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obtained, one of which is a huge kind of crab, sometimes six feet long, with terrible-looking toothed claws, called the Pterygotus or ear-wing. Reptiles are also found, two very large lizards being most frequent.

But by far the most numerous specimens of ancient life are gigantic fishes. These creatures are all covered with hard bony scales, burnished with enamel, with fierce teeth, and great fins armed with long sharp spines, with which they defended themselves or attacked their enemies.

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These fishes have received different names, according to peculiarities in their structure or appearance, and have been brilliantly described by Hugh Miller, who, when cutting the Old Red Sandstone as a mason, had his attention first drawn to geology by the brilliancy of their scaly

armour.

Scenery of Period. The wide oceans in which the thin fine-grained flags were deposited must have been smooth and tranquil. Round the coral islands that rose in its gleaming waters coursed huge fierce fishes. The sandy shores became the coarser sandstone. Within tidemark, numerous great crabs lived, and caught their prey in their toothed claws; shrimp-like creatures danced over the sands, and in them worms burrowed; the waves ebbed and flowed, leaving their ripple-marks on the rocks we now see; gravel beaches fringed the shore, where the surges rounded the pebbles and rolled the stones, creating our conglomerates;

1 Pteron, a wing, and ous, otos, the ear.

and rain-showers fell over the land, and left there the sandy bays pelted with their drops; and forests of sea-weed waved in the green waters and on the rocky reaches; and shells adorned the rocks. Into the seas flowed great rivers, whose banks were fringed with reeds and flags; ferns waved on the hill-side, tree-ferns reared aloft their feathery plumes, and broad-leaved plants clothed the surface of the landscape; while large reptiles roamed through the forests, or crushed the reeds by the riversides.

VI.-Carboniferous System.

Description.-Above the Devonian rocks lies a series of strata perhaps more generally known than any other, as they afford us what is so necessary to our comfort, the remarkable combustible stone called coal. They receive the name Carboniferous from the fact that they contain coal, although they furnish many other important products. These rocks are found in most regions of the globe; but in none are they more fully developed, compared with the size of the country, than in the British Isles. They consist of sandstones, limestones, shales, clays, ironstone, and coal. The sandstone is of various qualities and colours, some of it very valuable and durable; the beautiful stone of which the New Town of Edinburgh is built being from this system. The limestones are largely developed, and are of the greatest service for building and agriculture. The shales have of late become very valuable, as from them are distilled oils and other substances, including the celebrated paraffin oil and candles. The ironstone is of the very greatest value.

It must not be thought that coal is found only in the Carboniferous rocks. Coal being simply compressed vegetable matter, may be found in any rock-system in which plants are preserved, and is so found in other systems, and often in great abundance. For example, the coal-fields of Virginia, some thirty or forty feet thick, belong to another system, the Oolitic; and coal of various kinds can be obtained, more or less, from most systems.

The same is true of other products, such as limestone, sandstone, and iron, which last, though found in greatest abundance in this system, yet occurs in many others.

The Coal-strata are divided into three great groups-the Upper and Lower Measures, and a thick deposit of limestone, which separates them, known as the Mountain or Carboniferous Limestone. The Upper Coalmeasures are also called the True Coal-measures, as they contain the greatest amount of workable coal; the Lower Coal-measures consist chiefly of sandstones and shales. The Mountain Limestone is so called because where it is most largely developed, as in Yorkshire, it rises into hills with great limestone cliffs.

The industrial products of this system are numerous and important. We have coal of all kinds for household purposes and gas; iron, sandstone, limestone, and fire-clay. From the shales are obtained alum and the remarkable paraffin oil; and so abundant in America and elsewhere is

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this ancient oil, that when the earth is bored, a flood of it issues forth yielding thousands of gallons daily.

Organic Remains. The organic remains found in this system are very abundant and remarkable. Plants are numerous, varied, and beautiful.

THY

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Ferns are found with the most perfect fronds, as distinctly traced upon the rock as a modern dried fern on the pages of book. We find also large and beautiful club-mosses exquisitely exhibited. But the most luxuriant and beautiful of all are the great pine-like araucarias, the treeferns, and tall reeds that grew in boundless swamps and jungles along

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the banks of the rivers that swept in mighty volume to the carboniferous sea We see the lepidodendron1 or scale-tree, with its pine-like leaves, beautiful scaly bark, and great cones, from which the seed of the ancient pine may be gathered in hundreds to this very day; the sigillaria 2 or seal-tree, with its seal-stamped trunk and great pitted and branched roots, long thought to be a tree of a different species; calamite 3 or reed, rising high into the air, like the bamboo, with its joints and leafy branchlets; and many more, equally beautiful and well preserved.

The animal remains found are numerous and strange. Corals are abundant and beautiful; but no sea-creature was more common than the encrinite, which rose on its long jointed stalk, bearing its cup-shaped body, with its hundred fingers, that moved on all sides to secure its prey, like

the anemone of our own seas. The remains of encrinites are in some places so abundant as to form thick beds of limestone, called Encrinital Limestone; and when these, hard as marble, are polished, they present a most beautiful surface, through which is seen the exquisite carving of the encrinite stars. The little joints of the stems are often found detached, with a hole through the centre; these are known as Fairy Beads and as St Cuthbert's Beads; and when strung together, were used as a rosary, and no more beautiful ornament was ever hung round the neck of a saint. We also find star-fishes and sea-urchins; and the spines of the latter may be seen running through the limestone like threads of burnished silver. The shells are very numerous and varied; univalves and bivalves of both sea and land being everywhere found, and some of these can hardly be distinguished from shells gathered on our own shores, so perfect are they in form, colour, and structure. They may be detached from the rock, and collections made of them as easily as of modern shells. We find also crustaceans of different kinds; and the last trilobites are found in the Coal-measures. Fishes are numerous and formidable, but less so than in the Old Red Period. Reptiles in both salt and fresh water have also

Fig. 88.-Fragment of Encrinital Limestone.

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1 From Latin lepis, a scale, and dendron, a tree.
2 From Latin sigilla, a seal.

3 From Latin calamus, a reed.

left their remains, and their footprints may be seen on certain sandstones as distinct as if made but yesterday on the soft mud.

Scenery of the Period. In this remarkable period there stretched wide shallow seas, in which sported huge sharks, and whose waters washed the shores of many islands, guarded by great coral reefs, where the beautiful encrinite spread its waving arms. By the shores lived numerous shells, often in immense beds, that now form the mussel-band of the miner; and into these seas flowed Amazonian rivers, bearing into the deep the spoils of their wooded and reedy shores. By their wide estuaries and along their banks lay extensive impassable swamps and jungles, in which gigantic reeds, calamites, and tree-ferns flourished in tropical luxuriance, and amidst these lurked fierce crocodiles and mighty lizards, which have left their footprints on the yielding mud. The whole surface of the land was covered with tall pines and tree-ferns; the seal-palm, the scaletree, and star-leaf shot into the air in impenetrable thickets, shaking their numerous cones in the breeze, while the hum of insects might be heard in their still recesses. In the distance might be seen towering snow-peaks, and here and there the smoke of the volcano, the existence of which was felt in the numerous earthquakes that shook the ground.

VII.-Permian System.

Description. Immediately above the Carboniferous strata, we find certain strata that used to be called, as already explained, the New Red Sandstone, in contrast with the rocks below them, called the Old Red Sandstone. This New Red Sandstone series has been of late more thoroughly examined, and found to consist of two distinct portions, whose remains are so different that the series has been formed into two distinct systems, known as Permian and Triassic. The name Permian has been given to the system we now describe, from being developed very extensively in Perm, a province in the north-east of Russia. These rocks are found in many parts of the world, and largely in Scotland, England, Germany, and Russia. They consist of red and whitish sandstones, shales, and limestones, containing much magnesia. The rocks are remarkably variegated in colour, so much so as to be called the Variegated System ; while the limestone receives the distinctive name of the Magnesian Limestone. As the old name suggests, the sandstone is of a reddish hue, and the two chief rocks, therefore, are the Red Sandstone and the Magnesian Limestone. The sandstones are used for building, as are also the limestones, which have been employed in the construction of the Houses of Parliament. Copper is also extensively obtained from one of its shales in Germany, and also lead and zinc, but not very abundantly.

Organic Remains. The plants resemble greatly those of the Coal

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