No. 1.] DAWSON — POST-PLIOCENE. 33 



clay whicli intervenes between Lake Ontario and Georgian Bay. 

 Lake Erie may have been cut by the flow of the upper layers of 

 water over the Middle Silurian escarpment ; and Lake Michigan, 

 though less closely connected with the direction of the current, 

 is, like the others, due to the action of a continuous eroding force 

 on rocks of unequal hardness." 



" The predominant southwest striatiou, and the cutting of the 

 upper lakes, demand an outlet to the west for the Arctic current. 

 But both during depression and elevation of the land, there must 

 have been a time when this outlet was obstructed, and when the 

 lower levels of New York, New England, and Canada were still 

 under water. Then the valley of the Ottawa, that of the Mohawk, 

 and the low country between Lakes Ontario and Huron, and the 

 valleys of Lake Champlain and the Connecticut, would be straits 

 or arms of the sea, and the current, obstructed in its direct flow, 

 would set principally along these, and act on the rocks in north 

 and south and northwest and southeast directions. To this por- 

 tion of the process I would attribute the northwest and southeast 

 striatiou. It is true that this view does not account for the 

 southeast striae observed on some high peaks in New England ; 

 but it must be observed that even at the time of greatest depres- 

 sion, the Arctic current would cling to the northern land, or be 

 thrown so rapidly to the west that its direct action might not 

 reach such summits." 



" Nor would I exclude altogether the action of glaciers in eastern 

 America, though I must dissent from any view which would 

 assign to them the principal agency in our glacial phenomena, 

 under a condition of the continent in which only its higher peaks 

 were above the water, the air would be so moist, and the tempera- 

 ture so low, that permanent ice may have clung about mountains 

 in the temperate latitudes. The striatiou itself shows that there 

 must have been extensive glaciers as now in the extreme Arctic 

 regions. Yet I think that most of the alleged instances must be 

 founded on error, and that old sea-beaches have been mistaken 

 for moraines. Even in the White Mountains the action of the 

 ocean-breakers is more manifest than that of ice almost to their 

 summits; and though I have observed in Canada and Nova 

 Scotia many old sea-beaches, gravel-ridges, and lake-margins, I 

 have seen nothing that could fairly be regarded as the work of 

 glaciers. The so-called moraines, in so far as my observation 

 extends, are more probably shingle beaches and bars, old coast- 

 VoL, VI. c No. 1. 



