Prof. B. Studer on the Origin of the Swiss Lakes. 489 



summits, we may still doubt whether they could have acquired 

 and retained the force necessary to hollow out valleys of the 

 depth of our lakes, and of from 20 to 30 Swiss leagues in length. 



However, since the appearance of the classical works of Sir 

 Charles Lyell, these great efforts of the imagination are no longer 

 popular, and the great debacle, which was admitted chiefly in 

 order to explain the transportation of boulders, has given place 

 to the calm and slow movement of the glaciers. It is also by 

 means of the glaciers that De Mortillet, Ramsay, and their ad- 

 herents suppose the basins of the lakes to have been hollowed 

 out. After what has been said as to the erosive action of gla- 

 ciers, it is useless to return to this question. I shall confine 

 myself to remarking that upon the bed of gravel and detritus of 

 unknown depth which extends in front of our great glaciers at 

 Chamouni, at the glaciers of Arolla, Ferpecle, and the Aar, and 

 in front of all the others, we do not see the least trace of the 

 asserted tendency of the glaciers to bury themselves by digging 

 out the soil. We also know that in those regions where the gla- 

 ciers attain the sea-shore, they are prolonged above the water, 

 and do not sink below its level. 



Having thus ascertained the insufficiency of erosion for the 

 explanation of the origin of the valleys and lakes of the Alps, we 

 can hardly choose but recognize, with C. Escher, an intimate 

 connexion between a great number of Alpine valleys and the in- 

 clined position of the strata in the chains which they separate. 

 These are true orographic valleys, such as M. Desor has pointed 

 out in the Jura ; and to the two kinds described by him — the 

 synclinal and isoclinal valleys — we must add, according to Escher, 

 for the Alps the anticlinal valleys, of which the Justithal to the 

 east of the Lake of Thun presents a fine example. As to the 

 cluses, with which we shall join those rocky ravines which cut 

 the interior beds of the chains in the direction of the clip, and to 

 which Thurmann has given the name of Ruz, these are evidently 

 ruptures, often enlarged by erosion. We shall likewise add the 

 valleys of sinking [vallees d 1 ' affaissement) , which indeed do not occur, 

 as far as I know, in the Jura, but play a great part in volcanic 

 countries ; and perhaps some flat-bottomed circular valleys in the 

 Alps may be referred to this type. 



However, a classification of valleys founded upon the oro- 

 graphy of the Jura can only find a very limited application in 

 the Alps. Most of the Alpine valleys, and indeed all those of 

 any extent, are valleys of rupture which cut the strata at more 

 or less oblique angles; frequently also they are complex, and 

 pass from one type to another ; and many of them are combined 

 with great faults. Even longitudinal valleys of small size, and 

 apparently quite simple at the first glance, will not conform to 



