24 THE GROWTH OF THE YANGTZE DELTA 



fall is less than an inch per mile which is flatter than one 

 in a hundred thousand. See Plate 3. 



The average discharge during the year is 1,050,000 cubic 

 feet per second. 



Tides. 



The powerful semi-daily tides of the Pacific Ocean 

 traverse the China Sea, advance up the Yangtze a distance of 

 450 miles, diminishing gradually from a range of 15 feet at 

 Spring Tide at Side Saddles until its daily effect is no more 

 apparent at Kiukiang, and this agent complicates the forma- 

 tion of this delta. It is quite different from the Nile or the 

 Mississippi. 



(a) Physiography. — The Yangtze emerges from the hills 

 which practically define its course at Chinkiang. The hills 

 on the right bank are the eastern extremity of the Nanking 

 System, and the hills on the left bank 10 miles inland at 

 Yangchow are the eastern extremity of the mountains form- 

 ing the northern divide. See Plate 4. 



The Yangtze Delta is roughly east to a line from Yang- 

 chow southwestward through Chinkiang thence southeast- 

 ward to Hangchow. The western border is defined by the 

 Langshans or mountains of South Anhwei terminating in 

 the Tung Kwan Shan, west of the Tai Hu and the Nanking 

 System. 



The general level of the plain is about the level of 

 ordinary high water, 12 to 15 feet above lowest low water 

 at Woosung Forts. The immediate shore is dyked consider- 

 ably higher than ordinary high water, but with an exception- 

 ally high river as in 1921, great areas of the plain are flooded. 



No accurate maps in the modern sense exist earlier 

 than 1842 — the British Admiralty Survey. 



(b) Hills in the Delta. — Besides the range of hills at 

 Kiangyin and around the Tai Hu Lake, there are several 

 other groups, at Kanpu and Chapu on the Hangchow Bay, 

 at Sungkiang in the center of the drainage basin, at Lang- 

 shan on the left bank of the Yangtze, and many island-like 

 hills Chinwangshan and Choshan near Chinshan, Quinsan 

 near the city that bears that name and Yahzashan near 

 Changan. See General Map. 



The group near Kiangyin are probably a prolongation 

 of the Nanking System, while the group along the shore of 

 the Hangchow Bay are the extensions of the coastal hills 

 at Hangchow. 



The isolated hills are mostly volcanic and partially buried 

 in the delta plain. 



