100 GEOLOGY OF THE WITWATEESEANB, ETC. [Feb. 1898, 



tions guide the prospector in searching for the outcrop of the beds. 

 Is their existence indicated by quartz-r-bbles on the surface, or by 

 ferruginous outcrops, or what? In conclusion, he complained of 

 the use by the Author of the expression ' mineralization of the 

 conglomerate : ' he wished in season and out of season to protest 

 aga?nst this use of the word ' mineralization.' He quite understood 

 that the Author meant by ' mineralization ' the deposition of iron- 

 pyrites and silica in the mterstices between the pebbles ; but this 

 implies that the conglonierate was not mineral matter beforehand. 



llr. W. H. Meeeitt thought the term ' mineralization,' in the 

 sense objected to by the previous speaker, was in more common use 

 on the North American continent than on this side of the Atlantic. 

 He, however, suggested ' metallization ' as a more correct term. He 

 congratulated the Author on his paper, and said that what he thought 

 of special interest was the mode of occurrence of the gold in these 

 conglomerates. He said that this showed that auriferous solutions 

 ma^j occur in a very unexpected manner, and in very unexpected 

 places ; and in confirmation of this he alluded to a locality m 

 British Columbia, where gold occurred and was worked in deposits 

 of cupriferous pyrrhotite containing virtually no free quartz and 

 occurring chieflv in gabbro. 



The Rev. J. F. Blake and Dr. J. W. Geegoet also spoke. 

 The AuTHOE, replying to the President, admitted that in describing 

 the ancient crystalline rocks he had used the term ' Primary ' 

 indiscriminately with ' Archaean.' He agreed that it would perhaps 

 be better to discard the former, and to use the latter term m 

 preference. With regard to the age of the Cape Formation, he had 

 pointed out in the paper that the Witwatersrand Beds were probably 

 correctly correlated with the Table Mountain Sandstone, and that 

 the latter was underlain by the Bokkeveld Shales, in which cha- 

 racteristic Palgeozoic (Devonian) fossils had been found. 



Replying to Prof. Le Xeve Foster, he instanced the Nigel Mine 

 as one that had been opened up in payable ore on the southern side 

 of the synclinal. There was nothing to indicate which of the 

 conglomerate-beds might carry gold, short of taking samples for 

 panning or assay. He saw no objection to the use of the word 

 ' mineralization^' to indicate a secondary impregnation with mineral 



matter. . 



He was glad to find that Dr. Gregory confirmed him m the idea 

 that the Dwyka Conglomerate was a volcanic breccia, and conse- 

 quently iDdicative of volcanic activity. 



