12

THE PROPERTIES

proportion, and with grains of the fame size, as the fine warpowder, but with a less dense charcoal, is used by sportsmenin shooting game. When composed of 7 parts of saltpetre,1 of charcoal, and 1 of sulphur, and granulated as the finewar powder, it is called fire-work , or rejoicing powder.

41. We will now proceed to prove, that fired powderpreserves constantly the properties remarked in the combi-nation of its ingredients; (35.) modified, nevertheless, bythe exactness of the mixture, the size of the grains, andother circumstances that will be pointed out.

42. All degrees of heat are not sufficient to fire powderfor if it be only sufficient to inflame sulphur, the effects beforementioned (28, 35. N° 1.) will result, as may be provedby throwing several grains of powder near hot coals. Theburning of the grains contiguous to the coals will be so in-stantaneous, as not to be distinguishable from the inflam-mation of the sulphur; but the grains at a little distancefrom the coals will emit, after some time, a small, blue,lambent flame, which at length becomes brighter; the iri-sen sen ess of the fire increases, and the gradual destructionof the saltpetre is clearly discernible; some of the grainsare consumed, while in oth'-rs the blue flame disappearswithout producing their destruction : at length the moredistant grains become warm, without emitting any flame,or being consumed. This may be exemplified by putting'some large grains of powder on an iron plate, which maybe put near to, or drawn back from the fire, in order togive it different degrees of heat; or by directing upon themthe solar rays, united by means of a convex glass, as dif-ferent degrees of heat may be produced by augmenting ordiminishing the circle formed by the re-union of the rays.

43. These experiments prove that powder, like othercombustible bodies, may become hot or inflamed, withoutbeing in the fame instant consumed. It is necessary, there-fore, to distinguish between the inflammation and the finaldestruction of each grain: for sire, when applied to twograins of different sizes, does not always cause any sensibledifference in their destruction; yet there is a great differencein the force of two equal quantities of powder, made withthe fame proportion of ingredients, of the fame quality,but differently granulated, as is seen on comparing can-non and musquet powder.

44. The