THE GEOLOGY

AND

EXTINCT VOLCANOS

OF

CENTRAL FRANCE.

By G. POULETT SCROPE, M.P., F.R.S., F.G.S., &c.

Second Edition, enlarged and improved.

WITH ILLUSTRATIVE MAPS, VIEWS, AND PANORAMIC SKETCHES.

LONDON: PRINTED BY WILLIAM CLOWES AND SONS, STAMFORD STREET,

AND CHARING CROSS.

P R E F A СЕ.

WHILE resident in Italy during the winters of 1817– 18-19, I had observed with great interest the volcanic phenomena of Vesuvius, Etna, and the Lipari Isles, and paid considerable attention to the structure of the district west of the Apennines, between Santa Fiora in Tuscany and the Bay of Naples, which presents unmistakeable traces of volcanic action on an extensive scale, though no eruption has taken place there within the historical period.

After my return to England, being for some time at Cambridge, I had the advantage of frequent intercourse with the late Professor E. D. Clarke, who was himself well acquainted with volcanic Italy, and Professor Sedgwick, at that time commencing his distinguished career as a geologist. The doctrines of Werner were then so completely in the ascendant that it was considered little better than heresy to dispute any of them. Yet it appeared to me, from the knowledge of igneous rocks I had acquired in Italy, that the dogmatic canon of that school which denied a volcanic origin to the Floetz Trap-rocks (as basalt, clinkstone, and

trachyte were then called), and declared them to be precipitations from some archaic ocean, was signally

erroneous.

My two friends agreed with me in the opinion that the error of the Wernerians in undervaluing, or rather despising altogether as of no appreciable value, the influence of volcanic forces in the production of the rocks that compose the surface of the globe, formed a fatal bar to the progress of sound geological science, which it was above all things desirable to remove.

Being shortly after free to choose my path of travel, I determined to examine with care such evidence upon this point as might probably be found in Auvergne and the neighbouring districts-a country where the products of extinct volcanos are brought into contact with some of the earliest crystalline rocks, as well as with the most recent (tertiary and freshwater) strata.

For this purpose, in the beginning of June, 1821, I established myself at Clermont, the capital of the department of the Puy de Dôme, and passed some months in continual examination of the geology of the neighbourhood; removing from thence, as it became convenient, to the Baths of Mont Dore, Le Puy (Haute Loire), and Aubenas (Ardèche). I afterwards revisited Italy, where I had the good fortune to witness by far the most important eruption of Vesuvius that has occurred within this century-that of October, 1822.