JO

the properties

4. In the decomposition of saltpetre, an elastic fluidis generated, which is permanent for a considerable spaceof time.

CHAP. III.

Of Gbn-powder.

36. GU N-P O WD E R is composed of very light char-coal, sulphur, and well-refined saltpetre. These materials areput into a wooden trough, where they are ground together,to render the contact of the nitrous and combustible particlesintimate and equal throughout the whole mass. The mix-ture is occasionally sprinkled with water, to form an amal-gam, which is afterwards granulated, and prevent the finerparticles of the sulphur and charcoal from flying off, whichwould neceflarily alter the proportion of the composition.The powder-makers employ more or less time in the ope-ration. of grinding, in proportion to the quantity of saltpetre."When they conceive that the ingredients are properly mixedtogether, they form from the paste those little grains which,being dried, obtain the name of gunpowder.

37. There seems to be nothing in the fabric of gun-powder that can alter any of the properties of the constituentparts, taken either individually or collectively. (35.) Thenecessity of having a combustible body capable of producingthe total and instantaneous decomposition of the nitre, makessulphur and charcoal requisite ingredients: sulphur, becauseit easily takes fire, and propagates the inflammation, though[he heat it produces is not sufficient to decompose the nitre:charcoal, because its inflammation, as well as the propa-gation of fire into all its parts, being slower, it acquires, whenft becomes red-hot, a stronger degree of heat than the sulphur,and is therefore more capable of producing the entire decom-position of the nitre. Therefore, from their combinationwith a proper proportion of nitre, the most instantaneousexplosion may be expected; but if the quantity of nitre betoo great, the fire communicating to the combustible par-ticles with so much the more difficulty as the excess is th©greater, may produce no effects.

If to a composition of 14 part*; of saltpetre, 1 of sulphur,and 1 of charcoal, a burning coal be applied, those parts

only