KLEIN ZWARTBERG AND WITTEBERGS 393 



A view looking southward from the same knob on the wrinkled mono- 

 clinal ridge is presented in figure 6. Here the basal member of the Witte- 

 berg sandstones is seen with northward dip forming a ridge in the farther 

 foreground. When this ridge is followed westward its determining 

 stratum is seen to bend around, so as to form a sharp turn in the ridge 

 crest. How it is then continued, or whether it is torn or cut off by a 

 local fault, I can not say. Klein Zwartberg is shown in the distance, 

 with the deep gap of Buffets river on the left; subordinate Bokkeveld 

 ridges occupy the intermediate lowland. It should be avowed that this 

 figure is composed of two sketches; the foreground was drawn looking 

 southwest; the background, looking south. The two sketches have been 

 brought together by swinging the background about 45 degrees to the 

 right of its true direction with respect to the foreground, thus giving the 

 incorrect impression that the near and far ridges are convergent, while as 

 a matter of fact they are essentially parallel. The barrenness of this 

 landscape was a surprise to me; the view here drawn included only one 

 house in the river valley. A few flocks of goats and sheep were seen on 

 the ridges, where they seemed to do well, although we saw little or no 

 grass among the peculiar plants of this arid region. The dryness of the 

 climate by which the barrenness of the Karroo is caused does not seem 

 to be due largely to the desiccation of rain-bringing winds by the 

 mountains that lie across their path, for in that case the mountains them- 

 selves ought to be fairly well watered on their windward (southern) slopes, 

 and this does not seem to be the case. The dryness is more largely deter- 

 mined by the insufficient equatorward migration of the belt of subtropical 

 rains of the South African winter season, and thus resembles the dryness 

 of Lower California, where rainfall is extremely scanty, although the 

 ocean lies directly alongside of the desert coast. The tracks of the 

 cyclonic areas, from which the rainfall of the subtropical belts is chiefly 

 derived, do not appear to run far enough toward the equator, even in the 

 winter of the southern hemisphere, to water the Karroo. On the other 

 hand, the thunderstorm rains which water the interior highland during 

 the southern summer do not occur very often so far south as the Karroo. 

 Thus the Karroo remains as a dry belt between two areas of moderate 

 rainfall, one of winter, the other of summer rains. It is important to 

 understand this matter in connection with the climate of the Dwyka 

 glacial period, which is considered in a later section. 



TABLE MOUNTAIN RANGE AND ITS FELLOWS 



We learned from Mr Sogers that the anticlinal Zwartberg is a typical 

 example of its system. In this respect the east-and-west Cape Colony 



XXXV — Bull. Geol. Soc. Am., Vol. 17, 1905 



