\ 



0. B. Horivood (^ A. Wade— The Old Granites of Africa. 547 



Messrs. Chalmers and Hatcli ' have shown how very noticeably in 

 Mashonaland and Matabeleland the physical features are largely 

 dependent on the geology of the country. Thus the bulk of the 

 country is granite, the remainder consists chiefly of schists, and 

 the areas covered by granite present a bare, rocky, rugged aspect, 

 which is remarkable for its uniformity over large areas, or else 

 broad expanses of flat or rolling veld, from which rise here and 

 there masses of immense boulders and rugged kopjes. At intervals 

 the granite rises into wild mountain ranges. The schists occur as 

 broad patches in the granite and form the gold belts of the country. 

 Instead of the sandy sterile soil of much of the granite areas, the 

 schists give rise to a clayey fertile soil, produce softer, less rugged, 

 scenery, more undulating aud hilly, with fertile valleys and well- 

 wooded hills, owing to the more variable nature of the rocks and 

 also to the fact that they are tilted at high angles so that they are 

 more easily weathered. 



Dr. F. W. Voit,^ in describing the geology of German South- West 

 Africa, says : " It is so easy to see at a glance the difference in the 

 character of the landscape between a schistose and granite area." 

 He speaks of the schist districts as presenting a very undulating 

 land surface, from which rise hills to a height of from 1300 to 

 1600 feet, culminating in serrated kopjes and flat-topped ridges, and 

 covered with thick bush and grass. In the granite area, on the other 

 hand, rocks, like islands, rise out of a coarse-grained sandy floor with 

 startling abruptness, or form characteristic half-coned hills or gigantic 

 granite cones, almost completely barren of vegetation. 



The copper deposits of this region occur in the schists and gneiss 

 zones and not in the granite proper.^ However, granite areas may also 

 be undulating and fertile, as, for example, the granite boss between 

 Johannesburg and Pretoria, which is only sparingly wooded. 



Mr. W. Anderson* has pointed out that in metamorphic and 

 granitic areas, where the rocks are more or less crystalline and 

 contain chiefly quartz, felspar, hornblende, mica, etc., the soils 

 resulting from the former (gneisses, schists, etc.) are generally of 

 a decidedly clayey nature, while those derived from the latter are 

 of a more sandy character, though still containing much clayey 

 material from the decomposition of the felspars. Also that the 

 chemical constituents of the ordinary minerals in these rocks — potash, 

 alumina, silica, lime, magnesia, etc. — are such as are necessary for 

 the formation of a good soil ; and that the reason why granitic areas 

 are not, except in rare cases, much used for agricultural purposes is 

 a physical geological one, surface denudation of these rocks generally 

 producing a very rugged country, which is always against the 

 preservation of the soils for agricultural use ; but where it happens 



^ " Notes on the Geology of Mashonaland and Matabeleland," by J. A. Chalmers 

 aud Hatch : Geol. Mag., 1895, Dec. IV, Vol. II, No. ccclxxi, p. 193 et seq. 



- " A Contribution to the Geology of German South-West Africa," by Dr. F. "W. 

 Voit : Trans. Geol. Soc. S.A., vol. vii, pt. ii, p. 84. 



^ Loc. cit., pp. 77-94. Also vide "Copper Ore in South-West Africa", by 

 J. Kuntz : Trans. Geol. Soc. S.A., vol. vii, pt. ii, pp. 70-6. 



* Second Report of the Geological Survev of Natal and Zululand, by Wm. Anderson, 

 F.R.S.E., Government Geologist, 1904, p. 23. 



