he
operation was continued a long time, it made no sensible change in the
properties of the air. I also repeated the operation with pump-water,
but with as little effect. In this case, however, though the air was
agitated in a phial, which had a narrow neck, the surface of the water
in the bason was considerably large, and exposed to the common
atmosphere, which must have tended a little to favour the experiment.

In order to judge more precisely of the effect of these different
methods of agitating air, I transferred the very noxious air, which I
had hot been able to amend in the least degree by the former method,
into an open jar, standing in a trough of water; and when I had agitated
it till it was diminished about one third, I found it to be better than
air in which candles had burned out, as appeared by the test of the
nitrous air; and a mouse lived in 2-1/2 ounce measures of it a quarter
of an hour, and was not sensibly affected the first ten or twelve
minutes.

In order to determine whether the addition of any _acid_ to the water,
would make it more capable of restoring putrid air, I agitated a
quantity of it in a phial containing very strong vinegar; and after that
in _aqua fortis_, only half diluted with water; but by neither of these
processes was the air at all mended, though the agitation was repeated,
at intervals, during a whole day, and it was moreover allowed to stand
in that situation all night.

Since, however, water in these experiments must have imbibed and
retained a certain portion of the noxious effluvia, before they could be
transmitted to the external air, I do not think it improbable but that
the agitation of the sea and large lakes may be of some use for the
purification of the atmosphere, and the putrid matter contained in water
may be imbibed by aquatic plants, or be deposited in some other manner.

Having found, by several experiments above-mentioned that the proper
putrid effluvium is something quite distinct from fixed air, and
finding, by the experiments of Dr. Macbride, that fixed air corrects
putrefaction; it occured to me, that fixed air, and air tainted with
putrefaction, though equally, noxious when separate, might make a
wholesome mixture, the one, correcting the other; and I was confirmed in
this opinion by, I believe, not less than fifty or sixty instances, in
which air, that had been made in the highest degree noxious, by
respiration or putrefaction, was so far sweetened, by