[ 2°3 ] 
imbibed by aquatic plants, or be depofited in fome 
other manner. 
Having found, by feveral experiments above- 
mentioned, that the proper putrid effluvium is fome- 
thing quite diflinCt from fixed air, and finding, by 
the experiments of Dr. Macbride, that fixed air cor- 
rects putrefaction ; I once concluded that this effeCt 
was produced, not by Hopping the flight of the fixed 
air, or reftoring to the putrefying fubflance the 
very fame thing that had efcaped from it; and 
which was the common vinculum of all its parts 
(which is that ingenious author’s hypothefis) but 
by an affinity between the fixed air and the putrid- 
effluvium. It therefore occurred to me, that fixed 
air, and air tainted with putrefaction, though 
equally noxious when feparate, might make a 
wholefome mixture, the one correcting the other ; 
and I was confirmed in this opinion by, I believe, - 
not lefs than fifty or fixty inflances, in which air, 
that had been made in the higheft degree noxious, 
by refpiration or putrefaction, was fo far fweetened, 
by a mixture of about four times as much fixed air 
that afterwards mice lived in it exceedingly well, ' 
and in fome cafes almoft as long as in common air. 
I found it, indeed, to be more difficult to reftore 
old putrid air by this means ; but I hardly ever 
failed to do it, when the two kinds of air had flood 
a long time together, by which I mean about a 
fortnight or three weeks. 
The reafon why I do not a'bfolutely conclude ' 
that the reftoration of air in thefe cafes was the 5 
effeCt of fixed air, is that, when I made a trial of 
the mixture, I fometimes agitated the two kinds * 
D d 2 of 
