CHAPTER VIII.

A SKETCH OF THE HISTORY OF THE CREATION AS RECORDED IN THE STRATA OF THE EARTH, SHOWING THAT THE TREES WHICH NOW COVER ITS SURFACE WERE NOT ALL CREATED AT THE SAME TIME, BUT WERE INTRODUCED AS THE EARTH BECAME FITTED FOR THEIR RECEPTION-TREES WERE CREATED IN SUCCESSION-THOSE OF A LOW TYPE OF ORGANIZATION ARE THE MOST ANCIENT INHABITANTS OF THE GLOBE-THE MORE HIGHLY ORGANIZED TREES HAVE BEEN INTRODUCED AT A COMPARATIVELY SPEAKING MODERN GEOLOGICAL EPOCH.

JUST as a tree contains in the woody layers of its stem a record of its progressive life-history through the past years of its existence, so with the organism of the earth. We have recorded, in its strata, a faithful account of the progress of Creation, a history of those physical and organic changes which the earth has undergone, with this difference, that the time expended in producing them is to be estimated not by years, but by myriads of ages, periods of duration all but infinite fragments of eternity. The History of Creation has, in fact, been written in the rocks, which may be regarded as so many separate volumes laid up in the library of Nature. To interpret correctly the language in which this history is written, requires the highest attainments in Natural History and Physics. It has up to the present time been only partially interpreted. The following facts have, however, been fully elicited.

All the elements which enter into the composition of the solid and fluid parts of the earth once existed uncombined, and in the gaseous form. The earth was, during this epoch, an immense sphere of gaseous matter. In the course of vast

periods of time, the attractive forces gradually predominated over the repulsive, the nebulous matter condensed about a common centre, evolved heat and light, and the earth became a radiant star or self-luminous body. Another cycle of ages elapsed, during which there was a continual loss of heat from the surface by free radiation into the stellar spaces; and that surface was ultimately cooled down to the solid crust which now envelopes the fiery nucleus. The earth is therefore an opaque or dark body; and if these views be correct, it is an extinguished star.

About the time that the solid mantle of rock was formed through the cooling of the earth's crust, the air and water were probably separated, the atmosphere was charged with carbonic acid, and the clouds burst in violent showers of rain, originating a hot salt sea. The rind continued to grow thicker as the cooling process went on. In the meanwhile, it became necessarily fissured or cracked in many places, and an uneven surface thus originated, with elevations and depressions and openings, through which poured itself a part of the fiery contents of the earth's nucleus. The earth during this period was covered with an immense number of volcanoes, which were constantly engaged in throwing up showers of ashes, incandescent rocks and melted lava, thus increasing the inequalities of the surface, and forming, in connection with the operation of the boiling waters of these ancient seas, the laminated or slaty rocks known to Geologists as gneiss, micaslate, and talcose-slate. Their formation closed the first great geological period, the Azoic period.

Sublime and terrible must have been the scenery during this epoch; innumerable active volcanoes incessantly thundering, and illuminating the darkened heavens with their raging fires. In such a condition of things, it was impossible that organic bodies, animals and plants, should exist, and accordingly we find no traces of them in these ancient rocks.

In order for living beings to diffuse themselves over the earth, the temperature must be lessened, and an earthy soil must be created, on which plants can grow, and through them animals be nourished. Plants live on inorganic matter, on

water, carbonic acid, ammonia, and certain salts; animals, on the contrary, require plants and other animals for their existence. Such a soil forms itself only in the course of ages, out of the underlying rocks. Through the chemical influence of the air, and the solvent and mechanical power of the rains, the rocky surface was gradually broken up, and the loose material was either left lying on the surface, or, driven along by torrents of water, was deposited in other places at a distance. Rocks composed of matter which has thus been deposited from water are called sedimentary rocks, and we find first in the most ancient of these rocks the remains of plants and animals, the so-called fossils.

The time occupied in the formation of these ancient deposits is called for this reason by Geologists the Paleozoic period, because they contain the first germs of higher organic forms, and are the repository of its most ancient life. The Cambrian, Silurian, and Devonian formations are the oldest historical rocks, and the fossils which they contain prove that the earth was at this time no Eden, but, on the contrary, a monstrous muddy swamp. Water appears to have predominated over the land. Among animals the fish held the highest rank. There was an abundance of shell-fish and corals, and a crustaceous swimming animal called a trilobite. The air contained a great amount of carbonic acid gas.

The plants belong to the Cryptogamous or flowerless division, and are decidedly low in organization. They consist of gigantic calamites, plants allied to the horsetail (Equisetum), ferns, and arborescent club-mosses (Lycopodium), called Lepidodendra-in fact, such plants as are found now in swamps, and whose size is at present very diminutive. An almost endless ocean yet covered the earth's surface. Only here and there an island was visible, rugged and torn, and which the first offspring of the young creation covered. Land was, indeed, created, and the waves of these ancient seas broke against the rocks as now, and plowed out for themselves gulfs and bays. In the interior of the earth the wild efforts and strength of the fire had, in some measure, abated. The volcanoes were less numerous. Yet the blue heavens were not

visible through the cloudy atmosphere. Dense vapors arose from the ocean, and fell in violent showers over the land, returning back to that reservoir in ten thousand roaring torrents. This period has been called by Agassiz the Age of Fishes. There were neither reptiles, birds, nor mammals then in existence.

Toward the close of the Paleozoic period, the earth appears to have presented the appearance of one vast archipelago, or collection of islands, and vegetation was developed on the grandest scale. It was during this epoch that the coal was deposited, as only on the coasts of tropical islands could such plants grow as are found fossil in the coal formation. The vegetable remains are mostly found, not in the coal, but in the accompanying clayey and sandy soil with which the coal is interstratified.

From these remains it can be proved that splendid forests grew on the boggy soil of these islands. Here elevated itself a tree fern, its summit penetrating the dark clouds which obscured the heavens; there, a gigantic lycopodium or club moss. Calamites and equisetaceae were abundant; and, in addition to this, we find traces of coniferous plants, or plants allied to the Fir tree, and resembling the Norfolk Island Pine, (Araucaria excelsa.) Barren uniformity, however, marked the character of these forests. Only seven hundred and fifty plants are at present known to Naturalists, which were at this time diffused over the whole earth; whilst to-day, in Europe, one of the smallest dvisions of the earth, more than ten thousand species are known. The earth at the time of the stonecoal formation was yet too warm for the sun's rays to produce any essential influence on the climatic conditions. The temperature was pretty much the same all over the earth. Hence the stone-coal plants are the same, although found in countries thousands of miles apart. Even the poles of the earth were covered with a tropical vegetation, although now cooled down so as to be covered with a mantle of everlasting ice and snow. This opinion has been advanced by some Naturalists; but as light is nessary to the formation of plants, and as the poles are deprived of its influence during a part of the

year, this opinion must be received with some degree of restriction.

The animals of the Stone-coal period resemble in many respects those of the preceding formations. The crustaceans have, however, improved. In addition to the trilobites, we have the horse-shoe crabs, and other gigantic forms. We also meet with traces of insects and scorpions. These appear to have been the only inhabitants of these swampy forests. No mammalia pastured beneath their shade; no birds warbled forth their melody, or nestled amongst the branches of these leafless, flowerless trees. Trees with true leaves and flowers. had not made their appearance. The atmosphere was not yet fitted for their growth. With the exception of the Fir-trees, with their needle-shaped leaves, the vegetation was wholly cryptogamous, and decidedly low in organization. Every Botanist who examines the coal plants is necessarily impelled to this conclusion. There is no denying the evidence of the. rocks.

The Paleozoic rocks, which contain the fossil remains of the first inhabitants of the earth, extend from the Cambrian formation as far as the Magnesian limestone, which lies above the coal, and, together with the Old Red Sandstone, constitutes the Zechstein formation of the German geologists.

A careful examination of the fossil remains found in these rocks, by the most distinguished Naturalists, has developed the interesting fact, that the first inhabitants of the world were a few sea-weed zoophytes and shell-fish, and that, throughout the whole of the immense period of time occupied in the formation of these rocks, vegetation did not advance further than the Coniferæ or Pine family, the highest rank of the animal creation being a low order of fishes.

The period immediately succeeding the Stone-coal era was characterized by great volcanic activity: the rocks were upheaved, and storm and annihilation swept over the islandforests of the Stone-coal landscape, millions of gigantic trees being buried beneath the raging floods.

The great amount of carbonic acid removed from the atmosphere by the luxuriant vegetation thus entombed, rendered