Along the banks of the Yangtse, and for many miles along the Hwang ho, great levees have been built, some-times in reinforcing series of two or three at different distances back from the channel where the stream bed is above the adjacent country, in order to prevent widespread disaster and to limit the inundated areas in times of unusual flood. In the province of Hupeh, where the Han river flows through two hundred miles of low country, this stream is diked on both sides throughout the whole distance, and in a portion of its course the height of the levees reaches thirty feet or more. Again, in the Canton delta region there are other hundreds of miles of sea wall and dikes, so that the aggregate mileage of this type of construction works in the Empire can only be measured in thousands of miles. In addition to the canal and levee construction works there are numerous impounding reservoirs which are brought into requisition to control overflow waters from the great streams. Some of these reservoirs, like Tungting lake in Hupeh and Poyang in Hunan, have areas of 2,000 and 1,800 square miles respectively and during the heaviest rainy seasons each may rise through twenty to thirty feet, Then there are other large and small lakes in the coastal plain giving an aggregate reservoir area exceeding 13,000 square miles, all of which are brought into service in controlling flood waters, all of which are steadily filling with the sediments brought from the far away uncultivable mountain slopes and which are ultimately destined to become rich alluvial plains, doubtless to be canalized in the manner we have seen. There is still another phase of these vast construction works which has been of the greatest moment in increasing the maintenance capacity of the Empire,--the wresting from the flood waters of the enormous volumes of silt which they carry, depositing it over the flooded areas, in the canals and along the shores in such manner as to add to the habitable and cultivable land. Reference has been made to the rapid growth of Chungming island in the mouth of the Yangtse kiang, and the million people now finding homes on the 270 square miles of newly made land which now has its canals, as may be seen in the upper margin of Fig. 52. The city of Shanghai, as its name signifies, stood originally on the seashore, which has now grown twenty miles to the northward and to the eastward. In 220 B. C. the town of Putai in Shantung stood one-third of a mile from the sea, but in 1730 it was forty-seven miles inland, and is forty-eight miles from the shore today. Sienshuiku, on the Pei ho, stood upon the seashore in 500 A. D. We passed the city, on our way to Tientsin, eighteen miles inland. The dotted line laid in from the coast of the Gulf of Chihli in Fig. 53 marks one historic shore line and indicates a general growth of land eighteen miles to seaward.