BELT — ON THE GLACIAL PERIOD IN NORTH AMERICA. 97 



the.' depths to which fiords have been excavated, and from the fact of 

 littoral shells having been dredged niany miles from existing coasts. 

 With regard to the submergence of tropical and sub-tropical lands, 

 it is now well established that at the same period the African Sahara 

 was covered by the waters of the ocean, so that we have an approach 

 towards the conditions required for the production of extreme cold. 

 That the conditions were all fulfilled is very improbable, indeed that 

 they were not is proved by the ice having extended much farther 

 south in North America than in Europe. 



2. Recent changes of level of the land in northern henmphere 

 greatest towards the jiole. — In a paper on some movements of the 

 earth's surface in recent times,* I have remarked that in two instances 

 in the northern hemisphere, one of depression, the other of elevation, 

 the movement is greatest towards the pole. This matter is so im- 

 portant in dealing with the question of the probability of a rise of 

 Arctic lands in the glacial epoch that I may be jjermitted to refer to 

 it again, and to supplement the argument with some additional facts 

 bearing upon it. 



It has long been known that parts of the coasts of Sweden and 

 Norway were slowly rising, and in the time of Linna;us marks were 

 made on the rocks by which the rate of elevation at diflferent points 

 has been determined. It appears that at Gottenberg in the south, 

 the land is only being raised about four inclies in a century, but that 

 the rate of motion gradually increases northwards, until at Cape Cod, 

 the extreme point where it has been measured, the land is being- 

 raised about four feet in a century. 



Opposite to this area of elevation, on the other side of the At- 

 lantic, there is a corresponding area of depression. It appears to be 

 well established thfit the Atlantic sea board of North America is 

 slowly sinking. In New England the subsidence is scarcely 

 perceptible, but it gradually increases as we proceed northwards. 

 In Nova Scotia the submergence of marsh lands and of rocks has 

 been generally remarked by the residents on the coast, and Cobe- 

 quid bay and Cumberland basin submarine forests attest the long 

 continuance of the downward motion. This subsidence attains its 

 maximum on the west coast of Greenland, where the land is so rapidly 

 sinking that in quite recent times the settlers have had to move 



*These Transactions, vol. I, Part I, p. 2i. 



