f *6r ] 
with water or fome other fubftance proper to abforb 
it, and that its nature is not altered by keeping. 
Experiment III. 
In order to find how much fixed air water would 
abforb, the following experiment, was made. A cylin- 
drical glafs, with divifions marked on its fides with 
a diamond, (hewing the quantity of water which it 
required to fill it up to thofe marks, was filled with 
quickfilver, and inverted into a glafs filled with the 
fame fluid. Some fixed air was then forced into this 
cylindrical glafs, in the fame manner that it was into 
the inverted bottles of water, in the former experi- 
ments ; except that, to prevent any common air from 
being forced into the glafs along with the fixed, I 
took care not to introduce the end of the bent tube 
within the cylindrical glafs, till I was well aflured that 
no common air to fignify could remain within the 
bottle. This was done by firfl; introducing the end of 
the bent tube within an inverted bottle of water, and 
letting it remain there, till the air driven into this 
bottle was at lead io times as much as would fill the 
empty fpace in the bent tube, and the bottle containing 
the marble and acid. By this means one might be 
well aflured, that the quantity of common air re- 
maining within the bent tube and bottle muft be 
very trifling. The end of the bent tube was then 
introduced within the cylindrical glafs, and kept there 
till a fufficient quantity of fixed air was let up. After 
letting' it fland .a few hours, the divifion anfwering to 
the furfaoe of the quickfilver in the cylinder was ob- 
ferved and wrote down, bv which it was known how 
much fixed air had been let up. A little rain water 
Vol. LVI. V was 
