OCR Text |
Show X three exceptions, recognized by Signor Costa as species now inhabiting the Mediterranean, a circum .. stance which greatly astonished me, as I procured some of them at the height of 2000 feet above the level of the sea (Vol. iii. p. 126). Early in November, 1828, I crossed from Naples to Messina, and immediately afterwards examined Etna, and collected on the flanks of that mountain, near Trezza, the fossil shells alluded to in the third volume (p. 79, and Appendix II., p. 53). The occurrence of shells in this locality was not unknown to the naturalists of Catania, but having been recognized by them as recent species, they were supposed to have been carried up from the sea-shore to fertilize the soil, and therefore disregarded. Their position is well known to many of the peasants of the country, by whom the fossils are called 'roba di diluvio.' In the course of my tour I had been frequently led to reflect on the precept of Descartes, 'that a philosopher should once in his life doubt every thing he had been taught;' but I still retained so much faith in my early geological creed as to feel the most lively surprise, on visiting Sortino, Pentalica, Syracuse, and other parts of the Val di N oto, at beholding a limestone of enormous thickness filled with recent shells, or sometimes with the mere casts of shells, resting on marl in which shells of Mediterranean species were ~mbedded in a high state of preservation. All idea of attaching a high antiquity to a regularly stratified PRJ': FACE. xi limestone, in which the casts and impressions of shells alone were discernible, vanished at once from my mind. At the same time, I was struck with the iden .. tity of the associated igneous rocks of the Val di N oto with well known varieties of ' trap ' in Scotland and other parts of Europe, varieties, which I had also seen entering largely into the structure of Etna. I occasionally amused myself with speculating on the different rate of progress which Geology might have made, had it been first cultivated with success at Catania, where the phenomena above alluded to, and the great elevation of the modern tertiary beds in the Val di N oto, and the changes produced in the historical era by the Calabrian earthquakes, would have been familiarly known. From Cape Passaro I passed on by Spaccaforno and Licata to Girgenti, where I abandoned my design of exploring the western part of Sicily, that I might return again to the Val di Noto and the neighbourhood of Etna, and verify the discoveries which I had made. With this view I travelled by Caltanisetta, Piazza, Caltagirone, Vizzini, Militello, Palagonia, Lago N aftia, and Radusa, to Castrogiovanni, and from thence to Palermo, at which last place I procured the shells named in Appendix II. p. 55. The sections on this new route confirmed me in my first opinions respecting the Val di N oto, as will appear by the 6th, 8th, and 9th chapters of the third Volume. When I again reached Naples) in January, 1829, I |