436 W. M. DAVIS OBSERVATIONS IN SOUTH AFRICA 



independent of the general baselevel of the ocean, and that such a plain 

 might afterward be dissected if its rivers were increased in volume by a 

 change to a more humid climate or if a warping of the region should give 

 it easy drainage to the sea. Passarge indeed instances the peneplain of 

 the Kalahari, which seems to be in a general way continent with that of 

 the Veld, as an actual example of arid leveling — that is, of long continued 

 erosion under arid conditions — at its present altitude. His opinions on 

 this point are set forth in the second and third articles given under his 

 name in the list of references at the end of this paper. I have recently 

 presented some general considerations with respect to this problem in an 

 article entitled "The geographical cycle in an arid climate." 



If we accept Passarge's explanation, the highlands of South Africa 

 need not be regarded as having been elevated since they were worn down 

 to small relief ; they may be interpreted as having been produced at essen- 

 tially the same altitude as that in which they stand today. The dissec- 

 tion which they are now suffering, particularly around the margins, 

 should not be looked upon as the result of river revival by elevation, but 

 of river extension by change of climate, or (especially on the east) by 

 some downward tilting or warping of the marginal region which would 

 aid the escape of its rivers to the sea. It thus becomes an interesting 

 problem to inquire if any critical and distinguishing features can be dis- 

 covered by which the origin of the South African highland in one or the 

 other of these two ways may be demonstrated. 



There can be no question that much exploration is needed before a final 

 demonstration of either normal baseleveling or of arid leveling can be 

 reached. In the meantime the following suggestions are offered for 

 consideration. 



THE VELD REGARDED AS A NORMAL PENEPLAIN UPLIFTED 



If the highland of the Veld be regarded as a normal peneplain, now 

 evenly uplifted, it should possess well developed river systems, more or 

 less fully revived in consequence of elevation, and it should be sur- 

 rounded on its ocean border by a coastal plain whose marine strata would 

 contain part of the material removed from the peneplain during its 

 degradation. The Orange and other river systems of the Veld are there- 

 fore expectable features of the Veld, according to this theory; but the 

 pans or undrained hollows of the Veld are against it, and the general ab- 

 sence of marginal marine strata proves that a broadly uniform elevation 

 of the region did not take place. The only approach to a coastal plain is 

 found along the part of the ocean border in Natal. 



