C 160 3 
mat's; and, for this purpofe, I divided a quantity of 
about a gallon into three parts, the firft confiding of 
that which was uppcrmod, and the lad of that which 
was the lowed, contiguous to the water ; but all 
thefe parts were reduced in about an equal propor- 
tion, by palling through the water, fo that the whole 
mafs had been of an uniform compofition. This I 
have alfo found to be the cafe with feveral kinds of 
air, which will not properly incorporate. 
A moufe will live very well, though a candle will 
not burn, in the refiduum of the pured fixed air that 
I can make? and I once made a very large quantity 
for the foie purpofe of this experiment. This, there- 
fore, feems to be one indance of the generation of 
genuine common air, though vitiated in fome de- 
gree. It is alfo another proof of the refiduum of 
fixed air being, in part at lead, common air, that it 
becomes turbid, and is diminifhed by the mixture of 
nitrous air, as will be explained hereafter. 
That fixed air only wants fome addition to make it 
permanent, and immifcible with water, if not, in all re- 
fpedts, common air, I have been led to conclude, from 
leveral attempts which I once made to mix it with 
air, in which a quantity of iron filings and brim- 
done, made into a pade with water, had dood ; for, 
in feveral mixtures of this kind, I imagined that not 
much more than half of the fixed air could be im- 
bibed by water; but, not being able to repeat the 
experiment, I conclude that I either deceived myfelf 
in it, or that I overlooked fome circumftance on 
which the fuccefs of it depended. 
Thefe experiments, however, whether they were 
fallacious or otherwife, induced me to try whether 
any 
