122 THE ICE A(JE IX CANADA. 



far below water, would tend to sliow that the weisj^ht and 

 mass of tlie ice-cap was such as to enable it to remain a,- 

 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 Hud any phenomena 

 requiring long action at this period. The water in retreat 

 must have rearranged to some extent a part of tlic 

 surface-materials. The (piartzite-drift of the third steppe 

 was probaljly more uniforndy spread at this time, and a 

 part of the surface seul]>ture of the drift-deposits of the 

 second plateau may have been produced. It seems certain, 

 liowever, tliat the llocky mountains still held compara- 

 tively small glaciers, and that the I.aurentian region on 

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

 at least a short time. The closing e])isode of the glacial 

 period in tins regi(jn was the formation of the great fresli- 

 water lake uf the Ifcd Kiver \alley, or first prairie-level 

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

 of the river-courses. 



" It must not l)e concealed that there are difficulties yet 

 unaccounted for bv the theory of the glaciation and 

 deposit of drift on tlie ])lains by icebergs ; and chief 

 among these is the absence, wherever I have examined 

 the deposits and elsewhere (ner 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 ])l{v'ns and 

 llocky 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 tlie northern part of the second prairie escarpment. 



