THE GROWTH OF THE YANGTZE DELTA 25 



(c) Depressions.— Between the two. mountain masses 

 that form the western border, there is a very low depression 

 extending westward from the western shore of the Tai Hu 

 to the Yangtze at Wuhu. This depression is divided about 

 midway by a ridge of loess forming a watershed, a series of 

 lakes to the west drain into the Yangtze, while those to the 

 east have either formerly been a part of the Tai Hu or drain 

 into that lake. 



On the northern side of the Yangtze Eiver a belt of 

 swampy land forms almost a continuous sheet of water. 

 On the southern side, there is also a continuous lake area. 

 The drainage system of these lakes is also complicated, for 

 every lake has more than one outlet. 



\d) The Tai Hu,— The Tai Hu lies at the foot of the 

 great mountain system which forms the western border of 

 this great plain. Within the perimeter of the lake there 

 are some ninety hills rising to heights of 1,500 feet. Its 

 surface is 4 feet above the mean sea level and about one 

 to two feet above the mean water level at Woosung in the 

 winter and the lake is in free communication with the sea 

 via the Tien Shan Hu and the Huangpu. Its depth is up 

 to some 8-10 feet. 



These facts tend to confirm the supposition that the 

 mountain range along the western Tai Hu is the western 

 extremity of the Delta, and that the Tai Hu was at one 

 time a part of the sea. 



The cutlets from the Tai Hu are on the east side. 

 They may be divided into three groups. The first group 

 consists of the channels into the Grand Canal to Soochow. 

 These empty into the Yangtze at Liuchiaho. 



The second group consists of two channels, one to the 

 north of, the other to the south of, Wukiang. These ulti- 

 ma: i !\ empty into the Soochow Creek. 



The third group consists of two principal channels which 

 eventually find their way into the Tien Shan Hu and the 

 Huangpu. These channels are all in communication with 

 each other and they all reach the Yangtze. 



The discharge of the lake is principally through the 

 Tien Shan Hu and thence through the Huangpu. 



The Growth of the Delta. 



In order to explain how this delta came into being, 

 let us consider the agent that is known to be active to-day 

 in extending the delta, i.e., the silt of the Yangtze, lhis 

 is the agent that is building banks, bars and shoals in the 



