276 Canadian Record of Science. 



this glacier must, in many places, have exceeded a mile in 

 thickness. The reasons above stated appear, however, suffi- 

 cient to compel us to seek for some other explanation of the 

 observed facts, however difficult this may at first sight 

 appear. With a depression such as we know to have existed, 

 admitting the Arctic currents along the St. Lawrence Valley, 

 through gaps in the Laurentian watershed, and down the 

 great plains between the Laurentian areas and the Rocky 

 Mountains, we can easily understand the covering of the 

 hills of Eastern Canada and New England with ice and snow, 

 and a similar covering of the mountains of the west coast. 

 The sea also, in this case, might be ice-laden and boulder- 

 bearing as far south as 40°, while there might still be low 

 islands far to the north on which vegetation and animals 

 continued to exist. We should thus have the conditions 

 necessary to explain all the anomalies of the glacial deposits. 

 Even the glaciation of high mountains south of the St. 

 Lawrence Valley would then become explicable by the 

 grounding of ice on the tops of these mountains when reefs 

 in the sea. In like manner we can understand how on the 

 isolated trappean hill of Beloeil, in the St. Lawrence 

 Valley, Laurentian boulders, far removed from their native 

 seats to the north, are perched at a height of 1,200 feet on a 

 narrow peak where no glacier crald possibly have left them. 

 The so-called moraine, traceable from the great Missouri 

 Coteau in the west, to the coast of New Jersey, would thus 

 become the mark of the western and southern limit of the 

 subsidence, or of the line along which the cold currents 

 bearing ice were abruptly cut off by warm surface waters. 

 I am glad to find that these considerations are beginning to 

 have weight with European geologists in their explanation 

 of the glacial drift of the great plains of Northern Europe. 



Whatever difficulties may attend such a supposition, they 

 are small compared with those attendant on the belief in a 

 continental glacier, moving without the aid of gravity, and 

 depending for its material on the precipitation taking place 

 on the interior plains of a great continent. 



I have elsewhere endeavoured to show, on the evidence 

 found in Canada, that the occurrence of marine shells, land 



