THE ORIGIN OF MOUNTAINS. 
55 ' 
Folded Mountains. 
The Swiss mountains, however, belong to another 
class, and have a very different character. They are 
greatly folded and compressed (see Figs. 23-26). 
Fig. 1 represents the Cascade of Arpenaz in the 
valley of the Arve. It shows a grand arch, but does 
not include the whole fold, which takes the form of 
an S, the middle part only being included in the 
photograph. 
It used to be supposed that mountains were up- 
heaved by forces acting more or less vertically from 
below upwards, and the igneous rocks which occupy 
the centre of mountain ranges were confidently ap- 
pealed to in support of this view. It must be con- 
fessed that when we first visit a mountainous region, 
this theory seems rational and indeed almost self- 
evident. It is now, however, generally admitted that 
such an explanation is untenable; that the igneous 
rocks were passive and not active; that, so far fiom 
having been the moving force which elevated the 
mountains, they have themselves been elevated, and 
that this took place long after their formation. Near 
the summit of the Windgalle, in the Reuss district, 
is, for instance (Fig. 24), a mass of Porphyry. Ihe 
eruption of this Porphyry must have taken place be- 
