Mortar-Beds

—Mortars are fired from a bed; in the U. S. service there are three kinds of mortar-beds in use in the siege service; the 8-inch, 10-inch, and the Coehorn; the first two differ only in dimensions. They are made of wrought iron and put together after the manner of the sea-coast gun-carriage. The different parts are the cheeks, which, like those of the gun-carriage, are triangular in shape, and two transoms connecting the cheeks together. At the end of each cheek are projections, called front and rear notches, underneath which the cannoneers embar with their handspikes to move the bed on the platform; there are also two front and two rear manœuvring-bolts for the same purpose. The elevation and depre ion are given as in the gun-carriage by embarring with the iron elevating bar through the fulcrum into the ratchets on the breech of the mortar. The Coehorn-bed is made of a block of oak wood, in one piece, or two pieces joined together with bolts. A rece for the trunnions and part of the breech is made in the top of the bed, and the trunnions are kept in their places by plates of iron bolted down over them. Two iron handles are bolted to the bed on each side, by which four men can carry the bed with the mortar in its place, the entire weight being only 296 pounds. Sea-coast mortar-beds are similar to those for siege purposes, but they have eccentric truck-wheels for manœuvring the mortar-bed on the platform and the manœuvring-bolts are omitted. The 13-inch sea-coast mortar is now mounted upon a centre pintle-carriage. The usual bed, now become the top carriage, is placed upon a cha is resting on a platform. The top carriage has a crane attached to the left cheek, and to the inside of the right cheek is attached a pawl worked from the front, for locking the eccentric axle in and out of gear, and the carriage is strengthened by an additional rear transom about 5 inches wide, the pipe being omitted. The cha is has the usual appliance for throwing this cla of carriages into gear, and in addition an eccentric axle placed at right angles to and supported by a double front transom, and carrying a traverse wheel, by means of which motion is communicated to the cha is. The cha is is otherwise transomed and braced in accordance with the system. Heretofore nearly all sea-coast carriages were made of wood, but in consequence of the great difficulty of preserving this material from decay, especially when exposed to the dampne of casemates, they have nearly all been replaced by wrought iron. The carriages principally employed for the transportation of ammunition, implements, and materials for repairs, are cai ons, mortar-wagons, forges, and battery-wagons.