PREFACE. WHILE resident in Italy during the winters of 181718-19, 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, On my return to England in 1823, I published a volume on the Phenomena of Volcanos.'* In that work unfortunately were included some speculations on theoretic cosmogony, which the public mind was not at the time prepared to entertain. Nor was this, my first attempt at authorship, sufficiently well composed, arranged, or even printed, to secure a fair appreciation for the really sound and, I believe, original views on many points of geological interest, which it contained. I ought, no doubt, to have begun with a description of the striking facts which I was prepared to produce from the volcanic regions of Central France and Italy, in order to pave the way for a favourable reception, or even for a fair hearing, of the theoretic views I had been led from those observations to form. Indeed this obvious error was pointed out in a very friendly manner by the Quarterly Reviewer of this Memoir on the Geology of Central France,' which was shortly after published.† That article was, I believe, the first essay of my distinguished friend Sir Charles Lyell, in the path of geological generalisation which he has since so successfully pursued. And I have sometimes ventured to think that during its composition he may have imbibed that philosophical *Considerations on Volcanos, &c.,' 1825. |