GEOLOGICAL HISTORY OF NEW YORK. 657 



ation of this long line of drainage. As has been remarked, it is of 

 great and yet unknown depth. The clay by which it is partially filled 

 has been penetrated to a depth of about 100 feet along its margins. 

 How 'deep it is in the middle portion can only be conjectured ; but 

 Hell Gate channel, which has been kept comparatively free by the force 

 of the tides, is in places known to be nearly 200 feet deep ; and, since 

 this is a channel of erosion formed by a stream draining into the Hud- 

 son, the ancient bed of the Hudson must be still lower. 



From the depth and distinctness of the old river-course on the sub- 

 merged plain outside of the Narrows, we may reasonably infer that 

 the old channel at New York is not much less than 300 feet deep. 



We are compelled to conclude from these and other facts of similar 

 import: 1. That the topographical features of the vicinity of New York 

 were for the most part fashioned by the erosion of a system of water- 

 courses which, in preglacial times, when the continent was higher than 

 now, cut their valleys much deeper than would now be possible. 



2. That there was here a group of hills composed of crystalline 

 rocks, a sort of spur from the Alleghany belt, and that this range of 

 hills was then seventy or eighty miles inland from the ocean, separated 

 from it by a plain similar in its topographical relations to that which 

 lies between the highlands of our Southern States and the present 

 shore of the Atlantic. 



3. At the period under consideration a river draining the basin of 

 the Great Lakes, and in size the second on the continent, followed the 

 course of the Mohawk and Hudson, and, passing through the New York 

 hills, there left the highlands and flowed quietly on to the ocean. 



4. Where New York Harbor now is, this great river received two 

 important tributaries one from the east through Hell Gate channel, 

 which joined it at the Battery, the other from the west through the 

 gorge of the Kill van Kull. Of these, the first is now represented by 

 the Housatonic, then a larger stream, with a longer course and more 

 tributaries ; the second was formed by the Passaic and Hackensack, 

 which united at the head of what is now Newark Bay, arid emptied 

 into the Hudson at the entrance to the Narrows. The junction of 

 these two considerable branches so near each other seems to have pro- 

 duced the expansion of the valley which is now New York Harbor. 

 This must then have been a very picturesque spot, as its outlet ocean- 

 ward was a narrow pass bordered by the hills of Staten and Long Isl- 

 and, 500 feet in height. On the north, it was overlooked on one 

 hand by the great wall of the Palisades, which rose 700 feet above the 

 river; on the other, by a bold shoulder or headland, 400 feet in height, 

 now New York Island, then a promontory, which separated the Housa- 

 tonic and the Hudson to their junction at its southern extremity. 



5. After the lapse of unnumbered ages, during which this nook 

 among the hills was slowly prepared for the important part it was to 

 play in the history of the yet unborn being man a quiet subsidence 



vol. xiii. 42 



