CHAPTER I

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GEOLOGICAL STRUCTURE OF FRANCE—BASIN OF PARIS. ORGANIC REMAINS.

On the continental side of the Channel it will not be necessary to dwell, in minute details, upon any of the systems of rocks which are here presented. What is France? The tourist will say—A two hours’ voyage from the sister isle—a salt lake separates them—a pleasure trip is the measure of their estrangement. The geologist will add—And when safely landed, one finds himself among the sights and objects, the rocks and fossils, which engaged his attention on the coast of Albion, the cliffs and downs of both countries being composed of the self-same materials.

I. THE PHYSICAL UNION OF FRANCE AND ENGLAND, although already adverted to, falls again to be noticed.

The geographical distribution of the respective rocks of France and Great Britain forms a remarkable coincidence in giving shape and contour to their general outline. Thus, the primary systems in both stretch along their western shores, presenting a vast barrier-wall of the oldest and hardest rock against the incessant encroachments of the Atlantic. Britanny and Normandy consist almost entirely of granite, gneiss, mica-schist, and silurian rocks; on these repose the upper suites of the secondary strata,—the lias, oolite, and chalk—training to the south and east. On the tertiary formations rest the secondary, narrowing in their basins, and preserving the same general line of bearing with the English beds, and in both cases reaching their maximum of thickness and exuberance of fossils around the capitals of Paris and London. The old red sandstone is not indicated on the maps, nor is it clearly ascertained to possess a habitat in the district in question. The coal-measures are of very limited dimensions, but in their due order of position at Hardinger, near Boulogne, and passing under the chalk and green sand, continue in an easterly direction by Valenciennes, Mons, Namur, and Liege, to Eschweiler, near Aix-la-Chapelle. The new red sandstone, of both divisions, is amply developed along the eastern boundaries from Semoy in Ardennes to Langrés and the borders of Switzerland. On the west again, the tertiaries prevail from the mouth of the Gironde to Bayonne on the Adour, where they are exposed to the constant tearing and erosion of the rude surges of the Bay of Biscay, while in the interior, and over the district of Auvergne, the granites and gneiss are widely overlaid by the overflowings of the most recent extinct volcanoes; the oldest and the newest plutonic rocks thus lying in immediate superposition and contact.

The rocks on this side of the channel are not indeed everywhere so well displayed, nor do they crop out with the same successive regularity as in Britain. Over extensive districts some disappear altogether, while in other places patches are seen lying out of their due order of superposition; not that in these instances the order is ever violated, but that some of the intermediate members seem to be wanting, and the remoter ones are in consequence found in contact. Still they conform to each other in their great line of section, and occupy the same constant relative position in their respective basins. Here, as in England, the Oolitic system embraces the Cretaceous, and extends in a larger semicircle round Paris as a common center, stretching from Ardennes to Normandy. The Lias, again, is inferior to the Oolite, and, filling a wider space, reposes on the transition slates of Virreville on the western coast. The Plastic clay, London Clay, and freshwater beds emerge in succession, and maintain each their corresponding dimensions. A remarkable grouping of rocks, illustrative of the order of superposition, occurs within the circuit of a few miles in the immediate vicinity of Boulogne, where resting upon the mountain limestone the following series may be observed: Coal, Oolitic marble, Purbeck and Portland stone, Iron-sand, Wealden clay, Chalk marl, Green sand, and Chalk. The Plastic clay reposes upon the chalk at Calais on the east of this group, and on the west stretches along the coast from Etaples to Treport.

The period during which the two countries continued to be united superficially, extended down at least to the last great upheaval of the bed of the ocean, subsequent to the Pleiocene deposits, and probably even after the establishment of the current epoch. The different formations we have been tracing are geologically connected over vast tracts of country; these tracts once formed basins or inland seas, into which their several suites of materials were drifted; the extensive regions of the older formations were amply fitted to inclose them; and, when the _uppermost_ or pleiocene series of the English beds were deposited, one and the same shores and waters must have been common to the two countries—to the now insular as well as to the continental basins of the closing tertiary age.

One feels a real and enhanced pleasure in his researches, and his speculations assume a wider and a loftier range, as he casts a glance back to the white shores of Britain, and around upon the aspect of the country before him, and sees that he is still treading the same soil, threading his way among the same rocks, ascending and descending the slopes and valleys of the same earthy accumulations, varied only by slight local causes. Embarked upon the Seine, and along the banks of that lovely river, there is laid open for inspection a series of deposits, with every one of which we are already acquainted. The resemblance is even more striking when we examine the vast undulating plains around, and find the depressions, elevations, hills, and general outline of surface all of a class; and when we observe also the rocky foundations beneath to be one and the same—extensions merely of the same series of deposits, and forming at no very distant geological period integral portions of one great continent.

Combined with the subterranean movements which occasioned the dislocations, and inversions often, of the strata on both sides of the channel, the action of oceanic currents and incessant beating of the waves may be looked to as the instruments which produced their severance. The proofs are ample of the encroachments of the sea upon the eastern coast of England, the sites of towns, villages, and extensive fields, as marked on maps, now forming sand-banks, islands, and marshy swamps. The promontories and cliffs of Yorkshire, Norfolk, and Suffolk are still, as they were in Pennant’s time, “perpetually preyed on by the fury of the German sea;” the whole site of ancient Cromer is now under its waves; the towns of Shipden, Wimpwell, and Eccles, have entirely disappeared; large manors and even parishes have, piece after piece, been swallowed up; nor has there been any intermission, from time immemorial, in the inroads of the sea along a line of coast twenty miles in length, in which these places stood.[9] The ravages, from the same cause, have been equally if not more violent on the shores of the channel, the Straits of Dover, and the whole south coast; where slips of enormous magnitude are frequently recorded, cliffs undermined, and lands of considerable extent carried into the sea. The Isle of Wight, the peninsulas of Purbeck and Portland, the promontories of Devonshire and Cornwall, have all received their shape from the destructive agency, as they are still preyed upon and consumed by the tides and currents to which they are incessantly exposed. The French coast bears similar testimony to the inroads of the sea. From Calais to Cherbourg, with its magnificent dock-yard, the line of shore is everywhere indented and stripped bare, the strata undermined, and huge masses toppling over the abyss or rising into lofty pyramids of the most grotesque and varied forms. Britanny lies open, on every side, to the full swell of the Atlantic, where very recent as well as more ancient history attests the ravages of the waters in the destruction of towns and woods, the inundation of whole parishes, the severance of the hill of St. Michael from the main land, and, according to tradition, in the obliteration of the south-western district, of unknown extent.

Familiarized to facts such as these, and their necessary deductions, the mind no longer startles at the notion of the former physical union of the two countries. The agency seen in operation is demonstrably adequate to the effect. The straits are narrow. Their greatest depth between Dover and Calais is twenty-nine fathoms. The bed throughout is composed of the same stratum of chalk-rock, while a submarine chain extending from Boulogne to Folkestone is only a few fathoms under low water. Accordingly the wave of the mighty “ocean stream,” parted on the western coast, met tide after tide on the opposite banks of the connecting peninsula or narrow tongue of land, the one portion winding round by the Orcades and rolling up the German Sea, and the other portion beating on the line of cliffs facing to the west. The softer sedimentary deposits of the tertiaries would rapidly yield to the constant erosive action; the harder strata of the chalk, bared and undermined, would speedily follow; and thus, in a period comparatively short, the entire mass would be carried away, and the gulf of separation be irrevocably effected.

As a proof that France and England were united, and that these operations were continued _within_ the human epoch, M. Desmarest, in his prize essay on this subject, proposed in 1753 by a society at Amiens, adduces the fact, that the noxious animals in both countries are identical, creatures which were not fitted to swim across the straits, and were not of a kind to be willingly introduced by man. But Desmarest in this only followed the views of an older writer, and from whose work, “Restitution of Decayed Intelligence,” all his facts and reasonings are obviously borrowed. This curious volume is the production of Richard Verstegan, written about two hundred and fifty years ago, and dedicated to James I. of Great Britain. The principal object of the author is to trace out the origin of the western nations, and more especially of “the most noble and renowned English nation,” as discoverable in their language and other antiquities. The fourth chapter of this quaint work is entitled, “How the Isle of Albion is showed to have been continent or firm land with Gallia, now named France, since the Flood of Noah.” Verstegan holds the doctrine that “in whatever manner and form it pleased Almighty God, in the beginning of the world, to divide the sea from the dry land, is unto us wholly unknown; but altogether unlikely it is that there were any _isles_ before the deluge;” and to this event he ascribes the disruption of much of the dry land and the formation of islands. The connection of France and England continued long after this, and their severance, he believes, was produced by the operation of existing causes. The narrow isthmus by which they were conjoined extended across the Straits of Dover, just as Africa is united to Asia by the Isthmus of Suez, or North and South America by the Isthmus of Panama. This isthmus was breached by the action of the sea on both sides, but the sea being _lower_ on the west side, the current swept with greater violence through this new channel, “toward the most huge Western Ocean, the greater divider of Europe and Africa, from the late found America.” He notices the identity of cliffs on the opposite sides of the straits, the submarine ridge which extends from Folkestone to Boulogne, the existence of marine shells all over the Netherlands and adjacent countries, and their consequent submergence before the sea was permitted to retreat through the new course produced in the isthmus, “and no way is there else to be found or imagined, whereby these seas might be drained or drawn away.” He refers to the identity also of the noxious animals in England and France, when our isle, continuing since the flood fastened by nature to the great continent, these wicked beasts did of themselves pass over; nor is the earthquake omitted by the writer, in his enumeration of causes whereby the sea, first breaking through, might afterward by little and little enlarge her passage; and the labor of man, too, had its share, when the inhabitants of the one side or the other by occasion of war did cut it, thereby to be sequestered and freed from their enemies.

Such is the train of illustration employed by Richard Verstegan, at a time when the state of the science of geology could furnish him with few helps; and but little indeed has been added by subsequent observers, except a few additional facts and inferences, which serve to confirm his conclusions. He remarks that such too had been the opinions of others, as of Antonius Volscus, Marius Niger, Servius Honoratus, the French poet Bartas, and our own countrymen, John Twin and Dr. Richard White; but these simply held the connection of the two countries as a matter of opinion, without laboring to find out “by sundry frequent reasons, that so it was indeed.”[10] England long dominated in France, crowned her princes Sovereigns of Navarre and the adjacent provinces, and Agincourt, Cressy, and Poictiers tell where man waged war against his fellow-man, over the remains of races long extinct, denizens of the same land, and propelled by instincts fierce alike for mastery or destruction. What a moral effect has been produced by the physical severance of the two nations, not only to themselves, but to the rest of the world! Great Britain, freed from the connection, can well afford to repose in peaceful majesty on her own shores, improving the arts, extending her commerce, and communicating, as the most noble and renowned nation the blessings of religion to the remotest parts of the globe.

II. ORGANIC REMAINS. There are three districts in France which claim the special consideration of the geologist. The first comprises the basin of the Seine, of which Paris may be regarded as the center; the second is the basin of the Loire, extending in the direction of the rivers Gironde and Adour; the third is the volcanic district of Auvergue, embracing the tertiary and lacustrine formations, which have excited much geological speculation. The Silurian beds of Britanny are in many places absolutely loaded with Trilobites, which have found an able expositor in M. Marie Rouault; and the New Red Sandstone, which skirts the Vosges mountains, is equally remarkable for the fossils, vegetable and animal, peculiar to the Permian system.

THE BASIN OF THE SEINE. The series of rocks included in this district, are described as the Paris basin formation, where, amidst their fossiliferous remains, the genius of Cuvier shone forth and captivated the world by his wonderful disclosures in the science of comparative anatomy. The deposits occupy a depression in the chalk upon which they rest unconformably, like those of the London basin: they agree generally in their organisms, but differ considerably in the quality of their respective materials. Blue clay with imbedded calcareous and argillaceous bands characterize the London formation, while that of Paris is distinguished by a superabundance of white limestones, marls, and gypsum. These rocks range over a vast extent of superficial area, being in their greatest length from N. E. to S. W. about one hundred and eighty miles, and from E. to W. about ninety miles. They belong to the Eocene period, consist of alternating groups of marine and fresh water strata, and have been arranged in the following order, according to the corrected diagram of M. Constant Prevost, who has considerably modified the earlier tabular arrangements of Cuvier and Brongniart:—Plastic clay, Calcaire grossier, Calcaire silicieux, Gypsum, Marls, Marine and fresh water strata.

_The plastic clay and sand_ consist of intercalating argillaceous and gritty beds, containing a considerable quantity of lignite and fresh water shells. This deposit is not continuous throughout the basin, nor is it always lowest in position. In some places it rests upon a marine calcaire grossier, and in other places it is mixed up and imbedded in it, clearly showing that a river charged with argillaceous sediment entered a bay of the sea and drifted down, from time to time, wood and fresh water shells. No remains of mammalia have been detected in the plastic clay reposing on the chalk. _The Calcaire grossier_ is composed of a coarse limestone, often passing into sand, and extremely rich in testacea, a locality near Gignon alone furnishing about four hundred distinct species. _The Calcaire silicieux_ is a compact silicious limestone, almost destitute of organisms, and from its strong resemblance to the precipitates of mineral springs, as well as the fact that the few fossils contained in it are all of the land and fresh water species, it is justly inferred that the deposit is of fresh water origin. _The Gypsum_, with its associated _Marls_, is a saccharoid rock of considerable thickness, and constitutes the hill of Montmartre and other elevations toward the center of the basin. Here occur the remarkable variety as well as abundance of those organic remains which have given so much celebrity to the Paris basin. Fishes, reptiles, crocodiles, tortoises, birds, bats, mice, squirrels, opossums, gigantic mammoths, Anoplotheriums, and palm-wood, are all interred in this receptacle of the extinct dead. The remains of about fifty species of quadrupeds alone have been detected in the deposit, some of them, to the minutest organ, in the highest state of preservation—all of them extinct—and nearly four-fifths belonging to a division Pachydermata or thick-skinned animals. Immediately above the gypseous formation is an oyster-bed, of great superficial extent; this is succeeded by beds of sand, entirely destitute of fossils, forming a suitable covering to the countless millions which lie interred beneath.

Reader! pause and reflect upon this enumeration of the rocky strata, and their contents, which compose the Paris basin. What vast accumulations, now of terrestrial floods, now of inroads from the ocean—here a deposit, testifying to the fact of some great inland lake, with huge monsters browsing on its banks or reposing in its shallows—there another, bearing witness to “the strength of a mountain river,” combating with the waves of an estuary, and each wearying of the conflict and mingling their spoils from land and sea in one common mass. Neptune is again triumphant, and leaves as the trophies of victory whole families and tribes of his own domains. Silvanus now asserts and establishes his reign, and the Genet, Raccoon, Opossom, the Squirrel, Woodcock, and Buzzard are there to proclaim his sway. The Nereids too had their doings, and both genera and species of seven extinct nondescript fishes show their powers. And, last of all, come the Naïads of the streams, presenting you with their offering in the Quail, Curlew, and Pelican, along with Tortoises and Crocodilians. Count and enter upon your list, as found in the gypseous formation alone, eleven or twelve species of the Palæotherium, an animal partaking of the respective structures of the rhinoceros, the horse, and the tapir; of the Anoplotherium five species, commingling the light and graceful form of the gazelle with the conformation of the camel; fifteen species of the Lophiodon, closely allied to the former, but partaking also of the qualities of the hippopotamus; seven species of the Anthracotherium, a creature whose dimensions through the various members of the family swell out from the size of the hog to that of the hippopotamus; the Chæropotamus, allied to the suidæ, and forming a link between the Anoplotherium and the existing Peccary; and, lastly, as closing the list of this remarkable race of thick-skinned animals, we are presented with specimens of the Adapis, of hedgehog appearance, but in size three times larger, and uniting in characters the insectivorous carnivora with the Pachydermata.

It is recorded of Newton, that, toward the close of his wonderful calculations, when it seemed that the arithmetical results were to be in harmony with the dynamical problem to be solved, when he felt on the verge of determining one of the most important laws ever discovered by man, and which forever would bind the heavens to the earth—the nerves of the calculator gave way for a time, and he was unable to finish his task. He called in the aid of a friend, pacing the room in tumultuous agitation while the few last terms were being added. It is impossible for any other mind to realize the intensity of the geometer’s feelings when the result was announced! Knowing how trifling a novelty will at times agitate the finest minds, no wonder need be that Newton was affected by an uncontrollable tremor, when he saw that the discovery was made and tested, not only of the law that binds together the particles of matter which compose our earth, but also that which unites the heavenly orbs in all their majesty with the simplest of terrestrial phenomena; and demonstrates that, over the descent of a leaf in the forest—the drooping of a blade of grass—a pebble tossed upon the shore—a mote rising and falling in the sunbeam—a drop issuing from the rain-cloud—there is the same regulating power as that which retains the planets in their orbits, and determines their course through infinite space. Cuvier, in simple but eloquent words, has recorded, in the Introduction to his “Ossemens Fossiles,” the state of _his_ feelings as he established his discoveries, and proceeded in his task of reconstructing his singular menagerie from the dry bones of Montmartre in the basin of Paris. “I at length,” he says, “found myself as if placed in a charnel-house, surrounded by mutilated fragments of many hundred skeletons, of more than twenty kinds of animals, piled confusedly around me; and the task assigned me was to restore them all to their original position. At the voice of comparative anatomy, every bone and fragment of a bone resumed its place. I cannot find words to express the pleasure I experienced in seeing, as I discovered ONE CHARACTER, how all the consequences which I predicted from it were successively confirmed; the feet were found in accordance with the characters announced by the teeth; the teeth in harmony with those indicated beforehand by the feet; the bones of the legs and thighs, and every connecting portion of the extremities, were found set together precisely as I had arranged them before my conjectures were verified by the discovery of the parts entire; in short, each species was, as it were, reconstructed from a single one of its component elements.”

Cuvier proceeded upon the principle, that every organized individual forms an entire system of its own, all the parts of which mutually correspond, and that none of these separate parts can change their forms without a corresponding change on the other parts of the same individual body. Where the viscera, for example, are so constructed as only to be fitted for the digestion of recent flesh, it is requisite that the jaws should be so formed as to fit them for devouring prey—the claws for seizing and tearing it to pieces—the teeth for cutting and dividing its flesh—the limbs or organs of motion for pursuing and overtaking it—and the organs of sense for discovering it at a distance. But under this general principle in the structure of carnivorous animals, the ingenious anatomist further discovered that there are several particular modifications, depending upon the size, the manners, and the haunts of prey for which each species is destined or fitted by nature; and that, from each of these particular modifications, there result certain differences in the more minute conformations of particular parts. Hence it follows, that there will exist distinct indications in every one of their parts, not only of the classes and orders of animals, but also of their genera and species.

Thus, in order that the jaw may be well adapted for laying hold of objects, it is necessary that its condyle should have a certain form; that the resistance, the moving power, and the fulcrum, should all have a certain relative position with respect to each other. To enable the animal to carry off its prey when seized, a corresponding force is requisite in the muscles which elevate the head; and this again gives rise to a determinate form of the vertebræ to which these muscles are attached, and of the occiput into which they are inserted. The teeth of a carnivorous animal require to be sharp, in proportion to the greater or less quantity of flesh that they have to cut; their roots to be solid and strong, in proportion to the quantity and the size of the bones that have to be broken; and these conditions of structure will necessarily influence the development and form of the several parts that contribute to move the jaws.

The strength of the claws, in like manner, and the mobility of the paws and toes, have a necessary relation to the forms of the bones in the feet, and the distribution of the muscles and tendons by which they are moved. As the bones of the forearm are articulated with the humerus, no change can be made in the form and structure of the former without occasioning correspondent changes in the form of the latter. The shoulder-blade also, or scapula, requires a correspondent degree of strength in all carnivorous animals, while the play and action of the several parts are dependent on the muscles which set them in motion, and the impressions formed by these muscles still further determine the forms of all these bones. Again, the shape and structure of the teeth regulate the forms of the condyle, of the scapula, and of the claws, in the same manner as the equation of a curve regulates all its other properties;—and, as in regard to any particular curve, all its properties may be ascertained by assuming each separate property as the foundation of a particular equation, in the same manner a claw, a shoulder-blade, a condyle, a leg or arm bone, or any other bone separately considered, leads to the discovery of the characters of teeth to which they have belonged; and reciprocally from the teeth we are enabled to discover the structure and forms of the other bones.

Thus, conducting his investigations by a careful survey of the bones and organs individually and separately, the skillful anatomist was enabled to reconstruct the whole animal to which they severally had belonged. The orders likewise and subdivisions of herbivorous, ruminant, hoofed, and cloven-hoofed animals, he determined with equal precision, and found to result from the same constant laws of organization. By employing the method of observation, where theory was no longer able to direct his views, Cuvier was furnished with other astonishing results. The smallest fragment of bone, even the most apparently insignificant apophysis, he found to possess a fixed and determinate character, relative to the class, order, and genus of the animal to which it belonged; insomuch that, when he observed merely the articulating extremity of a well-preserved bone, he could at once ascertain the species as certainly as if the entire animal had been before him. Proceeding after this method, assisted by analogy and exact comparison, Cuvier has been enabled to determine the fossil remains of seventy-eight different quadrupeds, in the viviparous and oviparous classes. Of these, forty-nine are distinct species hitherto unknown, twenty-seven of which are referable to seven new genera, and the other twenty-two new species belong to sixteen genera, or sub-genera, already known; while the whole number of genera and sub-genera, to which the fossil remains of quadrupeds investigated belong, are thirty-six, including those both of known and unknown species; some hoofed animals not ruminant, and some ruminant—others _gnawers_ and others carnivorous—two, of the sloth genus, toothless—and two, amphibious animals, of two distinct genera.

Such are the triumphs of science, which always lead to a profounder admiration of the works of Nature, in the immensity and constancy of those laws that have prevailed through all time, and where her wisdom and foresight are demonstrated by a series of systematic contrivances and mutual adaptations to which she invariably adheres. In the remote invisible depths of space, slight oscillations have from time to time been detected, and following up the researches, astronomy, as announced beforehand, is rewarded by the discovery of a new planet. The earth gives up its dead, entombed for ages in its stony matrix. At the bidding of science their figures are restored, their habits determined, their very food ascertained, their characters for ferocity or otherwise brought to light, and they are all, each after their kind, called by their names. What a mastery in all this over the extinct forms of organic nature, as Newton manifested in a different way in his wonderful deductions and calculations respecting the molecules of inorganic nature and the physical heavens!

III. The Paris basin, which consists of the lower or eocene series of the tertiary system, is inclosed nearly on all sides by the middle or miocene group of strata. These, however, are most fully developed along the district of the Loire and its tributaries, as the former are chiefly confined to the water-shed of the Seine and the environs of Paris. We thus advance a step upward in the Course of Creation, while so far as geology has been able to mark the progress, the last stages of the stupendous work, prior to the introduction of its noblest inhabitant, are to be discovered in the PLEIOCENE deposits that immediately succeed, stretching over the western shores from Bordeaux to Bayonne.

THE BASIN OF THE LOIRE. The rocks which compose these upper layers of the earth’s crust, have all a family resemblance to the tertiaries already described. In the district of the Loire the _miocene_ beds consist generally of quartzose sand, gravel, and broken shells, mostly loose and earthy, but in many places agglutinated by a calcareous or ferruginous cement, so as to be fit for building purposes. The “faluns,” as they are provincially termed, resemble the crag of England, abounding in shells, and mammiferous remains incrusted with serpulæ, flustra, and balani, The deposit is seldom above seventy feet in its greatest thickness. Betwixt Sologne and the sea, patches are found to rest successively upon gneiss, clayslate, the coal-measures, Jura limestone, greenstone trap, chalk, and the upper beds of the eocene series. The _pleiocene_ beds are not materially different in their lithological characters from those of the miocene group: blue clays, marls, and osseous breccias are among the prevailing strata; and siltings of sand and gravel, only distinguishable by their organic remains from the alluvia and superficial drifts of the current era. Volcanic products are often largely mixed up with these pleiocene beds, and in districts where, in addition to the fossil evidence, they clearly establish that they belong to the class of extinct volcanoes, as the sedimentary deposits are themselves determined to belong to the pleiocene age.

[Illustration: Restored Form of Dinotherium.]

The interesting peculiarity connected with these two groups of the tertiary system is, that here all animal as well as vegetable life approaches a step nearer to the existing family types. Analogous species of molluscs are more numerous, the testacea in many instances being identical with those of our modern seas. The mammalia are likewise more akin to those of our domesticated tribes, where the horse is strikingly prefigured in the hippotherium, the dog in the agnotherium, and the cat in feline forms as large as lions. The glutton and the bear have also their compeers, nor are the fox, hare, and mouse, without their representatives. But the marvel of the formation is the DINOTHERIUM or gigantic tapir, whose dimensions in every organ and member are stupendous. The dinotherium was seemingly possessed of powers which enabled him at once to exercise the digging propensities of the mole and amphibious habits of the walrus, a trunk projecting nearly as long as that of the elephant, and two enormous tusks depending from the lower jaw. This animal was partly terrestrial and partly aquatic, and hence, says Dr. Buckland, the tusks may also have been applied to hook on the head to the bank, with the nostrils sustained above the water, so as to breathe securely during sleep, while the body remained floating at ease beneath the surface. Thus would he repose, moored to the margin of a lake or river—the huge body, of eighteen feet in length, with a corresponding thickness, indolently basking in the sun-beams, or quietly cooling after exertion in the limpid wave—and these enormous tusks, ready to release him at a bound, when attacked by the enemy beneath. The dinotherium existed during the miocene period, and constitutes an intermediate link between the tapir and the mastodon. It has left abundant remains in the basin of the Rhine, in Bavaria and Austria, and in several districts of the formation in France.

The tertiaries have a wide geographical distribution, and cover a vast extent of superficial area. Stretching from the Rhone to the Danube, they are found in every part of central and southern Europe, along the Julian Alps, and over the interior of Italy, from Ancona to Turin. The eocene group is ascertained, from the character of its fossils, and especially by its nummulites and echinoderms, to extend from the Mediterranean, through Egypt, Asia-Minor, and Persia, to Hindostan, and there to occupy large regions forming the western and northern limits of British India. This enormous mass of tertiary strata was drifted into lakes or estuaries, whereby the mind is carried back to a period when Europe was chiefly lacustrine, and all these countries eastward were as yet submerged in their waters. What explanation can geology give of their elevation to the surface? A scene of volcanic agency, now and _before_ the modern epoch extinct, remains to be noticed, which in part at least will furnish a probable solution of the changes then in operation or completed.

CENTRAL FRANCE, consisting of the districts of Auvergne, Velay, and Viverais, is universally admitted by geologists to be of volcanic origin. The most cursory glance at the dome-shaped hills, the basalt, trachyte, and scoriaccous ingredients of which they are composed, at once satisfies the student of nature as to the class of rocks among which he here treads. This region lies upon the river Rhone, nearly in the angle formed by it with the Mediterranean, and covers an area of forty or fifty leagues in diameter. Here are associated, perhaps, the earliest and the latest products of Plutonic action, the primary granites, and the basaltic lavas of comparatively recent times. The granite is flanked on the south and west by immense overliers of gneiss. It may be described as the highlands of the country, whence all the great rivers, the Seine, the Loire, the Gironde, and their principal feeders, take their rise. The mountains, though not remarkable for elevation, now that we are approaching true Alpine peaks, reach the height of four, five, and six thousand, and the Aurillac group to nearly seven thousand feet above the level of the sea; but what a geological series of events is embraced within the period of their physical history! The great depository arrangements of the globe have, one and all, succeeded to those paroxysmal movements that raised their tops above the primeval seas. Race after race of living creatures have enjoyed their span of existence, to be mixed up with the strata which during the interval have been collected and arranged in their various systems. The crust of the earth from time to time was disrupted. The depressions and fissures were as repeatedly replaced with new matter. The tertiary period dawned upon Creation, when plain, lake, and seas, were all teeming with an exuberance of terrestrial and aquatic life,—and when again all in the region of Central France was disturbed, and these newer molten rocks were erupted from beneath. The subterranean fires, wherever seated, were thus, after the lapse of geological epochs, still glowing with intense vigor. And, just bordering on the advent of man, the two classes of rocks would seem to have been placed in the closest proximity, as if to remind him, that the same Omnipotent agency which created every single atom of his earthly habitation, likewise determines every movement and advance of the structure, and makes the near and the remote equally manifest the thunder of his power.

There cannot exist a doubt that the district in question was the seat of an extensive chain of lakes, imbosomed amidst the primary rocks, and silted up during the currency of the tertiary age, partly by sedimentary and partly by igneous matter. The unstratified masses which encircled their waters, still stand out in bold relief from the well-defined strata that now occupy their basins. A walk up any one of these valleys—and they are innumerable—or among the cones, hundreds of which are scattered over the high grounds in the vicinity of Gergovia, will present to you in striking contrast these extremes of natural masonry. One can almost trace, in some localities, the very fissures which opened in the sides of the granite rocks, whence issued the molten flood that first perturbed the waters of the pure silent lakes. No straining of the imagination is indeed required to trace the whole progress of their silting—now in the dark lava-current from the bowels of the earth, and now in the collected debris from the mountain sides, hurried down by the torrent or by their own convulsive throes—here the fine comminuted sand, gently carried in by the stream, and there the waste of animal life forming entire beds of calcareous marls of still unsullied freshness. In the whole range of geology there is not, in fact, to be found anything more instructive and interesting than is displayed in these lacustrine deposits, the extreme thinness often of the beds, and the beautiful regularity of their superposition. The lavas intermix, and alternate repeatedly, with the alluvial and organic strata. A myriad of trickling rills fling themselves from the upheaved ridges, so green and flowery to their summits; they are collected into streams in the different ravines, and sweeping through the deep-cut gorges, lay open the interior to the depth of many hundred feet. Here the various igneous and aqueous groups can be read and studied in detail, as they were quietly deposited or violently strewn upon one another.

The hill of La Roche, in the Puy de Jussat, presents a face of a variegated quartzose grit of nearly seven hundred feet in thickness. At Chamalières, near Clermont, the same deposit is equally well exposed. Green and white foliated marls are very abundant, attaining a thickness sometimes of six to seven hundred feet, and consisting chiefly throughout this immense depth of the shells of _Cypris_, a genus which comprises several species, some of which are recent, and still existing in the waters of our stagnant pools and ditches. The structure of these beds, in this volcanic region, is as remarkable as the materials of their composition. The strata divide into plates thin as paper, which are piled up into laminated masses of several hundred feet, of various colors, but the white and green prevailing, and the whole sometimes covered by rocky currents of trachytic or basaltic lava. Gypseous marls, similar to those of Montmartre, have also contributed to the silting up of the lakes, where, as at St. Romain, they are worked, and extensively used for ornamental purposes. A remarkable deposit occurs among the series, termed the _indusial limestone_, from the circumstance of its containing the cases or _inducia_ of a tubular-form species of insects; a creature that not only assisted individually toward the increment of the rock, but possessed the power, like its existing analogues, of attaching to its body a load of shelly molluscs, in some cases no less than a hundred of these minute shells being arranged around one tube, while ten or twelve tubes are packed within the compass of a cubic inch. Some beds of this limestone are six feet thick, and may be traced over a considerable area, showing the countless number of insects and molluscs which contributed their integuments and shells to compose this singularly constructed rock. The fibular coralline rocks of the Keelan islands bear some faint resemblance to these ancient organic deposits, where the insects build from beneath, and gradually mount to the surface of the ocean when their work is done, and they perish. The _Phryganeæ_ of the tertiary age enjoyed their brief hour in the sunshine, fulfilled their destiny, sank into the waters, and contributed to form rocks over their bottom. They weaved not, like the existing races of builders, their own shroud, though the materials in which they are entombed are mainly of their own construction—concretionary plates of the finest texture, and indestructible as marble.

The lacustrine deposits in the department of the Haute Loire are nearly identical with those now described, but concealed very much by the lava and scoriæ that have flowed out in immense quantities in the trough of the river. The best sections are exposed near the town of Le Puy, where the sedimentary and erupted rocks are beautifully interstratified. The Aurillac basin, in Cantal, is filled with similar materials, although there is a greater proportion of silicious strata mixed with the calcareous marls. Indeed, so much in this district does the silex predominate, that a bed of tertiary limestone is covered with nodules of flint, and resembling in appearance the upper chalks of England. The fossil remains, however, clearly mark the distinction, where we have the shells of the _Planorbis_ for those of the _Echinus_, and other fresh water testacea instead of the marine types of the Cretaceous formation.

IV. GENERAL CONCLUSIONS. This district has been the theater of great volcanic action. The epoch of its activity is clearly determined by the undoubted tertiary character of the formations with which its porous lavas and scoriæ are intermixed. Basalts and trachytes, of the same age, texture, and qualities, are to be found in the various countries through which the deposits have been traced. The granites, porphyries, and greenstones we have seen successively employed in raising up the symmetrical rocks of the grand palæozoic systems, and thereby giving shape, stability, and access to the economic and gradually-augmenting volume of the crust of the globe. Can we see in these last extinct throes of the interior, the operations of the same great FINAL CAUSE—the overruling hand of power, wisdom, and goodness in the mineral arrangements and diversified ingredients of our earthly habitation?

Take a glance at the extent and geographical situation of this family of rocks. Everywhere among the Andes and Cordilleras, there are evidences of the elevation of large mountain-tracts, through the agency of volcanoes now extinct, and probably of the age in question. A volcanic region in the north of Spain, extending over twenty square leagues, from Amer to Massanet in Catalonia, is situated among the lower beds of the system, penetrating a nummulitic limestone and other strata, conjectured to belong to the age of our green sand and chalk. The Drachenfels on the Rhine and the Eifel chain of hills near Bonn, are likewise referable to this class of volcanic ejections. The Katakekaumene tract of mountains, in Asia-Minor, is composed of comparatively recent volcanoes, where Mr. Hamilton conceives the great cones of Mont Dore, the Cantal, and Mont Mezen in central France are represented by Ak Dàgh, Morad Dàgh, the trachytic hills east of Takmak, Hassan Dàgh, and Mount Argæus. Similar eruptive indications have been traced by Mr. Grant in the district of Cutch, situated near the eastern branch of the Indus, and consisting of large tracts of tertiary deposits. The elevated regions of the Tyrol, the flanks of the Bernese and Swiss Alps, have been the scene of violent disturbance, during and since the deposition of the tertiary formations; and, in the peninsula of Italy, there are numerous groups of volcanic origin, as in Tuscany the igneous rocks of Radicofani, Viterbo, and Aquapendente, and those of the Campagna di Roma, which are of the same chronological series, or probably not later than the pleiocene period. The West India Islands, the Azores, Iceland, Owhyhee where the peaks of Mauna-Roa and Mouna-Kaa rise to the height of between 15,000 and 16,000 feet above the sea, belong to the same class of phenomena. Thus in every quarter of the globe there have existed Phlegræan fields of ancient as well as of modern date, whose convulsions anterior to all historic records are still traceable in the submergence and closing up of lakes, the drainage of large tracts of land, the upheaval of mountains, and the reduction of the earth to existing superficial arrangements.

The products of these tertiary extinct volcanoes are indeed vastly inferior in amount to the ejections of the more ancient periods, whose stupendous monuments are seen in the primary and secondary mountain-chains of granite, porphyry, and greenstone; but still they had force enough to influence very extensive tracts of country, to convulse and move large portions of the crust of the earth. Even now it is impossible to guess through how wide an extent, in the subterranean regions, the shock of earthquakes is simultaneously felt. Not less than 100,000 square miles of country were permanently elevated by the Chili earthquake of 1822, from two to six feet above its former level, and part of the bottom of the sea remained dry at high water, with beds of oysters, muscles, and other shells adhering to the rocks on which they grew. The contemplation of volcanic phenomena in South America, has led Mr. Darwin to remark that, in order to comprehend the vast surface which was affected by the earthquake in Chili, and which destroyed Conception, in February 1835, it had a north and south range equal in extent to the distance between the North Sea and the Mediterranean—that we must imagine the eastern coast of England to be permanently raised, and a train of volcanoes to become active in the southern extremity of Norway—also that a submarine volcano burst forth near the northern extremity of Ireland—and that the long dormant volcanoes of the Cantal and Auvergne, each sent up a column of smoke. It need, therefore, excite no wonder that geologists have felt themselves warranted to ascribe the elevation not only of the sedimentary formations in central France to the volcanic movements of the district, but likewise those of the Paris and London basins, as well as the general rise and dislocation of the strata along the southern and eastern coasts of England. The cause, as compared with recent and still daily observed phenomena, was abundantly adequate to effect the results. Other districts would be simultaneously influenced; the tertiary deposits in their various successive groups were all arranged under similar circumstances and exposed to similar changes; and hence a doubt can scarcely exist, that all these geological basins, and this vast superficies of tertiary matter, were cotemporaneously elevated, as well as subjected to one and the same range of subterranean convulsion.

As an approximation to the period when this district was last subject to volcanic action, it may be noticed that the craters of Auvergne and the Cantal had all ceased to emit fire or were just expiring, when those of Etna and Vesuvius _began_ their operations. From whatever cause, it would appear that the incandescent elements had here parted with their caloric or had shifted their position, and that new vents were opened for them in the basin of the Mediterranean. These latter volcanoes may have been in activity _before_ the historical epoch, although the evidence must still be regarded as inconclusive, and the violent efforts to fasten a collision upon revelation have utterly failed. But in Auvergne, on the contrary, little doubt exists of the priority of all the volcanic emissions to the human epoch. When Cæsar encamped among these narrow defiles, his Commentary is silent as to any eruptions save the irruption of his own legions. The inhabitants, as now, were cultivating the vine or peacefully engaged in rural occupations, as little dreaming of any disturbances from the interior, as they were unprepared to resist the torrent of mail-clad warriors that poured through their valleys and devastated their fields. The poet Sidonius Apollinaris had his residence on the borders of Lake Aidat, but he sung not of the “sublime” in these upthroes of his native province. Nevertheless, an immense degree of historic interest must ever attach to these volcanic rocks, inasmuch as they are infinitely modern when compared with the primary and secondary formations, the granites and the traps of Britain. They keep continually, too, before our eyes the fact of a succession of igneous operations, and remind us that plutonic agencies have prevailed through all time, and over regions which have only recently been liberated from their ravages; that at any moment, and at any place, they may again burst forth, when islands will be raised, continents submerged, the fertile plain laid waste, and lakes, estuaries, and seas converted into dry land.

Nor are there evidences wanting, in existing volcanoes, of the intensity of the fires which still glow within the interior of our earth. There are at present more than TWO HUNDRED volcanoes in active operation; these are not confined to any particular zone, but are distributed like those of the older families through the different quarters of the world. The greater centers of action are situated in the mountain-ranges of South America, along the western coast of North America, and in the numerous islands of the Southern Pacific; but at the same time there is scarcely a portion of the earth’s crust that is not subjected to the shock of volcanic influence and the movement of earthquakes. There are two theories by which all volcanic phenomena are attempted to be explained. The more prevailing one among geologists is that which connects them with one great source of central heat—interior lakes of molten stone—the residue of that incandescent condition in which the globe originally appeared, and out of which the primary crystalline strata were formed. The other mode of explanation is that which supposes the internal heat to be the result of chemical and galvanic action among the materials composing the earth’s crust. The metallic and earthy bases, upon contact with water, everywhere transmitted through fissures and apertures on the surface, burn, melt, and are converted into lavaform matter, and which acting again as fuel, serve to fuse the rocks among which they occur. Hence various gases will be generated sufficient to occasion much local disturbance; though certainly not upon a scale to correspond with the magnitude, universality, and perpetuity of those changes that have resulted in the igneous products of the primary, secondary, or even tertiary formations.

But whatever be the source or cause, the heat and the elements of heat have been in constant activity, volcanoes and earthquakes, like the hurricane and disease, subserving important necessary purposes in the economy of nature. Humboldt was the first to remark the linear distribution of volcanic domes, which he considered as vents placed along the edge of vast fissures, communicating with reservoirs of igneous matter, and extending across whole continents. Lyell, considering that the earthquake and the volcano are probably the effects of the same subterranean process, and that the subterranean movements are least violent in the immediate proximity of volcanic vents, observes, “that if the fused matter has failed several times to reach the surface, the consolidation of the lava first raised and congealed will strengthen the earth’s crust, and become an additional obstacle to the protrusion of other fused matter during subsequent convulsions.” Thus, needful in all past time, these igneous phenomena are needful still—in supplying and indurating new lands—in repairing the waste and continual encroachments of the sea—in keeping up a salutary degree of heat over the earth’s crust, and thereby perhaps essential toward maintaining the necessary volume of the earth’s bulk. Nor will the fires within have fulfilled their law and purpose of inclosure until the ordinance of Heaven in its creation be completed, when the earth and the works therein shall be burnt up.

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