GEOLOGY OF THE NEW YORK CITY AQUEDUCT 229 



Points for exploration north of 59th street 



It was soon evident that extensive exploratory work would have 

 to be undertaken and the following points were selected at which to 

 begin. 



1 The Harlem river crossing, where the distribution conduit line 

 crosses the river just below High Bridge [see later description]. 

 The only good evidence as to character of rock at this place is from 

 the pressure tunnel of the New Croton aqueduct which crosses the 

 river a short distance above. 



2 The Manhattanville cross valley (125th street depression). 

 This is the most important cross depression on the island of Man- 

 hattan. It is apparent after a little investigation that the bed rock 

 floor lies deep and that if it were not for the drift filling the tides 

 would surge through this valley making a direct connection between 

 the Hudson and East river. It was the least known as to depth 

 and character of any point along the proposed line. 



3 The depression between Morningside and Central Park. At 

 that place limestone on the crest of a pitching anticline reaches 

 farther south than on either side and is more deeply eroded. The 

 other zones of large importance are in southern Manhattan the 

 geology of which is a special study. 



