v / 
EROSION HISTORY OF THE YANGTZE RIVER 129 
peaceful stream whose sluggish but determined current meets 
the sea, but it is churned and agitated at frequent intervals by 
roaring rapids and swirling eddies. As one proceeds, the walls 
become higher, and back from the river the mountains stand out 
in bold relief, carved in fantastic forms. Between the top of 
the gorge walls and the base of the flanking mountains there is 
an area of flat surface described as follows : ‘ 1 The cliffs which 
wall the Yangtze gorges are sometimes sheer for 2,000 feet, 600 
Fig. 4. “The cliffs ***** are sometimes sheer for 2000 feet.” The upper end 
of the upper gorge, looking down stream. 
meters, as estimated in passing. Above that altitude they recede 
in a decided bench above which the mountains rise 2,000 to 3,000 
feet, 600 to 900 meters, higher. It is probable that the level 
3,000 feet, 900 meters, above the river is the floor of the valley 
which was occupied for some length of time prior to the last 
sinking of the canyon. Since the pause at that stage permitted 
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