the Hudson and its Tributaries. 323 



ever, was abandoned for other reasons before any core-borings 

 seemed called for. 



Concluding .Remarks. — The great depth to bed-rock at the 

 Storm King crossing leads to some interesting lines of reflection. 

 We have no reason to think that the river has ever done 

 otherwise than flow down-grade to the sea along its present 

 channel. Some suggestions have been made of its diversion to 

 the Hackensack valley, but in this the writer and his colleague, 

 Dr. Berkey, who is very familiar with the local geology, have 

 no confidence whatever. For this region we believe in a rather 

 abrupt elevation of the land in the closing Tertiary which 

 brought about a deepening of stream channels to a point as 

 much below the present as the depths of the exploring holes, 

 above cited, indicate. The Hudson, however, obviously cut 

 much more rapidly than its tributaries, and with this the 

 temporary diversion of the drainage of the Great Lakes through 

 the Mohawk may have had some influence. The ice-sheet 

 served to still further accentuate the difference, and, as often 

 appears along a trunk glacier, left the tributaries as hanging 

 valleys. The drill-holes at Peggs Point prove that at this cross- 

 ing the gorge must be relatively narrow, but since there seems 

 no way of explaining the depths at Storm King by a gigantic 

 pothole or exceptionally deep, local scour, or any other reason- 

 able method other than water or ice erosion, the still undis- 

 covered gorge is inferred in the 1,040 ft. between the holes. 

 Since the Storm King granite is the hardest and most resistant 

 rock in the whole course of the river, if it has yielded anything 

 unusual it ought to form a reef rather than a depression. 



Doubtless the thought will come to a reader, as to the char- 

 acter of the Hudson valley opposite New York. Thus far 

 only the records of wash-borings have been published, and of 

 these the deepest is 300 ft. at a point 2,000 ft. off the bulkhead 

 at 57th street.* Yet there is reason to anticipate something 

 like 700 ft. or more to bed-rock, and the hope may be expressed 

 that some future exploration for an engineering enterprise will 

 give the actual determinations. 



Postscript. — Since July 15, when the above pages were completed, addi- 

 tional data have been obtained at the Storm King Crossing as follows (com- 

 pare fig. 16) : Hole 22 has caught the granite at 507', indicating that the 

 profile of the eastern bottom flattens from hole 19 to this point, more than 

 as sketched. Hole 20 is 626' and is in fine sand and clay. Hole 21 had 

 penetrated 4 to 5 feet in a granite ledge or bowlder when temporarily stopped 

 by the collision of a tow. Thus the extreme depth has not yet been reached 

 and appears to be beneath the middle of the river near Hole 20. 



August 31, 1908. 



* Cited by W. H. Hobbs in U. S. Geol. Survey Bulletin 270, p. 31, from 

 Ch. McDonald, Engineering News, xxxiii, 159, 1895. 



