The sizes of howitzers and mortars are expressed by the diameter of the shell they are intended to throw; the largest of which at present in general use is the “thirteen-inch.” This immense shell when charged weighs nearly 200 pounds. These shells or “bombs” as they were formerly called, are cast hollow (fig. 7), with a small opening into which a “fuze” or wooden tube filled with combustible matter is inserted; they are charged with gunpowder, which on being ignited by the fuze burning down to it, explodes and bursts the shell into fragments, which fly about with terrible force. What are called “shrapnel-shells,” are those shells which are filled with both gunpowder and leaden bullets, to be scattered about by the explosion. Case-shot is a name given to a packet of bullets inclosed in a tin canister and used as a projectile, the case bursts and the bullets are scattered. Grape-shot is the name given to a collection of nine iron balls packed up so as to be used as one. Hand-grenades are small shells of about three pounds’ weight, to be cast by hand. Bullets for the ordinary musket are simple balls of lead, in some cases cast six at a time in moulds (fig. 8), and coming out in one piece as seen at fig. 9, which are afterwards separated and finished off by a sort of nippers as seen in fig. 10; but for the most part musket and rifle bullets are formed by compression. The bullets for the Minié rifle are made by machinery; they are of a conical form, with a hollow at the base into which a small plug of box wood is fitted, this end being towards the powder receives the whole force of the explosion, the effect of which is to drive in the plug and open out the bullet, thus fitting it tightly into the grooves of the rifle and preventing any loss of power by the escape of the gases resulting from the combustion of the powder. The machine for making these bullets is shown at fig. 11. The following is an account of it, taken from the “Times”:--