Before the days of the railway coal was shipped mostly by water in rough boats called “arks,” which floated down the rivers to the seaboard towns. As it was impossible to return against the current, the ark was sold with the coal at its destination. A great many arks were wrecked in transit, and the whole process of transportation was a costly one. Only with the introduction of steamboats, canals and railways, did the coal industry assume serious proportions. The production of coal in America has grown at an amazing rate. In the year 1868 Great Britain produced 3.6 times as much coal as the United States, and the output was also exceeded by that of Germany. In 1899, the United States took the lead. At the present time, with an estimated production for the year 1917 of 643,600,000 tons, the United States is producing nearly half of all the coal mined in the world. Great Britain ranks second, closely followed by Germany. _How Coal is Mined_ A relatively small amount of coal is quarried near the surface of the ground from open pits. The overlying soil is removed by steam-shovels, and the coal is then blasted out and shoveled into cars. Most coal is mined underground. Access to the coal-beds is obtained either by sinking a vertical “shaft” or by driving a tunnel, according to the location of the beds. A tunnel driven at a steep angle is called a “slope.” A horizontal tunnel leading into a coal-seam is called a “drift.” In this country few coal mines are more than 300 or 400 feet below the surface, and the deepest is about 1,600 feet. Much deeper mines are found in Europe, especially in Belgium. [Illustration: Press Illustrating Service ROTARY DUMP IN A TIPPLE Showing a coal car half turned over in order to dump contents] [Illustration: Courtesy of “Coal Age” SPIRALIZING MACHINES which, by rotating motion, separate the coal from slate] [Illustration: Courtesy of U. S. Bureau of Mines MODERN HEADFRAME, BINS AND TRESTLE Of fireproof construction. Anthracite coal mine] American mine shafts are generally rectangular and are divided into two or more compartments. Where a shaft passes through water-bearing strata it must be provided with a tight lining, or “tubbing,” to prevent the mine from being flooded. All water that enters the mine collects in an excavation, or “sump,” at the bottom of the shaft, and must be pumped to the surface.