Geological Society of London. 333 



some rare cases a foliation parallel to that of the schists traverses 

 granite-veins. It is generally, however, parallel at once to the 

 sides of the sill and to the foliation of the schists ; and many of 

 the structures are the remains of biotite-folia belonging to schists 

 whose quartzo-felspathic elements have been incorporated with 

 those of the granite. But many sills or veins, traversing the schists 

 at various angles, are foliated parallel to the line of junction, and so 

 discordantly to the structures in the schists ; and foliated granites 

 may even be observed to cut each other's foliation. These can 

 hardly be anything but original igneous structures ; but, if coexistent 

 with the last-named, would be indistinguishable from it. 



The country-rocks are various types of biotite-schist or gneiss, 

 with quartz-schists at Kildonan, and a scapolite-limestone at Arma- 

 dale. They are almost all holocrystalline, but it is certain that 

 sedimentary rocks enter into the complex. The whole series is 

 powerfully folded. 



The granites increase in size and numbers north-westward from 

 Kildonan, the intimate intrusive relations above described becoming 

 more highly developed in the same direction. The schists, at the 

 same time, become more and more highly crystalline, sillimanite 

 also appearing in them. About Kinbrace they are coarse sillimanite- 

 biotite-gneisses, with large striated felspars. 



Igneous contact is not held to be the sole origin of metamorphism, 

 though the cause which brought about the introduction of the granites 

 has evidently also produced these high types of crystallization. The 

 evidence of powerful movement which the schists everywhere present 

 suggests that such movement was the initial cause of the whole 

 series of phenomena. Movement recurred throughout, though all 

 cataclastic structures (if such existed) have been wholly effaced by 

 crystallization; introduction of granite being the final stage in the 

 production of the complex, and a high temperature (as shown by the 

 absence of chilled edges) being maintained to the very end. 



With regard to the granites, the authors find it difficult to believe 

 that they are wholly foreign matter, but remark that it is here 

 necessary to observe the utmost caution. 



2. " The Geology of the Eastern Corner of Anglesey." By E. 

 Greenly, Esq., F.G.S. 



The notes contained in this paper embody the principal results 

 obtained during a survey of Anglesey on the six-inch scale. 



The schists of the south-east of the island are succeeded uncon- 

 formably by the slates of Careg Onnan, winch appear to be separated 

 by a strong unconformity from the Ordovician shales. The Careg 

 Onnan slates appear (pending confirmation from other sections or 

 direct fossil evidence) to be of pre-Cambrian age, and the author 

 records the existence of sponge-spicules therein. 



The ashy grits and bedded tuffs of Baron Hill, near Beaumaris, 

 appear to have been moved somewhat from the ENE. along a thrust- 

 plane. They are traversed by planes of unionization, and are much 

 broken and folded. 



The Ordovician rocks consist chiefly of sparingly fossiliferous dark 



