218 ESSAYS anp OBSERVATICNS 
quantity : From whence it is evident, that 
the air, which quick-lime attracts, is of a 
different kind from that which is mixed 
with water. And that it is alfo different 
from common elaftic air, is fuficiently 
proved by daily experience; for lime-wa- 
ter, which foon attracts air, and forms a 
eruft when expofed in open and fhallow 
veflels, may be preferved, for any time, 
in bottles which are but flightly corked, 
or clofed in fuch a manner as would allow 
ree accefs to elaftic air, were a vacuum 
formed in the bottle. Quick-lime there- 
fore does not attract air when in its 
moft ordinary form, but is capable of be-. 
ing joined to one particular fpecies only, 
which is difperfed through the atmo- 
fphere, either in the fhape of an exceed- 
ingly fubiile powder, or more probably 
in that of an elaftic fluid. To this I have 
given the name of fixed air, and perhaps 
very improperly ; but I thought it better 
to ufe a word already familiar in philo- 
fophy, than to invent a new name, before 
we be more fully acquainted with the 
nature 
