W ATKINS GLEN 391 



valleys of the Alps. Kockies and Sierra Nevada; and associated with 

 it is a condition of gorges and falls below the lips of the hanging 

 valleys. It is a notable fact that these regions, like that of the Finger 

 Lakes, are regions formerly occupied by powerful glaciers; and it is 

 even more noteworthy that hanging valleys and associated steepened, 

 straightened main valley walls are practically absent in regions not 

 formerly occupied by glaciers. 2 So general is this association; so 

 like the work of ice erosion, as we conceive it, is the anomalous valley 

 form; and so unlike is it to the valleys of stream erosion origin, that 

 physiographers are now quite generally agreed that the hanging valley 

 and the broadened and straightened main valley are the result of 

 glacial erosion. 



There are still some who question this conclusion, but none of them 

 has offered a satisfactory substitute or advanced a vital objection to 

 the ice erosion explanation. It is a relatively new point in interpre- 

 tation of land sculpturing and naturally is not universally accepted at 

 the start. The same was true when the origin of ordinary valleys by 

 stream erosion was proposed in place of the current explanation of 

 catastrophes. In fact, some of the most ardent supporters of the ice- 

 erosion theory are recent converts to it. 



When the hanging valleys of the Finger Lake region were first 

 recognized, and ice erosion proposed in explanation of them and of 

 the main lake valleys, 3 there were few who accepted the conclusions 

 advanced; but now the great majority of American physiographers 

 accept the ice erosion explanation for this region, as well as for others. 

 The literature of glacial erosion is now extensive, and the fact of pro- 

 found ice erosion in valleys freely followed by glaciers seems estab- 

 lished; but it would be aside from the purpose of this paper to state 

 the full argument for glacial erosion, Which, in fact, others have 

 already done. Suffice it to say that glacial erosion will explain the 

 conditions in the Finger Lake valleys, and no other theory so far pro- 

 posed will do so. Moreover, these valleys were a highway for glacial 

 motion, as is proved by the presence of pronounced moraines along 

 their sides and at their heads. 4 



When the glacial erosion theory was first applied to these valleys it 

 was supposed that the erosion was simple and of a single period; but 

 the discovery of other facts led first to a question whether some other 

 explanation than ice erosion might not be necessary, 5 and later to the 



'This statement ought perhaps to be slightly qualified, since exceptional 

 instances of hanging valleys have been described from such regions where other 

 causes, such as marine erosion and faulting, account for the hanging valleys. 



3 Lincoln, Arner. Jour. Set., Vol. XL1V., 1892, pp. 290-293; Tarr, Bull. 

 Geol. Soc. Amer., Vol. V., 1894, pp. 339-35G. 



4 Tarr, Bull. Geol. Soc. Amer., Vol. XVI., 190.5. pp. 213-228. 

 6 Tarr, Amer. Geol, Vol. XXXIII., 1904. pp. 271-291. 



