﻿GEOLOGY OF THE NEW YORK CITY AQUEDUCT 2IQ, 



12800 Manhattan schist probably good quality (to s. end of Cen- 

 tral Park) 

 21000 From Central Park to East river — no outcrops — mostly 

 Manhattan schists at tunnel depth. Condition largely 

 conjectural 1 — probably mostly good rock with occasional 

 weak zones 

 6000 Manhattan island to City Hall, Brooklyn. Containing an 

 unknown 1 zone in the East river and unknown quality 

 of rock in Brooklyn. 



Summary of Line A 



Feet 



6 200 Yonkers gneiss 



7 000 Fordham gneiss 



2 400 Contact (probably in gneiss) 

 12 000 In wood limestone 



2000 Contact (probably in limestone) 

 29200 Manhattan schist (good) 

 21 000 Estimated Manhattan schist (fair) 



6 000 Almost unknown 



85 800 total 



Line B. Going southzvard from Hill View reservoir 



Feet 



8 000 Yonkers gneiss — good quality 

 13000 Fordham gneiss — good quality 

 6 800 Inwood limestone, probably mostly in fair condition, except 



at two points (to Cromwell av.) 

 6600 Inwood limestone, unknown condition, but probably largely 

 poor (to Harlem river) 

 600 Inwood limestone — unknown condition (Harlem river) 

 4 600 Inwood limestone — unknown condition — probably fair 

 (to Mt Morris Park) 

 800 Manhattan schist, good 

 800 Probably Manhattan schist — unknown 

 2800 Inwood limestone — unknown condition — probably at least 



one bad zone (to 106th st.) 

 12000 Manhattan schist along Central Park — good 



1 Explorations since conducted by the Board of Water Supply have proven 

 the quality and character of the rock floor at these places. For the revised 

 statement on these sections see the special discussions. 



