Nature, it is now known, has her own gas works, on an immense scale. Thirty-five years ago the village of Fredonia, N. Y., was partially lighted with gas, and the supply is still unexhausted. Indeed, of late, many private individuals have sunk pipes two or three hundred feet, and thus supplied their homes with gas for illuminating, heating, and cooking purposes. In Butler and McKean counties, Pennsylvania, the production of these gas wells is enormous. Many have been burning day and night for years, while others have been utilized for heating and lighting towns and cities. Gas is now extensively used in rolling mills for smelting iron. Petroleum, or rock oil, which is usually associated with this natural gas, has now become of immense value to this and other lands. It is one of the chief articles of export from this country, ranking perhaps as fourth. Wells have recently been struck in Pennsylvania that flowed 5,000 and 6,000 barrels per day. [Illustration: SODIUM BURNING ON HOT WATER.[12]] 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. [Illustration: 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.