202 Transactions of the Royal Society of South Africa. 
The above description of the Foxdale granite would serve also as a general 
description of the granites occurring to the east and west of the Schapenberg. 
It would appear that the view — quoted above — as to the possible cause 
of the modification which gave rise to the G-rainsgill greissen is applicable 
to these rocks of the Schapenberg area. In support of which view I would 
emphasize the following comparisons :— 
(1) Both are most probably correctly considered to be apophyses of 
a fairly acid type of biotite granite. The trend of the tongue- 
like, eastern extension of the Kuil's River granite, and the 
coincident direction of the axis of the folding observed in the 
Malmesbury Series to the west of the Schapenberg are, I believe, 
facts in support of this view with regard to the latter area. 
(2) In the case of the Grainsgill greissen, magmatic differentiation 
and mechanical force are considered to be controlling factors. 
Evidence is not lacking that such have been effective in the 
Schapenberg area ; the existence of shear planes and the 
increasing acidity of the various rock-types described being 
considered as such. 
5. CONCLTJSIOlSrS. 
(1) The granite intrusion of the Schapenberg is a composite one. 
(2) That there were three well-defined periods at which intrusion of 
magma took place. 
(3) That these periods of intrusion are represented, respectively, by the 
different rock types described. 
(4) That the order of intrusion was as follows : — 
(a) Medium-grained porphyritic granite. 
(b) Fine-grained granite — or quartz-porphyry ; andalusite — bear- 
ing near its contact with the beds of the Malmesbury Series. 
It is questionable whether pneumatolytic action commenced 
to be effective during this period. 
(c) The greissen. This period was in all probability one of 
great mechanical disturbance affecting the whole area. 
Intrusion took place along shear planes. Pneumatolytic 
action became effective throughout the whole area — along 
the shear planes in the porphyritic granite, giving rise 
to the quartz -tourmaline veins ; along shear planes and 
throughout the quartz — or granite-porphyry — during this 
period. 
The veins of white quartz, also occurring along shear planes, may be 
similar to those described by Mr. Simmons in his paper on the granite 
mass of Foxdale.* They were j^robably the last rocks to be formed in the 
Schapenberg area, 
* Loc. cit. 
