Foerste.J 
402 
[April 6, 
M. Bertrand states that various cluses in the vicinity of Morez in the 
southwestern Jura owe their origin to the existence of horizontal 
displacements or faults. By this he probably means that such 
horizontal displacements would give rise to breaks in the barriers 
formed by the folds, the greatest heights of the folds not being 
continuous at such faults, but shifted laterally, permitting lower 
passages of escape between to the waters dammed back by the 
folds. This idea is more clearly expressed by La Noe and 
Margerie. A. Philippson conceives the folding of the Jura to have 
given rise to a series of lakes occupying the synclinal valleys and 
the split anticlinal combes. The lakes discharged their waters at 
the lowest points offered by their barriers. Erosion increased the 
depressions thus formed, and finally gave rise to the cross valleys 
so characteristic of the Jura river systems, after the formation of 
which, lakes could no longer exist. La Noe and Margerie restate 
Philippson’s theory in an amplified and clearer form. Lakes are 
supposed to be formed behind the folds, their overflow longitudin- 
ally being prevented by the joining of the folds under acute 
angles, while lower crests along the folds would determine their 
place of overflow transversely. The depressions in these folds be- 
ing considered of orographic nature, it seems natural that they 
should be repeated in a direction transverse to the trend of the 
mountains and in several of the adjacent folds. The cases 
of the Birse and Some are mentioned in illustration of such an 
origin. The origin of the cluse or cirque at Morez from a horizon- 
tal fault as exjdained by Bertrand is also more clearly stated and a 
figure is added illustrating the principles involved. According to 
this it is unnecessary that the lakes dammed up behind the folds 
should reach the level of these folds before beginning their over- 
flow, because by the horizontal displacement of the folds along 
some fault, a lower horizon is obtained between the disjointed 
ends, and a smaller accumulation of water is necessary to start the 
overflow. The authors also show that by the weathering of the 
tops of the folds and the carriage of the waste materials into the 
valleys between, both the height of the folds would be diminished, 
and the relative elevation of the bottom of the valleys increased. 
The combined result would be to diminish the amount of water 
necessary to be accumulated before overflow sets in. A. Penck 
states that many a cluse in the Jura may have been formed by 
subterranean streams widening their channels until the covering 
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