392 Scientific Intelligence. 



Geology of Webster County, by Frank A. Wilder, contains (pp. 

 138-224) an exhaustive study of the Iowa gypsum deposits, as 

 well as those of other American and of foreign localities. The 

 Geology of Henry County is written by T. E. Savage. Cherokee 

 and Buena Vista Counties have been mapped by Thomas H. 

 Macbride, who presents new facts regarding the limit of the 

 Wisconsin drift and its effect on topography. The Geology of 

 Jeiferson County is by J. A. Udden, and that of Wapello by A. 

 G. Leonard, Assistant Slate Geologist. Vol. xii is fully up to 

 the high standard of previous volumes of the Iowa survey, espe- 

 cially as regards contributions to stratigraphy and glaciology. 



3. The JEvohition of the northern part of the Lowlands of 

 Southeastern Missouri ; by C. F. Maebut. University of Mis- 

 souri Studies, vol. i, IS'o. 3, 63 pp., 7 pis. — Southeastern Missouri 

 consists of belts of lowlands enclosing belts and isolated areas of 

 upland. As the result of field study (involving the making of a 

 topographic and a geologic map). Professor Marbut finds the 

 explanation of these belts as follows : The Mississippi River 

 flowed west of (the present) Crowley Ridge, then between 

 Crowley and Benton ridges and finally through Benton Ridge at 

 Grays Point. These successive channels were abandoned in 

 favor of small tributaries of the Ohio; ''the Mississippi has been 

 captured by the Ohio twice in succession." 



The author's former paper on this region (Bos. Soc. Nat'l Hist., 

 vol. xxvi, pp. 478-488) described Crowley Ridge as a cuesta^ and this 

 erroneous interpretation shows clearly the uncertain character ot 

 conclusions based on map study unaccompanied by field work. 

 As Professor Marbut says : " Tb have determined the whole suc- 

 cession of events and the processes operating to produce them, 

 would have been probably impossible by the methods of library 

 study alone" (p. 39). 



4. Geology of the Potomac Group of the Middle Atlantic 

 Slope ; by W. B. Clark and A. Bibbins. Bull. Geol. Soc. Am., 

 vol. xiii, pp. 187-214, 7 pis. — A narrow belt of sand and clays, 

 mostly unconsolidated and often ferruginous, form the basal 

 element of the Atlantic Coastal plain. These sediments — called 

 collectively the Potomac Group — are described in detail as regards 

 their composition, fossil contents and economic importance. The 

 relationship of the beds is given as follows : 



Raritan 

 Patapsco 



Jurassic (?) j pXtnt 



In regard to the conflicting evidence of paleontology and paleo- 

 botany (see this Journal, vol. ii, p. 433, Dec. 1896), the authors 

 think it essential to suspend final decision until more exhaustive 

 investigations of the faunas and floras has been made throughout 

 the entire Coastal region. 



Cretaceous \ 



