1 1 4 Analyjis of the Air . 



Now a cubick inch of Mercury weighing 

 3580 grains, thirty cubick inches (which is 

 equal to the weight of our atmofphere on 

 an area of a cubick inch) will weigh fifteen 

 pounds, five ounces, 215 grains 3 and forty- 

 eight of them will weigh above 836 pounds; 

 which is therefore equal to the force with 

 which an inch fquare of the furface of the 

 Apple would comprefs the air, fuppofing 

 there were no other fubflance but air in the 

 Apple : And if we take the furface of an 

 Apple at iixteen fquare inches, then the 

 whole force with;\vjhich that furface would 

 comprefs the included air, would be 13383 

 pounds. And fince action and reaction 

 are equal, this would be the force, with 

 which the air in the Apple would endea- 

 vour to expand itfelf, if it were there in 

 an elaftick and ftrongly compreffed ftate : 

 But fo great an expanfivc force in an Apple 

 would certainly rend the fubflance of it with 

 a ftrong explolion, efpecially when that force 

 was increafed by the vigorous influence of 

 the Sun's warmth. 



We may make a like eftimate alfo, from 

 the great quantities of air which arofe either 

 by fermentation, or the force of fire from 

 ieveral orher bodies* Thus in Exp. 55. there 



arofe 



