Book Description

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1881 edition. Excerpt: ...of the Lizard and an extensive tract to the north of the serpentine region, besides some more limited areas. He found that this series was separable into a lower or micaceous group--schists with various green minerals (often a variety of hornblende), or with brownish mica; a middle or hornblendic group, characterized by black hornblende; and an upper or granulitic group, characterized by bands of quartz-felspar rock, often resembling in appearance a vein-granite. These are all highly metamorphosed; yet the second and third occasionally retain to a remarkable extent indications of the minuter bedding structures, such as alternating lamination and current bedding of various kinds. They form, in the author's opinion one continuous series, of which the uppermost is the thinnest. The general strike of the series, though there are many variations, is either N.W. or W.N.W. The junctions of the Palaeozoic with the metamorphic series at Polurrian and at Porthalla were described. These are undoubtedly faulted; and the two rocks differ greatly, the former being a slate like any ordinary Palaeozoic rock, the other a highly metamorphosed schist. Moreover, fragments of the hornblende schist and a kind of gneiss occur in a conglomerate in the former, S. of Nare Point. The author considers the metamorphic series (the microscopic structure of which was fully described) undoubtedly Archaean, and probably rather early in that division. The rocks of the micaceous group have considerable resemblance to the greenish and lead Intending Exhibitors are requested to communicate as early as possible with the Assistant Secretary. coloured schists of Holyhead Island and the adjoining mainland of Anglesey, and of the Menai Strait. Two outlying areas of serpentine, ...