Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/1028

898 which appear impracticable, consist of serpentine; but some of the jutting reefs below resemble hornblende schist.

Descending into Polbarrow Cove by a narrow track, we find that the southern part of it consists mainly of hornblende schist; but there are intrusive veins of serpentine in it close to a natural arch, as well as in the little ridge of schist, on the middle of which stands a small boathouse. Serpentine may also be seen in a quarry above the cliff south of the boathouse. Just north of this is a junction of the schist with the serpentine, which runs obliquely in this direction up the cliff. It now continues for some time; but two low headlands which bound the cove are capped by hornblende schist; and the next one to north is wholly of that rock. There is a gabbro vein in the schist, near the junction with the serpentine, about on a level with the boathouse, and another much higher up the cliff in the latter rock.

Returning to the cliff we come to a small quarry showing a junction of hornblende schist and serpentine. The former rock dips about 27° E.N.E., and in 1873 could be seen to be overlain irregularly by the serpentine. In one part of the quarry a piece of the schist was intercalated between serpentine. In 1876 the relations were less clear. The schist is very dark and full of hornblende. The specimen described above was collected here. The cliffs, as may be seen from the geological map, consist of hornblende schist from this spot to near Cadgwith, when we come to another junction in the celebrated Devil's Frying-pan, obviously an old sea-cave whose roof has fallen in.

The relations of the serpentine with the schist, as seen by descending into this hollow, leave no doubt that the former rock is intrusive. On reaching the shore we find ourselves at the bottom of a funnel-shaped pit communicating with the sea by a natural archway. This, and the greater part of the two adjoining sides, is of hornblende schist, which dips westward at an angle of 40° to 50°, increasing gradually to about 70° towards the west on the southern side, and rolling over considerably on the northern. The remaining side is serpentine.

The junction at the S.W. corner is masked by debris; but on the other it is clearly an intrusive one, a large fragment of schist being entangled between two masses of serpentine. I think that the pre- sent summit of the entrance archway also marks a former junction with the serpentine; for the schist of this looks much disturbed and slickensided, and has a "junction" aspect. Also an overlying block apparently in situ is serpentine. The serpentine is dull mottled blackish brown and red in colour, full of small glittering scale-like crystals with a rather silvery lustre, as at Mullion and at Pradanack Quarry.

After climbing back to the pathway leading to Cadgwith, the descent into that village is mainly over serpentine. But the rocks exposed in the little cove forming the harbour are very characteristic hornblende schists, dipping about 35° N.N.W.

On reaching the summit of the steep ascent which leads from