Most coal mines have been discovered and opened in this way; but when the coal is concealed beneath the soil, and nothing is observed on the surface, it is discovered by chance, or by geological indications. At the present day many coal mines are discovered by means of railway cuttings, or in sinking wells. Other mines are discovered in this way. Some twenty years ago, while a railway was constructing in Vermont, the workmen came upon a bed of marble, and it was found to be quite extensive. Speculators bought the land in the vicinity, and thus the Vermont marble quarry came into existence. In 1813 a well was sunk at La Sarthe, in France. Amongst the rubbish a black earth was noticed, which was sent to a provincial debating society at Le Mans. An extraordinary meeting of the society was called, and somebody suggested that this black earth might be coal. It was immediately tried in the stove in the room where the meeting was held, and it was found that the earth burned readily. An investigation followed. Careful examinations were made, and valuable coal mines were opened in the vicinity. Some of the mines in the United States have been discovered in places where burrowing animals had thrown up the earth. Decomposed coal retains its original blackness; in several instances where it was found in the earth thus thrown up, careful observations were made, and work was immediately begun in search of coal. Some valuable mines have been opened in this way. Many of the coal mines in France and Belgium, and also in other countries, have been found in consequence of the explorations of geologists. In the year 1716 a very skilful coal miner in Belgium made a series of explorations, and discovered very valuable mines. Under his direction they were explored for several years, but the works were at length abandoned, in consequence of the accumulation of water. In all parts of the world miners have always found great difficulty in proceeding in consequence of the interruptions caused by water, and until the steam engine was invented there was an absence of sufficient power for its removal. [Illustration: ENTRANCE TO A COAL MINE.] [Illustration: DOWN IN A COAL MINE.] [Sidenote: INVENTING THE STEAM ENGINE.] In the eighteenth century deep pits in the Newcastle coal fields were filled with water, and it was necessary to drain these pits before the coal could be taken out. The ordinary pump was not sufficient for the purpose, and a more powerful engine became necessary. Inventions seem to come at a time when they are most needed. When the necessity for a powerful pump was greatest, the steam engine was invented. Savery, Newcomen, and Watt succeeded each other. Captain Savery constructed one of his “fire engines” to lift water from one of the Cornish mines; but the power of the engine was not great, and the quantity of water raised was exceedingly small.