8 NOETH-EAST AFRICA. 



waters across the continent. Some old maps represent the latter as rising in the 

 same lake as the eastern Nile, whereas its main source lies, not in the centre of 

 Africa, but at Mount Loma, on the slope of the Rokelle Mountains, in the vicinity of 

 the west coast. A space of at least 2,700 miles thus intervenes between the farthest 

 headstreams of both rivers, while the nearest affluents are still separated by a dis- 

 tance of some 720 miles. The Niger in fact belongs to a region wholly different 

 from that of the Nile in the form and disposition of its plateaux. On the other 

 side of the hills where it takes its rise, the Congo, Rio Grande, Gambia, and several 

 other streams flow to independent estuaries on the west coast, while farther north 

 the Senegal, rising on the same slope as the Niger, sweeps round the hills, forcing 

 its way to the Atlantic through a series of rocky gorges and rapids. 



North of the Senegal no large river reaches the coast, and for a space of 4,800 

 miles from the bar of Saint Louis to the Nile delta nothing is met except a few 

 wadies or small streams, such as the Draa, in the south of Morocco, the Moluya, 

 Shelif, Mejerda, flowing to the Mediterranean. The Congo alone probably discharges 

 as much water as all the other African rivers together. Next to it rank the Niger 

 and Zambezi, the Nile in this respect taking only the fourth place. 



Of the inland basins either constantly or intermittently closed, the most impor- 

 tant are Lakes Tsad in the north, and Makarakara-Ngami in the south, both lying at 

 nearly equal distance from the middle Congo, and thus presenting a symmetrical 

 disposition on either side of the equator. Tsad, much the largest of the two, is 

 also situated in the northern or largest section of the continent, the extent of both 

 thus corresponding with that of the surrounding regions draining to the oceans. 

 But here all further analogy ceases, at least if it be true that Tsad has always been 

 a closed basin ; for the Ngami reservoirs certainly communicated at some former 

 geological epoch with the Limpopo and Zambezi. 



Besides these central depressions, each section of the continent has its deserts, 

 strewn with secondary basins and oases, whose waters lose themselves in the sur- 

 rounding sands. Altogether the area of inland drainage is estimated by Chavanne 

 at nearly 3,000,000 square miles, of which 560,000, or less than a fifth, lie south of 

 the equator.* Amongst the northern tracts without any outflow there are some 

 depressions which at present lie below sea-level. These are probably the remains 

 of straits and inlets formerly belonging to the Mediterranean and Red Sea. The 

 largest are those which seem to form a continuation of the Tunisian Gulf of Cabes 

 (Syrtis Minor), south of Algeria, which formerly received the discharge of the now 

 dried up Igharghar, a river 780 miles long, and consequently longer than the 



* Closed hydrographie basins of the African continent : — 



North Africa. 



Sq. Miles. 



Basin of the Tsad, including the Fedé 730,000 



„ „ Igharghar 330,000 



Other basins and waterless spaces 1,345,000 



SotiTH Africa. 



Basin of Lake Ngami ......... 314,000 



Other basins and waterless spaces. ...... 257.000 



