D)\ F. H. Hatch — Geological History of South Africa. 101 



This is a very creditable performance considering the smallness of 

 the staff. But a simple computation will show that at this rate 

 of progress some 30 years will be required to finish the work 

 unless the staff be augmented. The importance of rapidly com- 

 pleting the geological survey of a country, dependent as this is for 

 its future welfare on the development of its mineral resources, 

 oannot be too strongly impressed on the authorities ; and to 

 accomplish it the staff must be largely increased. I am glad 

 that we can welcome an additional field geologist in the person 

 of Dr. W. A. Humphrey, who has had part of his training in 

 South Africa, and we may trust that this is an augury of the 

 Government's recognition of the importance of the work, and of 

 its intention to carry it out with the least possible delay. 



I will pass on now to a consideration of the data available for 

 deducing the thickness of the South African formations. 



2. Thickness of the Strata. 



Since we know neither the base nor the summit of the Swaziland 

 system no estimate can be made of the thickness of these ancient 

 rocks, which are partly of sedimentary, partly of igneous origin, 

 but have in both cases been profoundly modified. There can be 

 no doubt, however, that they are very thick, and that an immense 

 quantity of material has been removed by erosion since their first 

 upheaval. Kecently, in a paper read before this Society, Dr. Voit^ 

 has expressed the opinion that certain banded gneisses of the 

 Northern Transvaal should be separated from the Swaziland system 

 as an older fundamental gneiss, corresponding, say, for instance, to 

 the Laurentian rocks of Canada and the Lewisian gneiss of Scotland. 

 As, however, he describes no section from which the relation of 

 these gneisses to the remainder of the Swaziland system can be 

 inferred, and since it is by no means certain that these gneisses 

 are anything else than a sheared or metamorphic portion of the 

 granite, which in other places is found intrusive in the Swaziland 

 Beds, it must be premature in the present state of our knowledge to 

 attempt any such subdivision. 



With regard to the Witwatersrand System, the shales and quartzites 

 of the lower division have on the Band a thickness of 12,000 feet ; 

 the upper division, if we exclude the Elsburg Series, about 7,000 feet ; 

 in all about 19,000 feet. The necessity of separating the Elsburg 

 Series from the Witwatersrand Beds, which was advocated by 

 Dr. Corstorphine and myself in a paper on the Geology of the 

 Bezuidenhout Valley, read before this Society, is again shown by 

 fresh evidence from the Klerksdorp district, which will be made 

 the subject of a paper by Mr. Torissen. This series of conglomerates 

 and quartzites has on the Band a thickness of from 3,000 to 

 4,000 feet. I include it with the Yentersdorp System. 



The thickness of the latter system, which includes boulder beds, 

 coarse conglomerates, volcanic breccias and lavas, is very difficult 



1 F. W. Voit, " Gneiss Formation on the Limpopo " : Trans. Geol. Soc. S. Afr., 

 Tol. viii (1905). 



