Chapter II: Preface (2)

But, in the numerous strata that overlie the rocks of granitic origin, there are found, in varying abundance, proofs that, when they were deposited, the surface of our earth had become the abode of organic life. Zoophytes lived in the ocean, some of which were engaged in secreting lime from the water, and depositing it in coral-reefs; stalked and jointed Star-fishes waved like lilies of stone from the submerged rocks; Sea-worms twined over the mud; mailed Crustaceans swam to and fro; and Mollusks, both bivalve and univalve, crawled over the ledges or reposed in the crevices. The remains of these occur in the Silurian rocks that lie immediately on the primitive granitic formations of Cumberland and North Wales. The construction of the coral-reefs of that deposit, in particular, must have occupied a lengthened period, continuing to go on, "month after month, year after year, century after century, until at length the depth changed, in which they could most conveniently live, or, owing to some other cause, their labours were brought to a close, and they disappeared from amongst existing species."[26]

(_Calymene Blumenbachii._)

_a._ extended; back view. _b._ rolled up; side view. _c._ rolled up; front view.]

Not a single species, or even a single genus of those early strata, is identical with any that exists now. The Coral-polypes, for instance, while allied to ours, are quite distinct from them, though endowed with similar powers and habits, so that we may reason from analogy on the laws of their deposits. The Trilobites were allied to the tiny water-fleas (_Entomostraca_) of the present day: like the _Oniscidæ_ (wood-lice, buttons, &c.) of our gardens, they had the habit of rolling their plated bodies into a ball. These are found in great numbers, their remains often heaped on one another. The Mollusca of those seas were chiefly of the class _Cephalopoda_--one of the least populous now-a-days, but then existing in vast number and variety; the Brachiopoda, Conchifera, and Gastropoda, were, however, well represented also.

Such were the inhabitants of the sea during the Silurian period, in which a series of solid deposits were made, the aggregate, probably, exceeding 50,000 feet in thickness. Each deposit, though not more than a few inches in depth, "is provided with its own written story, its sacred memoranda, assuring us of the regularity and order that prevailed, and of the perfect uniformity of plan."

Over all these, however, we see laid the strata of the Devonian system, especially the old red sandstone, which in some places attains a thickness of 10,000 feet. It is composed of a coarse agglomeration of broken fragments of the old granitic rocks, rolled and tossed about, apparently by the ever-breaking waves of shingle-beaches, until the hardest stones are worn into rounded pebbles by long and constant attrition.

An examination of the old red sandstone, as is seen in Herefordshire, will aid us in forming a notion of the time required for its production. It is composed of fragments obtained by the disintegration of more ancient rocks, which, by a long process of rolling together in a breaking sea, or in the bed of a rapid current, have lost all their angles. The pebbles, thus worn, have at length settled,--the heaviest lowest,--and the whole has been consolidated into firm rock. "In many places," says Dr. Pye Smith, "the upper part of this vast formation is of a closer grain, showing that it was produced by the last and finest deposits of clayey and sandy mud, tinged, as the whole is, with oxides and carbonates of iron, usually red, but often of other hues. But, frequently, the lower portions, sometimes dispersed heaps, and, sometimes, the entire formation, consist of vast masses of conglomerate, the pebbles being composed of quartz, granite, or some other of the earliest kinds; and thus showing the previous rocks, from whose destruction they have been composed. Let any person first acquire a conception of the extent of this formation, and of its depth, often many hundreds, and, sometimes, two or three thousand feet; (but such a conception can scarcely be formed without actual inspection;) then let him attempt to follow out the processes which the clearest evidence of our senses shows to have taken place; and let him be reluctant and sceptical to the utmost that he can, he cannot avoid the impression that ages innumerable must have rolled over the world, in the making of this single formation."[27]

Here, Fishes are added to the Invertebrate Animals. A sort of Shark with the mouth terminal, instead of beneath the head, was the earliest representative of this class. But closely following on this, were some curious species, enveloped in plate mail, and remarkable for the singularity of their forms, as the _Cephalaspis_ and the _Pterichthys_.

This great period passed away, and was succeeded by that of the Carboniferous deposits, indicative of a vast change in the physical character of the earth's surface and atmosphere. This change of character may be briefly summed up as consisting of an immense abundance of lime in the ocean, and of an equally vast charge of carbonic acid in the atmosphere.

Strata of limestone, 2,500 feet in thickness, were accumulated in the ocean by the labours of Coral-polypes, allied to, but totally distinct from, those which had previously existed in the primary system. On the floor of a shallow sea, which then occupied the middle of what is now England, the coral reefs rose perpetually towards the day, atom by atom, the strata on which they were founded slowly and steadily sinking ever to a lower level, while successive generations of the industrious zoophytes wrought upwards, to maintain their position within reach of the light and warmth. What period of time was requisite for the aggregation of coral structure to the perpendicular thickness of 2,500 feet?

While this was going on, other Invertebrata were living in the shallow seas, mostly differing from the older species, which had become by this time extinct. Encrinites and Sea-urchins existed; some _Foraminifera_ were astonishingly abundant; the _Cephalopoda_ and the _Brachiopoda_ presented a vast variety of species; and about seventy sorts of Fishes, mostly Sharks, characterised the age.

On the coral limestone lies a sort of conglomerate, known as the millstone grit; and on this is laid that source of Britain's eminence, the _coal_. The coal measures of South Wales are estimated at 12,000 feet in thickness. The profusion of vegetable life that must have combined to make the coal in these, has no parallel in this age; no, not in the teeming forests of South America, or the great isles of the Oriental Archipelago. The circumstances which favoured this enormous development of plants, seem never to have been repeated in subsequent ages, since the coal measures which are found in the later strata are thin and inconsiderable, compared with those we are considering.

M. Adolphe Brogniart suggests that in this period, from some source or other, carbonic acid was generated in vast abundance; or, at least, that it existed in the air, in a far greater proportion than it does now; and it is singularly confirmatory of his view, that terrestrial animals, to which this gas is fatal, have left almost no traces of their existence, during the age of these vast forests--a circumstance otherwise strange and unaccountable.

"Those parts," says Mr. Ansted, "of the great carboniferous series which generally include the beds of coral, consist of muddy and sandy beds, alternating with one another, and with the coal itself. Some of them would appear to be of fresh-water, and some of marine origin; and they abound, for the most part, with remains of the leaves of Ferns and fern-like trees, together with the crushed trunks of these and other trees, whose substance may have contributed to form the great accumulations of bituminised and other vegetable carbon obtained from these strata.

"It is not easy to communicate such an idea of beds of coal as shall enable the reader to understand clearly the nature of the circumstances under which they may have been deposited, and the time required for this purpose. The actual total thickness of the different beds in England varies considerably in different districts, but appears to amount, in the Lancashire coal-field, to as much as 150 feet. In North America there is a coal-field of vast extent, in which there appears at least as great a thickness of workable coal as in any part of England; while in Belgium and France the thickness is often much less considerable, although the beds thicken again still further to the east.

"But this account of the thickness of the beds gives a very imperfect notion of the quantity of vegetable matter required to form them; and, on the other hand, the rate of increase of vegetables, and the quantity annually brought down by some great rivers, both of the eastern and western continents, is beyond all measure greater than is the case in our drier and colder climate. Certain kinds of trees which contributed largely to the formation of the coal, seem to have been almost entirely succulent, and capable of being squeezed into a small compass during partial decomposition. This squeezing process must have been conducted on a grand scale, both during and after the formation of separate beds; and each bed in succession was probably soon covered up by muddy and sandy accumulations, now alternating with the coal in the form of shale and grit-stone. Sometimes, trunks of trees caught in the mud would be retained in a slanting or nearly vertical position, while the sands were accumulating round them; sometimes the whole would be quietly buried, and soon cease to exhibit any external marks of vegetable origin.[28]

"To relate the various steps in the formation of a bed of coal, and the gradual superposition of one bed upon another, by which at length the whole group of the coal-measures was completed, would involve an amount of detail little adapted to these pages; and when it is remembered that the woody fibres, after being deposited, had to be completely changed, and the whole character of the vegetable modified, before it could be reduced to the bituminous, brittle, almost crystalline mineral now dug out of the earth for fuel, it will rather seem questionable whether the origin of coal was certainly and necessarily vegetable, than reasonable to doubt the importance of the change that has taken place, and the existence of extraordinary means to produce that change. Nothing, however, is more certain than that all coal was once vegetable; for in most cases woody structure may be detected under the microscope; and this, if not in the coal in its ordinary state, at least in the burnt ashes which remain after it has been exposed to the action of heat, and has lost its bituminous and semi-crystalline character. This has been too well and too frequently proved by actual experiment, to require more than the mere statement of the fact."[29]

An eminent practical geologist thus essays to guess the age of the coal-fields, and of the sandstone that underlies it.

"The great tract of peat near Stirling has demanded [for its formation] two thousand years; for its registry is preserved by the Roman works below it. It is but a single bed of coal. Shall we multiply it by 100? We shall not exceed,--far from it,--did we allow 200,000 years for the production of the coal-series of Newcastle, with all its rocky strata. A Scottish lake does not shoal at the rate of half a foot in a century; and that country presents a vertical depth of far more than 3,000 feet in the single series of the oldest sandstone. No sound geologist will accuse a computer of exceeding, if he allow 600,000 years for the production of _this series alone_. And yet what are the coal deposits, and what the oldest sandstone, compared to the entire mass of the strata?"[30]

The conjecture, that the whole of the vegetable material now constituting the coal, was the growth of the antediluvian centuries, and that it was floated away and deposited by the flood, is untenable. In not a few instances trunks are found broken, and worn by water-action; but the great mass warrants the conclusion that trees of vast dimensions and of close array--dense, majestic forests, such as now occur only in the most humid regions of the tropics--were submerged in their native abodes, lying where they fell, and where they have left the impressions, side by side, on the upper and under surfaces of the shale, of their delicate peculiarities of structure, which would have been totally obliterated, if the trees had been sea-borne and shore-rolled, as pretended. The result of a careful and minute examination of the phenomena of coal, by Mr. Binney, is, that the vegetable matter now forming coal had grown in vast _marine_ swamps, subjected to a series of _subsidences_ with long intervals of repose; that the trees, and perhaps smaller plants, were submerged under _tranquil_ water, in the places of their growth; and that very inconsiderable portions, if any, of the beds, are owing to drifting.[31]

While the coal was in process of deposition, the sea was occupied with Invertebrata, not widely differing from those which had marked the previous eras.

Fishes, however, were advancing in development; and several new and strange forms, some of them of gigantic dimensions and formidable armature, were introduced. These were chiefly remarkable for their affinities with Reptiles (whence they are often called _Sauroid_ Fishes); and one of them--_Megalichthys_--was famished with jaws of serried teeth, surpassing those of the crocodile. With these were associated other and more ordinary Fishes; and swarms of Sharks of many species, and varying much in size, roved through the sea, maintaining the same pirate character as their representatives of our modern seas--fierce, subtle, voracious, and powerful.

At this time, too, appeared the earliest Reptiles, chiefly of the Amphibia sub-class. Some of these are known only by their foot-prints; and the late Hugh Miller has graphically described the appearance of some of these, which, he met with marking the roof of a coal-mine, four hundred feet below the surface. These must have been _Batrachia_ of large size, as the fore feet were thirteen inches apart across the breast.[32] They will be alluded to again.

With these exceptions, remains of terrestrial animals are, as has already been observed, rare in this formation.

III.

THE WITNESS FOR THE MACRO-CHRONOLOGY.

(CONTINUED.)

"Always distrust very plain cases: beware lest a snake
suddenly start out upon you, in the shape of some concealed
and utterly unexpected difficulty."--WARREN: _Law Studies_.

We have hitherto been considering the strata as if they had remained permanent when once deposited, subject to no change, save the successive superposition of other strata upon them. But this is very far from being true. Enormous displacements, upheavings, contortions, and fractures, are observed in the strata, which tell of mighty forces having been at work upon them after their formation. The explanation of these phenomena is due to the internal heat, which ever and anon seems to concentrate its action on some special point, seeking and finding vent for itself by some alteration in the already consolidated crust.

Sometimes, the mode of action has been the transmission of undulations through the crust, producing earthquakes, cracking and forcing apart strata already petrified, and bending and variously contorting those that have but partially become solid. Sometimes, the fiery impulse is sufficiently concentrated to break through the superincumbent materials, forcing a passage for the molten and incandescent rock, which then flows forth from the surface, penetrates into the cracks and fissures of the fractured strata, and frequently spreads into the hollows and over the summits of the latest formations.

It is owing to such causes as these, that we find the rocky layers so often inclined at various angles to the horizon, instead of being parallel to it, as they would be of course deposited; occasionally standing quite perpendicularly, and even to a small extent reversed. The outcropping of formations, the long lines of cliff running across a country in parallel series, ("crag and tail,") the dipping of strata from some central point or ridge, and the non-correspondence between the bottom of one stratum and the top of the underlying one,--are all phenomena of this sort of powerful action, which has been more or less energetic at all periods.

After the deposit of the Old Red Sandstone, the internal fire appears to have enjoyed a lull of its energy, if not a complete cessation, until the Coal Measures were complete. Then the long tranquility was again broken, and concussions so extensive and violent ensued, that hardly a single square mile of country can anywhere be found which is not full of fractured and contorted strata, the record of subterranean movements, which mostly occurred between the Carboniferous and the Premian deposits.

The effects of these convulsions were manifest in the changed relations of land and sea, existing continents and islands being dislocated, severed, and swallowed up, while others were elevated from the depths of the previous ocean.

It was from the wave-worn materials thus obtained from pre-existing strata, that the New Red Sandstone was consolidated. It consists chiefly of sand and mud, with few organic remains; and the hiatus thus found, in animals and vegetables, seems to be almost a complete one between the organisms of the preceding and the succeeding periods.

The most interesting traces of the earth's tenants during the New Red formation, consist of foot-tracks impressed by the progress of animals along the yielding mud between the ranges of high and low tide. They afford a remarkable example (not, I think, sufficiently dwelt on) of the extreme rapidity with which deposits were consolidated; since the tracks must have been made, and the material consolidated, during the few hours, _at most_, that intervened between the recess and the reflux of the tide; since, if the mud had not so soon become solid, the flow of the sea would have instantly obliterated such marks, as it does now on our shores.

The principal animal, whose foot-prints have been identified, was an enormous Frog (_Labyrinthodon_), as big as a hippopotamus, but apparently allied, in its serried teeth, and in the bony plates with which it was covered, to the Crocodiles, which were its associates.

It is curious that marks in the same material have chronicled the serpentine trail of a Sea-worm, the scratchings of a Crab, the ripple of the wavelets, and even the drops of a passing shower; the last revealing, by their margins, the direction of the wind by which the slanting rain was driven.

If the Triassic formations display but little evidence of organic existence, the lack is supplied by the abundance of such records, which is contained in the Oolitic system, and specially in its lowest component,--the Lias. Animals now existed in profusion, but of species which were for the most part peculiar. The coral-making Polypes existed not (or very rarely) in the seas of that age, but lime was secreted by an unusual number of Crinoid Echinoderms, which seem to have fringed the rocks and floating pieces of timber, much as Barnacles do now.

Among the Mollusca now began to appear the inhabitants of those very elegant shells, the _Ammonites_, allied to the Nautilus of our Southern seas, which may be considered as the lingering representative of those swarms of shelled Cephalopoda. They were accompanied by their near relations, the _Belemnites_, more resembling a Cuttle, with a long internal, pointed shell.

Fishes, chiefly belonging to a curiously armed tribe of Sharks, together with some enclosed in bony-mail like pavement, were present in the shallows, where the Lias was probably deposited.

_Plesiosaurus dolichodeirus_ and _P. macrocephalus_.]

But the most characteristic animals were great marine Reptiles, of strange and uncouth forms, to which the present world presents us no known analogy. One of these was the _Ichthyosaurus_, which closely resembled a porpoise in form, but thirty or forty feet in length, with a vertical fish-like tail, and two pairs of paddles; a mouth set with stout crocodilian teeth, and enormous eyes. Another form was that of the _Plesiosaurus_, scarcely less in size than its fellow, which in the outline of its body it resembled: it was distinguished, however, by an extraordinary length of neck, slender and swan-like, consisting of thirty or forty vertebræ.

It adds to the interest of these great marine Reptiles, that around their fossil skeletons are preserved pellets of excrement (known as Coprolites) containing fragments of bone, teeth, and scales of fishes, which clearly reveal the nature of their food. In some instances, the stomach and intestines of these great carnivorous creatures, filled with half-digested food, have left indubitable traces of their presence _in situ_.

Again, the geography of the Globe changed. New lands arose from the sea, and old lands partially or wholly sank. The German Ocean, and part of Western Europe, of our maps, were a great group of islands. The Oolitic formation was deposited. The general character of the organization of this period differed little from that of the Lias. New forms of plants, such as _Cycadeæ_, were abundant, with, considerable numbers of Corals, Encrinites, Sea-urchins and Mollusks. Macrurous Crustacea, much like those of our times (but essentially different in species), inhabited the sea, and some Beetles and Flies represented the Insects of the land. The Fishes and Marine Reptiles were pretty much the same with those of the Lias, though they received some important additions.

It is, however, among the terrestrial Vertebrata that we must look for the characteristic organisms of this age. And these are, still, Reptiles. The huge _Megalosaurus_, with a body as big as an elephant's, stood high on his legs, and stretched open a pair of gaping jaws, set with jagged teeth. The _Pterodactyles_ flew about,--carnivorous lizards, with the body and wings of bats,[33] except that the membrane was stretched upon the enormously developed little finger;--creatures, perhaps, the most unlike to anything familiar to us, of all fossil forms. And, in the marshy margins of the great river valley which formed the Wealden of our South-eastern districts, the giant _Iguanodon_, and his fellow, the _Hylæosaurus_, waged their peaceful warfare on the succulent plants that became their unresisting prey.

_Pterodactylus crassirostris_, and _P. brevirostris_.]

The circle of animal life was completed in this epoch, thus far, that every class was represented by some one or more of its constituent species. No fossil skeletons of Birds have, indeed, been found so low as the Oolite, but numerous foot-prints of some of the Grallatores are found in a sandstone of this period; and in the Stonesfield slate, which is contemporary with it, a genus of Mammalia has been discovered,--a small Marsupial, allied to the Opossums of America.

The duration of the Oolitic period must have been considerable. "The lias sea-bottom was succeeded first by a sandy, and then by a calcareous deposit, and the animals were modified accordingly." The deposit of carbonate of lime, which took place under circumstances that caused it to attract around its nodules the organic particles, whence the name _oolite_ (egg-stone) is derived, was not continuous, but repeated at intervals. The shells of Mollusks were developed in great abundance, and accumulations of these formed thick bands, which consolidated into layers of shell-limestone. Three hundred feet of strata, largely composed of organic remains, were formed before the clay was deposited which made the Stonesfield and contemporaneous slates.

Once more the dry land sank, probably by slow successive subsidences, and the sea flowed many fathoms deep above the great European archipelago. And upon its quiet bottom settled down, first a few sandy and clayey beds, and then the great layer of the Chalk.

Creatures of very minute size and low grades of organization were now playing a very important part. A large portion of the lime that was deposited, in the form of a pure carbonate, was doubtless supplied by the Coral structures, which, were exceedingly numerous; the polypidoms being gnawed down by strong-jawed fishes that fed upon the Zoophytes. _Foraminifera_ also were abundant, and contributed to the supply.

Nodules of flint exist in the Chalk, sometimes scattered, sometimes arranged in bands. Two sources are indicated for this substance. One is Sponge, the most common kinds of which are composed of skeletons of siliceous spicula; and these can be discerned with the microscope in the interior of the chalk-flints. But millions upon millions of Infusoria swam through the waters, and many of these were encased in siliceous loricæ, while the rocks and sea-weeds were fringed with as incalculably numerous examples of siliceous _Diatomaceæ_, whose elegant forms are recognisable without difficulty throughout the Chalk. The inconceivable abundance of these forms may be illustrated by the often-cited fact, that whole strata of solid rock appear to be so exclusively composed of their solid remains, that a cube of one-tenth of an inch is computed by Ehrenberg to contain five hundred millions of individuals.

The increase of these organisms is very rapid, and their duration proportionately short; but allowing for this, what period would elapse before the successive generations of entities, of which forty-one thousand millions are required to make a cubic inch, would have accumulated into solid strata fourteen feet in thickness?

Without pausing to examine the whole Cretaceous fauna, we may observe that the Mollusca with chambered shells--the Ammonites and their allies--were developed in singular variety and profusion during this period, after which they suddenly disappeared from the ocean. The Fishes present little that is remarkable; of Birds, few, and of Mammals, no remains exist; and the Reptiles, while not absolutely extinct, are few and rare. One great marine form, however, the _Mosasaurus_, was added to their number.

At length the sea ceased to deposit chalk, and its bed appears to have been slowly elevated, until all the animals that had inhabited the waters of that formation were destroyed; so that their race and generation perished.[34] The grand epoch of Secondary Formations was closed.

It was followed by an extensive disruption of the then existing strata, and by changes and modifications so great as to alter the whole face of nature. "It would appear that a long period of time elapsed before newer beds were thrown down, since the chalky mud not only had time to harden into chalk, but the surface of the chalk itself was much rubbed and worn." During this protracted period, eruptions of molten rock occurred of enormous extent, producing the Basaltic formation which covers the Chalk in the north of Ireland, and in some of the Hebrides. In the south of Europe the Pyrenees were elevated, and the Apennines and Carpathians were pushed to a greater altitude than before, if they were not then formed. The Alps and the Caucasus also experienced a series of upward movements, continuing through a considerable range of the Tertiary epoch.

The rich collections of vegetable remains--chiefly fruits and seeds--that have been made from the London Clay, show that the earliest land of this period was clothed with a great abundance and variety of plants; and these are of such alliances as would now require a tropical climate. Many species of Palms, Screw-pines, Gourds, _Piperaceæ_, _Mimoseæ_, and other _Leguminosæ_, _Malvaceæ_, and _Coniferæ_, dropped their woody pods and fruits where now these pages are written; and the animals manifest no less interesting an approximation to existing forms than the plants. The Zoophytes, the Echinoderms, the Foraminifera, the Worms, the Crustacea, the Mollusca, the Fishes and the Reptiles of the Eocene beds, exhibit a great preponderance of agreement with those that now exist, _so far as genus is concerned_, though the _species_ are still almost wholly distinct. The approximation is particularly marked in the Molluscous sub-kingdom, by the almost entire disappearance of the hitherto swarming Brachiopod and Cephalopod forms, and the progressive substitution for them of the _Conchifera_ and _Gastropoda_, which had, however, throughout the Secondary epoch, been gradually coming forward to their present predominance in nature.

Among the Fishes, the Placoid type was diminished in number; and those that were produced were mostly Sharks and Rays, of modern genera; but the chief difference was the paucity of those mailed forms (Ganoids), which were so abundant during the Oolitic period. On the other hand, the Ctenoid and Cycloid forms, which had begun to make their appearance in small numbers in the Chalk, are well represented. In both this deficiency and this plenitude, there is a very decided approach to existing conditions; for the Ganoids are almost unknown with us, while the last-named two orders are abundant. Representatives of our Perches, Maigres, Mackerels, Blennies, Herrings, and Cods, were numerous; _distinct, however, from the present species_. But not a single member of the great Salmon family was yet introduced.

The great Saurian Reptiles had entirely disappeared, and were quite unrepresented in the tertiary beds, except by a Crocodile or two, and a small Lizard. Turtles were, however, numerous, both of the marine and lacustrine kinds; and there is an interesting stranger, in the form of a large Serpent, allied to our Pythons, some twenty feet in length.

Birds and Mammals began now to assume their place on the land. The London Clay presents us with a little Vulture; and the Paris basin contains remnants of species representing the Raptores, the Rasores, the Grallatores, and the Natatores.

The Quadrupeds came in in some force; not developed from the lowest to the highest scale of organization; for the Monkey and the Bat occur in sands, certainly not later, if not earlier, than the London Clay, contemporaneously with the Racoon, and before the existence of any Rodent or Cetacean. Some Carnivora, as the Wolf and the Fox, roamed the woods, but the character of the epoch was given by the Pachyderms.

These, however, were not the massive colossi that browse in the African or Indian jungles of our days; no Elephant, no Rhinoceros, no Hippopotamus was as yet formed. But several kinds of Tapir wallowed in the morasses; and a goodly number of largish beasts, whose affinities were with the Pachydermata, while their analogies were with the Ruminantia, served as substitutes for the latter order, which was wholly wanting. These interesting quadrupeds, forming the genus _Anoplotherium_, were remarkable for two peculiarities,--their feet were two-toed, and their teeth were ranged in a continuous series, without any interval between the incisors and the molars. They varied in size from that of an ass to that of a hare.

The physical conditions of our earth, when it was tenanted by these creatures, is thus described:--"All the great plains of Europe, and the districts through which the principal rivers now run, were then submerged; in all probability, the land chiefly extended in a westerly direction, far out into the Atlantic, possibly trending to the south, and connecting the western shores of England with the volcanic islands off the west coast of Africa. The great mountain chains of Europe, the Pyrenees, the Alps, the Apennines, the mountains of Greece, the mountains of Bohemia, and the Carpathians, existed then only as chains of islands in an open sea. Elevatory movements, having an east and west direction, had, however, already commenced, and were producing important results, laying bare the Wealden district in the south-east of England. The southern and central European district, and parts of western Asia, were the recipients of calcareous deposits (chiefly the skeletons of _Foraminifera_), forming the Apennine limestone; while numerous islands were gradually lifted above the sea, and fragments of disturbed and fractured rock were washed upon the neighbouring shallows or coast-lines, forming beds of gravel covering the Chalk. The beds of Nummulites and Miliolites, contemporaneous with those containing the Sheppey plants and the Paris quadrupeds, seem to indicate a deep sea at no great distance from shore, and render it probable that there were frequent alternations of elevation and depression, perhaps the result of disturbances acting in the direction already alluded to.

"The shores of the islands and main land were, however, occasionally low and swampy, rivers bringing down mud in what is now the south-east of England, and the neighbourhood of Brussels, but depositing extensive calcareous beds near Paris. Deep inlets of the sea, estuaries, and the shifting mouths of a river, were also affected by numerous alterations of level not sufficient to destroy, but powerful enough to modify, the animal and vegetable species then existing; and these movements were continued for a long time."[35]

After the elevation of the mountain summits of Europe above the sea, and while the same causes were still in operation, deposits were being made in the narrow intervening seas of the Archipelago, such as the present south of France, the valleys of the Rhine and Danube, the eastern districts of England and Portugal. These deposits were partly marine and partly lacustrine; the former consisting largely of loose sands, mingled with shells and gravel. In Switzerland is a thick mass of conglomerate; and in the district around Mayence, there is a series of fresh-water limestones, and sandstones charged with organic remains.

The changes which took place during this comparatively recent epoch were not sudden, but gradual; the results of operations which were probably going on without intermission, and perhaps have not yet ceased. The land was more and more upheaved, till at length, what had been an archipelago of islands became a continent, and Europe assumed the form which it bears on our maps.

The most interesting addition to the natural history of the Miocene, or Middle Tertiary period, was the _Dinotherium_--a huge Pachyderm, twice as large as an elephant, with a tapir-like proboscis, and two great tusks curving downward from the lower jaw. It was, doubtless, aquatic in its habits, and possibly (for its hinder parts are not known), it may have been allied to the Dugong and Manatee, those whale-like Pachyderms, with a broad horizontal tail, instead of posterior limbs.

Other great herbivorous beasts roamed over the new-made land. The Mastodons, closely allied to the Elephant, had their head-quarters in North America, but extended also to Europe. And the Elephants themselves, of several species, were spread over the northern hemisphere, even to the polar regions. The Hippopotamus, the Rhinoceros, and other creatures, now exclusively tropical, were also inhabitants of the same northern latitudes.

From some specimens of Elephants and Rhinoceroses of this period, which seem to have been buried in avalanches, and thus to have been preserved from decomposition, even of the more transitory parts, as muscle and skin, we learn something of the climate that prevailed. The very fact of their preservation, by the antiseptic power of frost, shows that it was not a tropical climate in which they lived; and the clothing of thick wool, fur, and hair, which protected the skin of the Mammoth, or Siberian Elephant, tends to the same conclusion. At the same time, those regions were not so intensely cold as they are now. For the district in which the remains of Elephants and their associates are found, in almost incredible abundance, is that inhospitable coast of northern Asia which bounds the Polar Sea.

The trees of a temperate climate--the oak, the beech, the maple, the poplar, and the birch--which now attain their highest limit somewhere about 70° of north latitude, and there are dwarfed to minute shrubs, appear then to have grown at the very verge of the polar basin; and that in the condition of vast and luxuriant forests, perhaps occupying sheltered valleys between mountains whose steep sides were covered with snow, already become perennial, and ever and anon rolling down in overwhelming avalanches, such as those which now occasionally descend into the valleys of the Swiss Alps.

The coast of Suffolk displays a formation known as the Crag--a local name for gravel--which rests partly on the chalk; but, as it lies in other parts over the London Clay, it is assigned to the later Tertiary, or what is called the Pleiocene period. It is divided into the _coralline_ and the _red_ crag, the latter being uppermost where they exist together, and therefore being the more recent. The Coralline Crag is nearly composed of corals and shells, the former almost wholly extinct now; but the latter containing upwards of seventy species still existing in the adjacent seas. The Red Crag contains few zoophytes, but is remarkable for the remains of at least five species of Whales. Other Mammalia occur in this formation, among which are the red deer and the wild boar of modern Europe.

The gradual but rapid approximation of the Tertiary fauna to that of the present surface is well indicated by Mr. Lyell's table (1841) of recent and fossil species in the English formations:--

Per-centage No. of
Periods. Localities. of fossils
recent. compared.

Eocene {London and Hampshire } 1 or 2 400 Miocene {Red and Coralline } 20 to 30 450 { Crag, Suffolk } Older Pleiocene {Mamaliferous or Norwich } 60 to 70 111 { Crag } Newer Pleiocene {Marine strata near } 85 to 90 160 { Glasgow } Post Pleiocene {Fresh-water of the valley} 99 to 100 40 { of the Thames }

It is to this period that are assigned the animals whose bones are found in astonishing numbers in limestone caverns, as, for example, that notable one at Kirkdale, in Yorkshire, which was examined by Professor Buckland.

This is a cave in the Oolitic limestone, with a nearly level floor, which was covered with a deposit of mud, on which an irregular layer of sparry stalagmite had formed by the dripping of water from the low roof, carrying lime in solution. Beneath this crust the remains were found.

Of the animals to which the bones belonged, six were _Carnivora_, viz. _hyæna_, _felis_, bear, wolf, fox, weasel; four _Pachydermata_, viz. elephant, rhinoceros, hippopotamus, horse; four _Ruminantia_, viz. ox, and three species of deer; four _Rodentia_, viz. hare, rabbit, water-rat, mouse; five Birds, viz. raven, pigeon, lark, duck, snipe.

The bones were almost universally broken; the fragments exhibited no marks of rolling in the water, but a few were corroded; some were worn and polished on the convex surface; many indented, as by the canine teeth of carnivorous animals. In the cave the peculiar excrement of hyænas (_album græcum_) was common; the remains of these predacious beasts were the most abundant of all the bones; their teeth were found in every condition, from the milk-tooth to the old worn stump; and from the whole evidence Dr. Buckland adopted the conclusion, in which almost every subsequent writer has acquiesced, that Kirkdale Cave was a den of hyænas during the period when elephants and hippopotami (not of existing species) lived in the northern regions of the globe, and that they dragged into it for food the bodies of animals which frequented the vicinity.[36]

Thus in these spots we find, observes Professor Ansted, "written in no obscure language, a portion of the early history of our island after it had acquired its present form, while it was clothed with vegetation, and when its plains and forests were peopled by many of the species which still exist there; but when there also dwelt upon it large carnivorous animals, prowling about the forests by night, and retiring by day to these natural dens."

In our own country, and in many other parts of the world, we find fragments of stone distributed over the surface, sometimes in the form of enormous blocks, bearing in their fresh angles evidence that they have been little disturbed since their disruption, but sometimes much rubbed and worn, and broken into smaller pieces, till they form what is known as gravel. In many cases the original rock from which these masses have been separated does not exist in the vicinity of their locality; and it is not till we reach a distance, often of hundreds of miles, that we find the formation of which they are a component part.

Various causes have been suggested for the transport of these erratic blocks, of which the most satisfactory is the agency of ice, either as slow-moving glaciers, or as oceanic icebergs.

"The common form of a glacier," says Professor J. Forbes, "is a river of ice filling a valley, and pouring down its mass into other valleys yet lower. It is not a frozen ocean, but a frozen torrent. Its origin or fountain is in the ramifications of the higher valleys and gorges, which descend amongst the mountains perpetually snow-clad. But what gives to a glacier its most peculiar and characteristic feature is, that it does not belong exclusively or necessarily to the snowy region already mentioned. The snow disappears from its surface in summer as regularly as from that of the rocks which sustain its mass. It is the prolongation or outlet of the winter-world above; its gelid mass is protruded into the midst of warm and pine-clad slopes and green-sward, and sometimes reaches even to the borders of cultivation."[37]

The glacier moves onward with a slow but steady march towards the mouth of its valley. Its lowest stratum carries with it numerous fragments of rock, which, pressed by the weight of the mighty mass, scratch and indent the surfaces over which they move, and sometimes polish them. These marks are seen on many rock-surfaces now exposed, and they are difficult to explain on any other hypothesis than that of glacial action.

But the alternate influence of summer and winter--the percolation of rain into the mountain fissures, and the expansion of freezing--dislodge great angular fragments of rock, which fall on the glacier beneath. Slowly but surely these then ride away towards the mouth of the valley, till they reach a point where the warmth of the climate does not permit the ice to proceed; the blocks then are deposited as the mass melts. But if the climate itself were elevated, or if the surface were lowered so as to immerse the glacier in the sea, it would melt throughout its course, and then the blocks would be found arranged in long lines or _moraines_, such as we see now in many places.

If the glacier-valley debouch on the sea, the ice gradually projects more and more, until the motions of the waves break off a great mass, which floats away, carrying on its surface the accumulation of boulders, gravel, and other _débris_ which it had acquired during its formation. It is now an iceberg, which, carried by the southern currents, approaches a warmer climate, melts, and deposits its cargo, perhaps hundreds of leagues from the valley where it was shipped, and as fresh as when its component _frusta_ were detached from the primitive rock.

If the abundance of such erratic blocks and foreign gravel seem to require a greater amount of glacial action than is now extant, it has been suggested that the volcanic energy which elevated Europe may have been succeeded by a measure of subsidence before the land attained its present permanent condition. Hence there may have been, during the Tertiary epoch, mountain chains of great elevation, sufficient to supply the glaciers, which, on their subsidence, melted on the spot where they were submerged, or floated away as icebergs on the pelagic currents, till they grounded on the bays and inlets of other shores, which were subsequently elevated again.

Thus a large portion of the animals which then inhabited these islands (up to that time, perhaps, united to the continent) would be drowned, and many species quite obliterated, a few alone remaining to connect our present fauna with that of the submerged area, when the land rose again to its existent state.

It would not materially augment the force of the evidence already adduced on the question of chronology, to examine in detail the fossil remains of South America, Australia, and New Zealand. The gigantic Sloths[38] of the first, the gigantic Marsupials of the second, and the gigantic Birds of the third, however interesting individually, and especially as showing that a prevailing type governed the fauna in each locality then as now--are all formations of the Tertiary period, and some of them, at least, seem to have run on even into the present epoch. Indeed, it is not quite certain that the enormous birds of New Zealand and Madagascar are even yet extinct.

The phenomenon of raised sea-beaches is one of great interest, and seems to be connected with the alternate elevations and depressions of the Tertiary epoch, perhaps marking the successive steps of the upheaval of the land. In several parts of England the coast-line exhibits one or more shelves parallel with the existing sea-beach, and covered with similar shingle, sand, and sea-shells. And the same phenomenon is exhibited on a still more gigantic scale in South America. Mr. Darwin[39] found that for a distance of at least 1,200 miles from the Rio de la Plata to the Straits of Magellan on the eastern side, and for a still longer distance on the west, the coast-line and the interior have been raised to a height of not less than 100 feet in the northern part, but as much as 400 feet in Patagonia. All this change has taken place within a comparatively short period; for in Valparaiso, where the effect is most considerable, modern marine deposits, with human remains, are seen at the height of 1,300 feet above the sea.

At what exact point, geologically, the period of human history begins, it is impossible to say. No evidence of Man's presence has occurred older than the latest Tertiary deposits, which insensibly merge into the Alluvial. It seems certain that human remains have been found in chronological association with those of animals long extinct, and there appears no reason to doubt that some species of animals, as the Irish Deer, the Moa of New Zealand, and the Dodo of the Mauritius, have disappeared from creation within a period of a few centuries.[40] It is not improbable that the last of the Moho race may have lived only long enough to grace the pages of the "Birds of Australia."

It is as important as it is interesting, to observe that the same kinds of physical operations have been, within the present epoch, and are still, going on, as those whose results are chronicled in the rocks. Strata of alluvium are constantly being formed on a scale which, though it does not _suddenly_ affect the outline of coasts, and therefore appears small, yet is great in reality.

The Ganges is estimated to pour into the Indian Ocean nearly 6,400 millions of tons of mud every year; and its delta is a triangle whose sides are two hundred miles long. The delta of the Mississippi is of about the same size, and it advances steadily into the Gulf of Mexico at the rate of a mile in a century.

The accumulation of river-mud is gradually filling up the Adriatic Sea. From the northernmost point of the Gulf of Trieste to the south of Ravenna, there is an uninterrupted series of recent accessions of land, more than a hundred miles in length, which, within the last twenty centuries, have increased from two to twenty miles in breadth.

The coral-polypes are working still with great energy. Mr. Darwin mentions two or three examples of the rate of increase, one of which only I shall cite. In the lagoon of Keeling Atoll, a channel was dug for the passage of a schooner built upon the island, through the reef into the sea; in ten years afterward, when it was examined, it was found almost choked up with living coral.

Volcanic action is busy in many parts of the earth, pouring forth clouds of ashes and torrents of molten rock; and instances are not wanting in which new islands have been raised from the bed of the ocean by this means, within the sphere of history.

Slow and permanent changes of level are still being produced on the earth's crust. The bottom of the Baltic has been, for several centuries at least, in process of continuous elevation, the effects of which are palpable. Many rocks formerly covered are now permanently exposed; channels between islets, formerly used, are now closed up, and beds of marine shells have become bare. On the other hand, the whole area of the Pacific Polynesia seems subsiding.

Deposits are being made by waters which hold earthy substances in solution. The principal of these is _lime_. Several remarkable examples of this kind are quoted by Sir Charles Lyell, in one of which there is a thickness of 200 or 300 feet of travertine of recent deposit, while in another a solid mass thirty feet thick was deposited in about twenty years. He also states that there are other countless places in Italy where the constant formation of limestone may be seen, while the same may be said of Auvergne and other volcanic districts. In the Azores, Iceland, and elsewhere, _silica_ is deposited often to a considerable extent. Deposits of _asphalt_ and other bituminous products occur in other places.[41]

The floors of limestone caverns are frequently strewn with fossil bones, which are imbedded in stalagmite, and this incrustation is still in progress of formation. It is remarkable that in this deposit alone we obtain the bones of Man in a fossil condition. The two creations,--the extinct and the extant,--or rather the prochronic and the diachronic--here unite. But there is no line of demarcation between them; they merge insensibly into each other. The bones of Man, and even his implements and fragments of pottery, are found mingled with the skeletons of extinct animals in the caves of Devonshire, in those of Brazil,[42] and in those of Franconia. In Peru, some scores of human skeletons have been found in a bed of travertine, associated with marine shells; the stratum itself being covered by a deep layer of vegetable soil, forming the face of a hill crowned with large trees.

From a very interesting paper by M. Marcel de Serres, it appears indubitable that the existing shells of the Mediterranean are even now passing in numbers into the fossil state, and that not in quiet spots only, but where the sea is subject to violent agitations. Specimens of common species, "completely petrified, have been converted into carbonate of lime at the same time that they have lost the animal matter which they originally contained. Their hardness and solidity are greater than those of some petrified species from tertiary formations."

"In the collection of M. Doumet, Mayor of Cette, there exists an anchor which exhibits the same circumstances, and which is also covered with a layer of solid calcareous matter. This contains specimens of _Pecten_, _Cardium_, and _Ostrea_, completely petrified, and the hardness of which is equal to that of fossil species from secondary formations. On the surface of the deposit in which the anchor is imbedded, there are _Anomiæ_ and _Serpulæ_, which were living when the anchor was got out of the sea; these present no trace of alteration."[43]

Thus we have brought down the record to an era embraced by human history, and even to individual experience; and we confidently ask, Is it possible, is it imaginable, that the whole of the phenomena which occur below the diluvial deposits can have been produced within six days, or seventeen centuries? Let us recapitulate the principal facts.

1. The crust of the earth is composed of many layers, placed one on another in regular order. All of these are solid, and most are of great density and hardness. Most of them are of vast thickness, the aggregate not being less than from seven to ten miles.

2. The earlier of these were made and consolidated before the newer were formed; for in several cases, it is demonstrable that the latter were made out of the _débris_ of the former. Thus the compact and hard granite was disintegrated grain by grain; the component granules were rolled awhile in the sea till their angles were rubbed down; they were slowly deposited, and then consolidated in layers.

3. A similar process goes on again and again to form other strata, all occupying long time, and all presupposing the earlier ones.[44]

4. After some strata have been formed and solidified, convulsions force them upward, contort them, break them, split them asunder. Melted matter is driven through the outlets, fills the veins, spreads over the surface, settles into the hollows, cools and solidifies.

5. After the outflowing and consolidation of these volcanic streams, the action of running water cuts them down, cleaving beds of immense depth through their substance. Mr. Poulett Scrope, speaking of the solidified streams of basalt, in the volcanic district of Southern France, observes:--

"These ancient currents have since been corroded by rivers,
which have worn through a mass of 150 feet in height, and
formed a channel even in the granite rocks beneath, since
the lava first flowed into the valley. In another spot, a
bed of basalt, 160 feet high, has been cut through by a
mountain stream. The vast excavations effected by the
erosive power of currents along the valleys which feed the
Ardèche, since their invasion by lava-currents, prove that
even the most recent of these volcanic eruptions belong to
an era incalculably remote."[45]

6. A series of organic beings appears, lives, generates, dies; lives, generates, dies; for thousands and thousands of successive generations. Tiny polypes gradually build up gigantic masses of coral,--mountains and reefs--microscopic foraminifera accumulate strata of calcareous sand; still more minute infusoria--forty millions to the inch--make slates, many yards thick, of their shells alone.