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the mean rise of temperature is i° F. for 253.9 feet vertical depth. His 

 purpose was to show that temperatures taken by means of drill-holes of 

 moderate depth, in stopes or development faces, are often far from the 

 original rock temperatures ; that hence the temperatures so obtained often 

 give rock temperature gradients that are far from the actual. The view 

 was also expressed — and reasons stating for holding it — that, unless refri- 

 gerating methods are used, one cannot hope to reduce the air temperature 

 gradient below the natural mean temperature gradient which the air has 

 due to compression, namely about 1° in 180 feet. 



Geological Society of South Africa. — Monday, April 20th : D. P. 

 McDonald, M.A., B.Sc, President, in the chair. — "Metasomatism in Ban- 

 ket " : Prof. R. B. Young. The author prefaced his more general 

 remarks by describing some particular imrecorded instances of replace- 

 ment at the Rose Deep, Paarl Central, and Machavie Gold jMines. The 

 classes of metasomatism in general were naturally arranged in two groups : 

 ( I ) those in which the replacement occurs sporadically at a great number 

 of isolated points within the rock, and (2) those in which the replacing 

 mineral tends to form a continuous body. The former includes replace- 

 ment of quartz by pyrite and other sulphides, as well as by gold and the 

 carbonaceous substance now represented in the banket by almost pure 

 carbon. The second group includes replacements of quartz by chlorite, 

 sericite, and calcite. In some of the cases of metasomatism, e.g., calciiica- 

 tion and chloritisation, the decomposition of basic dykes intersected in the 

 mines would afford an abundant supply of the replacing substances; while 

 the existence of open fissures descending to depths of several thousands of 

 feet, along which conspicuous solution has taken place, suggests the 

 descent, in quantity, of meteoric waters. — '' The geology of a portion of 

 the Beling7ve District of Southern Rhodesia" : Dr. P. A. Wagner. The 

 first part of the paper consisted of a description of the physiography of 

 the area dealt with, to which were added brief accounts of the drainage 

 and water supply, vegetation and archaeology. In referring more 

 exclusively to the geology of the district, the author gave special attention 

 to the rocks of the banded ironstone and greenstone schist groups, which 

 occur in narrow belts and patches, scattered like islands through a sea of 

 gneiss. The gneisses and granites were then described, the former under 

 the three heads of (i) foliated biotite gneiss. (2) mylonitic gneisses, and 

 (3) magmatic or composite hornblende-biotite gneiss. In the concluding 

 part of the paper a description is given of the great di'ke of Southern 

 Rhodesia, a vast intrusion which introduces a distinct element into the 

 landscape in the south-eastern portion of the region dealt with in the 

 paper, and also of the Um Vimeela dyke, running parallel to it at a dis- 

 tance of eight miles, and marked by a line of norite hills, along which 

 almost exclusively in the district the presence of fine examples of the Um 

 Vimeela tree (Kirkia acuminata) is to be observed. 



South African Institute of Electrical Engineers. — Thursday. 

 April 23rd: W. Elsdon-Dew, President, in the chair. — "Additional notes 

 on Electric furnaces' : Dr. W. Glucksman. The author referred to 

 developments in the application of electric furnaces since the date of his 

 ])revious paper (see this volume, p. 64), and mentioned particularly the 

 artilicial production of diamonds by Deboismenu, who had succeeded in 

 making a diamond weighing 2I carats. 



NEW BOOKS. 



Tilby, A. Wyatt. — The English people 07'erscas: Vol. I'f. — South 

 Africa, 1486-IQ13. Post 8vo. (S-l X S-V in.), pp. x, 632. London: 

 Constable & Co. 1914. 7s. 6d. 



Stevens, E. J. C White and Black : an inquiry into South Africa's 



greatest problem. i2mo., pp. vi, 284. London : Sinipkin, Mar- 

 shall. Hamilton, Kent & Co. IQ14. 12 oz. 2s. 6d. 



White, S. E. — .Ifricau camp fires. 8vo. pp. 415. Tllus. London: T. 

 Nelson & Sons. 1914. 30 oz. 5s. 



