TRANSACTIONS OF SOCIKTTES. 789 



iHCiii of rorrosivc cooling water": W. O. Andrews Two cases of the 

 corrosion of metals by faintly acid cooling- water were discussed : one of 

 these was successfully treated by means of quicklime, and the other by 

 air-separated lime. Where the composition can be controlled it is desir- 

 able to make the water truly neutral. Neutral point indicators, such as 

 methyl red, rosolic acid, and litmus are necessary, but methyl orange and 

 phenolphthalein are unsuitable. 



South African Institute of Electrical Engineers. — Thursday, 

 December 19th: Prof. J. H. Dobson, D.S.O., M.Sc. M.Eng., M.I.xMech.B:., 

 ]\1.I.E.E., A Al.LC.E., President, in the chair. — "Illumination and some 

 of its fundamental considerations " : H. A. Tinson A discussion of 

 illumination problems, and some of the considerations governing their 

 solution. 



Thursday, March 2)oth : R. F. Botting, A.M.I.E.E., Vice-President, in 

 the chair. — "Notes on the application of synchronous condensers to large 

 power systems " : G. V. AdendorfF. The author discussed the practical 

 advantages which result from the use 01 rotary condensers on any large 

 system of power transmission. 



Thursday, May 15th : A. E. du Pasquier, M.I.E.E., President, in the 

 chair. — "Notes on the electrical equipment at t.iC circular shaft. New 

 Modderfontein Gold Mining Co., Ltd.": R. H. Copeland. A description of 

 one of the largest electrical equipments on the Witwatersrand, recently 

 installed, the power being supplied by the Rand Mines Power Supply Co., 

 Ltd. 



Thursday, June loth : A. E. du Pasquier, M.I.E.E., President, in the 

 chair. — Presidential Address: A. E. Du Pasquier. The address dealt 

 with the essential importance of British oversea trade ; the difficulties of 

 expanding it, or even of retaining it under present labour conditions ; the 

 importance of coal as the principal factor in commercial supremacy, and 

 the necessity for conserving existing reserves. 



Chemical, Metallukgical, and Mining Society of South Africa. — 

 Saturday, February 15th : H. S. Meyer, A.R.S.M., President, in the chair. 

 — "Ancient tin mines of the Transvaal" : M. Baumann. The workings 

 described are situated in the Rooiberg-Leeuwpoort area, in the Waterberg 

 District, about 40 miles west of the Pretoria-Pietersburg Railwaiy. 

 .iiardly a lode of any importance in the vicinity has been worked in 

 iriodern times on which the ancients have not been down in one or more 

 places. Where, in the course of their prospecting, the ancients came upon 

 rich ore, they followed it down until beaten by water, or the rock 

 became too hard. Where ore occurred in pockets, flats, or pipes, it was 

 followed and taken out with astonishing cleanness. The ore was broken 

 away with hammers and gads, specimens of the former found ))eing of 

 mild steel of exceptional purity. The principal smelting centre appears 

 to have been an outlier of the Elandsberg Range, known as Smelters Kop, 

 but remains of slag and broken nozzles have been found in several other 

 localities. A careful estimate shows that 18,000 tons of ore were taken 

 from the Rooiberg area alone, and about 6o,coo,coo lbs. of bronze must 

 have been produced. The author concludes that the mining, though some 

 of it is recent, must have extended over a very much longer period than 

 1. 000 years. — " Tlic application of the theory of probability in the deter- 

 mination of ore reserves": G. A. Watermeyer. It has been the custom 

 to determine ore reserves by the individual valuation of each block of ore, 

 based on samples taken at uniform intervals, or otherwise on the peri- 

 meter of the block where accessible. The assay results are reduced to 

 graphs and averages taken according to definite system. The author 

 proceeded to discuss simple applications of the theory of probability, and 

 then, taking a given value occurring over a width as abscissa, and the 

 frequency of occurrence as ordinate, curves can be deduced by the com- 

 pound Gaussian Law based upon sample sections taken during some agreed 

 period. 



Saturday, Marcli isth: H. S. Meyer. .K.R.S.M.. President, in the chair- 

 —"■Chemical Ewiiucrring" : Prof. I. A. Wilkinson The author 

 emphasised the fact that the experiences., .«)f tlic last tour years have 



