262 THE BEAUTIES OF NATURE chap, vn 



Thus many a mountain valley gives some 

 such section as the following. 



B 



A 



Fig. 27. — A, present river valley; 5, old river terrace. 



First, a face of rock, very steep, and in 

 some places almost perpendicular; secondly, 

 a regular talus of fallen rocks, stones, etc., 

 as shown in the view of the Rhone Valley 

 (Fig. 26), which takes what is known as the 

 slope of repose, at an angle which depends 

 on the character of the material. As a rule 

 for loose rock fragments it may be taken 

 roughly to be an angle of about 45°. Then 

 an irregular slope followed in many places 

 by one or more terraces, and lastly the 

 present bed of the river. 



