hereafter appear not to favour them.

In a great variety of cases I have observed that there is a remarkable
_diminution_ of common, or respirable air, in proportion to which it is
always rendered unfit for respiration, indisposed to effervesce with
nitrous air, and incapable of farther diminution from any other cause.
The circumstances which produce this effect I had then observed to be
the burning of candles, the respiration of animals, the putrefaction of
vegetables or animal substances, the effervescence of iron filings and
brimstone, the calcination of metals, the fumes of charcoal, the
effluvia of paint made of white-lead and oil, and a mixture of nitrous
air.

All these processes, I observed, agree in this one circumstance, and I
believe in no other, that the principle which the chemists call
_phlogiston_ is set loose; and therefore I concluded that the diminution
of the air was, in some way or other, the consequence of the air
becoming overcharged with phlogiston,[11] and that water, and growing
vegetables, tend to restore this air to a state fit for respiration, by
imbibing the superfluous phlogiston. Several experiments which I have
since made tend to confirm this supposition.

Common air, I find, is diminished, and rendered noxious, by _liver of
sulphur_, which the chemists say exhales phlogiston, and nothing else.
The diminution in this case was one fifth of the whole, and afterwards,
as in other similar cases, it made no effervescence with nitrous air.

I found also, after Dr. Hales, that air is diminished by _Homberg's
pyrophorus_.

The same effect is produced by firing _gunpowder_ in air. This I tried
by firing the gunpowder in a receiver half exhausted, by which the air
was rather more injured than it would have been by candles burning in
it.

Air is diminished by a cement made with one half common coarse
turpentine and half bees-wax. This was the result of a very casual
observation. Having, in an air-pump of Mr. Smeaton's construction,
closed that end of the syphon-gage, which is exposed to the outward air,
with this cement (which I knew would make it perfectly air-light)
instead of sealing it hermetically; I observed that, in a course of
time, the quicksilver in that leg kept continually rising, so that the
measures I marked upon it were of no use to me; and when I opened that
end of the tube, and closed it again, the same consequence always took
place. At length, suspecting that this effect m