mass of earthy matter might be much richer in gold than another, and yet be far less profitable to work, because the extraction of the metal from the richer mass might be much more difficult, and, therefore, much more expensive than from the poorer. It is obvious, that it is much easier to remove and wash a quantity of sand, gravel, and clay, than it would be to quarry out, crush, and wash an equal bulk of the hard and solid rock. It is also much easier to follow out, dig, and extract the richest beds, or portions of a mass of gravel, &c., than it would be to follow out, and mine, and extract a quartz vein in the solid rock. The bed lies horizontally, never at any great depth, and may be got either as open work," by removing the covering, or by pits or galleries. The quartz vein is more or less perpendicular, soon reaches a considerable depth, and requires much more skill and more expensive machinery to work.

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Still, making allowance for all these circumstances, it is probable that the fact remains as a fact, that, bulk for bulk, the "drift" of the rock is richer than the rock itself. Even, then, it does not necessarily follow, that the portion of the rock removed to form the drift was richer in gold than the part that remains near the surface. This "fact" would result simply from the action of denudation and removal of earthy matter having been far greater than at first sight appears. Vast quantities of earthy matter have been broken off, ground down, and utterly swept away, the gold from every portion having, from its superior gravity, remained behind, to enrich, beyond its due proportion, the remnant of the drift that was left.

7th. It is generally believed that the upper part of an auriferous vein is the richest. This, however, we are not inclined yet to receive as an established fact. We have just seen that the comparative richness of the drift does not necessarily prove it; and, as the result of mining operations, we should be glad of more precise information, as to how far the increased expense of working the vein as it descended had had an influence in giving rise to the idea.

8th. The period at which the gold was imparted, either to the rocks or to their quartzose veins, in its present abundance. This Sir R. Murchison believes to have been a very modern

geological period, in the Ural mountains at all events; founding his supposition chiefly on the older gravels of the neighbourhood, the conglomerates of the Permian and other rocks, not containing any gold. Giving full weight to that argument in that particular locality, it yet remains to be confirmed by observations in other regions, before it can be stated as a general fact in the history of gold.

9th. The exact method of the production of gold, that is, of its being located where we now find it in its present quantity, either in auriferous rock or in the quartz veins traversing rock. This is a matter of which we really know so very little, that the less we say about it the better.

In the concluding chapter of the work, Sir Roderick not only sums up the result of his descriptions of fact, but expounds and defends the theoretical philosophy which he derives from them. We will allow him to state some of these results in his own words :

"Reverting to the main object of this work-the history of the primæval rockslet us now see what inferences may be drawn from data established by the researches of the geologist. Passing rapidly over the earliest stages of the planet, which are necessarily involved in obscurity, our sketch of ancient nature began with the first attainable evidences of the formation of sediments, composed of mud, sand, and pebbles. It was shown that the lowest accessible of these deposits, though of enormous dimensions, and occasionally less altered than strata formed after them, are almost entirely azoic, or void of traces of inhabitants of the seas in which they were accumulated. One solitary genus of zoophytes has been alone detected in such bottom rocks, the heat of the surface during those earlier periods having been, it is supposed, adverse to life.

"Proofs were then adduced to demonstrate that, in the next formations, scarcely differing at all in mineral character from those which preceded them, observers in various regions have detected clear and unmistakable signs of a contemporaneous appearance of animal life, as shown by the presence of a few genera of crustaceans, molluscs, and zoophytes, occupying layers of similar date in the crust of the earth. Proceeding upwards from this protozoic zone, wherein organic remains are comparatively rare, we then ascended to other sediments, in which, throughout nearly all latitudes, we recognise a copious distribution of submarine creatures, resembling each other very nearly, though embedded in rocks now separated by wide seas, and often raised up to the sum

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mits of high mountains. Examining all the strata exposed to view, that were formed during the first long natural epoch of similar life, termed Silurian, we found that the successive deposits were charged with a great variety of forms of the trilobite, a peculiar crustacean; of the orthoceratite, the earliest chambered shell-as well as with numerous exquisitely - formed molluscs, criniods, and zoophytes, the genus graptolite of the latter class being exclusively found in these Silurian rocks.

In short, my contemporaries have assembled from those ancient and now desiccated marine sediments or repositories of primæval creatures, examples of every group of purely aquatic animals, save fishes. The multiplied researches of the last twenty years have failed to detect the trace of a fish, amid the multitudes of all other marine beings, in the various sediments which constitute the chief mass of the Silurian rocks. Of these, though they are the lowest in the scale of the great division, vertebrata, we are unable to perceive a vestige until we reach the highest zone of the Upper Silurian, and are about to enter upon the Devonian period. Even on that horizon, the minute fossil fishes long ago noticed by myself are exceedingly scarce, and none have since been found in strata of higher antiquity. fact, the few fragments of cartilaginous ichthyolites of the highest band of Silurian rock still remain the most ancient known beings of their class.

In

"Looking, therefore, at the Silurian system as a whole, and judging from the collection of facts gathered from all quarters of the globe, we know that its chief deposits (certainly all the lower and most extensive) were formed during a long period, in which, while the sea abounded with countless invertebrate animals, no marine vertebrata had been called into existence. The Silurian (except at its close) was, therefore, a series in which there appeared no example of that bony framework of completed vertebræ, from which, as an approach to the vertebrate archetype, the comparative anatomist traces the rise of creative power up to the formation of man.

"Whether, therefore, the term of 'progressive,' or that of 'successive,' be applied to such acts of creation, my object is simply to show, upon clear and general evidence, that there was a long period in the history of the world wherein no vertebrated animal lived. In this sense the appearance of the first recognisable fossil fishes is as decisive a proof of a new and distinct creation as that of the placing of man upon the terrestrial surface at the end of the long series of animals which characterise the younger geological periods.

"Nor have we been enabled to disinter from the oldest strata of this long period of invertebrate life any distinct fragments of land plants; but just in the same stratum, where

in the few earliest small fishes have been detected, there also have we observed the first appearances of a diminutive, yet highly organised tree vegetation.

Yet, however they admit the facts, some of my speculative contemporaries think that they can so explain them, as not to justify the inference of progressive creations. They suppose that nearly all the strata of date antecedent to those in which the first signs of life have been detected, are often in so crystalline a state, that if they originally contained remains of animals, the traces of them must have been obliterated by changes since effected in the structure of the rock. Now, if this supposition had been supported by the researches of late years, we must doubtless have admitted, that the origin of life in the globe was buried in hopeless obscurity; but the hypothesis has been set aside, as before explained, by the fact of the existence of deposits many thousands of feet thick, and scarcely at all altered, which, made up of sand, mud, and pebbles, constitute the very foundations of the fossil-bearing strata.

"In these huge lower sediments a zoophyte only has been detected, but immediately above them, in various and distant countries, we perceive the oldest-known small group of animals. If the opposing argument had been derived from the evidences collected in one region only, it might have been suggested, that as the same formation which is barren in life over one district, teems with signs of it in another, so the infra-Silurian, or bottom rocks (the Cambrian of the geological surveyors), may still prove to be fossiliferous. But even if a few types should hereafter be discovered in those lower strata, the reasoning would in nowise change its character if such infra-Silurian fossils were not found to pertain to higher forms of life - a result which would be in manifest contradiction to all ascertained facts respecting geological succession. Nor can we allow this hypothesis, founded on an exceptional possibility, to countervail the universal data that have been registered, and which demonstrate in many countries the unfossiliferous character of the lowest sedimentary formations. This prevalence

of a widely spread primæval ocean, and of a surface which had not yet been subjected to those innumerable variations of outline which have since changed and modified the different climates of the earth, when connected with a belief in the former greater radiation of heat from its interior, are the chief data required to satisfy us that physical conditions then prevailed with which the nature and extensive spread of the earlier groups of animals are in harmony.

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"The uniformitarian, who would explain every natural event in the earliest periods, by reference to the existing conditions of beings, is thus stopped at the very threshold

of the palace of former life, which he cannot deprive of its true foundations. Nature herself, in short, tells him through her most ancient monuments, that though she has worked, during all ages, on the same general principles of destruction and renovation of the surface, there was formerly a distribution of land in reference to the sea, very different in outline from that which now prevails. That primæval state was followed by the outbursts of great volumes of igneous matter from the interior, the extraordinary violence of which is made manifest by clear evidences. Fractures in the crust of the earth accompanied by oscillations that suddenly displaced masses to thousands of feet above or beneath their previous levels, were necessarily productive of such translations of water, as to abrade and destroy solid materials to an extent infinitely surpassing any change of which the historical era aflords an example.

"I would here cite the works of Leopold Von Buch, Elie de Beaumont, Sedgwick, Studer, and numerous other geologists, for countless proofs of this grander intensity of former causation, by which gigantic masses were inverted, and strata forming mountains have been so wrenched, broken, and twisted, as to pass under the very rocks out of whose materials they were constructed.

"The numerous positive evidences of a former wide distribution of similar animals and plants enable us fairly to bring before our mind's eye the physical geography of these great epochs, when such large portions of our present continents were under the waters, and forests of tree ferns occupied very extensive low lands, subjected, during a long period, to numerous oscillations. Not less clearly do we infer from other physical evidences how eruptive forces subsequently acted, breaking out with great violence after the close of the carboniferous era, and throwing the strata into those grand undulations and contortions, accompanied by stupendous fractures, which have given to the coal basins their curvatures and limits.

"Thenceforward was continued that long series of additional and repeated emissions of volcanic matter from within, of elevations of the sea bottom, and corresponding depressions of land, combined with the metamorphism of the strata (these changes being often accompanied by corresponding new creations of animals suited to the existing conditions) during the secondary and tertiary periods. By these great physical operations our planet was eventually brought to possess the climatal relations which have for so long a time prevailed. That these elevations and depressions finally produced a state of things altogether distinct from that of the earlier eras, is in short registered by a multitude of well attested data.

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"From the effects produced upon my own

mind, through the study of these imperishable records, I am indeed led to hope that my readers will adhere to the views which, in common with many contemporaries, I entertain of the succession of life; for he who looks to a beginning, and traces thenceforward a rise in the scale of being, until that period is reached when man appeared upon the earth, must acknowledge in such works repeated manifestations of design, and unanswerable proofs of the superintendence of a Creator."

We leave these passages to bear with all their own weight upon the reader's mind, simply remarking that whatever decision may be come to as regards the origin and progress of ani mal life upon the globe, we can never subscribe to the doctrines here promulgated with regard to its ancient physical geography, and the inorganic forces at work on it. It can be clearly shown that the erosive action of water was never greater than at present; that the old ejections of igneous matter were not one whit more or less extensive, or more or less violent than those that have taken place within the historic period; while with regard to the uniformity of surface and the slight elevation of land and little depth of sea so inconsistently supposed to have prevailed, as the result of the most violent and convulsive internal agencies, it can be proved to demonstration that old surfaces that had once existed as dry land, had subsequently been depressed many thousands of feet below the sea within the early palæozoic period, and a corresponding and contemporaneous elevation of land thus made in the highest degree probable. With regard to the closing paragraph, also, we may observe, that it is one thing to deny a beginning altogether, and quite another to say that our earliest geologic records do not give us any account of it. These are points which, as they are not matters of fact, but merely of inference and deduction, men will differ upon as long as their minds are differently constituted and variously trained. Theories, however profound, and speculations, however brilliant, dazzle and amuse for a time, and then often pass away, and are heard of no more

"A breath unmakes them, as a breath hath made;"

but he who has with patient labour added one set of new facts to the