159 



sandstone, are bound to be poor all round. It would, in fact, be difficult 

 to understand whence they could derive any natural fertility : the root 

 of the tongale, nearer Worcester, is less dominated by the sandstone, and 

 the calcareous matrix of the Enon conglomerate, which prevails there, 

 exercises an undoubtedly advantageous effect upon the soil. The follow- 

 ing are the analyses of the soils collected from this strip, beginning with 

 the sandstone-encircled tip and working downwards : 



II. TONGUE OF MALMESBURY SERIES EXTENDING FROM THE VICINITV OF 

 ROBERTSON TO THE WINTERHOEK MOUNTAIN NORTH OF TULBAGH. 



Phosphoric 

 Division. Farm. Fine earth. Water. Lime. Potash. oxide. 



Tulbagh. Misgund. 73'4 "95 '044 '032 "023 



Knolle Vallei. 61'4 T49 "068 '038 '047 



98-7 5-75 "008 "030 '023 



Kluitjes Kraal. 94'8 2'92 "070 "095 '070 



Worcester. Breede River. 83'4 T34 '086 '027 '034 



Wilge Eivier. 53'7 219 150 147 "093 



Eendracht. 100 2'09 '066 '037 '069 



Hartebeest Eivier. 70'9 '79 '016 '091 '051 



Zeekoegat. 89'6 T59 '260 195 "089 



Tweefontein. 70'0 "78 '038 158 '078 



Nonna, 75'5 1'45 156 '068 '063 



In many places the soils resulting from the rocks of the Malmesbury 

 series are diversified by the intrusion of granite. The consequent diver- 

 sity is more than becomes evident at first sight, for, although poverty in 

 plant food is practically inherent in the soils of the Malmesbury series, 

 it is otherwise with those derived from granite. The latter possess at 

 least the potentiality of fertility. This is owing to the fact, that, while 

 the Malmesbury rocks are deficient in plant food constituents, the intru- 

 sive granite is not, and thus the resulting granitic soils impart to the clay 

 slate soils, when mixed with them, not only plant food constituents, pro- 

 portionate to the relative quantities in which the two classes of soil are 

 mixed, but also actual plant food, proportionate to the amount of decom- 

 position that the granite has undergone. Where the granite has not been 

 sufficiently decomposed, the elements of fertility contained in its consti- 

 tuent minerals are not available for the plant. In other words, suffi- 

 ciency of plant food constituents may then be present in the soil while 

 there is lack of plant food. The diversification of the clays derived from 

 the Malmesbury slates, consequent upon the introduction of granite as a 

 soil-forming factor, is therefore dependent not only on the relative quan- 

 tities wherein these two classes of rock contribute to the formation of any 

 particular soil, but also on the stage which the mechanical disintegration 

 and chemical decomposition of the granite has reached. 



These facts naturally add to the difficulty of laying down anything 

 like a typical composition even for unmixed granite soils. Of several 

 granite soils that had been analysed by Professor Hahn, in one an allu- 

 vial soil the constituent minerals of the granite had completely decom- 

 posed, and the results of the analysis of this soil were : 



Lime '281 



Potash "151 



Phosphoric oxide '172 



