1847.] Association of Geologists and JYaturalists. 217 



surface, where the water melts the ice, and large icebergs are 

 broken off and float away. Murchison says that glaciers have left 

 their marks as far as the mountains extend, but that currents have 

 produced the phenomena observed in the valleys. 



This cannot be true — for the striai of the mountains and val- 

 leys preserve one general direction. Now the striae being similar 

 in character when observed in dilferent parts of the world, he was 

 led to conclude that one general cause had produced these effects. 



Mr. Redfield did not think that the striae were marked upon the 

 mountains and valleys at the same time. 



Remarks were also made by Dr. Reed and Prof. H. D. Rogers. 

 The latter spoke of the terraces of the St. Law^rence and the Lakes. 

 Some of them give evidence that they had been formed by drain- 

 ings of the upper lakes. 



A few additional facts gleaned from Mr. Redfield's paper, upon 

 the Drift of Long Island. The subject has acquired a deeper in- 

 terest, in consequence of the discovery of Marine shells in that of 

 Long Island. These are limited, however, to a few localities, 

 The drift referred to, is derived principally from the sand stone 

 and trap of New Jersey. The marine shells consist of individuals 

 belonging to the genera Venus, Ostrya, Solecurtis, and several 

 others. The Solecurtis carribeus is interesting, and its presence 

 taken in connection with other facts, go to prove that the climate 

 of this vicinity has not materially changed, as has been inferred 

 by Mr Lyell. Some of the specimens of shells were derived from 

 ancient indurated beds, which were of course partially broken up 

 during the drift period. Most, if not all the shells are in a broken 

 condition, and sometimes worn. Dr. Mitchell had noticed the 

 shells in Long Island, but was not aware of their existence 

 in the drift. Marine, post pleiocene shells have been described 

 by Mr. Murchison in the drift of northern Europe. Mr. Redfield 

 connects the origin of drift with the existence of icebergs, aided 

 by transporting currents flowing from the north to the south, one 

 of which may have flowed from the Gulf of St. Lawrence to New 

 York bay, through the great fracture and depression, stretching 

 through the valleys of Lake Champlain and the Hudson river. Ice- 

 bergs are still found in the latitude of New York. Their effect 

 on climate is to be regarded as temporary, and not as furnishing 

 proof of a general reduction of the temperature. 



In the discussion which followed, Mr. Desor maintained the doc- 

 trine of glacial action, as a cause which has given origin to the 

 drift of all countries — referring to the drift of Scandinavia and 

 the Alps, for facts to support the main features which were an- 

 nounced. Specimens of scratched rocks were also exhibited from 

 glacial regions, as the fiords of Christiana, the polar regions and 



