if it combines with oxygen, can we any longer call it pure?

MRS. B.

I was going to say, that, in this operation, the air must be excluded.

CAROLINE.

How then can the vapour of the oil and water fly off?

MRS. B.

In order to produce charcoal in its purest state (which is, even then,
but a less imperfect sort of carbon), the operation should be performed
in an earthen retort. Heat being applied to the body of the retort, the
evaporable part of the wood will escape through its neck, into which no
air can penetrate as long as the heated vapour continues to fill it. And
if it be wished to collect these volatile products of the wood, this can
easily be done by introducing the neck of the retort into the water-bath
apparatus, with which you are acquainted. But the preparation of common
charcoal, such as is used in kitchens and manufactures, is performed on
a much larger scale, and by an easier and less expensive process.

EMILY.

I have seen the process of making common charcoal. The wood is ranged on
the ground in a pile of a pyramidical form, with a fire underneath; the
whole is then covered with clay, a few holes only being left for the
circulation of air.

MRS. B.

These holes are closed as soon as the wood is fairly lighted, so that
the combustion is checked, or at least continues but in a very imperfect
manner; but the heat produced by it is sufficient to force out and
volatilize, through the earthy cover, most part of the oily and watery
principles of the wood, although it cannot reduce it to ashes.

EMILY.

Is pure carbon as black as charcoal?

MRS. B.

The purest charcoal we can prepare is so; but chemists have never yet
been able to separate it entirely from hydrogen. Sir H. Davy says, that
the most perfect carbon that is prepared by art contains about five per
cent. of hydrogen; he is of opinion, that if we could obtain it quite
free from foreign ingredients, it would be metallic, in common with
other simple substances.

But there is a form in which charcoal appears, that I dare say will
surprise you. --This ring, which I wear on my finger, owes its
brilliancy to a small piece of carbon.

CAROLINE.

Surely, you are jesting, Mrs. B.?

EMILY.

I thought your ring was diamond?

MRS. B.

It is so. But diamond is nothing more than carbon in a crystallized
state.

EMILY.

That is astonishing! Is it possible to see two things apparently more
different than diamond and charcoal?

CA