C 2 °5 ] 
perfectly agreeable to the analogy of Dr. Mac r 
bride’s difcoveries, and may naturally be expeCted 
from them, that it fhould have fuch an effeCt. 
By a mixture of fixed air I have made whole* 
fome the refiduum of air generated by putrefac- 
tion only, from mice plunged in water. This, 
one would imagine, a priori , to be the moft nox- 
ious of all kinds of air. For if common air only 
tainted with putrefa&ion be fo deadly, much more 
might one expert that air to be fo, which was ge- 
nerated from putrefaction only ; but it feems to be 
nothing more than common air tainted with jdu- 
trefa&ion, and therefore requires no other procefs 
to fweeten it. In this cafe, however, we feem to 
have an in fiance of the generation of genuine com- 
mon air, though mixed with fomething that is 
foreign to it. Perhaps the refiduum of fixed air 
may be another inflance of the fame nature. 
Fixed air is equally difFufed through the whole 
mafs of any quantity of putrid air with which it is 
mixed ; for dividing the mixture into two equal 
parts, they were reduced in the fame proportion 
by paffing through water. But this is alio the cafe 
with fomleof the kinds of air which will not incor- 
porate, as inflammable air, and air in which brim- 
flone has burned. 
If fixed air tend to correal air which has been 
injured by animal refpiration or putrefaction, lime- 
kilns, which difcharge great quantities of fixed air, 
may be wholefome in the neighbourhood of popu- 
lous cities, the atmofphere of which muff abound 
with putrid effluvia. I fhould think alfo that phy- 
ficians might avail themfelves of the application 
of 
