it in Scotland from the crackling or chattering noise which some kinds of it make when burned. That of different localities varies much in appearance, but it is commonly dull and earthy, or with only a slight luster; some kinds are, however, bright and shining. In texture it is nearly always compact, and certain beds of it admit of being polished in slabs of considerable size, which approach black marble in appearance. Of this material vases, inkstands, boxes, etc., are made. Cannel Coal, from its comparative scarcity and high price, is not suitable for house fires, and is for the most part consumed in making gas, of which it yields from 8,000 to 15,000 cubic feet per ton. When distilled at a low red-heat it yields paraffine oil. The other varieties of bituminous Coal are so numerous that there are as many as 70 kinds of it imported into London alone. Still, among these there are three leading kinds: (1) Caking Coal, which cakes or fuses into one mass in the fire. It breaks into small uneven fragments, and is found largely at Newcastle and some other localities. (2) Splint, or hard Coal, occurring plentifully in Scotland, which is hard and has a kind of slaty fracture. It is not very easily kindled, but when lighted makes a clear, lasting fire. (3) Cherry, or soft Coal, which breaks easily into small, irregular cubes, has a beautiful, shining luster, is readily kindled, and gives out a cheerful flame and heat. It is common in Staffordshire. Brown Coal, or lignite, though inferior to true Coal, is, nevertheless, an important fuel in some countries, in default of a better kind.
Origin.—Several theories as to the origin of coal have been put forth from time to time. The one now generally received is that the rank and luxuriant vegetation which prevailed during the Carboniferous Period grew and decayed upon land raised but slightly above the sea; that by slow subsidence this thick layer of vegetable matter sank below the water and became gradually covered with sand, mud, and other mineral sediment; that then, by some slight upheaval of the sea-bottom or other process, a land surface was once more formed and covered with a dense mass of plants, which in course of time decayed, sank, and became overlaid with silt and sand as before. At length thick masses of stratified matter would accumulate, producing great pressure, and this, acting with chemical changes, would gradually mineralize the vegetable layers into Coal. Some experiments made by Dr. Lindley a few years ago showed that of a large number of plants kept immersed in water for two years, the ferns, lycopodiums, and pines were those which had the greatest powers of resisting decay, and Coal appears to be mainly composed of the substance of the ancient gigantic representatives of these three orders of plants. The interesting fact has also been lately proved by Huxley, Morris, Carruthers, and others, that in many instances the bituminous matter in Coal is formed almost wholly of the spore cases and spores of plants allied to our clubmosses and ferns.
Sources of Supply.—Since the prosperity of great national industries, as well as much of our domestic comfort, depends on the continuance of an abundant and cheap supply of fuel, much anxiety has arisen of late years regarding the future supply and price of Coal. An exhaustive survey of the Coal fields of the world has produced the estimate that there exist in the United States and Alaska, 4,231,000,000,000 tons, of which 22,000,000,000 tons is anthracite, 2,155,000,000,000 tons is bituminous, and 2,054,000,000,000 tons is sub-bituminous and lignite; Canada, 1,361,000,000,000 tons, of which 2,000,000,000 is anthracite and 313,000,000,000 is bituminous; China, 1,097,000,000,000 tons, of which 427,000,000,000 is anthracite; Germany, 467,000,000,000 tons, of which 452,000,000,000 tons is bituminous and the rest sub-bituminous; Great Britain, 209,000,000,000 tons, of which 12,000,000,000 is anthracite; Siberia, 192,000,000,000 tons, no anthracite; Australia, 183,000,000,000 tons, all bituminous or sub-bituminous; India, 87,000,000,000 tons, no anthracite; Russia in Europe, 66,000,000,000 tons, of which 41,000,000 is anthracite; Union of South Africa, 62,000,000,000 tons, of which 13,000,000,000 is anthracite; Austria, 59,000,000,000 tons, no anthracite; Colombia, 30,000,000,000 tons, no anthracite; Indo-China, 22,000,000,000 tons, all anthracite; France, 19,000,000,000 tons, of which 4,000,000,000 is anthracite; Belgium, 12,000,000,000 tons, no anthracite; Spain, 10,000,000,000 tons, of which 2,000,000,000 is anthracite; Spitzbergen, 9,000,000,000 tons, no anthracite; Japan, 9,000,000,000 tons, no anthracite; Holland, 5,000,000,000 tons, no anthracite; other countries, 24,000,000,000 tons, of which 3,000,000,000 is anthracite.
Total Coal reserves, 8,154,000,000,000 tons, of which 548,000,000,000 is anthracite; 4,302,000,000,000 is bituminous, and 3,304,000,000,000 is sub-bituminous and lignite.
Coal in the United States.—The entire area of these is about 330,000 square miles. The principal fields are (1) Eastern, approximately 70,000 square miles; (2) the Interior area, about 133,000 square miles; (3) the Gulf area,
