PALAKOLITIIIC I.M1M,KM KXTS. 23,5 



It appears that the bkck vlei soil, the method of 

 formation of whicli has l)eeii described by Mr. Maufe, has 

 aecumidated since tlie formation of the older palaeolithic 

 implements, and is now nndero'oino' removal. 



EXPLANATION OF PLATP: XXX. 



8tOXE iMrLEMKM'S FKOM THE IJmGUZA AND ]^EM]$ESI VaLLEYS. 



(About one-sixth natinal size.) 



Fig. 1. — Pointed Chellean type, with unshari)ened butt, 

 Powola. 



Fio's. 2, '), 6. — Pointed Acheulian implements, Tegwan. 



Fig. 4 a (and b). — Two sides of same implements, showing 

 surface (4/>) detached from parent rock, n])per portion of 

 Imbusine. 



Figs. 5 and T. — Acdieiilian implements. Fmguza. 



Fig. 8.^ — Implement from upper part of Imbusine. 



Figs. 9, 10, 11. — Ovate implements, Imbusine. 



Figs. 12, 13. — " Cleavers," ovate implements unfinished, 

 Macheni. 



THE EFFECT OF ELEVATIOX OF TEMI'ERATURE 

 AND ALTITUDE OF AERODROME IX THE TAKIXO 

 OFF OF AEROPLANES. 



By P. G. GuNDRY, B.Sc, Ph.D., F.R.Ae.vS., 



Professor of FJiijslcs, Transvaal Universifij College, Pretoria. 



Read Juhi 15, 1920. 



Introduction. 



The Cairo-Cape flights of the present year brought into 

 prominence many peculiarities of conditions arising- from the 

 high temperature combined Avitli high altitude of the aero- 

 dromes on the route. The conditions were for the most part 

 new, for flight from elevated aerodromes in Europe and the 

 United States has been made as a rule in temperate climates, 

 where the temperature at such altitude was low. The^se 

 peculiarities, which led to great difficulties for tlie pilots, 

 may be divided into two classes : — 



(1) Engine peculiarities, especially defects of carburation 

 and unequal heating of the cylinder jackets owing 

 to the higli temperature of the air. 



