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NEW YORK STATE MUSEUM 



The phenomena shown a1 Xvack, so far as my observations go, 

 afford no indication of sea level since the retreat of the ice sheet 

 different from that now existing, though this evidence is wholly 

 negative in regard to a recent rise of the water level. 



Tarrytoum delta. At Tarrvtown, Pocanlico brook (Gory brook 

 on the United States Geological Survey map) has cut deeply 

 through a deposit of sand forming its ancient delta on the margin 

 of the Hudson gorge. At Tarrytown the eastern wall of the Hud- 

 son gorge changes its course from a few degrees east of north to 

 nearly north, and at the same time the rocky wall advances 

 slightly to the westward. In this angle of the bank below the 

 brim of the ancient rock terrace on the northern edge of the town 

 lies the deposit named. 



The surface of the deposit is about 60 feet above sea level, rising 

 in a small mound to above 80 feet. On the north it is bounded 

 by steep slopes, in part cut back by the stream which flows at its 

 base and in part an original depression evidently marking the 

 presence of ice while the sands were being deposited. 



Deposits south of Croton point. The ice which covered the Hud- 

 son valley south of the Hudson Highlands assumed a lobate margin 

 at the time of its halt along the line of the terminal moraine. The 

 axis of most rapid motion in this lobe lay on the west side of the 

 Palisade trap ridge in the Hackensack lowland of New Jersey. 

 East of this line the ice moved southward and eastward across 

 the lower Hudson ; west of the line the ice moved to the southwest 

 at angles somewhat greater than the southwest course of the lower 

 portion of the Hudson itself. During the retreat of the ice from 

 the moraine toward the southern edge of the Highlands it is to 

 be presumed that the same general bottom movements of the ice 

 would have been maintained till the ice thinning over the High- 

 lands continued to push through the Highland gorge alone and 

 thus became restricted to a small glacier occupying the Hudson 

 gorge. 



The margin of this small glacier it is believed is found in the 

 frontal deposits at Croton point and in the vicinity of Haver- 

 straw; but the deposits south of this stage in the retreat pertain 

 to the broader development of the ice sheet which had not as yet 

 lost its marginal continuity with the ice sheet extending eastward 



