CENTRAL AFRICAN RIVERS. 193 



gentleman to whom this letter is addressed. Yet having come to nearly the 

 same conclusions about three years afterwards, and by a different method, the 

 reasons which guided my tortoise pace may, though stated in my own way, 

 be accepted as a small contribution to the inferences deduced by you (Sir 

 Roderick Murchison) from the study of the map of Mr. Barnes. 



" In passing northwards to Angola, the presence of large Cape heaths, 

 rhododendrons, Alpine roses, and more especially the sudden descent into the 

 valley of the Quango, near Cassange, led me to believe we had been travelling 

 on an elevated plateau. I had hopes then of finding an aneroid at Loanda ; 

 but having been disappointed in this, from my friend Colonel Steel having gone 

 to the Crimea, I had to resort, on my return, to observations of the temperature 

 of boiling water as a means of measuring elevations. 



" The highest point in the district of Pungo Andongo is given to show 

 that it is lower than the ridge, which I believe is cut through by the valley of 

 Cassange, in which the Quango now flows. And the top of the ascent of Tala 

 Mungongo — which, to the eye, looks much higher than the eastern ascent, if 

 we may depend on the point of ebullition as an approximation — is in reality 

 much lower ; indeed not more elevated than Lake Ngami, which is clearly in 

 a hollow. In coming along this elevated land towards the Quango, we were 

 unconsciously near the crest of a large oblong mound, or ridge, which pro- 

 bably extends through 20° of latitude, and gives rise to a remarkable number 

 of rivers : thus, the Quango on the north ; the Coanza on the west ; the 

 Langebongo, which the latest information identifies with the Loeti, and the 

 numerous streams which unite and form the Chobe, on its south-east ; all 

 the feeders of the Kasai and that river itself on the east ; and probably also 

 the Embara or river of Libebe on the south. Yet this elevation is by no 

 means mountainous. The general direction of all these rivers, except the 

 Coanza and Quango, being towards the centre of the continent, with a little 

 northing or southing in addition, according as they belong to the western or 

 eastern main drains of the country, clearly implies the hollow or basin form 

 of that portion of intertropical Africa. The country about Lake Dilolo seems 

 to form a partition in the basin ; hence the contrary direction of its drainage. 



"Viewing the basin from this (Linyanti) northward, we behold an 

 immense flat, intersected by rivers, in almost every direction, and these 

 are not the South African mud, sand, or stone rivers either, but deep 

 never-failing streams, fit to form invaluable bulwarks against enemies who can 

 neither swim nor manage canoes. They have also numerous departing and 

 re-entering branches, with lagoons and marshes adjacent, so that it is scarcely 

 possible to travel along their banks without the assistance of canoes. We 

 brought two asses as a present from certain merchants in Loanda to Sekeletu, 

 and as this animal is not injured by the bite of the tsetse, they came as frisky 

 as kids through all the flowing rivers of Loanda ; but when we began to descend 

 A 1 



