GEOLOGIC HISTOEY OF CHINA— BLACKWELDER. 389 



have made deep valleys with intervening mountain ranges. Some 

 of the larger rivers, such as the Yangtze, maintained their courses in 

 spite of the slow uplifts directly athwart their courses. A result is 

 the magnificent series of gorges along the central Yangtze where the 

 great river has sawed its way through a slowly rising mass of hard, 

 complexly folded rocks. 



On the other hand, the broad areas which were depressed not only 

 below the general level of stream action, but below sea level, were rap- 

 idly filled with sand, loam, and clay washed doAvn out of the adjacent 

 mountains by the streams. The process of filling the depressions is 

 the exact complement of the process of etching out the highlands. No 

 doubt the rivers have been able in large measure to keep pace with 

 the sinking movement of the ground, so that great rivers like the 

 Hwang may have maintained perfectly graded courses across the 

 region of depression from the mountains to the sea. While thus en- 

 gaged in building up its channel, the river in time of flood frequently 

 breaks through its low banks, shifts its channel, and then begins to 

 fill up a new and hitherto lower part of its surroundings. By the 

 long continuance of this process of repeated shiftings and fillings. 

 the great eastern plain of China and many smaller plains have been 

 produced. It is here, where the population is densest and the rivers 

 least confined, that the devastation by floods and their attendant 

 famines is greatest. 



By this succession of events the surface of China is believed to have 

 reached its modern condition. We may now consider it piecemeal 

 and see how the existing geologic conditions, which are the result of 

 this long series of past changes, influence the habits, occupations, 

 and even mental traits of the people. Because space is limited and 

 also because I have not seen all the physiographic divisions of China, 

 it will not be possible for me, even briefly, to describe each of them. 

 A few are therefore selected to show the range of variety of the whole. 



The mountains of northeastern China, typified by the province of 

 Shantung, are unlike those of the rest of the country in several re- 

 spects. Although the individual peaks are often sharp and rocky, 

 they are generally separated by wide, flat-bottomed valleys. The 

 process of erosion has here gone so far that the rivers have already 

 carried away most of the land, leaving only isolated groups of low 

 mountains. The broad valleys accommodate a relatively large num- 

 ber of people, who congi-egate in the villages dotting the intermontane 

 plains. In contrast with most mountainous regions, travel between 

 the different valleys is comparatively easy here, because many of the 

 passes are but little higher than the plains themselves, and constitute 

 scarcely any obstacle to progress. Roads are plentiful, and so the cart 

 and the wheelbarrow are the principal vehicles for through traffic. 



