REVIEWS 829 within ten miles of the only purely volcanic rock in New York, Vermont, or western Massachusetts support this theory. The carbonated waters take on calcium and magnesium carbonates from the Little Falls dolomite on their upward journey. This conclusion accords with the marked tendency of economic geologists in the last decade to lay greater stress on the importance of magmatic emissions. W. B. W. Coal Resources of District No. I (Longwall). By GILBERT H. CADY. Illinois Coal Mining

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... vestigations, Bulletin No. io, Urbana, 1915. Pp. 149, pls. 9, figs. 27, tables 24. The Longwall District, comprising Bureau, Putnam, Marshall, La Salle, and Grundy counties and the adjacent parts of Livingston, Kankakee, and Will counties, an area of about 1,700 square miles, contains nearly six billion tons of available coal and is one of the foremost districts of the state in economic importance. This bulletin is concerned with the stratigraphic and structural geology of the region, the economic geology of the coals and accompanying strata, and with the working data developed. The important beds are Nos. 2, 5, 6, and 7, of which No. 2 has been extensively mined. These coals have been studied in a large number of mines. The character of the coal beds and their general structure have been worked out in detail, and many sections through the productive coal measures have been tabulated. In addition to its value in connection with the coal resources, the bulletin is of general interest in that it contains an outline of the geology of the La Salle anticline, including Starved Rock, Deer Park, and the surrounding country.