12 Spencer — Great Canyon of the Hudson River, 



the cause of such a submarine feature, except as a last resort 

 from accepting the evidence as is set forth in this paper, unless 

 such a reason can be shown to exist other than by negative 

 or insufficient evidence. 



As for submarine glacial erosion, I have shown that there 

 are no features of the shelf suggestive of the occurrence of 

 glacial action, even though such reached to Long Island and 

 New Jersey. Furthermore it could not have possibly extended 

 to the great depths of the canyon and the continuing valley. 

 Of this question Dr. Nansen says in his great monograph : — 

 "The drowned valley of the Hudson River cannot possibly 

 have been re-opened by submarine glacial erosion, it is too 

 long and narrow and deep." (Op. cit. p. 192.) Its analogues 

 of the tropics are situated beyond glacial action. 



Of the drowned valley of the Gulf of St. Lawrence, Prof. 

 N. S. Shaler also writes, but I do not remember whether he 

 considers the then discovered Hudson River canyon. 



Returning now to long accepted iluviatile origin of the sub- 

 marine channel, let me call attentiqn to the very close resem- 

 blance of the canyon, as shown on the map, to the gorge of 

 the Niagara, also excavated out of level plains, far from 

 mountains, in front of which are great slopes to lower levels. 

 Rut this portion of the Hudsonian canyon is thirty miles long 

 and reaches to thousands of feet in de]3th, while that of the 

 Niagara is only seven miles in length and now 440 feet deep. 

 So too the canyon of the Hudson is just like the barrancas on 

 the high plateaus of Mexico and Central America, starting in 

 level plains, and then suddenly transforming themselves into 

 rapidly descending canyons, which later widen out into such 

 valleys (as w*e may see in the east, which have reached more 

 mature forms), whose descent from the plateaus of thousands 

 of feet in height is not by regular gradients, but commonly by 

 a succession of great steps. 



The Magnitude and the Time of the Great ^Elevation. 



While it must have taken the Hudsonian canyon many 

 milleniums to have been formed, yet it presents a youthful 

 feature, in strong contrast with the valleys on the eastern side 

 of the American continent, while its submerged marginal shelf 

 is not deeply indented with its surface scored into a succession 

 of ridges and hollows. Even though many of the underlying 

 rocks may be of a resisting nature, yet the period of canyon- 

 making must have been one of limited duration. This is 

 further suggested when considering the size of the Hudson 

 river, which probably carried down glacial waters and detritus 

 for a portion of the period. Outside the limit of the Hud- 

 sonian river, the surface of the now submarine plain was 



