DEPOSITS OF THE NILE. 601* 



hoariest antiquity, the greatest material blessing that nature ever 

 bestowed upon a people.* 



Deposits of the Nile. 



The Nile is larger than all the rivers of Lombardy together ;f 

 it di-ains a basin fifty, possibly even a hundred, times as exten- 



* Deep borings have not detected any essential difference in the quantity or 

 quality of the deposits of the Nile for forty or fifty, or, as some compute, for 

 a hundred centuries. From what vast store of rich earth does this river derive 

 the three or four inches of fertilizing material which it spreads over the soil 

 of Egypt every hundred years ? Not from the White Nile, for that river drops 

 nearly all its suspended matter in the broad expansions and slow current of its 

 channel south of the tenth degree of north latitude. Nor does it appear that 

 much sediment is contributed by the Bahr-el-Azrek, which flows through 

 forests for a great part of its course. I have been informed by an old European 

 resident of Egypt who is very familiar with the Upper Nile, that almost the 

 whole of the earth with which its waters are charged is brought down by the 

 Takazze. 



f From daily measurements during a period of fourteen years — 1827 to 

 1840 — the mean delivery of the Po at Ponte Lagoscuro, below the entrance of 

 its last tributary, is found to be 1,730 cubic metres, or 60,745 cubic feet, per 

 second. Its smallest dehvery is 186 cubic metres, or 6,569 cubic feet, its 

 greatest 5,156 cubic metres, or 183,094 cubic feet. The average delivery of 

 the Nile being 101,000 cubic feet per second, it follows that the Po contributes 

 to the Adriatic rather more than six-tenths as much water as the Nile to the 

 Mediterranean — a result which will surprise most readers. It must, however, 

 be admitted that there is no small discrepancy among geographers with regard 

 to such estimates. Duponchel, Hydrologie Agricole, pp. 60, 61, states the 

 mean delivery of the Rhone at 1,718 cubic metres per second, that of the Rhine 

 at 2,000 cubic metres. Elisee Recltjs, La Terre, i., p. 535, gives the delivery 

 of the Rhone as 2,603 metres per second, that of the Po as 1,735, and that of 

 the Rhine as 1,975. I suspect a typographical error here in regard to the Rhone. 

 Though the Po receives four-tenths of its water from lakes, in which the 

 streams that empty into them let fall the solid material they bring down from 

 the mountains, its deposits in the Adriatic are at least sixty or seventy per 

 cent, greater than those transported to the Mediterranean by the Rhone, which 

 derives most of its supply from mountain and torrential tributaries. Those 

 tributaries lodge much sediment in the Lake of Geneva and the Lac de Bour- 

 get, but the total erosion of the Po and its affluents must be considerably 

 greater than that of the Rhone system. The Rhine conveys to the sea much 

 less sediment than either of the other two rivers. — Lombakdini, CangiamenU 

 nella condizione del Po, pp. 29, 89. 



The mean discharge of the Mississippi is 675,000 cubic feet per second, and, 

 accordingly, that river contributes to the sea about eleven times as much water 

 as the Po, and more than six and a half times as much as the Nile. The dis^ 



