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NEW YORK STATE MUSEUM 



southwest line al Piermont, through which cut a small stream 

 uow drains the marshes back of the Palisades into the Hudson. 

 The morainal deposits stand above this swamp in the form of 

 two northeast and southwest ridges of mounded drift rising from 

 100 to over 120 feet above the sea level. They are both cut off 

 by a small stream on the west of Tappan village. 



The northern of the two ridges is nearly straight in its course, 

 its southern slope being more uniform in direction and steeper 

 than its northern. 



The southern ridge trends southwestward from near Sparkill 

 railroad station for 1 mile when it turns abruptly northwestward 

 into the village of Tappan, having thus a convex southward 

 curvature as seen from the north though its southern front is 

 decidedly angular. 



Both of the ridges are composed largely of red gravelly drift. 

 An excavation just south of the Sparkill railroad station showed 

 gravels and sands with occasional small boulders, the upper part 

 of which deposit is without stratification. The surface of both 

 ridges is comparatively free from kettles but carries many 

 boulders, now particularly noticeable about the houses. 



A nearly smooth water-laid drift plain lying between 60 and 

 80 feet above sea level separates the ridges, and drains to the 

 westward; but more significant is a small frontal apron of washed 

 gravel and sand which extends beneath the swamp at the south- 

 western end of the outer or southern ridge, sloping from about 

 60 feet at the edge of the moraine to 10 feet where it disappears 

 southward beneath the recent swamp accumulation, fixing the 

 upper limit of the water body or lake into which it was built 

 as lower than 40 feet at the time of this stage, but giving no 

 closer index of sea level. 



The position of these frontal moraines, just north of the Pier- 

 mont gap, plainly indicates that at this time the gap was free 

 from ice, presumably allowing the escape of the drainage as now 

 into the Hudson gorge ; nor does the Hudson river appear to have 

 flowed through this gap since the ice last disappeared from its 

 valley. Just east of the Sparkill station glacial striae on the 

 trap rock read n. 24° w. a direction about at right angles to the 

 moraine showing that, though the striae may have been made 



