MORTARS.
Mortars differ from Guns in the construction of their bore, and also in their form, which is considerably shorter, the metal being much thicker, and the trunnions being at the extremity of the breech.
They are used for throwing Shells into a town, or battery, setting fire to and overthrowing works, blowing up magazines, and breaking through the roofs of barracks, casemates, magazines, &c. They are distinguished from each other by the diameter of their bore. Their chambers are in the form of a frustrum of a cone, in which the powder is more concentrated; the Shell fits close to the sides of the piece, and thereby receives the whole force of the expansion of the powder. The greatest charges their chambers will contain, and the corresponding Ranges, are as follows:—
| 13-inch. | 10-inch. | 18-inch. | |
| Land Service. | Land Service. | Land Service. | |
| Greatest charge | 9 pounds. | 4 pounds. | 2 pounds. |
| Greatest range | 2706 yards. | 2536 yards. | 1726 yards. |
When Mortars are used in firing on Inclined planes, up or down hill, should the inclination be considerable, take half the angle it makes with the horizon, and add it to, or subtract it from 45 degrees (which is for a medium plane), and it will give the greatest range upon the required plane.
Note.—Vide Tables of Dimensions, Weight, Charges, Ranges, &c.
VALUE OF ORDNANCE.
BRASS ORDNANCE.
Dependent on the market price of metals; at £100 per ton, after their combination, the value of gun metal is from 4 pence to 4½ pence per lb.
IRON ORDNANCE.