TRANSACTIONS OF SOCIETIES. 97 



Geological Society of South Africa. — Monday, June 30th: Mr. H. S. 

 Harger, Vice-President, in the chair. — "The Bushman's River creta- 

 ceous rocks " : Prof. E. H. L. Schwarz. The author recently examined 

 the Wood Beds (Lower Cretaceous) of the Bushman's River, where 

 Antliodon serrarius was discovered by Atherstone over fifty years ago. 

 The resuk of the examination was the discovery of a large bone, estimated 

 to have been quite rive feet long, which would give about twelve feet for 

 the length of the hind leg. At the base of the Wood Beds are brow*n 

 sandy beds, and above red marls, both containing great logs of petrified 

 wood, probably Araucarias, up to 18 in. diameter. Near Woodbury is the 

 alum cave whence the mineral bushmanite is obtained, the cave having 

 been formed by the weathering of the unconformity between the Witteberg 

 quartzites and the Enon conglomerate. As a natural occurrence the 

 chemical combination of this mineral, a magnesia-manganese alum, is 

 unique in the world. — " The geology of Katanga and Northern Rhodesia — • 

 an outline of the geology of South Central Africa"': F. E. Studt. The 

 author described (i) the sequence and general characteristics of the rock 

 systems of Katanga and Northern Rhodesia, and gave an ou'tline of the 

 tectonic geology of that portion of the African continent, covering an area 

 twice that of the British Tsles ; (2) He showed that the rock systems 

 recognised in South Africa cover the greater part of Equatorial and South 

 Central Africa, having similar lithological characters and geological 

 sequence; (3) He indicated the general distribution and relative age of the 

 large areas of subsidence which occur in Equatorial and South Central 

 Africa; and (4) lie summarised generally tlie conclusions arrived at. 

 Structurally he divided Equatorial and Southern .Africa into the follow- 

 ing regions: {a) the Couiio-Aii}iola-Kalahari Region, distinguished by the 

 presence, in almost undisturbed condition, of the Transvaal system and 

 the Waterberg System, and almost completely surrounded by rocks of the 

 Swazi system; (b) the Katanga-Rhodesia-Transi'aal Region, characterised 

 l)y the presence of the Transvaal and Waterberg forma,tions, very much 

 disturbed by granitic intrusion ; { c) the Cape Region a country of foldecL 

 and mountainous nature, covered I)y the apparent equivalents of the Trans- 

 vaal and Waterberg Systems: ( d) the Karroo Region, the large and high 

 plateau whose southern part was continously immersed in Ithe Karroo 

 Sea; (e) the East African Region — that part of the Continent east of Lake 

 Graben, from which the Transvaal and Waterberg formations are almost 

 entirely absent. The region is almost wholly granitic, schistose and vol- 

 canic, and is characterised by an extension of the subsidences, accompanied 

 by powerful volcanic activity, from the Katanga-Rhodesia Region; (f) 

 the Coastal Belts, narrow zones in which Cretaceous and Tertiary post- 

 Karroo deposits have been laid down. Incidentally, the author pointed out 

 the resemblance of the subsided areas, which extend apparently over 2,000 

 miles, from the Zambesi-Luangwa graben into Abyssinia, to the Martian 

 canals, and suggested that, if those canals really exist, these long subsi- 

 dences afford an explanation of them. 



Monday, September 8th : A. L.- Hall, B.A., F.G.S., President, in the 

 chair. — "The cassiterite lodes of Leeuwpoort; the paragenesis of the lode- 

 forming minerals " : D. P. McDonald. Cassiterite is very widely dis- 

 tributed throughout the area, but development has been concentrated on 

 live occurrences, and these were fully dealt with by the author, and the 

 minerals occurring in the lodes described. The ore bodies result almost 

 L-ntirely from the replacement of the quartzites by those minerals: these 

 replacements were each shortly discussed. Conclusions as to the order of 

 succession of the lode-forming minerals were stated, and the processes by 

 which the tin ore was mineralised from the granite of the Bushveld Com- 

 l)lex indicated. — " Notes on the tin deposits of Embabaan and Forbes Reef 

 in Swaziland " : A. L. Hall. The localities mentioned constitute the two 

 main tin-bearing districts of northern Swaziland. Practically the whole of 

 the tin recovered from the Embabaan workings occurs in the form of loose 

 crystals of cassiterite, no definite lodes in situ being visible. The source 

 of this cassiterite is undoubtedly the pegmatites belonging to the older 



