MORTAR, a piece of artillery which differs from a cannon in the large diameter of its bore in proportion to its length, and in the circumstance that it is usually fired at a con siderable angle, so that the projectile may strike the object aimed at in a direction nu-re or less vertical. The object for which mortars are intended is the discharge of live shells (q.v.) or carcasses. As the projectile has a large diameter, and, except in rare instances, a very great range is unnecessary, a comparatively small charge of powder is re,i uisite. To give this its utmost power and concentration, it is confined in a hemispheri cal chamber at the lower end of the bore, hut of less diameter. The shell completely closes this chamber; and when the explosion ensues receives its full force on its,center. In the British service the ordinary mortars range in diameter of bore from 5 to 13 inches.
Larger mortars have, however, been tried at times, as at the siege of Antwerp citadel in 1832, when the French• brought one of 24 inches bore to the attack. This monster, owing to its unsvieldiness and other causes, was a failure. Larger still than this, though perhaps more manageable, is Mr. Mallet's 36-inch mortar, construosed in 1855, of iron parts welded together, now at Woolwich, rather as a curiosity than for use. As loaded shells are of immense weight, so heavy, indeed, as in larger calibers to involve the apparatus to deposit them in their places, and the mortar is fired at high elevations, the recoil is so great and so nearly vertical that no carriage could withstand the shock; it is necessary, therefore, that the mortar should be mounted on a solid iron or timber bed, by the trunnions, which are placed behind the breech, and supported in front by massive blocks of wood. This arrangement renders the apparatus so heavy that mortars of large
size are rarely used in field operations, their ordinary positions being in defensive or siege works, and in mortar-vessels.
More wieldy, however, are the Coehorn mortars, invented by the Dutch engineer of that name, for clearing the covert-way or ditch of a fortress. This mortar is sufficiently small to be managed by one man, and is accounted useful in siege or defense operations. The French use a similar Lilliputian ordnance under the denomination of pierriers, stone-throwers. Small mortars are likewise constructed for mountain warfare; a mulo carries the mortar, another the bed, and a third is laden with the projectiles. The use of mortars is diminishing at the present time, elongated shells of great weight being 11 ow thrown from rifled cannon.