Prof. B. Studer on the Origin of the Swiss Lakes. 485 



and that subsequently, these moveable materials being unable to 

 resist the pressure of the glaciers, the basins were cleared out 

 and filled with ice up to the period of the thaw, and of the retreat 

 of the glaciers into the high Alps. M, Desor* supposes the 

 lakes to have existed until the arrival of the ice, to have been 

 temporarily filled by the glacier which transported the gravel 

 blocks on its surface, and to have returned to the condition of 

 lakes when the glaciers retreated. M. Ombonit combines these 

 two solutions in one. The glaciers, according to him, advanced 

 to the lower extremity of the lakes, replacing the water with ice; 

 torrents issuing from the long-stationary glaciers deposited the 

 ancient alluvium; and, lastly, the glaciers, again advancing, 

 worked up the soil of this alluvium and deposited the moraines 

 and blocks which repose upon it. 



None of these geologists doubted the relation between our 

 lakes and the elevation and orography of the Alps. M. Desor 

 explains even his lakes of erosion by the action of powerful cur- 

 rents caused by the retreat of the waters in consequence of the 

 elevation. The theory was carried still further in England. 

 Mr. Ramsay J, who, from his long-continued researches upon 

 the effects of glacial action in Wales and in the Alps, was pre- 

 pared to regard the question from a new point of view, sees no 

 essential difference between the small lake-basins of the mountains 

 of Wales, Scotland, and Switzerland, often hollowed out of the 

 solid rock, and the enormous depressions of our great lakes. 

 Attributing the former to the slow erosion of glaciers upon their 

 bottom, he does not hesitate to assume that the same agent has 

 produced the latter, and that all the basins of our great lakes are 

 the result of glacial erosion. As these basins did not exist before 

 the origin of the erratic formation, the transportation of the 

 ancient alluvium by rivers would be explained without any diffi- 

 culty. This theory of the learned Professor has been favourably 

 received by several geologists of the highest merit. Professor 

 Tyndall§ goes still further. He ascribes not only the basins of 

 our lakes, but the Alpine valleys themselves to the erosion of 

 glaciers. The whole Alpine system, according to this celebrated 

 physicist, formed originally an immense smooth boss or enor- 

 mous mass, in the surface of which the glaciers, by their gradual 

 advance, hollowed out our valleys. Mr. Beete Jukes ||, who had 

 previously indicated the great effects of erosion in the conforma- 

 tion of Ireland, declares himself in favour of this opinion ; and 



* Revue Suisse, 1860. Actes de la Soc. de Lugano, 1861. 



f Aid della Soc. Ital. vol. v. (1863), November. 



X Quart. Journ. Geol. Soc. vol. xviii. (1S62). 



§ " Conformation of the Alps," Phil. Mag. September 1862. 



|| Address to the Geological Section of the British Association, Oct. 1862. 



