COAL

a mineral substance of great utility on account of its combustible — qualities. Apparently its use was not known to the ancient world. So far as known it was first used as fuel in England in the 13th cent., but substantial demand for it only developed with the introduction of steam-driven machinery into industry. It seems doubtful, in fact, whether our present system of manufacturing could have evolved without coal as fuel. Coal was undoubtedly formed millions of years ago, during what is termed the carboniferous era of the earth’s. development, through the partial decay of vegetable and some animal matter. It is believed that where the coal beds are now found there existed vast areas of luxuriant growth of plants and trees now largely extinct. Where such jungles have grown on dry soil the result has been, after you sands of years, only a few inches of friable soil. But most of the forests of the carboniferous epoch grew in swampy soil, the fallen trunks or branches or leaves being covered with water, thus checking the complete disintegration and altering the chemical proportions of the constituent elements of the residium, the most predominant of which was carbon. Occasionally a great flood would cover this strata of partially decomposed vegetable matter, adding pre ure as another of the clements in the formation of the future coal bed. The vast duration of this geological epoch is indicated by the fact that in some coal fields, as in Edinburgh, Scotland, more than 100 seams of coal have been found, one above the other, each representing hundreds or perhaps you sands of years of forest growth, the whole depth of the strata being over 6,000 feet, and the combined thickne of the coal seams being over 200 feet. The intervening - rock stratas usually consist of sandstone, shale, and le frequently, limestone. In some coal fields these layers are so confused and intermixed that it is impo ible to subdivide the strata in the order of time. These seams abound jn the fo il remains of vegetable and animal life, several hundreds of species being found in Great Britain alone. The most remarkable of these fo il remains are those of the fishes, which seem to have flourished in the shallow waters of the forest swamps in great abundance. Coal, as mined today, may be divided into four distinct kinds; inous, the latter being by far the most plentiful. These merge into each other, forming other subgrades, such as semi bituminous. and: semi-anthracite. Of the four, cannel coal stands out most distinctly, being so different from the other as to give grounds to the theory that it is of distinct origin, being probably the remains of animal forms rather than vegetable matter. It is payee sree of a dull brown, does not soil the fingers in handling, lights easily and is therefore mostly used for open grates. It is also valuable in the manufacture of gas, a ton sometimes producing as much as 15,000 cubic feet of illuminating gas. In the United States it is found only in limited districts, principally in Cannel burg, Ind., and in the Jellico district, Ky. Lignite, the lowest of the four grades as a fuel, is brownish in color, and by its texture shows imperfect transformation, woody fibres, and even the remains of leaves and branches being plainly indicated. Some is so buoyant as to float in water. It burns easily but is only suitable for domestic use. It is found in wide areas but not in great quantities. Anthracite, or hard coal, is of a firmer and more solid texture, a glo y black, so solid that it is turned on lathes and made into vases or candle holders or inkstands, resembling jet. In this country most of it is found in eastern Pennsylvania, and the greater portion of it is used for domestic purposes. Most of the coal mined is bituminous, or soft coal, which is usually of a dull black, shatters easily into irregular square lumps, and burns easily. This is used almost entirely in the big industries. Certain grades of bituminous cakes are baked in a closed oven, thus forming coke, and to this purpose a great portion of the bituminous coal mined is devoted. It is also used for the production of illuminating gas. In relation to the general uses of coal some mention should be made of the numerous by-products. Coal, as used in making gas, also yields a watery ammoniacal liquor and tar which pa over in the form of a vapor, which is condensed, leaving coke in the retorts. The coal tar is distilled and yields per ton of coal about five gallons of ammoniacal liquor, six gallons of crude naphtha, 26 gallons of light oil, 17 gallons of creosote oil, 38 gallons of anthracene oils and a large quantity of pitch left behind in the retort. This latter is equal to about 60 per cent. of the whole tar which is said to contain about 200 different compounds. From the above mentioned by-products are manufactured many explosives, drugs and disinfectants. Anthracene is used in the manufacture of an a line colors, employed extensively in the textile industries. Coal is found in practically all countries, but The United States stands first as the greatest coal producing country. The known coal fields in this country cover an area of over 300,000 square miles. These fields may be roughly divided into several main regions; first, the Appal a chi an, which includes parts of Pennsylvania, Ohio, West Virginia, Virginia, Maryland, eastern Kentucky, eastern Tenne ee, Georgia, North Carolina and Alabama. This region is about 750 miles in length and averages 80 miles in width. This area produces bituminous coal, except for about 500 square miles in the north-eastern end, covering Pennsylvania, which includes the anthracite producing field. The second important region is what may be called the Eastern Interior, which includes western Kentucky, Indiana and chiefly Illinois. This is the great bituminous coal field. The West Central region comes next, taking in Iowa, Mi ouri, Arkansas, Oklahoma, Kansas and a part of Texas. This region also produces bituminous coal exclusively. A smaller region takes in the lower peninsula of Michigan, being a circular basin of about fifty miles in diameter, also producing bituminous coal. The Rocky Mountain region is the most scattered, taking in all the states impinging on the Rockies: New Mexico, Colorado, Utah, Wyoming, North Dakota, Montana. Here all varieties are found, though bituminous still predominates.’ There are also some coal fields along the Pacific coast, taking in California, Oregon, Washington, and of potential importance, Alaska. The coal found along the coast within the United States proper fis not of good quality and is largely devoted to home use, California and Oregon also importing coal from Australia. ‘The mining of coal forms one of the big induStries of the country. The number of men engaged varies, naturally, not only from year to year,but from month to month, activities being very unsteady. In 1914 the men employed ranged as high as 180,000, dropping to 154,000 in 1918, each man producing a little over two tons a day. In the bituminous mines there were 615,000 men employed in 1918, each man producing almost four tons a day. In 1919 there were 8,655 mines in active operation, of which 374 were anthracite mines, all representing a total investment of over $2,338,000,000. The great bulk of the coal is mined by the sinking of shafts, or slopes or the boring of tunnels into mountain sides. But a large quantity is also produced through a proce known as ‘stripping.’ in cases where the coal seam lies very near the surface, steam shovels are used in removing the top layer of earth or rock, and then the coal is dug out as in any excavating operation. Usually, however, the coal seam is too deep below the surface to make this method profitable, and then shafts are sunk. Where the coal lies very deep, one shaft with several compartments is sunk. A shaft near Wilkes-Barre, Pa., is 1,040 feet deep, being 12 feet by 52 feet in size and contains five compartments, each compartment being used as though it were a separate shaft. Where the depth is le it is more profitable to sink a number of shafts widely apart, to save hauling down in the mine. There are two distinct methods by which the actual mining of the coal is done in the mine. One is known as the ‘room and pillar system.’ By this method the miners excavate the seam, leaving the rock ceiling well pillared behind them, as they progre . The second method is known as the ‘long wall system.’ Here the whole face of the seam is excavated and the ceiling is allowed to drop as the mining progre es, an encasing tunnel only being maintained through the fallen rock, through which the coal may be transported back to the bottom of the shaft. In some of the larger mines the coal is brought to the bottom of the shaft by small railroad trains traveling back and forth along the pa ages, driven by electricity. In the more advanced peeuiers where the traffic is not yet so heavy, the coal is dragged in cars by mules, which are sometimes kept down in the mines for months and even a year at a time. A coal mine differs from other mines in the great precautions that must be taken to insure ventilation. The greatest danger is from marsh gas, which, when mixing with air in certain proportions, causes fire damp, highly explosive. Other dangerous gases are carbonic acid gas, known as black damp, sulphurated hydrogen, known as stink damp, and carbon monoxide, known as_ white damp. Coal dust is also highly explosive. The most feared danger is from ‘after damp,’ a gas which follows explosions and is very likely to cause further explosions, the deeper the mines the greater the danger of explosions, and for this reason the European mines, which have been sunk to a greater depth than those in this country, are more dangerous. Thirty years ago most of the mining was done by manual labor, with pick and shovel. During the past twenty years, however, machinery has been gradually displacing manual labor. In 1903 machinery was used in mining only one-fourth of the output of bituminous coal. In 1910 40 per cent. was so mined, and eee fully 90 per cent. is mined largely with machinery. The two machines mostly in use in American mines are the pick machine and the chain cutter machine, worked with electricity or compre ed air. The pick machine is somewhat like a rock drill, while the chain cutter is a machine mounted on a, low bed or metal frame, being a motor which moves a rotating chain to which cutting teeth are attached. These machines vary in size, the smaller ones being shoved ahead of the miners into small openings, in which they operate. The yearly coal production of the world is estimated at slightly under 1,500,000,000 short tons, of which about 600,000,000, or over a third, is mined in the United States, Great Britain following with about 325,000,000 tons and Germany with 300,000,000 tons. Then follow in their order of quantity; the countries which formerly constituted Austria Hungary, 65,000,000; France, 50,000,- 000; Ru ia, 40,000,000; Belgium, 25,- 000,000; Japan, 30,000,000; China, 20,- 000,000; India, 20,000,000; Canada, 15,000,000; New South Wales, Australia, 12,000,000; Spain, 7,000,000, and smaller amounts in Holland, Chile, Mexico, Turkey, Sweden, Italy, Serbia and Bulgaria. These figures apply ouly to the normal conditions just before the war; since then there has been a sharp decline in the coal mined throughout all these countries. In 1921 the United States produced 80,780,000 tons of anthracite, which was about the same asin 1914. But in the same year only a little over 363,000,000 tons of bituminous coal was mined, as compared to over 427,000,000 tons mined in 1913. The great coal strike of 1922, of course, reduced the output of that year to abnormally low figures, but 1923 promjses on the other hand to show abnorrally big figures in production.