Gun-carriage, Flank Casemate. See [Flank Casemate Carriage].
Gun-carriage, Mountain. See [Ordnance, Carriages for].
Gun-carriage, Prairie. See [Ordnance, Carriages for].
Gun-carriage, Sea-coast. See [Ordnance, Carriages for].
Gun-carriage, Siege. See [Ordnance, Carriages for].
Gun-cotton, or Pyroxyle. Gun-cotton was discovered by Schönbein in 1846, and was first made by treating ordinary cotton with a mixture of nitric and sulphuric acids. The product resembles ordinary cotton in appearance, but in color is slightly tinged with yellow, and is very much heavier. It explodes with great violence, but is unfit for most military purposes on account of its liability to spontaneous explosion, its corroding residue, and the irregular character of its explosion. Baron von Lenk, of the Austrian service, however, succeeded to some extent in regulating the suddenness of the explosion by twisting it into ropes, and weaving it into cloth, but it never came much into favor for military purposes. As first made, the length of time necessary for its manufacture was about two or three months, but Mr. Abel, of the British war office, has by a series of experiments materially decreased the time necessary for its manufacture, and greatly increased the safety and certainty of the product. At Favesham the manufacture of a peculiar kind of gun-cotton, known as tonite, is conducted on a large scale. The process consists in intimately mixing the ordinary gun-cotton with about an equal weight of nitrate of baryta. This compound is then compressed into candle-shaped cartridges, formed with a recess at one end for the reception of a fulminate of mercury detonator. It contrasts favorably with soft, plastic dynamite from the fact of its being easily fastened to the safety-fuze. Among its advantages, said to be due to the use of the nitrate, are that it contains a great amount of oxygen in a very small volume, and that it is very ready under the detonator, while its great density makes it slow to the influence of ordinary combustion. It is 30 per cent. stronger than ordinary gun-cotton, and takes up but two-thirds of its space, or the same space as dynamite. The cartridges are generally made water-proof. The projectile force of gun-cotton, when used with moderate charges, is equal to about twice its weight of the best gunpowder. Its explosive force is in a high degree greater than that of gunpowder, and in this respect its nature assimilates much more to the fulminates than to gunpowder. It evolves little or no smoke, as the principal residue of its combustion is water and nitrous acid. Recently, by the mixture of nitre and cane-sugar its quickness in action has been reduced so as to make it available for use in small-arms. The nitrous acid, however, will soon corrode the barrel if the piece is not carefully wiped after firing. Other explosive substances analogous to gun-cotton may be prepared from many organic bodies of the cellulose kind, by immersing them in the same bath as for gun-cotton; among these may be mentioned paper, tow, sawdust, calico, and wood fibre.
Gundermuk. A village of Afghanistan, 28 miles west from Jellalabad. Here the remnant of the British force, consisting of 100 soldiers and 300 camp-followers, were massacred in 1842, while retreating from Cabul (Cabool), only one man escaping.
Gun-fire. The hour at which the morning or evening gun is fired.
Gun-lift. The gun-lift recently devised by Col. Laidley, of the U. S. Ordnance Corps, is a most complete and rapid means for moving and dismounting heavy guns. In it the hydraulic jack is placed upon a stand over the gun, whereby the building-up of the crib-work of blocks, which serves as a base for the jack to stand on, is dispensed with, and the position of the jack has not to be changed during the operation of raising or lowering a gun. The ordinary carpenter’s horse or trestle is taken as the basis of the [hoisting] apparatus. The cap of the trestle, having to sustain the weight of the gun suspended at a distance of more than 2 feet from the points of support, is a large, strong, and heavy piece of timber, and the legs of the trestle have to be strongly braced. The bolster, a strong piece of oak on top of the cap of the trestle, has two mortices cut in it, one for a hoisting-bar to pass through, and the other for the fulcrum-post to rest in. The fulcrum-post has a recess cut on the top to receive the end of a lever and keep it in place. The lever has a mortice through which the hoisting-bar, already mentioned, passes; the latter is perforated with a series of holes through which a pin passes, by which the end of the lever, under which the hydraulic jack works, can be fastened to the hoisting-bar. The hoisting-bar has a hook on its lower end to which the weight to be raised is fastened by means of a sling.
Gun-metal. An alloy of nine parts of copper and one part of tin, used for brass cannon, etc. (See [Bronze]). The name is also given to certain strong mixtures of cast iron.