which that work was to be executed, gave rise to a good deal of discussion, and even of controversy. In these debates Dr Hutton took a share, and wrote several pieces, in which the grave and the ludicrous were both occasionally employed. None of these pieces have been published; but the plan that was in the end adopted was that in favour of which they were written. It is unnecessary, however, to enter into the merits of a question which has long ceased to interest the public.

From the time of fixing his residence in Edinburgh, Dr Hutton had been a member of the Philosophical Society known to the world by the three volumes of physical and literary essays so much and so justly esteemed.* In that society he read seve ral papers; but it was during the time that elapsed between the publication of the last of the volumes just mentioned, and the incorporation of the Philosophical into the Royal Society of Edinburgh; which last was established by a royal charter in 1783. None of these papers have been published, except one in the second volume of the Transactions of the Royal Society, "On certain Natural Appear

*The Philosophical Society was instituted about the year 1739. The first volume of Essays was published in 1754; the second in 1756; the third in 1771. From the year 1777 to 1782, the meetings of the Society were pretty regular, much owing to the zeal of Lord Kames. Mr Maclaurin may be regarded as the founder of this Society.

ances of the Ground on the Hill of Arthur's Seat."

The institution of the Royal Society of Edinburgh had the good effect of calling forth from Dr Hutton the first sketch of a theory of the earth, the formation of which had been the great object of his life. From the date formerly mentioned, when he was yet a very young man, and making excursions on foot through the different counties of England, till that which we are now arrived at, a period of about thirty years, he had never ceased to study the natural history of the globe, with a view of ascertaining the changes that have taken place on its surface, and of discovering the causes by which they have been produced.

He had become a skilful mineralogist, and had examined the great facts of geology with his own eyes, and with the most careful and scrupulous observation. In the course of these studies he had brought together a considerable collection of minerals peculiarly calculated to illustrate the changes which fossil bodies have undergone. He had also carefully perused almost every book of travels from which any thing was to be learned concerning the natural history of the earth; and, in consequence both of reading and observation, was eminently skilled in physical geography.

If to all this it be added, that Dr Hutton was a good chemist, and possessed abilities excellently

adapted to philosophical research, it will be acknowledged, that few men have entered with better preparation on the arduous task of investigating the true theory of the earth. Several years before the time I am now speaking of, he had completed the great outline of his system, but had communicated it to very few; I believe to none but his friends Dr Black and Mr Clerk of Elden. Though fortified in his opinion by their agreement with him, (and it was the agreement of men eminently qualified to judge,) yet he was in no haste to publish his theory; for he was one of those who are much more delighted with the contemplation of truth, than with the praise of having discovered it. It might, therefore, have been a long time before he had given any thing on this subject to the public, had not his zeal for supporting a recent institution which he thought of importance to the progress of science in his own country induced him to come forward, and to communicate to the Royal Society a concise account of his theory of the earth.

As I have treated of this theory in a separate essay, particularly destined to the illustration of it, I shall here content myself with a very general outline.

I. The object of Dr Hutton was not, like that of most other theorists, to explain the first origin of things. He was too well skilled in the rules of

sound philosophy for such an attempt; and he accordingly confined his speculations to those changes which terrestrial bodies have undergone since the establishment of the present order, in as far as distinct marks of such changes are now to be discovered.

With this view, the first general fact which he has remarked is, that by far the greater part of the bodies which compose the exterior crust of our globe, bear the marks of being formed out of the materials of mineral or organized bodies, of more ancient date. The spoils or the wreck of an older world are every where visible in the present, and, though not found in every piece of rock, they are diffused so generally as to leave no doubt that the strata which now compose our continents are all formed out of strata more ancient than themselves.

II. The present rocks, with the exceptions of such as are not stratified, having all existed in the form of loose materials collected at the bottom of the sea, must have been consolidated and converted into stone by virtue of some very powerful and general agent. The consolidating cause which he points out is subterraneous heat, and he has removed the objections to this hypothesis by the introduction of a principle new and peculiar to himself. This principle is the compression which must have prevailed in that region where the consolidation of

mineral substances was accomplished. Under the weight of a superincumbent ocean, heat, however intense, might be unable to volatilize any part of those substances which, at the surface, and under the lighter pressure of our atmosphere, it can entirely consume. The same pressure, by forcing those substances to remain united, which at the surface are easily separated, might occasion the fusion of some bodies which in our fires are only calcined. Hence the objections that are so strong and unanswerable, when opposed to the theory of volcanic fire, as usually laid down, have no force at all against Dr Hutton's theory; and hence we are to consider this theory as hardly less distin guished from the hypothesis of the Vulcanists, in the usual sense of that appellation, than it is from that of the Neptunists, or the disciples of Wer

ner.

III. The third general fact on which this theory is founded, is, that the stratified rocks, instead of being either horizontal, or nearly so, as they no doubt were originally, are now found possessing all degrees of elevation, and some of them even perpendicular to the horizon; to which we must add, that those strata which were once at the bottom of the sea are now raised up, many of them, several thousand feet above its surface. From this, as well as from the inflexions, the breaking and separation