AND ASSOCIATED ROCKS OF THE SOUTHEEN^ TEANSVAAL. 435 



(c) The subsequent outpouring of igneous rocks has been enormous. 

 This extrusion was certainly later in date than the deposition of 

 the conglomerate series, and may possibly be posterior to that at 

 which the faulting and crumpling of the strata took place. 



{d) The apparent base of the sedimentary series, where seen (as 

 at Yredefort), clearly overlies granites, gneisses, and gabbros ; but 

 the sedimentary beds dip towards the crystalline rocks, often at high 

 angles. 



{e) Most of the conglomerates are more or less auriferous, though 

 there are notable exceptions. 



(/) The coal-bearing strata overlying the Witwatersrandt series 

 rest unconf ormably upon the eroded edges of all the beds below, and 

 are the newest stratified rocks of the district. 



[The present paper deals essentially with the facts bearing upon the strati- 

 graphy of the Southern Transvaal. It was the Author's intention in a second 

 paper to give a detailed account of the lithology of the gold-bearing conglo- 

 merates, and to describe in this connexion various microscopic slides which he 

 had caused to be prepared, and also to discuss the mode in which the gold occurs 

 and the question of its origin. Before, however, he was able to complete this 

 part of his work, Mr, Gibson had to leave England for Equatorial East Africa. 

 His second paper is therefore necessarily deferred.] 



EXPLANATION OF THE PLATES. 



Plate X. 



Diagram-sections across the Gold-bearing beds of the Southern Transvaal. 



Plate XI. 

 Geological Sketch-map of the "Wit water srandt Gold-fields. 



DlSCITSSlOlS^. 



The President hoped that many papers similar to that just read 

 would be offered to the Society, now that so many of its members 

 were scattered over the world. Dr. Exton, who had sent specimens 

 which were exhibited on the table, had noted the difficulty of 

 accounting for the gold in the conglomerates. He (the President) 

 had not exactly understood, from the reading of the paper, how the 

 Author accounted for the mode of occurrence of this gold, further 

 than that it was derived from the auriferous quartz-veins in the 

 gneissose rocks, and he would be glad to hear the views of those 

 who had made a special study of the distribution of gold. 



Prof. Green pointed out the difficulty, in the present state of our 

 knowledge, of correlating the beds described in the paper with the 

 beds older than the coal-bearing rocks of Cape Colony. He thought 

 that the intrusive masses of dolerite might belong to the same com- 

 plex of dykes and sheets which form so marked a feature in the 

 country to the south. He hazarded the opinion that the conglome- 

 rates were old alluvial gold-bearing deposits, and maintained that 

 the mode in which the gold occurred was compatible with this view. 



Mr. Attwood said he had not visited the Witwatersrandt gold 

 district, so he found it a difficult matter to say much about the 



