PHYSICAL GEOCfRAPHY OF THE CAPE COLO>TY. 207 



which at last extended itself northwards about as far as the line of 

 the Zwartebergen, Wittebergen, and the other ranges included in 

 that chain. The country north of this line still remained above 

 water. In the basin so formed the Table-Mountain Sandstone, the 

 Bokkeveldt Beds, and the Zwarteberg Quartzites were deposited. 

 Whether these formations were laid down without interruption 

 during a long period of unbroken subsidence, or whether during the 

 time of their formation there were intervals of upheaval and 

 denudation, we cannot say until the geology of the country they 

 now occupy has been worked out in detail. The former supposition 

 has this in its favour. These rock-groups now form a number of 

 parallel ranges, which, in spite of their present moderate elevation, 

 have all the characteristic structure of a true mountain-chain, and 

 it is well known that the production of a mountain -chain has 

 generally been preceded by continuous sedimentation during a long 

 period. 



Earth-movements set in after the deposition of the Zwarteberg 

 Quartzites ; the rocks were folded and largely denuded. The proof 

 of this lies in the fact, noticed by Bain, that the Dwyka Conglom- 

 erate, the formation that follows next in order, rests sometimes on 

 the Quartzites and sometimes on Bokkeveldt Beds, and contains 

 boulders of the Quartzite. 



The continent now presented a great mountain-chain running 

 across it from east to west on the south, and a broad tract formed 

 of the Basement Eocks spreading away to the north. 



Afterwards the land again began to go down. The mountains 

 very likely sank, but not enough to lay them beneath water. But 

 the tract to the north became submerged, and a great basin was 

 eventually established, the southern shore of which was formed by 

 a line of quartzite mountains and the northern shore of Basement 

 Rocks. But the submergence was gradual, beginning on the south 

 and pushing its way step by step northwards. There was thus at 

 first only a narrow belt of shallow water fringing the quartzite 

 mountains, and into this blocks and boulders from the quartzite on 

 the one side, and from the Basement Eocks on the other side were 

 rolled down, and piled up in shingly heaps which are now the 

 Dwyka Conglomerate. The fans of gravel now forming at the 

 mouths of the Himalayan valleys furnish instances of a similar 

 process ; if these were discharged into the sea instead of being 

 thrown down on land, they would be spread out into a sheet of 

 conglomerate and breccia. As the water worked its way north- 

 wards, similar deposits would form along the receding coast-line, 

 and the whole bottom of the basin would become covered with a 

 sheet of conglomerate. But as soon as any portion of the basin 

 became deep enough, it would become the receptacle of finer sedi- 

 ment, and so a great thickness of shale, sandstone, and limestone, 

 the present Ecca Beds, accumulated above the conglomerate. 



The formation of the Ecca Beds was brought to a close by another 

 series of powerful earth-movements. These acted with greatest 

 energy on the south, along the old lines of disturbance : and accord- 



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