Minutes of Proceedings. 
iii 
that site as a source of lapilli during Witteberg times, he would have to 
prove the contemporaneity of the vulcanism and its continuance through 
Karroo times, for the Zuurberg fissure was certainly of post-Dwyka date, 
probably post-Uitenhage. The crumpling of the Witteberg strata near 
Eooi Kop could hardly be attributed to contemporaneous volcanic 
activity; such crumpling, also, is unknown from the neighbourhood of 
the Drakensberg and later volcanoes in Cape Colony. The speaker 
deprecated the revival of a volcanic theory of the Dwyka Series without 
good evidence. 
Dr. C. F. JuRiTz thought it probable that some of the curious reac- 
tions described in connection with the processes whereby platinum was 
said to have been extracted from the rocks of the Albany district, and 
attributed to the presence of metals hitherto unknown to science, would 
eventually be found to have very simple explanations. For instance, a 
greenish-black precipitate, which turned greyish- white, most likely 
resulted from nothing more than iron, the change of colour being due to 
the gradual deposition of free sulphur. A white precipitate, also put down 
to some new metal, was apparently only silver chloride derived from the 
silver dish prescribed in the process for the preliminary fusion of the rock, 
and the fact that this silver chloride would not dissolve in the usual 
solvents of that substance seemed to be due entirely to its having been 
exposed to light. Another hypothetical metal had been associated with 
the pink colour said to be developed at some stages of the process ; now 
he had heard that under certain conditions also a green colour was pro- 
duced, and it looked as though these were caused simply by manganese. 
The mineral Bushmanite (Dana's System," 6th ed., p. 955) — a manga- 
nese alum — occurred abundantly along the banks of, and, in fact, derived 
its name from, Bushman's Eiver, which fiowed through the very area 
supposed to be platiniferous. He considered it unfortunate that, where 
the stupendous assay results of hundreds of ounces of platinum per ton of 
rock had been reported, there had always seemed to be a link missing in 
the chain of evidence connecting the assay with the site ; and, on the 
other hand, where the chain w^as complete the proportions of platinum 
found were quite infinitesimal. Much had therefore to be taken on trust, 
and to constitute an acknowledged scientific fact more than this was 
needed. The attitude of chemists was consequently not one of enthusiasm 
regarding the future of the reported discoveries ; they were still waiting 
to be convinced. 
Dr. G. CoRSTOEPHiNE pointed out that the angularity of the quartz 
splinters in a rock was no evidence of its volcanic origin ; such sharp 
fragments were of common occurrence in rocks which contain small 
fragments. It is a usual experience to find the larger grains sub-angular 
or rounded and the smaller angular in ordinary sedimentary rocks. He 
