GEOLOGY OF THE NEW YORK CITY AQUEDUCT 2ig 



12 800 ^lanhattan 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^ — probably mostly good rock with occasional 



weak zones 

 6000 }^Ianhattan island to City Hall, Brooklyn. Containing an 



unknown^ zone in the East river and unknown quality 



of rock in Brooklyn. 



Summary of Line A 



Feet 



6 200 Yonkers gneiss 



7000 Fordham gneiss 



2400 Contact (probably in gneiss) 

 12 000 Inwood limestone 



2000 Contact (probably in limestone) 

 29200 ^Manhattan schist (good) 

 21 000 Estimated Manhattan schist (fair) 



6000 Almost unknown 



85 800 total 



Line B. Going soufhz^'ard froJii Hill Jlezc reservoir 



Feet 



8 000 Yonkers gneiss — good C[uality 

 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 i\It ^Morris Park) 

 800 ^Manhattan schist, good 

 800 Probably Manhattan schist — unknown 

 2 800 Inwood limestone — unknown condition — probably at least 



one bad zone (to io6th st.) 

 12000 ^Manhattan schist along Central Park — good 



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

 the qualit}- and character of the rock floor at these places. For the revised 

 statement on these sections see the special discussions. 



