Dr. F. H. Hatch — Geological History of 8outh Africa. 103 



informs nie that his figures work out to 9,900 feet, which is in 

 very close agreement with the estimate of the Survey. We have, 

 therefore, a maximum aggregate thickness for the three members 

 of the Potchefstroom System of about 18,000 feet. 



The thickness of the Waterberg Sandstone has not been measured 

 in any place where there is anything approaching a complete 

 section. The lower beds, however, have been carefully examined by 

 Mr. Mellor in the Rhenosterkop area, and were found by him to have 

 a thickness of 3,150 feet.^ The Table Mountain Sandstone, which 

 appears to be the Cape representative of the Waterberg,^ is estimated 

 by the Cape Survey to have a thickness of 5,000 feet, and there can 

 be very little doubt that the Waterberg formation is at least 

 as thick. 



The Bokkeveld Beds, which succeed the Table Mountain Sand- 

 stone at the Cape, are estimated by the Cape Survey at 2,500 feet, 

 and the same thickness is given to the Witteberg Beds, making 

 a total thickness for the Cape System of 10,000 feet. The Bokkeveld 

 and Witteberg Series are, however, absent in the Transvaal. 



According to Mr. Eogers,^ the Karroo System has a thickness of 

 18,000 feet, of which 4,900 feet is apportioned to the Dwyka and 

 Ecca Series, 5,000 feet to the Beaufort Beds, and 8,200 feet to the 

 Stormberg, 4,000 feet of the latter being occupied by the volcanic 

 group which forms the summit of the system. 



Summarising, we have the following maximum thickness for the 

 South African stratified rocks : — 



Karroo System 18,000 feet. 



Cape System (in which, is included the Waterberg 

 formations, as correlative with the Table 



Mountain Sandstone) 10,000 ,, 



Potchefstroom System about 18,000 ,, 



Ventersdorp System about 8,000 ,, 



"Witwatersrand System 19,000 ,, 



Excluding the Karroo Beds, there remain some 55,000 feet of beds 

 (say 10 miles) lying below the base of that system and above the 

 Swaziland Beds, or, in other words, below the Permo-Carboniferous 

 of Europe. When we take into consideration the gaps represented 

 by four great unconformities, we see that the ' geological column ' 

 must necessarily be much greater than this total, since no allowance 

 is made for the losses due to denudation. It probably embraces the 

 period of time covered by the Devonian, Silurian, Ordovician, and 

 Cambrian Systems of the European classification. 



Unfortunately, no correlation with the European formations is at 

 present possible, on account of the complete absence of fossils in all 

 the South African formations below the Bokkeveld (Devonian) 

 Beds.^ But we need not despair of finding organic remains in some 



1 Transvaal Geol. Surv. Eep., 1904. 



2 F. H. Hatch & G. S. Corstorphine : " The Geology of South Africa," p. 309 ; 

 London, 1905. 



2 A. W. Rogers: " The Geology of Cape Colony," p. 147; London, 1905. 

 * Quite recently some lamellibranch remains have been found by the Cape Survey 

 in the Table Mountain Sandstone, but have not yet been determined. 



