417 
[Foerste. 
1S92.J 
So much has been eroded from the tops and flanks of the folds 
that it is difficult at the present time to state what happened 
during folding. It is certain that there is no evidence at the 
present time of open cracks along the crests of the folds, in their 
present state of denudation. At the beautiful cross-sections pro- 
vided by the cirques no such longitudinal open cracks could be 
observed. Such cracks, however, may have existed at an earlier 
stage of the history of Jura folding. In these cracks streams 
may have been located, but it is certain that subsequent denuda 
tion has in that case cut down below the level to which the 
cracks extended, and has enlarged the original open cracks into 
broad valleys. 
If, however, it be remembered that the Cretaceous strata which 
once capped the Bernese Jura folds are softer and were prob- 
ably more plastic than the Jurassic, and that the Tertiary strata 
were still more plastic, it seems more probable that the upper 
strata managed to accommodate themselves to the curvatures pro- 
duced by folding in the lower strata, without the intervention of 
open ruptures. Still the existence of cracks in these more recent 
strata, now removed from the folds, cannot be denied. 
17. Capturing of Streams. In the backward erosion of the 
headwaters of a stream it is evident that one stream may often 
tap the other at various points along its course, and turn all 
the waters above this point of tapping into its own channel. 
This may have occurred in case of some of the Jura streams, but 
the evidence of such capturing in the Bernese Jura is not suffi- 
ciently clear, or the observations in the field were not extended 
enough, to bring to light unequivocal typical cases. Possibly 
the head waters of the Raus south of the Cremine cirque may 
represent such a case of capture. This would not agree well 
with some of the views previously expressed since in that case 
the formation of the Cremine cirque would probably have to be 
ascribed in large part to backward erosion and not to antecedent 
streams. 
18. Summary. The chief streams of the Bernese Jura follow 
consequent synclinal valleys for the most part ; but they fre- 
quently pass from one synclinal valley to another by transverse 
cirques , which seem to be persistent courses of streams that 
flowed here antecedent to the folding of the region. The general 
PROCEEDINGS B. S. N. H. VOL. XXV. 27 Aug. 1892. 
