Geology of Long Island. 361 



is quite reasonable to assume it capable of producing such a re- 

 sult. At one locality, West Deer Park, this is manifestly the 

 case, and I have no doubt that in time it will be found generally 

 true. The numerous springs that issue from the hillsides along 

 the north shore also lead one to infer that the substratum of clay 

 has been raised up in the centre of the hills. The occurrence of 

 the springs might be accounted for hypothetically by supposing 

 that these hills are the remnants of unequally eroded horizontal 

 strata of sand underlaid by clay ; but this we know is not the 

 case. 



Mr. Upham, in his discussion of the moraines, attributes all 

 the stratified deposits to diluvial and alluvial action in the Cham- 

 plain period, to which the Gardiner's Island deposit has been 

 erroneously referred. He also concludes that the more southern 

 drift hills, which are from 200 to 250 feet high, were formed 

 in ice-walled river-channels formed upon the surface of the gla- 

 cial sheet when rapidly melting. That this process has taken 

 place in some cases, is quite probable, as there are undisputed 

 kames in certain places, but from the analogy of the deposits in 

 question to the others described, I am inclined to refer them 

 generally to the same causes. 



The changes which have occurred on Long Island since the 

 retreat of the glacier, have been mainly topographical, and un- 

 questionably very extensive. The streams of the Ohamplain 

 epoch carried down the drift from the morainal hills and distri- 

 buted it on the plain to the south, forming in many places local 

 beds of clay. In the vicinity of Bethpage and elsewhere, are 

 hillocks of stratified sand similar in appearance to the New Eng- 

 land kames. The valleys mentioned above, which have been ex- 

 amined by Elias Lewis, Jr., are unquestionably the channels of 

 streams resulting from the melting of the glacier. 



The coast line of the island is rapidly changing, on account of 

 the action of the swift westerly currents which are wearing away 

 the east end and depositing the sediment along the north and 

 and south shores. By this means the bays which open into the 

 Sound are rapidly becoming shallow. The Great South Beach 

 is also an evidence of the action of the waves and currents in 

 changing the outline of Long Island. We have moreover abund- 

 ant evidence that the south shore has been gradually sinking. 



