:284 THE CANADIAN NATURALIST. [Vol. vii. 



until they are prepared to admit that the power of the heavy- 

 Arctic currents passing over the submerged land and carrying 

 with them their burden of ice, is vastly greater as an agent 

 of denudation than either the rivers or glaciers. Nor must we 

 conjfine this to the Post-pliocene period. Prof. Hall has shewn 

 that the whole of the vast thickness of the Palasozoic rocks of 

 •the Appalachians may be attributed to the carrying power of the 

 same currents which are now piling up banks of Arctic sand and 

 stones along the American coast. Nay more, the history of the 

 land of the Northern Hemisphere throughout geological time 

 has been that of a series of elevations and depressions or gigantic 

 pulsations of the earth's crust, so regular that we cannot hesitate 

 in referring them to some constantly operating law. Every 

 elevation exposed the land to sub-aerial disintegration. Every 

 subsidence scraped and peeled it by the action of the Arctic 

 currents, and thus the carrina;e of material and the growth of 

 the continents have ever been to the south-west. I cannot leave 

 this subject without according to Dr. Carpenter much credit for 

 contending as he has done for the reality, power, and true causes 

 of these great sub-oceanic rivers, which have played and are 

 playing so important parts as geological agents, that without 

 them it is impossible to account either for the Palasozoic deposits 

 or the Post-pliocene deposits of our North American continent. 



But it is time to turn to the second topic which I have marked 

 out for myself in this discourse. In the past summer three 

 lines of geological reconnaissance have been pushed out from the 

 Xaurentian and Huronian country of Lake Superior over the 

 plains ot Manitoba. One of these, under Mr. Selwyn, followed 

 the line of the North Saskatchewan. The second was that of 

 Prof. Bell on the south branch of the same river and its tribu- 

 taries. The third was that of Mr, G. M. Dawson on the 49th 

 parallel. All of these have been brought under the notice of 

 this Society in the course of the winter. This great western 

 plain presents first a wide expanse of Cretaceous rocks, apparently 

 not highly fossiliferous and not well exposed, but containing 

 ■some limestone layers rich in Foraminifera and Coccoliths pre- 

 cisely similar to those of the English chalk. Some of these 

 hs-ve been described by Mr. Dawson in our Journal. This is 

 :succeedsd by vast estuarine and lacustrine deposits of clay and 

 sand, holding brackish-water and fresh-water shells, and beds 

 of lignite with abundant plant remains. The general geological 



