N.trun.st. Gas l'IPE LINES are often similar to the wrought iron lines described above. but they are also composed of riveted steel plates, and even of east iron. Another variation from the oil pipe lines is the size of the gas mains, 16 to 24 inches or niore in diameter, instead of 4 to S inches. It is said that the Chinese used bamboo pipes for natural gas and that is wooden main 20 miles long was laid from a well at West Brookfield, N. Y., to Rochester as early as 1865, or thereabouts. The general utilization of nat ural gas in the United Stales, and also the con struction of gas pipe lines, followed the develop ment of the petroleum oil industry. In 1872 gas was piped to Titusville, Pa., through.a 2-inch and a :31i-ineh iron pipe line, long. In 1876 a (1-inch main, 17 miles long, was laid to Sharpshurg, front the Harvey well, in ler County. The feeders to the pipe lines are 2 to inches in diameter. The nut in lines are 40 to 50 miles in length. The pressures in vari ous fields originally ran from 300 to 1000 pounds per square inch. but of late they have fallen off,
year by year, until in many cases they are only a small fraction of the initial. This has neces sitated pumping the gas. The first pumps were installed by the People's Company, of Pittsburg, Pa., in 1890. Now nearly every company sup plying gas to the larger cities is compelled to pump in winter. The pumping is generally ef fected by some standard form of air compressor, driven by compound or triple expansion steam engines. The gas itself is generally used as fuel, but sometimes coal is used in order to husband the diminishing gas supply. About 1900 some large gas engines, one of 1000 horse-power, were installed to operate the gas compressors.
Where natural gas reaches a city under high pressure automatic pressure reducers are em ployed to reduce the gas to a uniform pressure of 10 to 50 pounds before it enters the city dis tributing mains. On each consumer's service pipe another reducing and regulating valve maintains a pressure of about one-half pound.