Carbon is always obtained from some of its combinations, as from pitch, tar, rosin, wood, and oil. Various processes are employed for this purpose. Thus, by the combustion of rosin and oil, as well as pitch, tar, turpentine, &c. a soot is formed that collects, called lampblack, which is nothing more than the carbon or charcoal. When pit-coal is _charred_ in an oven, called a coke oven, all the bitumen and sulphur contained in it are disengaged, and a charcoal remains, called, however, _coke_. Wood, when charred is decomposed; all the volatile parts are disengaged with carburetted hydrogen gas, and the woody fibre is converted into coal. This coal is more or less dense according to the compactness of the wood. Hard woods furnish the most solid coal, and light woods on the contrary. When the solid parts of animals, as bone, are charred, the volatile products, principally ammonia or volatile alkali, are dissipated, and there remains a substance called bone-black, improperly called, _ivory black_. The carbonization of wood in the common way is well known: after it is cut to the lengths required, it is piled on the ground in a pyramidal form, and covered with sod and clay, leaving a place for the current of air, and the smoke. The wood is then set on fire, and when the whole is burnt to a coal the vents, &c. are closed with sod and clay. Nicholson (_Chemical Dictionary_) observes, that in the forest of Benon, near Rochelle, great attention is paid to the manufacture, so that the charcoal made there fetches twenty-five or thirty per cent. more than any other. The wood is that of the black oak. It is taken from ten to fifteen years old, the trunk as well as the branches, cut into billets about four feet long, and not split. The largest pieces, however, seldom exceed six or seven inches in diameter. The end that rests on the ground is cut a little sloping, so as to touch it merely with an edge, and they are piled nearly upright, but never in more than one story. The wood is covered all over about four inches thick with dry grass or fern, before it is enclosed in the usual manner with clay; and when the wood is charred, half a barrel of water is thrown over the pile, and earth to the thickness of five or six inches is thrown on, after which it is left four-and-twenty hours to cool. The wood is always used in the year in which it is cut.