420 



LAKE OF GENEVA. 



[Ch. XVIII. 



the era at which the principal delta of Lake Leman or any 



commenced, we must 



with the geographical features and geological history of the 

 whole system of higher valleys which communicate with the 

 main stream, and all the changes which they have under- 

 gone since the last series of convulsions which agitated and 

 altered the face of the country. 



xi^yxu-xx, *~ — : of the Huttonian Theory of 



the Earth,' after declaring that he agreed in opinion with the 

 Scotch geologist that the principal valleys of the Alps and 

 other mountains had been excavated by rivers, frankly admits 

 that the Lake of Geneva seems to offer an objection to that 

 theory. The valley above is so deep and broad, that the ma- 

 terials removed from it ought to have filled up the lake again 

 and again ' on any reasonable supposition concerning its 

 original magnitude.' What has 

 which the Rhone has brought down from the higher region ? 



become 



To explain away the difficulty, he suggests, among other 

 hypotheses, that the lake had no existence while the river 

 was eroding the valley above. Part, both of the rising and 

 sinking of the land, he observes, has happened within periods 



comparatively modei 



The elevations and depressions 



may not be the same for every spot ; they may be partial, and 

 one part of a stratum or body of strata may rise to a greater 

 height or be more depressed than another. It is not impos- 



sible that this 



may 



change the relative level of their sides and bottom.' * 



The 



Vallais,' he also adds, ' which we consider as the work of the 

 Khone, may not have owed all its inequalities to the running 

 of water. It may, when the Alps rose out of the sea, have 

 included many depressions of the surface which the river 

 joined together, and from being a series of lakes formed into 

 one great valley.'t A suggestion has lately been made, that 

 the rock basin which the Lake of Geneva fills may have been 

 scooped out by ice. That it was once occupied by a glacier 

 I fully admit, but that the action of the glacier hollowed out 



* Playfair. Illustrations of Hut- 

 tonian Theory, p. 366. 



t Ibid. p. 367 



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