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As the iron is reduced to a calx by this procefs, 
I once concluded, that it is phlogifton that fixed air 
wants, to make it common air; and, for any thing 
I yet know, this may be the cafe, though I am ig- 
norant of the method of combining them ; and when 
I calcined a quantity of lead in fixed air, in the man- 
ner which will be defcribed hereafter, it did not feetn 
to have been lefs foluble in water than it was before. 
ir. 
On Air in which a candle, or erimstone* 
HAS BURNED OUT. 
It is well known that flame cannot fubfitl long 
without change of air, fo that the common air is 
neceflary to it, except in the cafe of fubllances, into 
the compofition of which nitre enters ; for thele will 
burn in vacuo, in fixed air, and even under water, 
as is evident in fome rockets, which are made for 
' this purpofe. The quantity of air which even a 
fmall flame requires to keep it burning is prodi- 
gious. It is generally faid, that an ordinary candle 
confumes, as it is called, about a gallon in a 
minute. Confidering this amazing confumption 
of air, by fires of all kinds, volcano’s, &c. it be- 
comes a great objedt of philofophical inquiry, to as- 
certain what change is made in the conftitution of 
the air by flame, and to difcover what provifion there 
is in nature for remedying the injury which the at- 
mofphere receives by this means. Some of the fol- 
lowing experiments will, perhaps, be thought to 
throw a little light upon the fubjedh 
' The, 
