476 A, Lindenkohl— Geology of the Sea-bottom 
has developed the existence of this channel; and thus the 
question is opened—whether this channel was produced by a 
break in the strata as was the upper channel of the Hudson, or 
by the current of a river seeking an outlet to the ocean. The 
following facts bear upon the question. 
The first indications of the channel are found ten nautical 
miles east by south off Sandy Hook at a depth of 19 fathoms, 
After following a southerly course for about ten miles, the chan- 
nel takes an easterly turn in the next five miles; from the dis- 
tance of fifteen miles (twenty miles in a direct line from the 
ook) it maintains a straight course (60° S. E.) to its bar, 
which is eighty miles from the Hook. 
From the head of the channel to the bend, tbe top of the banks 
remains at about an even level of 18 fathoms depth, while the 
channel increases in depth from 19 fathoms to 36 fathoms. The 
average slope of the banks is one degree, and the width of the 
enclosed channel from three quarters of a mile to a full mile; 
in the bend this slope is increased to three degrees, and the width 
contracted to one eighth of one mile. 
The banks maintain the same height on both sides, and are, as 
also is the bottom, composed of a sandy clay overlaid by 4 
crust of sand and gravel which spreads continuously over the 
adjacent flats. This clay is very uniformly described by the 
surveyors as “ blue clay” in the upper channel and “green mud 
in the lower channel. The bar (at seventy-five nautical miles 
from the Hook) is composed of fine sand. At the distance of 
eighty-five miles the channel reappears as a deep ravine and it 
will be described separately. The cross sections of the chan- 
nel, at intervals of ten miles starting from Sandy Hook, taken 
from the recent survey, are here given: 
Depth of channel Distance, from top of 
: ’ nks 
ooatnies, §—"StSganc’! UF Ran ataae vel ePinome 
10 25 8 
20 35 20 15 
30 37 22 15 
40 42 rif 15 
50 41 30 11 
43 36 7 
an 43 38 7 
75) (41) 39 
80 43 4 0 
) y feet. 
This sandy clay is believed to be identical with the Tertiary 
