and Detonating Matches. 133 



for the water present. But charcoal which has remained long 

 impregnated with moisture, affords a most detrimental con- 

 stituent to gunpowder. 



4. On Mixing the Constituents and forming the Powder. 



The three ingredients being thus prepared are ready for 

 manufacturing into gunpowder. They are, i. Separately 

 ground to a fine powder, which is passed through proper silk 

 sieves or bolting machines ; ii. They are mixed together in 

 the proper proportions, which we shall afterwards discuss; 

 iii. The composition is then sent to the gunpowder mill, which 

 consists of two edge-stones of a calcareous kind, turning by 

 means of a horizontal shaft, on a bed-stone of the same nature ; 

 incapable of affording sparks by collision with steel, as sand- 

 stones would do. On this bed-stone, the composition is 

 spread, and moistened with as small a quantity of water as 

 will, in conjunction with the weight of the revolving stones, 

 bring it into a proper body of cake, but by no means to a pasty 

 state. The line of contact of the rolling edge- stone is con- 

 stantly preceded by a hard copper scraper, which goes round 

 with the wheel, regularly collecting the caking-mass, and 

 bringing it into the track of the stone. From fifty to sixty 

 pounds of cake are usually worked at one operation, under 

 each millstone. When the mass has thus been thoroughly 

 kneaded and incorporated, it is sent to the corning-house, 

 where a separate mill is employed to form the cake into grains 

 or corns. Here it is first pressed into a hard firm mass, then 

 broken into small lumps ;, after which the corning process is 

 performed, by placing these lumps in sieves, on each of which 

 is laid a disc or flat cake of lignum vital. The sieves are made 

 of parchment skins, perforated with a multitude of round 

 holes. Several such sieves are fixed in a frame, which, by 

 proper machinery, has such a motion given to it, as to make 

 the lignum vitce runner in each sieve move about with con- 

 siderable velocity, so as to break down the lumps of the cake, 

 and force its substance through the holes^ in grains of certain 

 sizes. These granular particles are afterwards separated from 

 the finer dust by proper sieves and reels. 



The corned powder must now be hardened, and its rougher 



