400 Dr. ingenhousz’s Account of a 
mafs of the charge being employed in one and the fame 
explofion. This comparifon is very inadequate ; for in 
the cafe of a wind gun the air comprefled to ~ is ready 
to exert all the force of elafticity exifting in the whole 
mafs, and may therefore be compared to a ftrong fpring 
forcibly bent. But the inflammable air is far from 
exerting the force of expanfion and elafticity through its 
whole mafs at the fame inftant : for the inflammation is 
propagated through it fucceflively, beginning where the 
electrical fpark kindles it, and reaching gradually farther 
till the whole is confumed. Now as I have demonftrated, 
that inflammable air is reduced to more than half its 
bulk by inflammation, it mult follow, that that portion 
of it which is confumed the firft by the inflammation, 
leaving more room by its diminution, diminifhes in pro- 
portion the propelling powers of what remains ftill to be 
inflamed. 
The very great difference between the explofive force 
of the two compounds is illuftrated by what happens 
after their inflammation. The compound of inflammable 
with common or dephlogifticated air, is very much re- 
duced in bulk after inflammation. I found this by the 
following experiment: I fired a brafs inflammable air 
piftol (made by Mr. nairne according to my directions) 
which had apifton in the cylinder, by which a proper 
quantity 
