48 GEOLOGICAL RESEARCHES IN 



Taming (fu) and the sea, Avliich are also given. Previous to this, under Wentih, 

 about 160 B. C, there was a breach formed at Yentsin near Kaifung. 



Map No. 5 gives the second great change in the course of the "river of Yu," 

 which occurred about 11 B.C., and was caused apparently by the blocking up of 

 the channels leading to the Pei Ho. 



Map No. 6 shows the channels as they existed during the Tang, and five succeed- 

 ing dynasties, tUl the beginning of the Sung dynasty. 



A note on the map of Chin Hu Wei says, " the course of the river remained the 



same from the time of Muag Ti (Tung Han dynasty) A. D. 70 tiU under 



Jin Tsung, A. D. 1034, when a break occurred at Plunglung, and another, fourteen 

 years later, A. D. 1048, at Changwu, and the river of the Han and the Tang was 

 entirely destroyed. The map covers a period of 977 years." 



Map No. 7 (PI. 5) represents the coiu'ses, under the Sung dynasty, from A. D. 

 1048 to A. D. 1194, a period of 146 years. 



Map No. 8 records the course during the Kin dynasty. All the former channels 

 appear blocked up, and the river, after entering Lake Lo, near the summit-level of 

 the present Imperial canal, is seen to flow off" to the N. E. through the Tatsing 

 river, and to the S. E. through the Sz' river.\ Lake Lo appears from the observa- 

 tion of Clarke Abel, and from Chinese measurements, to be about 150 feet above 

 the sea. 



Map No. 9 shows the condition of the river under the Yuen and Ming dynasties, 

 together with the Grand canal, a condition which seems to have remained substan- 

 tially the same till within the last ten or fifteen years. 



In early times the Yangtse entered the sea by three arms called the Sankiang, 

 i. e., "Three Kivers;" and Chin Hu Wei has given a map of these, founded on the 

 opinions of early authorities. I have indicated them on map No. 1 of the series. 



A glance at the nine maps of the delta courses will show how widely separated 

 have been the limits of divergence of the arms of the Hwang Ho, within the past 

 3000 years. A mighty river, ever turbulent, subject yearly to an enormous increase 

 in volume, an increase regulated rather by the amount of precipitation in the distant 

 Kwenlun mountains, than by the local climate, it has ever been the terror of the 

 countless millions through Avhose midst it flows. 



From the earliest times an immense force has been at Avork to keep it from break- 

 ing through its dykes, or, Avhen this has happened, to guide and retain it between 

 new embankments. The quantity of solid material carried by the river and deposited 

 along its course, is so great that its bed is rapidly raised, and appears to have been, 

 before the last change, higher than the adjacent country. 



Biot says, " it is certain that the bed of the river, from Hwaiking to the sea, is 

 higher than the adjoining country." 



Several times, during the great wars that have preceded the downfall of dynas- 

 ties, this condition of the river has been turned to account as a weapon of offence. 

 Breaking the embankments has been made to accomplish, almost instantaneously, 

 by the destruction of hundreds of thousands of inhabitants, conquests that had been 

 delayed by years of brave resistance. 



From the earliest time of colonization on the delta-plain, the task of keeping the 



