vni 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 (7, 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 



