Yol. 50.] OF SOUTH-EASTEKlSr AFRICA. 557 



of the continent as at present existing. Consequently the shores 

 of any lake in which such a vast deposit of sedimentary material 

 (comprising the Ecca, Karoo, and Molteno Beds) could have been 

 accumulated must have extended far beyond the present boundaries 

 of the continent, and could scarcely be called a ' central lake-basin 

 of the Karoo,' for this would lead one to believe that its area was 

 limited by what is geographically called ' the Karoo.' 



The differences of thickness observed in the Dwyka Conglomerate, 

 Ecca, Karoo, and Molteno Beds lead us to suppose that great oscil- 

 lations of the surface occurred during their deposition. 



The Dwyka Conglomerate, Ecca and Beaufort Beds thin out 

 rapidly northward, and die away completely near the Pongolo 

 lliver, although they attain a thickness of over 700 feet 50 miles 

 away towards the south ; the Ecca and Beaufort Beds also thicken 

 southward. On the other hand, the Molteno Beds thicken in the 

 contrary direction, thinning rapidly southward. 



Apparently, during the deposition of the Dwyka, Ecca, and 

 Beaufort Beds, dry land existed in the central portion of South 

 Africa, notably at what is now the great northern watershed of the 

 Witwatersrand, and the high-lying portions of the High-veld plateau, 

 and extended southward to the present boundaries of Natal. 



This dry land consisted of granite and Primary rocks. The 

 Dwyka, Ecca, and Beaufort Beds are seen to die out against these 

 rocks wherever they are found in South-eastern Africa. On the 

 other hand, the Molteno Beds overlie the highest eminences of 

 Primary rocks and granite, even to the top of the Klip Stapel near 

 Lake Chrissie, 7000 feet above sea-level. 



The non-existence of the Cave-sandstone and the volcanic beds 

 north of Natal and Basutoland respectively can scarcely be taken 

 as definite evidence that they never were deposited there. The 

 vast amount of denudation which has occurred on a territory that 

 has not been submerged since the close of the Jurassic period 

 will account for the removal of immense bodies of rock. At the 

 same time the Cave-sandstone is by no means so important a 

 formation north of the town of Harrismith as it is southward ; and 

 there are evidences of a thinning of this series northward. 



In the south-eastern portion of South Africa I have failed to find 

 the evidences of disturbance in the Ecca and Dwyka Beds described 

 by Prof. A. H. Green in Cape Colony. The only great unconformity 

 that I could discover was between the Malmesbury Schists and the 

 Table-mountain Sandstone. The former are tilted and highly con- 

 torted, occasionally being quite perpendicular ; the latter lies hori- 

 zontally upon their upturned edges ; the Dwyka Conglomerate, and 

 all the overlying sedimentary deposits, follow conformably one to the 

 other. As previously mentioned, all the strata lying horizontally 

 in the inland area dip rapidly seaward when observed near the coast, 

 in consequence of the great fault along the coast-line. 



There is a marked distinction between the material composing 

 the Dwyka Conglomerate and the Ecca Beds immediately overlying 

 it, and consequently the junction of these two series is easily 



