Xyi Journal of thh Department of Aoriculture. 



largely ol quartz o-rnins which are rounded to ouly a small degTee. It 

 contains angular fragments of microcline and ortboclase (potash 

 felspars), fragments of plagioclase (a lime-soda felspar), and a little 

 white mica (a potasli-magnesian mineral). There would not appear 

 to have been made any numbei' of chemical analyses of representative 

 samples of this group, or indeed of any of the groups of the Stormberg 

 series, but the following ])artial analyses taken from the 1902 re])or1 

 of the Geological Commission are quoted for what they are wortli : — 



I. Cave sandstone from N'Quatsha's Xek. 

 II. Greenish blue standstone from red beds below the forinei-. 

 III. Typical red day that occurs in the cave sandstone and red 

 beds. 



I. 



Silica 83.5 



Calcinni oxide ... .07 



Sodium oxide 1 .55 



Potassium oxide... 1.44 



One would have liked to find in the Geological Commission's 

 Iicpoits quantitative idiemical analyses of typical specimens of locks 

 from several localities, and it is furtiier a matter of great regret that 

 no figuies for the i)hospboric oxide contents of the various rocks are 

 available. No doubt the Director of the Survey recognized the 

 desirability of such records; but in a new country many things have 

 to wait. It should, however, be obvious that such quantitative data 

 would considerably increase the value of the geological survey to 

 agriculture. 



Reference has already liecn made 1o llie thickness of the cave 

 stnidstone at the boundary of Yaalbank and Dankfontein ; on AVonder- 

 ])oort it is about 150 feet thick, and no more than 40 feet in the 

 neighbourhood of Dankfontein's Nek, a point neai" which samples 

 Nos. 608 and 60!) were collected. 



The most remarkable feature of the cave sandstone is the fantastic 

 shapes into which it weathers. Often the rock is hollowed out below 

 so as to form shallow caves, in which the ])rimitive Bushman artist- 

 hunter lived, decorating the pale-coloured walls of his abode with 

 characteristic paintings of men and of animals, done in red, yellow, 

 and black pigment. Such paintings may still be seen near the head 

 of the kloof that descends from the plateau down to the Witkop 

 homestead. 



Since cave sandstone consists mainly of silica in the shape of 

 quartz grains, and since it would seem to be poor in all plantfood- 

 containing minerals, it is to be expected that the soils derived solely 

 from it will be of a rather poor, fine, sandy type: while it is also to be 

 expected that conjointly with volcanic beds or dolerite it would give 

 rise to a fairly fertile and easily worked soil. 



Red Beds. — These beds are so called owing to their characteristic 

 colour. The junction between them and the cave sandstone is well 

 marked, but it is not always easy to draw the line which divides them 

 from the lower Molteno beds. 



The most characteristic locks of the group are red, purple and 

 blue mudstones and shales. Red sandstones and yellow and white 

 fine-grained feLspathic sandstones are also common. Calcareous 



