The southern frontier is formed by the escarpments which separate the Niger basin from those of the coast rivers of Liberia.
From the valleys their rugged, deeply indented escarpments, stretching away to the horizon, have the appearance of a continuous chain of mountains.
It first flows in a valley bounded, especially towards the west, by the escarpments of a high plateau, and containing the towns of Lugh (in 3° 50' N., the centre of active trade), Bardera, 387 m.
The eastern escarpments (the Drakensberg, &c.) of the plateau intercept the rain-bearing winds from the Indian Ocean, so that over the greater part of the interior the rainfall is slight (5 to 24 in.).
Through these gorges dash magnificent cascades, others leaping the escarpments of the plateaus in waterfalls of great volume and depth.