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 firing the Gunpowder in it was of the fame denfity with common 

 air, did, upon the tiring, become fo condenfed or compreHed as to 

 require, for attaining the natural Hate or Hberty, an extenfion of 

 fpace in the fame proportion. 



With thefe obfervations I was not yet contented, and, among 

 other experiments, I took a glafs, into which I put a common fized 

 grain of Gunpowder, leaving at the extremity oftheglals an open- 

 ing the lize of a common pin ; this opening, which was at a thin 

 and pointed end of the glafs, I immerfed in the before mentioned 

 glafs globe filled with water, and upon firing this fingle grain of 

 Gunpowder in the glafs, fo great a quantity of air was driven into 

 the glafs globe, that to replace the water which was thereby ex- 

 pelled, I had need of one hundred and fixty grains of water, over 

 and above the water which had found its Way out of the globe into 

 the glafs vefiel wherein the Gunpowder was fired. This laft men- 

 tioned glafs vefiel (which with one more were the only two of fe- 

 veral ufed by me, had remained entire ; for many of the glalies 

 upon the rufhing in of the water, buril in pieces), I weighed be- 

 fore I fired the grain of Gunpowder, in order, after the firing, to 

 know the fize of the cavity it contained, and found that the water 

 in it weighed one hundred and fifty grains.. 



And now, to make a calculation with as much accuracy as poffible, 

 we muft lay out of the cafe, the fize of the cavity of the glafs 

 wherein the Gunpowder was fired, and fay only this, a common 

 fized grain of Gunpowder, in its explofion, forces fo much air into a 

 glafs globe, as fills a fpace equal to that occupied, by one hundred 

 and fixty grains in weight of water ; and to make a comparifon 

 (though it will be a very uncertain one) between the fize of a grain 

 of Gunpowder and the quantity of air it produces on being fired, 

 we will fay, that water and Gunpowder are of equal weight, though 

 this i« not fo in fadl, for Gunpowder finks in water, and therefore 

 is heavier. Now let thirteen grains of Gunpowder be confidered 

 to make the weight of a grain, thefe thirteen grains of Gunpowder 



