Natural Gas. Natural gas is an ideal domestic fuel and an almost equally ideal industrial fuel. It is a large item in interstate but not in international trade. About one-fourth of the natural gas consumed in the United States is used for generating power, and its use affects international industry and commerce, for it supplements the supply of coal and oil. As it saves man power, is especially adapted to certain industrial processes and is cheap, natural gas is used as fuel in many glass works, cement plants, brickyards, factories and metallurgical plants. It is also used in large quantities as raw material in making carbon black, 30 per cent of the natural gas consumed industrially in West Virginia in 1917 having been used in the carbon black industry. Some natural gas is valuable because of its content of gasoline, and the extraction of gasoline from natural gas is now an industry of increasing magnitude. Some of the gasoline thus obtained is so light that it must be blended with naphthas and other distillates obtained from crude oil before it can be used as a motor fuel. A recently developed process is that of extracting the gas helium from natural gas. It is used in balloons as a non-inflammable substitute for hydrogen. Natural gas is now used by about 16,500 industrial consumers of whom more than 10,000 employ it for generating power and by about 2,500,000 domestic consumers. The field operations undertaken to exploit natural gas have been accompanied by enormous waste, which will hasten the exhaustion of this fuel. Character and Occurrence-Pure natural gas is odorless and colorless, burns with a luminous flame and is highly explosive when mixed with air. Its chief constituent is marsh gas, or methane, a member of the paraffin series. Besides methane, it may contain ethane, a closely related gas and varying amounts of ethylene or olefiant gas, carbon monoxide, carbon dioxide and nitrogen as well as a little oxygen and helium. Natural gas is classified as either "wet" or "dry" according to its content of gasoline. Wet gas is commonly associated with oil in oil fields and is generally obtained from the same sand or formation that yields the oil or even from the same well. It contains not only ethane, propane, butane and pentane, the lighter members of the methane series, which predominate in the dry gas, but some heavier hydrocarbons. Dry gas contains chiefly methane or marsh gas, the lightest known hydrocarbon, which has a specific gravity of 0.559. It is usually not associated with oil in the sand and is generally under high pressure. The close association of oil and gas in both occurrence and origin makes it difficult to consider the two resources separately. Gas invariably accompanies oil wherever the conditions are favorable to its accumulation but it is also found in places far removed from oil fields. Many of the natural gas fields coincide areally with oil fields and the production of oil and that of natural gas are closely related. The gas being lighter usually accumulates in the upper parts of the oil and gas bearing deposits. The accumulation of natural gas is governed by features of geologic structure similar to those that govern the accumulation of oil and the origin of natural gas is accounted for by the same theories that account for the origin of oil. Natural gas is found in rocks that range in geologic age from Cambrian to Recent, but most of the world's supply of natural gas is derived from beds of Devonian, Carboniferous and Tertiary age. Geographic Distribution-The chief natural gas fields of the United States are the Appalachian field, comprising parts of the States of West Virginia, Pennsylvania, New York, Ohio, Kentucky and Tennessee; the Mid-Continent field, including parts of Kansas and Oklahoma; and isolated fields in the states of Louisiana, Texas, Arkansas, California, Illinois and Indiana. Gas is also found in small quantities in Wyoming, Washington, Colorado, Oregon, South Dakota, North Dakota, Montana, Idaho, Iowa, Michigan, Missouri, New Mexico, Utah and Alabama. In foreign countries, natural gas is found in considerable quantities in the provinces of Ontario, Alberta and New Brunswick in _Canada and in Great Britain, Italy, Rumania, Galicia, Hungary, Russia, Persia, India, Japan, Mexico, Peru and Argentina. Undoubtedly as the search for petroleum is continued, productive gas fields will be discovered in foreign countries even in countries where natural gas is not now supposed to be present in great quantities. Production-The commercial production of natural gas is restricted almost wholly to the United States, the available statistics showing that about 95 per cent of the world's output is produced in this country. Canada stands second in rank. The United States is likely to lose this remarkable predominance, for she has already apparently passed her maximum production. (See U. S. Geol. Survey.) The table on page 395 shows the production of the principal natural gas producing countries in the world in 1913 and 1917: Typical Composition of Commercial Gases. Me Coal gas, Germany. 8.88 Lignite gas Wood distillation gas. thane Ethyl- Hydro- Carbon Carbon Nitro- Oxy- B.T.U. gen per CO: N2 cu. ft. 3.01 2.15 0.45 2.05 0.65 700 11.51 5.49 1.76 500 perature. Cannel coal gas, high temperature. 45.50 Natural gas. 0.00 0.00 Pressure still gas. 4.00 2.00 1.50 350 0.00 970 0.22 Oil gas.. 57.70 38.10 3.40 0.50 Producer gas.. 1.20 12.00 27.00 2.50 57.30 154 Blast furnace gas. *Still gases from lub stills |