chap. ix. not Horizontal. 257 



necessarily must be horizontal, if the elevation has been 

 horizontal. But here is a fallacy : for after the sea has, 

 during a cessation of the elevation, worn cliffs all round 

 the shores of a bay, when the movement recommences, 

 and especially if it recommences slowly, it might well 

 happen that, at the exposed mouth of the bay, the 

 waves might continue for some time wearing into the 

 land, whilst in the protected and upper parts successive 

 beach-lines might be accumulating in a sloping surface 

 or terrace at the foot of the cliffs which had been lately 

 reached : hence, supposing the whole line of escarpment 

 to be finally uplifted above the reach of the sea, its 

 basal line or foot near the mouth will run at a lower 

 level than in the upper and protected parts of the bay ; 

 consequently this basal line will not be horizontal. And 

 it has already been shown that the summit-edges of 

 each escarpment will generally be higher near the 

 mouth (from the seaward sloping land being there most 

 exposed and cut into) than near the head of the bay ; 

 therefore the total height of the escarpments will be 

 greatest near the mouth ; and further up the old bay 

 or valley they will on both sides generally thin out and 

 die away : I have observed this thinning out of the 

 successive escarpment at other places besides Coquimbo ; 

 and for a long time I was quite unable to understand 

 its meaning. The following rude diagram will perhaps 

 render what I mean more intelligible ; it represents a 

 bay in a district which has begun slowly rising. Before 

 the movement commenced, it is supposed that the 

 waves had been enabled to eat into the land and form 

 cliffs, as far up, but with gradually diminishing power, 

 as the points A A: after the movement had commenced 

 and gone on for a little time, the sea is supposed still to 

 have retained the power, at the exposed mouth of the 

 bay, of cutting down and into the land as it slowly 



