Smith.] 



Some Aspects of Erosion. 



167 



with gentler slopes, in the foreground, are of a readily weathered 

 sandstone, while near the center of the background may be seen a 

 hill with steeper slopes, formed from more resistant cherts. 



Figure 1. — View in the Coast Range of California, showing difference in slope clue to difference 

 in the character of the rocks. 



On a single graded slope formed in rocks of varying degrees of 

 resistance, or in a non- homogeneous rock, those parts formed in 

 the most resistant rock will have the greatest angle, those formed 

 in the least resistant, the least angle. Such a slope is a composite 

 graded slope. 



C A G B 



Figure 2. — Diagram to illustrate adjustment of drainage in rocks of varying degrees 

 of resistance. 



If we consider two slopes of equal altitude (EG, Fig. 2) and 



