40 HAYFORD 



been careful to distinguish sharply between the force which tends to 

 preserve the various elevations and depressions of the earth from the 

 force which tends to raise the lands and depress the sea bottoms. 

 Those two classes of forces are at work independently of each other. 

 The heavy masses of sediment which are formed upon the bottom of 

 the sea can, I conceive, only be elevated by a positive uplifting force. 

 Those portions of the land which are being denuded can only have 

 their profiles depressed by an independent process of subsidence. 

 Isostasy merely tends to keep the levels of the denuded region on the 

 one hand, and the loaded regions of the sea bottom on the other, at 

 constant levels. 



