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Page 18
These shells are used in long guns up to 6 and 81/2 inches caliber, and
in mortars up to 11.2 inches. They are made from disks of steel, 3 to
4 feet in diameter and 1 inch thick, and are forced into shape by
hydraulic presses. The base is usually screwed in, but some of the
German shell are made in two halves which screw together. The Italians
were the first in this new field of investigation, but the Germans
soon followed, and after trying various materials were at length
reasonably successful with gun-cotton soaked in paraffin. Their 8.4
inch mortar shells of 5 calibers contain 42 pounds; those of 6
calibers contain 57 pounds; and the 11.2 inch mortar shells of 5
calibers contain 110 pounds.
The projectile velocity used with the mortars is about 800 f.s. The
effect of these shells against ordinary masonry and earth
fortifications is very great. The charge of forty-two pounds has
broken through a masonry vault of three feet four inches thick,
covered with two feet eight inches of cement and with three to five
feet of earth over all. The shell containing fifty-seven pounds, at a
range of two and one-half miles, broke through a similar vault covered
with ten feet of earth; but with seventeen feet of earth the vault
resisted. In 1883, experiments at Kummersdorf showed that a shell
containing the fifty-seven pound charge would excavate in sand a
crater sixteen feet in diameter and eight feet deep, with a capacity
of twenty-two cubic yards. The Italians have had similar experiences;
but it is notable that in both Germany and Italy several guns and
mortars have burst. The velocity in the guns is not believed to exceed
1,200 to 1,300 f.s., and it is not thought that the quantity of
gun-cotton is as great in the gun shells as in the mortars. I have
lately been informed on good authority that the use of gun-cotton
shells has been abandoned in the German navy as too dangerous.
The French, in their investigations in this field, found gun-cotton
too inconvenient, and decided upon melenite. This substance has
probably attracted more attention in the military world than all
others combined, on account of the fabulous qualities that have been
ascribed to it. Its composition was for a long time entirely a secret;
but it is now thought to consist principally of picric acid, which is
formed by the action of nitric acid upon phenol or phenyillic alcohol,
a constituent of coal tar. The actual nature of melenite is not
positively known, as the French government, after buying it from the
inventor, Turpin, are said to have added other articles and improved
it. This is probable, since French experiments in firing against a
partially armored vessel, the Bellequense, developed an enormous
destructive effect, while the English, who afterward bought it,
conducted similar experiments against the Resistance, and obtained no
better results than with powder. The proof that the Bellequense
experiments were deemed of great value by the French lies in the fact
that they immediately laid down a frigate--Dupuy de Lome--in which
four-inch armor is used, not only on the side, but about the gun
stations, to protect the men; this thickness having been found
sufficient to keep out melenite shell. In most armorclads, the armor
is very heavy about the vitals, but the guns are frequently much
exposed.
The best authenticated composition for melenite consists of picric
acid, gun cotton and gum arabic, and lately it is stated that the
French have added cresilite to it. Cresilite is another product of
coal tar. Melenite is normally only three times as strong as
gunpowder; but it is said to owe its destructive qualities in shells
to the powerful character of the exploder which ignites it. It has
been known for some years that all explosives (including gunpowder)
are capable of two orders of explosion according as they are merely
ignited or excited by a weak fuse or as they are powerfully shocked by
a more vigorous excitant. Fulminate of mercury has been found most
serviceable for the latter purpose. With melenite the French have
reproduced all the results that the Germans have effected with
gun-cotton and have found that a shell containing 119 pounds of it
will penetrate nearly ten feet of solid cement, but will not penetrate
armored turrets six to eight inches thick. The French claim that
melenite has an advantage over gun-cotton in not being so dangerous to
handle and being insensible to shock or friction, and they have
obtained a velocity of 1,300 f.s. with the 88 inch mortar and claim to
have obtained 2,000 f.s. in long guns up to 62 inch caliber. However
this may be, they are known to have had severe accidents at the
manufactory at Belfort and at least one 56 inch gun was burst at the
Bellequense experiments in firing a sixty-six pound shell containing
twenty-eight pounds of melenite. The French are said to have large
quantities of melenite shells in store, but they are not issued to
service.
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