GENERAL SUMMARY 73 



The altitude for creeks given in the above table is that of the valley 

 section lying in the Finger Lakes belt. The figures are given on the 

 map, plate 21. 



It will be seen that the western and eastern members of the lake series 

 are comparatively shallow, and that drift damming is the reasonable 

 explanation of their basins. This is equally true of Cayuga and Seneca 

 when the depth of the buried section is considered. The Finger lakes 

 are all properly classed as " morainal. 1 ' 



General Summary 



The first part of this paper discusses the question of glacial erosion 

 theoretically, having special reference to alpine glaciers, with illustra- 

 tions drawn from glaciated areas. The term erosion is restricted to 

 signify removal of unweathered rock. After showing that the argument 

 for erosion is inferential and chiefly based on uncertain topographic 

 forms, an argument for erosion is formulated, which is then considered 

 in detail and found inconclusive. A general negative argument based 

 on recognized principles of glacier physics proves that bottom erosion 

 of glaciers must be only by the slow process of abrasion, which is a 

 self-checking process ; that glaciers tend to widen rather than to deepen 

 valleys ; that glaciers can not deepen without widening their channels, 

 and that all theory and observation lead to the conclusion that glaciers 

 are ineffective agents in production of valleys or basins. The subject is 

 then illustrated by examples drawn from areas of past and present gla- 

 ciation in the northern hemisphere, with citation of observations and 

 opinions by students of those areas showing the absence of any direct 

 evidence of erosion, and that the chief claim for erosion is for Norwe- 

 gian and Alaskan fiords and some Alpine valleys made by the physi- 

 ographers on the ground of valley discordance. It is shown that such 

 explanation does not harmonize the body of fact, but produces confu- 

 sion. Lastly, it is shown that the ice-erosion argument for hanging 

 valleys is illogical without proofs of the competency of glaciers, and 

 that these features will undoubtedly be explained as normal product of 

 atmospheric and stream work under conditions not yet understood. 



The second division of the paper treats of the erosional phenomena 

 in New York state as a critical area specially illustrating the work of a 

 continental ice sheet. After showing that all observers agree on the 

 slight erosional effect of ice on the Adirondack highland and in the 

 Saint Lawrence valley, the area of western New York is found to yield 

 the same result. Central New York, or the district of the Finger lakes, 



