Geological History of the Goicritz Biver System. 383 



Throughout the country south of the Zwartebergen, and to a 

 much smaller extent north of that range, there are scattered the 

 remains of a former widespread plain covered with gravels and 

 alluvial deposits that w^ere formed when the general level of that 

 portion of the country was probably some 800 feet to 1,000 feet 

 lower than at present. These isolated patches of river-borne 

 detritus are now often found to be cemented by iron compounds 

 and silica into ferruginous and silicious rocks. Descriptions of 

 these rocks have been published in the Eeports of the Geological 

 Commission, but a full consideration of them as a whole cannot 

 be undertaken until much more is known of their relative heights 

 above the present valley bottoms. We can only conclude that they 

 record a past stage of the development of the river systems, during 

 which the rivers had, in many parts of their courses, approached 

 the limit of downw^ard erosion, and as a consequence were levelling 

 the country near them more rapidly than was possible while they 

 were chiefly engaged in lowering their beds. The surfaces thus 

 produced were gently undulating plains cut out of the softer rocks, 

 the Uitenhage, Bokkeveld, and Witteberg Series, of the country 

 between the mountains composed of the Table Mountain Series. 

 The terraces cut in the latter are frequently seen south of the 

 Langebergen, and are less well developed north of that range. 

 Had this period of low level and great lateral erosion of the rivers 

 continued to the present day, probably the most conspicuous 

 difference in the resulting surface would have been a greater 

 degradation of the mountain ranges by the extension of the ter- 

 races than has actually been the case. But after these terraces 

 had been formed, the country was elevated relatively to the ocean, 

 and the downw^ard cutting powers of the rivers therefore restored, 

 with the result that the rivers have cut deeply into the old pene- 

 plain, and the latter is only represented by the flat-topped hills 

 capped with the surface quartzites and associated rocks, which are 

 so conspicuous both to the south and north of the Langebergen. 



The great bends of the Gouritz Eiver below Herbertsdale, and 

 between the Pogha Hills and Eoode Berg, with the remains of the 

 old peneplain still preserved as steep-sided hills some 600 feet to 

 800 feet high, enclosed by the bends, are an inheritance from this 

 period of lateral erosion. While a river is actively cutting down its 

 bed it does not take a circuitous route to its mouth ; but rivers, 

 whose fall is slight, meander considerably in the plains they 

 traverse. The meanderings of the Gouritz, which are now so 

 deeply sunk below the general surface of the country in their 

 neighbourhood, were doubtless formed while the river was flowing 



