46 BIBLIOGRAPHY OF NORTH AMERICAN GEOLOGY, 1906-1907. 
Cirkel, Fritz. 
468. Preliminary report on the examination of the iron ore deposits in the 
Ottawa Valley.— Canada, Dept. Interior, Rept. Supt. Mines, 1907, pp. 11-13, 1907. 
469. Graphite, its properties, occurrence, refining, and uses. — Canada, Dept. 
of Mines, Mines Branch, 307 pp., 20 pis., 8 maps, 52 figs., 1907. 
Clapp, C. H. 
470. The clays of North Dakota.— Econ. Geology, vol. 2, no. 0, pp. 551-504, 
1907. 
Economic geology of North Dakota clays. — See Babcock and Clapp, no. 92. 
Clapp, C. H., and Babcock, E. J. 
471. Clay and its properties with special reference to North Dakota clays. — ■ 
North Dakota State Geol. Survey, 4th Bienn. Rept., pp. 9-01, 1906. 
Clapp, Frederick G. 
472. The Nineveh and Gordon oil sands in western Greene County, Pa. — 
U. S. Geol. Survey, Bull. no. 285, pp. 362-30<», 1906. 
Discusses the correlation of the oil sands in this area. 
473. Evidences of several glacial and interglacial stages in northeastern 
New England. — Science, now ser., vol. 24, pp. 499-501, October 19, 1906. 
474. Clay of probable Cretaceous age at Boston, Massachusetts.— Am. Jour. 
Sci., 4th ser., vol. 23, pp. 183-180, March, 1907. 
Describes the occurrence and character of white clay encountered in borings at Boston, 
Massachusetts, which, for reasons stated, is considered as probably Cretaceous in age. 
475. Description of the Amity quadrangle [Pennsylvania]. — U. S. Geol. Sur- 
vey, Geol. Atlas of U. S., folio no. 144, 15 pp., 8 figs., 3 maps, 1907. 
Describes the topography, the occurrence, character, and relations of Carboniferous and 
Devonian strata, and of Pleistocene deposits, the geologic structure and history, and the 
mineral resources, coal, petroleum, and natural gas. 
476. Description of the Rogersville quadrangle [Pennsylvania]. — U. S. Geol. 
Survey, Geol. Atlas of U. S., folio no. 140, 14 pp., 6 figs., 3 maps and columnar 
section sheet, 1907. 
Describes the topography, the occurrence, character, and relations of Carboniferous and 
Devonian strata, and Pleistocene deposits, the geologic structure and history, and the 
mineral resources, chiefly petroleum, natural gas, and coal. 
477. Economic geology of the Amity quadrangle, eastern Washington County, 
Pennsylvania.— U. S. Geol. Survey, Bull. no. 300, 145 pp., 8 pis., 7 figs., 1907. 
Describes the occurrence, character, and relations of Carboniferous strata, the geo- 
logic structure, and the occurrence of mineral resources : petroleum, natural gas, coal, 
and limestone. 
478. Local glaciation in Maine. — Abstract : Science, new ser., vol. 25, p. 390, 
March 8, 1907. 
Oil and gas fields of Greene County, Pennsylvania. — See Stone and Clapp, no. 
2314. 
Clark, W. C. 
479. Zinc in eastern Tennessee. Mines and minerals, vol. 27, no. 9, p. 395, 
April, 1907. 
Clark, William Bullock. 
480. W T hat should appear in the report of a state geologist?— Econ. Geology, 
vol. 1, no. 5, pp. 489-498, 1906, 
