This texture of stone is novel and striking. It is supposed to be of chemical origin, each spherule being an aggregation of particles round a central nucleus. The oolite system is largely developed in England, France, Westphalia, and Northern Italy; it appears in Northern India and Africa, and patches of it exist in Scotland, and in the vale of the Mississippi. It may of course be yet discovered in many other parts of the world.
The series, as shewn in the neighbourhood of Bath, is (beginning with the lowest) as follows:- 1. Lias, a set of strata variously composed of limestone, clay, marl, and shale, clay being predominant; 2.
Lower oolitic formation, including, besides the great oolite bed of central England, fullers" earth beds, forest marble, and cornbrash; 3. Middle oolitic formation, composed of two sub-groups, the Oxford clay and coral rag, the latter being a mere layer of the works of the coral polype; 4. Upper oolitic formation, including what are called Kimmeridge clay and Portland oolite. In Yorkshire there is an additional group above the lias, and in Sutherlandshire there is another group above that again. In the wealds (moorlands) of Kent and Suss.e.x, there is, in like manner, above the fourth of the Bath series, another additional group, to which the name of the Wealden has been given, from its situation, and which, composed of sandstones and clays, is subdivided into Purbeck beds, Hastings sand, and Weald clay.
There are no particular appearances of disturbance between the close of the new red sandstone and the beginning of the oolite system, as far as has been observed in England. Yet there is a great change in the materials of the rocks of the two formations, shewing that while the bottoms of the seas of the one period had been chiefly arenaceous, those of the other were chiefly clayey and limy. And there is an equal difference between the two periods in respect of both botany and zoology. While the new red sandstone shews comparatively scanty traces of organic creation, those in the oolite are extremely abundant, particularly in the department of animals, and more particularly still of sea mollusca, which, it has been observed, are always the more conspicuous in proportion to the predominance of calcareous rocks. It is also remarkable that the animals of the oolitic system are entirely different in species from those of the preceding age, and that these species cease before the next. In this system we likewise find that uniformity over great s.p.a.ce which has been remarked of the Faunas of earlier formations.
"In the equivalent deposits in the Himalaya Mountains, at Fernando Po, in the region north of the Cape of Good Hope, and in the Run of Cutch, and other parts of Hindostan, fossils have been discovered, which, as far as English naturalists who have seen them can determine, are undistinguishable from certain oolite and lias fossils of Europe." {108a}
The dry land of this age presented cycadeae, "a beautiful cla.s.s of plants between the palms and conifers, having a tall, straight trunk, terminating in a magnificent crown of foliage." {108b} There were tree ferns, but in smaller proportion than in former ages; also equisetaceae, lilia, and conifers. The vegetation was generally a.n.a.logous to that of the Cape of Good Hope and Australia, which seems to argue a climate (we must remember, a universal climate) between the tropical and temperate. It was, however, sufficiently luxuriant in some instances to produce thin seams of coal, for such are found in the oolite formation of both Yorkshire and Sutherland. The sea, as for ages before, contained algae, of which, however, only a few species have been preserved to our day. The lower cla.s.ses of the inhabitants of the ocean were unprecedentedly abundant. The polypiaria were in such abundance as to form whole strata of themselves. The crinoidea and echinites were also extremely numerous. Sh.e.l.l mollusks, in hundreds of new species, occupied the bottoms of the seas of those ages, while of the swimming sh.e.l.l-fish, ammonites and belemnites, there were also many scores of varieties.
The belemnite here calls for some particular notice. It commences in the oolite, and terminates in the next formation. It is an elongated, conical sh.e.l.l, terminating in a point, and having, at the larger end, a cavity for the residence of the animal, with a series of air-chambers below. The animal, placed in the upper cavity, could raise or depress itself in the water at pleasure by a pneumatic operation upon the entral air tube pervading its sh.e.l.l. Its tentacula, sent abroad over the summit of the sh.e.l.l, searched the sea for prey. The creature had an ink-bag, with which it could muddle the water around it, to protect itself from more powerful animals, and, strange to say, this has been found so well preserved that an artist has used it in one instance as a paint, wherewith to delineate the belemnite itself.
The crustacea discovered in this formation are less numerous. There are many fishes, some of which (acrodus, psammodus, &c.,) are presumed from remains of their palatal bones, to have been of the gigantic cartilaginous cla.s.s, now represented by such as the cestraceon. It has been considered by Professor Owen as worthy of notice, that, the cestraceon being an inhabitant of the Australian seas, we have, in both the botany and ichthyology of this period, an a.n.a.logy to that continent. The pycnodontes, (thick-toothed,) and lepidoides, (having thick scales,) are other families described by M.
Aga.s.siz as extensively prevalent. In the shallow waters of the oolitic formation, the ichthyosaurus, plesiosaurus, and other huge saurian carnivora of the preceding age, plied, in increased numbers, their destructive vocation. {110} To them were added new genera, the cetiosaurus, mososaurus, and some others, all of similar character and habits.
Land reptiles abounded, including species of the pterodactyle of the preceding age--tortoises, trionyces, crocodilians--and the pliosaurus, a creature which appears to have formed a link between the plesiosaurus and the crocodile. We know of at least six species of the flying saurian, the pterodactyle, in this formation.
Now, for the first time, we find remains of insects, an order of animals not well calculated for fossil preservation, and which are therefore amongst the rarest of the animal tribes found in rocks, though they are the most numerous of all living families. A single libellula (dragon-fly) was found in the Stonesfield slate, a member of the lower oolitic group quarried near Oxford; and this was for several years the only specimen known to exist so early; but now many species have been found in a corresponding rock at Solenhofen, in Germany. It is remarkable that the remains of insects are found most plentifully near the remains of pterodactyles, to which undoubtedly they served as prey.
The first glimpse of the highest cla.s.s of the vertebrate sub-kingdom- -mammalia--is obtained from the Stonesfield slate, where there has been found the jaw-bone of a quadruped evidently insectivorous, and inferred, from peculiarities in the structure of that small fragment, to have belonged to the marsupial family, (pouched animals). It may be observed, although no specimens of so high a cla.s.s of animals as mammalia are found earlier, such may nevertheless have existed: the defect may be in our not having found them; but, other things considered, the probability is that heretofore there were no mammifers. It is an interesting circ.u.mstance that the first mammifers found should have belonged to the marsupialia, when the place of that order in the scale of creation is considered. In the imperfect structure of their brain, deficient in the organs connecting the two hemispheres--and in the mode of gestation, which is only in small part uterine--this family is clearly a link between the oviparous vertebrata (birds, reptiles, and fishes) and the higher mammifers. This is further established by their possessing a faint development of two ca.n.a.ls pa.s.sing from near the a.n.u.s to the external surface of the viscera, which are fully possessed in reptiles and fishes, for the purpose of supplying aerated water to the blood circulating in particular vessels, but which are unneeded by mammifers. Such rudiments of organs in certain species which do not require them in any degree, are common in both the animal and vegetable kingdoms, but are always most conspicuous in families approaching in character to those cla.s.ses to which the full organs are proper. This subject will be more particularly adverted to in the sequel.
The highest part of the oolitic formation presents some phenomena of an unusual and interesting character, which demand special notice.
Immediately above the upper oolitic group in Buckinghamshire, in the vicinity of Weymouth, and other situations, there is a thin stratum, usually called by workmen the DIRT-BED, which appears, from incontestable evidence, to have been a soil, formed, like soils of the present day, in the course of time, upon a surface which had previously been the bottom of the sea. The dirt-bed contains exuviae of tropical trees, acc.u.mulated through time, as the forest shed its honours on the spot where it grew, and became itself decayed. Near Weymouth there is a piece of this stratum, in which stumps of trees remain rooted, mostly erect or slightly inclined, and from one to three feet high; while trunks of the same forest, also silicified, lie imbedded on the surface of the soil in which they grew.
Above this bed lie those which have been called the Wealden, from their full development in the Weald of Suss.e.x; and these as incontestably argue that the dry land forming the dirt-bed had next afterwards become the area of brackish estuaries, or lakes partially connected with the sea; for the Wealden strata contain exuviae of fresh-water tribes, besides those of the great saurians and chelonia.
The area of this estuary comprehends the whole south-east province of England. A geologist thus confidently narrates the subsequent events: "Much calcareous matter was first deposited [in this estuary], and in it were entombed myriads of sh.e.l.ls, apparently a.n.a.logous to those of the vivipara. Then came a thick envelope of sand, sometimes interstratified with mud; and, finally, muddy matter prevailed. The solid surface beneath the waters would appear to have suffered a long continued and gradual depression, which was as gradually filled, or nearly so, with transported matter; in the end, however, after a depression of several hundred feet, the sea again entered upon the area, not suddenly or violently--for the Wealden rocks pa.s.s gradually into the superinc.u.mbent cretaceous series--but so quietly, that the mud containing the remains of terrestrial and fresh-water creatures was tranquilly covered up by sands replete with marine exuviae." {114} A subsequent depression of the same area, to the depth of at least three hundred fathoms, is believed to have taken place, to admit of the deposition of the cretaceous beds lying above.
From the scattered way in which remains of the larger terrestrial animals occur in the Wealden, and the intermixture of pebbles of the special appearance of those worn in rivers, it is also inferred that the estuary which once covered the south-east part of England was the mouth of a river of that far-descending cla.s.s of which the Mississippi and Amazon are examples. What part of the earth"s surface presented the dry land through which that and other similar rivers flowed, no one can tell for certain. It has been surmised, that the particular one here spoken of may have flowed from a point not nearer than the site of the present Newfoundland. Professor Philips has suggested, from the a.n.a.logy of the mineral composition, that anciently elevated coal strata may have composed the dry land from which the sandy matters of these strata were washed. Such a deposit as the Wealden almost necessarily implies a local, not a general condition; yet it has been thought that similar strata and remains exist in the Pays de Bray, near Beauvais. This leads to the supposition that there may have been, in that age, a series of river- receiving estuaries along the border of some such great ocean as the Atlantic, of which that of modern Suss.e.x is only an example.
ERA OF THE CRETACEOUS FORMATION.
The record of this period consists of a series of strata, in which chalk beds make a conspicuous appearance, and which is therefore called the cretaceous system or formation. In England, a long stripe, extending from Yorkshire to Kent, presents the cretaceous beds upon the surface, generally lying conformably upon the oolite, and in many instances rising into bold escarpments towards the west.
The celebrated cliffs of Dover are of this formation. It extends into northern France, and thence north-westward into Germany, whence it is traced into Scandinavia and Russia. The same system exists in North America, and probably in other parts of the earth not yet geologically investigated. Being a marine deposit, it establishes that seas existed at the time of its formation on the tracts occupied by it, while some of its organic remains prove that, in the neighbourhood of those seas, there were tracts of dry land.
The cretaceous formation in England presents beds chiefly sandy in the lowest part, chiefly clayey in the middle, and chiefly of chalk in the upper part, the chalk beds being never absent, which some of the lower are in several places. In the vale of the Mississippi, again, the true chalk is wholly, or all but wholly absent. In the south of England, the lower beds are, (reckoning from the lowest upwards), 1. Shankland or greensand, "a triple alternation of sands and sandstones with clay;" 2. Galt, "a stiff blue or black clay, abounding in sh.e.l.ls, which frequently possess a pearly l.u.s.tre;" 3.
Hard chalk; 4. Chalk with flints; these two last being generally white, but in some districts red, and in others yellow. The whole are, in England, about 1200 feet thick, shewing the considerable depths of the ocean in which the deposits were made.
Chalk is a carbonate of lime, and the manner of its production in such vast quant.i.ties was long a subject of speculation among geologists. Some light seemed to be thrown upon the subject a few years ago, when it was observed, that the detritus of coral reefs in the present tropical seas gave a powder, undistinguishable, when dried, from ordinary chalk. It then appeared likely that the chalk beds were the detritus of the corals which were in the oceans of that era. Mr. Darwin, who made some curious inquiries on this point, further suggested, that the matter might have intermediately pa.s.sed through the bodies of worms and fish, such as feed on the corals of the present day, and in whose stomachs he has found impure chalk.
This, however, cannot be a full explanation of the production of chalk, if we admit some more recent discoveries of Professor Ehrenberg. That master of microscopic investigation announces, that chalk is composed partly of "inorganic particles of irregular elliptical structure and granular slaty disposition," and partly of sh.e.l.ls of inconceivable minuteness, "varying from the one-twelfth to the two hundred and eighty-eighth part of a line"--a cubic inch of the substance containing above ten millions of them! The chalk of the north of Europe contains, he says, a larger proportion of the inorganic matter; that of the south, a larger proportion of the organic matter, being in some instances almost entirely composed of it. He has been able to cla.s.sify many of these creatures, some of them being allied to the nautili, nummuli, cyprides, &c. The sh.e.l.ls of some are calcareous, of others siliceous. M. Ehrenberg has likewise detected microscopic sea-plants in the chalk.
The distinctive feature of the uppermost chalk beds in England, is the presence of flint nodules. These are generally disposed in layers parallel to each other. It was readily presumed by geologists that these ma.s.ses were formed by a chemical aggregation of particles of silica, originally held in solution in the ma.s.s of the chalk. But whence the silica in a substance so different from it? Ehrenberg suggests that it is composed of the siliceous coverings of a portion of the microscopic creatures, whose sh.e.l.ls he has in other instances detected in their original condition. It is remarkable that the chalk WITH flint abounds in the north of Europe; that WITHOUT flints in the south; while in the northern chalk siliceous animalcules are wanting, and in the southern present in great quant.i.ties. The conclusion seems but natural, that in the one case the siliceous exuviae have been left in their original form; in the other dissolved chemically, and aggregated on the common principle of chemical affinity into nodules of flint, probably concentrating, in every instance, upon a piece of decaying organic matter, as has been the case with the nodules of ironstone in the earlier rocks, and the spherules of the oolite.
What is more remarkable, M. Ehrenberg has ascertained that at least fifty-seven species of the microscopic animals of the chalk, being infusoria and calcareous-sh.e.l.led polythalamia, are still found living in various parts of the earth. These species are the most abundant in the rock. Singly they are the most unimportant of all animals, but in the ma.s.s, forming as they do such enormous strata over a large part of the earth"s surface, they have an importance greatly exceeding that of the largest and n.o.blest of the beasts of the field.
Moreover, these species have a peculiar interest, as the only specific types of that early age which are reproduced in the present day. Species of sea mollusks, of reptiles, and of mammifers, have been changed again and again, since the cretaceous era; and it is not till a long subsequent age that we find the first traces of any other of even the humblest species which now exist; but here have these humble infusoria and polythalamia kept their place on earth through all its revolutions since that time,--are we to say, safe in their very humility, which might adapt them to a greater variety of circ.u.mstances than most other animals, or are we required to look for some other explanation of the phenomenon?
All the ordinary and more observable orders of the inhabitants of the sea, except the cetacea, have been found in the cretaceous formation- -zoophytes, radiaria, mollusks, crustacea, (in great variety of species,) and fishes in smaller variety. In Europe, remains of the marine saurians have been found; they may be presumed to have become extinct in that part of the globe before this time, their place and destructive office being perhaps supplied by cartilaginous fishes, of which the teeth are found in great quant.i.ties. In America, however, remains of the plesiosaurus have been discovered in this part of the stratified series. The reptiles, too, so numerous in the two preceding periods, appear to have now much diminished in numbers.
One, ent.i.tled the mosaesaurus, seems to have held an intermediate place between the monitor and iguana, and to have been about twenty- five feet long, with a tail calculated to a.s.sist it powerfully in swimming. Crocodiles and turtles existed, and amongst the fishes were some of a saurian character.
Fuci abounded in the seas of this era. Confervae are found enclosed in flints. Of terrestrial vegetation, as of terrestrial animals, the specimens in the European area are comparatively rare, rendering it probable that there was no dry land near. The remains are chiefly of ferns, conifers, and cycadeae, but in the two former cases we have only cones and leaves. There have been discovered many pieces of wood, containing holes drilled by the teredo, and thus shewing that they had been long drifted about in the ocean before being entombed at the bottom.
The series in America corresponding to this, ent.i.tled the ferruginous sand formation, presents fossils generally identical with those of Europe, not excepting the fragments of drilled wood; shewing that, in this, as in earlier ages, there was a parity of conditions for animal life over a vast tract of the earth"s surface. To European reptiles, the American formation adds a gigantic one, styled the saurodon, from the lizard-like character of its teeth.
We have seen that footsteps of birds are considered to have been discovered in America, in the new red sandstone. Some similar isolated phenomena occur in the subsequent formations. Mr. Mantell discovered some bones of birds, apparently waders, in the Wealden.
The immediate connexion of that set of birds with land, may account, of course, for their containing a terrestrial organic relic, which the marine beds above and below did not possess. In the slate of Glarus, in Switzerland, corresponding to the English galt, in the chalk formation, the remains of a bird have been found. From a chalk bed near Maidstone, have likewise been extracted some remains of a bird, supposed to have been of the long-winged swimmer family, and equal in size to the albatross. These, it must be owned, are less strong traces of the birds than we possess of the reptiles and other tribes; but it must be remembered, that the evidence of fossils, as to the absence of any cla.s.s of animals from a certain period of the earth"s history, can never be considered as more than negative.
Animals, of which we find no remains in a particular formation, may, nevertheless, have lived at the time, and it may have only been from unfavourable circ.u.mstances that their remains have not been preserved for our inspection. The single circ.u.mstance of their being little liable to be carried down into seas, might be the cause of their non- appearance in our quarries. There is at the same time a limit to uncertainty on this point. We see, from what remains have been found in the whole series, a clear progress throughout, from humble to superior types of being. Hence we derive a light as to what animals may have existed at particular times, which is in some measure independent of the specialties of fossilology. The birds are below the mammalia in the animal scale; and therefore they may be supposed to have existed about the time of the new red sandstone and oolite, although we find but slight traces of them in those formations, and, it may be said, till a considerably later period.
ERA OF THE TERTIARY FORMATION.--MAMMALIA ABUNDANT.
The chalk-beds are the highest which extend over a considerable s.p.a.ce; but in hollows of these beds, comparatively limited in extent, there have been formed series of strata--clays, limestones, marls, alternating--to which the name of the Tertiary Formation has been applied. London and Paris alike rest on basins of this formation, and another such basin extends from near Winchester, under Southampton, and re-appears in the Isle of Wight. There is a patch, or fragment of the formation in one of the Hebrides. A stripe of it extends along the east coast of North America, from Ma.s.sachusetts to Florida. It is also found in Sicily and Italy, insensibly blended with formations still in progress. Though comparatively a local formation, it is not of the less importance as a record of the condition of the earth during a certain period. As in other formations, it is marked, in the most distant localities, by ident.i.ty of organic remains.
The hollows filled by the tertiary formation must be considered as the beds of estuaries left at the conclusion of the cretaceous period. We have seen that an estuary, either by the drifting up of its mouth, or a change of level in that quarter, may be supposed to have become an inland sheet of water, and that, by another change, of the reverse kind, it may be supposed to have become an estuary again.
Such changes the Paris basin appears to have undergone oftener than once, for, first, we have there a fresh-water formation of clay and limestone beds; then, a marine-limestone formation; next, a second fresh water formation, in which the material of the celebrated plaster of Paris (gypsum) is included; then, a second marine formation of sandy and limy beds; and finally, a third series of fresh-water strata. Such alternations occur in other examples of the tertiary formation likewise.
The tertiary beds present all but an entirely new set of animals, and as we ascend in the series, we find more and more of these identical with species still existing upon earth, as if we had now reached the dawn of the present state of the zoology of our planet. By the study of the sh.e.l.ls alone, Mr. Lyell has been enabled to divide the whole term into four sub-periods, to which he has given names with reference to the proportions which they respectively present of surviving species--first, the eocene, (from [Greek], the dawn; [Greek], recent;) second, the miocene, ([Greek], less;) third, older pliocene, ([Greek], more;) fourth, newer pliocene.
EOCENE SUB-PERIOD.
The eocene period presents, in three continental groups, 1238 species of sh.e.l.ls, of which forty-two, or 3.5 per cent, yet flourish. Some of these are remarkable enough; but they all sink into insignificance beside the mammalian remains which the lower eocene deposits of the Paris basin present to us, shewing that the land had now become the theatre of an extensive creation of the highest cla.s.s of animals.
Cuvier ascertained about fifty species of these, all of them long since extinct. A considerable number are pachydermata, {127} of a character approximating to the South American tapir: the names, palaeotherium, anthracotherium, anoplotherium, lophiodon, &c., have been applied to them with a consideration of more or less conspicuous peculiarities; but a description of the first may give some general idea of the whole. It was about the size of a horse, but more squat and clumsy, and with a heavier head, and a lower jaw shorter than the upper; the feet, also, instead of hooves, presented three large toes, rounded, and unprovided with claws. These animals were all herbivorous. Amongst an immense number of others are found many new reptiles, some of them adapted for fresh water; species of birds allied to the sea-lark, curlew, quail, buzzard, owl, and pelican; species allied to the dormouse and squirrel; also the opossum and rac.o.o.n; and species allied to the genette, fox, and wolf.
MIOCENE SUB-PERIOD.
In the miocene sub-period, the sh.e.l.ls give eighteen per cent. of existing species, shewing a considerable advance from the preceding era, with respect to the inhabitants of the sea. The advance in the land animals is less marked, but yet considerable. The predominating forms are still pachydermatous, and the tapir type continues to be conspicuous. One animal of this kind, called the dinotherium, is supposed to have been not less than eighteen feet long; it had a mole-like form of the shoulder-blade, conferring the power of digging for food, and a couple of tusks turning down from the lower jaw, by which it could have attached itself, like the walrus, to a sh.o.r.e or bank, while its body floated in the water. Dr. Buckland considers this and some similar miocene animals, as adapted for a semi-aquatic life, in a region where lakes abounded. Besides the tapirs, we have in this era animals allied to the glutton, the bear, the dog, the horse, the hog, and lastly, several felinae, (creatures of which the lion is the type;) all of which are new forms, as far as we know.
There was also an abundance of marine mammalia, seals, dolphins, lamantins, walruses, and whales, none of which had previously appeared.
PLIOCENE SUB-PERIOD.
The sh.e.l.ls of the older pliocene give from thirty-five to fifty; those of the newer, from ninety to ninety-five per cent. of existing species. The pachydermata of the preceding era now disappear, and are replaced by others belonging to still existing families-- elephant, hippopotamus, rhinoceros--though now extinct as species.
Some of these are startling, from their enormous magnitude. The great mastodon, whose remains are found in abundance in America, was a species of elephant, judged, from peculiarities of its teeth, to have lived on aquatic plants, and reaching the height of twelve feet.
The mammoth was another elephant, but supposed to have survived till comparatively recent times, as a specimen, in all respects entire, was found in 1801, preserved in ice, in Siberia. We are more surprised by finding such gigantic proportions in an animal called the megatherium, which ranks in an order now a.s.suming much humbler forms--the edentata--to which the sloth, ant-eater, and armadillo belong. The megatherium had a skeleton of enormous solidity, with an armour-clad body, and five toes, terminating in huge claws, wherewith to grasp the branches, from which, like its existing congener, the sloth, it derived its food. The megalonyx was a similar animal, only somewhat less than the preceding. Finally, the pliocene gives us for the first time, oxen, deer, camels, and other specimens of the ruminantia.
Such is an outline of the fauna of the tertiary era, as ascertained by the ill.u.s.trious naturalists who first devoted their attention to it. It will be observed that it brings us up to the felinae, or carnivora, a considerably elevated point in the animal scale, but still leaving a blank for the quadrumana (monkeys) and for man, who collectively form, as will be afterwards seen, the first group in that scale. It sometimes happens, however, as we have seen, that a few rare traces of a particular cla.s.s of animals are in time found in formations originally thought to be dest.i.tute of them, displaying as it were a dawn of that department of creation. Such seems to be the case with at least the quadrumana. A jaw-bone and tooth of an animal of this order, and belonging to the genus macacus, were found in the London clay, (eocene,) at Kyson, near Woodbridge, in 1839. Another jaw-bone, containing several teeth, supposed to have belonged to a species of monkey about three feet high, was discovered about the same time in a stratum of marl surmounted by compact limestone, in the department of Gers, at the foot of the Pyrenees. a.s.sociated with this last were remains of not less than thirty mammiferous quadrupeds, including three species of rhinoceros, a large anoplotherium, three species of deer, two antelopes, a true dog, a large cat, an animal like a weasel, a small hare, and a huge species of the edentata. Both of these places are considerably to the north of any region now inhabited by the monkey tribes. Fossil remains of quadrumana have been found in at least two other parts of the earth,- -namely, the sub-Himalayan hills, near the Sutlej, and in Brazil, (both in the tertiary strata;) the first being a large species of semnopithecus, and the second, a still larger animal belonging to the American group of monkeys, but a new genus, and denominated by its discoverer, Dr. Lund, protopithecus. The latter would be four feet in height.
One remarkable circ.u.mstance connected with the tertiary formation remains to be noticed,--namely, the prevalence of volcanic action at that era. In Auvergne, in Catalonia, near Venice, and in the vicinity of Rome and Naples, lavas exactly resembling the produce of existing volcanoes, are a.s.sociated and intermixed with the lacustrine as well as marine tertiaries. The superficies of tertiaries in England is disturbed by two great swells, forming what are called anticlinal axes, one of which divides the London from the Hampshire basin, while the other pa.s.ses through the Isle of Wight, both throwing the strata down at violent inclination towards the north, as if the subterranean disturbing force had WAVED forward in that direction. The Pyrenees, too, and Alps, have both undergone elevation since the deposition of the tertiaries; and in Sicily there are mountains which have risen three thousand feet since the deposition of some of the most recent of these rocks. The general effect of these operations was of course to extend the land surface, and to increase the variety of its features, thus improving the natural drainage, and generally adapting the earth for the reception of higher cla.s.ses of animals.