114 STUDIES, SCIENTIFIC AND SOCIAL chap. 



tinguish the two classes of lakes, and the application of 

 these tests serves to show that most of the valley-lakes of 

 glaciated countries were not formed by submergence. 



The first point is that valleys in mountainous countries 

 often have the river-channel forming a ravine for a few 

 miles, afterwards opening out into a flat valley, and then 

 again closing, while at an elevation of a hundred or a few 

 hundred feet, at the level of the top of the ravine, the 

 valley walls slope back on each side, perhaps to be again 

 flanked by precipices. Now, if such a valley were con- 

 verted into a deep lake by any form of subsidence, these 

 ravines would remain under water and form submerged 

 river channels. But neither in the lakes which have been 

 surveyed by the Swiss Government, nor in the Atlas des 

 Lacs Fran^aises of M. Delebecque, nor in those of the 

 German Alps by Dr. Alois Geistbeck, nor in the lakes of 

 our own country, can I find any indications of such sub- 

 merged river-channels or ravines, or any other of the 

 varied rock features that so often occur in valleys. Almost 

 all these lakes present rather steeply sloping sides with 

 broad, rounded, or nearly level bottoms of saucer shape, 

 such as are certainly not characteristic of sub-aerial valley 

 bottoms, but which are exactly what we might expect 

 as the ultimate result of thousands of years of incessant 

 ice-grinding. The point is, not that the lake-bottoms may 

 not in a few cases represent the contours of a valley, but 

 that they never present peculiarities of contour which are 

 not unfrequent in mountain valleys, and never show sub- 

 merged ravines or jutting rocky promontories like those 

 which are so common a feature in hilly districts. 



The next point is, that Alpine lake-bottoms, whether 

 large or small, frequently consist of two or more distinct 

 basins, a feature which could not occur in lakes due to 

 submergence unless there Avere two or more points of 

 flexure for each depression, a thing highly improbable 

 even in the larger lakes and almost impossible in the 

 smaller. Flexures of almost any degree of curvature are 

 no doubt found in the rocks forming mountain chains ; but 

 these flexures have been produced deep down under enor- 

 mous pressure of overlying strata, whereas the surface beds 



