RUBIDGE — SOUTH-ArniCAy EOCKS. 
55 
subject is still somewhat defective ; I will defer what I have to say on 
this subject till a future period. 
I have had but little time or opportunity for the microscopical 
studies which have done so much for the views on the nature and 
origin of granite which I am here advocating. I should hardly have 
ventured indeed to have given observations so crude as my own, but 
for a conviction that probably no country in the world offers greater 
facilities for studies of this kind than does this Colony, and more 
especially the district of Namaqualand, which is probably barer of 
vegetation and more intersected by gullies than any other country in 
the world not absolutely uninhabitable. 
I will give a hrie^ resume of the observations which led me first to 
doubt and at length to abandon the igneous theory of granite, in 
which I was a firm believer ere I visited the Western Province of the 
Colony. 
1. The undoubted change which rocks have undergone into quartz- 
ite and its equally evident origin in superficial and igneous agency. 
Mr. Darwin admits this origin of the Table Mountain sandstone. 
2. The existence of beds of granite and other rocks of felspathic 
bases in association with sedimentary rocks in positions which it is 
impossible to believe they could have occupied by forcible intrusion 
from below. Many veins of the claystone-porphyry exceed a thousand 
yards in width, yet they do not in the slightest degree disturb the 
strata adjacent to them. At Kleinpoort I measured the slate eighteen 
inches from its junction with the porphyry. It dipped towards the 
latter at an angle of 35°, the porphyry itself having a dip in the 
same direction. 
3. Tlie irregular masses of granite taking the place of gneiss and 
not connected with the granite below. 
4. The origin of prehnite and other zeolitic minerals from decom- 
position of igueous dykes of the Dicynodon-strata. Prehnite, as 
well as of quartz, is formed thus between the decomposing " boul- 
ders " of igneous rocks. Veins of carbonate of lime are often formed 
in the same way. Nor can I hesitate to refer the felspathic veins 
and irregular masses in decomposing gneiss in Namaqualand to a 
like process of re-arrangement. I have there seen carbonate of lime 
in felspathic rocks ; fluor-spar mixed with epidote and felspar ; phos- 
phate of lime with felspar and quartz. 
5. I have mentioned the igneous dykes of the Dicynodon-strata. 
They have always been referred to plutonic agency, but it appears to 
me that there are great difiiculties in admitting such origin. They 
take, I believe, every direction of the compass, vary from eighteen 
inches to some hundreds, perhaps thousands, of yards in breadth, and 
some of them are probably fifty or more miles in length ; they are 
numerous, and occur frequently from near Somerset East to the Vool 
E/iver, but never, in my experience, or that of any one I know, pass 
the boundary of the Dicynodon-strata, nor do they disturb the rocks 
through which they cut in the base. 
6. I have mentioned the occurrence of granite-veins conformable 
