THE CAPE SYSTEM 157 



near Triangle, in the Hex Kiver Valley, and the top of 

 the hill east of the north entrance to Seven Weeks' 

 Poort. The last-named spot is one of the finest points 

 of vantage in the Colony for the purpose of seeing the 

 structure of a wide area. The folds into which the 

 rocks have been thrown north of the Zwartebergen are 

 distinctly seen, the outcrop of the four groups of sand-^ 

 stone in the Bokkeveld series make independent escarp- 

 ments or ledges on large ridges, and where repeated by 

 folding the structure is seen clearly. The gradual dying 

 out of the folds northwards in the Karroo is displayed 

 as if the country were a geological model, and the out- 

 crops of each formation are at once recognised. The 

 sandstones and quartzites of the Bokkeveld and Witte- 

 berg series stand up prominently between the shale 

 bands that have determined the positions of the minor 

 valleys, the soft, easily eroded shales having offered an 

 easier path for the rivers than the more resistant sand- 

 stones. The view is limited on the north by the great 

 dolerite-crowned escarpment of the Nieuweveld, seventy 

 miles distant. 



South of the Langebergen the structure of the country 

 is not at all obvious until it has been made out in detail, 

 for the Bokkeveld beds have been cut to a level with 

 the outliers of the Uitenhage series ; and although this 

 plain has since been dissected by rivers, the Bokkeveld 

 and Witteberg slates, on account of their uniform char- 

 acter, have had little effect in determining the positions 

 of the valleys, so that the longitudinal valleys so con- 

 spicuous north of the mountains are not nearly so well 

 developed to the south. 



