32 PRESIDENTIAL ADDRESS. — SECTION' II 



some further information, but everything may be summed up Dy 

 saying that at present the only investigations into the potentiahties 

 of the drugs and poisons latent in many South African plants come 

 as side issues to criminal proceedings against Kaffir " doctors " 

 who may happen to kill their " patients " by overdosing. This 

 is a most unsatisfactory method of dealing with a matter so worthy 

 of our serious attention. 



For our farming community there are scarcely two branches 

 of science so closely bound together by the possibilities of mutual 

 aid as chemistry and geology. Elsewhere I have striven to illus- 

 trate this mutual relationship as it affects the fertility of the 

 agricultural soils of the Cape Colony.* Geologicall3^ the coastal 

 belt consists of the sandstones and quartzites of the Table Mountain 

 and Witteberg series, below the former of which are the slates of 

 the Malmesbury beds. The soils of all these, according to many 

 chemical analyses made in the Cape Government Laboratories, 

 are very poor indeed, and the sandstone mountains yield acid soils 

 with a vegetation of rank sour grass. Intermediate between the 

 first two formations are the rocks of the Bokkeveld series, and 

 our analyses have shown their soils to be of far greater fertility. 

 The basin of the Karroo, deficient, unfortunately, in adequate 

 water supply- consists of the most fertile of soils as regards plant- 

 food, but the presence of alkaline salts may greatly hinder plant 

 production even where the water supply is ample. To the north- 

 west great bands of limestone traverse the JVlalmesbury slates and. 

 shales, and entirely change the character of the latter. A con- 

 siderable proportion of plant food is thereby imparted to the soil, 

 and, as the rainfall is scanty, the loose sands have retained all 

 their original elements of fertility, and are now just awaiting the 

 waters of irrigation in order to be turned into lands of remarkable 

 productiveness. These facts have been ascertained by chemical 

 analyses of the various soils referred to, but without the knowledge 

 derived from the studies of the geologist the chemist could not, 

 except with very much increased labour, be aware how far the 

 types of soil that he encounters in one particular locality would 

 be likely to extend unaltered. The time-saving nature of the 

 aid rendered to the agricultural chemist by previous geological 

 surveys is therefore patent. 



Something similar may be said in regard to the water supply. 

 Nearly two thousand analyses of water have been performed of 

 late years in the Cape Laboratories, and of these the analyses 

 of a number of deep-seated waters have been collated by me.t 

 The most important features noticed were that the waters of 

 the Table Mountain and Stormberg geological series are exceed- 

 ingly pure, that the most saline waters are those of the Uitenhage, 

 Dwyka and Bokkeveld formations, and that lime and magnesia 

 abound in the waters of the Karroo system ; those of the lower 

 Beaufort beds rarely containing sodium carbonate, which, howev^er, 



* " Fertility of some Colonial soils as influenced by Geological conditions," 

 Trans. S.A. Phil. Soc, Vol. i8, pp. 7-30. 



t " Underground waters of Cape Colon3^" Pres. Address to Cape Chem- 

 Soc, 1908. 



