THE work entitled "The Albert N'yanza Great Basin of the Nile,"published in 1866, has given an account of the equatorial lakesystem from which the Egyptian river derives its source. It hasbeen determined by the joint explorations of Speke, Grant, andmyself, that the rainfall of the equatorial districts suppliestwo vast lakes, the Victoria and the Albert, of sufficient volumeto support the Nile throughout its entire course of thirtydegrees of latitude. Thus the parent stream, fed by never-failingreservoirs, supplied by the ten months' rainfall of the equator,rolls steadily on its way through arid sands and burning desertsuntil it reaches the Delta of Lower Egypt.
It would at first sight appear that the discovery of the lakesources of the Nile had completely solved the mystery of ages,and that the fertility of Egypt depended upon the rainfall of theequator concentrated in the lakes Victoria and Albert; but theexploration of the Nile tributaries of Abyssinia divides the Nilesystem into two proportions, and unravels the entire mystery ofthe river, by assigning to each its due share in ministering tothe prosperity of Egypt.
The lake sources of Central Africa support the life of Egypt, bysupplying a stream, throughout all seasons, that has sufficientvolume to support the exhaustion of evaporation and absorption;but this stream, if unaided, could never overflow its banks, andEgypt, thus deprived of the annual inundation, would simplyexist, and cultivation would be confined to the close vicinity ofthe river.
The inundation, which by its annual deposit of mud has actuallycreated the Delta of Lower Egypt, upon the overflow of which thefertility of Egypt depends, has an origin entirely separate fromthe lake-sources of Central Africa, and the supply of water isderived exclusively from Abyssinia.
The two grand affluents of Abyssinia are, the Blue Nile and theAtbara, which join the main stream respectively in N. lat. 15degrees 30 minutes and 17 degrees 37 minutes. These rivers,although streams of extreme grandeur during the period of theAbyssinian rains, from the middle of June until September, arereduced during the dry months to utter insignificance; the BlueNile becoming so shallow as to be unnavigable, and the Atbaraperfectly dry. At that time the water supply of Abyssinia havingceased, Egypt depends solely upon the equatorial lakes and theaffluents of the White Nile, until the rainy season shall againhave flooded the two great Abyssinian arteries. That flood occurssuddenly about the 20th of June, and the grand rush of waterpouring down the Blue Nile and the Atbara into the parentchannel, inundates Lower Egypt, and is the cause of its extremefertility.
Not only is the inundation the effect of the Abyssinian rains,but the deposit of mud that has formed the Delta, and which isannually precipitated by the rising waters, is also due to theAbyssinian streams, more especially to the river Atbara, which,known as the Bahr el Aswat (Black River), carries a largerproportion of soil than any other tributary of the Nile;therefore, to the Atbara, above all other rivers, must the wealthand fertility of Egypt be attributed.
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