266 Prof. Rogers^s Address before the 



in the hills and mountains, they frequently form long narrow belts, the 

 margins of which sometimes maintain a remarkable parallelism. 



The course of the drift and bowlders, like that of the scratches, is 

 obliquely across the crests of most of our mountain ridges ; but lower 

 on their slopes, and in the beds of the deeper longitudinal valleys, it 

 conforms partially or entirely to the directions of what would be the 

 great natural channels of drainage, if the whole surface were tempora- 

 rily or permanently under water. 



It should be observed that the bowlders of all sizes are themselves 

 smoothed and striated, and in many cases in such manner as to indi- 

 cate that this effect has been produced by the fragments rushing past 

 each other. 



Lastly, blocks of considerable size have been transported from low- 

 er to higher elevations, being seen in New England, New York and 

 northern Pennsylvania, on mountain ridges a thousand or fifteen hun- 

 dred feet above the level of their parent rocks ; and this fact, as Prof. 

 Hitchcock has justly remarked, is one of great importance in the his- 

 tory of our drift. 



3d. The third class of facts connected with the drift, relate to the 

 proofs of a lower level in the land at the epoch of its production. In 

 describing the post pleiocene blue clay of Lake Champlain and other 

 northern valleys, I have already cited the proofs that at one period at 

 least in the general era of the drift, the surface of the country in the 

 region of New York and the St. Lawrence was lower in level than it 

 now is by as much as perhaps five hundred feet. It is obvious too that 

 the whole of New England was at the same time somewhat depressed, 

 though there is no satisfactory indication that it was throughout as much 

 submerged as the region of Lake Champlain. It is moreover highly 

 probable that the country of the upper lakes was lower and more over- 

 flowed than at present, though it has not yet been established that the 

 depression was sufficient to let in the sea. That the waters of the ocean 

 flowed freely at this particular middle period of the drift through the 

 long and narrow valleys of the St. Lawrence, Lake Champlain, the 

 Hudson and the Mohawk, and ascended those of the principal rivers of 

 New England, and even gained admission to the basin of Lake Onta- 

 rio, there cannot be a doubt ; but that our whole northern region was, 

 as Prof. Mather and Mr. Hall suppose, lower than it now is by fifteen 

 hundred or two thousand feet, and the greater part of New England 

 and New York and the vast area of the western states all at that era 



