C i6 4 ] 
quantity of lime-water, will aflfeft it in fuch a man- 
ner, that breathing into it will not make it turbid, 
which otherwife it always prefently does. 
Dr. Hales fuppofed, that by burning brimftone 
repeatedly in the fame quantity of air, the diminu- 
tion would continue without end. But this I have 
frequently tried, and not found to be the cafe. In- 
deed, when the ignition has been imperfect in the 
firft inftance, a fecond firing of the fame fubftance 
will increafe the efredt of the firft, &c. but this pro- 
grefs foon ceafes. In many cafes of the diminution 
of air, the effect is not immediately apparent, even 
when it ftands in water; for fometimes the bulk of 
air will not be much reduced, tiil it has pafted fe- 
veral times through a quantity of water, which has 
thereby a better opportunity of abforbing that fluid 
part of the air, which had not been perfectly de- 
tached from the reft. I have fometimes found a 
very great redudlion of a mafs of air, in confequence 
of palling but once thorough cold water. If the air 
has flood in quickfllver, the diminution is generally 
inconfiderable, till it has undergone this operation, 
there not being any fubftance expofed to the air that 
could abforb any part of it. 
I could not find any confiderable alteration in the 
fpecific gravity of the air, in which candles, or brim- 
ftone, had burned out. I am fatisfied, however, 
that it is not heavier than common air, which muft 
have been manifeft, if fo great a diminution of the 
quantity had been owing, as Dr. Hales and others 
fuppofed, to the elafticity of the whole mafs being 
impaired. After making feveral trials for this pur- 
pose, I, concluded that air, thus diminifhed in bulk* 
