OF GUN-POWDER*

ncl are bronzed by the flame of the powder. As the pow-der first takes fire in R, that which is placed above in Pcannot fall upon the plate without passing across the flame ofthe burning powder in R; so that, in this experiment, thefire being inclosed in a smaller space, is more active thanin the former one ; (44.) yet ail the powder is notsired, because the air, on the bladder’s bursting, is toorarefied.

46. But to destroy all doubt of this property of gun-powder,let the funnel be charged as before, the capital N O screwedon to B B, and a wad put at the aperture O to retain thepowder: then, if the bladder be tied fast in q q, and the re-ceiver be exhausted, the quantity of sired powder will alwaysbe greater in proportion as the hole O is narrower ; and if itbe nearly of the fame size as the hole I of the little canalA H I, all the powder in D P will be consumed. In thepreceding experiment, (45.) it was found, that when theair had been entirely exhausted from the receiver, only ~ or^ of the powder took fire, and that a great part of the flamespread itself into the receiver when the bladder burst; whilethat the remaining part expanded itself in D P, which itbronzed. On the contrary, in this experiment, where theaperture O O is narrower than I) D, as neither the air con-tained between the grains, nor the flame, is able to passwith the fame facility into the receiver, they remain in muchgreater quantity in DP; the fire is therefore more intense,and consequently a greater quantity of powder is consumed ;indeed all the powder will be fired when O O is reduced tothe size of I. The fame effects take place with all kinds ofpowder, (40.) the only difference being in the quantity thatremains unfired.

47. It is then ascertained (44, 45,46.) that, in order tofire powder, the heat should be in proportion to the rare-faction of the surrounding air, and that it is increased bypreventing the expansion of the flame. It remains now tobe proved, that the degree of heat must be likewise greater inproportion to the density of the smoke.

It has fallen within the observation of every artillerist,that when shells sink into stiff earth with the fuses down-ward, the smoke finding no passage, the fire is extinguished,and the shell does not burst; but if they fall into water, thesmoke mixing with the water, the site continues till the pow-der in the shell explodes. Fuses are generally filled with a

mixture