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 efTect 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. la 

 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 

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

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

 submerged as the region of Lake Champlain. It is moreover tag y 

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

 flowed than at present, though it has not yet been established t a 

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

 flowed freely at this particular middle period of the drift throug ^ 

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

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

 New England, and even sained admission to the basin of La e 

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

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

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

 and New York and the vast area of the western states all at I a 



