[_Concluded._]
[Illustration: GUN COTTON SHELL AFTER IMPACT.]
It is apparent that the range of even the most highly perfected
torpedo is comparatively short, while their accuracy of travel is low.
Besides, their propelling, controlling, and discharging mechanisms are
complicated, delicate, and easily deranged, they are very expensive,
and not only the explosive chamber but the entire system is destroyed
in use. The superiority of gunpowder guns as a means of throwing
projectiles to great distances with accuracy is well known, and
their capacity for safely and efficiently projecting shells filled
with gunpowder has long been demonstrated. It was obvious that as
the superior destructive power of dynamite, gun cotton, and other
high explosives became known and their commercial manufacture was
assured, attempts would be made to employ them as bursting charges
for shells. Experiments to demonstrate how this might be done and
what effects could be expected were begun more than forty years ago,
and have been continued in many different places from time to time
ever since; but while it has proved that small charges might be
fired with low velocities and pressures in ordinary shell, and large
charges in specially constructed shell or in specially prepared forms
of charge, with comparative safety so far as the premature explosion
of the explosive charge itself is concerned, yet these bodies are so
sensitive to the shock resulting from the discharge of the propellant,
the heat generated by its combustion, and that arising from friction
in the “set-back” of the shell charge and the rotation imparted by
the rifling, that they can not be safely fired from modern high-power
guns under service conditions, particularly as these explosives all
require that the shell shall be fitted with a detonator in order that
the charge may be fully exploded. The most promising results with
explosives of this class have been obtained with compressed wet gun
cotton, which has been packed directly in the shell in rigid blocks
completely filling the shell cavity, or cut in cubes and cemented in
the cavity with carnauba wax, for shell filled in the former manner,
but unfused, were repeatedly fired, in 1887 and 1888, at Newport, R.
I., from 24-pounder Dahlgren howitzers and 20-pounder muzzle-loading
rifles with service charges of powder, and though they were fired
point blank into the masonry escarpment of the old fort on Rose
Island, but fifty yards distant from the muzzle, so that the shells
were broken up or distorted and the gun cotton in them subjected to a
powerful compression, yet not only was there no premature explosion,
but none of the shell exploded by impact. About the same time fused
shell containing cemented gun cotton were fired in Germany, with an
initial velocity of fourteen hundred feet per second, and they passed
completely through four inches and three quarters of compound armor,
backed with twenty-four inches of oak, and burst inside the bombproof,
while in 1897 fused armor-piercing shells containing wet gun cotton
were fired from the six-inch quick-firing gun, with a muzzle velocity
of nearly nineteen hundred feet per second, which completely perforated
three inches of steel and burst behind the plate. Encouraged by these
results, this system was adopted by our army officials, but, on trial
in larger calibers at Sandy Hook, it gave rise to premature explosions,
and the tale of disaster reached its climax on April 29, 1899, when
Captain Stuart, of the Ordnance Corps, was superintending the loading
of a twelve-inch torpedo shell with wet gun cotton by compressing
it into the shell, for an explosion resulted which killed four men
instantly and fatally wounded two others, Captain Stuart being one of
them.
[Illustration: SIMS-DUDLEY PNEUMATIC GUN, LIMBERED UP.
(Courtesy of the Scientific American.)]
[Illustration: SIMS-DUDLEY PNEUMATIC GUN, IN BATTERY.
(Courtesy of the Scientific American.)]
[Illustration: TYNDALL’S BRONZE BELL-MOUTHED GUN.]
The history of the attempts made to use nitroglycerin, dynamite,
explosive gelatin, and explosives of this class as bursting charges
for shell fired from service guns is even less satisfactory than that
given for gun cotton. It is not surprising, therefore, that inventors
should have proposed catapults, slings, rotary wheels, and other means
for projecting these powerful agents into the enemy’s midst, but the
Mefford air gun, as mounted on the United States steamship Vesuvius,
and the Sims-Dudley gun, in which a reduced charge of powder is fired
in a chamber exterior to the gun proper, were deemed to possess
sufficient merit to warrant their trial in the field. These devices
were employed in the recent war with Spain, the pneumatic guns on the
Vesuvius being used to throw shells containing three hundred pounds of
gun cotton, while the Sims-Dudley guns were used on land to throw small
charges of dynamite or explosive gelatin; but, beyond frightening the
enemy by the startling character of their reports, these superficial
charges produced no serious effect.
[Illustration: MIRROR OR REFLECTOR IN WHICH TO FIRE GUN COTTON.]
There is a widespread misapprehension in regard to the devastating
effect of these high explosives, for when unconfined the effect even of
large charges of them upon structures is comparatively slight. At the
Naval Ordnance Proving Ground, so long ago as 1884, repeated charges
of dynamite, varying from five pounds to one hundred pounds in weight,
were detonated on the face of a vertical target consisting of eleven
one-inch wrought-iron plates bolted to a twenty-inch oak backing, until
440 pounds of dynamite had been so detonated in contact with it, and
yet the target remained practically uninjured; while at Braamfontein
the accidental explosion of fifty-five tons of blasting gelatin, which
was stored in railway vans, excavated but 30,000 tons of soft earth.
This last may seem a terrible effect, but the amount of explosive
involved was enormous and the material one of the most energetic that
we possess, while if we compare it with the action of explosives when
confined its effect becomes quite moderate. Thus at Fort Lee, on the
Hudson, but two tons of dynamite placed in a chamber in the rock and
tamped brought down 100,000 tons of the rock; at Lamberis, Wales,
two tons and a half of gelatin dynamite similarly placed threw out
180,000 tons of rock; and at the Talcen Mawr, in Wales, seven tons of
gunpowder, placed in two chambers in the rock, dislodged from 125,000
to 200,000 tons of rock. We might cite many such examples, but on
comparing these we find that the gunpowder confined in the interior at
the Talcen Mawr was over forty-two times as efficient as the explosive
gelatin on the surface at Braamfontein, while the dynamite at Fort Lee
was over ninety times as destructive.
[Illustration: RAILROAD TORPEDOES FASTENED ON RAIL.]
[Illustration: STEEL DISKS UPON WHICH GUN COTTON HAS BEEN DETONATED TO
TEST THEIR RESISTANCE TO SHOCK. Midvale steel disks after second fire.]
Considerations similar to these led me, in 1885,[H] to point out that
high explosives for use in shells must be strongly confined, and in
the attack on armored ships they should be fired in projectiles that
can “either penetrate the armor partially and explode in place or
pierce it completely and burst inside the ship” to secure the greatest
efficiency. This requires that the projectiles shall be fired at
higher velocities than can be imparted to them by guns of the kind
just described, and which can only be realized at present in modern
breech-loading rifles. Although experience has shown the futility of
all our efforts to use gun cotton and nitroglycerin explosives in this
manner, it has been proved that the nitro-substitution explosives can
be employed with safety and effect.
[H] Van Nostrand’s Engineering Magazine, vol. xxxii, pp. 1-9,
1885.
The nitro-substitution explosives are made from nitrobenzenes,
nitrotoluenes, nitronaphthalenes, nitrophenols, and bodies of a similar
character, and one of them, called joveite, has given excellent results
in this country. After having demonstrated that the destructive effect
of joveite was greater than that of gunpowder, smokeless powder, or gun
cotton, and, by repeated trials under severe conditions, that service
shell loaded with it could be fired from service guns under service
conditions with safety, on November 3, 1897, the naval officials
at Indian Head fired a fused ten-inch Carpenter armor-piercing
projectile containing 8.25 pounds of joveite, with a velocity of 1,960
foot-seconds, at a Harveyized nickel-steel plate taken from the armor
for the United States steamship Kentucky. The shell passed completely
through the armor plate, where it was 14.5 inches in thickness, and
burst immediately behind the plate. In a second round an unfused
ten-inch Midvale semi-armor-piercing shell containing twenty-eight
pounds of joveite was fired with a velocity of 1,925 foot-seconds at
the same plate where it was sixteen inches thick. The shell penetrated
to a depth of twelve inches, and the heat produced by the upsetting of
the shell was so great as to explode the joveite, which broke the plate
and burst the shell with tremendous violence. In fact, the explosion
was so very severe that the heavy base plug of the shell was sheared
longitudinally, an effect never observed before with any explosive
fired at the proving ground.
[Illustration: SHOOTING AN OIL WELL WITH NITROGLYCERIN.]
Notwithstanding that no accident occurred in any of the many firings,
that the stability and safety of the explosive are assured, and that
the explosion has been effected with a well-known and long-used form
of fuse, no provision has yet been made to supply the service with
charges for its costly armor-piercing projectiles.
Happily, the force resident in explosives may be applied to the
saving as well as to the destruction of human life, advantage having
long since been taken of the penetrating power of the report from
the discharge of a gun to employ them as signals of distress at sea
or as warnings in foggy weather. The English Lighthouse Board, under
Professor Tyndall’s guidance, some years ago sought to find the form
of gun best suited to this purpose, and their experiments led them at
first to a bronze gun with a bell-shaped mouth. Subsequently, their
attention being called to the sharpness and carrying power of the
report from detonating gun cotton, an apparatus was devised in which
the gun cotton was detonated in the focus of a parabolic mirror. The
best results, however, were attained with rockets carrying gun cotton
charges arranged to be exploded in mid air.
[Illustration: SAFE TO BE OPENED BY DETONATION OF NITROGLYCERIN. Before
the charge was fired.]
[Illustration: AFTER FIRING CHARGE.]
Guns have also been arranged for projecting life-lines between stranded
ships and the adjacent shore, and are now employed on a smaller scale
for conveying lines to the upper stories of our monumental buildings
when they are on fire. By means of guns or rockets, projectiles filled
with oil may be cast to considerable distances from a vessel in a
raging sea, so that the oil, as it diffuses, may still the waters in
her course; while sounding-lines may be thrown far in advance of a
vessel while she is still under way, and the soundings taken without
her laying-to.
Inclosed in shallow tin boxes, which are fixed by lead strips to the
top of the rail, explosives are used as torpedoes in the railroad
service to give warning, by the report of their explosion as an engine
runs over them, that another train is on the same track and but a short
distance ahead, and by this means collisions in fogs or on curves are
frequently prevented.
Explosives find applications in many industries. The farmer uses them
in breaking bowlders, grubbing stumps and felling trees, in shaking
the soil to fit it for deep-soil cultivation, and, in the wine-growing
districts, to free it from phylloxera, while the farmer’s friend has
tried by this means, in times of drought, to shake the nerves of Jove
and to divert the hailstorm from its course.
[Illustration: SAFE PERFORATED BY HOLLOW DYNAMITE CARTRIDGE.]
The iron founder uses them in breaking up large castings. The iron
smelter employs them to clear out obstructions in blast furnaces while
the latter are still in operation, the dynamite, protected by a clay
envelope, being inserted in the red-hot mass which clogs the furnace.
The author has proposed to use the detonating explosives for testing
the integrity of large masses of metals and their resistance to shock.
Dynamite has been employed in fishing, since submarine explosions of
it will kill or stun fish for a long distance about the charge. This
method of fishing, which threatened to deplete the waters, has very
properly been prohibited by law, but guns are employed for projecting
harpoons in the whale fishery, and have reduced very much the danger
attending this extra-hazardous occupation.
Nitroglycerin, inclosed in tin cans three to five inches in diameter
and five to twenty-five feet in length, is used for shooting oil wells
to free them from the solid paraffins with which they become choked, or
to shake the oil-bearing sandstone so as to produce a greater yield. In
this work the loaded can, having a detonating cap attached to its top,
is lowered by a wire to the bottom of the well, which is often fifteen
hundred feet or more in depth. A perforated weight is then strung on
the wire, and when the torpedo is in place the weight is allowed to
fall, strike the cap, and explode the charge.
Dynamite has been used to knock out the blocking from the ways when
launching ships. Fired on an iron plate placed on the top of a pile
and covered with a tamping of earth or clay, it has successfully and
economically replaced the pile driver. It has been found efficient in
excavating holes in which to plant telegraph and telephone poles; in
driving water out of quicksands in which foundations are to be laid
or shafts to be driven; in slaughtering cattle; in breaking down ice
dams to prevent inundations; in blowing up buildings to prevent the
spread of conflagrations; in razing unsafe walls of burned buildings;
in destroying wrecks which endanger navigation, and even in freeing
vessels which are hard aground on shoals.
[Illustration: HOLLOW DYNAMITE CARTRIDGE; ELEVATION.]
An especially notable instance was in the blasting out of the _débris_
in the river at Johnstown after the frightful flood that occurred
there, which formed an enormous dam above the bridge and threatened
its existence, and which was successfully and expeditiously removed by
blasting after all other means had been tried in vain.
[Illustration: HOLLOW DYNAMITE CARTRIDGE.