THE GEOLOGICAL HISTORY OF THE COLONY 459 



bent surface of denudation, and that the position of the 

 coast roughly marks the axis about which the bending 

 has taken place. He shows how the variation in level 

 of the axis, lying either just above or below that of the 

 sea, would account for the presence of such apparently 

 contradictory phenomena as drowned valley sand raised 

 beaches in one and the same district. This suggestion 

 certainly throws light on many of the coastal phenomena 

 from the Olifant's Eiver round the south coast to the 

 Natal border, of which the geology is known in at least 

 its outlines. For a thorough discussion of the sugges- 

 tion as regards the Cape Colony coast, more information 

 is required about the thickness of the sediments lying 

 on the bed rock of the river channels in their lower 

 courses, and about the slopes of, and deposits on, the 

 coastal terraces. 



