REVIEWS 549 



seems a bit fanciful to believe that the streams now have a general 

 course originally developed on the top of the ice. It is also difficult 

 to imagine how streams, granting that they were developed on the ice 

 in a symmetrical fashion, could be transferred to the drift surface 

 during the melting of the ice without disturbance of their arrange- 

 ment. If the disappearance be supposed to be accomplished by frontal 

 retreat, the edge of the ice itself will give a sufficiently marked line for 

 the development of the cross streams, and the major streams would in 

 all probability be developed normal to the ice front. This apparently 

 accords with the facts of the field and does not involve the difficulty 

 of accounting for the development of a vigorous surface drainage on 

 the ice and its transfer to the drift surface without notable destruction 

 of its arrangement. The whole problem is an interesting one, and 

 certainly Mr. Udden's hypothesis, if valid, is widely applicable. If we 

 are to be able from the present stream arrangement to infer so much 

 regarding the condition during glacial times a considerable step in 

 advance is made. This fact warrants the closest skepticism in exam- 

 ining the hypothesis. 



The volume as a whole is one which geologists will welcome. 

 While the long series of annual reports made up of separate county 

 reports is confusing to one not familiar with the region, the survey is 

 systematically building up a work which will prove valuable not only 

 to students of the local geology but to geologists in general. The 

 work will lend itself to final summary treatment, and in the meantime 

 the county reports not only serve a useful purpose locally, but enable 

 outsiders to keep in touch with the results. The progress map of the 

 drift mapping (plate II) is particularly valuable in this regard. 



H. F. B. 



Beach Structures in the Medina Sandstone. By H. L. Fairchild. 

 American Geologist, Vol. XXVIII, pp. 9-14, plates 2-6. 

 In the July number of the American Geologist Professor H. L. 

 Fairchild discusses the "Beach Structures in the Medina Sandstone." 

 The features considered are certain troughs and swells of a breadth 

 ranging from thirty to eighty feet. These are assumed to be of the 

 same nature (probably in some cases the same examples) as those which 

 formed the basis of Dr. Gilbert's theory of "giant ripples." Gilbert 

 had concluded {Bulleiifi Geol. Soc. Ajner., March 1899) that with 



