monitors were very broad
for their length and were very slow. At best they could make only seven
knots and in heavy weather they could not make more than two or three
knots.

To be made proof against torpedoes these boats were formed with
"blisters" or hollow rounded swells in the hull at each side which
extended out to a distance of twelve to fifteen feet. The blisters were
subdivided into compartments, so that if a torpedo struck the ship it
would explode against a blister at a considerable distance from the
real hull of the ship and the force of the explosion would be expended
in the compartments. The blisters were the salvation of the monitors.
Often were the boats struck by torpedoes without being sunk.

Unfortunately, this form of protection could not be applied to ordinary
vessels, because it would have interfered seriously with navigation.
The blisters made the monitors very difficult to steer and hampered the
progress of a ship, particularly in a seaway.

With ships such as these the British bombarded Zeebrugge from a
distance of twenty to twenty-five miles. Of course, the range had to be
plotted out mathematically, as the target was far beyond the horizon of
the ship, and the firing had to be directed by spotters in airplanes.

At first guns from antiquated battle-ships were used in the monitors;
then larger guns were used, until finally two of the monitors
inherited the 18-inch guns of the _Furious_. A single gun was mounted
on the after deck of each vessel and the gun was arranged to fire only
on the starboard side. No heavily armored turret was provided, but
merely a light housing to shelter the gun.


AN ELECTRICALLY STEERED MOTOR-BOAT

The British war-vessels that operated in the shallow waters off the
coast of Flanders were a constant source of annoyance to the Germans.
Because of the shallow water it was seldom possible for a submarine
to creep up on them. A U-boat required at least thirty-five feet of
water for complete submergence and it did not dare to attack in the
open. This led the Germans to launch a motor-boat loaded with high
explosive, which was steered from shore. The motor-boat carried a reel
of wire which connected it with an operator on shore. There was no
pilot in the boat, but the helm was controlled electrically by the man
at the shore station. As it was difficult for the helmsman to see just
what his boat was doing, or just how to steer it when it was several
miles off, an airplane flew high above it and directed the helmsman,
by radiotelegraphy, how to steer his boat. Of course, radiotelegraphy
might have been used to operate the steering-mechanism of the boat, but
there was the danger that the radio operators of the British might send
out disturbing waves that would upset the control of the motor-boat,
and so direct wire transmission was used instead. Fortunately, when the
Germans tried this form of attack, an alert British lookout discovered
the tiny motor-boat. The alarm was given and a lucky shot blew up the
boat with its charge before it came near the British vessel.



CHAPTER XVI

RECLAIMING THE VICTIMS OF THE SUBMARINE


Nearly fifteen million tons of shipping lie at the bottom of the sea,
sunk by German U-boats, and the value of these ships with their cargo
is estimated at over seven billion dollars. In one year, 1917, the loss
was nearly a million dollars a day.

Of course these wrecks would not be worth anything like that now, if
they were raised and floated. Much of the cargo would be so damaged by
its long immersion in salt water that it would be absolutely valueless,
but there are many kinds of merchandise that are not injured in the
least by water. Every ship carries a certain amount of gold and silver;
and then the ship's hull itself is well worth salving, provided it was
not too badly damaged by the torpedo that sank it. Altogether, there
is plenty of rich treasure in the sea awaiting the salvor who is bold
enough to go after it.

To be sure, not all of the U-boat's victims were sunk in deep water.
Many torpedoed vessels were beached or succeeded in reaching shallow
water before they foundered. Some were sunk in harbors while they lay
at anchor, before the precaution was taken of protecting the harbors
with nets. The Allies did not wait for the war to end before trying to
refloat these vessels. In fact, during the war several hundred ships
were raised and put back into service. A special form of patch was
invented to close holes torn by torpedoes. Electric pumps were built
which would work under water and these were lowered into the holds
of ships to pump them out. The salvors were provided with special
gas-masks to protect them from poisonous fumes of decayed matter in the
wrecks.

Our own navy has played an important part in salvage. Shortly after
we entered the war, all the wrecking-equipment in this country was
commandeered by the government and we sent over to the other side
experienced American salvors, provided with complete equipment of
apparatus and machinery.

The majority of wrecks, however, are found in the open sea, where it
would have been foolish to attempt any salvage-operations because of
the menace of submarine attack. On at least one occasion a salvage
vessel, while attempting to raise the victims of a submarine, fell,
itself, a prey to a Hun torpedo. Now that this menace has been removed,
such vessels as lie in comparatively shallow water, and in positions
not subject to sudden tempests, can be raised by the ordinary methods;
or if it is impracticable to raise them, much of their cargo can be
reclaimed. However, most of the torpedoed ships lie at such depths that
their salvage would ordinarily be despaired of.


IN THE DEPTHS OF THE SEA

It will be interesting to look into conditions that exist in deep
water. Somehow the notion has gone forth that a ship will not surely
sink to the very bottom of the deep sea, but on reaching a certain
level will find the water so dense that even solid iron will float,
as if in a sea of mercury, and that here the ship will be maintained
in suspension, to be carried hither and yon by every chance current.
Indeed, it makes a rather fantastic picture to think of these lost
ships drifting in endless procession, far down beneath the cold green
waves, and destined to roam forever like doomed spirits in a circle of
Dante's Inferno.

But the laws of physics shatter any such illusion and bid us paint
a very different picture. Liquids are almost incompressible. The
difference in density between the water at the surface of the sea and
that at a depth of a mile is almost insignificant. As a matter of fact,
at that depth the water would support only about half a pound more
per cubic foot than at the surface. The pressure, however, would be
enormous. Take the _Titanic_, for instance, which lies on the bed of
the ocean in water two miles deep. It must endure a pressure of about
two long tons on every square inch of its surface. Long before the
vessel reached the bottom her hull must have been crushed in. Every
stick of wood, every compressible part of her structure and of her
cargo, must have been staved in or flattened. As a ship sinks it is not
the water but the ship that grows progressively denser. The _Titanic_
must have actually gained in weight as she went down, and so she must
have gathered speed as she sank.

We may be certain, therefore, that every victim of Germany's ruthless
U-boats that sank in deep water lies prone upon the floor of the sea.
It matters not how or where it was sunk, whether it was staggered by
the unexpected blow of the torpedo and then plunged headlong into
the depths of the sea, or whether it lingered, mortally wounded, on
the surface, quietly settling down until the waves closed over it.
Theoretically, of course, a perfect balance might be reached which
would keep a submerged vessel in suspension, but practically such a
condition is next to impossible. Once a ship has started down, she will
keep on until she reaches the very bottom, whether it be ten fathoms or
ten hundred.


A SUBMARINE GRAVEYARD

Instead of the line of wandering specters, then, we must conjure up a
different picture, equally weird--an under-world shrouded in darkness;
for little light penetrates the deep sea. Here in the cold blackness,
on the bed of the ocean, the wrecks of vessels that once sailed proudly
overhead lie still and deathly silent--some keeled over on their sides,
some turned turtle, and most of them probably on even keel. Here and
there may be one with its nose buried deep in the mud; and in the
shallower waters we may come across one pinned down by the stern, but
with its head buoyed by a pocket of air, straining upward and swaying
slightly with every gentle movement of the sea, as if still alive.

This submarine graveyard offers wonderful opportunities for the
engineer, because the raising of wrecked vessels is really a branch
of engineering. It is a very special branch, to be sure, and one that
has not begun to receive the highly concentrated study that have such
other branches as tunneling, bridge-construction, etc. Nevertheless it
is engineering, and it has been said of the engineer that his abilities
are limited only by the funds at his disposal. Now he has a chance to
show what he can do, for there are hundreds of vessels to be salved
where before there was but one. The vast number of wrecks in deep water
will make it pay to do the work on a larger and grander scale than has
been possible heretofore. Special apparatus that could not be built
economically for a single wreck may be constructed with profit if a
number of vessels demanding similar treatment are to be salved.

The principal fields of German activities were the Mediterranean Sea
and the waters surrounding the British Isles. Although the submarine
zone covered some very deep water, where the sounding-lead runs down
two miles without touching bottom, obviously more havoc could be
wrought near ports where vessels were obliged to follow a prescribed
course, and so most of the U-boat victims were stricken when almost in
sight of land. In fact, as was pointed out in a previous chapter, it
was not until efficient patrol measures made it uncomfortable for the
submarines that they pushed out into the open ocean to pursue their
nefarious work. The _Lusitania_ went down only eight miles from Old
Head of Kinsale, in fifty fathoms of water.

If we draw a line from Fastnet Rock to the Scilly Islands and from
there to the westernmost extremity of France, we enclose an area in
which the German submarines were particularly active. The soundings
here run up to about sixty fathoms in some places, but the prevailing
depth is less than fifty fathoms. In the North Sea, too, except for a
comparatively narrow lane along the Norwegian coast--which, by the way,
marked the safety lane of the German blockade zone--the chart shows
fifty fathoms or under. If our salvors could reach down as far as that,
most of the submarine victims could be reclaimed. But fifty fathoms
means 300 feet, which is a formidable depth for salvage work. Only one
vessel has ever been brought up from such a depth and that was a small
craft, one of our submarines, the _F-4_, which sank off the coast of
Hawaii four years ago.


DIFFERENT WAYS OF SALVING A WRECK

There are four well-known methods of raising a vessel that is
completely submerged. Of course, if the ship is not completely
submerged, the holes in her hull may be patched up, and then when her
hull is pumped out, the sea itself will raise the ship, unless it be
deeply embedded in sand or mud. If the vessel is completely submerged,
the same process may be resorted to, but first the sides of the hull
must be extended to the surface to keep the water from flowing in as
fast as it is pumped out. It is not usual to build up the entire
length of the ship. If the deck is in good condition, it may suffice
to construct coffer-dams or walls around several of the hatches. But
building up the sides of a ship, or constructing coffer-dams on the
ship's deck is a difficult task, at best, because it must be done under
water by divers.

A record for this type of salvage work was established by the Japanese
when they raised the battle-ship _Mikasa_ that lay in some eighty feet
of water. Her decks were submerged to a depth of forty feet. It is
doubtful that this salvage work could be duplicated by any other people
of the world. The wonderful patriotism and loyalty of the Japanese race
were called forth. It is no small task to build a large coffer-dam
strong enough to withstand the weight of forty feet of water, or a
pressure of a ton and a quarter per square foot, even when the work is
done on the surface. Perfect discipline and organized effort of the
highest sort were required. Labor is cheap in Japan and there was no
dearth of men for the work. Over one hundred divers were employed. In
addition to the coffer-dam construction much repair work was necessary.
Marvelous acts of devotion and heroism were performed. It is rumored
that in some places it was necessary for divers to close themselves in,
cut their air supply-pipes and seal themselves off from the slightest
chance of escape; and that there were men who actually volunteered to
sacrifice their lives in this way for their beloved country and its
young navy. Where, indeed, outside of the Land of the Rising Sun could
we find such patriotic devotion!

A second salvage method consists in building a coffer-dam not on the
ship but around it, and then pumping this out so as to expose the ship
as in a dry-dock. Such was the plan followed out in recovering the
_Maine_. Obviously, it is a very expensive method and is used only in
exceptional cases, such as this, in which it was necessary to make a
post-mortem examination to determine what caused the destruction of the
vessel. Neither of these methods of salvage will serve for raising a
ship sunk in deep water.


RAISING A SHIP ON AIR

A salvage system that has come into prominence within recent years
consists in pumping air into the vessel to drive the water out, thus
making the boat light enough to float. This scheme can be used only
when the deck and bulkheads of the boat are strongly built and able
to stand the strain of lifting the wreck, and when the hole that sank
the vessel is in or near the bottom, so as to allow enough airspace
above it to lift the boat. The work of the diver in this case consists
of closing hatches and bulkhead doors, repairing holes in the upper
part of the hull, and generally strengthening the deck. It must be
remembered that a deck is built to take the strain of heavy weights
bearing down upon it. It is not built to be pushed up from beneath,
so that frequently this method of salving is rendered impracticable
because the deck itself cannot stand the strain.

[Illustration: Climbing into an Armored Diving Suit]

[Illustration: Lowering an Armored Diver into the Water]

A more common salvage method consists in passing cables or chains under
the wreck and attaching them to large floats or pontoons. The slack in
the chains is taken up when the tide is low, so that on the turn of
the tide the wreck will be lifted off the bottom. The partially raised
wreck is then towed into shallower water, until it grounds. At the
next low tide, the slack of the chains is again taken in, and at
flood-tide the wreck is towed nearer land. The work proceeds step by
step, until the vessel is moved inshore far enough to bring its decks
awash; when it may be patched up and pumped out. Where the rise of the
tide is not sufficient to be of much assistance, hydraulic jacks or
other lifting-apparatus are used.

[Illustration: A Diver's Sea Sled ready to be towed along the bed of
the sea]

[Illustration: The Sea Sled on Land showing the forward horizontal and
after vertical rudders]


SALVING THE U. S. SUBMARINE F-4

If the salvor could always be assured of clear weather, his troubles
would be reduced a hundredfold, but at best it takes a long time to
perform any work dependent upon divers, and the chances are very good
when they are operating in an unsheltered spot, that a storm may come
up at any time and undo the result of weeks and months of labor. This
is what happened when the submarine _F-4_ was salved. After a month
of trying effort the submarine was caught in slings hung from barges,
lifted two hundred and twenty-five feet, and dragged within a short
distance of the channel entrance of the harbor, where the water was
but fifty feet deep. But just then a violent storm arose, which made
the barges surge back and forth and plunge so violently that the
forward sling cut into the plating of the submarine and crushed it.
The wreck had to be lowered to the bottom and the barges cut free to
save them from being smashed. At the next attempt to raise the _F-4_
pontoons were again used, but instead of being arranged to float on the
surface, they were hauled down to the wreck and made fast directly to
the hull of the submarine. Then when the water was forced out of the
pontoons with compressed air, they came up to the surface, bringing the
submarine with them. In this way all danger of damage due to sudden
storms was avoided because water under the surface is not disturbed
by storms overhead; and when the wreck was floated, the pontoons and
submarine formed a compact unit.

While this method of salvage seems like a very logical one for work
in the open sea, one is apt to forget how large the pontoons must be
to lift a vessel of any appreciable size. Not only must they support
their own dead weight, together with that of the sunken vessel, but
some allowance must usually be made for dragging the wreck out of the
clutches of a sandy or muddy bottom. Imagine the work of building
pontoons large enough to raise the _Lusitania_. They would have to have
a combined displacement greater than that of the vessel itself, and
they would have to be so large that they would be very unwieldy things
to handle in a seaway. It is for this reason that submarine pontoons
are not often used to take the entire weight of the vessel. So far
they have been employed mainly to salve small ships and then only to
take a portion of the weight, the principal work being done by large
wrecking-cranes. Instead of horizontal pontoons it has been suggested
that vertical pontoons be employed, so as to provide a greater
lifting-power without involving the use of enormous unwieldy units.

Ships are not built so that they can be picked up by the ends. Such
treatment would be liable to break their backs in the middle. Were
they built more like a bridge truss, the salvor's difficulties would
be materially lessened. It would be a much simpler matter to raise a
vessel with pontoons were it so constructed that the chains of the
pontoon could be attached to each end of the hull. But because a ship
is built to be supported by the water uniformly throughout its length,
the salvor must use a large number of chains, properly spaced along
the hull, so as to distribute the load uniformly and see that too much
weight does not fall on this or that pontoon.

The main problem, however, is to get hold of the wreck and this
requires the services of divers, so that if there were no other
limiting factor, the depth to which a diver may penetrate and perform
his duties sets the mark beyond which salvage as now conducted is
impossible.

[Illustration: (C) International Film Service

The Diving Sphere built for Deep Sea Salvage Operations]

A common diver's suit does not protect the diver from hydraulic
pressure. Only a flexible suit and a thin layer of air separates him
from the surrounding water. This air must necessarily be of the same
pressure as the surrounding water. The air that is pumped down to the
diver not only serves to supply his lungs, but by entering his blood
transmits its pressure to every part of his anatomy. As long as the
external pressure is equalized by a corresponding pressure within him,
the diver experiences no serious discomfort. In fact, when the pressure
is not excessively high he finds it rather exhilarating to work under
such conditions; for, with every breath, he takes in an abnormal amount
of oxygen. When he returns to the surface he realizes that he has
been working under forced draft. He is very much exhausted and he is
very hungry. It takes a comparatively short time to build up the high
internal pressure, which the diver must have in order to withstand
the pressure of the water outside, but it is the decompression when
he returns to the surface that is attended with great discomfort and
positive danger. If the decompression is not properly effected, the
diver will suffer agonies and even death from the so-called "Caisson
Disease."

[Illustration: The Pneumatic Breakwater--Submerged Air Tubes protecting
a California Pier from Ocean Storms]


A HUMAN SODA-WATER BOTTLE

We know now a great deal more than we used to know about the effect
of compressed air on the human system, and because of this knowledge
divers have recently descended to depths undreamed of a few years ago.
When a diver breathes compressed air, the oxygen is largely consumed
and exhaled from the lungs in the form of carbon-dioxide, but much of
the nitrogen is dissolved in the blood and does not escape. However,
like a bottle of soda-water, the blood shows no sign of the presence of
the gas as long as the pressure is maintained. But on a sudden removal
of the pressure, the blood turns into a froth of nitrogen bubbles, just
as the soda-water froths when the stopper of the bottle is removed.
This froth interrupts the circulation. The release of pressure is felt
first in the arteries and large veins. It takes some time to reach all
the tiny veins, and serious differences of pressure are apt to occur
that often result in the rupture of blood-vessels. The griping pains
that accompany the "Caisson Disease" are excruciating. The only cure is
to restore the blood to its original pressure by placing the patient
in a hospital lock, or boiler-like affair, where compressed air may be
admitted; and then to decompress the air very slowly.

It is possible to relieve the pressure in a bottle of soda-water so
gradually that the gas will pass off without the formation of visible
bubbles, and that is what is sought in decompressing a diver. After
careful research it has been found that the pressure may be cut down
very quickly to half or even less of the original amount, but then
the diver must wait for the decompression to extend to the innermost
recesses of his being and to all the tiny capillaries of his venous
system.

In the salvage of the _F-4_ a diver went down 306 feet, and remained
on the bottom half an hour. The pressure upon him was 135 pounds per
square inch, or about 145 tons on the surface of his entire body. Some
idea of what this means may be gained if we consider that the tallest
office building in the world does not bear on its foundations with a
greater weight than 215 pounds to the square inch or only about 50 per
cent more than the crushing pressure this diver had to endure.

It took the diver a very short time to go down. On coming up he
proceeded comparatively rapidly until he reached a depth of 100 feet.
There he found the bottom rung of a rope ladder. On it he was obliged
to rest for several minutes before proceeding to the next rung. The
rungs of this ladder were 10 feet apart, and on each rung the diver
had to rest a certain length of time, according to a schedule that had
been carefully worked out. At the top rung, for instance, only 10 feet
from the surface, he was obliged to wait forty minutes. In all, it
took him an hour and forty-five minutes to come up to the surface. The
decompression was complete and he suffered no symptoms of the "Caisson
Disease." But he was so exhausted from his efforts that he was unfit
for work for several days. Yet the operations that he performed at the
depth of 300 feet would not have taken more than a few minutes on the
surface.


A SUBMARINE REST-CHAMBER

The Germans have paid a great deal of attention to deep-diving
operations, and no doubt while their U-boats were sinking merchant
ships German salvors were anticipating rich harvests after hostilities
ended. One scheme they developed was a submarine rest-chamber which
could be permanently located on the bottom of the sea close to the
point where the salvage operations were to take place. This chamber
consists of a large steel box which is supplied with air from the
surface and in which divers may make themselves comfortable when they
need a rest after arduous work. Entrance to the chamber is effected
through a door in the floor. The pressure of the air inside prevents
the water from rising into the chamber and flooding it. From this
submarine base the divers may go out to the wreck, either equipped
with the ordinary air-tube helmets or with self-regenerating apparatus
which makes them independent of an air-supply for a considerable period
of time. When the diver has worked for an hour or two, or when he is
tired, he may return to this chamber, remove his helmet, eat a hearty
meal, take a nap if he needs it, and then return to the salvage work
without going through the exhausting operation of decompressing.


CUTTING METAL UNDER WATER WITH A TORCH

The work of the diver usually consists of far more than merely passing
lines under a sunken hull. It is constantly necessary for him to cut
away obstructing parts. He must sometimes use blasting-power. Pneumatic
cutting-tools frequently come into play, but the Germans have lately
devised an oxy-hydrogen torch for underwater use, with which the diver
can cut metal by burning through it. This is accomplished by using a
cup-shaped nozzle through which a blast of air is projected under such
pressure that it blows away the water over the part to be cut. The
oxygen and hydrogen jets are then ignited electrically, and the work
of cutting the metal proceeds in the hole in the water made by the
air-blast. A similar submarine torch has recently been developed by
an American salvage company. It was employed successfully in cutting
drainage-holes in the bulkheads of the _St. Paul_, which was raised in
New York Harbor in the summer of 1918.


EXPLORING THE SEA BOTTOM IN A DIVER'S SLED

The diver's sled is still another interesting German invention. It is
a sled provided with vertical and horizontal rudders, which is towed
by means of a motor-boat at the surface. The diver, seated on the
sled, and provided with a self-contained diving-suit, can direct the
motor-boat by telephone and steer his sled up and down and wherever
he chooses. And so without any physical exertion, he can explore the
bottom of the sea and hunt for wrecks.


ARMORED DIVING-SUITS

From time to time attempts have been made to construct a diver's suit
that will not yield to the pressure of the sea, so that the diver
will not be subjected to the weight of the water about him, but can
breathe air at ordinary atmospheric pressure. Curious armor of steel
has been devised, with articulated arms and legs, in which the diver is
completely encased. With the ordinary rubber suit, the diver usually
has his hands bare, because he is almost as dependent upon the sense
of touch as a blind man. But where the pressure mounts up to such a
high degree that a metal suit must be used, no part of the body may be
exposed. If a bare hand were extended out of the protecting armor it
would immediately be mashed into a pulp and forced back through the
opening in the arms of the suit. The best that can be done, then, is to
furnish the arms of the suit with hooks or tongs or other mechanical
substitutes for hands which will enable the diver to make fast to the
wreck or various parts of it.

But if a diver feels helpless in the bag of a suit now commonly worn,
what would he do when encased in a steel boiler; for that is virtually
what the armored suit is! A common mistake that inventors of armor
units have made is to fail to consider the effects of the enormous
hydraulic pressure on the joints of the suit. In order to make them
perfectly tight, packings must be employed, and these are liable to be
so jammed by the hydraulic pressure that it is well nigh impossible to
articulate the limbs. Again, the construction of the suit should be
such that when a limb is flexed it would not displace any more water
than when in an extended position, and vice versa. A diver may find
that he cannot bend his arm, because in doing so he would expand the
cubical content of his armor by a few cubic inches, and to make room
for this increment of volume it would be necessary for him to lift
several hundred pounds of water. The hydraulic pressure will reduce the
steel suit to its smallest possible dimensions, which may result either
in doubling up the members or extending them rigidly.

But these difficulties are not insuperable. There is no reason why a
steel manikin cannot be constructed with a man inside to direct its
movements.


THE SALVOR'S SUBMARINE

Other schemes have been devised to relieve the diver of abnormally
high air-pressure. One plan is to construct a large spherical
working-chamber strong enough to withstand any hydraulic pressure that
might be encountered. This working-chamber is equipped with heavy
glass ports through which the workers can observe their surroundings
in the light of an electric search-light controlled from within the
chamber. The sphere is to be lowered to the wreck from a barge, with
which it will be in telephonic communication and from which it will
be supplied with electric current to operate various electrically
driven mechanisms. By means of electromagnets this sphere may be
made fast to the steel hull of the vessel and thereupon an electric
drill is operated to bore a hole in the ship and insert the hook of
a hoisting-chain. This done, the sphere would be moved to another
position, as directed by telephone and another chain made fast. The
hoisting-chains are secured to sunken pontoons and after enough of the
chains have been attached to the wreck the pontoons are pumped out and
the wreck is raised.

It is a pity that ship-builders have not had the forethought to provide
substantial shackles at frequent intervals firmly secured to the
framing. A sunken vessel is really a very difficult object to make
fast to and the Patent Office has recorded many very fantastic schemes
for getting hold of a ship's hull without the use of divers. One man
proposes the use of a gigantic pair of ice-tongs; and there have been
no end of suggestions that lifting-magnets be employed, but no one who
has any idea of how large and how heavy such magnets must be would give
these suggestions any serious consideration.

But, after all, the chief obstacle to salvage in the open sea is the
danger of storms; months of preparation and thousands of dollars' worth
of equipment may be wiped out in a moment.


FIGHTING THE WAVES WITH AIR

However, there has been another recent development which may have a
very important bearing on this problem of deep-sea salvage work. It
has often been observed that a submerged reef, twenty or thirty feet
below the surface, may act as a breakwater to stop the storming waves.
An inventor who studied this phenomenon arrived at the theory that the
reefs set up eddies in the water which break up the rhythm of the
waves and convert them into a smother of foam just above the reef.
Thereupon he conceived the idea of performing the same work by means of
compressed air. He laid a pipe on the sea bottom, forty or fifty feet
below the surface, and pumped air through it. Just as he had expected,
the line of air bubbles produced exactly the same effect as the
submerged reef. They set up a vertical current of water which broke up
the waves as soon as they struck this barrier of air.

The "pneumatic breakwater," as it is called, has been tried out on an
exposed part of the California coast, to protect a long pier used by an
oil company. It has proved so satisfactory that the same company has
now constructed a second breakwater about another pier near by. There
is no reason why a breakwater of this sort should not be made about a
wreck to protect the workers from storms. Where the water is very deep,
it would not be necessary to lay the compressed-air pipe on the bottom,
but it could be carried by buoys at a convenient depth.

Summing up the situation, then, there are two serious bars to the
successful salvage of ships sunk in the open sea--the wild fury of the
waves on the surface; and the silent, remorseless pressure of the deep.
The former is the more to be feared; and if the waves really can be
calmed, considerably more than half the problem is solved. As for the
pressure of the sea, it can be overcome, as we have seen, either by
the use of special submarine mechanisms, or of man-operated manikins
or even of unarmored divers. We have reached a very interesting stage
in the science of salvage, with the promise of important developments.
Fifty fathoms no longer seems a hopeless depth.

Even in times of peace the sea exacts a dreadful toll of lives and
property. Before the war the annual loss by shipwreck around the
British Isles alone was estimated at forty-five million dollars. But
the war, although it was frightfully destructive to shipping, may
in the long run save more vessels than it sank; for it has given us
sound-detectors which should remove the danger of collisions in foggy
weather, and the wireless compass, which should keep ships from running
off the course and on the rocks. And now, if salvage engineering
develops as it should, the sea will be made to give up not only much
of the wealth it swallowed during the war, but also many of the rich
cargoes of gold and silver it has been hoarding since the days of the
Spanish galleon.



INDEX


  Air, fighting waves, 334
    raising ship, on, 319
    war in, 123

  Airplane, ambulance, 146
    armored, 139
    artillery-spotting, 131
    camera, 173
    cartridges, 131
    classes of work, 127
    fighting among clouds, 137
    flying boats, 144
    gasolene tank, 130
    giant, 132
    hospital, 146
    launching from ship, 303
    Liberty motor, 142
    scouting, 125
    scouts, 128
    speed of, 134
    spotting, 177
    training spotters, 180
    wireless telephone, 194
    See also Seaplane

  Ambulance airplane, 146

  Armored diving-suit, 330

  Arms and armor, 111

  Artillery, hand, 23

  Atmosphere, shooting beyond, 64

  Audion, 185


  Balloon, Blimp, 260
    helium, 164
    historical, 148
    hydrogen, 150

  Balloon, kite, 174
    principles, 150
    record flight, 65

  Barbed wire, 15
    cylinders, 17
    gate, trench, 9
    gates through, 15
    shelling, 16

  Barge for towing seaplanes, 302

  Barrage, grenade, 27
    mine, 292

  Battle-fields, miniature, 180

  Blimp, 260

  Blisters on ships, 307

  Boats, electric, 308
    Eagle, 301
    flying, 144
    surface, 298

  Bombs to destroy barbed wire, 16

  Breakwater, pneumatic, 335

  Browning, John M., 56

  Buildings, shadowless, 227


  Caisson disease, 325

  Caliber, 68

  Camera, airplane, 173

  Camouflage and camoufleurs, 211
    buildings, 227
    grass, 229
    horse, 223
    land, 222
    roads, 225

  Camouflage, ships, 211

  Cartridges, aircraft guns, 131

  Catapults, 36

  Caterpillar tractor, 109

  Caves, 8

  Coffer-dam, salvage, 318

  Color, analyzing, 229
    screens, 229

  Compass, wireless, 201

  Convoy, 267

  Countermines, 17


  Deep sea, conditions in, 312

  Deep water diving, 327

  Depth bombs, 265

  Devil's eggs, 276

  Diesel engine, 240

  Direction-finder, 205

  Dirigible, see Balloon

  Disease, caisson, 325

  Diver, armored suit, 330
    caisson disease, 325
    rest chamber, 328
    sled, 330
    submarine torch, 329
    suit, 324

  Diving, deep, 324
    record depth, 327

  Duck-boards, 9

  Dugouts, 7

  Dummy heads of papier mâché, 13


  Eagle boats, 301

  Egg-laying submarines, 287

  Eggs, Devil's, 276

  Electric motor-boat, 308

  Engine, Diesel, 240


  Field-guns, 81

  Fire broom, 105
    liquid, 103

  Forts, machine-gun, 58

  Fuse, grenade, 28


  Gas, 85
    American, 102

  Gas attack, boomerang, 92
    first, 89

  Gas, chlorine, 87
    diphosgene, 96
    exterminating rats, 94
    grenades, 26
    helium, 164
    hydrogen, 150
    lock, 97
    masks, 99
    mustard, 98
    phosgene, 93
    pouring like water, 86
    shell, 95
    sneezing, 98
    tear, 95
    vomiting, 98

  Gasolene-tank, airplane, 130

  Gate, barbed wire, trench, 9

  Gates through barbed wire, 15

  Gatling gun, 43

  Geologists, Messines Ridge, 19

  Glass, non-shattering, 100

  Grapnel shell, 16

  Graveyard, submarine, 314

  Grenade, disk-shaped, 33
    fuse, 28
    gas, 26
    hair brush, 34
    history of, 23
    Mills, 29
    parachute, 31
    range of, 25
    rifle, 28
    throwing implement, 27

  Grenade, wind-vane safety device, 32

  Gun, aircraft, 131
    American, 50-mile, 63
    big, hiding, 226
    caliber, 68
    disappearing, 77
    double-end, 145
    18-inch, monitors, 306
    elastic, 73
    field, 81
    42-centimeter, 79
    how made, 76
    120-mile, 70
    long range, German, 62
    non-recoil, 145
    on submarine, 249
    16-inch, coast defense, 78
    Skoda, 81
    spotting by sound, 181
    three-second life, 73
    12-inch, submarine, 251
    ways of increasing range, 67
    wire-wound, 76


  Hand-grenade, see Grenade

  Helium, 164

  Hospital, airplane, 147

  Horizon, seeing beyond, 219

  Howitzer, 79

  Hush ships, 304

  Hydroaëroplanes, see Seaplanes

  Hydrogen, weight of, 150

  Hydrophone, 270


  Illusions, optical, 215


  Kilometer, length in miles, 6

  Kite balloons, 174

  Kite, water, 283


  Liberty motor, 142

  Liquid-fire, 103

  Locomotives, gasolene, 10

  _Lusitania_, 316


  Machine-gun, 112
    airplane, 127
    Benèt-Mercié, 52
    Browning, 53
    Colt, 44
    forts, 58
    Gatling, 43
    history, 41
    Hotchkiss, 49
    Lewis, 50
    Maxim, 42
    water-jacket, 47
    worth in rifles, 58

  Machine-rifle, 55

  Magnets, lifting, salvage, 334

  Maps, making with camera, 175

  Marne, first battle of, 4

  Messines Ridge, mine, 19

  Metal-cutting under water, 329

  Microphone detectors, mines, 18

  Mine-field, North Sea, 290

  Mine laying, North Sea, 292

  Mine-laying submarine, 287

  Mine railroad, 294

  Mine-sweeping, 281

  Mines, 276
    anchored, 278
    and counter-mines, 17
    automatic sounding, 278
    drift of, 285
    electric, 277
    floating, 284
    Messines Ridge, 19

  Mines, paravanes, 288

  Monitors, 306

  Mortars, 79
    depth bomb, 266
    flying, 23

  Mortars, See also Trench mortars

  Mother-ships for airplanes, 305

  Motor-boat, electric, 308
    sea Tank, 299

  Motor torpedo-boats, 298

  Mystery ships, 220


  Net, North Sea, 290


  Ocean currents, 285

  Optical illusions, 215

  Oxy-hydrogen torch, submarine, 329


  Paint in war, 209

  Papier mâché heads, 13

  Papier mâché horse, 223

  Parachute, 175
    grenade, 31
    search-light shell, 84

  Paravanes, 288

  Periscope, submarine, 244
    trench, 11

  Pill-boxes, 59

  Pneumatic breakwater, 335

  Pontoons, salvage, 320

  Propeller, shooting through, 136


  Radio, see Wireless

  Railroad, mine, 294

  Railways, trench, 10

  Range-finder, 170

  Range, getting the, 169

  Range of guns, increasing, 67

  Range, torpedo, 213

  Rats, freeing trenches of, 94

  Rifle grenade, 28
    safety device, 32

  Rifle, machine, 55

  Rifle stand, fixed, 14

  Roads, camouflage, 225


  Salvage, 310
    diving, 324
    ice-tongs, 334
    lifting-magnets, 334
    methods, 317
    pneumatic, 319
    pontoons, 320
    shackles on ships, 333
    submarine F-4, 321
    submarine sphere, 332

  Scouts, airplane, 128

  Sea, deep, conditions, 312

  Sea gulls finding submarines, 258

  Sea lions locating submarines, 259

  Sea tank, 299

  Seaplane, 143
    automatic, 145
    submarine patrol, 259
    torpedo, 145
    towing-barges, 302

  Search-light shell, 84

  Shackles, salvage, 333

  Shadowless buildings, 227

  Shell, gas, 95
    grapnel, 16
    search-light, 84
    shrapnel, 83
    Stokes mortar, 39

  Shield on wheels, 114

  Ships, airplane, 304

  Ships, blisters, 307
    camouflage, 211
    "clothes-line," 220
    convoy, 267
    hush, 304
    making visible, 230
    monitors, 306
    mystery, 220
    railroads on, 294
    sunk by submarines, 310

  Ships, see also Salvage

  Shrapnel shell, 83

  Sled, submarine, 330

  Smoke screen, 262

  Sniper, locating, 13

  Sniperscopes, 12

  Sound, detecting submarines, 269

  Sound detectors, mines, 18

  Sound, spotting by, 181

  Sphere, salvor's submarine, 332

  Spotting by sound, 181

  Spotting gun-fire, 177

  Submarine, blindness, 244
    chasers, 255
    construction, 234
    depth bombs, 265
    egg-laying, 287
    engines, 246
    F-4, salving, 321
    getting best of, 253
    graveyard, 314
    guns on, 249
    history, 232
    hydrophone, 270
    mine-field, 290
    mine-laying, 287
    net, 290
    oil-tank, 236
    periscope, 244
    reclaiming victims of, 310
    rest chamber, 328
    salvage vessel, 332
    sea-gulls, 258
    sea-lions, 259
    seaplanes, 259
    ships sunk, 310
    sled, 330
    steam-driven, 250
    torch, 329
    torpedo, 246
    12-inch gun, 251
    vs. submarine, 269

  Super-guns, 62


  Tank, 107
    American, 122
    flying, 139
    French, 119
    German, 120
    one-man, 114
    sea, 299
    small, 121

  Telegraphy, rapid, 199

  Telephone, New York to San Francisco, 186
    wireless, 178

  _Titanic_, 314

  TNT (trinitrotoluol), 18

  Torch, submarine, 329

  Torpedo, 299
    boats, motor, 298
    electrically steered, 308
    construction, 246
    getting range, 213
    proof ships, 306
    seaplane, 145

  Towing-barge, seaplane, 302

  Trajectory, 22

  Trench, gas-lock, 97

  Trench mortar, 36
    pneumatic, 37
    Stokes, 38

  Trench railways, 10

  Trench warfare, 4

  Trenches, 21
    barbed wire gates, 9
    duck-boards, 9

  Tunnels, mines, 17
    to observation posts, 12


  U-boats, see Submarines


  Villages, underground, 7


  Walking-machine, 108

  War, paint, 209

  Water kites, 283

  Waves, fighting with air, 334

  Wireless compass, 201
    spy detector, 200

  Wireless telegraph, rapid, 199

  Wireless telegraphy explained, 188

  Wireless telephone, 178
    airplane, 184

  Wireless telephony across Atlantic, 192

  Woolworth Building, falling from, 135

  Wrecks, see Salvage


  Zeppelin and Lowe's balloon, 149

  Zeppelin balloon, construction, 156

  Zeppelin, suspended observer, 162

  Zeppelin's failures and successes, 154



      *      *      *      *      *      *



Transcribers' note:


Punctuation and spelling were made consistent when a predominant
preference was found in this book; otherwise they were not changed.

Simple typographical errors were corrected; occasional unbalanced
quotation marks retained.

Ambiguous hyphens at the ends of lines were retained.

Some illustrations have been slightly repositioned to improve their
appearance in eBooks.

Page 76: "eight tenths of an inch" may be a misprint for "eight
ten-thousandths of an inch".

Page 100: "inhaled air" was misprinted as "inhaled aid".

Page 104: "would send the stream" was misprinted as "sent".

Page 113: "Secretely" was printed that way.

Page 209: "psycologists" was printed that way.





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