THE DESICCATION OF AFRICA. 183 



on -meteorology, such as Mr. Charles Stewart, Chief Meteoro- 

 logist for the Union. 



Dr. I. B. Pole Evans. M.A., F.L.S., Chief of the Division 

 of Botany, Union Department of Agriculture, said that he was 

 much in the same position as the previous speaker (Mr. 

 Kanthack) ; in that he had not yet had an opportunity of reading 

 through Professor Schvvarz's interesting paper; he could there- 

 fore, in the short time at his disposal, only touch upon a few of 

 the points which had occurred to him whilst listening to Pro- 

 fessor Schwarz. 



The first point was that with regard to Professor Schwarz's 

 suggestion that at one time in the history of Africa some of the 

 great rivers instead of flowing directly into the oceans first ran 

 inland. If such had been the case one would naturally expect to 

 find evidence of the peculiar coast-belt flora in the interior along 

 the courses of these rivers. As far as he was aware, there was at 

 present no evidence of a botanical nature to support this view. 



The second point was with regard to Professor Schwarz's 

 idea that the desert conditions of the KarroO' were of com- 

 paratively recent origin. The botanical evidence certainly did 

 not bear this out, for the Karroo flora was of a very highly 

 specialised type. All the organs, such as the leaves, stems, and 

 roots, were constructed either for the purposes of storing water 

 or for preventing the evaporation of water. Such a high degree 

 of specialisation could not possibly have been brought about in 

 even a comparatively short geological period of time. 



Furthermore, it was common knowledge that the Karroo 

 xerophytes were the most difficult of all plants to grow out of 

 their natural habitat, and could not be easily acclimatised by man 

 like many of our other plants. 



By creating such a huge mass oif water as Professor 

 Schwarz proposed in the interior of the continent, it must be borne 

 in mind that we would be disturbing the balance ui nature, and 

 it would be very difficult to predict, without considering the 

 matter in all its aspects from a biological standpoint, whether the 

 presence of such a lake would be to the benefit of the country or 

 otherwise. 



_ Mr. C. M. Stewart, B.Sc, Chief Meteorologist of the 

 Union, said that before proceeding to make any comments, he 

 must express his admiration for the originality and boldness of the 

 ideas contained in Professor Schwarz's paper. 



Apart from the geological aspect of the probable cause of 

 aridity, the most important because the most practical considera- 

 tion in connection with this proposed scheme is the probable 

 effect of such a body of water on the climate of South Africa. 

 There are certain results which would naturally ensue from the 

 damming up of a body of water 15,000 square miles in area. 

 Among these may be mentioned, first, a modification of the local 

 atmospheric circulation similar to the land and sea breezes of the 

 coastal districts. Owing to its great specific heat, the water would 



