420 W. M. DAVIS OBSERVATIONS IN SOUTH AFRICA 



and of the polar flattening. The shifting of the poles is therefore at 

 present not only a daring hypothesis, but gratuitous and discredited as 

 well. Nevertheless, if evidence of Permian warm climate were found 

 around a zone that would be equatorial to an Indian Ocean polar area, 

 and if another Permian glacial area were found in the regions antipodal 

 to the Indian ocean, this daring, gratuitous, and discredited hypothesis 

 would have to be taken seriously into account. 



The cause of the Dwyka glaciation for the present remains a puzzle, al- 

 though the fact of the glaciation is well established. 



The Interior Highland: The Veld* 

 the scheme of the geographical cycle 



Our rapid journey inland from Cape Town as far as Johannesburg and 

 Victoria falls, and then eastward to Beira on the Portuguese coast, gave 

 a particular pleasure to some of the geographically minded members of 

 the party, who attempted to refer the various land forms that were seen 

 to their appropriate place in the scheme of the geographical cycle. This 

 scheme recognizes that if the ordinary processes of erosion carry on their 

 destructive work without interference by crustal movement or by climatic 

 change for an indefinitely long time, they will eventually wear down any 

 land area, whatever height and form it originally had as a result of up- 

 lifting forces, to a nearly featureless lowland, hardly above sealevel. On 

 such a lowland plain the further processes of erosion must be very slow ; 

 the rivers would* have long since, reduced their courses to gentle grade, 

 with extremely faint declivity toward their mouths in the sea ; the branch 

 streams would have given up the torrential activity of their youth and 

 become sluggish tributaries in their old age; and the smaller rills would 

 have been largely extinguished by lack of ground-water discharge in 

 springs on the flattened land slopes, for the hills that rose between the 

 eroded valleys during the stage of vigorous maturity would by this time 

 have been worn down to faint swells, seeming almost level to the eye, and 

 the ground-water would find few points of emergence until the larger 

 channels were reached. The waste of the land, prevailingly of fine text- 

 ure, would be slowly washed down the nearly imperceptible slope of the 

 swells toward the streams, and carried by the streams and rivers along 

 their well ordered courses to the sea. The watercourses would not follow 



♦This section of the present article is expanded from the notes of an informal address 

 given on the deck of the steamer Durham Castle during the return voyage of the British 

 Association party from Beira, by the east coast of Africa, to Southampton, September-October, 

 1905. 



