﻿Vol. 66.~] METAMORPHISM ABOUND THE BOSS OE MULL GRANITE. 401 



pelitic gneiss only where these were approached or invaded by 

 the granite. On the other hand, kyanite, staurolite, and 

 tourmaline were found only along the outcrop of two particular 

 sets of beds, which were separated from the granite and the contact- 

 altered rocks by 2 miles of ordinary unaltered Moine rocks (mainly 

 pelitic gneiss), and in this pelitic gneiss none of the above-mentioned 

 minerals had been found. 



After thanking Dr. Teall for his kindly remarks, the Author said 

 that the reasons for correlating the Ross of Mull granite intrusion 

 with other granites, the later Palaeozoic age of which was established, 

 were : (1) its resemblance to them ; (2) it was conspicuously 

 later than the foliation of the Moine Gneisses ; (3) the absence of 

 shearing ; and (4) it was traversed by similar sheets of mica-trap. 



Referring to what Dr. Flett had said, the Author agreed that 

 the kyanite-tourm aline rocks might be due to recrystallization, 

 the extra heat being possibly derived from dynamic action or 

 from intrusive matter. At one of the localities in Mull much 

 pegmatite was associated with these minerals, but at the other 

 locality there was no conspicuous amount of it. Pegmatite was 

 commonly associated with these minerals in other districts. These 

 old pegmatite patches were intimately related to the gneisses, and 

 were often folded with them. There was every gradation from 

 knots of true pegmatite to the ordinary quartzo-felspathic streaks 

 which were present in the pelitic gneiss, and were frequently 

 sporadic in their distribution. The Author had, however, left it 

 for more experienced geologists to say whether these pegmatites 

 were genuine intrusions from an independent deep-seated magma, 

 or whether they were due to segregation during the regional 

 metamorphism. 



Pelspathization, such as Dr. Evans had mentioned, did occur 

 here. The peculiar rock, described as consisting of schist-material 

 with porphyritic felspars, etc., was of this nature. The quartz- 

 felspar granulites on the west side of Loch na Lathaich, near the 

 granite also enclosed comparatively large well-formed felspars, 

 which might be due either to recrystallization or to felspathization. 



