224: MAN AND THE GLACIAL PERIOD. 



We are not permitted, however, to assume that there 

 have been no changes of level since the deposition of these 

 beaches surrounding the ancient glacial Lake Erie- Ontario. 

 On the contrary, there appears to have been a considerable 

 elevation towards the east and northeast in post-glacial 

 times. The highest ridge south of Lake Erie, which at 

 Fort Wayne is about 780 feet high, is now about 795 feet 

 in Lorain County. The second of the ridges above men- 

 tioned, which is about 740 feet above tide at Cleveland, 

 Ohio, rises to 870 feet where the last traces of it have been 

 discovered at Hamburg, 1ST. Y. The third ridge, which is 

 673 feet at Cleveland, has risen to the height of 860 feet 

 at Crittenden, about one hundred miles to the east of 

 Buffalo, 1ST. Y. 



A similar eastern increase of elevation is discoverable 

 in the main ridge surrounding Lake Ontario. What Pro- 

 fessor Spencer calls the Iroquois beach, which is 363 feet 

 above tide at Hamilton, Ontario, has risen to a height of 

 484 feet near Syracuse, X. Y. ; while farther to the north- 

 east, in the vicinity of Watertown, it is upwards of 800 

 feet above tide. 



There is also a similar northward increase of elevation 

 in the beaches surrounding the higher lands of Ontario 

 eastward of Lake Huron and Georgian Bay. 



All this indicates that at the close of the Glacial period 

 there was a subsidence of several hundred feet in the area 

 of greatest ice accumulation lying to the east and north of 

 the Great Lake region. The formation of these ridges 

 occurred during that period of subsidence. The re-eleva- 

 tion which followed the disappearance of the ice of course 

 carried with it these ridges, and brought them to their 

 present position.* 



In returning to consider more particularly the remark - 



* See Spencer, in Bulletin of the Geological Society of America, 

 vol. ii, pp. 465-476. 



