274 THE BUTTERMERE AND ENNERDALE GRANOPHYRE. [May I906, 



reasonably be expected that the contact-metamorphic effects pro- 

 duced by it would also be of an intermediate character, and he 

 suggested that a comparison of the three cases might perhaps 

 afford evidence confirming the Author's views. 



Mr. J. V. Elsden drew attention to the fact that the Author's 

 interesting conclusions with regard to the influence of pressure 

 upon the formation of a granophyric structure seemed to be opposed 

 to those of Prof. Yogt, who, after an exhaustive study of analyses by 

 Lagorio and others, had strongly expressed the opinion that even 

 considerable differences in the depth at which consolidation takes 

 place can have very little effect upon the eutectic composition. 

 With regard to the occurrence of micropegmatite in the interior 

 portion of the mass, this was what would be expected of the product 

 of the final consolidation of the mother-liquor. The rule, however, 

 did not appear to be universal, for an instance had come before the 

 speaker's notice, in the enstatite-diorite of Carnedd Lleithr, near 

 St. David's, in which the only pronounced micropegmatite seemed 

 to occur quite on the extreme margin of the intrusion. 



Prof. Watts expressed his regret at the Author's absence and 

 the cause of it. He remarked that Mr. Eearti3ides was more or less 

 responsible for the singularly-perfect photographs shown on the 

 screen, which enabled hearers to follow with ease the necessarily 

 somewhat technical descriptions embodied in the paper. Dr. Teall 

 had been the first in Britain to direct attention to the part played 

 by eutectics in rock-magmas, and had tabulated analyses of 

 numerous micropegmatites showing that they had a practically- 

 uniform composition. His conclusions had been driven home by all 

 the most recent work on the crystallization of alloys. 



Mr. W. G. Eearnsides, in the absence of the Author and in reply 

 to Dr. Cullis, explained that the question of the metamorphism 

 produced by the granophyre was still sub judice and was being 

 worked at by the Author. He commented upon the enormous 

 extent of country which must be covered in the course of such 

 an investigation ; but thought that, so far as the Author had gone, 

 the metamorphism was certainly found to be of a type intermediate 

 between that around the Threlkeld Microgranite and that of the 

 Skiddaw-Granite aureole. As a further example of a tonalitic 

 granophyre, in which the centre of the mass was finer-grained and 

 more definitely and more minutely micropegmatitic than the 

 margin, he would mention the rock-mass which was variously 

 known as the Tan-y-grisiau Syenite and the Ffestiniog Granite : 

 this is intrusive into the slates and flags which immediately 

 underlie the Ordovician Volcanic Series of Nor tlr Wales. In this 

 mass also there is a tendency, for certain parts of the marginal 

 granitic or granulitic portion, to lose its felspar and pass into a sort 

 of secondary greisen. 



