64 PEESIDEXTIAL ADDRESS SECTIOX C. 



that action pending- inquiries, I urg-e meantime rapid progress 

 with tlie work of the liotanieal Survey as one of the proofs which 

 sooner or later will again be, demanded to show the stability or 

 instability alike of the flora and of the climate. 



Meantime, let the destructive agencies be checked or 

 controlled in accordance with scientific reasoning and with 

 common sense. 



REFEREXCES CITED. 



Aectowski, H. (1915) — 



A study of the influence of volcanic dust-veils on climatic 

 variations. — Sci., 41, 252. 

 BOLrS AND WOLLEY-DOD (1903) — 



S.A. Philos. Soc, Trans., xiv, 3. 

 Clements, F. E. (1916)— 



Plant Succession. — Carnegie Inst., "Washington. 

 Douglas, A. E. (1914)— 



A method of estimating rainfall bv the growth of trees. 

 In Huntington's " The Climatic Factor."— 

 Carnegie Inst., Wash. Pub. 192. 101. 

 HrxTixGTOx. E. (1914)— 



The climatic factor, as illustrated in arid America. — 

 Carnegie Inst., Wash. Pub. 192. 

 Sim, T. R. (1920)— 



Soil erosion and conservation. — Industries Bulletin. 

 Series. Bulletin '^o. 47. 



SOME ZOOLOGICAL FACTORS IX THE ECONOMIC 

 DEYELOPMEXT OF SOUTH AFRICA. 



By C. W. Mally, M.Sc, F.E.S. 



With Plate XXIX. 



Presidential Address to Seetion D, delicered July 14, 1920. 



In beginning the work of the Section over Avhicli I have 

 the honour to preside on this occasion, it seems advisable to 

 call for suggestions for the good of the Section. The 

 programme which we have before us will afford opportunities 

 to discuss subjects on which the authors of the papers have 

 done original work. There may be members or visitors who 

 would like to get information concerning some subject not on 

 the programme or to offer suggestions for the benefit of the 

 organisation of the work of the Section in future. To afford 

 opportunity for inquiries and suggestions, I beg leave to 

 propose that when all the special papers have been dealt with, 

 any available time be devoted to a "Symposium'" on any 

 subjects that may be brought forward. My purpose in making 



