458 MR. W. H. PENNING ON THE 



the Vaal River near Barkly, and may then be followed up along the 

 valley, past Christiana and Bloemhof, to Klerksdorp, where it over- 

 lies the Witwatersrand series. Thence it rises to cap the Gats- 

 Randt, where it rests on the Klip-River series, and its outcrop makes 

 a clear line of demarcation between the High-Veldt coal-deposits and 

 the Megaliesberg formation. 



Brief mention may also be made of a volcanic rock (h), of which 

 but few small patches remain, overlying this coal-formation. East 

 of Boksburg it caps a small hill as a bluish-grey basalt, which 

 weathers into rounded lumps of a dark-brown colour. North of 

 that place it is seen in section overlying grey and black paper- 

 shales, sometimes micaceous, with coarser sandstone below ; here 

 the volcanic rock is weathered into a soft grey mass with numerous 

 small concentric nodules. In this locality, and near the base of the 

 formation, there is a bed of loose, calcareous, sandy clay, enclosing 

 many water worn pebbles, some of large size, derived from the 

 " bankets " and quartzites of the subjacent formation; this is an 

 old alluvium to which further reference will be made. 



A few additional sections may be enumerated as follows : — 



East of the Wilge River, the Holfontein mines give a good 

 section : — 



Coarse sandstone, 

 ft. in. Shale. 



21 Coal, with a constant thin parting of shale about the 

 middle ; the best coal below. 

 Sandstone. 



On the farm " Witklip," forty miles E. of Johannesburg, in the 

 " Greville Colliery," the following section is obtained : — 



ft. 



in. 





20 







Loam, over calcareous clay. 



4 







Sand and pebbles. 



11 







Shale, dark in colour. 



3 







Sand and pebbles. 



19 







Shales. 



4 







Shales, with thin layers of coal. 



15 







Coal. 



The Boksburg Collieries have seams of coal of varying thickness. 

 The " Brakpan" colliery-shaft goes down 58 feet to coal, which is 

 over 20 feet thick, including a bed of sandstone about a foot thick. 



South of the Zuikerbosch-Randt River, on the farm " Modder- 

 fontein," two pits, 14 feet deep, show : — 



ft. in. 



Grey sandstone. 



3 



Shale. 



G 



Coal. 





Sandstone. 



South of the Vaal River, opposite Klerksdorp, the mine of the 

 Kroonstad Coal-Company is in — 



