THE CAPE SYSTEM 161 



served in quartzite than in the micaceous and sandy 

 shales, although they are more abundant in the latter. 



The Witteberg beds have a maximum thickness of 

 about 2,500 feet. They form several important ranges 

 of mountains on the southern border of the Karroo, and 

 their name is taken from the Wittebergen, south of 

 Matjes Foritein. In the west and south of the Colony 

 the mountains composed of the Witteberg beds are re- 

 markably bare and barren-looking (see Plate VIII.). 

 They are less well supplied with rain than the Table 

 Mountain sandstone ranges, for the latter are generally 

 higher and therefore receive a heavier rainfall. The 

 high percentage of quartz sand in the Witteberg beds 

 causes the soils derived from them to be poor and thin. 

 The formation is first met with in the west of the 

 Colony, north of Eland's Vlei (Calvinia and Clan- 

 william), where the long line of hills called the Zwart 

 Ruggens commences. The northern boundary is a 

 denuded one, and, as is the case with the Bokkeveld 

 boundary a little farther to the north, is of great anti- 

 quity, being chiefly older than the Dwyka series. 

 Following the Witteberg beds southwards they become 

 thicker owing to the coming in of higher and higher 

 beds below the Dwyka. Some outliers, somewhat table- 

 shaped mountains, are found at Bidouw, Gerustheid, 

 and in the angle between the Bosch and Doom Rivers 

 in the north-east of Clanwilliam and south-west of 

 Calvinia. The Zwart Ruggens are a long dip slope of 

 the quartzites on the east of the Cederberg and Cold 

 Bokkeveld anticlines. When seen from the Karroo the 

 Zwart Ruggens appear to .consist entirely of whitish 



