I n the following notes I propose to lay before the Society the results of a microscopical examination of certain metamorphic rocks surrounding the Land's-End granite. In doing so my principal object will be to point out the structural and mineralogical changes produced in clay-slates and certain igneous rocks by the intrusion of a mass of granite, and also to compare the phenomena of contact-metamorphism with those produced by other agencies in rocks of similar character at a distance from the granite. On referring to the map of the Geological Survey of Cornwall, it will be seen that in the vicinity of Penzance the granite is surrounded by a belt of altered Devonian slates extending from St. Ive's Bay on the north coast to a point a little beyond Mount's Bay on the south; they also occur along the coast north-east of Cape Cornwall, and reappear in the same direction at Porthmear Cove and near Zennor. The so-called greenstones occur in four distinct groups, also round the outskirts of the same mass of granite, vizaround Penzance and in the other localities just mentioned. In all cases they are represented as occurring in the altered slates either at a short distance from the granite or in actual contact with it. A microscopical examination of both these groups shows at once that they have all been highly metamorphosed, and that the alteration varies greatly in character and extent according to the nature of the rock and its distance from the granite. The change