132 Proceedings of the Royal Society 
ward. It is true that the whole of South Africa is a plateau, with 
a general elevation of about 3500 feet, and that the outer edges of 
it rise steeply from both coasts; but the eastern side is the higher 
of the two, and the law of a general slope towards the Atlantic is 
maintained on its surface. The Lake Eegion occupies the central 
part of the eastern, or higher side, of the South African plateau, 
and here the line of descent to the coast-land of the Indian Ocean 
is marked continuously from north to south; first by the south¬ 
ward continuation of the outer slope of the Abyssinian table-land, 
then near the equator by the edge on which the great mountain 
peaks of Kenia and Kilima Ndjaro rise; farther south by the 
Rubelio Mountains, up which Burton and Speke ascended to the 
plateau; and then by the N’jesa Mountains, which wall in the 
Lake Nyassa. Farther south the cataracts of the Shire river, 35 
miles in extent, show where this river tumbles over the edge of 
the plateau, and the Zambezi breaks through it at the narrows of 
Lupata. Below this steep edge the coast-land slopes in gently to 
the sea, and is diversified by wide plains or scattered hill ridges. 
The high surface of the South African plateau inland is hollowed 
out in the wide high valleys which contain its lakes and great 
rivers. The most northerly of these depressions in the Lake Region 
is that of the great lake reported by the ivory trader Piaggia, who 
approached within 60 miles of its northern shore. This lake ap¬ 
pears to lie in a high valley on the northern edge of the plateau 
of South Africa, or rather in a recess of the northern lower land, 
partly shut in by the slopes of the plateau southward, and the 
mountain range which the traveller saw rising to south-westward 
beyond the lake, is perhaps only the steep northern edge of the 
southern plateau here. 
The wide depression in which the Victoria Lake lies is shut in 
eastward by the continuation of the Abyssinian highland into the 
South African plateau. This valley appears to include the basin 
of the Bahari N’go, which is believed to he a vast salt marsh, or 
perhaps a sort of backwater of the Victoria Lake, and its slope is 
to north-westward, towards the angle of the northern lower land 
which is formed by the inner side of the Abyssinian highland run¬ 
ning north and south, and the northern edge of the plateau of 
South Africa, which has a direction from east to west. 
