[ 174 ] 
Air is not lefs neceflary for the fupport of fire 
than of animal life, for fire will not long conti- 
nue to burn without a circulation of frefh air, which 
I fuppofe happens not from its adding any thing to 
the pabulum of fire (for that feems unneceflary) 
but rather on this account.- The air immediately 
about a body on fire, is heated and made fpecifically 
lighter than the air at fome diftance from it. This 
hot air muff, therefore, afcend and carry with it all 
thofe minute particles of different kinds, which are 
thrown off from the burning body, and which other- 
wife would reft upon its furface, and thereby clog 
and flop the fubtile vibrations of the burning matter, 
in which the nature of fire partly confifts. If, 
therefore, fire be confined in a clofe place, where 
there can be no circulation of frefli air, the air about 
it being foon faturated, with the particles arifing from 
the burning matter, will not be able to take up any 
more of them, and, therefore, the fire muft go out 
fmothered as it were in its own allies. And hence 
it is, that fire burns fafter when air is ftrongly blown 
upon it ; for this air carries off the aflies as faft as 
they are formed on the furface of the burning bo- 
dy, and thereby keeps thofe particles that have juft 
taken fire quite free from any thing that can impede 
or clog their vibratory motion. This air will alfo 
fpread the fire quickly through the fuel, by blowing 
the particles. that are already kindled amongft them 
that are notj and, perhaps, the motion of the air 
may promote thefe fubtile vibrations in the burning 
matter, by which the fire is propagated through its 
parts. 
Though 
