248 THE POPULAR SCIENCE MONTHLY. 



channels. But neither in the lakes which have been surveyed by 

 the Swiss Government, nor in the Atlas des Lacs Franchises 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 in- 

 dications of such submerged 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 subaerial 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 con- 

 tours of a valley, but that they never present peculiarities of 

 contour which are not unfrequent in mountain valleys, and never 

 show submerged ravines or those jutting rocky promontories 

 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 

 were 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 enormous pressure 

 of overlying strata, whereas the surface beds which are supposed 

 to have been moved to cause lakes are free to take any upward 

 or downward curves, and, as the source of motion is certainly 

 deep-seated, those curves will usually be of very gradual curva- 

 ture. Yet in the small lake of Annecy there are two separate 

 basins ; in Lake Bourget also two ; in the small lake of Aiguebel- 

 lette, in Savoy, there are three distinct basins of very different 

 depths ; and in the Lac de St. Point, about four miles long, there 

 are also three separate flat basins. In Switzerland the same phe- 

 nomenon is often found. In the Lake of Neufchatel there are 

 three basins separated by ridges from twenty to thirty feet above 

 the deeper parts. The small Lac de Joux, at the head of a high 

 valley in the Jura, has also three shallow basins. Lake Zurich 

 consists of three well-marked basins. The exceedingly irregular 

 Lake of Lucerne, formed by the confluence of many valleys meet- 

 ing at various angles hemmed in by precipitous mountains, has 

 eight distinct basins, mostly separated by shallows at the narrow 

 openings between opposing mountain ridges. This is exactly 

 what would result from glacier action, the grinding power of 

 which must always be at a maximum in the wider parts of val- 

 leys, where the weight of the ice could exert its full force and 

 the motion be least impeded. On the subsidence or curvature 



