126 W. M. Davis— Gorges and Waterfalls. 
hills of moderate slope about five hundred feet high on either 
i Sudd 
side. Suddenly and without apparent cause the stream turns 
from this broad trough and enters a narrow gorge with steep 
rocky walls not less than three hundred feet high, in which it 
continues for about five miles on a circuitous course, until it 
example for our consideration. ‘There 
strong obstacle placed in the old matured channel to cause the 
creek to leave a course so well suited to its wants; to turn from 
what it had been patiently at work preparing for unnumbered 
thousands-of years, and cut out a new passage through the hills; 
and Professor Orton, who first, some ten years ago, gave 4 
detailed description of this notable locality,* concludes that the 
obstacle was the ice of the glacial sheet that had its margin, 
during its farthest southern advance, in this district. The 
upper waters of the creek must have been held back by the ice, 
aided by the drift, and risen behind them into a lake, whose 
level is marked by heavy terraces of stratified drift, until a line 
of overflow was found around the barrier; and along this over- 
ing hills. But sometimes the streams found their best escape 
- along new lines of flow; there they have abandoned the old 
channels and wrought out new ones, and these constitute most 
of the narrow gorges in the cliff rock that make so notable 4 
feature in the scenery of this region. 
The Falls of St. Anthony in the Mississippi at Minneapolis 
and the gorge below them are shown by Professor N. H. Wit 
* Geological Survey of Ohio, ii, 1814, 653. ‘ 
+ Geol. Ohio, i, 460. . 
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