No. 4.J CLAYPOLE — PRE-GLACIAL GEOGRAPHY. 195 



infer that its bottom lies nearly or quite as low as that of the 

 lake, so that in the later Tertiary age before it was filled with 

 clay and sand, the waters of the Ontarian valley must have 

 found their way by Oswego, Syracuse, Rome, Utica and Albany 

 to the sea. The present lake basin, therefore, like those of 

 Lakes Erie and Huron, must have formed an open valley drained 

 by the river whose upper course was pointed out above, and 

 which, considering its lower course, we may well christen the 

 "Pre-Glacial Mohawk." 



An objection will here be raised which must be met. The 

 bed of Lake Ontario lies 215 feet below the present level of the 

 Atlantic, while the bed of Lake Erie is 330 feet* above it, conse- 

 quently, while there is no obstacle to the flow of this ancient 

 Mohawk from the Erie to the Ontarian valley, it will be impos- 

 sible to explain its course from the latter to the sea. A like 

 difficulty is found in establishing the flow of the river from the 

 Huron basin into that of Lake Erie, the bed of the former lying 

 230 feet below the Atlantic level, while that of the latter is 330 

 feet above it, giving an ascent of more than 500 feet. If the 

 relative levels of sea and land were then as they are now, such a 

 course for this pre-glacial river was impossible. But there is 

 much reason to believe that before the coming on of the great 

 ice age the present relative levels of land and sea did not exist. 

 It is the opinion of many geologists, among whom we may men- 

 tion Professor Dana, that the glacial era was a time of conti- 

 nental elevation in high northern latitudes, and that this eleva- 

 tion became less and less towards the equator. But what- 

 ever may have been the case at and before its commencement, it 

 is more probable that during the ice age the land to the north 

 underwent depression in relation to the sea, whether the result 

 of a rise in the ocean waters or not" may be left for the present 

 undetermined. Be this however as it may, most geologists are 

 agreed that before the ice age, during the later Tertiary and 

 early Quaternary eras, the northern part of the continent was 

 more elevated than now. 



" The Atlantic coast of North America to the north of Cape 

 Cod was higher than now during the Cretaceous and Tertiary 

 eras, as is shown by the absence of sea-shore deposits of these 

 eras." Dana's Manual, 1874, p. 540. 



* In these figures no account is taken of the recent deposits in the 

 beds of the lakes. 



