water. This, one
would imagine, _a priori_, to be the most noxious of all kinds of air.
For if common air only tainted with putrefaction be so deadly, much more
might one expect that air to be so, which was generated from
putrefaction only; but it seems to be nothing more than common air (or
at least that kind of fixed air which is not absorbed by water) tainted
with putrefaction, and therefore requires no other process to sweeten
it. In this case, however, we seem to have an instance of the generation
of genuine common air, though mixed with something that is foreign to
it. Perhaps the residuum of fixed air may be another instance of the
same nature, and also the residuum of inflammable air, and of nitrous
air, especially nitrous air loaded with phlogiston, after long agitation
in water.

Fixed air is equally diffused through the whole mass of any quantity of
putrid air with which it is mixed: for dividing the mixture into two
equal parts, they were reduced in the same proportion by passing through
water. But this is also the case with some of the kinds of air which
will not incorporate, as inflammable air, and air in which brimstone has
burned.

If fixed air tend to correct air which has been injured by animal
respiration or putrefaction, _lime kilns_, which discharge great
quantities of fixed air, may be wholesome in the neighbourhood of
populous cities, the atmosphere of which must abound with putrid
effluvia. I should think also that physicians might avail themselves of
the application of fixed air in many putrid disorders, especially as it
may be so easily administered by way of _clyster_, where it would often
find its way to much of the putrid matter. Nothing is to be apprehended
from the distention of the bowels by this kind of air, since it is so
readily absorbed by any fluid or moist substance.

Since fixed air is not noxious _per se_, but, like fire, only in excess,
I do not think it at all hazardous to attempt to _breathe_ it. It is
however easily conveyed into the _stomach_, in natural or artificial
Pyrmont water, in briskly-fermenting liquors, or a vegetable diet. It
is even possible, that a considerable quantity of fixed air might be
imbibed by the absorbing vessels of the skin, if the whole body, except
the head, should be suspended over a vessel of strongly-fermenting
liquor; and in some putrid disorders this treatment might be very
salutary. If the body was exposed quite naked, there would be very