172 



GEOLOGY. 



its antecedent course across areas which have been uplifted (differen- 

 tially) hundreds and even thousands of feet.^ Some of the striking 



Figs. 163, 164. — Piracy stimulated by warping. Uplift along axis 1-2. 



scenic features of this noble valley are the result of these changes in 

 the country through which it flows. A lesser stream would have been 



1 Russell. Rivers of North America, p. 279. 



