THE PROPERTIES

22

rating the smoke from the elastic fluid, to determine the ab-solute force of each; yet it may be safely inferred, that thegreater part of it depends upon the permanent fluid.

60. The common air that is within and between thegrains contributes likewise, by its expansion, to the force ofthe powder when fired. Its absolute force might be easilydetermined ; but is very small, in comparison of the elas-ticity of the permanent fluid generated from powder.

fir. Thus, the diminution of the ranges of fire-arms, whenheated by frequent discharges, or when the air of the atmos-phete is more rarefied, ought not to be attributed to lesseia iicity in the air, but rather to the second property ofpowder; where, being fired in a rarer medium, less takesfire though the fame quantity be used ; and hence the rangeis shortened, as will hereafter be more clearly proved.

62. For the fame reason, the increase of force obtainedby triturating powder for a long time, and the force whichdamaged powder resumes after having undergone a frelhprocess, proceed not, as some think, from the greater quan-tity of air compressed into the substance of the powder, butsimply from a more exact mixture of the ingredients, whencethey more easily and generally take fire.

63. In illustration of this remark, it is sufficient to ob-serve, that the best manufactured powder is liable to be da-maged by excessive heat or moisture. The powder-makers,in drying powder, take care to stir it frequently, and suffer itto cool before they put it into the barrels; as they pretendthat it ferments when very hot: and in fact, if, when muchheated, it be closed up in a barrel for some hours, and after-wards poured gently upon a cloth, a great part of the grains,especially those towards the middle of the barrel, will becaked together; on examining them carefully, it will befound to be owing to the great heat, which having liquefiedthe sulphur, it glues the grains together when cold : but thisnever happens if the powder be allowed to cool before it isput into the barrel. A partial or total liquefaction of thesulphur is always prejudicial to the inflammation and quickdestruction of the powder, (27, 28.) as it destroys the exactmixture of the ingredients, which can be only recovered bysubjecting it to a fresh process. If the heat be not sufficientto liquefy the sulphur, a large quantity os dust, consistingprincipally of sulphur and charcoal, will be sound in barrelsof powder that have been long manufactured and exposed todamp. The powder from which, this dust is detached will

be