30 THE ICE AGE IN CANADA. 



The lower boulder clay (/) is often a true and very 

 hard till, resting usually on intensely glaciated rock- 

 surfaces, and filled with stones and boulders. Where 

 very thick, it can be seen to have a rude stratification. 

 Even when destitute of marine fossils, it shows its sub- 

 marine accumulation by the unoxidized and unweathered 

 condition of its materials. The stria? beneath it, and the 

 direction of transport of its boulders, show a general 

 movement from N.E. to S.W., up the St. Lawrence 

 valley from the Atlantic. Connected with it, and 

 apparently of the same age, are evidences of great local 

 glaciers descending into the valley from the Laurentian 

 highlands. The boulder clay of the basins of the great 

 lakes, and of the western plains, as well as that of the 

 Missouri Coteau, seems to be of similar character. The 

 basins of the lakes are parts of older valleys dammed up 

 with Pleistocene debris.* The Missouri Coteau and its 

 extensions, probably the greatest "moraine " in the world, 

 and the "terminal moraine" of the great continental 

 glacier of some American geologists, appears to me to be 

 the deposit at the margin of a sea laden with vast fields 

 of floating ice.-f- 



The lower Leda clay (d) seems in all respects similar 

 to the deposits now forming under the ice in Baffin's 

 bay and the Spitzbergen sea. The upper Leda clay 

 represents a considerable amelioration of climate, its 

 fauna being so similar to that of the gulf of St. Lawrence 

 at present, that I have dredged in a living state nearly all 

 the species it contains, off the coasts on which it occurs. 



* Newberry, Reports on Ohio ; Hunt, Canadian Reports ; Spencer, 

 Ancient Outlet of lake Erie, Ann. Phil. Society, 1881. 



t Report on 49th Parallel, G. M. Dawson, Paper on Superficial 

 Deposits of the Plains in the Journal of London Geological Society. 



