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 

 c Hole no. 12. In jMorningside Park at 113th street 



Surface elevaLion+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=]\Ianhattan schist, typical 

 with considerable pegmatite. But all good sound rock, not 

 much broken and standing at about 65^-80° 

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



Surface elevation=-55 feet 



Rock floor at depth of 159 feet=^el.-i04 feet 

 ^Material : 



a-44 feet^to el.-ii feet=filled ground and mixed material 



44-159 feet^to el.-i04 feet=fine sands and silts interpreted 

 as chiefly modified drift. ]\Iuch of it Ytry fine and the lower 

 portion rather micaceous and angular throwing a little doubt 

 on the exact line of demarcation between drift and residuarv- 

 matter 



1 59-161 feet^to el .-1 06 feet=core of ^Manhattan schist 



1 71-186 feet=to el.-i3i feet^decayed rock in place, some 

 micaceous type, coming out as mud 



186-228 feet^to el.-i73 feet:=micaceous reddish mud with 

 variable amounts of angular quartz grains. Certainly residu- 

 ary decayed rock 



228-270 feet=to el.-2i5 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 cliloritic 

 grains near the bottom 



305-335 feet=to el.-28o feet=Inwood limestone, core, ordi- 

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

 feet between 159 and 161 feet 

 e Hole no. 36 at io8th 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.-i85 feet 



