( 153 ) 



multiplied by l6o, the produd is 2080, and fo many times more 

 fpace does a grain of Gunpowder occupy when fixed, than what it 

 did before, 



Tliis is then the magnitude or quantity in fpace of the expanfion 

 or explofion of Gunpowder, computed by me with all the accuracy 

 I was able, though by no means to be deemed perfecit, becaufe one 

 grain of Gunpowder will explode much more completely than ano- 

 ther, by reafon that the mixture of faltpctre, fulphur, and charcoal, 

 is not in their proportions alike in all, as a proof of which, I have 

 oblerved in firing a grain of Gunpowder, that part of it hiis been 

 confumed before the reft blew up. 



But one circumftance in thele my obfervations appeared moft 

 worthy -of note, namely, that with the fame velocity as the air 

 ruflied out of the glafs wherein the grain of Gunpowder was fired 

 into the glafs globe, with equal velocity was the water forced out 

 of the glafs globe, through the narrow opening of the glafs where 

 the Gunpowder had been fired, infomuch as almoft haU' to fill that 

 glafs with water ; the caufe of which, I conceived, could be no 

 other than this ; the fire produced by the kindling of the Gun- 

 powder inclofed within the glafs, requires great extenfion, whereby 

 the air in the glafs muft in part be driven out, and whereas with 

 the fame rapidity as the fire was kindled, it will efcape through the 

 pores of the glafs into the air, fo upon the fire's quitting the cavity 

 of the glafs, fome other fubftance nmft follow in its place to occupy 

 the vacuum, whereupon this vacancy in the glafs muft be filled with 

 water, becaufe the opening in the glafs is immerged under thq 

 water. 



From this regurgitation or ruftiing of the \a ater into the glafs, 

 when the Gunpowder was fired, after the fire had efcaped from 

 thence, I was led to refleA on the firing of Gunpowder in a Can- 

 non or great Gun, and I concluded that a ball fired from an over- 

 long great Gun would not have fo much force, nor be driven to fo 

 great a diftance as if the Gun was of a more moderate length, for 



