and 2-1/2 wide, being such as I have
generally used for electrical batteries, but I have likewise vessels of
very different forms and sizes, adapted to particular experiments.

When I want to remove vessels of air from the large trough, I place them
in _pots_ or _dishes_, of various sizes, to hold more or less water,
according to the time that I have occasion to keep the air, as fig. 2.
These I plunge in water, and slide the jars into them; after which they
may be taken out together, and be set wherever it shall be most
convenient. For the purpose of merely removing a jar of air from one
place to another, where it is not to stand longer than a few days, I
make use of common _tea-dishes_, which will hold water enough for that
time, unless the air be in a state of diminution, by means of any
process that is going on in it.

If I want to try whether an animal will live in any kind of air, I first
put the air into a small vessel, just large enough to give it room to
stretch itself; and as I generally make use of _mice_ for this purpose,
I have found it very convenient to use the hollow part of a tall
beer-glass, _d_ fig. 1, which contains between two and three ounce
measures of air. In this vessel a mouse will live twenty minutes, or
half an hour.

For the purpose of these experiments it is most convenient to catch the
mice in small wire traps, out of which it is easy to take them, and
holding them by the back of the neck, to pass them through the water
into the vessel which contains the air. If I expect that the mouse will
live a considerable time, I take care to put into the vessel something
on which it may conveniently sit, out of the reach of the water. If the
air be good, the mouse will soon be perfectly at its ease, having
suffered nothing by its passing through the water. If the air be
supposed to be noxious, it will be proper (if the operator be desirous
of preserving the mice for farther use) to keep hold of their tails,
that they may be withdrawn as soon as they begin to shew signs of
uneasiness; but if the air be thoroughly noxious, and the mouse happens
to get a full inspiration, it will be impossible to do this before it be
absolutely irrecoverable.

In order to _keep_ the mice, I put them into receivers open at the top
and bottom, standing upon plates of tin perforated with many holes, and
covered with other plates of the same kind, held down by sufficient
weights, as fig. 3. These receivers stand upon _a