We found the north-east end composed of a fine-grained granite[19]; the middle of the island of a brittle micaceous schistus of a deep blue colour[20]; the strata are nearly horizontal, but dip a little to the south-west. This body of strata is cut across by a granite dyke[21], at some places forty feet wide, at others not above ten; the strata in the vicinity of the dyke are broken and bent in a remarkable manner: this dislocation and contortion does not extend far from the walls of the dyke, though veins of granite branch out from it to a great distance, varying in width from three feet to the hundredth part of an inch: the dyke is visible from the top of the cliff to the water's edge, but does not re-appear on the corresponding cliff of an island opposite to it, though distant only thirty yards. This island is composed of the same schistus, and is cut in a vertical direction by a whin dyke[22], four feet wide, the planes of whose sides lie north-east and south-west, being at right angles to those of the great granite dyke in the neighbourhood, which run south-east and north-west. The strata contiguous to the whin dyke are a good deal twisted and broken, but not in the same degree as at their contact with the granite dyke. The whin dyke is formed of five layers or sets of prisms laid across in the usual way. Beyond the small island cut by the whin dyke, at the distance of only forty or fifty feet, we came to an island rising abruptly out of the sea, and presenting a high rugged cliff of breccia[23], fronting that on which the granite dyke is so conspicuous: the junction of this rock with the schistus cut by the granite and the whin would have been interesting; but although we must have been at times within a few yards of it, the actual contact was every where hid by the sea. The whole of the south-west end of this island is formed of breccia, being an assemblage of angular and water-worn pieces of schistus, quartz, and some other rocks, the whole having the appearance of a great shingle beach and cliffs. The fragments of the schistus in this rock are similar to that which forms the cliff first spoken of. (Specimen 8.)