﻿GEOLOGY OF THE NEW YORK CITY AQUEDUCT 247 



242-280.71 feet— to el. -242.71 feet=Inwood, very coarse type 

 of limestone. Poor core showing. Much broken 

 Hole no. 12. In Morningside Park at 113th street 



Surface elevation+28 feet 



Rock floor at depth of 84 feet=el. -50 feet 

 Material : 



0-26 feet=to el.+2 feet=mixed drift 



26-84 feet=to el-56 feet=modified drift 



84-335.15 feet=to el.-307.15 feet= Manhattan schist, typical 

 with considerable pegmatite. But all good sound rock, not 

 much broken and standing at about 65°-8o° 

 Hole no. 16. Corner of Manhattan avenue and iioth street 



Surface elevation=+55 feet 



Rock floor at depth of 159 feet— el -104 feet 

 Material : 



0-44 feet=to el.+n feet=filled ground and mixed material 



44-159 feet=to el-104 feet— fine sands and silts interpreted 

 as chiefly modified drift. Much of it very fine and the lower 

 portion rather micaceous and angular throwing a little doubt 

 on the exact line of demarcation between drift and residuary 

 matter 



1 59-161 feet=to el-106 feet=core of Manhattan schist 



1 71-186 feet=to el-131 feet— decayed rock in place, some 

 micaceous type, coming out as mud 



186-228 feet=to el-173 feet=micaeeous reddish mud with 

 variable amounts of angular quartz grains. Certainly residu- 

 ary decayed rock 



228-270 feet— to el-215 feet=similar residuary matter less 

 highly colored passing from reds into grays and coming out 

 as soft material 



270-305 feet=to el-250 feet=grayish micaceous and quartz- 

 ose residuary matters. With much silvery mica and chloritic 

 grains near the bottom 



3°5~335 feet=to el-280 feet=Inwood limestone, core, ordi- 

 nary type. No more recovered above this point except for 2 

 feet between 159 and 161 feet 

 Hole no. 36 at 108th street and Manhattan avenue 



Elevation of surface+63 feet 



Rock floor (decayed) at depth of 55 feet— el.+8 feet 



Depth to solid core=248 feet^el-185 feet 



