THE 



SOUTH AFRICAN JOURNAL 

 OF SCIENCE; 



COMPRISING THE REPORT Oi'^ THE 



SOUTH AFRICAN ASSOCIATION 



FOR THE 



ADVANCEMENT OF SCIENCE. 



1919. 



RINGWILLIAMSTOWN. 



OFFICERS : 1919-1920. 



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. Prof. 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 and 



Technology, Johannesburg. 



ASSISTANT GENERAL SECRETARY. 



M. K. Carpemter. P.O. Box 6894, Johannesburg. (Telegraphic Address : "Science.") 



EDITOR OF JOURNAL. 



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



P.O. Box 1176, Johannesburg. 



VOL. XVI. JAN.-MARCH, 1920. NO. 4. 



JOHANNESBURG. 

 PUBLISHED BY THE ASSOCIATION. 



1920 [Ppiee 6s. 



