GEOLOGY OF THE NEW YORK CITY AQUEDUCT 91 



assumption that there are narrower, still deeper channels within the 

 unexplored spaces hoth at New York city and at Peggs point. 



The only known exception and the one really surprising section 

 is the Storm King crossing. It is toO' wide, considering the profiles 

 at Peggs point and at New York city for simple normal stream 

 erosion. That is clear enough. But a still more difficult question is 

 whether it is also too deep. It is much deeper than any known 

 section above or below for a distance of 50 miles. 



There appears to be only one satisfactory explanation of this 

 abnormal width of the deeper section and that is by glacial erosion. 

 Just above Storm King is the wide bay opposite Cornwall and 

 Newburgh. The few glacial scratches observed trend about s. 15° e. 

 The ice therefore moved to the east of south, and it is noted that the 

 course of the river is about the same. The northern tront of Storm 

 King mountain is steep and trends east and west while the northern 

 front of Breakneck mountain trends southwest. It would appear 

 therefore that these slightly converging mountain fronts served as 

 sort of a funnel into which the ice was forced from the wide gather- 

 ing ground immediately above, and through which there may have 

 been a tongue or stream of ice of more than average power and 

 efficiency moving alm.ost in direct line of the present course of the 

 river. It is reasonable to expect that these conditions would favor 

 more than average glacial erosion. 



3 Storm King-Breakneck mountain profile 



It is practically impossible to draw a complete profile for the 

 Hudson river gorge at any point in its lower course. Even at Storm 

 King mountain or New York city or at Peggs point, at each of 

 v/hich places considerable exploratory work has been done, only the 

 broadest features are known. Nevertheless, several things have 

 been proven and they are worth considering in this question. They 

 may be summarized as follows : 



a If there is a very deep gorge at Peggs point (deeper than 250 

 feet) it can not be over 1000 feet wide. 



h If there is a very deep gorge at New York city (deeper than 

 300 feet) it can not be over 1200 feet wide. 



c xA.t Storm King, located between the other two and in harder 

 rock than either of them, a gorge at least 400 feet deep is proven 

 to have a width of more than 1500 feet. 



It is certain that simple stream erosion could not account for 

 such a difference of cross section. There is no doubt but that en- 



