72 SURFACE GEOLOGY. 



upon both poles." "This," says he, " is the very theory which I advocate; and 

 unless the advocates of that theory go to that length in their premises, I venture 

 to say, without fear of contradiction, that they will find the source of their ice- 

 bergs fall short of the requisite conditions which they must assume upon due con- 

 sideration, to account for the whole phenomena as they have really been observed." 

 {Lake Superior, p. 406.) I think that could we get access to the floor of the Arctic 

 Ocean, where the icefloes probably occupy more space than the water, that par- 

 tially bears them up, we should find a work going on very similar to that which 

 produced the drift. On such icebergs and icefloes, for the present I take my stand. 

 But as I look toward the shore, and see my neighbor standing upon a glacier, I can 

 hardly tell the difference between the two foundations ; and whenever he will show 

 me that his glacier is advancing southerly over a level surface, as does my iceberg, 

 I will gladly place myself by his side. 



As to the origin of that more intense cold which once prevailed over New Eng- 

 land and other countries much farther from the pole than at present, I have no 

 hypothesis to offer. But as to the fact it seems to me that the undeniable former 

 great extension and thickness of glaciers in Switzerland, Scandinavia, Wales, and 

 perhaps Scotland, and the absence of organic remains from drift, in general, make 

 it certain. I have sometimes imagined that the upheaval of the bed of the north- 

 ern ocean, according to De la Beche, or the earthquake waves of the Professors 

 Rogers, sweeping southerly from the same region, might afford an explanation. 

 But such forces would produce only a temporary submersion and icy deposit; 

 whereas the evidence of the long continued presence and action of water and ice, 

 and of the slow emergence of the land from the ocean, evince its permanent sub- 

 mergence. 



41. Let me now present a summary of my present views of the origin of that 

 deposit, properly called drift, excluding all which I have described as modified 

 drift, 



1. Glaciers. — It seems to me that the moraines of glaciers affords a good type of 

 drift, viz. : a confused mixture of abraded materials of almost every size, driven 

 mechanically forward. I cannot see why we should limit the impelling force to 

 water as does the ordinary definition of the term drift. 



If these views are correct (and I presume no geologist will dissent), then we 

 have one agency in this work in which all are agreed, and which is still in opera- 

 tion before our eyes. Moreover it has been at work from the earliest times 

 in which we have any evidence of drift action. Certainly it goes back as far as 

 the tertiary period, perhaps further. Before the last submersion of our continents 

 it may have operated long and powerfully ; and if the views of some geologists 

 are true, it then accumulated the great body of the drift now before our eyes. And 

 still in northern regions, and even in central Europe, it is adding to the mass 

 daily. 



2. Icehergs. — Wherever these reach the bottom and are urged forward, it cannot 

 be doubted that they must produce essentially the same effects as glaciers. And 

 for the reasons already given, I must suppose that in some countries — our own for 



