122 THE ICE AGE IN CANADA. 



far below water, would tend to show that the weight and 

 mass of the ice-cap was such as to enable it to remain as 

 a glacier till submergence was very deep. 



" The emergence of the land would seem to have been 

 more rapid ; or, at least, I do not find any phenomena 

 requiring long action at this period. The water in retreat 

 must have rearranged to some extent a part of the 

 surface-materials. The quartzite-drift of the third steppe 

 was probably more uniformly spread at this time, and a 

 part of the surface sculpture of the drift-deposits of the 

 second plateau may have been produced. It seems certain, 

 however, that the Kocky mountains still held compara- 

 tively small glaciers, and that the Laurentian region on 

 its emergence was again clad to some extent with ice, for 

 at least a short time. The closing episode of the glacial 

 period in this region was the formation of the great fresh- 

 water lake of the Eed Eiver valley, or first prairie-level 

 (which was only gradually drained), and the re-excavation 

 of the river-courses. 



" It must not be concealed that there are difficulties yet 

 unaccounted for by the theory of the glaciation and 

 deposit of drift on the plains by icebergs ; and chief 

 among these is the absence, wherever I have examined 

 the deposits and elsewhere over the West, of the remains 

 of marine mollusca or other forms of marine life. With 

 a submergence as great as that necessitated by the facts, 

 it is impossible to explain the exclusion of the sea ; for, 

 besides the evidence of the higher western plains and 

 Ilocky mountains, there are terraces between the Lake of 

 the Woods and lake Superior nearly to the summit of the 

 Laurentian axis, and corresponding beach-marks on the 

 face of the northern part of the second prairie escarpment. 



