MINING AND USES. The methods used for drill ing gas-wells are the same as those employed for sinking oil-wells (q.v.). When the gas is first struck the pressure has in rare cases been sufficiently great to blow out the string of drill ing tools weighing over 1000 pounds. As soon as practicable the well is capped, and the supply is piped to the site of consumption or to storage tanks. As the gas is often required for use at sonic distance from the well, the construction of pipe-lines has become an important feature of the natural-gas industry. With high rock pres sure the gas may reach the market unaided, but with low pressure it is necessary to locate pump ing stations at different points along the pipe. The pipes used vary in diameter from two inches to three feet, and are made of wrought iron or steel. One of the first lines was that laid in 1882 from Wilcox to Colegrove, Pa., a distance of 20 miles. Later, with the depletion of the gas-fields around Pittsburg, it became necessary to pipe the gas for that city from greater distances, and at the present time some of it is being piped from Doddridge County, W. Va., a distance of over 100 miles. The pipe-lines from Wetzel County, W. Va., to Akron and Canton, Ohio, are over 150 miles long. So extensive has been the construc tion of pipe-lines that at the close of 1901 there were 22,000 miles of them in operation.
When first used the price of natural gas was low and no attempt was made to measure it, as it appeared to be widely distributed and to exist in inexlmustible quantities, but the giving out of some of the districts and the rapid fall in rock pressure led to the use of meters and a rise in the value of the gas. On account of its clean liness and excellent calorific power, natural gas has become an important source of light, heat, and power in many States, so that in 1901 it was used in thirteen States, by 1545 companies, representing a total of 5742 manufacturing estab lishments, including iron-mills, steel-works, glass factories, brick-factories, and lead and zinc smelt ers. In addition to this it was used in many hundred private houses for heating or illumina tion.
Natural gas has a high calorific power, 1000 cubic feet having the power to evaporate 1000 pounds of water at 212° F. About 50 candle power can be obtained by the consumption of 21/2 cubic feet per hour. In fuel value, 12 cubic feet of natural gas is equal to about one pound of coal. Its illuminating power is low, unless used with some patent burner, such as the Welsbach light. The production of the United States in 1901 was valued at $27,067,500, exclusive of the amount piped in from Canada.