diation should correspond with that
of absorption. It is, in fact, cause and effect; for a body cannot
radiate heat without having previously absorbed it; just as a spring
that is well fed flows abundantly.

MRS. B.

Fluids are in general very bad radiators of caloric; and air neither
radiates nor absorbs caloric in any sensible degree.

We have not yet concluded our observations on free caloric. But I shall
defer, till our next meeting, what I have further to say on this
subject. I believe it will afford us ample conversation for another
interview.

CONVERSATION III.

CONTINUATION OF THE SUBJECT.

MRS. B.

In our last conversation, we began to examine the tendency of caloric to
restore an equilibrium of temperature. This property, when once well
understood, affords the explanation of a great variety of facts which
appeared formerly unaccountable. You must observe, in the first place,
that the effect of this tendency is gradually to bring all bodies that
are in contact to the same temperature. Thus, the fire which burns in
the grate, communicates its heat from one object to another, till every
part of the room has an equal proportion of it.

EMILY.

And yet this book is not so cold as the table on which it lies, though
both are at an equal distance from the fire, and actually in contact
with each other, so that, according to your theory, they should be
exactly of the same temperature.

CAROLINE.

And the hearth, which is much nearer the fire than the carpet, is
certainly the colder of the two.

MRS. B.

If you ascertain the temperature of these several bodies by a
thermometer (which is a much more accurate test than your feeling), you
will find that it is exactly the same.

CAROLINE.

But if they are of the same temperature, why should the one feel colder
than the other?

MRS. B.

The hearth and the table feel colder than the carpet or the book,
because the latter are not such good _conductors of heat_ as the former.
Caloric finds a more easy passage through marble and wood, than through
leather and worsted; the two former will therefore absorb heat more
rapidly from your hand, and consequently give it a stronger sensation of
cold than the two latter, although they are all of them really of the
same temperature.

CAROLINE.

So, then, the sensation I feel on touching a cold body, is in proportion
to the rapidity with which my hand yields its heat to that body?

MRS. B.

Precisely;