SUSQUEHANNAN AND DELAWAREAN VALLEYS 213 



it becomes precipitous, which is like that near Flemish cap, off cape Hat- 

 teras. At various points are suggestions of submarine plateaus in the 

 slope, owing to the occurrence of somewhat extensive plains with only 

 slight gradients— for example, southeast of New Jersey, between the con- 

 tours of 9,000 and 10,500 feet, which are here some 60 miles apart. 



SUSQUEHANNAN VALLEY 



In the margin of the continental shelf in front of Chesapeake bay 

 thefe is a strongly marked indentation corresponding to it. Here at 

 some distance within the 600 line connecting the promontories on its 

 two sides the depression or valley reaches depths of 4,686 and 5,154 feet, 

 enclosing a cul-de-sac or gulf, having a still farther descent to 6,420 feet 

 below sealevel. Some 15 miles farther outward the valley reaches to 

 more than 9,846 feet, thus making known another abrupt step in it. 

 From this point the valley descends only about 900 feet in the next 30 

 or 40 miles, but it has a depth of 1,500 feet below the floor of the adja- 

 cent continental slope. In this locality an outlying fragment of a sub- 

 marine plateau appears at about 5,000 feet below sealevel, and overhangs 

 by nearly 5,000 feet the adjacent valley to the north ; but the valley 

 bends round to the east of this promontory, where it has descended to 

 the great depth of 8,000 feet below this fragment of a submarine table- 

 land, and has a depth of 12,840 feet below sealevel at a distance of 60 

 miles from the head of the cul-de-sac or cove, indenting the edge of the 

 continental shelf. About 30 miles farther it enters an embayment shown 

 by the 15,000-foot line. This embayment has a length of 150 miles and 

 .a breadth of 70 miles, with a depth from 1,200 to 2,400 feet below the 

 floor of the lower plains of the continental slope. Thus the Susque- 

 hannan valley occurs all the way down to oceanic depths. 



THE DELAWAREAN VALLEY 



Mr Lindenkohl first called attention to a cul-de-sac of 2,376 feet inside 

 the 600-foot contour in front of Delaware bay. At a point about 95 

 miles from cape May, in the same direction, incomplete soundings show 

 the valley reaches to 3,000 feet below sealevel, where the adjacent conti- 

 nental slope is only 1,200 feet below the surface, and 10 miles farther 

 the depth of the channel is 6,066 feet, or about 1,200 feet deeper than the 

 neighboring sea bottom. For the next 90 miles the valley is shown in 

 the contours, and at this distance its depth is 11,256 feet below sealevel, 

 or more than 1,000 feet deeper than the adjacent continental slope. Some 

 50 miles farther it enters the Susquehannan embayment, as already men- 

 tioned. A little farther north than that of the Delaware, Mr Lindenkohl 



