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THE POPULAR SCIENCE MONTHLY 



Fig. 31. A Valley in the Central Ranges. In the foreground are a series 

 of terraced rice fields now filled with water. 



sary for the boatmen to pole around the cliff or to zigzag from one side 

 of the river to the other to take advantage of every foothold. 



Through the central part of this mountain uplift, the great Yang-tze 

 River, which in its lower course readily accommodates large ocean- 

 going vessels, has carved a succession of superb gorges. In many 

 places the gray limestone walls rise from 3,000 to 4,000 feet above the 

 river, and the stream is compressed into less than a tenth of its usual 

 width. Difficult and dangerous as are these canyons, beset with rapids 

 and whirlpools, they afford the only ready means of communication 

 between eastern China and the fertile basin of Sze-chuan, which lies 

 west of the Central Eanges. 



Without the highway of the Yang-tze, this great province, four 

 times as large as Illinois and with more people than all of our states 

 east of the Mississippi Eiver, would be unable to export its many rich 

 products or to enjoy the commerce of outside provinces and nations. 

 It has been effectually barred off from India and Burma by the succes- 

 sion of high ranges and deep canyons which appear to be due primarily 

 to the great epoch of folding in the Miocene period. Sze-chuan is a 

 broad basin which has never been depressed low enough to force the 

 streams to level its bottom with alluvial deposits, as in the Yellow 

 Eiver plain to the east; nor does it seem to have been elevated into a 

 high plateau which would have been carved by many streams into a 



