Foerste. | 
400 
[April 6, 
lie would at once be struck by the beauty and regularity of the 
transverse valleys made by the Suxe, the Birse, and their tribu- 
taries, in crossing the Jura folds. The Swiss call them very 
appropriately, cirques , from the rounded form of their walls. 
The longitudinal valleys along the synclinal troughs have mani- 
festly a structural origin ; the occasional shallow longitudinal valleys 
along the crests of the anticlines have given rise to some dis- 
cussion, and will be considered below ; but the transverse cirques 
have attracted much attention. How came these transverse valleys 
to exist? The most ready explanation is that the rivers here fol- 
low the direction of old cracks, and subsequent erosion upon the 
anticlinal structure of their sides has given these valleys their 
beautiful outlines. J. Thurmann refers to them as ruptures. 
A. Gressly expressed as his opinion that — “ Examining from afar, 
the accordance existing between the folds and the cirques 
( crat&res ) forming interruptions in their continuity from time to 
time, the observer is surprised to see with what regularity the 
different cirques reproduce themselves from point to point, and 
almost along the same transverse rays, always giving rise 
to a second series of folds more numerous and more or less ar- 
ranged in the form of a fan. The different cirques denote the 
time and places of retardation in the process of elevation, except- 
ing for which there would have been some degree of rest ; for it is 
at these points that for a certain length of time all the energy of 
the agent giving rise to folding exerted itself, finally producing 
ruptures or faults, of which the most important have given rise to 
new chains of mountains.” It is evident that Gressly had an 
incorrect idea of the manner in which the force causing elevation 
was exerted, but there is no doubt about the fact that he ascribes 
the origin of cirques to fissures or faults. The more or less 
circular outlines of cirques he explained by the explosion of huge 
reservoirs of gas during the process of folding. B. Studer 
believed in cracks assisted by denudation. E. Desor insisted on 
the impossibility of streams having given rise to all cirques. “ If 
this were so the cluses and combes should also be found only along 
the path of streams. If some fanatical Neptunists still doubt this, 
we would bring up the case of the Creux-du-Vent, asking the 
question, where did the water come from, which could hollow out 
such a splendid cirque .” A. Jaccard says of these transverse val- 
leys, — “Although the water no doubt contributed to their 
