GEOLOGY OF THE WEST POINT QUADRANGLE, NEW YORK 93 



date almost any type of vessel. In railroad building, however, the 

 conditions are not so simple. The sides of the gorge at many places 

 reach the water's edge in comparatively steep cliffs or rugged moun- 

 tain sides and the upland is too rugged to encourage the location of 

 any such transportation line. Two railways, however, follow the 

 Hudson river. The difficulties encountered by them are in part met 

 by tunnelling and in part by filling and stabilizing the natural fill of 

 the river gorge itself. No extraordinary problems have arisen in 

 this connection. 



A recent piece of engineering work, however, the Catskill aque- 

 duct, has introduced several less common problems of sufficient com- 

 plexity to warrant special note. 



Those of chief geologic interest are : ( i ) the Hudson river cross- 

 ing at Storm King, (2) Bull Hiil tunnel, (3) the Foundary brook 

 crossing, (4) Garrison tunnel, (5) the Sprout brook section, (6) the 

 Peekskill Hollow section. 



In a region of such complex structural habit and variety of relief, 

 considerable difference in the practical problem is presented at these 

 different localities. Thus it happens that in certain cases it is a 

 matter of depth of preglacial channel ; in others, a matter of quality 

 of rock or depth of decay or source of structural material or water 

 behavior. The cases selected for illustration are typical of problems 

 belonging to engineering geology in a region of this kind. 



The Hudson river crossing from Storm King to Breakneck 

 mountain. The Catskill aqueduct approaches the Hudson fro-m the 

 west at hydraulic grade, across the country back of Newburgh which 

 is something over 400 feet above sea level. It is necessary either to 

 keep this level by some sort of structure or maintain the pressure in 

 some sort of conduit or pressure tjnnel across the Hudson river to 

 the east side, so that a 400-foot level may be maintained again 

 across the Highlands. The engineers in charge of this work decided 

 in favor of a pressure tunnel in bedrock as the most permanent and 

 practical design for this undertaking, and the location chosen for the 

 crossing was between Storm King and Breakneck mountain in the 

 northeast corner of this quadrangle. 



A careful study of other possible crossings was made by the senior 

 author of this bulletin before this selection was made and it was 

 finally determined on several accounts that this location had more 

 known points in its favor and was more defensible geologically than 

 any other. All the more favorable locations were in the Highlands 

 within the bounds of this quadrangle, but several others outside of 

 this area were also explored in some detail. 



