106 ON EROSIONS OF THE EARTH'S SURFACE. 



that much of it was effected since the drift period. Most likely it is a valley of 

 very great antiquity. 



15. High Falls on the Hudson, in Luzerne, Warren county, New York. — I depend 

 entirely upon Professor Emmons' account of this gorge, in his Report on the Second 

 Geological District, p. 188. It lies at the junction of gneiss and Potsdam sandstone. 

 It is a mile long, and the wall of gneiss rises in some parts of this distance to the 

 height of 100 feet. From Professor Emmons' description, I should judge this to 

 be a genuine example of river erosion. 



16. Little Falls on the Mohawli, Oneida county, Neio York. — The rock here is 

 gneiss, through which the river has cut its way. Professor Vanuxem says that on 

 its east side the walls of rock are 100 feet high, and that westward it gradually 

 declines in height. The length of the gorge I am unable to state. It is an 

 unequivocal example of river erosion : for pot-holes are found at various heights 

 in its walls. — Yanuxems Report on the Geology of the Third District, p. 208. 



17. Gorge on the Oltaqueechy river, at Hartford, in Vermont. — The river here 

 passes through a gulf a mile long, one side of which is 100 feet high and continu- 

 ous : the opposite side being more irregular. Falls exist at Queechy village, 20 

 feet high, a mile above the gulf, with pot-holes on the sides and the bottom. Be- 

 tween these and the gulf are meadows, with seven terraces on one side of the 

 river, and four on the other, as given in my paper on Terraces. Probably to 

 determine the amount of erosion here, we must add the length of the gulf to its 

 distance below the falls. But my examination of the spot was so hasty that I 

 could not give a sketch of its features. The walls forming the gulf are mica slate, 

 with trap, which Professor Hubbard supposes to have once occupied the gorge. — 

 American Journal of Science, vol. IX., New Series, p. 160. 



18. Grandfather Bull's Fcdls, on Wisconsin river, in gneiss, mica slate, and trap. — 

 The cut is one and a half miles long, and 150 feet deep. Professor Owen describes 

 another cataract a mile further up the stream, in trap; and the two may perhaps 

 have formed parts of one continuous erosion, though more probably the work may 

 have been going on contemporaneously at both places. Owen's Report to the 

 Government, in 1848, p. 97. 



19. Gates of the Rochy Mountains. — This remarkable chasm lies near the head 

 waters of Missouri river, where it emerges from the Rocky Mountains. The 

 average height of the walls is 1200 feet, and the chasm nearly six miles long. I 

 am not sure that the rocks are crystalline, or hypozoic. — Encyclopedia of Geogra- 

 phy, vol. III., p. 373. 



20. Sixty miles easterly from the Gates of the Rochy Mountains the Missouri forms 

 a succession of cataracts, second only to Niagara. — In the space of seventeen miles, 

 the river falls 360 feet, beside the great fall of 90 feet. I refer to this place as 

 probably affording, like the last, a striking example of river erosion. — Encyc. Geog., 

 vol. III., p. 373. 



21. Robert Maclagan, Esq., of the Bengal Engineers, who has resided ten years 

 near the Himalaya Mountains, informs me that on the Sutlej river, there is a gorge 

 through gneiss, as much as 1500 feet deep and a mile long. Since his return to 

 Europe he has sent me the following letter on this subject : — 



