inland portion of it above New York city. According to
Mr. A. Lindenkohl,* this submarine valley began to be
noticeable in the soundings ten miles southeast of Sandy
Hook. The depth of the water where the channel begins
is nineteen fathoms (114 feet). Ten miles out the chan-

* Bulletin of the Geological Society of America, vol. i, p. 564 ;
American Journal of Science, June, 1891.
196 MAN AND THE GLACIAL PERIOD.
nel has sunk ninety feet below the general depth of the
water on the bank, and continues at this depth for twenty-
miles farther. This narrow channel continues with more
or less variation for a distance of seventy-five miles, where
it suddenly enlarges to a width of three miles and to a
depth of 200 fathoms, or 1,200 feet, and extends for a dis-
tance of twenty-five miles, reaching near that point a
depth of 474 fathoms, or 3,844 feet. According to Mr.
Lindenkohl, this ravine maintains for half its length " a
vertical depth of more than 2,000 feet, measuring from
the top of its banks, and the banks have a nearly uni-
form slope of about 14°. The mouth of the ravine opens
out into the deep basin of the central Atlantic.
