The fine powder thus obtained is sometimes merely moistened, so as to form a stiff paste, and passed through rollers, the cake formed, being dried and granulated. The incorporating cylinders are used occasionally, but the more usual plan adopted on the Continent to effect this operation is the stamping-mill, which requires a short description. It is nothing more nor less than the pestle-and-mortar principle, each mill consisting of from six to twelve bronze or wooden mortars bedded in the floor of the building; they are the shape of the frustum of a cone, the mouth being much narrower than the base; the pestles, or stampers as they are called, are made of wood, shod with either very hard wood or bronze, on which project wooden teeth about twelve inches long; a vertical movement is imparted to them by a shaft worked by the water-wheel having similar teeth attached; in its revolution it raises the stamper about eighteen inches, which falls again as the projection is disengaged, twenty five times in a minute. This operation is carried on for twelve hours, during which period the charge (about 15lbs.) is moistened at intervals, and routed up with a copper-shod spud; at the end of this time the cake is taken out, and left to dry and harden; it seldom receives any pressure--although, in some manufactories, presses are being erected. GRANULATING. ~Granulation.~ The cake is then granulated in sets of sieves fitting one into the other, having perforated zinc bottoms of different degrees of fineness, which are suspended from the ceiling of the room by ropes, an ash spring being attached to each box holding the sieves, the cake is put into the uppermost one with some gun-metal balls, and shaken backwards and forwards, which motion the spring facilitates; it is thus broken up into different sized grains, which are separated by passing through the several meshes. The grain formed is then dusted in bags or shaking-frames covered with canvas, and then glazed in barrels. STOVING OR DRYING. ~Drying.~ ~Comparative merits of foreign and English gunpowder.~