There is reason to believe that this material is the product of distillation of organic matter in the earth. It is found in porous rock, usually coarse sand, at depths varying from three hundred to two thousand feet. When the rock above the sand containing oil is tight, the gas is often retained, which by its expansion presses upon the oil and forces it to the surface through the pipes put down for this purpose. This produces a flowing well. When the gas has escaped a pump is necessary.
The most useful hydro-carbon now employed is coal. Its use was first introduced in the latter part of the twelfth century, and as late as the thirteenth century petitions were made by residents of London demanding its exclusion, on account of its injurious effect on the health. But now, Great Britain mines annually more than one hundred million tons of coal. Its uses are manifold. By it England has multiplied her power a thousand fold. It is almost always employed in generating steam, and the aggregate steam power of England is equal to the productive laboring force of four hundred millions of men, or “twice the power of the adult working population of the globe.” Most countries know its value.
POURING CARBON DI-OXIDE FROM ONE VESSEL INTO ANOTHER TO EXTINGUISH FLAME.[13]
Coal is the key that unlocks for us the treasures of the iron ore. It seizes upon the oxygen in the ore, and liberates the pure metal. By a wonderful provision they often exist in the same mountain, side by side. I have seen in Pennsylvania, running out of the same tunnel in the hills, car loads of coal and iron ore.
Among the many advantages possessed by our own country is our immense store of this precious hydro-carbon. With an area of 300,000,000 miles of territory, we have more than 200,000 square miles of known coal producing area, or one in fifteen.
Great Britain has one-half of the coal fields of all Europe, but even she has but one square mile of coal to twenty square miles of territory. Beside, our coal seams are of great thickness, and lie comparatively near the surface. In the far West, vast fields of lignite[14] have been discovered, so that there seems no prospect of our exhausting our fuel supply for ages to come.
The diamond is crystallized carbon, and can be burned, though one would hardly care to be warmed by so costly a fire.
Cleopatra, in a freak of extravagance, dissolved a wonderful pearl, but who could think of the wise queen of England using in so wasteful a manner her Kohinoor.[15] Six of the great diamonds of the world are called, by way of eminence, “The Paragons,” and a romantic interest has been attached to this form of carbon among all nations. In point of fact, however, the black diamonds of the coal pit are more interesting, and of far greater value to mankind than these glittering gems from Golconda,[16] Brazil and the Dark Continent.[17]