Vol. 54.] WITWATEESRA.ND AJSTD OTHER DISTRICTS IN S. TRANSVAAL. 79 



the latter appear the subjacent Hospital Hill Series is invariably 

 present, and although there may be occasionally some variation in 

 the (lip of the two series, this may be attributed to the action of 

 strike-faults, as already suggested, by Gibson.^ I have observed no 

 evidence of folding, and estimate the thickness of the Hospital Hill 

 Series at 8000 to 10,000 feet. 



2. The Witwateesrand Beds. 



This name "was used by Penning to embrace the whole of the 

 quartzite-and- conglomerate series, including the underlying Hospital 

 Hill Series ; and since no better name has been suggested I shall 

 continue to use it, but in the more restricted sense, excluding 

 the Hospital Hill Series. 



Distribution. 



In the main section (Witwatersrand) the quartzites and con- 

 glomerates of this series crop out on fairly flat or gently sloping 

 ground south of the Hospital Hill range. The strike is here east- 

 and-west, and the dip south. The industr)^ of the Witwatersrand is 

 concentrated along the line of outcrop of the conglomerates known 

 as the ' Main E,eef,' and an uninterrupted line of head-gears, smoke- 

 stacks, machine-shops, and other structures demarcates its course 

 from Boksburg to Krugersdorp, a distance of 30 miles. 



At Krugersdorp the beds turn to the south-west ; the con- 

 glomerates are clearly exposed on B,andfontein, Droogeheuvel, 

 Haartebeestfontein, Witfontein, and Elandsfontein. On the latter 

 farm they pass under the dolomite. Like the Hospital Hill Series, 

 they emerge again west of Frederikstad, and can be followed past 

 Buffelsdoorn on to Klerksdorp and thence to the Vaal River. 



Twelve miles east of Johannesburg, namely, at Boksburg, the 

 Witwatersrand Beds are covered by the Coal-beds of the Karoo 

 Formation ; but 4 or 5 miles farther east they emerge again on 

 the farm Benoni, and can be followed thence through Vlakfontein 

 and Modderfontein to Klipfontein, where they once more pass under 

 the Karoo Formation. Their next appearance is at the Nigel Mine, 

 striking east and west, but dipping north. A section drawn between 

 Johannesburg and the Nigel, a distance of about 30 miles, discloses 

 the existence of a very complete syncline. Starting immediately 

 north of Johannesburg, we have above the Archaean rocks the 

 following succession of beds dipping south : — 



Hospital Hill Series. 



Witwatersrand Beds, with the different series of conglomerates. 



Klipriversberg Amygdaloid. 



Black Beef. 



Dolomite. 



Continuing the section, the same beds are then recrossed, but out- 

 cropping in the reverse order and dipping north, the section 

 terminating with the Archaean rocks. 



^ Quart. Journ. Geol. Soc. vol. xlviii (1892) p. 423. 



