To prevent coal-dust explosions
DRILLING IN COAL FOR BLASTING
“Anthracite” is the hardest of coals. It was formed from bituminous coal under the crushing pressure due to the upheaval of mountains or by the intense heat of adjacent molten rocks. Most American anthracite is mined in eastern Pennsylvania. The largest deposits in the world are found in China. Anthracite burns slowly, with little smoke. It is well adapted for domestic use on account of its cleanness, but is not an economical fuel for steam-raising or general manufacturing.
Press Illustrating Service
MODERN ELECTRIC LOCOMOTIVE
Used for hauling coal from the mines
“Semi-anthracite” also ranks as a hard coal, though it is less hard than anthracite. Very little is mined in this country, and it is generally sold as anthracite.
“Semi-bituminous” coal is a softer coal, which, when properly burned, gives off but little smoke. The best semi-bituminous coal ranks highest among the coals in heating value. It is the most valuable fuel for manufacturing purposes; also for steamships, as it requires less bunker space per unit of heat than any other coal.