The annual production of coal throughout the entire world is roughly estimated at about two hundred millions of tons. More than half of this coal is produced in Great Britain. About twenty millions of tons are mined in North America, and the rest mainly in Belgium, France, and Prussia. The production of other countries is comparatively insignificant. Coal is the most valuable mineral substance known. The amount of coal taken from the earth every year is double the value of all the gold, silver, and diamonds annually produced. In the great World’s Fair of London in 1851, when the famous Kohinoor diamond attracted thousands of curious spectators, there was one day a lump of coal placed near the case containing the Kohinoor. The lump bore this brief label: “This is the _real_ Kohinoor diamond.” America to-day is of far less importance as a coal producer than Great Britain, but she is destined to become eventually the great coal producer of the world. At the present time there is much anxiety in England about the exhaustion in a few hundred years of the coal fields in the British Isles. The United Kingdom contains nine thousand square miles of coal fields; France, Belgium, Spain, Prussia, and other German states, together, about two thousand seven hundred square miles of coal fields; other countries, not including America, contain about twenty-nine thousand, while North America, including the British colonies, contains about one hundred and eighty thousand square miles of coal fields. It will thus be seen that the area of the North American coal fields is four times as great as all those of the other countries of the globe. Of this immense extent of coal deposits, a very small portion has yet been touched, and consequently for thousands of years to come our country can supply the world. [Sidenote: HOW COAL WAS FORMED.] Coal was formed at a very remote geological period. Scientific men differ as to the exact age of this substance. Their differences are trivial, however, being only a few millions of years; but they all agree that at the time coal was formed there were wide jungles and swamps that covered a large portion of the earth’s surface. The atmosphere was very moist, and probably contained a much larger proportion of carbonic acid than at the present time. This gas is one which especially promotes the growth of plants. It is, and was, probably unfavorable to the existence of animal life; and it has been suggested that the gradual withdrawal of the carbonic acid by the growth of vegetation of that period slowly purified the atmosphere, and brought it to the condition in which we now find it. The earth at that time was not fitted for the habitation of man. If man had existed at that period, he would have needed fins in the place of hands and feet, and would have required lungs like those of fishes, instead of those which he now possesses. There was an abundant population of reptiles and of insects, and there was a liberal supply of fishes.