GLACIAL AND POST-GLACIAL HISTORY 



453 



SUBMERGED CHANNEL OF THE HUDSON. 



The submerged channel extends from Troy, the hmit reached by 

 the tides, through the Narrows of Brooklyn and beyond out to the 

 outer edge of the overwash plain fronting the Brooklyn moraine. 

 Beyond this there are a number of channels, but none can be con- 

 sidered a continuation of the channel through the Narrows until 

 opposite Sandy Hook, where a channel begins that can be traced 

 southeastward to the forty-one-fathom line. (See Fig. 17.) Whether 

 this should be considered a continuation of the Narrows channel will 

 be discussed later. 



Extra-morainic channel. — This 

 channel can be traced from a 

 point opposite Sandy Hook south- 

 eastward and ends at the forty- 

 one-fathom line,' eighty nautical 

 miles from Sandy Hook. In depth 

 below the plain into which it is 

 cut it varies from zero to 90 feet. 

 Ten miles from Sandy Hook it has 

 a depth of 48 feet, and increases 

 south-eastward to 90 feet, and 

 again decreases to zero feet, at the 

 forty-one-fathom line. Beyond this channel, after an interval, there 

 is a much deeper ravine, with which this paper is not concerned. It 

 is 25 miles long, 3 miles wide, and has a maximum depth of 2844 

 feet.^ 



Channel inside the moraine. — The channel inside the moraine is 

 covered by the waters of the Hudson estuary which vary from 10 to 

 216 feet in depth. On the whole, the minimum depth increases from 

 Troy to just north of Newburg. South of here the water is shallow 

 to the Highlands. In the Highlands it is deep, and from North 

 Haverstraw south it is shallow again, but on the whole grows deeper to 

 the Narrows. Throughout its entire length there is a very great 

 variation in the depth, however. There are certain "deeps" which 



Fig. 17. — Submerged extra-morainic 

 channel of the Hudson. 



G, shallower channel to forty-one fathom line; 

 H, deeper channel. [Taken from map by A. 

 Lindenkohl in the U. S. Coast and Geodetic Survey 

 Report ioT 1884.]^ 



'A. Lindenkohl, American Journal of Science, Vol. CXXIX {li 

 = Lindenkohl, loc. cit. 



PP- 475- 



