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POPULAR SCIENCE MONTHLY 



Fig. 12. Hanging Valley Tributary to Russell Valley (Fig. 11). The first tributary 

 from the mouth on the north side. The lip of this valley lies about 1,000 feet above the main 

 valley floor, and the stream flows over it on the very surface of the rock, forming a gorge, 

 below which it crosses moraine. A small glacier lies at the head of this hanging valley. Pho- 

 tograph by Lawrence Martin. 



so unlike their abundant and striking development in glaciated regions, 

 that they are hardly to be considered as bearing upon the problem. 



The facts discovered in reading the literature and in field investi- 

 gation, point to glacial erosion as the cause of the hanging valleys and 

 associated phenomena, while no facts are found that are vitally opposed 

 to it. Of no other hypothesis proposed may the same be said; on 

 the contrary, all other explanations are open to fatal objections.. The 

 great majority of students of glacial action are now in accord with the 

 belief in profound glacial erosion in favorable situations. Even those 

 opposed to the explanation by glacial erosion admit that the forms 

 under discussion are what would be expected if it were possible for 

 glaciers to perform such great erosive work. 



The few who are opposed to this explanation have been able to 

 offer no better argument against it than their failure to believe in 

 the ability of ice to do erosive work in great amount. Some of this 

 opposition is based upon observations at the margins of small glaciers. 

 But all such observations have little value; for, as has been well stated 

 by another, if an observer could have been where ice was really capable 

 of profoundly eroding, he would not have been able to come back and 

 talk about it. The weak, retreating margin of a small valley glacier 

 gives no better basis for understanding profound glacial erosion than 

 a small meadow brook gives for a conception of the mode of formation 



