coast, and beyond this to the Ultima Thule' of Melville Island. In South America M. Alcide d'Orbigny has traced the same formations through many degrees of latitude; while on the continent of Europe we have long known them under the old name of transition limestones, as occupying the Ardennes, the neighbourhood of Prague, and the southern coast of the Gulf of Finland. To follow them out in Northern Europe appears to have been the first inducement which attracted Sir R. Murchison to the coasts of Russia. Fortunately, however, for the progress of geology, he did not thus limit his researches, but carried them through all the formations of that mighty empire and the adjacent

countries.

He had formerly extended his acquaintance with the general types of the oldest fossiliferous series, beyond the limits of our own island, by a careful comparative survey of the Rhenish provinces. In this he was accompanied by his old companion in the Highlands and the Eastern Alps, Professor Sedgwick, and by M. de Verneuil. By the profit he then derived from the accurate and minute knowledge of the latter on the specific distinctions of the ancient mollusca, he was induced to invite him to join in his projected visit to Russia, and to contribute the paleontological ̄ department to the work which should record the results of the new investigation.

'To invade Russia, however,' says he, 'as unassisted geologists, with mere hammers and compasses, would have proved but a fruitless mission, had not the countenance of the Imperial Government been obtained. This was secured through the friendly intervention of Baron de Brunow, his Imperial Majesty's representative at the Court of St. James's, who exhibited a generous feeling for the advancement of science, and strongly recommended the undertaking to the protection of his sovereign.'

The summers of 1840 and 1841 were spent in diligent travelling. The whole survey was carried out under the especial orders and protection of the Emperor; and the friends were fully accredited to the governors and chief officers of the provinces they traversed as being, pro hâc vice, in the Russian service. They speak in the warmest terms of the support which they uniformly experienced from his Imperial Majesty's enlightened minister the Count de Cancrine. the very able chief of the état major of the mines, Lieut.-General Tcheffkine, and that good geographer and geologist, Colonel Helmersen. The personal kindness of the Emperor to our own countryman was, we can add, on numberless occasions displayed in the most striking manner. No man of science, we venture to say, has in modern times received marks of greater favour and confidence from a great sovereign.

Still, our geologists, though their book was already advancing through the press, could not rest satisfied without new expeditions. In 1843 Keyserling undertook, accompanied by Lieutenant Krusenstern, the survey of the north-eastern wilds, inhabited only by Samoyedes and Zyrians, and defined the previously unknown Timan range; while Murchison explored Poland, the Carpathian Mountains, and those eastern parts of Germany which appear upon his map. Lastly, in 1844, Sir Roderick travelled through extensive districts of Norway and Sweden, which afforded, as we shall presently see, the most important results.

One great object, it appears, which he had in view in testing the value and applicability of his new classification of the older sedimentary deposits over a vastly larger region than any previously examined, was to ascertain if the origin of animal life in the crust of the globe could there be clearly defined, and if so, to what extent the succession of subsequent and different types of beings was also there exhibited. Knowing that the enormous area he was about to explore was singularly void of all eruptive and volcanic rocks, it was for that very reason he presumed that he might there be able to read off the pages of the most ancient chronicles of Mother Earth in nearly an unruffled condition. He says:

'Bounded on the north by a vast country occupied by crystalline rocks, and surrounded on other sides by the mountains of the Ural, the Caucasus, and the Carpathians, Russia in Europe may be viewed as a spacious low undulating region which opens out into the great depression of the Caspian Sea on the south-east, and to the flat countries of Northern Germany on the west.'

After an allusion to the total absence of mountains throughout this great basin, and the lowness of its watersheds, including the Valdai Hills-the noble rivers of Russia are dwelt upon, as constituting her dominant physical features; and whilst it is stated that an acquaintance with their low dividing barriers enabled Peter the Great to unite these streams by canals, and thus to secure to his country important commercial advantages and much internal power,' so is it shown how they have served to reveal to the geologist the true nature of the subsoil.

'In other countries the upper lands often expose stony masses which emerge from beneath the soil as separate or continuous rocks, and afford the knowledge the geologist requires; but here the round-backed plateau and loftiest elevation are so loaded with detritus of sand, clay, and fartransported blocks, that inspection of the concealed strata can seldom be obtained, except in the deep ravines which are daily forming on the sides of the valleys, or on the banks of rivers, where the subsoil is laid bare by denudations. The water-courses are, therefore, as truly the keys of the internal structure and mineral wealth of Russia as they are the sinews of her commercial intercourse.'—vol. i. p. 22.

The

The northern portion of this huge region to the south of the primordial and crystalline rocks is occupied, as we proceed southwards, by Silurian, Devonian, and Carboniferous deposits-the two last-mentioned formations occupying tracts infinitely larger than the British Isles, whilst to the east they are succeeded by another still more widely-spread accumulation, the Permian, which, ranging from the Asiatic steppes in 52° N. lat. to the icy sea, and from the backs of the Volga to the Ural mountains, occupies a trough of more than twice the dimensions of France! All the deposits above named belong to the great Palæozoic or earliest division of the geological series; but besides these, the surface of broad tracts is occupied by shales and sands containing an entirely other order of animal remains, and belonging to the Oxfordian beds of the Jurassic or Oolitic group of the secondary rocks. With the exception of one carboniferous district between the Don and the Dnieper (the only one in Russia which contains coal worthy of notice), all the southern portion of the empire is occupied at rare intervals by Jurassic beds (also Oxfordian), by large breadths of chalk and other strata of that age, and by very extensive tertiary accumulations-which are only closed on the south-west and south by the Carpathians, the Balkan, and the Caucasusand which, extending to the south-east by the seas of Azof, the Caspian, the Aral, trend away into the inhospitable steppes beyond Chiva, and are probably only terminated by the mountains of Bokhara and Chinese Tartary.

If one leading object of the work be to develop with clearness the whole history of sedimentary succession from the dawn of creation to an epoch immediately anterior to the historical æra, another is to demonstrate how the deposits which in their virgin and unaltered state throughout the vast low region consist of slightly coherent sands, clays, and marls, are in the Ural mountains broken, elevated-and metamorphosed into talcose, micaceous, and chloritic schists and crystalline limestones, where they approach the igneous and eruptive axis of that chain.

In the endeavour to lay before our readers the more important points of the details now collected concerning the local history of these various formations, our fondness for methodical arrangement would naturally induce us to comply with the precept of our friend Rabelais, commencez par le commencement s'il vous plaît;' but this is in these days by no means so easy a task as it appeared in the good olden time of infant geology, thirty long years ago. Then we should unhesitatingly have described the granitic axes of our mountain chain, with the gneiss and mica slate into which they graduated by an easy transition, as the first and foremost terms of the whole series, των παλαιοτάτων παλαιότερα ;

but

but a change soon came over the spirit of our dream. The views first proposed by Hutton as to this igneous origin and eruptive or intrusive position of granite, though long scouted by the prevailing Wernerian school as extravagant heresies, ultimately became the established and orthodox faith of all catholic geologists; and this principally through the masterly re-examination by Dr. Macculloch of the same Highland districts which had suggested them originally. It was in the process of inquiry demonstrated, that in many instances eruptive volumes of granite had been protruded subsequently to the consolidation of the oolites and cretacea, and even late in the tertiary period; and beds of lias and lias shale, and even of more modern chalk, were shown to have been converted by the agency of these igneous masses into the saccharine marble once called primitive, and into mica slate; and this often in the very heart of the central axes of our mightiest mountain chains. M. Brochant, one of the first engineers who questioned the rights of primogeniture of those supposed legitimate monarchs of the globe, was modestly content to depose them only to the transition rank; and his countryman, D'Aubuisson, tells us—' Il ne s'arréte que devant le Mont Blanc et les grandes Alpes, retenu par un reste de considération pour leur ancienne prérogative de primordialité, et par cette élévation qui les place en premier rang parmi les montagnes de l'Europe;' but his successors, such merciless revolutionists as Elie de Beaumont, knew no such touch of pity or of shame; they pursued the work of degradation without scruple or remorse; they dragged forth liassic belemnites from the several recesses of the pretended primitive mica and chlorite slate, and demonstrated that the principal Alpine elevations took place in the tertiary epoch. The same recent origin has been proved for the Pyrenees by M. Dufrenoy, and for the Caucasus by M. Dubois de Montpereux. Fully admitting, however, the truth and importance of all these discoveries, we must still maintain that large districts of granitic and gneissose rocks have been restored by the present work, with demonstrative evidence, to their rightful dignity as the most ancient known portions of the earth's crust, and the fundamental base on which the earliest fossiliferous or protozoic deposits repose. We shall, therefore, on the present occasion, fearlessly follow Sir Roderick in beginning with these rocks, to which, from their priority to the deposits containing organic remains, he has assigned the title azoic.

This term he uses as synonymous with prozoic-i.e. before any known traces of animal life; expressing simply the actual fact, and without presuming to dogmatise, or to assert that nothing organic could then have existed. Under this denomination he

includes

includes all the crystalline and slaty masses belonging to the ancient group of gneiss, together with the ancient granitic and Plutonic rocks by which they have been invaded. He does not appear to believe it practicable to lay down any universally distinctive mineral character by which we may be able at once to discriminate with certainty between these prozoic igneous rocks and more recent eruptive and metamorphised groups. Although he concurs with Dr. Macculloch in considering the syenitic character (such as is shown in our Malvern and Mount Sorrell) as prevailing in the latter case, yet he admits the occasional existence of true granite as an intrusive rock of more modern date; but he grounds his distinction on the local fact of position, as actually ascertained. And on this evidence he pronounces the conclusion in favour of the antiquity of the Scandinavian gneiss. This consists of generally contorted laminæ of felspar, quartz, mica, and horneblende; it much resembles the same rock in our own Grampian mountains, and is in like manner penetrated by innumerable veins of a rose-coloured granite. In valleys and plateaus lying between the gneiss we now and then find local deposits of Silurian strata, which have been in their turn invaded by granites, porphyries, greenstone, and trappean rocks of a later era. We consider that important inferences may be deduced from this combination of igneous rocks of different ages in the same geographical site, to which we shall hereafter return. The junctions of these palæozoic districts with the subjacent gneiss, occasionally sustain his views: for he has given us sections in which we observe the fucoid sandstone and shales, the constant lowest term of the northern fossiliferous series, reposing unconformably on the truncated edges of elevated gneissose beds, or separated by strata of a recomposed rock derived from fragments of the gneiss itself. Mr. Lyell also, in his recent Travels in America, has recorded a similar instance, where a palæozoic sandstone called that of Potsdam (the recognised fossiliferous bed of the group answering to the lowest Silurian) reposes, unconformably, near the banks of the St. Lawrence in Canada, on the neighbouring gneiss, and includes enormous boulders, appa

*

Mr. Lyell's two thin octavos form one of the most interesting works we have lately read. They contain a résumé, equally clear and condensed, of all that is known of the geology of North America; but though more than half his pages are dedicated to the science he has so materially advanced. he has shown himself by no means an inattentive observer on subjects of more general interest. Some of his more discursive speculations on national institutions may probably be our text for an early article; passages from which, if we had not long ago been aware of his penchant for the more recent formations, we might have illnaturedly inferred that their writer already meditated a second visit to the great Pleiocene Republic. The whole book is full of acute thought, and it is very elegantly written: indeed, as to the merits of style he is facile princeps among our geologists.

VOL. LXXVII. NO. CLIV.

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