Page:Africa by Élisée Reclus, Volume 4.djvu/120

86 SOUTH AND EAST AFRICA. the Limpopo. In this northern section of the Border llunge the last crest which exceeds 7',000 feet is the Mauchberg (7,300), so named from the explorer who discovered the goldfields of this region. Nevertheless the Zoutpansbergen, or " Saline Mountains," at the northern extremity of the whole system, still present an imposing aspect, thanks to the precipitous slope of their escarpments down to the valley of the Limpopo. Towards the south-west some disconnected ranges of hills and scattered heights serve to break the monotony of the upland plains, which descend with a gentle incline towards the less elevated depression of the Kalahari Desert. But these eminences produce little effect, owing to the great relative altitude of the surrounding plateau. They culminate in the Magalies- bergen, near Pretoria, capital of the South- African Republic (Transvaal). Geological Formations. Throughout the whole of Austral Africa, comprising Cape Colony, Kafirland, Natal, the Basuto, Zulu, and Dutch territories, the general geological substratum is constituted by granitic rocks, which underlie all the other formations of this region. By their incessant erosive action the running waters have everywhere exposed the lower granitic foundation and the sedimentary strata deposited on the primitive crystalline rocks. As remarked by Livingstone, the granite back- bone is concealed, but it here and there breaks through the skin. The granite is itself traversed in all directions by veins of a very pure white quartz, which are almost everywhere associated with auriferous deposits. But except in some rare districts these deposits are not sufficiently abundant to render mining operations remunerative. Throughout the whole of the coastlands the underlying granite is covered by crystallised limestones, while in the interior the granite is overlain chiefly by carboniferous series and Devonian formations with their crown of sand- stone rocks. Some geologists point to heaps of displaced and striated boulders, as clear indications of a former glacial period on the eastern slopes of the Drakenberg. Most observers also accept the view that the seaboard is at present undergoing a process of slow upheaval. From the Cape of Good Hope all the way to the coast of Natal may be seen old tracings of raised beaches still covered with banks of marine shells, oysters, and polyps. Near the south frontier of Natal these elevated banks stand nearly fourteen feet above the present level of the highest spring tides.* Rivers— The Orange. The great watercourse of Austral Africa, and one of the most considerable in the whole Continent, if not for its volimie, at least for the length of its course and the extent of its basin, is the Gariep of the Hottentots, the Groote-rivier (" Great River ") of the Boers. In the year 1770 it received from Gordon, an officer in the Dutch service, the name of Orange, more in honour of the royal • Griesbach, Qtiarterly Journal of the Geological Society, May, 1871.