( 156 ) 



^roreover, I took feveral other glafTes, and inclofed in each of 

 them three {grains of Gunpowder, which (the glafles being fnft care- 

 fully clofed) I fet on fire ; but in this experiment fonic of the 

 glalfes flew in pieces, though they were all of the fame lize, and 

 the quantity of Gunpowder the fame in each. The caufe of this I 

 took to be, that in the broken gkifles the grains of Gunpowder 

 might be fired altogether, or blown up more haftily than in the 

 others. The gkilles which remained uninjured, after tlie fpace of 

 twenty-four hours had elapfed, I opened in fuch a manner that the 

 air within them (which in thefe glaifes was more comprefled than 

 the common air we breathe, and more than the glalfcs themfelves 

 originally contained) might empty itfelf into a glafs globe filled 

 with water, having a fmall neck, and placed not upright, but 

 floping, in order that I might obferve accurately the quantity of air 

 which was forced out of the glafs wherein the Gunpowder had been 

 fired into the glafs globe filled with water ; for fo much air as was 

 forced into the slohe, fo much M^ater mufl: be driven out of it. 



To afcertain this, I took feveral glafles, and after having fired 

 the Gunpowder in them, as before related, I weighed them, though 

 to avoid prolixity, I will here only relate the computations I made 

 with one of them. This glafs weighed feventy-feven grains, and 

 w'hen the comprefled air it contained had been made to pafs into the 

 before mentioned glafs globe, I filled the other glafs with water^ 

 and weighing it, 1 found that the water contained in the cavity of 

 the glafs weighed fixty-three grains : with this water I filled up the 

 cavity in the glafs globe, which had been made in it, by introducing 

 the air generated by the explofion of the Gunpowder, and I fomid 

 that fifty-five grains of water had been driven out of the glafs globe, 

 for I had only eight grains of water remaining after filling up the 

 cavity or fpace ; confequently, the firing three grains of gunpowder 

 in the glafs, produced fuch a compreflion of air within it, that when 

 the glafs was opened, nearly feven-eighth parts of the air it tlien 

 contained ruflied out ; fo that the air in the glafs, which before 



