l82 THE DESICCATION OF AFRICA. 



into existence within a few generations, but must have required 

 an enormously long period of time for its evolution. The 

 (further development of this line of argument must be left to 

 botanical authorities, such as Dr. Pole Evans and others, who, 

 it is hoped, will take part in this discussion. 



Secondly, from the geological and physiographical point of 

 view, evidence most strongly supports the theory of the extreme 

 age of the present arid conditions. The great vleis in the 

 Karroo, which, in the past, were such a feature in the landscape, 

 but w'hich are now unfortunately, to a large extent, arid and 

 eroded flats, due to causes already mentioned, have obviously 

 come into existence only throughout a long period of arid 

 conditions. In this connection, Mr. Kanthack cited examples of 

 the nature and formation of such vleis as derived from experi- 

 ences in building dams in the Karroo, more especially the 

 valuable evidence obtained in the building of the great dam on the 

 Smartt Syndicate Estate in the Britstown district. He further 

 drew comparison between the conditions under which these vleis 

 had been formed and the formation oif the great Loess plains 

 and steppes of South-East Europe. He also drew attention to 

 the interesting discovery of a fossil skeleton of a large saurian 

 in the Henkries Valley in Northern Namaqualand, which was 

 recently discovered by Dr. Rogers, and which was embedded in, 

 and entirely covered by, deposits of material derived from 

 erosion under extreme arid conditions, which pointed to the 

 extreme length of time throughout which desert conditions had 

 obtained in that part of Namaqualand. 



Thirdly, he pointed out that agricultural evidence indicated 

 clearly in the Cape Province that, with soils derived from 

 identical geological formations, the degree of fertility was, more 

 or less, in inverse proportion to the rainfall. Thus the alluvial 

 soils of the most arid parts of the Karroo were vastly more fertile 

 than the soils derived from almost exactly the same geological 

 formations situated further east in regions of much greater 

 rainfall. 



Fourthly, there is the historic evidence contained in old 

 accounts of travels of high ofificials, etc., which are to be found 

 in the Cape Archives, in which frequent reference is made to the 

 most severe droughts. 



All the above, and much more evidence of a varied 

 character, goes to show that the present arid conditions of the 

 Karroo are of enormously longer standing, and that if, as is 

 asserted, any great changes took place in the northern parts of 

 Bechuanaland such as the sudden drying up of the N'Gami and 

 Makarikari Lakes, these catastrophes made no impression upon 

 the climatic conditions of the Karroo, either for the worse or for 

 the better. , ., 



It remains to deal with the problem from the meteorological 

 point of view, which, in many respects, is the most important 

 aspect of the case. This was, however, a matter which Mr. 

 Kanthack stated he preferred to leave in the hands of authorities 



