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NKW YORK STATIC MUSEUM 



soiithwost lino :ii I'icnnont. tliroujih wliicli out a small stream 

 now drains tho marshes baok of the Palisades into the Hudson. 

 The morainal doi)osits stand above this swamp in the form of 

 two northeast and southwest ridges of mounded drift rising from 

 KM) to over JL'O feet above the sea level. They are both cut off 

 by a small stream «>ii ilie west of Tappan village. 



The northern of Ihc^ two ridges is nearly stiaight in its oourse, 

 its southern slope being more uniform in direotion and steeper 

 than its northern. 



The southern ridge trends south westward from near Sparlcill 

 railroad station for 1 mile when it turns abruptly northwestward 

 inio the village of Tappan, having thus a oonvex southward 

 curvature as seen from the north though its southern front is 

 deoidodly angular. 



Both of the ridges are oomposed 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 wliicli (le|!osii is without stratitieation. The surface of both 

 ridges is comparatively free from kettles but carries many 

 boulders, m^^v j)articularly 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 

 (JO feet at the edge of I lie moraine to 10 feet where it disappears 

 southward beneath the iccent swamp accumulation, fixing the 

 upi)er limit of the water body or lake inlo which it was built 

 as lower lliaii 10 feel at the time of this stage, bilt giving no 

 closer index of sea IcncI. 



The posit i(Mi of these frontal moraines, just north of the Pier- 

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

 fi-om ice, pr<*sninal)ly allowing tho oscai)e of the drainage as now 

 inlo (he Hudson gorge; nor does the Hudson river appear to have 

 (lowed iliiMMigh I his gap since the ice last disappeared from its 

 vallry. .lust oast of the Sparkill station glacial striae on the 

 liaj. lock ic;i(| II. L'l w. n direction aibout at right angles to the 

 iiKnaiiic showing (hat, though the striae may have been made 



