52 NORTH-EAST AFRICA. 



appearance of sparkling water. But in tlie lower bed of the Atbara a few pools 



are scattered here and there. They owe their existence partly to the hollows that 



the eddies have excavated many yards below the normal bed, and partly to the trees 



that line the bank preventing the water from evaporating. In these pools, some 



more than half a mile in length, others reduced to an extent of a few square yards, 



are crowded together, in a space much too small for their mutual ease and safety, 



all the river fauna — fishes, turtles, crocodiles, and even the hipjiopotamus ; the wild 



animals resort likewise to these pools teeming with life, and every palm and every 



thicket along the bank has its colony of birds. In most of the rivers on the plain 



the water brought back with the rainy season returns gently into its channel. 



Preceded by a current of air, which causes the foliage along its banks to thrill with 



life, it advances with a sound like the rustling of silk. The first sheet of water is a 



mere mass of yellowish foam mixed with débris of all sorts ; following this mixture 



of mud and water comes a second wave, the true fluvial stream ; then appears the 



normal current, towards which the animals rush to quench their thirst. But the 



powerful volume of the Atbara rushes on like an avalanche ; when it again fills its 



bed, it is not by a slight and gradual advance, but by a sudden rush of water 



sweeping everything before it. The traveller sleeping on its sandy bed is suddenly 



awakened by the trembling of the earth, and by an approaching roar like that of 



thunder. " El Bahr ! el Bahr ! " shout the Arabs, and there is scarcely time to 



rush to the bank to escape the advancing flood, driving before it a mass of mud, 



and bearing on its first waves reeds, bamboos, and a thousand other spoils torn from 



its banks. Presently the river bed is completely flooded, a quarter of a mile broad, 



and from 18 to 40 feet deep, flowing on as calmly as if its current had never been 



ruflled. Like the Blue Nile, the Atbara, called also by the Arabs the Bahr-el- 



Oswad, or " Black Pi ver," flows into the Nile, and running with it from cataract 



to cataract, sends down to the lower reaches that muddy sediment by which the 



fertility of the soil is ever renewed. 



The Nubian Nile. 



Below the junction of the two Niles, north of Khartum, the river has no more 

 visible affluents during the dry season, the lower bed of the Atbara itself being 

 quite exhausted. But it probably receives hidden streams, for through evaporation, 

 lateral filtrations, and the loss sustained in irrigating the riverain plains, the stream 

 is diminished only by a seventh according to Lombardini, and by a fifth according 

 to Gothberg, in the entire section of 1,620 miles between Khartum and Cairo. In 

 the great bend that it describes in its course through Nubia it is diminished very 

 slowly ; but to the eyes of the traveller its volume does not appear to be modified 

 during this long course over a considerable portion of the earth's circumference. 

 As the Nile discharges a quantity of water equal to four times that of the Loire, 

 or seven times that of the Seine, merchant vessels might penetrate through this 

 highway to the centre of the continent, were it not obstructed at intervals by 

 numerous rocky barriers. The Nubian Nile is thus divided by six natural barriers 



