448 Geological Society : — 



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 silliman- 

 ite-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 gra- 

 nites 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 un con- 

 formably by the slates of Careg Onnan, which appear to be 

 separated by a strong unconfoimity 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 

 ths 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 E.N.E. along a 

 thrust-plane. They are traversed by planes of my Ionization, and 

 are much broken and folded. 



The Ordovician rocks consist chiefly of sparingly fossiliferous dark 

 shales and mudstones, but contain a group of volcanic tuffs on the 

 horizon of the pisolitic ironstone. 



The Carboniferous rocks appear to be about 700 feet thick, and 

 contain conglomerates, sandstones, and shales, with plant-remains 

 about the middle of the series. 



