1862.] 



RAMSAY — GLACIAL ORIGIN OF LAKES. 



185 



On the Glacial Oeigin of certain Lakes in Switzerland, the Black 

 FoEEST, Great Britain, Sweden, North America, and elsewhere. 

 By A. C. Eamsay, P.E.S., President of the Geological Society, &c. 



[Plate VIII.] 

 Contents. 



Erroneous theories of the Transport 

 of Alpine Blocks : reasons for aban- 

 doning them. 



Old Distribution of the Great Alpine 

 G-laciers. 



Connexion between Tarns and Gla- 

 ciers. 



Origin of the Great Alpine Lakes. 



The G-reat Lakes : — 

 The Lake of Geneva. 

 The Lake of Thun. 



The Lake of Lucerne, 



The Lake of Zurich. 



The Wallen See. 



The Lake of Constance. 



The Italian Lakes, 

 Summary with regard to the Alpine 



Lakes. 

 Lakes of the Northern Hemisphere 



generally. 

 The Glacial Theory. 



Erroneous Theories of the Transport of Alpine Blocks. — In the year 

 1859, in a series of papers by the members of the Alpine Club, I 

 published a memoir in which I compared the old glaciers of North 

 Wales with those of Switzerland ; and in it, among other matters, I 

 explained the glacial origin of certain rock-basins now holding lakes, 

 on the watersheds and in the old glacier-vaUeys of both those 

 countries ; and in a later edition of the same memoir, published as 

 a separate book, with additions*, I extended these generalizations to 

 many of the lakes in Sutherlandshire. 



In the same work I also expressed an opinion that the blocks of 

 Monthey, in the valley of the Khone, and the great erratic boulders 

 that strew the southern flank of the Jura had been transported by 

 icebergs derived from glaciers which descended in the Alpine valleys 

 to the sea-level, during a period of submergence in which the low 

 country that lies between the Jura and the Oberland was covered 

 with erratic drift. 



There was nothing new in this latter opinion, for it had previously 

 been held by several distinguished geologists, both English and con- 

 tinental. 



Since then I have twice revisited Switzerland, and have seen good 

 reason to change my opinion respecting the cause of the trans- 

 port of erratic blocks to Monthey and the Jura, and of debris 

 not remodelled by rivers, &c., that lies scattered over the lowlands 

 of Switzerland, or that borders, or lies in great mounds well out in, 

 the plain of Piedmont and Lombardy. I am now convinced, for 

 example, that the vast circling moraine of Ivrea, noticed by Studer in 

 1844, was shed from a glacier, 105 miles in length, that filled the 

 valley of Aosta to a height of more than 2000 feet, and protruded far 

 into the plain ; while on the north a still greater glacier, long ago 

 described by Charpentier, flowed from the valley of the Ehone right 

 across the low country until its end abutted on the Jura. As there 

 are still many persons in England who doubt these conclusions, it 



• The Old Glaciers of North Wales.' Longman & Co. 



