DOLERITE RIDGES AND TABLES 427 



condition is almost realized where the Veld is underlaid by stratified 

 rocks, but it has been already stated that doleritic intrusions in dikes and 

 sheets are not uncommon. Where these resistant rocks occur it is but nat- 

 ural that they should stand up in much more mature relief than that of 

 the old plains which have been worn down around them on the weaker 

 rocks. It is evident enough that if the whole region consisted of resistant 

 dolerite the surface would not now be worn as smooth as it is in the actual 

 areas of the weaker stratified rocks; for the time and the agencies that 

 have sufficed for the peneplanation of the latter would have hardly car- 

 ried the former beyond maturity. From what we could learn, it seems 

 probable that the Stormberg mountains, which rise along the southeastern 

 border of the Veld, are an example of such a more resistant district ; their 

 structure seems to be essentially horizontal, and they are said to contain 

 much dolerite. They may therefore be provisionally looked upon as rep- 

 resenting in their height and form something of the maturity through 

 which the weaker rocks of the Veld have long since passed. 



The side slopes of the ridges and mesas formed on the dolerite dikes 

 and sheets are suggestive of the slow erosive processes by which the ridges 

 are being slowly worn down. The crests and the steeper part of the upper 

 slopes consist chiefly of bare dolerite. There the agencies of removal are 

 somewhat in excess of the agencies of disintegration; rock fragments are 

 rolled down as soon as they are detached from the parent ledges. Farther 

 down, where the slope is less steep, it is covered with coarse waste or talus 

 from the bare ledges above. Here the agencies of removal are only able 

 to carry away the middle textured and finer waste that comes partly from 

 the disintegration of the coarse waste and partly from the disintegration 

 of the underlying rock. The talus-covered slope turns by a rather short 

 curve into the plain, where the soil is of relatively fine texture. Here the 

 agencies of removal are able to carry away only the fine waste that comes 

 from the relatively complete disintegration of the materials farther uphill 

 and of the underlying strata. Thus the talus slope as well as the plain 

 is essentially at grade with respect to the agencies and materials there 

 concerned, though the slopes of the two are very different; but the top of 

 the ridge is not yet reduced to grade. The front view of the ridges gives 

 one the impression that the talus slope and the plain meet at an angle ; 

 the profile view shows that the two surfaces are connected by a short 

 curve, as already stated, and close inspection shows that the plain near the 

 base of a ridge has a slightly greater declivity and a slightly coarser waste 

 cover than farther forward. It sometimes happens that the stratified 

 rocks may be seen through the talus slopes, especially on the slopes of 



