﻿GEOLOGY OF THE NEW YORK CITY AQUEDUCT IO7 



heal up the fractures and so make the rock about as substantial as 

 before. 



It is noted elsewhere that faulting is common in this region, and 

 that in a considerable portion of its lower course the Hudson prob- 

 ably follows such structures. It is, however, wholly unnecessary 

 to assume that its whole course is a fault line. Whether or not 

 there is a longitudinal fault zone of any prominence in the river at 

 Storm King is unknown. There are several cross faults, both above 

 and below this point, that give much clearer surface evidence of 

 their presence. Fault zones have proven to be objectionable ground 

 in many places along the aqueduct line, but elsewhere the data 

 refer chiefly to situations favoring more ready underground cir- 

 culation, i. e. at higher levels. In this particular case the rock in 

 question lies below former ground water level within the belt of 

 cementation rather than up in the belt of decay, and there is prob- 

 ably no disintegrated rock from any cause. 



