st
as it is generated; and the offensive smell is a sufficient proof that
it is not fixed air. For this has a very agreeable flavour, whether it
be produced by fermentation, or extracted from chalk by oil of vitriol;
affecting not only the mouth, but even the nostrils; with a pungency
which is peculiarly pleasing to a certain degree, as any person may
easily satisfy himself, who will chuse to make the experiment.

If the water in which the mouse was immersed, and which is saturated
with the putrid air, be changed, the greater part of the putrid air,
will, in a day or two, be absorbed, though the mouse continues to yield
the putrid effluvium as before; for as soon as this fresh water becomes
saturated with it, it begins to be offensive to the smell, and the
quantity of the putrid air upon its surface increases as before. I kept
a mouse producing putrid air in this manner for the space of several
months.

Six ounce measures of air not readily absorbed by water, appeared to
have been generated from one mouse, which had been putrefying eleven
days in confined air, before it was put into a jar which was quite
filled with water, for the purpose of this observation.

Air thus generated from putrid mice standing in water, without any
mixture of common air, extinguishes flame, and is noxious to animals,
but not more so than common air only tainted with putrefaction. It is
exceedingly difficult and tedious to collect a quantity of this putrid
air, not miscible in water, so very great a proportion of what is
collected being absorbed by the water in which it is kept; but what that
proportion is, I have not endeavoured to ascertain. It is probably the
same proportion that that part of fixed air, which is not readily
absorbed by water, bears to the rest; and therefore this air, which I at
first distinguished by the name of _the putrid effluvium_, is probably
the same with fixed air, mixed with the phlogistic matter, which, in
this and other processes, diminishes common air.

Though a quantity of common air be diminished by any substance
putrefying in it, I have not yet found the same effect to be produced by
a mixture of putrid air with common air; but, in the manner in which I
have hitherto made the experiment, I was obliged to let the putrid air
pass through a body of water, which might instantly absorb the
phlogistic matter that diminished the common air.

Insects of various kinds live perfectly well in air tainted with anima