Spencer — Great Canyon of the Hudson River. 7 



cove. Beyond this point, where the sounding is more than 4806 

 feet deep, the canyon feature must continue for several miles 

 at least. I have carried it to the 42-mile point, where the con- 

 tinental shelf is submerged to 3000-3500 feet. At this depth 

 we have several soundings which show that the 3000-foot 

 isobath continues in a direct line as if across the canyon with- 

 out any known suggestion that it sweeps round into the form 

 of a broadened embayment. Its parallelism to the 500-foot 

 line of the edge of the shelf shows the remarkable regularity 

 of this zone of the great slope. There is also suggested the 

 remains of a shelf or bench of depth corresponding to the 

 Blake plateau south of Cape Hatteras. 



Within a few miles the canyon appears to broaden out, and 

 yet at 48 miles there is a steep cliff of 2000 feet or more on its 

 southern side. Here the floor exceeds a submergence of 6126 

 feet, as the measurement is not in the center of the valley, nor 

 have we obtained the sounding on the opposite northern edge, 

 the last in the gorge being 4800 confined within walls of 3800 

 feet, though the walls are known on both sides lower down. 

 Indeed this depth is still below that of the continental slope at 

 48 miles. Evidently the canyon section must reach to a depth 

 of from 6000 to 7000 feet, which also corresponds to the deep 

 valley of the Connecticut. (C on map.) 



Beyond the canyon section is the southern side of the 

 extended valley, demonstrated by a line of soundings, though 

 not at its summit. The four soundings at about 8688 feet are 

 specially important as proving the continuation of the Hud- 

 sonian valley. The first of these is at 63 miles. At 67 miles 

 the lateral bank is at least 624 feet high (probably 1000 feet at 

 least above the floor), and our record carries the valley to 71 

 miles from the head of the gorge. The end of this lower 

 reach does not exceed 14 miles in width, but fuller soundings 

 may limit it to 8 or 10 miles. . Thus the valley is shown to 

 exist to a depth of 9000 feet. 



Beyond this point there are no soundings in the line of the 

 valley, but lateral ones on both sides are suggestive, and at 100 

 miles east of this study, at a little less than 12,000 feet, is an 

 embayment of 30 miles in breadth, with the depth of a few 

 hundred feet. This cannot be a meaningless feature, though 

 not part of the present analysis. 



The breadth of the canyon hardly exceeds a mile at its head, 

 but it soon widens to two miles or more. From the second 

 turn (see map) a breadth of four miles is maintained for the 

 outer canyon. The deeper inner gorge is reduced to a width 

 of one mile or less, and is more sinuous than the outer. 

 Beyond the tributary it is wider, five or six miles, though pos- 

 sibly more, as the next sounding is farther away, but a little 



