■50 Transactions of the South African Philosophical Society. 



withdrawn, and the occurrences of gravels on the ledge lends addi- 

 tional evidence for this view. But on studying the area further, it 

 will be seen that there are several hills in the centre of the basin 

 which come up just to the level of the ledge and no further, and 

 slowly one gets to recognise that the ledge is but the remnant of a 

 wide high-level plateau which has since been cut into by the natural 

 forces of erosion. Along the south side of the basin, and north of 

 the Kammanassie Mountain, the shelf is still very broad, running 

 out from the mountain a mile or more, and there are only deep and 

 narrow gorges cut into it. The rock out of which the shelf s are cut 

 is mostly Bokkeveld Beds. On the north of the basin, however, the 

 width of the shelf is much less, and the end of the remnants facing 

 the main river are not simple mountain slopes covered with debris, 

 but are true dip-slopes of Table Mountain Sandstone. The dip- 

 slopes are very steep, from 45° to 60°, and on some a small patch of 

 Bokkeveld slates is still adherent, and Enon Conglomerate is also to 

 some extent piled against them, but for the most part they are bare 

 rock-faces truncated at the top by the shelf and covered with gravel. 

 We have found these rock-shelfs as far west as Seven Weeks' Poort 

 on the Ladismith side ; and they can also be very well seen at 

 Meiring's Poort ; between these two points there has been so 

 vigorous an erosion that the traces of the old plateau have disap- 

 peared, yet it is abundantly evident that the plain did formerly exist 

 here. 



At Ylakte Plaats the shelfs run together and form a continuous 

 high-level plateau. It is very interesting to notice here the remnants 

 of another plateau only a hundred feet above the present flood-level, 

 and still a third, which only recently has been abandoned by the 

 river, and over which the railway between Jager's Eiver and Union- 

 dale Eoad is carried for some distance. In this one area, therefore, 

 we have all the stages in the development of the plateaus, each 

 formed during a period of no downward erosion of the river, due 

 to stoppage in its course. The gravel covering the high plateau is 

 in places exceedingly coarse, and the' boulders are not rounded ; the 

 matrix is yellow clay not usually impregnated with iron, but which 

 becomes flint-hard by the deposition of silica. The lower plateaus 

 are not capped with gravel, but were once probably covered with 

 soil, which has not had an opportunity of hardening, and has con- 

 sequently been washed or blown away. 



At Paarde Kloof there is an isolated hill to the west of the home- 

 stead, cut out of white gravel and sand belonging to the Enon 

 Conglomerate, which dip steeply to the south-west ; the summit of 

 the hill reaches the level of the plateau, and is covered with the high- 



