[ *6c ] 



mafs; and, for this purpofe, I divided a quantity of 

 about a gallon into three parts, the firft: confuting of 

 that which was uppermoft, and the laft of that which 

 was the loweft, contiguous to the water j 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 purefl: fixed air that 

 I cau make ; and I once made a very large quantity 

 for the fole purpofe of this experiment. This, there- 

 fore, feems to be one inftance 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 allre*- 

 fpects, common air, I have.been led to conclude, from 

 ieveral attempts which I once made to mix it with 

 air, in which a quantity of iron filings and brim- 

 ftone, made into a parte with water, had ftood; 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 



