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measures. We find sea-weed, fine-leaved ferns, tall calamites, and reeds, great pines with cones, tree-ferns, and palms like the modern fan palm. The animal remains are not nearly so numerous as in the coal rocks. There are sponges, corals, sea-urchins, and beautiful shells. We also find fishes like those of the Coal-measures, and the Permian is remarkable as the system where the ancient form of tail, in which the spine of the fish was continued into the upper lobe of the tail, becomes extinct, never to appear again. The reptiles of this system are numerous and perfectly developed, some of them being of gigantic form. Their footprints, in particular, are remarkably abundant and large, and from these alone, the whole animal has been constructed by learned men, the truth of their drawings being proved by subsequent discovery of the entire creature. Even pouched animals, like the kangaroo, are found in the American Permian, thus shewing a gradual but slow approach to modern life forms.

Scenery of Period. The Carboniferous Period was remarkable for the great activity of volcanic agents, but this period seems to have been comparatively tranquil in this respect. The rivers carried in their waters much iron, as they did in the Old Red Period; the seas appear to have been shallow, bearing in solution magnesia and salt, while animal and vegetable life seems scarce, as compared with other epochs. From the existence of a rough conglomerate in the west of England, it has been ably argued that the greater part of the period was one of glacial action, withı icebergs bearing blocks and rounded débris; and if this was the case, we have a conclusive explanation of the scarcity of life during this period.

VIII.-Triassic System.

Description. The upper part of the old system, known as the New Red Sandstone, has received the name Triassic, which means triple, from being found in Germany in three distinct groups, of which the first and third alone exist in Britain.

The system contains sandstones of different colours, shales, and conglomerates; but the distinguishing product is rock-salt. This occurs in beds of from seventy to one hundred feet thick in Cheshire, whence we obtain salt for daily consumption. Salt-springs also abound in salt districts, being formed by the issuing of water through the salt rocks below. The Triassic rocks are found in patches in the British Isles, but extensively on the continent of Europe and in America.

Organic Remains.—The organic remains are very scanty, especially when compared with the exuberance of life in eras before and after. Plants are rare both in number and species. We find horse-tails, calamites, and ferns. The gigantic trees of the Coal-measures no longer exist,

and we have instead short palm-like trees, like the modern cycas. The vegetation is mostly of a tropical kind.

Animals are far from abundant, but are more numerous than the plants. We have no corals, few encrinites, and bone-plated fishes are rare. There are a few shells, some crustaceans, and several great shark-like fishes. Reptiles, however, are numerous and of gigantic size. One brute in particular, called the Labyrinthodon, from the labyrinth-like structure of a section of its teeth, is an uncouth, frog-like creature, with great staring eyes, and immense toothed jaws. The most abundant remains in the Triassic are the great footprints of large lizards. These are found in Scotland, but are so numerous in America, that above one hundred species of creatures have been distinguished, as indicated by these footprints. Huge birds, too, were numerous, and have also left their marks

Fig. 89.-Labyrinthodon.

upon the rocks. These rocks furnish the earliest evidences of warmblooded mammals.

Scenery. The scenery of the old Triassic age is peculiar, and we can form but a dim notion regarding it. We can easily see that the seas were shallow with bordering lagoons, in which the salt waters were evaporated in the strong sun-rays, and left the salt-beds that are now of such service to us. By the muddy rivers lived great crocodiles, that lurked amid the reeds and pines, and fed on shell-fish and crustaceans, and left their footprints on the yielding mud, while on the dry plains above grew plants adapted for an arid soil and tropical climate.

IX.-Oolitic System.

Description.-We have now arrived at a remarkable epoch, whose remains, abundant and wonderful, have been more fully investigated and described by celebrated men than perhaps any other. We begin also a new epoch in geologic history; the forms of life, habits, and scenery are more like those of our own times, and can therefore be restored with the greater certainty.

The term Oolitic is applied to a series of rocks which in England form three distinct groups-the Lias, Oolite Proper, and Wealden.

The Lias is the oldest, and receives its name, a corruption of liers or layers, from the thin variegated beds of which the rocks are composed, and which present a remarkable ribbon-like appearance not easily forgotten. The Oolite is above the Lias, and is so called from the rock being greatly composed of small round grains like the eggs of the cod, so that it signifies the egg-rock, being called also roestone and peastone, according to the size of the particles. These strange granules consist almost entirely of lime or grains of sand coated with lime. The Wealden is the highest rock in the series, and receives its name from being developed largely in the Weald in Kent and Sussex. The name Oolitic has been applied to the whole system, because the egg-structure is common to all the rocks in the series, although the term Jurassic, from its being largely found in Mount Jura, is given to it by some geologists.

The Oolitic system consists of a series of sandstones, limestones, sometimes so hard as to be used as marble, shales, and clays, while ironstone bands, coal, lignite, and jet are abundant. The sandstones are useful as building-stone, the celebrated Bath and Portland stones, so much used in

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London and the south of England, being varieties. The limestones are burned for agricultural purposes; the clays are extensively developed, and receive different names in different parts, and yield alum, sulphur, and fuller's-earth. Ironstone is abundant and good, and furnishes a great part of the iron of Yorkshire, being eleven feet thick. The coal is

1 From Greek ōon, an egg, and lithos, a stone.

workable and abundant, which disproves the notion too prevalent that coal can be obtained only from the Coal-measures. Lignite is a less hard variety of coal, and the jet, which is only a crystallised coal, yields the beautiful jet of Whitby, so much used for ornaments.

Organic Remains.-The remains of plants and animals are so abundant, that their enumeration and description would fill volumes, and we can merely roughly indicate some of their wonderful forms.

Vegetable life was abundant, requiring a warm climate like that of Australia. We find sea-weeds, beautiful tree-ferns, lily-like leaves, palms like the pandanus, and pines like the araucaria and yew. The clays that occur were the very soil on which those ancient forests grew, and in some of them, known as dirt-beds,' the roots are seen in natural position, with part of the trunk broken over, while the tree itself lies close by, as if cut down by the woodman but yesterday.

The animal remains are abundant and remarkable. We find sponges, exquisite star-corals, beautiful encrinites, seaurchins, worms, and lobsters. The shells are very beautiful and varied, the most remarkable being the ammonite, of which there are one hundred and thirty species, and the nautilus. Gigantic cuttle-fish floated and spread their black ink through the oolitic seas. Fishes were numerous and large; huge plated sharks devoured their prey, their very names telling terrible things, such as 'Strong-tooth,' 'Sharp-tooth,' and 'Great-jaw: ' tortoises also floated on the summer seas.

But the most striking remains are those of reptiles, so numerous, strange, and uncouth, that the Oolite has been designated the

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Fig. 91.-Ammonite.

Age of Reptiles.' We find enormous skeletons, some of them thirty feet long, of large lizards and crocodiles, all being more or less strange and terrible.

Fig. 92.-Skeleton of the Ichthyosaurus.

In these rocks, too, a most interesting discovery has lately been made, that of the earliest feathered creature-a real bird-in which the bones,

claws, and full-spread plumage are finely seen. The remains of the earliest warm-blooded animals have also been found—a kind of pouched creature like the kangaroo.

Scenery.—The scenery and animals of the Oolitic Period resemble, to a remarkable extent, those of Australia, both in vegetable and animal remains. The land and water went through many changes during this long period. In the Lias times, the seas were deep and tranquil; under the Oolite, exposed coral beaches were dashed by great breakers, that have left their work in broken shells and marls; while the Wealden seems to have been the carried deposits laid down in the estuary of a mighty river, that rolled into the sea in what is now the south of England; and the present icy lands of the arctic regions were covered with the vegetation of a warm climate, which now appears as Oolitic coal strata.

X.—Chalk or Cretaceous System.

Immediately above the Oolite lies a system in which the chief rock is the well-known substance chalk, and which has hence received the name of the Chalk, or, what is the same thing, Cretaceous1 System. In this system, other rocks also occur, chalk-marl or blue-clay, known by the local name of Gault or Golt; thick beds of green-coloured sand, called Greensand; and, embedded in the chalk, nodules of flint, which when less pure is called Chert; and coal, in Vancouver's Island. The chalk is used for many purposes: when it is burned, it forms a useful lime; when hard enough, is used for building-stone; and when crystallised, forms a fine white marble. The flints are an important ingredient in china, porcelain, and glass, and from the sands we obtain fuller's-earth. The whole system has been generally divided into two groups, the lower being called the Greensand, and the upper the Chalk.

Organic Remains.—The plant-remains are rare and imperfect, and seem to have been all drifted. Leaves of different kinds, palms, fruits, cones, and bits of pines have been discovered. Animal remains, however, are very numerous, and most beautifully preserved. We find sponges, corals, sea-urchins, complete in form and structure, beautiful star-fish, numerous crustaceans, and varieties of the lobster tribe. The shells are plentiful, and exquisitely beautiful in form and even in colouring, and are the finest fossil preservations found in any system-including splendid ammonites and nautiluses, and hundreds of other species, whose mere names would fill pages. Fishes are not numerous, but are well preserved, and, as in other systems, are named from peculiarities in form or structure, such as the 'twisted tooth,' the wrinkle tooth,' 'thick tooth,' and such

1 From Latin crcta, chalk.

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