converted into gaseous form before they can be consumed. Natural gas, however, has reached that form, and is in condition to take to itself the amount of oxygen necessary for combustion. The great natural reservoirs require only to be pierced by the drill when the gas may be brought to the surface, where it is at once ready to be used as fuel or to become a direct source of power in the gas-engine. No preparation is necessary for its combustion and no residue is left.

"It is easily distributed in pipes to points of consumption many miles distant, and no known method for the distribution of power equals in economy that of the transportation of a gaseous fuel in pipes.

"The great natural reservoirs of this ideal fuel, so far as known, are found on the north-western flank of the Appalachian mountains, extending from northern- central New York to central Tennessee, and on the summit of the great Cincinnati arch in north-western Ohio and northern Indiana. It is more or less associated with the pools of petroleum found within these areas. These two fields furnish about ninetyseven per cent. of all the natural gas produced in the United States. Outside of these fields there are smaller fields of natural gas in Kansas, Colorado, California, Illinois, Missouri, Texas, and South Dakota."

Natural gas is combustible gas formed naturally in the earth. It is sometimes found issuing through crevices, but is generally obtained by boring. Natural gas has long been used in western China and elsewhere. It was first utilized in New York in 1821, and began, about 1874, to be of importance commercially, especially in the vicinity of Pittsburg.

The area over which natural gas and petroleum are obtained in quantity and the conditions of their occurrence are in most respects essentially the same, but the principal source of the gas in Ohio and Indiana is a formation lower down in the geological series than that furnishing it in Pennsylvania. In the former States the gas comes from the Trenton limestone, a group belonging to the Lower Silurian; in the latter, from the Devonian. The natural gas burned at Pittsburg contains about sixty-seven per cent. of marsh gas, twenty-two per cent. of hydrogen, five per cent. of an ethylene compound, three per cent. of nitrogen, together with a small percentage of carbonic

THE THICK PALL OF SMOKE CAUSED BY USE OF SOFT COAL.

A correlation between natural gas and petroleum is universally admitted, but there is a strange conflict of scientific opinion as to the origin of both of them. Without entering into the arguments that are variously brought forward to prove that natural gas and petroleum are an animal, vegetal, or mineral product, it may here be stated that the bulk of scientific opinion favors the theory of animal origin, and that the following conclusions are in this connection fairly generally accepted:

1. Saurians, fishes, cuttlefishes, coralloid animals, etc., especially have authentically contributed to the formation of petroleum, though soft animals without solid frame, of which no authentic determinable remains are left behind, may also have co-operated. While coal has been formed by the transformation of vegetable substances, petroleum and the allied bitumens originated from animal substances.

2. The nature of the conditions under which petroleum could be formed from animal remains is unknown.

history of which animal remains exist. The archean strata are free from petroleum.

4. Petroleum could accumulate and be preserved in the original deposit only, if during its formation it was shut off from escape.

5. The formation of petroleum has been effected without the co-operation of an uncommonly high temperature; and

6. It has taken place under high pressure, the influence of which on the chemical process is not known.

7. The deposits of petroleum are partially original (primary) and partially secondary. The latter may be or were connected with the former.

So much specifically for petroleum. For natural gas the same materials and similar processes are presupposed. The accumulation of both also took place in the same spaces, frequently in such a manner that the gas occupied the higher and the oil the lower sections of the same rock stratum. No process being known by which petroleum can be formed from natural gas while the separation of the latter from the formereven at the ordinary temperature-is a well-known fact, it is very probable that petroleum is the primary and gas the secondary product.

The recognition of the commercial value of natural gas quickly followed that of petroleum. When the use of petroleum was limited, very primary methods for obtaining it were in vogue. At first the oil collecting on the surface of the water was skimmed off and purified by heating and straining. Later on, shallow pits were dug in which the oil issuing from the lower rock strata collected and was kept for use.

The Namu Indians and the Persians of the Caucasus were in the habit of soaking up the oil with cloths, dipping it out with earthen pots. With the increasing consumption of the oil, the shallow pits were gradually changed to wells (30 to 100 feet deep), from which the oil was raised by hand or animal power. The oldest traces of obtaining oil by mining are found in Japan, where from a very remote period wells have been dug and tunnels have been run into hillsides for oil.

In the United States several different methods for obtaining oil were employed before wells were drilled. In the Ohio oil districts shafts were found, apparently made by the French.

Artesian wells formed the transition to the present deep borings. Although not employed for petroleum and gas alone, their use for these purposes is as old as the primary methods previously mentioned. In China the Jesuit missionaries found artesian wells in full operation. These wells were drilled for brine and natural gas, the latter being frequently accompanied by petroleum. Abbé Huc, in his work on China, describing the methods of drilling wells, says: "The wells are usually from 1,500 to 1,800 feet deep and only 5 or 6 inches in diameter." A heavy rammer, weighing 300 or 400 lbs., was used, worked by a lever and operated by two men. "When the rock is good the work advances at the rate of two feet in twenty-four hours, so that about three years are required to dig a well."

In the United States the first artesian well was drilled in 1809 and furnished, besides a very large volume of gas, a great quantity of oil.

The success which attended the drilling of artesian wells gave, indirectly, rise to the drill. In the summer of 1858 Colonel E. L. Drake attempted to sink a shaft for oil on property of the Seneca Oil Company. Being thwarted by water and quicksands, he hit upon the expedient of driving an iron pipe from the surface to the solid rock, when after four months he was rewarded by "bringing in" the first drilled oil well in history, and making way for the immediate tremendous development of the oil business.

At the present time three drilling systems are used in boring for natural gas or oil. They are the rotatory, the percussive, and the free-fall system. For the rotatory method the

drilling instrument is a screw auger, a common round earth auger, or else a diamond or steel crown drill, to which a continuous supply of water is forced down to keep the crown cool, and which carries off the débris formed by the erosion of the strata by the crown.

The ordinary percussive drill is in the form of a chisel, and is used at the end of an iron or wooden rod. In its simple form it is adaptable only for slight depths.

The free-fall drill is the style in common use, and is suitable for all kinds of drilling. It is swung upward and downward by a walking-beam.

For natural gas, as for petroleum, there is no such thing as positive surface indications of the precious fluid underneath.

history of which animal remains exist. The archean strata are free from petroleum.

4. Petroleum could accumulate and be preserved in the original deposit only, if during its formation it was shut off from escape.

5. The formation of petroleum has been effected without the co-operation of an uncommonly high temperature; and

6. It has taken place under high pressure, the influence of which on the chemical process is not known.

7. The deposits of petroleum are partially original (primary) and partially secondary. The latter may be or were connected with the former.

So much specifically for petroleum. For natural gas the same materials and similar processes are presupposed. The accumulation of both also took place in the same spaces, frequently in such a manner that the gas occupied the higher and the oil the lower sections of the same rock stratum. No process being known by which petroleum can be formed from natural gas while the separation of the latter from the formereven at the ordinary temperature is a well-known fact, it is very probable that petroleum is the primary and gas the secondary product.

The recognition of the commercial value of natural gas quickly followed that of petroleum. When the use of petroleum was limited, very primary methods for obtaining it were in vogue. At first the oil collecting on the surface of the water was skimmed off and purified by heating and straining. Later on, shallow pits were dug in which the oil issuing from the lower rock strata collected and was kept for use.

The Namu Indians and the Persians of the Caucasus were in the habit of soaking up the oil with cloths, dipping it out with earthen pots. With the increasing consumption of the oil, the shallow pits were gradually changed to wells (30 to 100 feet deep), from which the oil was raised by hand or animal power.

The oldest traces of obtaining oil by mining are found in Japan, where from a very remote period wells have been dug and tunnels have been run into hillsides for oil.

In the United States several different methods for obtaining oil were employed before wells were drilled. In the Ohio oil districts shafts were found, apparently made by the French.