The chief coal-fields of N

America are: 1. The anthracite fields of e. Pa. 2. The bituminous coal-fields of w. Pa., O., W. Va., Ky., Tenn., etc., to Ala. 3. The bituminous coal-fields of Ill. and Ind. 4. The bituminous coal-fields of Mo. and Ia. 5. The bituminous coal-fields of Mich. 6. The bituminous coal-fields of Nova Scotia. Of these fields the 1st and 2d are the most important for the quantity and quality of their yield. In the 3d. 4th, and 5th, the beds are thinner and the quality is inferior; in the 5th especially the coal is of comparatively little value. The 6th is fully equal to the 2d in quality, but much le in extent. At the present rate of increase in the consumption of coal there is no probability of the exhaustion of the N. American fields for many centuries, though the end of the Pa. anthracite will come much sooner and indeed is already in sight. Coal consists largely of carbon, with some chemically combined hydrogen, oxygen and nitrogen, and varying quantities of inorganic ash. Coals are cla ed as lignite or brown, soft or bituminous, and hard or anthracite coal. Lignite is of a dark brown to black color, frequently shows a woody structure, burns with a feeble, yellow, smoky flame, without much heat and with a smell of tarry matter. The sp. gr. is between 1 and 1.40, and in composition the fixed carbon varies between 50 and 70 per cent, or, if the water is driven off, between 60 and 80. Large beds of lignite are found in Europe, where it is used for purposes not requiring a strong heat, as evaporating solutions, burning lime, and for domestic uses. Practical use shows that it takes 3 parts of lignite by volume to have the same heating effect as 1 part of hard coal, or 24 parts by weight. It excels kiln-dried wood, weight for weight, in evaporating power, being able to evaporate 5 to 6 times its weight of water. It is some being too soft. Bituminous coals are black, compact substances showing no sign of vegetable structure. They are brittle, opaque, dull or shining, and when heated in closed ve els leave coke. They are divided into several cla es, such as caking and non-caking, long flame and short flame. The caking coals become pasty when heated, swell up, give off bubbles of gas burning with a bright yellow flame, and if air is not present form a hard lump of coke. Non-caking coals are dry, and leave a powder instead of coke. Long-flame coal is particularly chosen for use in long furnaces, where the heat is to be carried a distance from the fire-place; this peculiarity is due to a large proportion of rich hydrocarbons in it. Caking coals with a long flame are suited for making illuminating gas, as they give large quantities of rich gas, and afford a good coke, which finds a ready market. Caking coals with short flame are suitable for blacksmith's use. Non-caking coal with long flame is used in reverberatory furnaces and in evaporating, also for heating large ovens to an even temperature. Non-caking coal with short flame makes a good coal for raising steam, as it does not cake and clog up the grate, neither does the flame stop up the flues of the boiler. The chemical composition of these coals varies from 75 to 90 per cent of carbon, of which 55 to 85 per cent is fixed, and remains in the coke. The sp. gr. is 1.2 to 1.4, and will evaporate 8 to 10 times their weight of water. Cannel coal is dull, compact. very rich in bituminous matter, and therefore suitable for gas making. Anthracite or stone coal is jet black, hard, and has a sp. gr. of 1.3 to 1.75. It contains very little volatile matter, and does not produce a coke. The composition varies between 80 and 95 per cent of fixed carbon, with 5 to 15 per cent of ash. The evaporative value of these coals is high, being 9 to 12 times their weight of water. They burn with a short, blue flame, giving an intense heat, but requiring more of a body of fire to keep them ignited than the softer coals. In England, where the most of the coal is bituminous, distinctions are based largely on prominent physical characters or adaptability to special uses. In the U. S. the custom is to cla ify coal (excluding lignite) as anthracite, when containing le than 6 per cent volatile matter; semi-anthracite, in which the volatile matter is more than 6 per cent and le than 10 per cent; semi-bituminous, where the volatile matter is between 10 and 18 per cent; and bituminous, if the amount of volatile matter is more than 18 per cent. The most extensive deposits of coal are found in the Carboniferous formation, though it is also abundant in rocks of Mesozoic and of Tertiary age. In 1893 the amount of coal mined in the world was about 550,000,000 tons, of which Great Britain produced about 180,000,000, the U. S. more than 160,000,000, and Germany 95,000,000. In 1882 the aggregate production was le than 400,000,000 tons, and in 1845 only 50,000,000 tons.