GLACIAL DRIFT. 21$ 



The phenomena agree best with the theory that the south-east course 

 originally covered both the valley and the adjacent borders for scores of 

 miles, but that, after the ice ceased to be furnished abundantly from the 

 St. Lawrence, the residue followed its natural way down the several river 

 depressions to the sea, and, being of considerable thickness, was able to 

 leave abundant evidences of its passage. 



Prof. J. D. Dana was the first to insist upon the existence of a Con- 

 necticut glacier separate from the general mass of drift. My father was 

 the first of American geologists to point out the fact in any publication 

 of the existence of local glaciers radiating from high ridges.* He was 

 led to this conclusion from a comparison of the ancient glacial drift in 

 Wales and Switzerland with the drift generally, and with the local exam- 

 ples seen by him in western Massachusetts and Vermont. As the 

 common phenomena of the drift seemed to him best explicable upon the 

 iceberg theory, his ready recognition of the real glacial markings in the 

 Westfield and Deerfield River valleys shows how ready he was to accept 

 truth, even against his judgment of the proper interpretation of the 

 phenomena of nature. His suggestion of a movement down the Con- 

 necticut valley is not to be regarded as a claim that he understood the 

 whole depression to be scored like the few examples he had seen.f The 

 fact established clearly by him was, that the Hoosac and Green Moun- 

 tains supported the mer de glace in the last part of the ice period, from 

 which local glaciers flowed down, both towards the Connecticut on the 

 east, and to the Champlain valley on the west. We can now extend this 

 deduction eastwardly, and say that there was a Connecticut Valley gla- 

 cier in the latter part of the ice period, with branches both from the 

 west and the east. 



The branch glaciers on the west that have been described are these : 

 Upon Westfield river, with its tributaries, especially Little river ; Deer- 

 field river, both in Massachusetts and Vermont ; West river, joining the 



* Report Geology of Massaclitisetts, 1S53. Sinithsonzan Contributions, \o\. ix. 



f The following is the passage referred to {Smithsonian Contributions, vol. ix, p. 136): On examination, I did 

 find, on the west side of the Connecticut valley, that what I called drift striae, instead of running north and south, 

 as they usually do, turn southerly south of South Hampton as much, in some places, as S. 65° W. I suspected 

 at first, either that these markings were produced by the [Westfield] glacier, after it reached the Connecticut val- 

 ley, or that the supposed glacier scratches were the result of drift agency operating up hill. But when I found 

 that the stoss of the glacier strise was the west side, and that of the drift striae was the north-east, both these sup- 

 positions were shown to be untenable ; and I accounted for the south-west direction of the drift striae by the 

 expansion to the right of the Connecticut valley south of South Hampton. I think this the right interpretation 

 of the facts, but I could wish to give them further examination. 



