208 E. C. ANDREWS. 



that they depend for their understanding upon a suggestion 

 derived from a consideration of streams in general; and 

 that general stream principles in turn again may only be 

 appreciated after actual observation of the successive 

 steps in the development of land profiles which have been 

 formed by one or more stream types. 



Half a century ago Ramsay explained the profiles of 

 certain Alpine Lake Basins as those due to the action of 

 ice. Nevertheless, the observed action of present-day 

 glaciers apparently 1 does not bear out his statements. (This 

 does not necessarily prove that Ramsay was wrong, but it 

 does show, however, that Ramsay missed at least one link 

 in the chain of evidence). Then came the inductive studies 

 of such observers as Chamberlin, Davis, Gilbert, Tarr, 

 Penck, Gannett, Bailey Willis, W. D. Johnson, Salisbury, 

 J. Geikie, McGee, Reid, Matthes Blandford and others, by 

 whom it was demonstrated that certain land profiles were 

 always and only found in regions which had been but 

 recently deglaciated. Moreover, they showed that in pro- 

 portion to the intensity of the glaciation to which a region 

 had been subjected so had these ''peculiar" land profiles 

 been correspondingly emphasised. 



A very valuable suggestion was thus afforded, neverthe- 

 less, this evidence in itself was not sufficient to actually 

 prove that these land profiles were due to the action of 

 glaciers. 2 With the progress of time additional light was 

 shed on this subject. Thus in a description of the famous 

 amphitheatres in the Red Wall Limestone of the Colorado 

 Canon, Davis 3 showed how such profiles have been deter- 

 mined by weathering and by stream action. He described 

 the avalanche also as a stream. Then later, from compara- 

 tive stream studies also, came the knowledge that certain 



1 See Culver, Fairchild and references quoted therein. 



2 See Culver, Fairchild and references. 3 Davis (d) pp. 176- 180. 



