GEOLOGY OF THE NEW YORK CITY AQUEDUCT 89 



2 Discussion 



The present facts therefore indicate that the buried Hudson 

 channel is more than 700 feet deep between Storm King and 

 Breakneck ridge. Furthermore this is more than twice as great 

 depth as has been found (so far as yet tested) at any other point 

 either above or below this place. Although data of this kind are 

 scarce yet there are two other borings that have given surprising 

 results — (a) at Peggs point and (h) the Pennsylvania borings at 

 New York city. 



Peggs point. At this place, where studies were made for a 

 possible crossing, a hole 700 feet from shore struck rock at 223 

 feet and the unknown space or interval within which it is possible 

 for a channel to lie is less than 1040 feet wide. This is about 10 

 miles above the Storm King crossing and in much softer rock 

 (Hudson River slates). Yet the Storm King gorge in granite is 

 deeper than that (deeper than 223 feet) for a width of nearly 2500 

 feet. Of course, there may be, and probably there is, a much 

 deeper channel at Peggs point within the 1040 feet unexplored 

 space. But even so there is a remarkable discrepancy in width of 

 gorge at these two points that must be accounted for in some other 

 way than simple stream erosion. 



The Pennsylvania borings opposite 33d St., New York city. 

 The data gathered by the Engineers of the Pennsylvania Tunnel 

 Company in their explorations for tunnel from 33d street, Man- 

 hattan, to Jersey City, have recently been made public. There are 

 six holes into rock. Their positions and depth to rock bottom are 

 given below : 



a 800' from New York bulkhead 190' to bed rock = aplite 



b 1000' from New York bulkhead 290' to bed rock = hornblende 

 schist 



c 21S0' from New York bulkhead 300' to bed rock = chloritic 

 and serpentinous rock. 



d 2350' from New York bulkhead 260' ( ?) to probable boulder = 

 jasper breccia 



e 3300' from New York bulkhead 270' to bed rock = arkose 

 sandstone 



/ 13700' from New York bulkhead 225' to rock=brown sand- 

 stone 



■ There are other shallower borings on both sides of the river. 

 Those on the Manhattan side are represented by several different 

 facies of Manhattan mica schist and granite and pegmatite in- 



