The high altitude region under consideration is that above 2300 metres (7500 feet) in Southern Africa ; the only extensive area, apart from isolated peaks, where such high altitudes occur, is where the basalt rock cap resulting from the vast and homogeneous lava flows of the Drakensberg Beds in the Stormberg series remains relatively intact . This includes the whole of the mountain region of the newly independent country of Lesotho and the contiguous areas of the Orange Free State, Natal and the Cape Province of the Republic of South Africa. These share the same complex of mountains, the Drakensberg, or Qathlamba, and the other ranges which spread out from Mont aux Sources .
The districts concerned are those of Harrismith, Bergville, Estcourt, Impendhle, Underberg, Mount Currie, Matatiele, Mount Fletcher, Maclear, Elliott, Barkly East, Lady Grey and Herschel ; the last five, Maclear to Herschel, have much of their area on a basaltic rock base but in the other districts, only small portions fall within the altitudinal limits, these being those parts against the slopes of the escarpment edge of the Drakensberg . The main rivers to which each of these give rise are the Wilge, which joins the Vaal above the Barrage, and rises in the Witzieshoek area of Harrismith district ; the Tugela, formed from streams descending from the Drakensberg in the Bergville and Estcourt districts ; the Orange (or Senqu, within Lesotho), rising entirely within Lesotho and covering a hundred and fifty miles or more of its course there