I shall observe once for all, that this process
has never failed to restore any kind of noxious air on which I have
tried it, viz. air injured by respiration or putrefaction, air infected
with the fumes of burning charcoal, and of calcined metals, air in which
a mixture of iron filings and brimstone, that in which paint made of
white lead and oil has stood, or air which has been diminished by a
mixture of nitrous air. Of the remarkable effect which this process has
on nitrous air itself, an account will be given in its proper place.

If this process be made in water deprived of air, either by the
air-pump, by boiling, or by distillation, or if fresh rain-water be
used, the air will always be diminished by the agitation; and this is
certainly the fairest method of making the experiment. If the water be
fresh pump-water, there will always be an increase of the air by
agitation, the air contained in the water being set loose, and joining
that which is in the jar. In this case, also, the air has never failed
to be restored; but then it might be suspected that the melioration was
produced by the addition of some more wholesome ingredient. As these
agitations were made in jars with wide mouths, and in a trough which had
a large surface exposed to the common air, I take it for granted that
the noxious effluvia, whatever they be, were first imbibed by the water,
and thereby transmitted to the common atmosphere. In some cases this was
sufficiently indicated by the disagreeable smell which attended the
operation.

After I had made these experiments, I was informed that an ingenious
physician and philosopher had kept a fowl alive twenty-four hours, in a
quantity of air in which another fowl of the same size had not been able
to live longer than an hour, by contriving to make the air, which it
breathed, pass through no very large quantity of acidulated water, the
surface of which was not exposed to the common air; and that even when
the water was not acidulated, the fowl lived much longer than it could
have done, if the air which it breathed had not been drawn through the
water.

As I should not have concluded that this experiment would have succeeded
so well, from any observations that I had made upon the subject, I took
a quantity of air in which mice had died, and agitated it very strongly,
first in about five times its own quantity of distilled water, in the
manner in which I had impregnated water with fixed air; but though t