OF

GEOLOGY:

BEING

AN INQUIRY HOW FAR THE FORMER CHANGES OF

THE EARTH'S SURFACE

ARE REFERABLE TO CAUSES NOW IN OPERATION.

BY

CHARLES LYELL, Esq. F.R.S.

FOREIGN SECRETARY TO THE GEOLOGICAL SOCIETY OF LONDON.

"Amid all the revolutions of the globe, the economy of Nature has been
uniform, and her laws are the only things that have resisted the general
movement. The rivers and the rocks, the seas and the continents, have been
changed in all their parts; but the laws which direct those changes, and the
rules to which they are subject, have remained invariably the same."

PLAYFAIR, Illustrations of the Huttonian Theory, § 374.

IN FOUR VOLUMES.

VOL. I.

THE THIRD EDITION.

LONDON:

JOHN MURRAY, ALBEMARLE STREET.

1834.
EPB

PUBLIC LIE

159175

ASTOR, LENOX AND TILDEN FOUNDATIONS. 1899.

PREFACE.

IN the Preface to the former edition of the "Principles of Geology," I gave a brief account of the progress of the work up to the publication of the Third Volume in 1833. This account I shall now repeat with some omissions, and with the addition of such information as I think will be useful to the reader respecting the latest alterations made in the work.

The original MS. of the "Principles of Geology" was delivered to the publisher at the close of the year 1827, when it was proposed that it should appear in the course of the year following, in two volumes octavo. Many causes concurred to delay the completion of the work, and considerably to modify the original plan. In May, 1828, when the preliminary chapters on the History of Geology, and some others which follow them in the first volume, were nearly finished, I became anxious to visit several parts of the continent, in order to acquire more information concerning the tertiary formations. Accordingly,

collected many recent testacea from the seas surrounding the Calabrian coasts. His comparison of the fossil and living species had led him to a very different result in regard to the southern extremity of Italy, from that to which Signors Guidotti and Bonelli had arrived in regard to the north; for he was of opinion that few of the tertiary shells were of extinct species. In confirmation of this view, he showed me a suite of fossil shells from the territory of Otranto, in which nearly all the species were recent.

In October, 1828, I examined Ischia, and obtained from the strata of that island the fossil shells named in Appendix II. Vol. III., p. 57. of the first edition. They were all, with two or three exceptions, recognized by Signor Costa as species now inhabiting the Mediterranean; a circumstance which greatly astonished me, as I procured some of them at the height of two thousand feet above the level of the sea (Vol. III. p. 390.).

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. 335., and Appendix II., p. 53., first edition). The occurrence of shells in this locality was not unknown to the naturalists of Catania; but, having been recognized by them