1868.] 



131 



[Shaler. 



and the advance of the sea lipe towards the land.^ The remaining con- 

 dition (Fig. 2) would be always accompanied by the apparent elevation 



1 In the diagrams 1 and 2, similar letters denote corresponding points. 



In figures 1 and 2, the straight lines A, B, A'', B' are diagrammatic expressions 

 for sections extending across the shore. For convenience of delineation, the action 

 of the movement of the small segments of the crust represented is supposed to be 

 like that of a rigid bar. 



Fig. 1. 



In Fig. 1, the pivot point, P, is to the landward of the shore, S, the line A, B, 

 indicating the surface of the continent near the coast. Let the depression of the 

 sea floor and the elevation of the land go on until the continent-il surface is in 

 the position indicated by the lines A', V>' , and the sliore will be removed to the 

 point S', and the sea gains. S, L indicates the sea level. If we suppose, liowever, 

 that the dotted line P, L^, denotes the sea level, then the pivot point will fall just at 

 the shore line, and all the changes in the position of the line A, B, will not affect 

 the position of the water lines. 



T\z. 2 



In Fig. 2, the pivot point is the seaward of the shore line A, B, indicating the 

 original position of the continental surface, and A^, B', the position of the change. 

 Inspection will show that in this diagram the change has caused the shore to move 

 seaward, and the land gains. 



Fig. 3 represents a shore line with an axis of rotation, A, B, cutting it in such a 



Fi.ff. ;^. 



