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 min ers cut coffin-shaped galleries 5 feet in height. At the present time the galleries or levels are usually 71/2 feet high and 5 feet wide, thus affording facilities for traveling and for ventilation. Gunpow der was not applied to mining purposes until the beginning of the 17th century, and it made its way so slowly that it lieries, many ingenious substitutes for blasting have been proposed. For ex ample, a hole is bored and wedges in serted to force down the Coal which has previously been under-cut with the pick.
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 elec tricity, 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 ex cavation 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 sustain ing pillars of coal being left. This, when well planned, is the safer, both as re gards facility of ventilation and less lia bility to accidents from falls. At a Dur ham colliery, working the Harvey seam, 31/2 feet in thickness, 5,185 tons of coal were obtained when working by the long wall system and 5,052 tons when work ing 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 ma terial. 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 erec tion 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 larg est amount of coal for 1919, 145,300,000 tons of bituminous coal and 86,200,000 of anthracite coal. West Virginia was sec
ond with 75,500,000 tons; Illinois third with 64,600,000 tons; and Ohio fourth with 35,050,000 tons. Other States pro ducing over 10,000,000 tons were Ala bama, Indiana, and Colorado. The num ber of employees in the coal mines in the country in 1918 was 762,426. Of these 147,121 were employed in the an thracite mines and 615,305 were em ployed 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 in dustrial plants running and to supply domestic demands. During 1918 indus trial 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 re open the question of the wage award, and the strike subsided. The coal out put for the first 8 months of 1920 indi cated an increase in production over 1919. For 205 working days the pro duction 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 cen tury it began to be used in London, but at first only in the arts and manu factures, and the innovation was com plained of as injurious to health. In 1316 Parliament petitioned the king, Ed ward 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.