VIII RIVERS AND LAKES 297 
for a certain distance in the direction of the 
main axis, so often break away into lateral 
valleys? If the elevation of a chain of moun- 
tains be due to the causes suggested in p. 214, 
it is evident, though, so far as I am aware, 
stress has not hitherto been laid upon this, 
that the compression and consequent folding 
of the strata (Fig. 41) would not be in the 
direction A B only, but also at right angles to 
it, in the direction A C, though the amount of 
folding might be much greater in one direc- 
tion than in the other. Thus in the case of 
Switzerland, while the main folds run south- 
west by north-east, there would be others at 
right angles to the main axis. The complex 
structure of the Swiss mountains may be 
partly due to the coexistence of these two 
directions of pressure at right angles to one 
another. The presence of a fold so originating 
would often divert the river to a course more 
or less nearly at right angles to its original 
direction. | 
Switzerland, moreover, slopes northwards 
from the Alps, so that the lowest part of the 
great Swiss plain is that along the foot of 
