Aralo-Caspian or Steppe Limestone.-We consider as interesting in the highest degree that portion of their work in which our authors examine into the geological evidences of the idea first shadowed out by Pallas-that of a great eastern inland sea originally connecting together the Black Sea, the Caspian, and the Aral. They show that the mass of waters extended 300 miles to the north of the present limits of those seas; nay, probably far to the east over the deserts of the Ural, now inhabited by the Turkomans and the Kirghis; perhaps even to the foot of the mountains of the Hindoo Kush and Chinese Tartary; concluding that the mass was gradually reduced by convulsions which elevated, at successive periods, much of its original bottom above its level.

These views we regard as exactly exemplifying the ideas which we should attach to the geological period which has been named the newest Pliocene; an era in which the surface of the earth was passing, by gradual approximations, to its present configuration and distribution of land and water; and the geological agencies affected by these conditions were ultimately reduced to their actual state. The character, therefore, of these newer Pliocene deposits must vary with the varying minute relations of different localities. Where these relations are still maritime, the organic remains will be marine; where inland lakes were in preparation, the species will be those of brackish or of fresh water. The geological evidence, therefore, of this great inland brackish sea consists in a formation being spread over the whole of its old area, containing fossils analogous to, and in great measure identical with, those of the present Caspian; in which the univalves (with the exception of one doubtful species of Rissoa) are of freshwater origin, associated with forms of Cardiaceæ and Mytili, which are common to partially saline waters. The existing Caspian, we need hardly remark, has only a sixth part of the salt present in oceanic waters.

The first elevations connected with this series of events must have been the throwing up of the natural barriers which intercepted the communication between this inland sea and the western ocean of that day. The sea thus cut off would gradually become brackish; but for a time some accommodating marine species might contrive to live amid their new associates-as in the analogous case of the Lake of Stennis in the Orkney Islands, very recently converted from a salt loch to a fresh-water pool, marine Cardiacea and Mytili are found together with fluviatile Limneæ and Neritinæ. Evidences of such a transition state are found in the intermixtures of shells in the overlying miocene beds of the Crimea and at Taman, in the corresponding promontory on the east of the entrance of the Sea of Azof, where we have coral reefs VOL. LXXVII. NO. CLIV. 2 c

of

of Eschara lepidosa rising amidst shells of brackish water. An extinct herbivorous Cetacean (Cetotherium Rathkii) has likewise been found in the same locality. Similar indications are said to exist at other places on the western boundary of the Aralo-Caspian deposits, e. g., in Bessarabia, and around the Sea of Azof and the Black Sea-for this boundary must have been conterminous with the openings into the previous ocean; but throughout the eastern limits we find only the persistent types of a vast inland sea, considerably larger than the present Mediterranean.

The desiccation or rather reduction of this vast eastern Mediterranean must have resulted from at least two great movements of upheaval; by the first of which the limestones occupying the hilly coasts of the several resulting and detached seas were consolidated and left dry-so as to cut off the Aral; while the Black Sea, the Sea of Azof, and the Caspian, then covering the steppes of Astrakhan, still formed a continuous and magnificent expanse of waters-which were subsequently subdivided by a second elevation of large portions of their bottoms. The limestones of the first elevation, which of course must exhibit older deposits than those laid dry by the second disturbance, are distinguished on the map by a separate colour and number (10 and 10'). The one forms a zone curving in irregular flexures on the exterior of the other. Both present the same genera of shells-those which generally characterize brackish waters-but the elder presents several species not now known in the Caspian, while the latter closely agrees with the present sea. These great facts in the ancient physical geography of the globe, which are thus for the first time clearly placed before the public, must have a marked influence on the inductions of the philosophical geologist.

Final elevation of the crest of the Ural, and accumulation of auriferous Mammoth alluvia.-We hesitated whether we ought not at once to proceed from the evidences of this old farstretching Aralo-Caspian Sea on the south, to those phenomena accompanying the great northern drift, which attest that the Baltic on the north must in the same period have equally exceeded its present limits-extending from 700 to 1000 miles beyond them to the south and east; but as we shall see that the eastern side of the Permian trough, connected with the Ural chain and the opposite steppes of Siberia, had then been elevated above the sea, we entirely concur with Murchison in the opinion that the final convulsions which elevated the Uralian and Caucasian chains were probably contemporaneous with the expansions of the crust which affected the borders of these seas.

Now we have already seen that even before the deposition of the Permian beds the Ural district already was elevated into the

rocky

rocky shore of an ancient and probably low continent, skirting on the east the vast Western ocean in which these beds were deposited-and the rocks which constituted their conglomerates were abraded from these ancient shores, from whence also flowed the mineral streams which impregnated them with cupriferous salts: but these very circumstances afford proofs to our authors that the towering watershed of the present Úral could not then have been raised; for all the great masses of copper ore, and many of the rocks entering into the Permian conglomerates (porphyry, green stone, and Lydian stone), were found only on the eastern side of the chief ridge, which must therefore have effectually cut off their transference into the Permian ocean, had it already existed. As, on the other hand, no traces of platinum or gold occur in these western debris, it is concluded that these metals were only introduced into the chain during its most recent disturbances, when the highest peaks were thrown up, and the syenitic granites and most recent igneous rocks were erupted along its eastern slopes. Gold,' says Murchison (p. 475), was one of the most recent mineral productions in these regions anterior to the historic æra; and the auriferous debris were then collected in valleys which were tenanted by the mammoth and rhinoceros, and the bos urus. The original site of the gold (in one spot near Ekaterinburg) is in a dyke of a felspathic rock called beresite, associated with veins of quartz,* but it is generally perceived dispersed through an alluvium of coarse gravel entirely local, and derived from the neighbouring rocks. This alluvium is heaped on the top of the auriferous rocks in situ, at various other points on the east of the chain, usually in the vicinity of recent eruptive rocks.

The bones of mammoths and other extinct quadrupeds are dispersed through this auriferous gravel, just as in the ordinary gravels of the Thames, the Rhine, and the Danube, from which they differ in the interspersed particles of gold alone. The hollows containing these alluvia our authors conceive to have been ancient lakes, around which these extinct quadrupeds once roamed, and into whose bottoms their bones with shingle from the neighbouring rocks were washed for ages, and which were drained, and their barriers broken down, by some of the most

* Gold has also been found in other granitic and igneous rocks of central Siberia, and is occasionally even disseminated into clay slate in their vicinity. Platinum occurs in local alluvia of its own on the flanks of the chain; it appears from the rocks associated to have been drifted down from neighbouring peaks of hornblende, slate, serpentine, and greenstone (p. 484). Diamonds also have been found, though very rarely, in alluvia, and are supposed to be derived from a metamorphosed quartzose schist in the Ural. The rock is the same as that in which diamonds are found in the Brazils.

violent movements of elevation which gave rise to the present central watershed of the Ural (p. 492). The character of the soil covering the gravel, and the entire absence of marine shells, and of any trace whatever of the sojourn of the sea, authorize the conclusion that these depôts were lacustrine.

In proportion as we advance eastwards from the Ural, in the plains of Siberia, these bones increase in quantity, and are in still better preservation; and the farther the Siberian rivers are followed to their mouth this remark becomes the more applicable, until at length skeletons have been found entire, even with the flesh and hair adherent. The peculiar hairy covering of this fossil species of elephant, and the structure of its teeth-which, according to Owen, enabled it to browse on the coarser ligneous tissues of trees and shrubs*-may have qualified it to bear the climate and subsist in temperate and even moderate arctic latitudes; and it may have become finally extinct only owing to the last increase of cold depending on the most recent elevations of our mountains. Our authors conceive that they roamed over the plateaux extending northwards from the Altai, then lower than at present, and covered with forests; and that when the summer (even now in these regions intensely hot) advanced, they would naturally migrate to the embouchures of the great streams, and edges of the then Arctic Sea, which still covered all the low tracts of Northern Siberia. Here their carcases may have been drifted, occasionally to some distance, into what were then long estuaries— entombed in muddy clay at their mouths-and there on the increase of cold preserved almost intact (p. 500).

In Western or European Russia, in the central and southern provinces, we find in ancient drifts of sand and clay, often charged with fluviatile shells, remains of the ordinary European fauna of this period: the elephas primigenius (mammoth), rhinoceros tichorhinus, trogantherium, beaver, bear, and elk; besides peculiar and remarkable generic forms (exclusively Russian), the merycotherium and elasmotherium.

Our authors also remind us of the time when hordes of similar animals, associated with lions and hyenas, haunted the narrow slip which now forms our own island, reposed in caves or thronged around lakes in Yorkshire, or rambled on the borders of estuaries in Middlesex; but these phantasmagoric troops of the extinct beings of a former world come like shadows, so depart.'†

Block

Owen's British Fossil Mammalia, p. 261. There still roams undisturbed in a great Lithuanian forest, from remote ages a cherished preserve of the Polish kings, and kept intact by the Russian government, the enormous Bos Aurochs, of which we have now, by the Emperor's gracious attention to Sir R. Murchison's wishes, a splendid stuffed specimen and also a fiuely articulated skeleton

Block Deposits of Northern Russia, and Northern Drift.From the days when Saussure first directed our attention to vast blocks of granite, wafted in some inconceivable manner from the summits of the Alps across the Vale of Geneva to the highest ridges of the Jura, and when Sir James Hall reasoned more fully on the phenomenon of drifts of such transported materials and similar phenomena, interest has never abated. Every kind of hypothesis, possible and impossible, has been attempted for their solution. Diluvial debacles sweeping over the surface of the globe were resorted to-then glaciers existing where glaciers never could have been produced, and accomplishing what glaciers never could have performed; and if you would only admit a small snow-drift filling up the Vale of Geneva to the height of 5000 feet, everything was held to be satisfactorily explained.

By far the most remarkable of this class of phenomena is the vast accumulation of northern drift, as it is called, or of boulders, evidently derived from the Scandinavian hills, and dispersed over a space in Northern Germany and Russia, having a width from 400 to 1660 miles on the opposite side of the Baltic. Such is the great phenomenon which our authors undertake to illustrate; and we may confidently refer to the chapters in which they have done so, as presenting the richest storehouse of all the real information previously communicated on this subject by Von Buch, Brongniart, Sefström, Böhtlingk, Forchammer, Durocher, and others, combined with original observations and conclusions so important, that we believe future geologists will refer to them as a great authority on this subject. Our authors refer this dispersion to enormous waves of translation, produced by the final elevation of the Scandinavian peninsula to the additional height of perhaps only a few hundred feet in an ocean of 300 or 400 feet in depth surrounding it, and extending to a southern

skeleton in the British Museum; and Professor Owen has thus been enabled to identify the existing animal with a fossil species coeval with the mammoth, &c. The Emperor has also kindly undertaken that, if possible, a male and female shall be sent alive to our Zoological Gardens, which, if the thing be accomplished, will have what cannot be matched anywhere out of the Russian dominions. We wish we had room for Sir Roderick's picturesque description of this monster and its native forest, to which the peasantry attach ideas of the most mysterious reverence. None of the breed is ever killed but by the express order of the Emperor. The truly imperial preserve occupies about 150 English square miles.

*For a mathematical application of the powers of waves of translation, described by Mr. Scott Russell (Trans. Brit. Ass. 1844), to geological dynamics, see the very able memoir of Mr. Hopkins on the lake district (Proc. Geol. Soc. vol. iii. p. 763). In this he demonstrates that such waves excited in a sea of the depth specified by sudden vertical elevations, each not exceeding fifty feet, would have the power of hurling on enormous stacks of sand and gravel to vast distances and over considerable inequalities.

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