40 BIBLIOGRAPHY OF NORTH AMERICAN GEOLOGY, 1906-1907. 
Calkins, Frank Cathcart. 
Description of the Snoqualmie quadrangle. — See Smith and Calkins, no. 1156. 
Calvin, Samuel. 
The Aftonian gravels and their relations to the drift sheets in the region 
about Afton Junction and Thayer [Iowa]. — Davenport Acad. Sci., Proc, vol. 
10, pp. 18-31, 7 pis., 1907. [As separate, 1905. See U. S. Geol. Survey, Bull. 
301, p. 56]. 
387. Notes on the geological section of Iowa. — Jour. Geology, vol. 14, no. 
7, pp. 571-578, 1906; Iowa Geol. Survey, vol. 17, pp. 192-200, 1907. 
Describes briefly the occurrence, character, relations, and nomenclature of the forma- 
tions comprised in the geological scale of Iowa. 
388. Geology of Winneshiek County [Iowa]. — Iowa Geol. Survey, vol. 16, 
pp. 37-146, 18 figs., 2 geol. maps, 1906. 
Describes the topographic features and drainage, the stratigraphy, including Cambrian, 
Ordovician, Silurian, and Devonian strata and glacial deposits, and the economic products. 
389. Some features of the channel of the Mississippi River between Lansing 
and Dubuque, and their probable history. — Iowa Acad. Sci., Proc, vol. 14, 
pp. 213-220, 7 figs., 1907. 
Discusses drainage changes in Iowa and the Mississippi Valley. 
390. Fifteenth annual report of the state geologist. — Iowa Geol. Survey, vol. 
17, pp. 1-6, 2 pis.. 1907. 
Administrative report. 
Campbell, Donald F. 
391. The iron ore of Shasta County, California. — Min. and Sci. Press, vol. 
93, p. 603, 1 fig., Nov. 17, 1906. 
392. The copper of Shasta County, California. — Min. and Sci. Press, vol. 94, 
pp. 28-30, 55-58, 4 figs., January 5, 1907. 
Campbell, Marius R. 
The classification of coals. — Am. Inst. Min. Eng., Trans., vol. 36, pp. 324-340, 
1906 (Bi-Mo. Bull. no. 5, pp. 1033-1049, 1905).— See Campbell, 21, page 58 of Bul- 
letin no. 301, U. S. Geol. Survey. 
393. The Santa Fe peneplain. — Abstract : Science, new ser., vol. 23, p. 267, 
February 16, 1906. 
394. Fractured bowlders in conglomerate. — Am. Jour. Sci., 4th ser., vol. 22, 
pp. 231-234, 2 figs., September, 1906. 
Describes the occurrence in Arizona and discusses the origin of the phenomena. 
395. Natural mounds. — Jour. Geology, vol. 14, no. 8, pp. 70S-717, 3 figs., 
1906. 
Notes the form, size, and occurrence of these mounds and discusses the various 
hypotheses advanced to explain their origin. 
396. Rock folds due to weathering. — Jour. Geology, vol. 14, no. 8, pp. 718- 
721, 1 fig., 1906. 
Describes shallow folding in Arkansas, which is explained to be due to weathering. 
397. The formation of coal. Hypothesis to account for the transformation 
of vegetable matter into the different grades of coal. — Mines and Minerals, vol. 
26, no. 12, pp. 565-566, July, 1906. (Reprinted from Econ. Geology, vol. 1, 
pp. 26-33, 1905.) 
398. Review of " Report on the coals of Maryland," by William Bullock 
Clark and others (Maryland Geol. Survey, vol. 5). — Econ. Geology, vol. 1, no. 5, 
pp. 502-508, 1906. 
