70 PRESIDENTIAL ADDRESS — SECTION li. 



is also present. Assays of several ounces to the ton have been 

 recorded, but the average platinum content of the ore appears 

 to be between ^ dwt. to i dwt. per ton. 



The ore clearly owes its origin to a process of gravitative 

 differentiation, and it is believed that ore bodies very much larger 

 than any hitherto exposed await discovery on the concealed floors 

 of the basins or cakes. Thus, the mineralised zone, on which 

 most exploratory work has been done at Insiswa, is in all prob- 

 ability only the eastern edge of a great lens-shaped mass of ore 

 underlying the Insiswa Mountain. The same applies to the Tonti 

 and Tabankulu occurrences, and as the massifs are of very great 

 size — ^that forming the Insiswa Mountain is ten miles in diameter 

 — it will be seen that the area offers enormous possibilities. Some, 

 indeed, see in it a second Sudbury. 



Apart from the value of its metallic contents, the ore is of 

 value as a potential source of sulphur. 



Petroleum. — The Karroo Province contains the only area 

 in the Union — namely, the so-called Folded Belt, along its 

 southern margin — within which some, at any rate, of the requisite 

 conditions for the formation and concentration of petroleum in 

 commercial quantities are satisfied. 



The prospects of finding oil in the Folded Belt are, as has 

 been pointed out elsewhere,* not very hopeful, because, if 

 present, it is probably so deeply buried as to be beyond com- 

 mercial accessibility, but the possibility of its being struck none 

 the less exists. 



Oil-Shale. — There are extensive deposits of oil-shale in the 

 Ermelo and Wakkerstroom districts of the Transvaal, and in the 

 Utrecht and Impendhle divisions of Natal, and equally extensive 

 deposits are said to exist in the north-eastern portion of the 

 Orange Free State. . The deposits are likely sooner or later to 

 form the basis of an important industry. 



Natural Gas. — Natural gas has so far only been struck in 

 considerable quantity on the farm Gruisfontein, in the Heidelberg 

 district of the Transvaal, f where it was encountered at a depth of 

 540 feet, beneath a dolerite sill, which acted as an impervious 

 cover. Cunningham Craig| is of opinion that there may be other 

 isolated and irregular reservoirs of gas in the area, and also 

 considers that the Fauresmith district of the Orange Free State 

 and the Folded Belt of the Karroo system offer favourable con- 

 ditions for the occurrence of gas. 



Diamonds. — The discovery of further workable occurrences 

 of Kimberlite within the Karroo Province may be predicted with 

 confidence, the neighbourhood of Kimberley and the north- 



* C/. S.A. Journal of Ivdustries, October, 1917. 



t Dr. Du Toit inforrhs me that an important strike of natural gas 

 was made some months ago near Dannhauser, in Natal. 



X Report on the Petroleum Prospects in the Union of South Africa. 

 Pretoria, 1914, P- T9. 



