of the Hudson River. 11 



down from the New York shore at West 32d street to New 

 Jersey, and they have been supplemented by several diamond 

 drill holes.' 55 ' As shown by the accompanying cut (fig. 5), taken 

 from Mr. Rogers' paper, the diamond drill borings are about 1100 

 ft. apart at the most important place and 900 ft. apart farther 

 west. It is a very interesting question whether the bed-rock 

 continues across these intervals at a depth of 300 ft, at which 

 depth it appears on either side, or whether there is a deep 

 and relatively narrow notch in the 1100 ft. stretch, so deep 

 indeed as to permit water which had traversed the Storm 

 King pass, 40 miles north at 800 ft. or thereabouts below 

 tide, to reach the sea by a pass, necessarily still lower, opposite 

 New York City. Advocates of water erosion as the cause of 

 the Hudson gorge, would assume the existence of the notch. 

 The bottom of the notch could not be less than between 500 

 and 600 feet below the nearest known bed-rock. 



If water erosion is not the cause, then the Storm King pass 

 has been over-deepened by some other agent than water. 

 There is but one other agent and that is ice. Sub-glacial 

 erosions would therefore follow. Opinion in America in recent 

 years has been predominantly against glacial erosion, but 

 various lines of evidence are making this process more and 

 more probable. The Storm King Crossing would seem to be 

 a favorable place for it. 



Between Storm King and Breakneck Mountain the Hudson 

 valley is very narrow, as is shown by fig. 3. A short distance 

 north the old crystalline rocks end in a sharp fault escarpment 

 which crosses the valley in a northeast direction. The softer 

 Paleozoics have been easier marks for erosion than the hard 

 crystallines and now present a broad valley. The same con- 

 trasts existed at the opening of the Glacial epoch. As the 

 ice-sheet moved southward its only outlet was the narrow pass 

 which was occupied by the river. The ice was crowded into 

 this gorge and certainly was in as favorable a position to deepen 

 its channel as ice under ordinary circumstances ever is placed. 

 It may well be that in this way the channel was over- 

 deepened and that as the ice-sheet approached the terminal 

 moraine just below New York, it became gradually feebler 

 and rose to higher levels, leaving in the end a shallower chan- 

 nel filled with ground moraine. 



While not denying the possibility of water erosion with 

 a notch at the Pennsylvania Railroad crossing, yet over- 

 deepening by ice has been favored by Dr. Berkey and the 

 writer in their reports as consulting geologists to the Board of 

 Water Supply, but Professor W. O. Crosby, also reporting to 

 the Board as consulting geologist, favors water erosion. 



*G. S. Sogers. The Character of the Hudson Gorge at New York City, 

 School of Mines Quarterly, xxxiii, 26-42, 1910. 



Columbia University, New York City. 



