e of
your body, the table, which before felt the colder, would now feel the
hotter of the two; for, as in the first case it took the heat most
rapidly from your hand, so it will now impart heat most rapidly to it.
Thus the marble table, which seems to us colder than the mahogany one,
will prove the hotter of the two to the ice; for, if it takes heat more
rapidly from our hands, which are warmer, it will give out heat more
rapidly to the ice, which is colder. Do you understand the reason of
these apparently opposite effects?

EMILY.

Perfectly. A body which is a good conductor of caloric, affords it a
free passage; so that it penetrates through that body more rapidly than
through one which is a bad conductor; and consequently, if it is colder
than your hand, you lose more caloric, and if it is hotter, you gain
more than with a bad conductor of the same temperature.

MRS. B.

But you must observe that this is the case only when the conductors are
either hotter or colder than your hand; for, if you heat different
conductors to the temperature of your body, they will all feel equally
warm, since the exchange of caloric between bodies of the same
temperature is equal. Now, can you tell me why flannel clothing, which
is a very bad conductor of heat, prevents our feeling cold?

CAROLINE.

It prevents the cold from penetrating . . . . . . . .

MRS. B.

But you forget that cold is only a negative quality.

CAROLINE.

True; it only prevents the heat of our bodies from escaping so rapidly
as it would otherwise do.

MRS. B.

Now you have explained it right; the flannel rather keeps in the heat,
than keeps out the cold. Were the atmosphere of a higher temperature
than our bodies, it would be equally efficacious in keeping their
temperature at the same degree, as it would prevent the free access of
the external heat, by the difficulty with which it conducts it.

EMILY.

This, I think, is very clear. Heat, whether external or internal, cannot
easily penetrate flannel; therefore in cold weather it keeps us warm;
and if the weather was hotter than our bodies, it would keep us cool.

MRS. B.

The most dense bodies are, generally speaking, the best conductors of
heat; probably because the denser the body the greater are the number of
points or particles that come in contact with caloric. At the common
temperature of the atmosphere a piece of metal will feel much colder
than a piece of wood, and the latter than a pie