TKANSACTIUXS OF SOCIETIES. 225 



two to twelve niillionths pQv cent., and a short discussion of the 

 factors which control the working of a mine at a profit. 



The ninth and tenth chajiters contain an account of the 

 secondary deposits, and tlie various questions raised by the 

 diamonds in these beds are fully discussed. 



In the last cha]Jter there is a list of the exi^tin^ diamond- 

 mining com])anies in the sub-continent, and tables of statistics 

 relating to diamond production. 



The numerous photograjjliic illustrations of exposures, rock- 

 sections, plant, etc.. are well chosen and ])rinted, as is also the 

 case with the maps and diagrams. 



TRAXSACTTOXS OF SOCIETTl-lS. 



South African Institution ov Knoinkrrs. — Saturday, I-'ehruary 141.I1: 

 Mr, \V. Calder, President, in the chair. — "Notes on Structures ": A. S. 

 Oatreicher. The author descrihed the method adopted by him in the 

 construction of a wooden roof of 100 ft. span, and 45 ft. from abutment 

 hinge to apex hinge, which had to be erected at comparatively short notice 

 in order to replace anotlier roof that had collapsed six weeks after com- 

 pletion. The roof designed by the author depended for its construction 

 entirely upon the carrying capacity of bolts, the roof being designed like 

 a steel structure with gussets, the bolts taking the place of rivets. 



Wednesday, March i8th : Mr. W. Calder, President, in the chair.-— 

 " The recovery of bye-products ; the plant required, and its location " : K, 

 Austin. The author referred primarily to the bye products obtainable in 

 the combustion of coal, and particularly in connection with the manufac- 

 ture of coke, the working of gas-producing plants, and the smelting of 

 iron in blast furnaces. The possibilities of recovering ammonium sulphate, 

 tar, and benzol on a prolitable scale were pointed out. 



( Kimberley Branch). — Thursday, March igth : Mr. J. Ilarbottle in 

 the chair. — "Concentration of diamondiferous ground, as applied to the 

 works of the De Beers Consolidated ^Tines, Limited " : J. Stewart. 

 A short account of the earlier methods of concentration was given, and 

 the present arrangements for workin.g the pulsators and grease tables 

 described in detail, 



Gkologicai. Socikty of South Afrka — Monday. Feljruary i6th : .\, L. 

 Hall, B,A,. F.G.S., President, in the chair.—" The Bushveld complex 

 as a metamorphic Province'" (Presidential address;: A. L. Hall. 

 A review of the more important results prf>duced by the intrusion 

 of the Bushveld Plutonic complex into the .surrounding sedimentary rocks. 

 The schistose rocks over the disturbed portion of the metamorphic pro- 

 vince are essentially due to thermal metamorphism, but possesses special 

 structural fentures arising from the-additional influence of intense pres- 

 sure. 



Monday, February 2.3rd: D, P. McDonald, M..A.. B.Sc. President, in 

 the chair. — " Notes on some prehistoric stone implements found in Ka- 

 tanga ■' : F. E. Studt. The implements were : an arrow-head of white 

 quartz : a " celt '' fashioned from the greyish wdiite granular q;-,ai-tzite of 

 the Kafubu Beds; an axe-head made from massive haematite ; two splie- 

 roidal stone hammers, one of quartzite and the other of ferruginous late- 

 rite ; two similarly but roughly shaped quartzite hammers ; and a " hole- 

 stone " of greyish brown sandstone. — "The granite dykes of tlie 3.520 ft. 

 level . Kimberley Mine " : Prof E. H. L. Schwarz. The paper opened 

 with ;t general historical account of granite dykes in South .'\frica, to 

 whicli was appended a resume of the recorded occurrences of the horn- 

 blende schists in the north-west of the Cape Province, and a discussion of 

 the irregular dykes, mostly of pegmatite type, which, together with the 

 schists, pass into the foliated rocks surrounding the masses of granite in 

 the area. The author proceeded to describe in detail the rocks of the 

 section on the 3,520 ft. level. 



