DIRECTION OF ITS DRIFTS. 241 



in the deeper and warmer waters. In consequence of the 

 long subsidence and gradual re-elevation of the land, the 

 results of the terrestrial and sea-floated ice would become 

 commingled ; and hence one great source of the difficulty 

 attending the interpretation of the phenomena of the glacial 

 epoch. He, therefore, that would read aright the ice-epoch, 

 must restrict himself to no limited theory, but must grasp 

 broadly the consequences of a general glacialised condition, 

 calling in alike the aid of terrestrial and marine ice, and 

 ascribing to both what he cannot clearly determine as 

 having been performed by either. 



Another question that has given rise to much discussion, 

 is the direction in which the ice has generally moved, and 

 the source or sources from which the debris has been borne. 

 In the north of Europe the set seems to have been from 

 the north or a little west of north, so that the rocks torn 

 from the Scandinavian mountains have been scattered over 

 the plains of Denmark and Germany. In the British 

 Islands, the set seems also to have been from the north and 

 north-west, so that boulders from the Grampians are strewn 

 over the Lowlands, and blocks from the Cumberland hills 

 over the valleys of Yorkshire. In North America too, the 

 general float or trend has been, in like manner, from the 

 north, or from directions between the north and north-west 

 hence the appropriateness of the term " northern drift " 

 when applied to the erratic blocks that now lie scattered so 

 far and wide from their native sources. But in most coun- 

 tries the land-ice has moved in accordance with the general 

 slopes of the land or the trends of its principal valleys ; 

 hence the glacial gougings and groovings radiate in all 

 directions from some main eminence, or lie chiefly in one 

 way, according to the bearing of the valley down which the 

 ice has descended. A great deal of minute but worthless 

 labour has indeed been spent on this subject. The grooves 



Q 



