<h2><SPAN name="CHAPTER_IV" id="CHAPTER_IV">CHAPTER IV</SPAN><br/> <span class="subhead"><span class="smcap">Guns and Super-Guns</span></span></h2>
<p class="drop-cap3"><span class="smcap1">When</span> 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.</p>
<h3>SHOOTING AROUND THE EDGE OF THE EARTH</h3>
<p>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<span class="pagenum"><SPAN name="Page_63" id="Page_63">63</SPAN></span>
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.</p>
<p>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<span class="pagenum"><SPAN name="Page_64" id="Page_64">64</SPAN></span>
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.</p>
<p>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 43½ 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.</p>
<h3>BEYOND THE EARTH'S ATMOSPHERE</h3>
<p>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.<span class="pagenum"><SPAN name="Page_65" id="Page_65">65</SPAN></span>
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.</p>
<p>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<span class="pagenum"><SPAN name="Page_66" id="Page_66">66</SPAN></span>
from earth and out in the endless reaches of
space.</p>
<p>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.</p>
<p><span class="pagenum"><SPAN name="Page_67" id="Page_67">67</SPAN></span></p>
<h3>WAYS OF INCREASING THE RANGE</h3>
<p>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<span class="pagenum"><SPAN name="Page_68" id="Page_68">68</SPAN></span>
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.</p>
<p>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.</p>
<div id="ip_68" class="figcenter" style="width: 535px;">
<ANTIMG src="images/i_068.jpg" width-obs="535" height-obs="345" alt="" /><br/>
<div class="captionl">Courtesy of "Scientific American"</div>
<div class="caption0">The 121-Mile Gun designed by American Ordnance Officers</div>
</div>
<p>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<span class="pagenum"><SPAN name="Page_69" id="Page_69">69</SPAN></span>
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.</p>
<div id="ip_69" class="figcenter" style="width: 526px;">
<ANTIMG src="images/i_069.jpg" width-obs="526" height-obs="350" alt="" /><br/>
<div class="captionl">(C) Underwood & Underwood</div>
<div class="caption0">American 16-Inch Rifle on a Railway Mount</div>
</div>
<p>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.</p>
<p>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<span class="pagenum"><SPAN name="Page_70" id="Page_70">70</SPAN></span>
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.</p>
<h3>A GUN WITH A RANGE OF A HUNDRED AND TWENTY MILES</h3>
<p>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<span class="pagenum"><SPAN name="Page_71" id="Page_71">71</SPAN></span>
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.</p>
<p>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.</p>
<p>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.</p>
<p>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.<span class="pagenum"><SPAN name="Page_72" id="Page_72">72</SPAN></span>
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.</p>
<p>The engraving facing page <SPAN href="#Page_68">68</SPAN> 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<span class="pagenum"><SPAN name="Page_73" id="Page_73">73</SPAN></span>
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.</p>
<h3>THE THREE-SECOND LIFE OF A GUN</h3>
<p>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.</p>
<h3>ELASTIC GUNS</h3>
<p>We had better go back with it and learn
something about the manufacture of a big gun.<span class="pagenum"><SPAN name="Page_74" id="Page_74">74</SPAN></span>
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.</p>
<p>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<span class="pagenum"><SPAN name="Page_75" id="Page_75">75</SPAN></span>
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.</p>
<p>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.</p>
<p><span class="pagenum"><SPAN name="Page_76" id="Page_76">76</SPAN></span></p>
<h3>HOW BIG GUNS ARE MADE</h3>
<p>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.</p>
<div id="ip_76" class="figcenter" style="width: 526px;">
<ANTIMG src="images/i_076.jpg" width-obs="526" height-obs="350" alt="" /><br/>
<div class="captionl">Photograph from Underwood & Underwood</div>
<div class="caption0">A Long-distance Sub-calibered French Gun on a Railway Mount</div>
</div>
<p>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<span class="pagenum"><SPAN name="Page_77" id="Page_77">77</SPAN></span>
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.</p>
<div id="ip_77" class="figcenter" style="width: 542px;">
<ANTIMG src="images/i_077.jpg" width-obs="542" height-obs="350" alt="" /><br/>
<div class="captionl">Courtesy of "Scientific American"</div>
<div class="container caption0 l2">Inside of a Shrapnel Shell and Details<br/>of the Fuse Cap</div>
<div class="container in4 caption0">Search-light Shell and<br/> one of its Candles</div>
</div>
<h3>GUNS THAT PLAY HIDE-AND-SEEK</h3>
<p>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.<span class="pagenum"><SPAN name="Page_78" id="Page_78">78</SPAN></span>
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.</p>
<p>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.</p>
<p>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 16¼-inch caliber
and 30-caliber length. In order to test the
penetrating-power of this gun a target was<span class="pagenum"><SPAN name="Page_79" id="Page_79">79</SPAN></span>
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.</p>
<h3>THE FAMOUS FORTY-TWO-CENTIMETER GUN</h3>
<p>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<span class="pagenum"><SPAN name="Page_80" id="Page_80">80</SPAN></span>
bore were built. These would fire at a high
angle, so that the projectile would fall almost
vertically on the target.</p>
<p>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 1½ yards
long. The diameter of the shell was 42 centimeters,
which is about 16½ 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<span class="pagenum"><SPAN name="Page_81" id="Page_81">81</SPAN></span>
"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.</p>
<h3>FIELD-GUNS</h3>
<p>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.</p>
<p><span class="pagenum"><SPAN name="Page_82" id="Page_82">82</SPAN></span></p>
<h3>GUNS THAT FIRE GUNS</h3>
<p>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.</p>
<p><span class="pagenum"><SPAN name="Page_83" id="Page_83">83</SPAN></span>
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 <SPAN href="#Page_77">77</SPAN>) strike a pin, <i>E</i>, which ignites the
train of powder, <i>A</i>. 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 <i>A</i>, and
then jumps through the short cut <i>B</i> to the other,
or movable train, as it is called, until it finally
reaches, through hole <i>C</i>, the main charge <i>F</i>, 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 <i>K</i>, which
will strike the primer <i>L</i> and explode the shell<span class="pagenum"><SPAN name="Page_84" id="Page_84">84</SPAN></span>
when the latter strikes the ground, if the time-fuse
has failed to act.</p>
<p>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.</p>
<div id="ip_84" class="figcenter" style="width: 542px;">
<ANTIMG src="images/i_084.jpg" width-obs="542" height-obs="347" alt="" /><br/>
<div class="captionl">(C) Committee on Public Information</div>
<div class="caption0">Putting on the Gas Masks to Meet a Gas Cloud Attack</div>
</div>
<p>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.</p>
<div class="center"><div class="container">
<div id="ip_85" class="figleft" style="width: 258px;">
<ANTIMG src="images/i_085.jpg" width-obs="258" height-obs="302" alt="" /><br/>
<div class="captionl">(C) Kadel & Herbert</div>
<div class="caption0">Even the Horses had to be Masked</div>
</div>
<div id="ip_85b" class="figright" style="width: 274px;">
<ANTIMG src="images/i_085b.jpg" width-obs="274" height-obs="300" alt="" /><br/>
<div class="captionl">Photograph by Kadel & Herbert</div>
<div class="caption0">Portable Flame-throwing Apparatus</div>
</div></div>
</div>
<hr />
<p><span class="pagenum"><SPAN name="Page_85" id="Page_85">85</SPAN></span></p>
<div style="break-after:column;"></div><br />
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