South Africa is divided into an interior plateau and the more varied country between it and the sea by an escarpment. This great escarpment is very well defined southwards from the Pietersburg district, where it is known as the Drakensberg, and is made of the Black Reef quartzites as far south as the headwaters of the Komati River; from there southwards it is made of Karroo rocks lying on granite and pre-Transvaal sediments. Higher and higher beds of the Karroo system come in successively to the south and the ancient rocks become hidden under the Karroo beds, until in the Quathlamba or Drakensberg of Natal the highest known beds of the Karroo system form the summit of the escarpment, which is here the highest land in South Africa. Trending at first south-south-west and then south-west from the Tugela basin, the escarpment is made of the highest major subdivision of the Karroo system (Stormberg series) as far as the Stormberg region, where its course turns nearer west. and the upper Karroo rocks disappear from its summit in the Sneeuwberg, Nieuwveld, Komsberg, and Roggeveld. In the Roggeveld region a terrace comes in between the Karroo beds forming the upper part of the escarpment and the Bokkeveld escarpment of Van Rhyns Dorp, a cliff of Table Mountain sandstone resting on Nama beds and facing the coastal plain. The terrace wedges out between Stinkfontein Poort and Langeberg, beyond which the Karroo beds are no longer found at the edge of the escarpment, now made of gneiss alone, the Table Mountain sandstone and Nama beds having successively disappeared from it owing to pre-Karroo denudation and faulting respectively. Gneiss and its included schists form the whole of the escarpment south-east and west of Kamiesberg and as far north as the Buffels River valley, where the base of the Nama system, now lying flat, appears as a thin layer of quartzite at its edge. From Klipfontein northwards to the Orange River the escarpment and country immediately east of it are deeply cut into by stream beds with steep slope to the sea, but in the South-West Protectorate it again becomes a well-defined feature, at least in the southern part of the territory. The relation of the escarpment to the river systems is definite and important; from Carolina round by south, west, and north to the place where the Orange River traverses it by a gorge, the escarpment is almost coincident with the watershed between the Orange River and its tributaries, draining the interior plateau on the one hand, and the shorter streams which flow directly to the sea on the other. North of Carolina the escarpment is not an important watershed, the Limpopo traverses it by a low-worn valley, very different from that of the Orange, and the drainage of the central Transvaal passes through it by the gorge of the Olifants River. The Orange River basin has been diminished by captures effected by the Komati and Buffalo Rivers, and in the drier region of Namaqualand similar events are in progress; the Buffels and Green Rivers have taken the entire drainage of Kamiesberg from the Orange catchment. The escarpment is for the most part formed, or capped, by flat or gently inclined hard rocks, either sediments, intrusive sheets, or lavas, and to these rocks it owes its definiteness, for they have checked the headward development of the streams coursing down the more rapid slope to the sea, and their disposition and joint-systems tend to maintain vertical cliffs at the top of the slope. Whether we look at the escarpment in the Transvaal Drakensberg, the Natal Berg, Stormberg, Nieuwveld, Bokkeveld, or the hills south of Anenous, the cliffs facing the ocean are the striking feature in the view. The persistence of this escarpment along more than a thousand miles is in conformity with the general steep grade of the rivers draining the country, for both point to geologically recent elevation. The top of the escarpment is, as a whole, the highest belt in the country, and it is only in the Cape ranges that we find small areas exceeding in height the top of the escarpment inland of them. The interior plateau and the country outside it can be divided up into several regions more or less sharply by characters dependent on past geological events and climate. The number of these regions can, of course, be increased by narrowing the range of characters considered to be distinctive of each, and the degree to which the process is carried is determined by the purpose in view. The regions chosen for this sketch are as follows: The interior plateau (1) The High Veld. (4) The Basuto Highland. (5) The Limpopo Highland. (6) The Bushveld. (7) The Kalahari and Bushmanland. (8) The Kaap Plateau. (9) The Namaqualand Highland. (10) The Low Country (including much country below the escarpment). The country below the escarpment (11) The Great Karroo. (12) The South-Eastern Region. (14) The Coast Belt. The interior plateau is drained by the two largest rivers in the country, the Orange and the Limpopo, and by the Olifants River. The Limpopo has the more open and gently graded valley of the two; it has reached a maturer stage in river development than the Orange perhaps owing to its being throughout its course in a region of higher rainfall, and this circumstance may have persisted during the past existence of the two rivers. The Orange River flows through a region of very low rainfall for some 600 miles above its mouth; from the Prieska district to the sea it only occasionally receives water from tributaries: in fact, the loss of water by evaporation must exceed the influx below the confluence of the Orange and Vaal Rivers. Beyond the Kenhardt district (Augrabies Falls) the Orange runs through a gorge or very steeply sided valley to within 50 miles of the sea. A discussion of the relative importance of uplift and possible change of climate in past time in determining the characters of the Orange and Limpopo drainage-basins would lead too far for the present occasion, but it should be borne in mind that a desert climate tends to produce flat surfaces over wide areas both by erosion and the filling-up of valleys. and also depressions or pans wanting an outlet for running water; while a climate wet enough to maintain river channels leading eventually to the sea or to an inland depression of tectonic origin (i.e. due to movements of the earth's crust) produces continuous slopes which tend to become plains advancing inland as long as the country remains stationary relatively to sea-level and is not tilted. If the country rises as a whole, the downward cutting of the rivers is increased, the renewed activity starting from the coast and proceeding upstream; if the country is tilted, the effects vary according to the situation of each tract or stream relatively to the tilt. There is a contrast between those parts of the interior plateau which are still covered by Karroo rocks and those from which the Karroo formation has been denuded; plains and flat-topped and terraced hills are characteristic of the former, while plains and ridges, often of the "inselberg" type, are found in the latter. The Karroo beds extended over the whole of the plateau at no very distant date, and the hills made of pre-Karroo rocks we see to-day, such as the Magallesberg, Witwatersrand, and the Langeberg of Bechuanaland, owe their shape in the main to pre-Karroo denudation, and their old forms have been revealed through the removal of the Karroo rocks under which they were formerly buried. The plateau reaches its greatest elevation in the Basutoland mountains, where it is so dissected by the headwaters of the Orange River that the plateau character is concealed. The structure of Basutoland, however, unites it with the rest of the plateau. An important point concerning past clin:atic conditions may be touched upon here the extent to which South Africa was affected by the fall in temperature which brought about the lowering of the snow line in Europe, America, Central Africa, Asia, Australia, and New Zealand. South Africa can hardly have escaped the influence of these worldwide conditions, but up to the present time no indisputable sign of the former existence of glaciers in the country since the period of the Karroo (Dwyka) ice-sheets has been found. The few supposed moraines and glaciated surfaces yet reported have not met with acceptance, and the characters of the high-lying valleys in the Basuto mountains and the Cape ranges point to stream and not glacial erosion as having had at least the chief share in their production. Inselberge are hills which rise abruptly from a plain, such as the kopjes of metamorphosed Pretoria beds in M'Pathlele's Location and the Korannabergen of Bechuanaland. (1) The High Veld covers the south-eastern Transvaal and much of the Orange Free State; the surface is directly underlain by the Karroo beds lying flat or by dolerite sheets intrusive in them. It is characteristically a grass veld, and the soil is on the whole deeper than that on the older rocks to the west. The rivers have cut rather deep valleys with gently inclined sides in the country near the escarpment, but undulating and flat surfaces predominate towards the east. The rainfall is moderately high (20 to 35 in.), and the rivers usually have water in them. A noteworthy contrast between the High Veld and the Middle Veld is due to the lack of superficial deposits of limestone in the former and their abundance in the latter, whence they continue over the Kaap Plateau and the Great Karroo. This difference does not indicate poverty in lime of the rocks in the east, but it is intimately connected with the westerly decrease in rainfall. In a dry climate much of the carbonate of lime dissolved by percolating rain-water is left in the soil by the evaporation of the solvent, but in a wetter climate most of it is carried to the streams in weak solution. The High Veld, in common with the country to the west, has an abundance of pans, flat surfaces below the level of the immediately surrounding country without a valley leading from them. The pans of the north-eastern part of the High Veld, of which Lake Chrissie is a very fine example, are remarkably large and deep, and their origin is a most interesting problem. The wind is an efficient agent in the formation of pans in a dry region, and pans are characteristic of dry countries throughout the world, especially where the country happens to be made of horizontal beds; but the eastern Transvaal has a good rainfall, and it is difficult to understand how the rainfall there was ever less than in the western Transvaal and the country still farther west. The Lake Chrissie group of pans has reached a further stage of development than those of the rest of the plateau, except perhaps a few of the pans in the Kalahari. The existence of the pans is itself evidence of a former climate drier than the present, but there is as yet no corroborative evidence known, either in the existence of patches of superficial limestone or remains of inselberge. Possibly there may be some feature in the vegetation which throws light on the question. (2) The Middle Veld, a term borrowed from its local use for the country between the High Veld and the Bushveld and Bechuanaland, includes the districts of Potchefstroom, Bloemhof, Wolmaransstad, Lichtenburg, and Taungs, and parts of Pretoria, Middelburg, Heidelberg, Rustenburg, Marico, Vredefort, and Barkly West. It is made up of pre-Karroo rocks with only small outlying areas of Karroo beds lying on them, and in it are the extensive high- and low-level gravels of the Vaal and Harts Rivers, which are the seat of the river diggings. Volcanic rocks of the Ventersdorp system occupy wide flat areas in the south-west between Klerksdorp, Ventersdorp, Vryburg, and Barkly West, with the Witwatersrand beds and older granites and schists appearing from below them in the Transvaal and Orange Free State portion of the region. The Pretoria series forms important ranges, such as the Magaliesberg and Gats Rand, and the dolomite below that series underlies the surface over large parts of Pretoria, Rustenburg, Marico, and Lichtenburg. The dolomite is the chief water-bearing rock in the Union, but the rock itself is impervious, and it is the widened joints due to solution by ground-water that furnish storage room for it and strongly influence the behaviour of underground water in the areas made of the rock, besides accounting for the apparently erratic disappearance of streams and the occurrence of strong springs. The rivers are less constantly supplied with water in this region than in the High Veld. On account of the varied character of the rocks, such as the quartzites of the Witwatersrand system, the Black Reef and Pretoria series, the shales of the Pretoria series, the dolomite, the Ventersdorp volcanic rocks, and the old granites and schists, the region has a great range of soils, and the vegetation may be expected to show much diversity; as a whole the region is grass veld and small bush. (3) The Upper Karroo includes the south-west of the Orange Free State, the valley of the Vaal River south of Barkly West, and that part of the Cape Province between the great escarpment on the south, and Bushmanland and the Orange River on the north. Most of the country is made of the nearly horizontal sandstones and shales of the Karroo formation penetrated by sheets and dykes of dolerite, and the drier north-western part of the region has much tufaceous limestone in or below the soil. In Prieska and Kenhardt the rocks of the Transvaal and older systems have to a large extent been stripped of the Karroo beds, and the sediments form low ranges of hills, the Doornbergen and the long quartzite range on the boundary of the two districts, while the granite and gneiss give rise to gently undulating ground with occasional kopjes often appearing to be made up of huge boulders. Where the Karroo beds above the Dwyka series form the country, the hills are markedly terraced by the resistant sandstones and dolerite sheets, one or other of which often makes kranzes on the slopes. The dolerite sheets may be scores or even a few hundred feet thick, and where these happen to form the surface at a moderate height above the river channels cut in or through them, they make exceedingly rough ground studded over with low kopjes between which large and small boulders of dolerite are strewn. Dolerite sheets in the wide flats of Hopetown, Prieska, Britstown, De Aar, and Carnarvon make no prominent features, and they are deeply decomposed and usually accompanied by limestone derived from their decomposition. The position as regards ground-water is the condition governing the behaviour of the dolerite where the rock is exposed for long periods to the action of water it becomes decomposed to irregular depths along joints, and where this partly decomposed rock is subjected to active denudation the soft, weathered portions are removed faster than the hard, fresh parts; the sheets capping hills high above the general level of the neighbourhood maintain a fairly even surface and are little decomposed. The dykes, which are numerous, give rise to linear groups of kopjes or ridges, such as are conspicuous features in the landscape between Beaufort West and De Aar. The inclined dykes or sheets are more apt to produce these features than the vertical dykes. The larger groups of hills between the flat country of the north-west and the edge of the escarpment are not linear ranges, but irregular remnants of plateaux. The rivers have low grades after leaving the hilly country, and wide stretches in the lower part of the valleys are covered with water in flood times. These flats are in the shales and tillite at the base of the Karroo formation, rocks which are easily removed by the action of the wind and rain, while farther down, the rivers traverse the hard archaean rocks which form the floor of the Karroo beds north of latitude 3140, check the downward cutting of the river-beds, and allow the rain and wind to cut great flats on the more easily denuded Karroo formation to a level very little above that of the outcrop of the archaean border. The extensive vloers of Calvinia and Carnarvon, which are found near the edge of the Karroo outcrop, are such flat surfaces thinly covered with the finest silt dropped from flood-water, and, in some instances at least, the silt is impregnated with soluble salts. The striking absence of vegetation from the vloers is no doubt chiefly due to the abundance of the salts, but in part it may be due to difficulty seeds have in establishing themselves on the almost continuous film of hard, dry mud. (4) The Basuto Highlands are distinguished from the High Veld and Upper Karroo by their mountainous character. The mountains consist of those parts of the highest series of the Karroo formation, the cave sandstone and the volcanic beds, which have not been removed by denudation. Basutoland is the highest lying of the regions, for narrow strips along the Caledon and Orange Rivers alone lie below 5000 ft., and the mountains attain heights exceeding 10,000 ft. The whole region is carved out of the uppermost sub-division of the Karroo system, the Stormberg series, of which the pale-coloured cave sandstone and the overlying dark basaltic lavas form the mountain masses. These two groups of beds form the Springbok Flats of the Transvaal, where the rocks are rarely seen cropping out from below the general cover of sand. The great contrast between the surface features of these two areas made of the same rocks is primarily due to their different altitudes above the outlets of the rivers draining them; in Basutoland the rivers are engaged actively in cutting down their beds, which for some 300 miles are made of Karroo rocks only, while the Nyl and Olifants Rivers, which drain the Springblok Falts, meet the hard belts of the Limpopo Highlands within a short distance of the flats, where the rocks have disintegrated faster than the streams can carry away the sand, owing to the great resistance of the hard rocks to the corrosion of the rivers. (5) The Limpopo Highlands comprise the rugged country of the northern Drakensberg traversed by the Steelpoort and Olifants Rivers, the Waterberg and Pietersburg plateaux, and the Zoutpansberg. The greyish quartzites of the Black Reef series in the south-east give rise to rough hills with scanty and sandy soil, while the granites of the Pietersburg plateau with their included schists form more undulating and bush-covered country. The contrast between the forest belt on Zoutpansberg and the Woodbush on |