The water-parting.
Passing from the mountains to the great plateau they enclose, the first point to be noted is that its surface is set at two opposite "tilts," the portion north of the Witwaters Rand inclining downward to the east, the other, south of that ridge, to the west. The drainage, therefore, runs respectively east and west, and it is effected by the two great streams of the Limpopo and the Orange, with their many affluents. The general river system of the central plains is thus of the simplest; the Indian Ocean receives their northern waters, the Atlantic their southern; the remarkable factor of the arrangement being that a physical feature so insignificant as the Witwaters Rand should perform the function of water-parting for a region so gigantic.[64]
Course of Limpopo.
The Limpopo, or Crocodile river, rises as a paltry stream in the Witwaters Rand between Johannesburg and Pretoria, and flows into the Indian Ocean, 80 miles north of Delagoa Bay, covering in its course fully 1,350 miles.
Course of Orange.
The Orange has three distinct sets of headstreams from the western flank of the Drakensberg, and a total length of 1,300 miles. From the Basuto border to Ramah, on the Kimberley railway, about 220 miles, it divided the Orange Free State from Cape Colony. The Orange receives on its right bank its greatest affluent, the Vaal, which is between 500 and 600 miles in length. Commercially, both the Orange and the Vaal are as useless as their smallest tributary, being entirely unnavigable at all times of the year. Raging floods in the wet season, and mere driblets in the dry, they are at present denied to the most powerful or shallowest of river steamboats. The prospects of the Orange river as a potential waterway are in any case practically destroyed by a great bar which blocks approach to the estuary from the sea.
Military character of streams of S.A.
The streams of the South African plateau, whether river, spruit, sluit, or donga, have, in addition to their extreme variability, another marked and almost universal peculiarity. Running in deep beds, of which the banks are usually level with the surrounding country, and the sides terraced from the highest to the lowest water-mark, they constitute natural entrenchments which are generally invisible, except where rarely defined by a line of bushes, and, owing to the dead uniformity of the surrounding country, are almost impossible to reconnoitre. Nor, in 1899, were their defensive capabilities lessened by the dearth of bridges, by the dangers of the drifts, and by the absence of defined approaches to all crossing-places away from the main roads. The "drifts," or fords, especially rendered the laying out of a line of operations in South Africa a complex problem. Their depth varied with the weather of the day; they were known by many names even to local residents, and were of many types; but all alike were so liable to sudden change or even destruction, that any information concerning them, except the most recent, was practically useless.
Effect of winds on climate.
To comprehend broadly the salient physiological features of a region so enormous as South Africa, the causes of the climatic influences which affect them must be understood. These causes on are simplicity itself. The warm winds blow from the east, and the cold from the west; the former, from the warm Mozambique current, skirting the eastern seaboard, the latter, from the frigid Antarctic stream, setting from south to north, and striking the western coast about Cape St. Martin. It follows, therefore, that the climate and country become more genial and fertile the further they are removed from the desiccating influence emanating from the western seaboard. The dreariness of the solitudes between Little Namaqualand and Griqualand West, the latter slightly more smiling than the former, attests this fact. But the comparative inhospitality of the Boer States—comparative, that is, to what might be expected from their proximity to the warm Indian Ocean—demands further explanation. From the Atlantic to the eastern frontiers of these States no mountain ranges of any elevation intervene to break the progress of the dry, cold breezes; from the mouth of the Orange river to the Drakensberg the country is subject almost uninterruptedly to their influence. But it is not so with the milder winds from the east. The great screen of the Drakensberg meets and turns them from end to end of South Africa; no country west of this range profits by their moisture, whereas the regions east of it receive it to the full. Hence the almost tropical fertility of Natal and eastern Cape Colony, with their high rainfall, their luxuriance of vegetation, indigo, figs, and coffee, and the jungles of cactus and mimosa which choke their torrid kloofs. Hence, equally, the more austere veld of the central tableland, the great grass wildernesses, which are as characteristic of South Africa as the prairies and the pampas of America, and, like them, became the home and hunting-ground of a race of martial horsemen. Agriculture, The velds. following nature, divides the veld into three parts, the "High," "Bush," and "Low" Velds; but it is the first and greatest of these which stamps the central tableland with its peculiar military characteristics. Almost the whole of the Orange Free State, and the Transvaal east of the Natal railway, are High Veld, which may be taken to mean any grassland lying at an elevation of about 4,000 feet, upon which all vegetation withers in the dry season, while in spring and summer it is covered with nutritious herbage. The Low Veld lies properly between longitude 31° and the tropical eastern coast; while the Bush Veld is usually understood to mean the country lying between the Pretoria-Delagoa railway and the Limpopo river. The terms, however, are very loosely used. The Low Veld differs widely from the High Veld. Upon the former is rich—almost rank—vegetation and pasture flourishing throughout the year. But the climate is hot, moist, and unhealthy; and the Boer farmers, forced by the course of the seasons to drive their flocks from the sparkling, invigorating air of the uplands to the steamy lowlands, were wont to take the task in turn amongst themselves, as an unpleasant one to be performed as seldom as possible.