THE ORIGIN OF MOUNTAINS. 
51 
the original watershed be cut into detached summits, 
but secondary ridges would be formed approximately 
at right angles, to be again cut into detached summits 
like the first. 
The general opinion of geologists used, however, 
to be, in the words of Sir R. Murchison, that “most 
of the numerous deep openings and depressions 
which exist in all lofty mountains were primarily due 
to cracks which took place during the various move- 
ments which each chain has undergone at various 
periods.” 
In support of this view such gorges as those of 
Pfaffers, the Trient, the Gorner, the Aar, etc., were 
quoted as conclusive cases, but even these are now 
proved to have been gradually cut down by running 
water. 
The rapidity of denudation is of course affected 
greatly by the character of the strata, so that the 
present level depends partly on the original con- 
figuration, partly on the relative destructibility of the 
rock. The existing summits are not those which 
were originally raised the highest, but those which 
have suffered the least. And hence it is that so 
many of the peaks stand at about the same level. 
Everyone who has ever stood at the top of such a 
mountain as the Piz Languard, which I name as 
4 * 
