Geology and Mineralogy. 221 



been the greatest mother of geologists, the training gronnd for 

 most American workers in the science between 1843 and 1890. 

 Moreover, due to Hall's great influence, interwoven with the 

 growth of geologic knowledge in New York is the development of 

 the geology of the entire Mississippi Valley. Hall ' ' guided official 

 geologic movements in every state where they were inaugurated 

 and in many his own hand took a helmsman's part." Not the 

 least valuable feature of the book are the many letters quoted 

 wholly or in part, with their interesting side-lights on the emi- 

 nent writers and the times in which they lived. 



Doctor Clarke has made full use of his unique opportunity to 

 know Professor Hall and his history, and he is to be heartily 

 congratulated on the results he has attained. c. s. 



2. The Problem of the St. Peter Sandstone; by Charles L. 

 Dake. Univ. of Missouri School of Mines and Metallurgy, Tech- 

 nical Series, Bull., vol. 6, No. 1, 225 pp., 30 pis., August/l921.— 

 This thorough and clearly presented study of the environment 

 under which the St. Peter was laid down is based on the very 

 wide distribution of this formation throughout the Mississippi 

 valley. Starting out with the prevalent idea in modern times, the 

 author "was biased in favor of the desert origin of the sand- 

 stone," but finally became convinced "that the formation is in 

 fact of marine origin. ' ' The rounded and frosted nature of the 

 sand grains is found to be of antecedent origin and was not pro- 

 duced during the time of the St. Peter deposition. This character 

 of the sands is inherent in those of the Upper Cambrian (Croix- 

 ian) and it is from this northern formation, once of far wider 

 distribution than at present, that the sands of the St. Peter were 

 derived. Similar sands occur in other Ordovician formations. 

 Finally, the St. Peter is a well bedded formation of cleanly 

 washed sands (almost 99 per cent silica), and even though fossils 

 are rare, a considerable fauna was obtained by Sardeson in the 

 midst of this series in Minnesota, which is farthest away from the 

 source of the marine transgression. In the south, the equivalent 

 formations of the St. Peter more often yield marine fossils. 



Incidentally the report records much information as to the 

 formations beneath the St. Peter, and more especially those above 

 it. Two valuable correlation tables and many excellent views of 

 outcropping formations accompany the book. The author is to 

 be congratulated on his excellent work, which constituted his 

 dissertation for the doctorate at Columbia University. c. s. 



3. A Geological Reconnaissance of the Dominican Republic; 

 by T. \Y. Yaughax, AYvthe Cooke, D. D. Condit, C. P. Ross, 

 W. P. AYoodrixg, and F. C. Calkins. Geol. Survey Dominican 

 Republic, Memoirs, vol. 1, 268 pp., 23 pis., 1921.— This important 

 publication, the joint work of the Dominican Republic and the 

 U. S. Geological Survey, describes the geography, geology, strati- 



