Alpine Lakes. 443 



southern slopes of the Oberland, and the northern 

 drainage of all the southern Alps, from Mont Blanc 

 to the Matterhorn, which looks down on the modern 

 puny glacier of the Eh one. But where at its western 

 end, near Geneva, the ice was thinner, there the pressure 

 and grinding power were less, and the waste of the 

 underlying rock was proportionately diminished. The 

 result was, that a great hollow was scooped out, at 

 least 984 feet deep as sounded by De la Beche, or about 

 1 ,000 feet as given by later measurements in the deepest 

 part, without allowing for the moraine matter that, in 

 later times, must have been left in the depths of the 

 lake by the retreating glacier, or for the modern sedi- 

 ment that covers the bottom. At first it may be diffi- 

 cult to realise this theory and to appreciate the mode of 

 action of the ice, but when we compare the depth with 

 the length of the lake and the height and weight of the 

 ice above, and reduce all to a true scale, as shown in 

 fig. 92, it becomes evident that the depth of the rock- 

 basin is comparatively quite insignificant. 



I have elsewhere shown that the rock-bound lakes 

 of Brienz and Thun had the same kind of origin. These 

 were originally one lake, but are now separated by 

 broad alluvial meadows. In like manner the Lakes of 

 Lucerne, Zug, the Wallen See, Zurich, and Constance, 

 all lie in rock-basins of erosion by glacier ice. The same 

 is the case with many other Swiss lakes of minor note, 

 and should anyone wish to see actual basins, visibly 

 bordered by glaciated rocks, let him critically inspect 

 the lakes of Sarnen and Lungern on the route from 

 Lucerne across the Brunig. The deep hollows in which 

 the great Italian lakes lie on the south side of the Alps 

 had a similar origin. 1 



1 .See Memoir by the Author, On tlie Glacial Origin of certain 



