254 Address before the Association of American Geologists. 



are abraded over all northern countries. Vast blocks of stone are 

 likewise conveyed without abrasion, by the advance of the gla- 

 ciers, and lodged in peculiar situations. 



From year to year, the evidence has been increasing, of the 

 prevalence of intense cold in northern regions in the period im- 

 mediately preceding the historic. The elephants and rhinoceros 

 found, undecayed, in the frozen mud of Siberia, the arctic charac- 

 ter of the few organic remains found in the post-tertiary strata of 

 Scotland and Canada, and described by Lyell and Bowman, and 

 of the borders of Lake Champlain, as described by Emmons 

 and Conrad ; and the great extension of the ancient moraines in 

 the Alps, are the evidence from which Agassiz infers that in that 

 period, all northern countries were covered with a vast sheet of ice, 

 filling the valleys and extending southerly as far as diluvial phe- 

 nomena have been observed. Glaciers would then be formed on 

 mountains of moderate altitude ; and, indeed, he supposes that 

 all the northern parts of the globe might have constituted one 

 vast Mer de Glace, which sent out its enormous glaciers to the 

 south ; thus giving the same direction to the drift and the striae 

 on the rocks. As these vast masses of ice melted away, when 

 the temperature was raised, immense currents of water were 

 the result, which would lift up and bear away huge icebergs, 

 whereby extensive erosions would be produced, and blocks of 

 stone be transported to great distances. Subsequently, lakes 

 would be formed where moraines had produced barriers, clay and 

 sand would there be quietly deposited, and the waters be ulti- 

 mately drained by the wearing down of the barriers of detritus. 



It is doing injustice to this theory to attempt so brief a descrip- 

 tion of it. A detailed account of existing glaciers, which cannot 

 here be given, forms the best preparation for a just appreciation of 

 the theory. Admitting its truth in the main, let us see how it 

 applies to the phenomena of drift in this country. 



In the first place, it explains satisfactorily, the origin of those 

 singular accumulations of gravel and bowlders, which we meet 

 with, almost every where, in the northern parts of our country. I 

 cannot doubt that these are ancient moraines ; just such as exist 

 in Scotland and England. Were this the proper place, I could 

 point out a multitude of localities of these, most of which have 

 been a good deal modified by subsequent aqueous agency ; but 

 some of them retain the very contour which they had as the 



