256 PKOF. A. H. GKEEN ON THE GEOLOGY AND 



The fresh unaltered state of the minerals in these slices is very 

 noticeable, all the more so that my specimens were taken close 

 to the surface. The dryness of the climate and the scantiness 

 of the vegetation have probably much to do with this. 



II. Lie of the Eocks and PnrsiCAL Stetjctuke of the CouifTKT. 



In its broad outlines the geological structure of the southern end 

 of Africa is extremely simple. The strike of the beds runs roughly 

 parallel to the coast, and in the part of the country with which we 

 are now specially concerned is nearly east and west. The general 

 dip is from the coast towards the interior, so that in the district 

 now under consideration it is northerh'. 



The country falls naturally into two divisions, sharply contrasted 

 with one another in geological structure ; the one on the south is a 

 district of disturbed, the one on the north of undisturbed beds ; the 

 distinctive characters of each will be recognized by a glance at 

 Horizontal Sections nos. 1 & 2 (figs. 4 and 5, facing p. 270). 



The southern belt of folded and contorted rocks includes the 

 formations up to the top of the Ecca Beds. The southern half 

 of this belt is occupied by the formations up to and including the 

 AVitteberg quartzites (jS'o. 4 of the Table at p. 240), and its physical 

 structure is very much the same throughout. More or less inter- 

 rupted hill-ranges, with a general easterly and westerly trend, 

 separated by longitudinal valleys, and cut across by transverse 

 gorges, are the features which it everywhere presents. The separate 

 hill-ranges of this zone are numerous, and each has a name of its 

 own ; the Zwartebergen and Wittebergen may be taken as types of 

 all of them. The maximum of contortion and elevation is found 

 along a zone ininning east and west through the centre of the con- 

 torted belt. Both to the north and south of this zone the folds open 

 out, and the contortion gradually decreases in intensity. 



AVe have here all the distinctive characters of a true mountain- 

 chain, of a somewhat mild type perhaps, and worn down by denu- 

 dation to a moderate elevation. 



The northern part of the southern belt is occupied by the Dwyka 

 Conglomerate and the Ecca Beds. It varies a good deal in its physical 

 aspect : some of its chief characteristics have been already mentioned, 

 and will be described further on. 



To the north of the contorted belt lies a broad spread of country, 

 in which the Kimberley Shales, the Karoo Beds, and the Stormberg 

 Beds come on, one above the other. The rocks lie in a great saucer- 

 shaped basin ; but the saucer is so flat that the strata are every- 

 where practically horizontal. This country is bounded on the south 

 by a belt of lofty ground formed by a number of hill-ranges, with 

 a general easterly trend, of which those known as the Nieuwveldt 

 and Camdeboo Mountains may be taken as types ; but these are hills 

 of denudation, and have no right to the title of mountains in the 

 geological sense of the word, though, if wildness and ruggedness 

 may give them a claim to the name in its popular acceptation, they are 



