292 The Auicrican Geologist. November, 1904. 
THE SUBMARINE GREAT CANYON OF THE 
HUDSON RIVER. 
By J. W. Spencer, Washington, D. C. 
(Submitted to Eighth International Geographic Congress, New York.) 
(Advance Notice.) 
More than forty years ago, professor J. D. Dana first ex- 
plained the channel of the continental border, extending from 
New York for more than a hundred miles, as the former 
course of the Hudson river, at a time when the continent stood 
higher than now (then known to be only 720 feet deep). In 
1885, professor A. Lindenkohl discovered that the sliallnw clian- 
nel became a canyon, and reached a depth of nearly 3,000 feet, 
but with an apparent barrier across it. Since then, both pro- 
fessor Dana and Dr. Upham applied this feature as evidence 
of continental elevation of the Glacial period. On the evi- 
dence of incomplete soundings, in 1897 I ventured to point 
out that the valley was traceable to a depth of 12,000 feet. 
Recently I have found authentic evidence, from s'oundings by 
Lt. Com. Tanner, that immediately beside the sounding re- 
sponsible for the barrier hypothesis, he obtained another, 
which revealed a deep canyon, at this point, where the former 
depth had been taken on its side only. Then in the next four 
miles the floor drops in a step of 2,000 feet. Here another 
deep sounding, close upon an older and shallower one. shows 
a depth of 4,800 feet below sea level wdiere the continental 
slope is submerged only 1,000 feet. Accordingly, there is a mag- 
nificent canyon, 3,800 feet deep, which at a little below its top is 
less than tAvo miles wide. Just beyond is a tributary. This great 
depth is 31 miles from the head of the gorge, incising the 
level floor of the continental shelf, having two right-angled 
turns in its course. Beyond this point, the gorge is defined 
and extends at least 11 miles farther. At 48 miles, the right 
wall of more than 2,000 feet becomes less precipitous, showing 
that the canyon is widening into a valley with the depth of 6,200 
feet below the surface at a point not in its center. I have 
taken the end of the more precipitous walled gorge at 
about six miles above this point, and the depth below the 
surface between 6,000 and 7.000 feet. The details of the 
right wall from this point onward are sufticiently full, but on. 
