200 PEOCEEDINGS OP THE GEOLOaiCAL SOCIETY. [Mar. 5, 



2nd. I think the theory of an area of special subsidence for each 

 lake untenable, seeing no more proof for it in the case of the larger 

 lakes than for the hundreds of tarns in perfect rock-basins common 

 to all glacier- countries, present or past, and the connexion of which 

 with diminished or vanished glaciers I proved originally in ' The Old 

 Glaciers of IS'orth Wales.' In the Alps there is a gradation in size 

 between the small mountain- tarns and the larger lakes. 



3rd. None of them lie in lines of gaping fracture. If old fractures 

 ran in the lines of the lakes or of other valleys, and gave a tendency 

 to lines of drainage, they are nevertheless, in the deep-seated strata, 

 exposed to us as close fractures now, and the vaUeys are valleys of 

 erosion and true denudation. 



4th. They are none of them in simple synclinal basins, formed 

 by the mere disturbance of the strata after the close of the Miocene 

 epoch: nor, 



5th, Do they lie in hollows of common watery erosion ; for run- 

 ning water and the stiU water of deep lakes can neither of them ex- 

 cavate profound basin-shaped hoUows. So deeply did Plajfair, the 

 exponent of the Huttonian theory, feel this truth, that he was fain to 

 liken the Lake of Geneva to the petty pools on the JN'ew Eed Marl 

 of Cheshire, and to suppose that the hoUow of the lake had been 

 formed by the dissolution and escape of salts contained in the strata 

 below. 



6th. Eut one other agency remains — that of ice, which, from the 

 vast size of the glaciers, we are certain must have exercised a power- 

 ful erosive agency. It required a solid body, grinding steadily and 

 powerfully in direct and heavy contact with and across the rocks, to 

 scoop out deep hollows, the situations of which might either be deter- 

 mined by unequal hardness of the rocks, by extra weight of ice in 

 special places, or by accidental circumstances, the clue to which is lost, 

 from our inability perfectly to reconstruct the original forms of the 

 glaciers. 



7th. It thus follows that, valleys having existed giving a direc- 

 tion to the flow of the glaciers ere they protruded on the low coun- 

 try between the Alps and the Jura, these vaUeys and parts of the 

 plain, by the weight and grinding power of ice in motion, were modi- 

 fied in form, part of that modification consisting in the excavation of 

 the lake-basins under review. 



In connexion with this point, it is worthy of remark that glaciers, 

 many of them very large in the modern sense of the term, on the 

 south side of the Yallais (excepting those of Mont Blanc), and the 

 large glaciers on the south side of the Oberland,aU drain into the Lake 

 of Geneva ; those on the north of the last-named snow-field, also 

 large glaciers, are drained through the Lakes of Brienz and Thun. 

 These, among the largest existing glaciers of the Alps, are only 

 the shrunken tributaries of the greater glaciers that in old times 

 filled and scooped out the basins of the lakes. The rest of the 

 lakes, as already stated, are in equally close connexion with the old 

 snow-drainage of glacier-regions on the grandest scale, — aU of them, 

 excepting those of Neuchatel, Bienne, and Morat, lying in the direct 



