214 THE PHENOMENA OF DRIFT, OR 



acted in this mighty work, and as to their origin. The views 

 that now prevail may all be reduced to three phases, or theories. 

 I shall briefly inquire which of these acQords best with the phe- 

 nomena on this continent. 



The first theory, so ably defended by Mr. Lyell, and I believe 

 originating with him, supposes this work to have been accom- 

 plished mainly by icebergs, while the continent was beneath the 

 ocean. It admits of a greater degree of cold than now prevails 

 in the same latitude, and supposes that as the mountains emerged, 

 even though not much above the waters, they would produce gla- 

 ciers ; which, descending to the shores of the ocean, would be 

 floated away as icebergs, loaded with detritus, to a more south- 

 ern region, and there deposit their load to form moraines. 



That the greater part of the phenomena of drift on this conti- 

 nent must have been produced by icebergs, driven by currents 

 over its surface, I can hardly doubt. And indeed, all the promi- 

 nent features of this theory appear at first view extremely plausi- 

 ble, and many of them must be introduced into any theory of 

 this subject that will apply at all to this continent. But to some 

 features of it there are objections so serious as to be overcome 

 with great difficulty. These relate principally, but not exclusively, 

 to the vertical movements which our continent must have experi- 

 enced, if the theory be true. 



In the first place, I do not see that this theory, which is founded 

 on the uniformitarian doctrine of existing geological causes, pro- 

 vides for the depressed temperature which must have existed to 

 bring such vast quantities of ice over our country, as would be 

 necessary to produce the striae and accumulate the detritus. For 

 if our continent was then mainly below the ocean, greater heat, 

 instead of more cold, should have been the result. 



In the second place, we have no evidence that glaciers have 

 descended from any of our mountains ; but we have proof, 

 that the force which produced striae and embossed rocks, 

 acted upon the highest summits in the northern part of the 

 continent. 



In the third place, the vast deposits of vegetable matter, derived 

 from land plants, in various places from Nova Scotia to the 



