MARSHFIELD, a city of Wood county, Wisconsin, about 165 m. N.W. of Milwaukee. Pop. (1890), 3450; (1900), 5240, of whom 1161 were foreign-born; (1905) 6036; (1910) 5783. It is served by the Chicago & North-Western, the Chicago, St Paul, Minneapolis & Omaha, and the Minneapolis, St Paul & Sault Ste Marie railways. It contains the mother-house of the Sisters of the Sorrowful Mother. Lumbering is the most important industry, and there are various manufactures. The city is situated in a clover region, in which dairying is important, and Guernsey and Holstein-Friesland cattle are raised. The municipality owns and operates the waterworks and the electric-lighting plant. The site of Marshfield was part of a tract granted by the Federal government to the Fox River Improvement Company, organized to construct a waterway between the Mississippi river and Green Bay, and among the original owners of the town site were Samuel Marsh of Massachusetts (in whose honour the place was named) and Horatio Seymour, Ezra Cornell, Erastus Corning, and William A. Butler of New York. Marshfield was settled about 1870, and was first chartered as a city in 1883.
MARSH GAS (methane), CH4, the first member of the series of paraffin hydrocarbons. It occurs as a constituent of the "fire-damp" of coal-mines, in the gases evolved from volcanoes, and in the gases which arise in marshy districts (due to the decomposition of vegetable matter under the surface of water). It is found associated with petroleum and also in human intestinal gases. It is a product of the destructive distillation of complex organic matter (wood, coal, bituminous shale, &c.), forming in this way from 30 to 40% of ordinary illuminating gas. It may be synthetically obtained by passing a mixture of the vapour of carbon bisulphide with sulphuretted hydrogen over red-hot copper (M. Berthelot, _Comptes rendus_, 1856, 43, p. 236), CS2 + 2H2S + 8Cu = 4Cu2S + CH4; by passing a mixture of hydrogen and carbon monoxide over reduced nickel at 200-250° C., or hydrogen and carbon dioxide at 230-300° C. (P. Sabatier and J. B. Senderens, _Comptes rendus_, 1902, 134, pp. 514, 689); by the decomposition of aluminium carbide with water [H. Moissan, _Bull. Soc. Chim._, 1894, (3) 11, p. 1012]; and by heating phosphonium iodide with carbon bisulphide in a sealed tube to 120-140° C. (H. Jahn, _Ber._, 1880, 13, p. 127). It is also obtained by the reduction of many methyl compounds with nascent hydrogen; thus methyl iodide dissolved in methyl alcohol readily yields methane when acted on by the zinc-copper couple (J. H. Gladstone and A. Tribe, _Jour. Chem. Soc._, 1884, 45, p. 156) or by the aluminium-mercury couple. It may be obtained in an indirect manner from methyl iodide by conversion of this compound into zinc methyl, or into magnesium methyl iodide (formed by the action of magnesium on methyl iodide dissolved in anhydrous ether), and decomposing these latter substances with water (E. Frankland, 1856; V. Grignard, 1900),