262 THE BEAUTIES OF NATURE CHAP. VII 
Thus many a mountain valley gives some 
such section as the following. 
Fig. 27. —.A, present river valley; B, 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. 
