186 THE PHENOMENA OF DRIFT, OR 



operated in a southeasterly direction over the northern parts of 

 this continent, at the lowest and at intermediary levels, has acted 

 in the same manner, and in the same direction, upon the sum- 

 mits of the White Mountains. 



Hence, secondlv, that the same force surmounted all the moun- 

 tains on this continent east of the Mississippi. 



Hence, thirdly, we have no reason to suppose that the White 

 Mountains have ever been a centre from which bowlders have 

 been dispersed ; and no evidence has been discovered on the 

 sides of the mountain of the former existence of glaciers, other 

 than icebergs floated by a current. 



Hence, fourthly, the presumption is strong, that no other moun- 

 tains east of the Mississippi have been centres of dispersion, or 

 have been occupied by Mers de Glace, emitting glaciers. For 

 the high latitude of the White Mountains makes it more 

 probable that glaciers should have existed there than on any 

 other of our mountains, except those of Essex county in 

 New York ; and Professor Emmons, in his Reports, represents 

 the force there as acting in a southerly direction. And since 

 we are sure that the same southeasterly impulse, connected 

 evidently with currents of water, which has produced the phe- 

 nomena of drift at lower levels, has operated in one place to the 

 height of five thousand feet, it furnishes an adequate cause for 

 the like effects at the same height all over the continent ; and, 

 therefore, to call in the aid of other causes, is unphilosophical. 

 To stand at that dizzy height, and witness the erosions of this 

 agency, makes a deep impression of its potency and far-reaching 

 influence ; especially if we suppose aqueous currents ever to 

 have attained such an altitude ; or of its immense antiquity, if 

 it acted when these primeval mountains were at the bottom of 

 the sea.*" 



* January 1, 1S43. "Mountains of considerable elevation in Scotland, — Schiliallion for 

 exann|ile, — have their summits as polished as their flanks ; whereas in Switzerland there 

 exists a limit, at about nine thousand French feet in the centre of the Alps, above which 

 the summits are no longer polished ; but where the ruarged peaks present a very 

 striking- contrast to the lower surfaces, which are polished, or at least moutonuies. In the 

 interior chains of the Alps, the polishing does not reach to a greater height than six 

 thousand or seven thousand feet." — Agassiz on the Glacial Theory, New Ed. Philos. 

 Journal, Oct. 1S42,^. 232. 



