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? CAROLINE. It is, indeed, curious to think that we adorn ourselves with jewels of charcoal! MRS. B. There are many other substances, consisting chiefly of carbon, that are remarkably white. Cotton, for instance, is almost wholly carbon. CAROLINE. That, I own, I could never have imagined! --But pray, Mrs. B., since it is known of what substance diamond and cotton are composed, why should they not be manufactured, or imitated, by some chemical process, which would render them much cheaper, and more plentiful than the present mode of obtaining them? MRS. B.