XXV.—Ideal Landscape of the Pliocene Period.

THE PLIOCENE PERIOD. 37/

In the mountainous regions of the Alps it is always difficult to determine the age of beds, in consequence of the disturbed state of the strata; for instance, the lofty chain of the Swiss Jura consists of many parallel ridges, with intervening longitudinal valleys; the ridges formed of contorted fossiliferous strata, which are extensive in proportion to the number and thickness of the formations which have been exposed on upheaval. The proofs which these regions offer of comparatively recent elevation are numerous. In the central Alps, Cretaceous, Oolitic, Liassic, and Eocene strata are found at the loftiest summits, passing insensibly into metamorphic rocks of granular limestone, and into talcose and mica-schists. In the eastern parts of the chain the older fossiliferous rocks are recognised in similar positions, presenting signs of intense Plutonic action. Oolitic and Cretaceous strata have been raised 12,000 feet. Eocene 10,000, and Miocene 4,000 and 5,000 feet above the level of the sea. Equally striking proofs of recent elevation exist in the Apennines; the celebrated Carrara marble, once supposed — from its crystalline texture and the absence of fsssils, and from its resting — i. on talcose schists, 2. on quartz and gneiss — to be very ancient, now turns out to be an altered limestone of the Oolitic series, and the underlying crystalline rocks to be metamorphosed Secondary sandstones and shales. Had all these rocks undergone complete metamorphism, another page in the earth's history would have been obscured. As it is, the proofs of what we state are found in the gradual approach of the rocks to their unaltered condition as the distance from the intrusive rock increases. This intmsive rock, however, does not always reach the surface, but it exists below at no great depth, and is observed piercing through the talcose gneiss, and passing up into Secondary strata.

At the close of this epoch, therefore, there is every probability that Europe and Asia had pretty nearly attained their present general configuration.

378

QUATERNARY EPOCH.

The Quaternary epoch of the history of our globe commences at the close of the Tertiary epoch, and brings the narrative of its revolutions down to our own times.

The tranquillity of the globe was only disturbed during this era by certain cataclysms whose sphere was limited and local, and by an interval of cold of very extended duration; the deluges and the glacial period — these are the two most remarkable peculiarities which distinguished this epoch. But the fact which predominates in the Quaternary epoch, and distinguishes it from all other phases of

the earth's history is the appearance of man, the culminating and supreme work of the Creator of the universe.

In this last phase of the history of the earth geology recognises three chronological divisions:— 1. The European Deluges. 2. The Glacial Period. 3. The creation of man and subsequent Asiatic Deluge.

Before describing the three orders of events which occurred in the Quaternary epoch, we shall present a brief sketch of the organic kingdoms of Nature, namely, of the animals and vegetables which flourished at this date, and the new formations which arose. Lyell, and some other geologists, designate this the Post-Tertiary Epoch, which they divide into two subordinate groups. — i. The Post- Pliocene Period; 2. The Recent or Pleistocene Period.

Post-Pliocene Period.

In the days of Cuvier the Tertiary formations were considered as a mere chaos of superficial deposits, having no distinct relations to each other. It was reserved for the English geologists, with Sir Charles Lyell at their head, to throw light upon this obscure page of the earth's history; from the study of fossils, science has not only

re-animated the animals, it has re-constructed the theatre of their existence. We see the British Islands now a straggling archipelago, and then the mouth of a vast river, of which the continent is lost; for, says Professor Ramsay, " We are not of necessity to consider Great Britain as having always been an island; it is an accident that it is an island now, and it has been an island many times before." In the Tertiary epoch we see it surrounded, then, by shallow seas swarming with numerous forms of animal life; islands covered with bushy Palms; banks on which Turtles basked in the sun; vast basins of fresh or brackish water, in which the tide made itself felt, and which abounded with various species of sharks; rivers in which Crocodiles increased and multiplied; woods which sheltered numerous Mammals and some Serpents of large size; fresh-water lakes which received the spoils of numerous shells. Dry land had increased immensely. Groups of ancient isles we have seen united and become continents, with lakes, bays, and perhaps inland seas. Gigantic Elephants, vastly larger than any now existing, close the epoch, and probably usher in the succeeding one; for we are not to suppose any sudden break to distinguish one period from another in Nature, although it is convenient to arrange them so for the purposes of description. If we may judge from their remains, these animals must have existed in great numbers, for it is stated that on the coast of Norfolk alone the fishermen, in trawling for oysters, dredged up between 1820 and 1833, no less than 2,000 molar teeth of Elephants. If we consider how slowly these animals multiply, these quarries of ivory, as we may call them, must have required many centuries for their production and accumulation.

The same lakes and rivers were at this time occupied, also, by the Hippopotamus, as large and as formidably armed as that now inhabiting the African solitudes; also the two-horned Rhinoceros; and three species of Bos, one of which was hairy and bore a mane. Some Deer of gigantic size, as compared with living species, bounded over the plains. In the same savanahs lived the Reindeer, the Stag, a Horse of small size, the Ass, the Bear, and the Roe, for Mammals had succeeded the Ichthyosauri of a former age. Nevertheless, the epoch had its tyrants also. A Lion, as large as the largest of the Lions of Africa, hunted its prey in the British jungles. Another animal of the feline race, the Machairodiis (Fig. 179), was probably the most ferocious and destructive of Carnivora; bands of Hycenas and a terrible Bear, surpassing in size that of the Rocky Mountains, had established themselves in the caverns; two species of Beaver made their appearance on the scene.

Fig. 179. — a, Tooth of Machairodus, imperfect below, natural size; h, outline of cast of tooth, perfect, half natural size; c, tooth of MegalosGurus, natural size.

The finding of the remains of most of these animals in caverns was perhaps among the most interesting discoveries of geology. The discovery was first made in the celebrated Kirkdale Cave in Yorkshire, which has been described by Dr. Buckland; and afterwards at Kent's Hole, near Torquay. This latter pleasant Devonshire town.

is built in a creek, shut out from exposure on all sides except the south. In this creek, hollowed out of the rocks, is the great fissure or cavern known as Kent's Hole; like that of Kirkdale, it has been under water, from whence, after a longer or shorter interval, it emerged, but remained entirely closed till the moment when chance led to its discovery. The principal cavern is 600 feet in lengthy with many crevices or fissures of smaller extent traversing the rock in various directions. A bed of hard stalagmite of very ancient formation, which has been again covered with a thin layer of soil, forms the floor of the cavern, which is a red sandy clay. From this bed of red loam or clay was disinterred a mass of fossil bones belonging to extinct species of Bear, Lion, Rhinoceros, Reindeer, Beaver, and Hyaena. Such an assemblage gave rise to all sorts of conjectures. It was. generally thought that the dwelling of some beasts of prey had been discovered, which had dragged the carcases of elephants, deer, and others into these caves, to devour them at leisure. Others asked if, in some cases, instinct did not impel sick animals, or animals broken down by old age, to seek such places for the purpose of dying in quiet; while others, again, suggested that these bones might have been engulfed pell-mell in the hole during some ancient inundation. However that may be, the remains discovered in these caves show that all these Mammals existed at the close of the Tertiary epoch, and that they all lived in England. What were the causes which led to their extinction? It was the opinion of Cuvier and the early geologists that the ancient species were destroyed in some great and sudden catastrophe, from which none made their escape. But recent geologists trace their extinction to slow, successive, and determinative action due to local causes, the chief one being the gradual lowering of the temperature. We have seen that at the beginning of the Tertiary epoch, in the older Eocene age, palms, cocoa-nuts, and acacias, resembling those now met with in countries more favoured by the sun, grew in our island. The Miocene flora presents indications of a climate still warm, but less tropical; and the Pliocene period, which follows, contains remains which announce an approach to our present climate. In following the vegetable productions of the Tertiary epoch, the botanist meets with the floras of Africa, South America, and Australia, and finally settles in the flora of temperate Europe. Many circumstances demonstrate this decreasing temperature, until we arrive at what geologists call ihi^ glacial period — one of the winters of the ancient world.

But before entering on the evidences which exist of the glacial era we shall glance at the picture presented by the animals of the period; the vegetable products we need not dwell on — it is, in fact, that of our own era, the flora of temperate regions in our own epoch. The same remark would apply to the animals, but for some signal exceptions. In this epoch Man appears, and some of the Mammals of the last epoch, but of larger dimensions, have long disappeared. The more remarkable of these extinct animals we shall describe, as we have those belonging to anterior ages. They are not numerous; those of our hemisphere being the Mammoth, Elephas primigeniiis; the Bear, Ursus spelcBus; gigantic Lion, Felis spelcEa; Hysena, HycBua spelcea; Ox, Bison priscus^ Bos primigenius; the gigantic Stag, Cervus megaceros; to which we may add the Dinornis and Epiornis, among birds. In America there existed in the Quaternary epoch some Edentates of colossal dimensions and of very peculiar structure, these were Megathermm, Megalonyx, and Mylodon; we shall pass these animals in review, beginning with those of our own hemisphere. The Mammoth, the skeleton of which is represented in Fig. 180, surpassed the largest existing Elephants of the tropics in size, for it was from sixteen to eighteen feet in height. The teeth, and the size of the monstrous tusks, much curved, and with a spiral turn outwards, and which were from ten to fifteen feet in length, serve to distinguish the Mammoth from the two Elephants living at the present day, the African and the Indian. The form of its teeth permits of its being distinguished from its ally, the Mastodon; for while the teeth of the latter have rough mammillations on their surface, those of the Mammoth, like those of the living Indian Elephant, have a broad united surface, with regular furrowed lines of large curvature. The teeth of the Mammoth are four in number, like the Elephants, two in each jaw when the animal is adult, its head is elongated, its forehead concave, its jaws curved and truncated in front. It has been an easy task, as we shall see, to recognise the general form and strurture of the Mammoth, even to its skin. We know beyond a doubt that it was thickly covered with long shaggy hair, and that a copious mane floated upon its neck and along its back; its trunk resembled that of the Indian Elephant; its body was heavy, with a tail naked to the end, which was covered with thick tufty hair, and its legs were comparatively shorter than those of the latter animal, many of the habits of which it nevertheless possessed. Blumenbach gave it the specific name of Elephas priinigenhis.

Page 57 of 79