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



tive fluid. Some, following their masters, admit only marine 

 currents, rivers, or torrents ; the others, amongst whom we 

 find some justly celebrated English and Italian physicists and 

 geologists, have lately proposed to accept the intervention of the 

 erosive action of glaciers. 



Each of these views is justified by the facts which take place 

 before our eyes, for nature frequently makes use of very different 

 means of producing the same effect. Desor, in an excellent 

 article " On the Physiognomy of the Swiss Lakes "*, adopts both 

 the principal theories, and applies them according to the nature 

 of the lake the origin of which he is endeavouring to explain. 

 He distinguishes the orographic lakes, or those depending on the 

 orography of the country, from the lakes of erosion, of which the 

 basins have been hollowed out by water. The former are divided 

 into three categories : — 1st, the lakes of the synclinal or boat- 

 shaped valleys t, such as the Lac du Bourget, the Lac de Joux, 

 and the Lac de Saint-Point ; 2nd, the lakes of the isoclinal or 

 coinbe-like valleys, among which are the lakes of Brienz and 

 Wallenstadt ; and 3rd, the lakes of the transverse valleys or 

 cluses, of which the lakes of Thun and Uii are examples. The 

 alpine lakes, according to M. Desor, are chiefly orographic lakes ; 

 whilst those of Neuchatel, Bienne, Morat, Zurich, and Con- 

 stance, and others situated in the lower parts of Switzerland, are 

 lakes of erosion. Some are the combined product of both prin- 

 ciples ; the Lake of Geneva, from Villeneuve to Vevey, is a trans- 

 verse-valley lake (lac de cluse), and from Vevey to Geneva a lake 

 of erosion. In a supplement J, M. Desor extends his classifica- 

 tion to the lakes of the Italian slope of the Alps, where he finds, 

 according to M. de Mortillet§, a new category in the lakes of 

 moraines. Their origin is explained by ancient moraines, which 

 have served as barriers to the water at the mouth of the valleys. 



The question becomes still more complicated if, in order to 

 determine the epoch of formation of the lakes, we examine the 

 geology of the strata which surround them. All the lower part 

 of Switzerland and of the first chain of the Jura is sprinkled over 

 with Alpine blocks, which, whatever may have been their mode 

 of transport, must necessarily have passed over the lakes in order 

 to pass from their original position to their present place, and we 

 cannot conceive but that the current which carried them would 

 have filled up these basins and formed a great cone of debris 



* Revue Suisse (1860). 



t M. Desor calls these valleys vallons. but this term does not appear to 

 be well chosen*; vallon is the diminutive of rallee. and the synclinal valleys, 

 on the contrary, are the largest in the Jura. 



J Actes de la Soc. de Lugano (1361). 



§ Bull, de la Soc. Geol. >". S. vol. svi. 



