290 THE BEAUTIES OF NATURE CHAP, 
downhill. He imagined that the downward 
slope had a fall of about 40 or 50 feet per- 
pendicular. We here have unequivocal evi- 
dence that a ridge had been uplifted right 
across the old bed of a stream. From the 
moment the river course was thus arched, 
the water must necessarily have been thrown 
back, and a new channel formed. From that 
moment also the neighbouring plain must 
have lost its fertilismg stream, and become 
a desert.’’* 
The strata, moreover, often — indeed gener- 
ally, as we have seen, for instance, in the case 
of Switzerland—pbear evidence of most vio- 
lent contortions, and even where the convul- 
sions were less extreme, the valleys thus 
resulting are sometimes complicated by the 
existence of older valleys formed under pre- 
vious conditions. 
In the Alps then the present configuration 
of the surface is mainly the result of denuda- 
tion. If we look at a map of Switzerland 
we can trace but little relation between the 
river courses and the mountain. chains. 
1 Darwin’s Voyage of a Naturalist. 
