100 Dr. F. H. Hatch — Geological History of South Africa. 



Mr. Dorffel.^ But what is the nature of the evidence that he would 

 deem satisfactory to establish the relation of the Witwatersrand 

 Beds to the granite ? They are seen in contact at numerous places, 

 but nowhere is the latter found penetrating or sending off apophyses 

 into the former. Neither do the sediments show anywhere any sign 

 of contact metamorphism. On the contraiy, they appear to have 

 been accumulated on an ancient granite floor. If the granite were 

 later than and intrusive into the Witwatersrand Beds, surely some 

 evidence of this would be forthcoming. It is true that Mr. Kynaston 

 does not deny the possibility of an unconformable relation, but he 

 records the evidence as insufficient. 



Now this is a question which affects the mapping of thousands 

 of square miles of country ; it is besides important to the public 

 from a mining point of view. I will give an instance — bore- 

 holes put down by exploration companies through the overlying 

 covering of Karroo rocks or Dolomite are invariably stopped if they 

 should reach the Granite. Is the doubt as to the usually accepted 

 relation of the Granite to the Witwatersrand Beds so strong in 

 Mr. Kynaston's mind that he would advise the continuation of such 

 boreholes ? We unfortunate geologists and mining engineers, who 

 have to take practical views of such matters, are not allowed the 

 luxury of academic doubt. Further, the important question is 

 involved as to the relation of the Witwatersrand Banket to the 

 conglomerates and quartzites that occur in association with schistose 

 rocks in the Barberton and Pietersburg districts, and in Swaziland 

 and Mashonaland, a question which has recently been much dis- 

 cussed, owing to the prominence given to the so-called banket 

 occurrence at Lomagunda in Rhodesia, and its correlation with the 

 Witwatersrand rock.^ I maintain that instead of shelving questions 

 like these, the Survey should investigate the facts, and establish 

 definitely the relation of the Witwatersrand Beds to the Old 

 Granite, and the existence or non-existence of an older system 

 of sedimentary rocks. These are questions of vast importance to 

 the mining industry, and call for as early a settlement as possible. 



While the maps produced by the Survey are a fit subject for 

 congratulation there is room for a difference of opinion as to the 

 line on which the survey work should be carried out. Personallj'^ 

 I am of the opinion that in the present stage of the development 

 of the country the most good would be done, not by giving us 

 detailed maps (however excellent in themselves) of outside districts, 

 but by settling the lax-ge questions which its Director holds still 

 requii'e solution. 



While on the subject of the Survey I will touch on another 

 question, of the importance of which Mr. Kynaston is as fully 

 cognisant as we are. The maps issued by the Survey since its 

 reorganisation in 1902 cover an area of about 4,100 square miles. 



1 D. Dorffel, "Note on the Geological Position of the Basement Granite": 

 Trans. Geol. Soc. S. Afr., vol. vi (1903), pp. 104-105. 



2 F. P. Mennell, "The Banket Formation of Ehodesia": Trans. Geol. Soc. 

 S. Afr., vol. viii (1905), p. 82. 



