VALLEY OF THE ST. LAWRENCE. 177 



the older rocks in the west were subsequently overlaid by 

 the new deposits. However that may be, the occurrence 

 of the chalk fossils and tertiary deposits in their present 

 position and altitude clearly indicates that the elevation of 

 the Rocky Mountain chain was one of the latest of the great 

 movements that have occurred in this continent. It is to 

 the westward of these mountains only, along the Pacific 

 coast, and in the peninsula of Alaska*, and the Aleutian 

 chain of islands, that recent volcanic action can be traced. 

 The existence of coal measures, containing ferns and 

 other plants of a tropical character, in Jameson's Land 

 and Melville Island, in the high latitudes of 71° and 

 75°, is a curious fact, to be accounted for by those who 

 theorise on the ancient condition of the surface of the 

 earth ; and the vast accumulations formed at a later epoch 

 in the Siberian Sea and Kotzebue's Sound, of fossil bones 

 of mammoths, rhinoceri, and other animals which do not 

 exist in arctic regions at the present day, and the pre- 

 servation to this date of some of their undecomposed car- 

 cases, are equally interesting facts, which need explanation. 



VALLEY OF THE ST. LAWRENCE. 

 The first in order of the great transverse excavations, and 

 the grandest, is the basin of the St. Lawrence, which has 

 a length equal to the whole course of the Mackenzie, and 

 contains by far the greatest accumulation of fresh water in 

 the world. It has no connection with the drainage of the 

 prairie slopes in the same parallels, which is performed by 

 the Missouri and its numerous affluents on one side, and 

 on the other by the Saskatchewan and its tributaries, 

 aided by the upper feeders of the Mackenzie. It differs 

 from the three great lacustrine basins which succeed it, in 



* Spelt thus, and also Alashka in Cook's Third Voyage. The 

 French and Russian authors write the word Aliaschka. 



VOL. II. N 



