412 THE CANADIAN NATURALIST. [Vol. vi. 



As the land rose again, ice-clad hills returned, and new though 

 perhaps less extensive glaciers were formed, and fresh crops of 

 boulders were deposited in the shallowing seas of the Saxicava 

 sand period. Snow still exists throughout the summer in the 

 higher ravines of the White Mountains, and on the hills of La- 

 brador, and a subsidence of a few hundred feet in the valley of 

 the St, Lawrence and the country to the southward, would suf- 

 fice to restore them to the condition of snow-clad hills giving off 

 icebergs from their bases, so near are we yet to the glacial 

 period ; and so little did it really differ from that condition of 

 the continent which still exists. I do not here enter into the 

 question of possible astronomical causes of refrigeration suggested 

 by Croll and others. These may have been influential both with 

 reference to changes of level and of temperature ; but I believe 

 the changes of level are sufl&cient to account for the observed facts. 



On my return from Europe in 1866, 1 endeavoured in a popu- 

 lar lecture, printed in Vol. III. N. S. of the Canadian Natural- 

 ist, and entitled comparisons of the " Icebergs of Belleisle and 

 the Glaciers of Mont Blanc," to picture the condition of Post- 

 pliocene Canada. I may refer to this paper as more fully stat- 

 ing my conclusions on the subject, and shall close this summary 

 of the results of sixteen years' work in the Post-pliocene, with 

 two extracts referring to the nature of the action of glaciers and 

 the probable state of Post-pliocene Canada. 



" Glaciers are mills for grinding and triturating rock. The 

 pieces of rock in the moraine are, in the course of their move- 

 ment, crushed agaiast one another and the sides of the valley, 

 and are cracked and o-rouud as if in a crushiDo;-mill. Farther, 

 the stones on the surface of the glacier are ever falling into cre- 

 vasses, and thus reach the bottom of the ice, where they are 

 further ground against one another and the floor of rock. In the 

 movement of the 2,lacier these stones seem in some cases to come 

 again to the surfiice, and their remains are finally discharged in 

 the terminal moraine, which i^ the waste-heap of this great mill. 

 The fine material which has been produced, the flour of the mill, 

 so to speak, becomes diffused in the water which is constantly 

 flowing from beneath the glacier, and for this reason all the 

 streams flowing from glaciers are turbid with whitish sand and 

 mud. 



" The Arve which drains the glaciers of the north side of 

 Mont Blanc, carries its burden of mud into the Rhone, which 



