THE 



SOUTH AFRICAN JOURNAL 

 OF SCIENCE: 



COMPRISING THE REPORT OF THE 



SOUTH AFRICAN ASSOCIATION 



FOR THE 



ADVANCEMENT OF SCIENCE. 



1919. 



KINGWILLIAMSTOWN. 



OFFICERS : ^919-1920. 



PRESIDENT. 

 I. B. Pole Evans, M.A., D.Sc, F.L.S. 



VICE-PRESIDENTS. 

 Prof. J. W. Bews, M.A., D.Sc. Prof. R. Leslie, M.A F S S 



Prof. J. E. DuERDEN. M.Sc-, Ph.D., A.R.C.S. Prcf. J. A. Wilkinson, M.A., F.C.S. 



HON. GENERAL SECRETARIES. 

 J. A. FooTE, F.G.S.. F.E.I.S., Commercial High School, Johannesburg, 

 C. F. JuRiTz, M.A., D.Sc, F.I.C., Agricultural Chemical Research Laboratory, Cape- 

 town. 



HON. GENERAL TREASURER. 

 Prof. C. E. Moss, M.A., D.Sc, F.L.S., F.R.G.S., South African School of Mines amd 



Technology, Johannesburg. 



ASSISTANT GENERAL SECRETARY. 

 M. K. Carpenter, P.O. Box 6894, Johannesburg. (Telegraphic Address : "Scienc«.") 



EDITOR OF JOURNAL. 



Prof. H. B. Fantham, M.A.. D.Sc, South African School of Mines, 



P.O. Box 1 176, Johannesburg. 



^OLXVL APRIL-JULY, 1920. NO. 5. 



JOHANNESBURG. 

 PUBLISHED BY THE ASSOCIATION. 



1920. [Price Bs. 



