apprehension. That natural gas will explode under certain conditions, and when mixed with proper proportions of atmospheric air, is certain. It would be of no value at all if it did not have that property. Gas made from coal containing more free hydrogen, ignites at a lower temperature even than well-gas. In a mixture of atmospheric air and gas, a smaller proportion of well- than of coal-gas makes an explosive mixture; in one case, in the other. The danger, however, from the use of wellgas is enhanced considerably from the fact, that it is inodorous (or nearly so); while coal-gas is offensive and its presence, even in very small quantity, is instantly detected. It has been proposed to obviate or lessen the danger by the admixture of some odorous vapors by which its presence in a room might be instantly detected. The following table is taken from the report of the Western Engineers' Society already mentioned:

Table showing comparative Inflammability of Natural Gas and

That accidents should have occurred through haste, inexperience, and, perhaps, the negligence of those engaged in laying pipes to conduct the gas, is not to be wondered at; such work should be done under strict municipal surveillance and regulations. Whatever may be said respecting the right, under existing laws of natural-gas companies to place their pipes in the city streets, such right surely cannot debar any city or corporate community from enacting the strictest regulations to insure the safety of its citizens.

NATURAL GAS AT PITTSBURGH.

The city of Pittsburgh, Pa., is, at the present time, the theatre of some very extensive experiments in the use of this natural gas as a fuel in nearly all the various manufactures of iron, steel, glass, and chemical products. This city appears to have the advantage of being able to tap three or four prolific gas belts or fields. Mr. William Metcalf, C. E., of this city, says: "An observer standing on a hill-top in Allegheny Township, Westmoreland County, say about three miles southeast of the confluence of the Allegheny and Kiskiminetas Rivers, can see on a dark night on the northwestern horizon the reflection of the lights from the Butler County wells; to the north the lights from the wells in the direction of Kittanning; to the northeast the Leechburg and Apollo wells; to the southeast the Murraysville wells, and to the southwest the lights of the Tarentum wells. Off in Washington County and

down towards Steubenville, there are other wells, while at Hulton, in Pittsburgh, in the east end, at Soho, at Brownstown, at Sligo, and in Bayardstown, there are wells upon wells, "roarers" and "gushers." These wells are all on the same straight forty-five degree line, northeast and southwest. Some of these wells give out their gas at an enormous pressure. A gauge on a six-inch pipe situated some miles from the wells, registered, November 18, 1884, 120 pounds to the square inch, and the noise of the rushing gas indicated that the gauge was about right."

Professor J. Lawrence Smith describes graphically two prolific wells known under the names of "the Burns" and the "Delameter." These are separated by at least half a mile, and are located in Butler County, seven miles northeast of Butler and about fifteen miles from the Harvey wells, of which the gas is conducted to Pittsburgh. The two wells are located about thirty miles, measured in a straight line, from Pittsburgh. Their depth is about 1600 feet down to the fourth sand stratum so well known, at least by name, to those engaged in petroleum production. The Burns well it is believed has never yielded oil, but the Delameter, first carried to the third sand layer, was a petroleum well at 1600 feet; sunk afterwards to the fourth stratum, it gave gas at such a pressure that the tools of about 1760 pounds weight might be withdrawn by hand. Each well is 52 inches in diameter.

The Delameter well is the more remarkable. It produces nearly double the quantity of gas of the Burns, and furnishes light and fuel to the entire neighborhood, includ

ing the village of Saint Joe. It is situated in a valley surrounded by high mountains, which reflect and concentrate the light of the ignited gas. Many conduits start from the well: one leads the gas directly to the cylinder of a powerful motor, which, by its pressure alone, acquires a prodigious velocity, and if the gas at the exhaust of this be lit, an immense flame is produced. Another pipe feeds a second flame capable of reducing as much iron ore as half the furnaces in Pittsburgh. At 64 feet distant is the principal escape orifice of the well. From a tube 3 inches in diameter, a column of fire 40 feet high shoots forth with a roar that fairly makes the hills tremble. Over a radius of 50 feet around the earth is scorched, but farther away the vegetation is abundant and as vigorous as in the tropics, and appears to enjoy a perpetual summer. During a calm. night, the noise can be heard at a distance of 15 miles. At 4 miles, the sound resembles that of a railroad train crossing a bridge near at hand, and, finally, as the escape orifice itself is reached, the roar is like that of a thousand locomotives blowing off steam together. At the distance of an eighth of a mile, the sound is like a cannonade. The human voice is hardly able to make itself heard, and the flame seems to leap into the air, at times, to the height of 70 feet, resembling a burning steeple. In winter, even when the hills are covered with snow, for fully ten acres about the flame the grass is green and flourishing. Its illuminating power is 7 candles, coal gas being nearly 16. At the well, in a tube of 52 inches, the pressure is about 100 pounds per square inch, and in a tube of 2 inches, in which

the gas is led to Freeport, 15 miles from the well, the pressure is 125 pounds.

The ascending velocity is in round numbers 1700 feet per second, and if this be multiplied by the area of the tube 24.7 square inches, a yield of 289 cubic feet per second, or 17,340 cubic feet per minute, or about one million cubic feet per hour is determined. The quantity of gas furnished daily is thus 1408 tons. Taking into consideration that for the use of furnaces, the combustion is much more complete than that of bituminous coal, and that the effective heat produced is 25 per cent. greater, the yield of the well in combustible material is estimated at about four million pounds daily.

For more than fifty years Pittsburgh has been called the Smoky City. The extensive and apparently inexhaustible beds of coal and iron in the immediate vicinity, have attracted large capital, to be invested either in the manufacture of iron, the production of coal, or in some of the varied forms of industry dependent upon, or associated with, these interests. Hundreds of tall chimneys belched forth continually huge volumes of black sulphurous smoke, tinging every building with its sooty hue. Although the introduction of the natural gas is quite recent, the change wrought in this respect through its instrumentality is remarkable. A recent letter informs us that within a single year, great strides have been taken here in the natural gas industry. In this city alone not less than $6,000,000 are invested in practically applying the gas; add to this its introduction as fuel in surrounding towns and the