258 Gravel-Terraces of Coquimbo paeth. 



emerged; but in the upper parts of the bay it is 

 supposed soon to have lost this power, owing to the more 



No. 25. 



_J 



protected situation and to the quantity of detritus 

 brought down by the river ; consequently low land was 

 there accumulated. As this low land was formed during 

 a slow elevatory movement, its surface will gently slope 

 upwards from the beach on all sides. Now, let us 

 imasrine the bav, not to make the diagram, more com- 



O *f * CD 



plicated, suddenly converted into a valley : the basal 

 line of the cliffs will of course be horizontal, as far as 

 the beach is now seen extending in the diagram; but 

 in the upper part of the valley, this line will be higher, 

 the level of the district having been raised whilst the 

 low land was accumulating at the foot of the inland 

 cliffs. If, instead of the bay in the diagram being 

 suddenly converted into a valley, we suppose with much 

 more probability it to be upraised slowly, then the 

 waves in the upper parts of the bay will continue very 

 gradually to fail to reach the cliffs, which are now in 

 the diagram represented as washed by the sea, and 



