PREFACE.

THE attempt to compress so vast a theme as Geology within the narrow limits of a duodecimo volume of such spare dimensions, will be regarded by those, who, in ponderous tomes, have communicated to the world the result of years of labour in this department of science, as absurd and futile. The author does not address himself to these, nor to that class of readers to whom the subject is familiar, but humbly aims at stimulating the intellectual appetency of those who have enough of curiosity to be anxious to peep into the interior of this portion of the Temple of Science, and to know something of the wonders which it contains, but who lack sufficient ardour to grapple with and surmount the technical difficulties which obstruct their approach. To such persons the substance of the following Sketch was originally addressed in the form of Lectures by the author, whose only apology for the publication is the numerously-expressed wish of his audience.

GEOLOGY IN 1835.

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GEOLOGY, as the original Greek words from which the term is derived import, is the science or knowledge of the earth. Unlike Geography, which delineates the surface of the globe, and the various tribes of animate beings with which it is peopled; and distinct from Astronomy, which defines the figure, examines the position, and has reference to the external circumstances of our planet as a member of the solar tem, the business of Geology is to investigate the internal structure and configuration of this vast mass of matter upon which we dwell-a subject of the highest interest and importance to man. In the character of its results, and the magnitude and sublimity of the objects of which it treats, Geology may be with propriety ranked in the scale of the sciences, next to Astronomy; but while the one has attained a degree of perfection, which appears almost incompatible with the limited capacity of the human mind, the other has only, within a very recent period, assumed the dignified form of a science. It is, however, established on a secure and permanent basis: the intelligence of the age which gave it birth is fast accelerating its growth to maturity: observations are extending and facts accumu

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lating, with a rapidity unparalelled in the annals of science. But no Newton has yet arisen to grapple with contending theories-to concentrate with superhuman intelligence the scattered elements-to mould with Promethean skill the inflexible materials, and impart perfection and immutability at once to a system. This circumstance peculiarly recommends Geology as a subject of popular study. Where a high degree of excellence has been attained by an individual, in any art or science, emulation the main-spring of exertion is checked: men are dissatisfied with the result of their efforts: the ardour which would have carried to the goal had the race been equal, subsides into despair. Who, in geometry, during the long interval of two thousand years, has attempted to improve upon Euclid? In the vain attempt to imitate the immortal productions of Greece and Rome, how many an artist has laid down his pencil in disgust! Who has ever dared to entertain the thought of displacing Newton from the pinnacle of glory, on which he proudly stands, and bids defiance to emulation? The mere acquisition of his ideas, the comprehension of his complex deductions, requires an effort which ordinary minds are scarcely equal to. In Geology, however, the ground is unoccupied : a wide field is open to emulation, and results of the highest importance await a patient and attentive examination. The sphere of observation is co-extensive with the world itself, and every locality is replete with information-accessible, and intelligible to all, without the preliminary acquirements essential to the study of Astronomy, and other abstract sciences.

It is a singular feature in the history of the human

mind, that while with comprehensive grasp it had measured the heavens, and weighed all the planets of the solar system, and with telescopic eye was exploring the confines of the universe, the earth and all the interesting phenomena which it has since disclosed, were disregarded. Elated by their splendid discoveries in space, Astronomers seem to have looked with contempt upon the earth beneath their feet, or at most to have regarded it merely as a station from which their observations upon surrounding objects were made, for which purpose a knowledge of its form and position was all that

was necessary.

Nothing satisfactory can be gathered from the opinions of the ancients on this interesting branch of the physical sciences. Aristotle, the master-spirit of his age, seems to have been aware that sea and land had frequently changed their relative positions: but he also contended that the earth had volition, and a better specimen of his syllogistic philosophy, which during twenty centuries held dominion over men's minds, and which at a period not very remote from our own times it was a penal offence to controvert, can scarcely be adduced

"Everything which has self-motion has volition :

The earth is endowed with self-motion :

Ergo the earth has volition."

Thales, an ancient Greek philosopher, suggested that all things had their origin in water; and the Pythagoreans generally seem to have had some indefinite notions on the subject of the changes which the surface