one idea, all the facts which they saw told in the same scale, and they saw no other facts. Their facts were all deduced from one region, under the domain of one power, to whose agency the theory had been, in the first instance, very carefully adapted. The followers of Werner were many of them blind in their devotions, some knew no other facts than Werner's; and when they did look out for facts in this, or other lands, beyond the German pale, it was with German eyes: they caught at all the facts which were favourable-saw none which were unfavourable to the aqueous theory.

Hutton and Playfair, on the other hand, from having made the basalts and whins of Scotland their peculiar study, were led to regard fire as the chief formative agent in all rocks; in which they were strengthened by the very striking experiments of Sir James Hall, who found that by exposing pulverised rocks to heat, under such pressure as would prevent the gasses from escaping, they would become consolidated; and not only rocks but saw dust, or vegetable matter, thus treated, could be converted into coal: and he also found that substances which were converted into glass by cooling rapidly, might, by gradual cooling, be made to assume an opake and stoney character, instead of the shining vitreous character. Thus, for consolidating the earths into rocks, fire appeared to be a sufficient agent, while, at the same time, it was shown that heat, combined with pressure, would neither calcine nor vitrify, but only consolidate.

Both parties, however, left unaccounted for the notorious and all-important phenomenon, that vast masses of strata are conformable with each other, yet not homogeneous; a fact which renders both these theories, under any modification, equally inadmissible: for supposing a stratum of hard silicious sandstone to lie between two strata of clay, yet all three perfectly conformable, which is a very common case, this state of things cannot be accounted for by either hypothesis; water will not account for it because the ingredients differ; fire will not account for it because the clay is not consolidated; and any pressure which enabled the fire to consolidate the rock would consolidate the clay also, which lies in juxta-position on both sides of the rock.

The English geologists, who have since taken the lead, and chiefly in consequence of the formation of a Geological Society in London, began without any theory, and on the sole principle of collecting and classifying facts; yet, from the remarkable abundance of fossils in the London clay and gravel, and other deposits lying above the chalk, they have.

been led to the study of animal remains, and have given fossils a very prominent place in determining the distinctions between different deposits, and the order in which they have succeeded each other. Had they kept to this, their proper province, all would have been well; and we should have been able to use their local knowledge of fossils in full confidence, without abatement, without qualification: but, unfortunately, they, too, have been ensnared by theories, which we do not wish to speak of harshly, and which we would not allude to at all but that they do warp observation and distort facts; while, in prematurely grasping at too much, they are in danger of losing all.

All these errors are gendered by that partiality which arises from limited observation; and the corrective will come in proportion as other facts from distant quarters are made known for even, if all the facts in all cases should be tinged with partiality, yet if they be from distant regions they will be different kinds of partiality, and the errors will neutralise or compensate each other, leaving a residuum of truth; and, therefore, we welcome any observations concerning the geology of distant countries, and the more so in proportion as they are more detailed: therefore, we are glad to meet with the works which we have placed at the commencement of this paper, and especially the first of them, which is a very striking account of a most remarkable country, and a country with which we are only just beginning to become acquainted. It is by an extension to all parts of the world of such observations as have been made in England that truth will be established; and until this is done we cannot be expected to receive, as universal principles or foundations on which geology as a science may securely rest, facts derived from one country alone, and that also a country, the geological structure of which is notoriously different from all other countries, in the number and variety of the mineral products found within the same extent of space, and in the singular abundance of the most useful minerals-coal, iron, and lime-which are found throughout the whole length of the land from Bristol to Newcastle, and which have already formed a larger ingredient of the prosperity of England than any other of her internal sources, yet seem destined to exert an influence still greater on the coming age, and carry her forward in a career at once so rapid and extensive as to cast all our past experience into the shade-to make England one city-and that the metropolis of the world.

England presents a remarkably good field for geological

observation, from its great variety of rocks all abutting against its western mountains, and exposed along its southern coast, where their succession and junction is traceable along the cliffs which are laid bare by the action of the waves. The granites of Cornwall form a base against which the mica slates and shales of Devonshire lean, succeeded by the limestone of Plymouth, and the marles and lias of Lyme Regis. To this succeeds the oolite of Dorset, passing into Portland stone and Purbeck, surmounted by chalk, London clay, and the fresh-water formations of the Isle of Wight. This complete succession is a great advantage, in simplifying our ideas at the commencement of a study; but it is accompanied with the temptation of making our systems of geology exclusively English, from assuming that we have on our southern shores a complete display of the whole succession of strata, from the fundamental granite to the last sands and gravels which lie over the Norfolk crag or London clay. We think that, as no formation is universal which is not to be found or accounted for everywhere, when the formations above and below it appear, so every universal formation, or its equivalent, should appear in such a succession as this; unless we can account for its absence by marks of denudation, or disruption, leaving a manifest hiatus, which we are then at liberty to supply from other lands.

But in finding equivalents, or in supplying a deficiency, we are in danger of unwarrantably increasing the number of universal formations; and of making an aggregate of many particulars, which has real existence nowhere. We cannot allow that the universal formations are more in number than the distinct formations which are exposed in every such situation as the southern coast of England: and if it be asserted that another formation ought to be present, we require distinct proof, from more than one other series, that this formation is accidentally absent from the English series; and every such proof of accidental absence generates the suspicion, on the other hand, that some may be accidentally present which ought not to be regarded as universal formations.

In the last geological map of England, Mr. Murchison regards the distinct formations as eighteen; but of these only twelve appear on the southern coast. These twelve, therefore, are all that should à priori be regarded as universal, and the absent six may be regarded either as local deposits, or as having equivalents and substitutes in some of the twelve. We find, in fact, that two of the absent formations are the upper and lower Silurian, which have indisputably their

equivalents in the old red sandstone of Devonshire; and the other four, which are absent, belong to the coal measures, which we have always regarded as local deposits, or, when regarded as a whole, would call it the independent coal formation: believing each coal district to be distinct and separate from all other formations, and having no right whatever to a place among universal deposits, or to rank as one of a geological series.

Every universal deposit, having a place in a series, must re-appear whenever the strata which lie over it are removed; as the Hastings sand re-appears at the Isle of Wight, and at Purbeck, under the green sand and the chalk. But if the carboniferous strata were universal, they ought to appear in the neighbourhood of Torbay, between the old red sandstone and the new; but nothing at all like them appears, except a few patches of Babicombe and Devon marble. By the same rule, if strictly applied, we might strike out the lias, and the Oxford clay, from the series of universal deposits, since they are decidedly local and partial; though not so entirely separated into patches as the independent coal formations-and of course the London clay, and the other less considerable deposits above the chalk, which are only accidental lodgements in the superficial hollows, and have so little solidity or constancy of character-have still smaller pretensions to be ranked among formations, or as forming members of a geological series. These being struck out would leave only eight distinct formations above the granite-mica slate, old red sandstone, new red sandstone, oolite, Portland stone, Hastings sand, green sand, and chalk; and it would greatly simplify our ideas to regard all other strata as only appendages or subdivisions of these.

Clay slate is regarded by Mr. Murchison as only an appendage of the old red sandstone, and chlorite as an appendage of mica slate. This principle might be extended; and, in studying foreign geology, we must be prepared to find rocks which, though differing from our own, it will be safer to regard as equivalents for, or subdivisions of formations with which we are already acquainted, than to constitute new formations, which convey no new ideas, but are little more than the same thing under a new name.

The most remarkable of the recent additions to our knowledge of extensive formations is that which has resulted from Mr. Murchison's examination of the old red sandstone of Cumberland, and Wales, and Devon, and South Russia; yet all these can only be regarded as subdivisions of one great

formation, for some of the members prevail in one locality, some in another; and the other members are reciprocally defective, and seen only in the minutest indications, if not totally wanting. But looked at in reference to the primary and secondary rocks, these all, as one whole, occupy precisely the same place in the system which had been long ago assigned to our old acquaintance; it is, after all, only an old friend under two or three new names: and though we quite agree with Linneus, in thinking that it requires more science to distinguish species than to form genera, and so give all credit to Mr. Murchison for his sagacity, we would also urge the propriety of respecting well established genera, both because classification and order are stamped upon all that we see, and because life is too short to be wasted in learning a new classification for every new discovery.

For it is to be borne in mind that, as things at present stand, one classification is as good as another, provided it be equally clear. All present arrangements are merely optional and conventional-are not scientific-are merely like the sorting of papers in an office, or the arrangement of words in a dietionary, for more convenient reference. The principles upon which a scientific arrangement should be made are not yet discovered.

One of the most able and candid of geologists, Professor Ansted, in his " Introduction to Geology," (p. 93), observes:

"It is, perhaps, an unfortunate circumstance for geology, that in whatever way the subject is first viewed, it is surrounded with difficulties, from the impossibility of actually connecting geological phenomena with the operations now going on around us. If, for instance, we endeavour to trace back the history of the world, and pass from the consideration of the alluvial matter carried down by rivers, to that of the gravel, which appears to be the newest deposit, and one abundantly spread over various formations, we are at once struck by the utter inadequacy of any cause now in action to produce such effects. If, on the other hand, we attempt to look back to that far distant period when the world was only beginning to assume its present form, it requires no slight effort to dispossess the mind of a certain incredulity, naturally arising from those feelings of astonishment produced by the contemplation of phenomena so unfamiliar to us, and apparently so inexplicable; and a great effort is required fully to comprehend them. Before, however, entering on the considerations of the Paleozoic rocks, this effort must be made; for in them we have a series of strata, whose total thickness amounts to many thousand feet, which contain, in rich abundance, several distinct groups of animal and vegetable remains, not one of them the same, and but few of them similar to the animals and vegetables of our own time; and these