OF GUN-POWDER

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14. Wherefore, the force of gun-powder fired in tnus-quets, cannon, mortars, mines, &c. being in proportion toits inflammation, its effects must inevitably be modified bythe quantity and the proportion of the ingredients, the tem-perature of the atmosphere, and other circumstances that willbe hereafter pointed out. And fince it is not in our powerto determine every point that affects its inflammation andtotal consumption, we cannot be always certain of producingthe fame effects with the fame quantity of powder fired fromthe fame piece of ordnance.

CHAP. II,

Of Sulphur, Saltpetre, and Charcoal.

15. SuLPHUR is a substance composed of vitriolicacid and a combustible matter. It is ranked in the class ofminerals, because it is extracted from the bowels of theearth. When exposed to a moderate degree of heat, itliquefies, and sublimes in little tufts called flowers of sul-phur: thus it is purified from heterogeneous substances bysublimation.

16. The property of sulphur is to take fire, inflame, andbe entirely consumed, when exposed in the open air to astronger fire than that which will liquefy it. It is made useof in the composition of gun-powder, because the ignitedmotion is easily propagated in it.

17. The facility with which sulphur takes fire and burnsdepends on the rarefaction of the surrounding air. Toburn it in an exhausted receiver, it requires a continued ap-plication of a much greater degree of heat than wouldinflame it in the open air: the receiver should also be of asize proportioned to the quantity of sulphur, lest the con-densation of the smoke prevent its total consumption, si2.)The only method of decomposing sulphur is by burning;which destroys the combustible matter, and the vitriolic acidexhales in vapour.

18. Charcoal, used in the composition of gun-powder, isdefined to be a body composed of a combustible mattery and

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