Notes on the Congo River. 155 
(Chibungo), and other unvisited waters, its area of 
drainage will nearly equal that of the Nile. 
The four arteries all arise in inner regions of 
the secondary age, subtended east and west by 
ghats, or containing mountains mostly of palaeozoic 
or primary formation, the upheaval of earth¬ 
quakes and volcanoes. These rims must present 
four distinct water-sheds. The sea-ward slopes 
discharge their superabundance direct to the ocean 
often in broad estuaries like the Gambia and the 
Gaboon, still only surface drains; whilst the 
counterslopes pour inland, forming a network of 
flooded plains, perennial swamps, streams, and 
lakes. The latter, when evaporation will not 
balance the supply to a “ sink,” “ escape from 
the basin of the central plateau-lands, and enter 
the ocean through deep lateral gorges, formed 
at some ancient period of elevation and disturbance, 
when the containing chains were subject to trans¬ 
verse fractures.” All four head in the region of 
tropical rains, the home of the negro proper, ex¬ 
tending 35 0 along the major axis of the continent, 
between Lake Chad (north latitude 14 0 to 15°), 
and the Noka a Batletle or Hottentot Lake, 
known to the moderns as Ngami (south latitude 
20 0 to 21 0 ). Consequently all are provided with 
lacustrine reservoirs of greater or smaller extent, 
and are subject to periodical inundations, varying 
in season, according as the sun is north or south 
