382 Transactions of the South African Philosophical Society. 



Buffel's Eiver. The diversion of the Buffel's Eiver was brought 

 about by the more rapid erosion of the valley of the Gamka, which 

 enabled the tributary of the latter from the west to cut back the divide 

 between the Gamka and Buffel's Elvers to such an extent that the 

 latter river deserted its old course and flowed into the Gamka. The 

 level of the Garcia Pass is about 1,000 feet above the present level of 

 the Butfel's Eiver at the point where it changes its direction, and the 

 diversion must have taken place a very long time ago. Examples of 

 change in direction of rivers owing to the encroachment of a lateral 

 stream, or in the language of the American geographers, the behead- 

 ing of rivers, are to be found elsewhere in the Colony. One very 

 clear case is that of the Drie Hoek's Eiver in Clanw^illiam which 

 flows eastward from the Cederberg anticline, and which formerly ran 

 across the escarpment of the Bokkeveld and Witteberg beds through 

 Nieuwe Gift into the Kruis Eiver, but a north branch of the Matjes 

 Eiver, working its way along the soft Bokkeveld shales, has captured 

 the Drie Hoek's Eiver, and the former eastward course of the latter is 

 now indicated by a deep depression in the escarpment, a wind gap of 

 the Americans. In this case the cause of the diversion is clear, the 

 soft shales of the Bokkeveld Series yielded easily to the encroaching 

 stream so that the Drie Hoek's Eiver was forced to flow down that 

 stream instead of maintaining its former valley across the harder 

 beds of the upper part of the Bokkeveld Series. In the case of the 

 Buffel's Eiver the diversion is so old that we cannot know exactly 

 what the determining factors were. The Langebergen evidently 

 made it sufficiently difficult for the river to cut down its valley across 

 the range, but whether the lateral affluent of the Gamka at the time 

 of the diversion ran over the Uitenhage Series, or whether the river 

 bottom had reached the underlying Bokkeveld Beds, is now 

 impossible to find out. 



From an inspection of the maps it is probable that the Traka 

 has had a history somewhat similar to that of the Buffel's Eiver, 

 and has been captured by the Oliphant's Eiver. "Whether the 

 Meiring's Poort Eiver is another victim of the Oliphant's Eiver is 

 as yet uncertain ; the Wagonpad's Nek in the Kamnassie Eange, 

 and a favourably situated depression in the Outiniqua's, point to 

 that being the case, and the future examination of the country will 

 decide the matter. 



It appears not improbable that the Gouritz Eiver system has 

 developed by the encroachment of the Dwyka and Gamka Elvers 

 and their affluents, which have captured the Buffel's, Meiring's Poort) 

 and Traka Elvers, once streams with independent valleys from the 

 Karroo to the ocean. 



