COAL, a solid mineralized vegetable matter that can be used for fuel. In the sense of a piece of glowing fuel, thence a piece of fuel, whether dead or alive, the word is common to all languages of the Gothic stock, and seems allied to the Latin caleo, to be hot, and is allied to glow and kiln. The different sorts of fuel are distinguished by prefixes, as char-Coal, pit-Coal, sea-Coal, but, owing to the eminent importance of mineral or pit-Coal, the word Coal alone has come to be used in this special signification. Coal is one of the most important of all minerals; it consists chiefly of carbon, and is universally regarded as of vegetable origin. It occurs generally in strata or beds; it is always of black or blackish-brown color; some of the varieties have considerable vitreous or resinous luster; some are destitute of luster; some have a shell-like fracture, and some have a sort of salty structure, and are readily broken into cubical or rhomboidal fragments. In a general way we may define Coal as a fossil fuel of a black color and stony consistency, which, when heated in close vessels, is converted into coke with the escape of volatile liquids and gases. The variety known in Great Britain as blind Coal, and in the United States as anthracite, no doubt gives off scarcely any volatile matter; but this is because it has undergone a natural distillation through metamorphism or other cause.
Divisions.—We may, therefore, divide Coal into two primary divisions, viz., Anthracite, which does not, and Bituminous, or soft Coal, which does, flame when kindled. Anthracite averages in analysis 85 to 87 per cent. of fixed carbon. The term “anthracite” is applied to all Coals containing more than 80 per cent. of fixed carbon. Various synonyms, such as stone Coal, glance Coal, culm, and Welsh Coal, also are used to designate this substance, which in Great Britain is used chiefly for smelting purposes and for raising steam, but in the United States is used also almost entirely for domestic fuel and manufacturing purposes. It is difficult to kindle, but gives out a high heat in burning, and holds fire for a long time. Bituminous Coal includes an almost endless number of varieties, one of the best marked being cannel or parrot Coal. Cannel Coal is so called from burning with a bright flame like a candle, and the name “parrot Coal” is given to 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, about 2,100 square miles; (4) the Northern or Great Plains area, about 88,000 square miles; (5) the Rocky Mountain area, about 37,000 square miles; (6) and (7) Pacific Coast area, about 1,900 square miles.
Anthracite Areas.—Commercially speaking, the anthracite division may be said to consist of Pennsylvania alone, although a small amount of anthracite coal is mined in other States. The original Coal beds of New England have been metamorphosed into graphite and graphitic Coal. This area is confined to eastern Rhode Island, and the counties of Bristol and Plymouth, Mass, The product mined from the beds, which may be more properly called graphite than Coal, requires a considerable degree of heat for combustion, and can be used only with other combustible material or under an intense draught or blast. Its principal use is in the direct manufacture of steel; the entire annual output is but a few thousand tons. There are five recognized principal divisions of the Pennsylvania anthracite region: (1) The Southern or Pottsville field, extending from the Lehigh river, at Mauch Chunk, S. E. to within a few miles of the Susquehanna river, directly W. of Harrisburg. (2) The Western Middle or Mahanoy and Shamokin field, extending from the easternmost headwaters of the Little Schuylkill river to the Susquehanna. These are sometimes grouped together and given the common name of the Schuylkill region. (3) The Eastern Middle or upper Lehigh field, lying between the Lehigh river and Catawissa creek, and mostly situated in Luzerne co. (4) The Northern or Wyoming and Lackawanna, mostly in Luzerne and Lackawanna cos. (5) The Loyalsock and Mehoopany field is within the area drained by the headwaters of two creeks of that name, 20 or 25 miles N. W. of the W. end of the field last mentioned. The anthracite region of Pennsylvania, as a whole, has a maximum length of about 115 miles, a maximum breadth of about 40 miles; area about 1,700 square miles; but the area underlaid by workable Coal beds is only about 470 square miles.
MINING COAL WITH AN ELECTRIC DRILL
Bituminous Areas.—The bituminous Coal areas of the United States may for convenience be grouped into seven divisions: the Triassic, the Appalachian, the Northern, the Central, the Western, the Rocky Mountain, and the Pacific Coast areas. The eastern Triassic area is composed chiefly of the Richmond basin, in Virginia, and the Deep River and the Dan River fields, in North Carolina. No extensive mining operations are now carried on in this area. The Appalachian field is immediately W. of the E. border of the Appalachian range, and extends from New York on the N. to Alabama on the S., its direction being N. E. and S. W.; length, about 900 miles; width, from 30 to 180 miles. There are in this region many varieties of bituminous Coal, the best and most productive beds on the whole being those of the Pittsburgh district and of West Virginia. The thickness of the coal measures in different sections varies from 100 to over 3,000 feet. The northern bituminous area is all in central Michigan. The coal here found is not of superior quality, and is used mostly for local supply. Of the central area three-fourths are in Illinois, less than one-sixth in Indiana, and about one-twelfth in western Kentucky. In the western field the most extensive mining operations have been carried on in Iowa and Missouri; its area is greater than that of any other one Coal field in the United States. The coals are of great variety; the best which has so far been mined is that of the Indian Territory. The Rocky Mountain Coal beds have have been found in the geological formations from the Carboniferous up to and including the Cretaceous, differing in this respect from those hitherto enumerated, which, with the exception of that in Virginia and North Carolina, are all confined to the Carboniferous. Coal has been mined in the Pacific States.
Coal Mining.—The cutting of a path through the harder rocks, as carried on by the ancient miners, was particularly laborious and unhealthy. Miners became subject to disorders of the lungs at an early age. Previous to the introduction of blasting, the implements used were wedges and hammers. Bit by bit pieces of rock were broken away, the operation being assisted by natural fissures in the rock and by the brittleness of the hard material. In this way the ancient miners cut coffin-shaped galleries 5 feet in height. At the present time the galleries or levels are usually 7½ feet high and 5 feet wide, thus affording facilities for traveling and for ventilation. Gunpowder was not applied to mining purposes until the beginning of the 17th century, and it made its way so slowly that it was not largely employed until the 18th century. Of late years rock-drills driven by steam or by compressed air have come largely into use. The bore-hole, when finished, is then charged. The gunpowder is inclosed in a little bag of cloth dipped in pitch and provided with a fuse. The fullest benefit of modern explosives, such as dynamite, gun-cotton and yonite, can be obtained only by the use of strong detonators fired by electricity, by which it is impossible to place a number of bore-holes in such a manner that when fired simultaneously they shall help one another. Blasting powder is still used for removing coal and millions of tons are obtained by its aid. In order to obviate the danger of explosions in fiery collieries, many ingenious substitutes for blasting have been proposed. For example, a hole is bored and wedges inserted to force down the Coal which has previously been under-cut with the pick.
JEFFREY LOADING CONVEYOR USED IN A COAL MINE
Various machines have been invented with a view of lessening the labor and expense of under-cutting coal seams. They work with compressed air or electricity, and have the cutters arranged on the periphery of a rotating disc, or on a traveling pitch chain. The coal, when broken down, is placed in cars and drawn to the bottom of the shaft and raised to the surface. The actual mode of working the coal varies greatly in every district. By the post-and-stall, or board-and-pillar, or (in Scotland) stoop-and-room, method the first stage of excavation is accomplished with the roof sustained by coal; in the long-wall method the whole of the coal is allowed to settle behind the miners, no sustaining pillars of coal being left. This, when well planned, is the safer, both as regards facility of ventilation and less liability to accidents from falls. At a Durham colliery, working the Harvey seam, 3½ feet in thickness, 5,185 tons of coal were obtained when working by the long-wall system and 5,052 tons when working by the post-and-stall system. In thick and highly inclined beds it is usual to remove the coal by horizontal slices and to fill the excavation with waste material. In some instances blast furnace slag is used for the purpose.
The great depth and size of modern collieries necessitate the raising of vast quantities of coal through a single shaft and the winding engines of modern erection are of extraordinary power.
Production.—The total coal production of the United States in 1919 was 544,263,000 short tons. Of this 458,063,000 tons were bituminous and 86,200,000 tons were anthracite. This production was a decrease of 133,949,000 tons over that of 1918. Pennsylvania produced the largest amount of coal for 1919, 145,300,000 tons of bituminous coal and 86,200,000 of anthracite coal. West Virginia was second with 75,500,000 tons; Illinois third with 64,600,000 tons; and Ohio fourth with 35,050,000 tons. Other States producing over 10,000,000 tons were Alabama, Indiana, and Colorado. The number of employees in the coal mines in the country in 1918 was 762,426. Of these 147,121 were employed in the anthracite mines and 615,305 were employed in the bituminous mines. The total value of the coal produced in 1918 was $1,828,290,287.
During the participation of the United States in the World War, the production of coal in sufficient quantity became an important problem. In 1918-1919 strikes in various fields produced a shortage of coal, and only by the most rigorous methods of distribution was it possible to obtain sufficient quantities to keep industrial plants running and to supply domestic demands. During 1918 industrial plants were shut down for certain periods owing to a shortage of coal. In 1920 conditions had greatly improved, and there was no alarming shortage of coal during that year. On Aug. 30, 1920, President Wilson approved a report of an anthracite wage commission which awarded from 17 to 20 per cent. increase over their previous pay to men employed in the anthracite coal mines. The men refused to accept the provisions of the commission and undertook a strike in September. The President refused to reopen the question of the wage award, and the strike subsided. The coal output for the first 8 months of 1920 indicated an increase in production over 1919. For 205 working days the production of bituminous coal was 347,406,000 tons, and nearly 30,000,000 tons more than were produced in the same period of 1919.
History.—The use of coal does not seem to have been known to the ancients, nor is it known at what time it began to be used for fuel. Some say that it was used by the ancient Britons, and at all events it was to some extent an article of household consumption during the Anglo-Saxon period as early as A. D. 852. There is reason for thinking that England was the first European country in which coal was used to a considerable extent. About the end of the 13th century it began to be used in London, but at first only in the arts and manufactures, and the innovation was complained of as injurious to health. In 1316 Parliament petitioned the king, Edward II., to prohibit the use of coal, and a proclamation was accordingly issued against it; but owing to a high price of wood its use soon became general in London. It was for a long time known there as Sea-Coal, because imported by sea.