he phial only, without a plant growing in it, a younger mouse
continued not longer than two or three seconds, and was taken out quite
dead. It never breathed after, and was immediately motionless. After
half an hour, in which time the larger mouse (which I had kept alive,
that the experiment might be made on both the kinds of air with the very
same animal) would have been sufficiently recruited, supposing it to
have received any injury by the former experiment, was put into the same
vessel of air; but though it was withdrawn again, after being in it
hardly one second, it was recovered with difficulty, not being able to
stir from the place for near a minute. After two days, I put the same
mouse into an equal quantity of common air, and observed that it
continued seven minutes without any sign of uneasiness; and being very
uneasy after three minutes longer, I took it out. Upon the whole, I
concluded that the restored air wanted about one fourth of being as
wholesome as common air. The same thing also appeared when I applied the
test of nitrous air.

In the seven days, in which the mint was growing in this jar of noxious
air, three old shoots had extended themselves about three inches, and
several new ones had made their appearance in the same time. Dr.
Franklin and Sir John Pringle happened to be with me, when the plant had
been three or four days in this state, and took notice of its vigorous
vegetation, and remarkably healthy appearance in that confinement.

On the 30th of the same month, a mouse lived fourteen minutes, breathing
naturally all the time, and without appearing to be much uneasy, till
the last two minutes, in the vessel containing two ounce measures and a
half of air which had been rendered noxious, by mice breathing in it
almost a year before, and which, I had found to be most highly noxious
on the 19th of this month, a plant having grown in it, but not
exceedingly well, these eleven days; on which account I had deferred
making the trial so long. The restored air was affected by a mixture of
nitrous air, almost as much as common air.

As this putrid air was thus easily restored to a considerable degree of
fitness for respiration, by plants growing in it, I was in hopes that by
the same means it might in time be so much more perfectly restored, that
a candle would burn in it; and for this purpose I kept plants growing in
the jars which contained this air till the middle of August following,
but did not t