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.
In summer the process of drying is often performed in the sun, and in winter by the steam stove, in the following way. The powder is spread about three or four inches thick on a large canvas tray, under which is an arrangement of pipes, which convey the hot air forced by a fan through a cylinder heated by steam: it is considered to be sufficiently dried in from three to four hours, during which time it is occasionally raked about. In some manufactories it undergoes a further operation of being dusted, and is then barrelled up for use. Generally the great failure in the foreign manufacture is the neglect of the principal stage of the fabrication, viz. incorporation; with the old stamping-mill, it is quite impossible that the process can be carried out to the necessary extent. Comparative merits of foreign and English gunpowder.The Continental powder is usually very soft in its grain, dusty, and quickly absorbs moisture from the atmosphere; its density is below the English powder, on account of its never being subjected to pressure; consequently it is not so durable, and forms a good deal of dust in transport; a great amount of residue is generally left in the gun, and its strength, as a propelling agent, is far inferior to our powders. On being flashed on a glass plate, instead of producing a sudden concussion, like the sharp rap of a hammer, it burns more like composition, throwing off a quantity of sparks.
NEW RIFLE POWDER.
The following mode of manufacturing rifle powder, appeared in Garrison Orders at Woolwich, 31st December, 1859:
Composition in 100 parts:—