Coal

a well known combustible mineral, used as a fuel. It varies in color from brown to black. It is brittle, it cannot be melted, and is not subject to decay. It is composed essentially of carbon, but contains from five to six per cent of earthy matter. This is the part that is left behind in ash. Sulphur is found in almost all coal.

Coal is supposed to be derived from a vast growth of vegetation that accumulated in oceanic swamps, chiefly in a former era of rain and heat known as the carboniferous age. An intensely tropical climate caused a rank and rapid growth of tree-like rushes, now extinct, whose gigantic trunks, mingled with ferns and other plants, covered tropical areas to a great depth. A sinking of the earth's crust, followed by a deposit of soil, brought down by such floods as we have no conception of today, buried the vegetable matter of the old swamps beneath a mass of mud, a mile deep perhaps. Intense heat from the interior of the earth and pressure from above turned the plants themselves into a layer or vein of coal. Sometimes a new swamp of rank vegetation appeared above the old one; or in this way several layers of coal may have been formed, one above the other, with strata of stone intervening.

The nearest approach to coal formation nowadays are the peat beds in which vegetable fiber is accumulating from year to year. Should any considerable thickness of peat ever be covered with soil and subjected to great pressure and heat, we might expect it to become a coal measure.

Lignite is a form of coal that is but imperfectly converted. Traces of woody growth, as in the lignites of North Dakota and Texas, are still visible. Attempts to grind these coals and compress them into more solid bricks for general consumption have been made with entire success, save as to expense.

Hard coal, or anthracite, is coal that has been buried beneath great masses of earth, and hence has been subjected to such pressure and heat as to drive off the greatest possible percentage of matter that can be converted into vapors or gases, and leave a high percentage of pure carbon. The great hard coal bed of the world is that of Pennsylvania. It underlies an area 125 miles long by 35 miles wide. During the past fifty years 4,000,000;000 tons have been taken out. It is estimated that 15,000,000,000 tons remain. It will last a hundred years at the present rate of mining. About forty per cent is wasted needlessly in dust and in fragments left in the debris.

Soft coal or bituminous coal contains gaseous materials that have not been driven out. All grades of coal from soft to hard are to be found. The softer the coal, the more it swells in burning, and the denser the black smoke it gives off. The more recently coal has been formed, the softer it is likely to be.

Coal was not burned in the ancient world. We hear of the first in England about 852. American coal was mentioned by Father Hennepin who found it in the bluffs of the Illinois River near La Salle in 1673-80. It is said that the settlers of Pennsylvania did not know any use to which they could put the black stone that cropped out of the cliffs along their streams. Even after they had learned that it could be burned, and how to burn it, it was a long time before anyone thought of selling it. Each farmer drove up to a bank anywhere and shoveled in as much of the stuff as he cared to haul away. It was not until a way of getting it to Philadelphia and New York was opened up that coal began to have a money value.

At the present time the coal of the United States is spoken of as found in certain areas or districts, as the Rhode Island district; the Appalachian, extending from Pennsylvania to Alabama; the Michigan; the Illinois, including part of Indiana and Kentucky; an ill defined prairie district including localities from North Dakota to Texas; the Rocky Mountain area; and the states of the Pacific coast. Many of our coals, especially the lignites, belong to an age subsequent to that known as the carboniferous.

Although increasing quantities are produced in Nova Scotia, Vancouver Island, China, India, Australia, New Zealand, Orange Free State, and Brazil, Europe and the United States now produce practically all the coal of the world. Large fields in Alaska and adjacent parts of Canada may be expected to add to the world's output. More than half of the world's miners are engaged in mining coal. The world's production of coal in 1904 is given as follows:

Total, partly estim'd 471,800 866,104,538

An important use of coal is that for heating. Locomotives and stationary steam engines in manufactories requiring steam power consume enormous quantities. Illuminating gas is made from coal. Electric lights are in circuit with the power house in which electricity is generated, usually by burning coal. The smelting of iron is accomplished by means of coal. The various forms of iron, wrought, cast, and steel, are obtained from pig iron by the aid of coal.

Of these four uses, heating, lighting, smelting, and producing power, the last named is the most conspicuous. If coal were to give out suddenly, nine-tenths of the world's industries would stop until new methods of transportation and manufacturing could be devised. The production of iron would cease. Cities would be plunged into darkness. Trains would come to a standstill. The wheels of factories would stop. Surplus crops would be worthless--no way of carrying them. People would starve for want of a way to get food to them. Northern people would perish for want of a way to get fuel to them. Wood, water power, and oil would help us out, and doubtless a substitute for coal would be found; but a large part of the earth's surface would be abandoned temporarily, and civilization would be set back by the disaster. At the present rate of waste and consumption the known supply will last about 450 years. No doubt coal will give out; but in the meantime the inventive genius of mankind will have devised means of harnessing the wind, waves, and sunlight to supply heat and do our work.

A German authority writing in 1908 says the world has coal enough to last at least 2,000 years. His estimate in tons is as follows:

See Steam; Coke; Carbon; Iron; Mining; Charcoal; Belgium; Pennsylvania; Alabama, etc.