The mortar differs from all other guns in its solidity of form, its shortness, and its large bore. The object is the projection of shells by a more or less vertical fire, with the intention of breaking through and destroying, by weight and explosion together, roofs of magazines, public buildino-s, and so on, or of sinking a shell deep into earth works of a fortress, in which it silt]] explode as a most deadly mine. The different sorts of mortar will be described under MORTAR. The mortar arose naturally out of the old bombard, and doubtless deviated by degrees more and more from the cannon. In very early days, we read iu Arabian authors of a cylinder hewn in the rock at Alexandria, and used as a mortar. Such a cylinder, and of large size, is still to be seen at Gibraltar, where it was employed in the last siege against the Spanish, when it was made to discharge volleys of large stones, which spreading at times to a distance of 500 yards, constituted a formidable means of defense. In recent years, nearly all guns fire shells, so that the specific necessity for mortars has greatly diminished.
A gun is a frustrum of a right cone, with a cylinder (bore) removed around the axis; from which it follows that the thickness of metal is greatest at the breech, where it haS to withstand the effect of ignited powder in its most condensed, and therefore most powerful state. Guns are first cast in loam or dry sand, then turned to the required shape, and lastly bored with the minutest accuracy. Formerly, they were cast with the bore already formed; but the direction was rarely exactly correct, and the surface scarcely ever strictly even. Some additional particulars of their manufacture will be
given under GUN-FACTORIES, ROYAL; and the science of artillery will be summarized under GUNNERY.
An article on fire-arms would be incomplete without some allusion to the progress made in small-arms. In the 15th c., the smallest sort of cannon were probably at times mounted and used as hand-guns. From this the step to the arquebus was rapid; that weapon developed as years passed into the clumsy matchlock; that into the firelock and flint musket; then the percussion-musket; and lastly, into the beautiful rifles of our own day, which have culminated in the central-fire breech-loaders. For diminutives, small arquebnses were made to do duty as horse-pistols; genuine pistols succeeded them: these were gradually improved and reduced in size, till they have culminated in the saloon pistol, available for a waistcoat pocket; and the deadly revolver, with its multi plied shooting power. All these weapons are described under their respective heads— ARQUEBUS, MATCHLOCK, MUSKET, PISTOL, REVOLVER, RIFLE.
Many valuable works have been written on fire-arms from the days of Leonardo da Vinci and Tartaglia to the present. Among those consulted for this article have been Etudes sur le Passo et l' Avenir de l' Artillerio of the emperor Napoleon III. ; Our Engines of War, by rapt. Jervis; maj. Straith's Treatise on Artillery; gen. Chesney On Fire arms, etc.