490 Prof. B. Studer on the Origin of the Siviss Lakes. 



the Jurassic classification. The valley of the Bas-Simmenthal 

 may be classed among the synclinal valleys ; but what a difference 

 there is between it and the valleys of the same kind in the Jura ! 

 At the bottom of the latter the beds are horizontal, and rise to 

 the two sides; in the Simmenthal they are vertical, and diverge 

 upwards like a fan — it looks like a synclinal valley folded up 

 (refoulee) by lateral pressure. The valley of the Pays d'Enhaut, 

 from Gessenay to Chateau d'Oex, also appears to be longitudinal; 

 nevertheless it cuts obliquely through three zones of Flysch and 

 two intermediate ranges of limestone which run from N.E. to 

 S.W. The Valais in the neighbourhood of Sion is an isoclinal 

 valley, its two sides inclining to the S.E. ; but its northern side 

 consists of Jurassic limestone, and the opposite side, which ought 

 to be more recent, belongs to the carboniferous series. Here 

 there has evidently been a great fault. The same circumstance 

 occurs again at the Lake of Brienz : the base of the northern 

 range being Neocomian, the base of the group of the Faulhorn, 

 which would be supposed to be superior, is Jurassic; and the 

 Neocomian strata only occur at the very summit of this group. 

 The relation of the great transverse valleys of the Alps with the 

 cluses of the Jura is no better founded: most of these com- 

 mence by gigantic ruz, such as those of the Aar, of the Grimsel 

 at Gutannen, and of the Reuss from the St. Gothard to Amstseg, 

 Further down this character is lost; the valley, cutting the 

 ranges horizontally, resembles the cluses, as that of the Arve 

 from Sallenches to Cluse, that of the Reuss from Amstseg to 

 Brunnen, where it unites with a longitudinal valley, and that of 

 the Aar from Meiringen to Leissigen. But the further we de- 

 scend, the more we see the difference between its opposite sides 

 increase ; so that a valley which still appears to belong to the 

 class of cluses, often separates two systems of mountains of a 

 totally different geological character. This is the case in the 

 valley of the Arve between Bronneville and Annemasse, in 

 that of the Aar upon the margins of the Lake of Thun, in that 

 of the Rhine from Schollberg to Rheineck, and in that of the 

 Iller at Sonthofen. By this circumstance these valleys acquire 

 a significance of much more importance than that of being 

 simple crevasses ; they appear as boundaries, probably of great 

 antiquity, between two different groups of mountains, such 

 as would be a boundary placed between the Alps and the Jura, 

 or between the latter and the Vosges. And, lastly, how are we 

 to class the great semicircular valley which extends from 

 Reichenau by Coire to the Lake of Wallenstadt, resembling, on 

 a colossal scale, the Atrio dei Cavalli of Vesuvius ? Moreover, 

 this does not appear to be unique in the Alps. We may find a 

 parallel to it in the valley which follows the Rhone from Mar- 



