Cadgwith. A lofty and finely indented cliff was prolonged to the west, and continued almost inaccessible, until it was cut through by a deep ravine, which terminated in a small sheltered cove close to the village of Cadgwith. Some time before we reached the village, the serpentine had disappeared, and was succeeded by well defined beds of green-stone slate; which had a slight inclination to the north. As this slate re-appeared in the same position on the western side of the ravine; we should, in any other place, have concluded that the chasm had been formed by a vertical excavation in a continuous schistose mass. But our acquaintance with the district led us to form a contrary opinion. A further examination of the ravine afforded the most convincing evidence, that the whole opening had once been filled with serpentine, of which a few crumbling blocks were still to be seen in situ above the village. After we had crossed the high cliff on the western side of the cove, we descended into a magnificent natural amphitheatre; formed by the decomposition of an irregular mass of serpentine, which had again intruded on the green-stone. During high water, the sea rushes into the lower part of this amphitheatre; and at the same time undermines its walls and carries off the ruins, which are continually falling down from the decomposing face of a rock nearly two hundred feet high. Above that portion of the cliff, where the sea has forced a passage into the chasm, a hard mass of serpentine stretches right athwart the gulf, and affords a natural bridge, by which we passed over to the west. For nearly two miles we advanced along a high terrace, bounded towards the sea by a cliff which was precipitous and unbroken, except in two or three places where the green-stone was interrupted by serpentine. The alternations were marked by the usual appearances of decomposition. We afterwards descended to the beach by a road recently excavated in some rocks which seemed to belong to the green-stone formation. One part of them contained much resplendent diallage; another part was composed almost exclusively of fine granular felspar; and we were surprised to find associated with them, some masses into which granular quartz entered as a constituent. Alternations, such as I have before described, are continued Balk Head. as far as Balk Head, which is the last locality of the serpentine on the eastern side of the Lizard promontory. Before we reached that headland we met with an alluvial cap, containing much siliceous sand, and some quartz crystals with double terminations. We were informed that it had been used successfully as a top dressing for the land. At the immediate termination of the serpentine, the whole strand was covered with prismatic blocks, derived from the crumbling cliff, which generally exhibited a dull fracture, and a decomposing texture. This decomposition often penetrated deep into the substance, even of those masses where the rugged angular forms continued very little altered; a circumstance which would make it necessary to exercise great caution in the selection of such materials for the purposes of ornamental architecture. Large sound blocks, possessing extraordinary beauty, from the admixture of greenish black and bright red colours, might, however, be extracted from the cliff; if the public taste offered sufficient encouragement for the undertaking. On a review of the phenomena we had hitherto observed on Recapitulathe south side of the Helford river, we were led to conclude, that tion, &c. the great plateau of the Lizard was not composed of stratified rocks. We have, indeed, pointed out some obscure indications of an order of superposition near Coverack and Porthalla. But they are too uncertain to be opposed to the clear evidence offered in the southeastern parts of the coast; where the alternating masses of greenstone and serpentine so often appear, like great wedges driven side by side into the escarpment, without any order of arrangement whatsoever. Those who contend for the stratification of the serpentine, may perhaps consider the dykes of felspar, and the vertical masses of green-stone, as intrusive members of the formation; and therefore of more recent origin. To this objection we need only reply; that in many parts of the coast, the vertical masses of serpentine might with the same propriety be considered as intrusive members of a formation of green-stone. To us it seemed impossible to account for such phenomena, except on the supposition of the contemporaneous consolidation of a mass, in which the elementary parts had been irregularly distributed; or their mode of aggregation affected by the local action of disturbing forces. On the other hand it must be conceded, that the green-stone, where it is not immediately interrupted by foreign beds, generally exhibits somewhat of a schistose texture; and at considerable distances from the serpentine, not unfrequently passes into a beautiful green-stone Veins in the slate. ated with it. It According to the hypothesis we have adopted, the serpentine can hardly be considered to arise from any elements besides those which enter into the composition of the granular rocks associmay therefore be regarded as the result of the intimate union of felspar, diallage, hornblende, magnesian earth, and magnetic iron ore. A continually varying proportion of these materials will account for the different appearances exhibited by a rock, which in many instances is not sufficiently homogeneous to be included in the class of simple minerals. Every part of it on the eastern coast, between Coverack and Balk Head is porphyritic; but this structure can only be considered as accidental ; for we lose all trace of it in the greatest part of the patch of serpentine which occurs near Porthalla. I have already mentioned the veins which traverse many parts of this formation. We found them very abundant on both sides of Kennick Cove; still more so in the ruinous cliffs between Kennick Cove and Callean Cove; and we remarked some, of very unusual dimensions, among the crumbling masses which had fallen into the great amphitheatre west of Cadgwith. In some instances they ascend along the face of the cliff in well defined lines; and may, therefore, have originated in fissures, formed by a retreat at the moment of consolidation, and subsequently filled by infiltration. Most frequently their direction is ill defined, and they ramify into minute threads; often filled with steatite, occasionally seeming to pass into silky transverse fibres of asbestos. Sometimes the smaller veins are filled with small laminæ of talc. Their pearly lustre, unctuosity, and want of elasticity, seemed to determine their species. In the flame of the blow-pipe they continued to exfoliate, until there remained only a minute atom which melted with difficulty into a light brown enamel. In the larger veins we often remarked among much decomposing matter, coarse asbestos; in which the fibres were arranged longitudinally, associated with impure varieties of fibrous and indurated talc. The whole substance of the vein would sometimes pass into an unctuous ligniform mass, disposed in undulating lamina, which very rarely alternated with thin layers of noble serpentine. Sometimes these veins were divided into several parallel portions, by the intervention of carbonate of lime; while other parts of the mass were studded over, and mixed with beautiful minute rhombs. The outer part of the vein was occasionally coated over with a kind of steatite, and studded with small botryoidal masses, which had a stellated fracture. These globules, if we mistake not, are formed by the aggregation of minute scales of silvery talc. In a single instance we found the interior of a small vein coated with small transparent crystals of felspar. Our examination of the coast was too much directed to general facts to allow us to enter into minute details. What we have just stated, can, on that account, only be considered as a sketch of Green-stone slate of &c. such phenomena connected with these veins, as are of obvious occurrence. Beyond Balk Head commences the finest formation of greenFrom some quarries beyond Lizard Cove, stone slate in the whole district. Lizard Cove we obtained specimens capable of being divided into laminæ as thin as paper. In the eastern side of the cove, there were three or four small veins filled with magnesian carbonate of lime, deeply tinged with oxide of iron, and occasionally exhibiting a very unusual and complex crystallization. These minerals were also partially mixed with quartz and iron glance. The schistose beds were slightly inclined to the east; but in the next cove, where they were intersected by many contemporaneous veins of carbonate of lime, the great planes of cleavage dipped to the north. On the south side of this cove, near the road which has been excavated in the naked face of the rock, the cliff is cut through by a vein six or eight feet wide, which underlines to the south-east. As its bearing is nearly the same with that of the coast; it may be traced, for a considerable extent, near the foot of the escarpment. When we ascended from the beach it was inaccessible, but from the ferruginous colour of its materials we supposed them to have been nearly the same with those last described. Hot Point. On both sides of Hot Point the formation continued to be characterized by a fine slaty texture; and the beds, on the whole, had a slight inclination to the north-east, though not without some exceptions, arising out of partial contortions. All the more elevated portions of them were externally coated with lichens, which we observed constantly to invest the beds of green-stone slate, whenever that rock prevailed in the upper part of the cliffs. The want of variety in the mineral character of these larger masses, was compensated by their continual change in external form. It would lead me into details inconsistent with the object of this paper to attempt a description of all the features of this |