354 Transactions of the Boyal Society of South Africa. 
gentle features which vary its raonotonous aspect are caused by beds of 
resistant chert. The post-Karroo origin of the plateau is proved by the 
fact that both at Boetsap and near Mark's Drift the Dwyka shales have 
been cut to a flat equally with the Campbell Eand limestones. 
Gravels are still found in situ on this surface, namely, between 
Kuruman and Vryburg, at an altitude of 4,750 feet, the pebbles having 
obviously been transported some distance, and along the edge of the Kaap 
at 4,000 feet, near its south-eastern extremity, where water-worn 
pebbles of the jaspers of the Griqua Town Hills predominate. 
The occurrence of these durable brown jasper pebbles is of immense 
value in determining the existence of former deposits of gravels, for the 
rocks from which they were derived are only known in the Griqua Town 
and Doornberg Hills, and inclusions of this material are not found in the 
Dwyka tillite in the area under consideration. 
These jasper gravels are found south of the Orange Eiver as far away 
even as Hopetown — a distance of 70 miles from their nearest possible 
source, and at an altitude of 8,600 feet. Small fragments are not un- 
common over Hopstown and Britstown up to altitudes of nearly 4,000 feet, 
and, though some can be accounted for as having been carried by the 
aborigines for the purpose of making implements, they are so numerous 
that there can hardly be any doubt that they are the relics of gravels 
deposited by streams arising in the north and north-west, for it is note- 
worthy that the pebbles become gradually smaller in size to the south-east. 
Further south in Carnarvon, Victoria West, Eichmond, and Philipstown 
lies a belt of rugged country, composed of terraced dolerite-capped hills, 
in which isolated peaks attain an altitude of over 5,000 feet, and in some 
instances of over 6,000, and which is situated some distance to the north 
of the main watershed of the Colony. In this important mountainous 
region, owing to subsequent erosion, no traces of the peneplain remain. 
The course of the rivers over the original surface of this peneplain, 
which can be named the Kaap Peneplain, is naturally impossible to 
determine with any pretensions to accuracy. In the north the emergence 
through the cover of Karroo rocks of the crests of the once-buried ridges 
must have determined the water partings in that quarter. In the north, 
therefore, the old drainage was re-established, but in the south, where the 
ancient rocks were still deeply buried, new drainage lines were set up 
and attained some measure of permanency. The evidence obtainable 
seems to show that the position of the Orange Eiver lay many miles to 
the south of its present course in Hopetown. Below Prieska its direction 
may have followed more or less that of its present course, and it is note- 
worthy that the evidence for the existence of the peneplain in this quarter 
is found in the remarkably flat-topped ridges of the Doornbergen, the 
Kheis Hills, Ezel Eand, and Langebergen in contrast to their jagged 
