1862.] RAMSAT — GLACIAL OEiaiN" OF LAKES, 193 



some traces of freshwater deposits, perhaps of the age of part of the 

 Crag. No such relics exist. 



The Great Lakes. Lake of Geneva. — The Lake of Geneva is about 

 45 miles in length by about 12 in breadth, and its delta, once part 

 of the lake, between Villeneuve and Bex, is 12 miles long. The 

 latter and a small part of the banks of the lake beyond the mouth 

 of the river lie in the great Rhone valley, formed of older Tertiary 

 and Secondary rocks. All the rest of the lake is surrounded by the 

 low country formed of the various subdivisions of the Molasse and 

 JN'agelfluh. The lake is 1230 feet above the level of the sea, and 

 984 feet deep towards the eastern end, according to the soundings of 

 De la Beche *. See fig. 1, p. 194. 



Geneva itself stands on superficial debris; but the solid rock 

 first appears in the river-bed below Geneva, at Yernier, at the level 

 of 1197 feet above the sea — only 33 feet below the surface of the 

 lake, or 951 feet above the deepest part of its bottom. Any one 

 acquainted with the remainder of the physical geography of the 

 country will therefore see that the water of the lake lies in a true 

 rock-basin. The question thus arises. How was this basin formed ? 



1st. It does not lie in a simple synclinal basin ; for, though the 

 Lake of Geneva lies in the great synclinal hollow of the Miocene 

 strata between the Alps and the Jura, it is evident by an inspection of 

 the country that the flexures of that formation are of far greater 

 antiquity than the lake. These flexures have been denuded, and the 

 lake runs in a great degree across their strike. 



2nd. Por reasons already stated, it is, I believe, impossible to 

 prove that the lake lies in an area of special subsidence, aU the pro- 

 babilities being against this hypothesis. 



3rd. It is almost needless to say that the Lake of Geneva is too 

 wide to lie in a mere line of fracture ; and I know of no reason why 

 the valley of the Rhone, where occupied by the delta, should be 

 esteemed a line of fault or gaping fissure, any more than many other 

 vaUeys in Switzerland, which many geologists will consider with me 

 chiefly the result of the old and long- continued subaerial denudation 

 of highly disturbed strata. I could enter on details to prove this point, 

 but they belong rather to the rock-geology of Switzerland than to the 

 matter in hand. 



4th. Those who do not believe in the existence and excavating 

 power of great and sudden cataclysmal floods will at once see that 

 the area of the lake cannot be one of mere watery erosion ; for ordi- 

 nary running water, and far less the still water of a deep lake, can- 

 not scoop out a hollow nearly 1000 feet in depth. 



Now, if the Lake of Geneva do not lie in a synclinal trough, in an 

 area of subsidence, in a line of fracture, nor in an area of mere 

 aqueous erosion, we have only one other great moulding agency left 

 by which to modify the form of the ground, namely, that of ice. 



"When at its largest, the great glacier of the Rhone (No. 1 of the 

 Map, PL YIII.) debouched upon the Miocene beds where the eastern 

 end of the Lake of Geneva now lies. The boulders on the Jura, near 

 * Edinburgh Philosophical Journal, 1820, vol. ii. p. 107, and plate 2. 



02 



