54 TRANSACTIONS OF SOCIETIES. 



chemical analysis proved the presence of 45 per cent, of iridium in the 

 Osmiridium found in the concentrate. The author concludes the metals to 

 be of secondary origin, occurring as primary segregations formed by mag- 

 matic concentration in the basic eruptives occurring in the mines : and 

 that by the last phase of eruptive activity they were extracted from the 

 dykes by superheated gases. Subsequent hydrothermal action probably 

 operated in concentrating them in the banket reefs. 



Monday. June 17: Mr. H. S. Harger, President, in the chair. — " Topo- 

 graphy and Geology of the German South Kalahari " : Dr. P. Range. 

 The county described consists of an uninhabited northern portion and an 

 inhabited southern portion, bordering on Gordonia and Bechuanaland. The 

 entire country is an immense plain, and the author's object in his journey 

 was t<> discover the nature of the older rocks hidden under the 

 prevailing surface deposits. Those rocks belong to the Nama and 

 Karroo formations, almost completely covered by a deposit termed '"Kala- 

 hari limestone," but really a calcareous sandstone, on top of which lie the 

 reddish Kalahari sands, the layer of sand averaging about 15 feet in thick- 

 ness. Below the upper strata, the author is convinced, an extensive under- 

 ground water supply exists, and doubtless the country, as well as the 

 adjacent parts of Gordonia and Bechuanaland, formerly misnamed "desert," 

 will yet become the home of a large number of well-to-do farmers. — 

 '"Notes on a specimen containing Bastnasite and Wolframite from Wel- 

 gevonden : " D. P. McDonald. Bastnasite, a fluo-carbonate of the cerium 

 metals, has been found fairly widely distributed in the vicinity mentioned. It 

 is associated with wolframite, and also with tourmaline, in which the larger 

 crystals are embedded. It is also found together with orthite, a? was 

 the case where it was first described, in Sweden. The wolframite i- of 

 relatively late origin, formed by the alteration of scheelite and associated 

 with calcite. The deposit, the author concludes, is of pneumatolvtic 

 origin. — "Xote on the relationship between the Black Reef Formation and 

 the Ventersdorp diabase " : C. B. Horwood. At Randfontein, 27 miles 

 uest of Johannesburg, the author has found Ventersdorp diabase intrusive 

 in the Black Reef Formation. Through the typical bluish-black quartzite 

 of the latter formation tongues of diabase have forced their way, and two 

 or three feet of shaly diabase may be seen overlying this quartzite. and 

 Underlying some eight inches of the quartzite which has been bleached 

 white and rendered fissile. Xear Robinson Station the diabase had broken 

 right through the quartzite and poured over its surface. In other localities 

 it may also be seen overlying the Black Reef conglomerate. Apparently, 

 therefore, the eruptive activity of the Ventersdorp period did not entirely 

 die out during the time that the Ventersdorp System was being laid down, 

 but extended into that period to which the Black Reef Series belongs. 



South African [nstitute of Electrical Engineers. — Thursday, May 

 23rd: J. H. Rider. V.P.I. E.F., President, in the chair.— "The design and 

 installation of transformers from an operating point of view" : C. W. R. 

 Campbell. Dealing principally with three-phase transformers, practical 

 observations were made with regard to their, designing, transport and 

 installation. Every transformer of any importance should be fitted with 

 a thermometer pocket and a thermometer, of which constant readings 

 should supersede the practice of judging the temperature by hand. 



