440 W. M. DAVIS OBSERVATIONS IN SOUTH AFRICA 



Passarge places much emphasis on the abrupt transition between hill 

 slope and plain surface as a feature explicable only on the supposition of 

 erosion under an arid climate. We saw several rather striking examples 

 of this kind in the district of the Matopos near Bulawayo and also along 

 the eastern border of the Kalahari region, which we passed on the rail- 

 way, and were disposed to regard Passarge's explanation of them as cor- 

 rect; but it does not follow that, because the erosion of these plains was 

 carried on under an arid climate, they were therefore developed inde- 

 pendent of normal baselevel. There are several arid regions in the world 

 close to the seacoast where erosion is proceeding today with respect to 

 the ocean as a baselevel, and it does not seem inconceivable that the ero- 

 sion of the Veld, even under a more arid climate than that of toda} 7 , may 

 have been accomplished by one or more river systems which, when they 

 had water to run, flowed to the sea, and that the present altitude of the 

 region has been gained by later elevation. 



A pertinent suggestion offered by Chamberlin is as follows : Conti- 

 nental quietude being assumed, it then follows that, even if the climate 

 of South Africa had long been dry enough to permit the arid leveling of 

 the Veld, the contemporaneous climate of the equatorial belt must have 

 been moist enough to supply outflowing rivers; and these would have 

 produced a low-lying peneplain by normal processes in the same period 

 that sufficed for the production of the high-lying Veld by arid processes. 

 The equatorial belt of Africa is, however, not a lowland but a highland, 

 and its chief river, the Kongo, has falls near its mouth. Kelatively recent 

 uplift is thus indicated with a great degree of probability in the Kongo 

 basin, the fundamental postulate of continental quietude is thereby con- 

 tradicted, and the probability of uplift in South Africa is greatly in- 

 creased. The only escape from this conclusion seems to be a change of 

 climate sufficient to make even equatorial Africa arid; but this goes be- 

 yond the bounds of reasonable occurrence. The peneplanation of the 

 Veld at its present altitude consequently seems improbable. 



It remains, however, to consider one aspect of the matter which may 

 eventually, when the more complete history of South Africa is worked 

 out, come to be favorable to the supposition of arid leveling, namely-, the 

 former greater extension of the continent. 



THE FORMER GREATER EXTENSION OF SOUTH AFRICA 



It has been frequently suggested that South Africa once possessed a 

 greater land extension to the east, south, and west. There appear to be 

 many facts in favor of this view. If the continent were once larger, the 

 area of the present highlands must then have been drier than now, and 



