passing this air through water, it is presently reduced to its
original quantity again, with little or no change of quality.

I put about the quantity of half a nut-shell full of ether, inclosed in
a glass tube, through a body of quicksilver, into an ounce measure of
common air, confined by quicksilver; upon which it presently began to
expand, till it occupied the space of two ounce measures. It then
gradually contracted about one sixth of an ounce measure. Putting more
ether to it, it again expanded to two ounce measures; but no more
addition of ether would make it expand any farther. Withdrawing the
quicksilver, and admitting water to this air, without any agitation, it
began to be absorbed; but only about half an ounce measure had
disappeared after it had stood an hour in the water. But by once passing
it through water the air was reduced to its original dimensions. Being
tried by a mixture of nitrous air, it appeared not to be so good as
fresh air, though the injury it had received was not considerable.

All the phenomena of dilatation and contraction were nearly the same,
when, instead of common air, I used nitrous air, fixed air, inflammable
air, or any species of phlogisticated common air. The quantity of each
of these kinds of air was nearly doubled while they were kept in
quicksilver, but fixed air was not so much increased as the rest, and
phlogisticated air less; but after passing through the water, they
appeared not to have been sensibly changed by the process.

2. Spirit of wine yields no air by means of heat, the vapours being soon
condensed by cold, like the vapour of water; yet when, in endeavouring
to procure air from it, I made it boil, and catched the air which had
rested on the surface of the spirit, and which had been expelled by the
heat together with the vapour, in a vessel of quicksilver, and
afterwards admitted acid air to it, the vessel was filled with white
fumes, as if there had been a mixture of alkaline air along with it. To
what this appearance was owing I cannot tell, and indeed I did not
examine into it.

3. Having been informed by Dr. Small and Mr. Bolton of Birmingham, that
paper dipped in a solution of copper in spirit of nitre would take fire
with a moderate heat (a fact which I afterwards found mentioned in the
Philosophical Transactions) it occurred to me that this would be very
convenient for experiments relating to _ignition_ in different kinds of
air; and indeed I found that