frame of wood_, that
the fresh air may have an opportunity of getting to the bottoms of them,
and circulating through them. In the inside I put a quantity of paper or
tow, which must be changed, and the vessel washed and dried, every two
or three days. This is most conveniently done by having another
receiver, ready cleaned and prepared, into which the mice may be
transferred till the other shall be cleaned.

Mice must be kept in a pretty exact temperature, for either much heat or
much cold kills them presently. The place in which I have generally kept
them is a shelf over the kitchen fire-place where, as it is usual in
Yorkshire, the fire never goes out; so that the heat varies very little,
and I find it to be, at a medium, about 70 degrees of Fahrenheit's
thermometer. When they had been made to pass through the water, as they
necessarily must be in order to a change of air, they require, and will
bear a very considerable degree of heat, to warm and dry them.

I found, to my great surprize, in the course of these experiments, that
mice will live intirely without water; for though I have kept them for
three or four months, and have offered them water several times, they
would never taste it; and yet they continued in perfect health and
vigour. Two or three of them will live very peaceably together in the
same vessel; though I had one instance of a mouse tearing another almost
in pieces, and when there was plenty of provisions for both of them.

In the same manner in which a mouse is put into a vessel of any kind of
air, a _plant_, or any thing else, may be put into it, viz. by passing
it through the water; and if the plant be of a kind that will grow in
water only, there will be no occasion to set it in a pot of earth, which
will otherwise be necessary.

There may appear, at first sight, some difficulty in opening the mouth
of a phial, containing any substance, solid or liquid, to which water
must not be admitted, in a jar of any kind of air, which is an operation
that I have sometimes had recourse to; but this I easily effect by means
of _a cork cut tapering_, and a strong, wire thrust through it, as in
fig. 4, for in this form it will sufficiently fit the mouth of any
phial, and by holding the phial in one hand, and the wire in the other,
and plunging both my hands into the trough of water, I can easily convey
the phial through the water into the jar; which must either be held by
an assistant, or be fastened by st