Vol. 62.] IN THE SOUTH-WEST OF CAPE COLOXY. 75 



the levelling process all trace of the Cretaceous deposits was removed, 

 except in these hollows, where the unbroken rim of the more consoli- 

 dated, older rocks protected them. When the plateau was raised, 

 these Uitenhage Beds exhibited the same levelled surface as the 

 rest of the rocks, and recent gravels were deposited upon them ; but 

 the enormous powers of downward erosion which the rivers now 

 acquired, attacked these loosely-made rocks and carried them away 

 to the sea : hence there are wide, open basins on the plateau 

 wherever the Cretaceous deposits occur. 



As regards the recent deposits found on many of the ridges of 

 the Huggens, I think that the greater part of them are formed 

 in situ — that is to say, before the country was cut up into these 

 ridges, there were extensive plateaux covered with thick sandy soil, 

 such as we now see is the case to the east in Knysna, on the same 

 plateau, though on a harder substratum of rock. Water percolating 

 through this soil would form the ironstone-gravel by cementing 

 the sand-grains with hydrated iron compounds, and the surface- 

 quartzite could be formed in the same way by the deposition of 

 silica. 



In Uniondale I have seen the process of formation of the burr- 

 stone going on. The plateau there has been cut, very thick deposits 

 of clayey sand have been piled upon it, and the gradual hardening 

 upwards, till the surface is glassy quartzite, can be studied. 1 Gravel 

 does exist on the ridges, and this cannot, except within very narrow 

 limits, be explained in a similar manner : when a hard reef projects 

 above the general level of the plateau (for instance, a quartz-vein 

 through granite), fragments, apparently waterworn, of the same 

 material are found in the loose sandy soil in the neighbourhood ; 

 but they have never been noticed actually to form gravelly deposits 

 (see fig. 1, p. 71). Yet gravel is not formed by river-action alone : 

 beaches are as common as river-gravels ; and Godwin-Austen as 

 long ago as 1849 recorded shingle on the English platform at from 

 80 to 100 fathoms below the surface of the water. 



Behind the mountains, we find the remains of plateaux cut in 

 various rock-systems, resembling the Uplands plateau in certain 

 features, only they are of considerably greater elevation. They are 

 covered with surface -quartzite, ironstone -gravel, and shingle, 

 exactly as in the coast-plateau. After studying both, I am unable 

 to distinguish the two deposits one from the other, and yet I 

 see as complete evidence for ruling out the action of waves from 

 the explanation of these inland plateaux, as I see for abandoning 

 the action of running water in explaining the formation of the 

 coast-ledge. We are not directly concerned with these inland 

 plateaux in the present paper ; they were described in the memoir 

 on the ' High-Level Gravels of the Cape, &c/ referred to above. 



1 See photograph in ' High-Level Gravels of the Cape, &c.' Trail's. Phil. Soc. 

 S. A. vol. xv (1904) pt. 2, pi. iii. 



