826 D. Dana on American Geological History. 



Much, doubt must remain about the origin of the drift, until 

 the courses of the stones and scratches about mountain ridges 

 and valleys shall have been exactly ascertained. The general 

 course from the north is admitted ; but the special facts proving 

 or disproving a degree of dependence on the configuration of the 

 land have not yet been sufficiently studied. 



One theory, the most prevalent, supposes a deep submergence 

 over New England and the North and West, even to a depth of 

 four or five thousand feet, and conceives of icebergs as floating 

 along the blocks of stone, and at bottom scratching the rocks. 

 Another, that of the Professors Kogers, objects to such, a sub- 

 mergence, and attributes the result to an incursion of the ocean 

 from the north, in consequence of an earthquake movement 

 beneath the Arctic Seas. 



The idea of a submergence is objected to on the ground that 

 the sea has left no proof of its presence by fossils, sea-shore ter- 

 races or beaches. 



Unless the whole continent were submerged, of which there is 

 no evidence whatever, there must have been in the Post-tertiary 

 Period an east-and-west line of sea-shore, say across New Jersey, 

 Pennsylvania, Southern Ohio, and the other States west, or still 

 farther south ; and yet no such, sea-shore marks now exist to 

 trace its outline, although the ocean must have been a portion of 

 the same that had laid up the Cretaceous and Tertiary beds all 

 along the coasts, and, in fact, already contained the oysters and 

 clams and many other species of Mollusks which now exist. 

 Can it be, that, contrary to all the ways of the past, such a grand 

 submergence as this view supposes, placing New England four 

 thousand feet under water, could have transpired without a sea- 

 shore record ? 



Very many have replied in the affirmative ; and one able ad- 

 vocate of this view, who sees no difficulty in the total absence 

 of sea-shore terraces or fossils at all levels above the Laurentian 

 beds, finds in the succeeding epoch sea-shore accumulations in 

 all the terraces of our rivers. Why this wonderful contrast ? 

 What withheld the waves from acting like waves in the former 

 case, and gave unbounded license in the latter ? 



This much, then, seems plain, that the evidence although neg- 

 ative, is very much like positive proof that the land was not 

 beneath the sea to the extent the explanation of the drift phe- 

 nomena would require. 



There are other objections to this view of submergence. If 

 North America were submerged from the southern boundary-line 

 of the drift far into the Arctic regions, this would have made a 

 much warmer climate for the continent than now; if only half- 

 way, then there is another east-and-west shore line to be traced 

 out, before the fact of the submergence can be admitted. Again, 



