Engineering Wonders of the World
Volume III

 242 ENGINEERING WONDERS OF THE WORLD. THE SOLANI AQUEDUCT, WHICH CARRIES THE GANGES CANAL OVER THE SOLANI RIVER. It has 15 arches of 50 feet span, is 195 feet broad, and passes a stream of water 172 feet across and 9 feet deep. into the cribs till its top is at the level of the water which, during construction, had been flowing over it. The boulder dam when complete is, of course, very leaky. This is remedied partially by sink- ing grass mattresses on the up-stream face, and throwing on to them boulders, shingle, and soil until an almost watertight embankment has been formed, to direct the river into the channel feeding the canal. It may seem strange that so primitive a structure should be a mainstay of the prosperity of a large tract of country. But so it is, and the canal has worked effectively for half a century. The Ganges Canal has a maximum capacity of 7,000 cubic feet a second. This great vol- ume of water is carried by level crossings through some rivers, over The Solani an(j jn aqueducts, the Aqueduct. most notable of which—that over the Solani—has fifteen arches of 50-foot span, is 195 feet broad, and gives passage to a stream 172 feet broad and 9 feet deep. We may notice that in some cases a river is led over a canal; for instance, a river 400 feet The Forma- tion of Deltas. broad and 9 feet deep in flood crosses the Sirhind Canal at a height of 24 feet. On the eastern coast the rivers, as they approach the sea, become deltaic. In their lower reaches the reduced velocity of the stream causes the matter eroded in swifter upper reaches ,to be deposited, and so raises the bed until the water overflows. The silt is then deposited on the land, the general level of which rises until the water is once more confined. This process is repeated along the banks and at the river’s mouth until a great fan-shaped body of land has been pushed out into the sea, traversed by the several branches into which the river has divided. These branches run along the ridges of the country, a condition of affairs which is ideal for irrigation. In the delta of the Godaveri a weir spans the river at Dowlaishweran, holds up the level of the water, and compels the stream to flow into three main canals. These supply many branch canals, which feed many more dis-