VOL. XVII.] PHILOSOPHICAL TRANSACTIONS. 33g 



monds. Some of the saltpetre particles, which lay mixed with the others, 

 were long and slender, and looked like little bundles of arrows. 



I repeated the experiments with the powder, and immediately after its blow- 

 ing up, I viewed the glass with a microscope, and could then discern the very 

 sudden change or shooting of t+ie globular particles of the nitre into sexangular 

 salts, and that all at once. The number of these nitrous particles, afforded by 

 one corn of powder, is inconceivably great, besides those of the sulphur and 

 coal. These were best seen when I fired but one corn ; for when there were 

 more fired, the greater quantity of nitre blew up so much of the sulphur and 

 coal, that the change and shooting of the salts could not be so well seen. If I 

 fired the powder with heat from below, the coal and sulphur would be blown 

 up ; but if with heat from above, but few particles of the coal, and yet fewer 

 of the sulphur, would be forced up. 



Next I fired one, two, and three corns of powder in several closed glasses, 

 and suffering them to cool, I opened them, some after 4 or 5 days, and found 

 always compressed air therein, which flew forcibly out. That I might know the 

 quantity of this generated air, I opened some of them after such a manner, 

 that the contained air issued into a bolt-head with a narrow neck, which was 

 filled with water, which, as the air rushed in, was forced out ; by which expe- 

 riment I found the air compressed 8 times more than it was before ; or, which 

 is the same thing, when at liberty took up 8 times the room it did before. 



I next put one corn of powder in a glass, and closing it up with a very small 

 hole only at the narrow end, which end 1 placed under the water in the glass 

 vessel as before, and firing the powder, as much air was thereby generated, 

 as forced out l60 grains of water. Now 13 corns of powder weigh but 

 one grain ; wherefore multiplying l6o by 13 which makes 2080, we find that 

 gunpowder fired expands itself 2080 times, or takes up so many times the space 

 it did before.* 



I observed likewise that the glass wherein the powder was fired would be 

 always filled half full of water immediately after the explosion ; the reason of 

 which I conceived to be the great rarefaction of the air, by the heat of the fire 

 and stroke of the powder, which upon cooling takes up less space, and the water 

 enters in to fill up the rest to prevent a vacuity. 



From this last observation, I concluded that a bullet cannot be shot with so 

 great a force out of a very long cannon, or other gun, as out of one something 



* There leems to be some inaccuracy in this experiment, as to the quantity or numbers, as will 

 appear hereafter by the more accurate experiments of Mr. Hauksbee and Mr. Robins. A great part 

 •f the above expansion is to be ascribed to the heat of the inflamed powder. 



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