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THE POPULAR SCIENCE MONTHLY.
stream runs through unstratified rocks, in a district well supplied with rains, the walls or banks of the stream are cut down in more gentle slopes.
For purposes of discussion, it will be convenient to call the deep
Section of Wall in the Grand Cañon.
channels of streams through table-lands, in arid climates, cañons; and the deep channels of streams through heterogeneous beds, in a moist climate, water-gaps, or narrows, and ravines.
