cial counter-balance assists the engine to hoist the loaded ascending cage. Haulage in mines is accomplished by animal power or by steam hoisting engines operating a system of rope haulage or by mine locomotives operated by steam, electricity, compressed air, or gasoline.
The preparation of mined coal for the market consists in screening the coal over bars and through revolving or over shaking screens, together with breaking it with rolls to produce the required market size. The large lumps of slate or other impurities are separated by hand, while the smaller portions are picked out by automatic pickers or by hand by boys or old men seated along the chutes leading to the shipping pockets or bins. When coal contains much sulphur, this is frequently removed by washing it with water in special washing plants.
Bibliography. Lesley, Manual of Coal and Its Topography (Philadelphia, 1850)—a good work, but difficult to find; Chance, “Coal-Mining,” in Second Geological Survey of Pennsylvania, Report AC (Harrisburg, 1883); Hughes, A Textbook of Coal-Mining (London, 1899); Peel, Elementary Textbook of Coal-Mining (London, 1901); Macfarlane, The Coal Regions of America, Their Topogrnphy, Geology, and Development (New York, 1875); Nicolls, The Story of American Coals (Philadelphia, 1897); Lesley and others, “Reports on the Coal-Fields of Pennsylvania,” in various publications of the Second Geological Survey of Pennsylvania (Harrisburg). Numerous scattered papers have been published in the following annuals and periodicals: Transactions of the American Institute of Mining Engineers (New York); The Mineral Industry (New York); The Engineering and Mining Journal (New York); Mines and Minerals (Scranton, Pa.); “Mineral Resources of the United States,” United States Geological Survey (Washington). For foreign coal deposits, consult: Memoirs of the Geological Survey of Great Britain (London); Reports of Progress of the Geological Survey of the United Kingdom (London); Annales de la société géologique de Belgique (Liége, 1874 et seq.); Bulletin de la société belge de géologie, de paléontologie et d'hydrologie (Brussels, 1877 et seq.); Annales des mines (Paris, 1816 et seq.); Bulletin de la société géologique de France (Paris, 1896 et seq.); Lozé, Les charbons britanniques et leur épuisement (Paris, 1900); Zeitschrift für praktische Geologie (Berlin, 1893 et seq.). See Anthracite; Bituminous Coal; Carboniferous System; Coke; Culm; Cretaceous System; Peat; Tertiary System; Graphite; Carbon; Fire-Clay; and the articles on the different States and countries in which coal has been found.
COAL APPLES. The name given to some curious specimens of spheroidal anthracite coal found in the Mammoth seam of Pennsylvania. They vary from one-fourth inch to ten inches in diameter, but are usually about the size of a hen's egg. They are thought to be due to jointing.
COAL-BREAKER. A structure containing machinery for the purpose of crushing, sorting, and cleaning anthracite coal. The breaker is often as much as 150 feet high, and rarely less than 80 feet. The coal, as it is hoisted out of the mine, is carried up to the top of the breaker and discharged into a hopper, whence it passes downward over bars, through screens and crushers, and is finally discharged into bins at the bottom. The admixed slate is separated partly by special screens, and the slaty coal (bone coal) is picked out by boys as it slides down the chutes, in the more modern breakers water-jigs are used very successfully to separate the slate and coal. The sizes produced are described in the article on Anthracite. The capacity of a coal-breaker is commonly about 1000 tons per day, but some exceed 2000 tons in output. Consult Chance, “Report on Coal-Mining,” Report AC of the Second Geological Survey of Pennsylvania (Harrisburg, 1883).
COALFISH (so named from its color). (1) The pollack (q.v.). (2) A singular and interesting chirid fish (Anoploma fimbriata) of the North Pacific, which is usually slaty-black above and white below, but variable with age and place. It is about 18 inches long, allied to the rock-trout, and called in California beshow, candlefish, and skilfish.
COAL-GAS. See Gas, Illuminating.
COALING SHIP. In modern naval vessels coaling ship has become an operation of importance. Special machinery is provided for handling it, and the men are drilled at coaling expeditiously. Notwithstanding all that can be done in the way of drill and the improvement of appliances, the operation of coaling must take many hours, and in time of war may necessitate a trip to the nearest coaling-station. This loss of time may prove most serious and defeat the plans of a campaign. Means of coaling at sea without leaving station, or while en route to a place, are therefore sought. Several plans have been devised, in the most successful of which a steel hawser runs between the collier and the vessel to be coaled, starting from a high point on the collier's mast. This serves as a stay on which bags, carried by a trolley, pass to and fro, very much after the fashion of a cableway (q.v.).
COAL-MEASURES. See Coal; Carboniferous System.
COAL-OIL. See Petroleum.
COAL-TAR, or Gas-Tar. The thick, black, opaque liquid that comes over and condenses in the pipes when gas is distilled from coal. It is slightly heavier than water, and has a strong, disagreeable odor. Coal-tar is a mixture of many distinct liquid and solid substances, and the separation of the more useful of these constitutes an important branch of manufacturing chemistry. By distilling from wrought-iron stills, the tar is first broken up into five fractions, which are then further subjected to fractional distillation separately: (1) Crude Naphtha or Light Oil is the fraction distilling over before the temperature of the tar has risen to 170° C. This portion contains a number of valuable hydrocarbons, including benzene, toluene, xylene, etc. Another important product obtained from this fraction is the so-called solvent or burning naphtha of commerce, which is largely used for burning in lamps, as a solvent for india-rubber and gutta-percha, and for a variety of other purposes. The benzene obtained from this fraction is also used as a solvent, though most of it is converted into aniline, all of the vast amount of aniline manufactured at present being derived from nitro-
