of two huge mortars, the idea of which presented itself to Mr. Mallet
during the Crimean War, the intention being to throw into the Russian
lines spherical shells a yard in diameter, which would, in fact, have
constituted powerful mines, rendering it impossible for the
fortifications to continue tenable. Mallet’s original design was to
project these shells from mortars of no less than 40 tons weight. When
it was pointed out that the transport of so heavy a mass would be
impracticable, the design was changed to admit of the mortar being made
in pieces not exceeding eleven tons in weight, and built up where
required. During the most active period in the siege of Sebastopol this
plan was submitted to Lord Palmerston, who at once ordered two of these
apparently formidable pieces to be constructed, without waiting for
official examinations of the scheme, and the usual reports of
experts,—promptness in this case being considered of the utmost
importance. A contract was made with a private firm, who undertook to
deliver them in ten weeks. But the difficulties attending such
constructions not being understood at the time, delays arose, the
contractors failed, and two years elapsed before the mortars were
completed. In the meantime peace had been concluded, and the mortars
were never fired against any hostile works; but experiments were made
with one of them at Woolwich. The heaviest of the shells it was intended
to project weighed 2,940 lbs., and for this it was proposed to use a
charge of 80 lbs. of gunpowder. In the experiments the charges first
used were low, but gradually increased: when it was found that after
every few rounds repairs became necessary in consequence of the weak
points in the construction, and after the nineteenth round the mortar
was so much damaged that the trials were definitely discontinued. The
other mortar, though mounted, was never fired, but remains at Woolwich,
an object of some interest to artillerists, especially since there has
been some talk of reverting to this very old-fashioned form of ordnance
as a means of attacking ironclads in their most vulnerable direction by
the so-called vertical fire. In one of the rounds of the Mallet mortar
tried at Woolwich, a shell weighing 2,400 lbs. was thrown by a charge of
70 lbs. of gunpowder a distance of more than a mile and a half, and it
buried itself in the soil to a very great depth.
[Illustration:
FIG. 103.—_Mallet’s Mortar_
]
For high-elevation firing, howitzers will more probably be the form of
ordnance most in use. The range of the howitzer is determined by the
angle at which it is elevated, whereas with the mortar it is chiefly by
variation of the powder charge that the aim is adjusted. Many of the old
short 9 in. muzzle-loaders have already been converted into 11 in.
rifled howitzers, and these are likely to prove of great service in
defending our harbours and channels against war vessels.
Some account has been given in a preceding article of the great steel
works of Krupp & Co. at Essen, and the place has been noted as one of
the greatest gun factories in the world during the second half of our
century. The process there practised of casting crucible steel ingots,
and already described, is precisely that used in the first stage of
gun-making. The steel for guns put into the crucibles is a carefully
adjusted mixture of one quality of iron puddled into steel and subjected
to certain treatment; the other portion is made from a different quality
of iron from which all the carbon has been puddled out. The cast ingot
is forged under a great steam hammer, bored, turned, and steel hoops
shrunk upon it, in several layers, and other operations are performed
upon it like those which have already been mentioned. A 14 in. gun is
said to require sixteen months for its manufacture, and its cost to be
about £20,000.
[Illustration:
FIG. 104.—_32–pounder Krupp Siege Gun, with Breech-piece open._
]
Artillerists had long carried on a warm controversy as to the relative
merits of wrought iron and steel in gun construction, the latter
material being regarded with shyness on account of its want of
uniformity as formerly produced. Krupp however began as early as 1847 to
make guns of his excellent crucible steel, and through bad report and
good report confined himself to this material until, it is asserted, by
1878 he had supplied over 17,000 steel guns of all calibres. He began by
making a 3–pounder gun, but soon produced pieces of larger size, all of
which were bored and turned out of solid masses of metal. At a later
period the plan of shrinking on strengthening hoops of steel was
adopted. The Krupp guns have found extensive favour, and many very heavy
ones have been made, some indeed of greater weight than the 110–ton
Armstrong; but the excess of weight is due to the mass of metal which
the Krupp construction of the breech mechanism requires. Thus Krupp’s
120–ton gun has a muzzle energy of but 45,796 foot-tons, while that of
the Elswick piece is 55,105 foot-tons.
[Illustration:
FIG. 105.—_The Citadel of Strasburg after the Prussian Bombardment._
]
The breech arrangement in the Krupp guns consists of a lateral slot into
which slides a closing block after the charge has been inserted from the
rear. An obsolete form of this breech piece is seen in Fig. 104, which
represents a 32–pounder gun such as was used in sieges by the Prussians
in the Franco-German War. It will be observed here that the slot and
breech piece are of rectangular form; but this shape, causing the piece
to be weak where most strength was required, was afterwards altered into
a D-shaped section, the curved side being of course to the rear. That
difficulty which baffled the earliest attempts at breech-loading is the
same that has given much trouble to modern gunmakers. It consists in so
closing the breech that no escape of the powder gases can take place
there at the moment of discharge. When we remember that the momentary
pressure of the gases in the powder chamber may amount to more than 40
tons on the square inch, we can well understand the enormous velocity
with which they will rush forth from even the smallest interspace
between the base of the gun and the breech block, but we can hardly
realise without actual inspection the mechanical action they produce in
their passage: when once the escape occurs, a channel is cut in the
metal as if part had been removed by an instrument, and the piece in
that condition is disabled for further use. Several devices are in use
obtaining perfect closure of the breech, which is technically called
_obturation_ (Latin, _obturare_, to close up). One of these consists in
fitting closely into the circumference of the bore a ring of very
elastic steel, turned up at the edges towards the powder chamber. The
gas pressure forces the edge of this ring still more closely against the
interior of the powder chamber, much in the same way as the Bramah
collar acts in the hydraulic press (see Fig. 165). The shaded circle
shown on the breech piece in Fig. 104 is an additional device for
obtaining obturation. The Broadwell ring, as the above-mentioned
contrivance is called, is not used in English guns, but another plan of
obtaining a gas-joint has been much adopted, in which a squeezable pad
is by compression forced outwards to close up the bore.
A very long range was claimed for Krupp’s guns at the time of the
Franco-German War, for at the siege of Paris (1870) it was said they
could hurl projectiles to the distance of five miles, though probably
there was some exaggeration in this statement. There is no doubt however
that the Prussians had very effective and powerful artillery, as may be
gathered from Fig. 105, which is taken from a photograph of part of the
fortifications of Strasburg after the bombardment of that fortress. The
explosive shells used by the Prussians against masses of troops were not
precisely segment shells of the form already described, but the
principle and effect were the same, for the interior was built up of
circular rings, which broke into many pieces when the shell exploded.
Out of the very numerous forms in which modern ordnance is constructed,
we have been able to select but a few examples for illustration and
description. These will suffice, it is hoped, to give an idea of the
progress that the century has witnessed. It would be beyond our scope to
give details of the ingenious mechanical devices that have come to be
applied to guns: such as the breech-closing arrangements, the various
ways in which recoil is controlled and utilized, etc. A good
illustration, had space permitted, of the scientific skill applied to
ordnance would be found in the contrivances fitted to certain
projectiles in order to determine their explosion at the proper moment.
These are very different from the cap or time fuse that did duty in the
first half of the century. We have indeed said little of the projectiles
themselves beyond mention of the Palliser chilled shot and the obsolete
studded projectiles. We have not explained how bands of copper, or other
soft metal, are put round a certain part of the shot or shell, in order
that, being forced into the grooves, the axial rotation may be imparted,
or how windage is prevented by “gas checks” attached to the base of the
projectiles. We must now be contented to conclude this section by
showing the structure of two kinds of explosive shells which have been
much used.
Shrapnel shell takes its name from Lieutenant Shrapnel, who was its
inventor about the end of last century, but the projectile began to be
used only in 1808. Fig. 105_a_ is a section showing the shell as a case
containing a number of spherical bullets, of which in the larger shells
there are very many, the interspaces being filled with rosin, poured in
when melted; the bullets are thus prevented from moving about. The
figure shows the shell without the fuse or percussion apparatus, which
screws into the hollow at the front. The bursting charge of gunpowder is
behind the bullets, and when it explodes they travel forward with a
greater velocity than the shell, but with trajectories more or less
radiating, carrying with them wide-spreading destruction and death.
A shrapnel shell may be said to be a short cannon containing its charge
of powder in a thick chamber at the breech end; the sides of the fore
part of the shell are thinner than those of the chamber, and may be said
to form the barrel of the cannon. This cannon is loaded up to the muzzle
with round balls, which vary with the shell in size. An iron disc
between the powder and the bullets represents the wad used in ordinary
fowling-pieces. A false conical head is attached to the shell, so that
its outward appearance is very similar to that of an ordinary
cylindro-conoidal shell: that is to say, it looks like a very large long
Enfield bullet. The spinning motion which had been communicated to the
shell by the rifling of the gun from which it had been fired causes the
barrel filled with bullets to point in the direction of the object at
which the gun has been aimed. Consequently, when the shrapnel shell is
burst, or rather fired off, the bullets which it contained are streamed
forward with actually greater velocity than that at which the shell had
been moving; and the effect produced is similar to firing grape and
canister from a smooth-bore cannon at a short range.
[Illustration:
FIG. 105_a_.—_The Shrapnel and Segment Shells._
]
Segment shells were first brought into use by Lord Armstrong in 1858 in
connection with his breech-loading guns. The segment shell consists of a
thin casing like a huge conical-headed thimble, with a false bottom
attached to it. It is filled with small pieces of iron called
“segments,” cast into shapes which enable them to be built up inside the
outer casing into two or more concentric circular walls. The internal
surface of the inmost wall forms the cavity of the compound or segment
shell, and contains the bursting charge. The segment shell is fitted
with a percussion fuse, which causes it to explode when it strikes. In
the shrapnel shell, the powder charge is situated in rear of the
bullets, and consequently produces the chief effect in a forward
direction. In the segment shell, the powder is contained inside the
segments, and therefore produces the chief effect in a lateral
direction. When the shrapnel shell is burst at the right moment, its
effect is greatly superior to that of the segment shell; on the other
hand, the segment shell, when employed at unknown or varying distances,
is far more unlikely to explode at the proper time.
Shrapnel and segment shells can be used with field artillery, _i.e._,
9–pounders, 12–pounders, 16–pounders; and also with heavy rifled guns in
fortresses, viz., 40–pounders, 64–pounders, 7–in. and 9–in. guns. But
the conditions of their service are very different in each case. With
regard to field artillery, the distance of the enemy is rarely known,
and is constantly changing, and hence the men who have to adjust the
fuses would probably be exposed to the fire of the enemy’s artillery,
and, consequently, could not be expected to prepare the fuses with the
great care and nicety which are absolutely necessary to give due effect
to the shells. There are, however, some occasions when the above
objections would not hold good—as, for instance, when field artillery
occupy a position in which they wait the attack of an enemy advancing
over ground in which the distances are known.
Segment shells require no adjustment of their percussion fuse. They
enable the artillerymen to hit off the proper range very quickly, since
the smoke of the shell which bursts on striking tells them at once
whether they are aiming too high or too low.
With regard, however, to the service of heavy rifled guns in fortresses,
the conditions are quite different. In the first place, the distance of
all objects in sight would be well known beforehand; and in the second
place, the fuses of the shells would be carefully cut to the required
length in the bomb-proofs, where the men would be completely sheltered.
The 7–in. shrapnel contains 227 bullets, and a 9–in. shrapnel would
contain 500 bullets of the same size, and these shells could be burst
with extraordinary accuracy upon objects 5,000, 6,000, or 7,000 yards
off.
_MACHINE GUNS._
The name of machine guns has been applied to arms which may be regarded
as in some respects intermediate between cannons and rifles, since in
certain particulars they partake of the nature of both. Like the former,
they are fired from a stand or carriage, and in some of their forms
require more than one man for their working: in the calibre of their
barrels and the weight of their projectiles, they are assimilated to the
rifle, but they are capable of pouring forth their missiles in a very
rapid succession—so rapid indeed as practically to constitute volley
firing. The firing mechanism of the machine gun has always an automatic
character, but the rifle has acquired this feature, so that it cannot be
made a distinguishing mark: on the other hand, since machine guns have
been made to discharge projectiles of such weights as 1 lb. or 3 lb.
there is nothing to separate them from quick-firing ordnance unless it
be the automatic firing.
The idea of combining a number of musket-barrels into one weapon, so
that these barrels may be discharged simultaneously or in rapid
succession, is not new. Attempts were made two hundred years ago to
construct such weapons; but they failed, from the want of good
mechanical adjustments of their parts. Nor would the machine gun have
become the effective weapon it is, but for the timely invention of the
rigid metallic-cased cartridge. Several forms of machine guns have in
turn attracted much attention. There is the Mitrailleur (or
Mitrailleuse), of which so much was heard at the commencement of the
Franco-German War, and of whose deadly powers the French managed to
circulate terrible and mysterious reports, while the weapon itself was
kept concealed. Whether this arose from the great expectations really
entertained of the destructive effects of the mitrailleur, or whether
the reports were circulated merely to inspire the French troops with
confidence, would be difficult to determine. Our own policy in regard to
new implements of war is not to attempt to conceal their construction.
Experience has shown that no secret of the least value can long be
preserved within the walls of an arsenal, although the French certainly
apparently succeeded in surrounding their invention with mystery for a
while. The machine gun, or “battery,” invented by Mr. Gatling, an
American, is said by English artillerists to be free from many defects
of the French mitrailleur. In 1870 a committee of English military men
was appointed to examine the powers of several forms of mitrailleur,
with a view to reporting upon the advisability or otherwise of
introducing this arm into the British service. They recommended for
certain purposes the Gatling battery gun.
[Illustration:
FIG. 105_b_.—_The Gatling Gun.—Rear View._
]
In the Gatling the barrels, ten in number, are distinct and separate,
being screwed into a solid revolving piece towards the breech end, and
passing near their muzzles through a plate, by which they are kept
parallel to each other. The whole revolves with a shaft, turning in
bearings placed front and rear in an oblong fixed frame, and carrying
two other pieces, which rotate with it. These are the “carrier” and the
lock cylinder. Fig. 105_b_ gives a rear view, and Fig. 105_c_ a side
view, of the Gatling battery gun. The weapon is made of three sizes, the
largest one firing bullets 1 in. in diameter, weighing ½ lb., the
smallest discharging bullets of ·45 in. diameter. The small Gatling is
said to be effective at a range of more than a mile and a quarter, and
can discharge 400 bullets or more in one minute. Mr. Gatling thus
describes his invention:
“The gun consists of a series of barrels in combination with a grooved
carrier and lock cylinder. All these several parts are rigidly secured
upon a main shaft. There are as many grooves in the carrier, and as many
holes in the lock cylinder, as there are barrels. Each barrel is
furnished with one lock, so that a gun with ten barrels has ten locks.
The locks work in the holes formed in the lock cylinder on a line with
the axis of the barrels. The lock cylinder, which contains the lock, is
surrounded by a casing, which is fastened to a frame, to which trimmers
are attached. There is a partition in the casing, through which there is
an opening, and into which the main shaft, which carries the lock
cylinder, carrier, and barrels, is journaled. The main shaft is also at
its front end journaled in the front part of the frame. In front of the
partition in the casing is placed a cam, provided with spiral surfaces
or inclined planes.
“This cam is rigidly fastened to the casing, and is used to impart a
reciprocating motion to the locks when the gun is rotated. There is also
in the front part of the casing a cocking ring which surrounds the lock
cylinder, is attached to the casing, and has on its rear surface an
inclined plane with an abrupt shoulder. This ring and its projection are
used for cocking and firing the gun. This ring, the spiral cam, and the
locks make up the loading and firing mechanism.
“On the rear end of the main shaft, in rear of the partition in the
casing, is located a gear-wheel, which works to a pinion on the
crank-shaft. The rear of the casing is closed by the cascable plate.
There is hinged to the frame in front of the breech-casing a curved
plate, covering partially the grooved carrier, into which is formed a
hopper or opening, through which the cartridges are fed to the gun from
feed-cases. The frame which supports the gun is mounted upon the
carriage used for the transportation of the gun.
“The operation of the gun is very simple. One man places a feed-case
filled with cartridges into the hopper; another man turns the crank,
which, by the agency of the gearing, revolves the main shaft, carrying
with it the lock cylinder, carrier, barrels, and locks. As the gun is
rotated, the cartridges, one by one, drop into the grooves of the
carrier from the feed-cases, and instantly the lock, by its impingement
on the spiral cam surfaces, moves forward to load the cartridge, and
when the butt-end of the lock gets on the highest projection of the cam,
the charge is fired, through the agency of the cocking device, which at
this point liberates the lock, spring, and hammer, and explodes the
cartridge. As soon as the charge is fired, the lock, as the gun is
revolved, is drawn back by the agency of the spiral surface in the cam
acting on a lug of the lock, bringing with it the shell of the cartridge
after it has been fired, which is dropped on the ground. Thus, it will
be seen, when the gun is rotated, the locks in rapid succession move
forward to load and fire, and return to extract the cartridge-shells. In
other words, the whole operation of loading, closing the breech,
discharging, and expelling the empty cartridge-shells is conducted while
the barrels are kept in continuous revolving movement. It must be borne
in mind that while the locks revolve with the barrels, they have also,
in their line of travel, a spiral reciprocating movement; that is, each
lock revolves once and moves forward and back at each revolution of the
gun.
“The gun is so novel in its construction and operation that it is almost
impossible to describe it minutely without the aid of drawings. Its main
features may be summed up thus: 1st.—Each barrel in the gun is provided
with its own independent lock or firing mechanism. 2nd.—All the locks
revolve simultaneously with the barrels, carrier, and inner breech, when
the gun is in operation. The locks also have, as stated, a reciprocating
motion when the gun is rotated. The gun cannot be fired when either the
barrels or locks are at rest.”
There is a beautiful mechanical principle developed in the gun, viz.,
that while the gun itself is under uniform constant rotary motion, the
locks rotate with the barrels and breech, and at the same time have a
longitudinal reciprocating motion, performing the consecutive operations
of loading, cocking, and firing without any pause whatever in the
several and continuous operations.
The small Gatling is supplied with another improvement called the “drum
feed.” This case is divided into sixteen sections, each of which
contains twenty-five cartridges, and is placed on a vertical axis on the
top of the gun. As fast as one section is discharged, it rotates, and
brings another section over the feed aperture, until the whole 400
charges are expended.
[Illustration:
FIG. 105_c_.—_The Gatling Gun.—Front View._
]
After a careful comparison of the effects of field artillery firing
shrapnel, the committee concluded that the Gatling would be more
destructive in the open at distances up to 1,200 yards, but that it is
not comparable to artillery in effect at greater distances, or where the
ground is covered by trees, brushwood, earthworks, &c. The mitrailleur,
however, would soon be knocked over by artillery if exposed, and
therefore will probably only be employed in situations under shelter
from such fire. An English officer, who witnessed the effects of
mitrailleur fire at the battle of Beaugency, looks upon the mitrailleur
as representing a certain number of infantry, for whom there is not room
on the ground, suddenly placed forward at the proper moment at a
decisive point to bring a crushing fire upon the enemy. Many other
eye-witnesses have spoken of the fearfully deadly effect of the
mitrailleur in certain actions during the Franco-German War.
Mr. Gatling contends that, shot for shot, his machine is more accurate
than infantry, and certainly the absence of nerves will ensure
steadiness; while so few men (four) are necessary to work the gun that
the exposure of life is less. No re-sighting and re-laying are necessary
between each discharge. When the gun is once sighted its carriage does
not move, except at the will of the operator; and the gun can be moved
laterally when firing is going on, so as to sweep the section of a
circle of 12° or more without moving the trail or changing the wheels of
the carriage. The smoke of battle, therefore, does not interfere with
its precision.
Whatever may be the part this new weapon is destined to play in the wars
of the future, we know that every European Power has now provided itself
with some machine guns. The Germans have those they took from the
French, who adhere to their old pattern. The Russians have made numbers
of Gatlings, each of which can send out, it is said, 1,000 shots per
minute, and improvements have been effected, so as to obtain a lateral
sweep for the fire.
[Illustration:
FIG. 105_d_.—_The Montigny Mitrailleur._
]