PHYSICAL CONDITIONS— POSTGLACIAL. 525 



waves had sufficient time to cut the rocks back so as to form 

 conspicuous platforms between high- and low- water marks. Now 

 and again, it is true, these may be observed, but it is only in 

 cases where the rocks, by reason of their composition or struc- 

 ture, have lent themselves more readily to the action of the sea. 

 As one boats along the rocky shores all the phenomena seem sug- 

 gestive of a very recent loss of land, and the inference I would 

 make is simply this, that the movement of depression which 

 separated Iceland and Greenland from Europe has continued, 

 with perhaps no interruption, from the genial postglacial epoch to 

 the present day. I have not forgotten the important fact that 

 the postglacial submergence carried down Central Scotland for 

 some 50 feet or so below its present level, and that the regaining 

 of this belt of coast-land from the sea would seem to indicate 

 not only an interruption of the great northern depression, but a 

 movement in the opposite direction. It is not so certain, how- 

 ever, that our later raised-beaches owe their origin to earth- 

 movements. M. Adhemar and Dr. Croll have shown that the 

 sea-level may rise without any movement of the land itself. 

 They have pointed out that a great accumulation of ice in 

 northern regions, such as that which characterised the glacial 

 epochs, would of itself cause a rise of the sea by displacing the 

 earth's centre of gravity, and it is quite possible, as Dr. Croll 

 has suggested, that some of our recent raised-beaches may indi- 

 cate periods when the ice of north polar regions attained a con- 

 siderable augmentation, while, at the same time, the ice of the 

 Antipodes suffered a corresponding diminution. Now, it is the 

 fact, as I have proved, that the climate of Scotland during the 

 50-feet-beach was considerably colder than it is now; and I 

 believe that this will be found to hold true of a much wider 

 area. It is therefore quite possible, as already remarked, that 

 the great northern depression may have been going on without 

 interruption from the genial postglacial epoch down to our own 

 era — the more recent raised-beaches being likely enough due to 

 oscillations of the sea-level itself, and not necessarily to move- 

 ments of the land. 



