256 Gravel-Terraces of Coquimbo part h. 



of cliff or escarpment, neither its summit-edge nor its 

 base is horizontal. On the theory of the terraces having 

 been formed during a slow and equable rise of the land, 

 with as many intervals of rest as there are escarpments, 

 it appears at first very surprising that horizontal lines 

 of some kind should not have been left on the land, 



The direction of the diagonal inclination in the 

 different terraces being different, — in some being direc- 

 ted more towards the middle of the vallev, in others 

 more towards its mouth, — naturally follows on the 

 view of each terrace, beins: an accumulation of successive 

 beach-lines round bays, which must have been of dif- 

 ferent forms and sizes when the land stood at different 

 levels : for if we look to the actual beach of a narrow 

 creek, its slope is directly towards the middle ; whereas, 

 in an open bay, or slight concavity on a coast, the slope 

 is towards the mouth, that is, almost directly seaward ; 

 hence as a bay alters in form and size, so will the direc- 

 tion of the inclination of its successive beaches become 

 changed. 



If it were possible to trace any one of the many 

 beach-lines, composing each sloping terrace, it would 

 of course be horizontal ; but the only lines of demarca- 

 tion are the summit and basal edges of the escarpments. 

 Xow the summit-edge of one of these escarpments 

 marks the furthest line or point to which the sea has 

 cut into a mass of gravel sloping seaward ; and as the 

 sea will generally have greater power at the mouth than 

 at the protected head of a bay, so will the escarpment 

 at the mouth be cut deeper into the land, and its 

 summit-edge be higher ; consequently it will not be 

 horizontal. "With respect to the basal or lower edges 

 of the escarpments, from picturing in one's mind ancient 

 bays entirely surrounded at successive periods by cliff- 

 formed shores, one's first impression is that they at least 



