1 1 4 Analyfts of the Air. 
Now a cubick inch of Mercury weigh* 
ing 3 5 8o grains, thirty cubick inches (which 
is equal to the weight of our atmofphere on 
an area of a cubick inch) will weigh 15- 
pounds, 5 ounces, 215 grains 5 and 48 of 
them will weigh above 73 6 pounds ; which 
is therefore equal to the force with which an 
inch Iquare of the furface of the Apple 
would comprefs the air, fuppofing there 
were no other fubftance but air in the Ap- 
ple : And if we take the furface of an Ap- 
ple at 1 6 fquare inches, then the whole 
force with which that furface would com- 
prefs the included air, would be 11776 
pounds. And fince adion and re-adion 
are equal, this would be the force, with 
which the air in the Apple would endeavour 
to expand itfelf, if it were there in an elaftick 
and ftrongly comprefled ftate : But fo great 
an expanfive force in an Apple would cer- 
tainly rend the fubftance of it with a ftrong 
cxplofion, 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 ei- 
ther by fermentation, or the force of fire 
from feveral other bodies. Thus in Exp. 5 5 . 
there 
