Foerste.J 
404 
[April 6, 
ing. On the other hand, at the north end of this cluse there is 
marked evidence that the beds are unfraetured ; the rocks which 
have been fairly horizontal for some distance suddenly dip at an 
angle of about 50 degrees towards the north, and farther north, 
where the corresponding strata on opposite sides of the gorge are 
shown within 100 feet of each other and perfectly in line, the rocks 
are vertical, and a little farther north, even a little overturned. 
At the south end of the Pery cirque the rocks on either side ap- 
proach to within a short distance of each other, their dip is strongly 
to the south, perhaps 65 degrees, but the strata are perfectly in 
line. It is necessary at the mouths of cirques to avoid being mis- 
led by the fact that subsequent erosion may have removed here a 
certain thickness of strata on one side of the valley, while on the 
opposite side a smaller amount of erosion may have taken place, 
and hence a real concordance of strata may have in appearance 
become discordant. There is every evidence of accordance in this 
beautiful cirque until the northern mouth is reached when a slight 
discordance is at once noted. The strata on the west side have a 
somewhat lower altitude than those on the east side. It is evident 
that this is caused by several longitudinal faultings on the west side 
lowering the strata there. These faults are made up on the east side 
by a single large fault which gave rise to the hill which projects 
quite a distance north of the line of strike shown by the strata on 
the west side. The facts here indicate a crack transverse to the 
fold, but the strict accordance in the strata over the remainder of 
the cirque at once assigns these facts simply to local causes of 
limited importance. Between Tavannes and Sonceboz is a 
cirque whose importance as such does not seem to have been 
recognized in geological literature. The absence of a stream trav- 
ersing it and to which its origin or at least its subsequent 
enlargement might be attributed, was no doubt to large extent the 
cause of this. Moreover the outlines of this cirque as recorded 
on the topographical maps, without the marked assistance to the 
eye given by the rock outcrops which actually exist in nature, do 
not readily suggest its character as a cirque. And yet the traveller 
who traverses it on foot at once discerns the similarity to 
the broader cirques he has seen elsewhere in the Jura, and if he 
be a geologist he sees at once that an active stream must have 
once traversed the gorge and must have carried away in its 
drainage the vast amount of material represented now by the 
