and the feeming Converjion of Water into Air. 4 1 7 
that time there was in it a confiderable proportion of fixed air, 
which I imagined might either be that which had not been 
fufficiently expelled before, or might be compofed of fame 
phlogiftic matter contained in the lime, and the purer air that 
was yielded by the water : for I own I then concluded, that the 
air which I got (and which, when the fixed air was extracted 
from it, was luch as a candle would juft burn in) came from 
the water, efpecially as in fome of the proceffes, the weight of 
the air I caught was very nearly, if not quite equal to that of 
the water, and interpofing a large glafs balloon between the 
retort and the recipient for the air, I obferved that it remained 
perfectly cool and dry during the whole procefs ; and feveral 
hours afterwards there was not the lead; moifture condenfed in 
it. I alfo received a quantity of another produce of air made 
in this manner in mercury, and having viewed it with the 
greateft attention, obferved that, after feveral days, it never 
depofited the leaft moifture. 
I then calcined a quantity of natural lime-ftone with this 
glafs balloon, interpofed in the fame manner, and found no 
"water, but only air to come from it, though the ftone is gene- 
rally fuppofed to contain water. But when I ufed much more 
than half an ounce of water to the quantity of whiting or 
lime above-mentioned, I always had fome w^ater come over, 
though very little in proportion to the quantity made ule of. 
I did not fail to examine whether there had been any lols in 
the weight of the lime, or whiting, in order to determine 
whether any part of thefe folid fubftances had entered into the 
compofition of the air ; but I found much difficulty in weighing 
them with exa£hiefs, after fhaking them out of an earthen re- 
tort, into which I could not fee, and to which part of thefe 
earthy matters often adhered, fo that I could not obtain much 
fatisfa&ion even when I broke the retort. Betides, there was 
