LITERATURE AND SUMMARY OF OPINION 17 



were partly, if not wholly (in the case of Erie and Ontario), the effect of 

 glacial excavation. With a resounding blow on the table, Lesley said 

 that ki ice has no eroding power." There was a warm debate on a cold 

 topic. To the writer Newberry was a demi-god and Lesley was a very 

 impious mortal, but with the passing of time the conviction has come 

 that Lesley was essentially right. Many readers of these lines can 

 probably give similar experience. 



Literature and summary of opinion. — The opinions and arguments relat- 

 ing to this subject are scattered through an immense volume of glacial 

 and physiographic literature, and it seems undesirable to cumber these 

 pages with a host of references. An excellent digest of the literature on 

 the subject was published by Culver in 1895* In that paper it was 

 shown that from the time of Ramsay, 1862, who was responsible for giv- 

 ing currency to the idea of glacial origin of lake basins, up to 1895 very 

 few glacialists of note were advocates for extreme glacial erosion. On 

 the other hand, the vast majority of students of glaciers and glacial phe- 

 nomena had been emphatic in denying effective erosion to glacial ice. 

 Among these were Bonney, Judd, Neumayer, Heim, Forel, Whymper, 

 and most American geologists who had spent much time on living gla- 

 ciers. Culver's quotation of opinions shows this striking fact, that the 

 judgment adverse to ice erosion was almost entirely based on direct ob- 

 servation and field-study of glacial phenomena, while the opinions favor- 

 ing great erosion were abstract and theoretic, relying chiefly on physio- 

 graphic features. The same division of opinion is true today, and the 

 fact will be emphasized later. 



In 1900 Turner f summarized some of the opinions relating to ice ero- 

 sion as bearing specially on the problem in the Sierras. In the same 

 year Davis X published a review of previous writings on " hanging " val- 

 le} T s with an appended bibliographic list. 



References to the literature bearing on the origin of the Great lakes 

 and the valleys and lakes of New York up to 1900 may be found in two 

 publications by Tarr.g 



Some references to writings on special areas or particular localities 

 will be given in the following pages. 



THEORETICAL DISCUSSION 



Burden of proof . — The argument for deep rock erosion by glacial ice is 



*G. E. Culver : " The erosive action of ice." Trans. Wis. Acad. Sci., Arts and Letters, vol. x, 1895, 

 pp. 339-366. 



■f-H. W. Turner : "The Pleistocene geology of the south central Nevada with especial reference 

 to the origin of Yosemit* valley." Proc. Cal. Acad. Sci.. 3d ser., vol. i, no. 9, 1900, pp. 261-321. 



t W. M. Davis : '•Glacial erosion in France, Switzerland, and Norway." Proc. Boston Soc. Nat. 

 Hist., vol. 29, no. 14, July, 1900, pp. 273-322. 



\ R. S. Tarr : " Lake Cayuga a rock basin." Bull. Geol. Soc. Am., vol. 5, 1894, pp. 339-356. 

 "The physical geography of New York state," 1902, pp. 179, 227-234. 



