GUNPOWDER. The date of invention of this explosive composition is involved in ob scurity. It has been said that it was used in China as early as the year A. D. 85, and that the knowledge of it was conveyed to us from the Arabs on the return of the Crusaders to Europe ; that the Arabs made use of it at the siege of Mecca in 690 ; and that they derived it from the Indians. Roger Bacon has been supposed to allude, in an enigmatic way, to the composition of explosive force of gun powder ; and about 1336 Berthold Schwartz, a monk, is said to have also discovered the mode of manufacturing it.
Whatever may have been the history of its origin, gunpowder at the present day consists of a very intimate mixture of nitre, or nitrate of potash, charcoal, and sulphur. The pro portions vary; but they generally consist of about 6 parts of nitre to 1 of charcoal and 1 of sulphur. According to a comparative table which has been published, gunpowder for sporting contains the largest ratio of nitre, gunpowder for blasting the largest ratio of sulphur, and the Austrian gunpowder the largest ratio of charcoal ; but the range of difference is only small—chiefly observable in the sulphur. The ingredients must be of the greatest attainable purity ; and the nitre is fused before use. The charcoal, either of alder, willow, or dog-wood, is prepared in iron retorts ; and the sulphur is the volcanic kind imported from Sicily, and is refined by melting or subliming.
When the ingredients are prepared, they are separately ground to a fine powder, and mixed in the proper proportions. The com position is sent to the gunpowder mill, which consists of two stones vertically placed, and running on a bed-stone. On this bed-stone the composition is spread, wetted, and ground, and is then taken off and taken to the corning house to be corned or grained ; here it is first pressed into a hard and firm body, broken into small lumps, and the powder grained by these lumps being put into sieves in each of which is a flat circular piece of lignum The sieves are made of parchment skins, having round holes punched through them ; several of these sieves are fixed in a frame, which by machinery has such a motion given to it as to make the runner in each sieve go round with velocity sufficient to break the lumps of powder, and force them through the sieves, forming grains of several sizes. The
grains are separated from the dust by proper sieves and reels ; they are then hardened, and the rougher edges taken off by being run a sufficient length of time in a close reel, which has a proper circular motion given to it.
The gunpowder, thus corned, dusted, and reeled, is sent to the stove and dried, care being taken not to raise the heat so as to dis sipate the sulphur. The heat is regulated by a thermometer.
The theory of the action of gunpowder is this: that particle on which a spark falls is immediately heated to the temperature of ig nition ; the nitre is decomposed, and its oxygen combines with the charcoal and sulphur, which are also heated ; this combination extricates as much heat as is sufficient to inflame suc cessively, though rapidly, the remaining mass. The cause of the expansive force of gunpowder is the production of carbonic acid, carbonic oxide, and nitrogen; and, these being liberated at a very high temperature, the effect is greatly increased. The firing may be effected by the