140 STUDIES, SCIENTIFIC AND SOCIAL chap. 



accompanied by a heaping up of the surface and great 

 grinding power, thus leading to those curiously embayed 

 hollows around Eppigen and Imhof, which are not found 

 on the opposite side of the valley, where the glacier had a 

 direct onward motion. 



It appears, therefore, that the singular phenomena of a 

 great valley barred across by a precipitous rocky ridge, 

 which is pierced only by a narrow water-worn gorge, ad- 

 mittedly sawn down by the debris-laden water of the sub- 

 glacial torrent, does aftbrd a most striking additional proof 

 of the power of the old glaciers to grind out rock-basins. 

 The only escape from this conclusion is to call in the aid 

 of hypothetical local subsidences or elevations of which no 

 direct evidence has yet been found. And when we see 

 that, besides all the existing valley-lakes of glaciated 

 countries, we have also to account for these gorge-pierced 

 rocky dams with the fiUed-up lake-basins above them, and 

 for the number of other filled-up rock-basins which occur in 

 the course of all the great Alpine valleys, the explanation 

 by subsidence becomes more and more difficult and impro- 

 bable. And the difficulty is still further increased by the 

 consideration, that all these earth-movements must have 

 been comparatively recent, that in all cases they must have 

 been so rapid that the erosion of the valley did not keep 

 pace with them, and that, in all non-glaciated areas, either 

 no earth-movements have occurred within the recent period, 

 or, if they have occurred, they have failed, in every single 

 case, to produce a lake-basin, because erosion has fully 

 kept pace with elevation. A theory which involves 

 such a series of improbable assumptions, and which is not 

 supported by any direct evidence, stands self-condemned. 



But besides this body of evidence, in itself almost con- 

 clusive, I have adduced in the preceding chapter a new 

 and independent argument founded on the characteristic 

 contoursof all these valley-lakes, which were shown to besuch 

 as could be produced only by ice-erosion in a pre-existing 

 valley, while any form of damming up by subsidence above 

 or elevation below the lake would necessarily result in a 

 very different contour. 



