202 THE CANADIAN NATURALIST. [Vol. Vlii. 



valley of the present Hudson, and reached the Atlantic some- 

 where to the south-east of New York harbour, after a course of 

 nearly 1000 miles, while its former tributary, the Hudson, ap- 

 pears to have drained the district whose waters now find an out- 

 let to the Lower St. Lawrence. In the west the broad open 

 vales of Superior and Michigan poured forth their waters to the 

 south to meet the great Midland River of the Continent, the 

 Mississippi, while the waters of the Georgian Bay instead of 

 communicating, as at present, with Lake Huron, flowed directly 

 into the Ontarian valley somewhere along the line of the present 

 Ottonnabee. 



From the position maintained in the present paper, several 

 facts otherwise difficult of explanation, become consistent with 

 one another, and are, in fact, necessary consequences of the 

 principle here laid down. The great depth of the lakes to the 

 northward is a result of the previous elevation and subsequent 

 depression, which we have assumed as the basis of our reasoning. 

 The almost uniform descent in the channel of the pre-glacial 

 Mohawk from the valley of Lake Huron to New York harbour 

 would be restored if elevation to the same amount should again 

 take place and the accumulation of drift be removed. The 

 shallowness of Lake Erie at its western end is a consequence of 

 its southerly position which lessened the depression it has since 

 undergone. It increases in depth to the north-east. Ontario is 

 deeper than Erie, while the three upper lakes extending much 

 farther to the north are also considerably deeper, because of the 

 greater subsidence their basins have since experienced.* 



Another fact which this principle explains is the excavation 

 of many part of these channels below the level of the sea. The 

 bottoms of lakes Superior, Michigan, Huron and Ontario, are all 

 more than 200 feot below the surface of the Atlantic- The 

 same is true of the buried channel under Lake Onondaga, and 

 also t oa less degree of several places in the present Hudson River. 



There is no evidence that cataracts ever existed to scoop out 

 these basins, and with one exception no other agent has ever 

 been brought forward to explain their formation. That agent is 

 ice, and to it some writers are disposed to attribute effects which 

 the evidence fails to support. We have already alluded to the 



* A similar explanation may be given of the great depth of the 

 bed of the Saguenay and the lower St. Lawrence. 



