voracity, and their invariable presence wherever animal or vegetable matter is undergoing decomposition in water. Surely we must be indebted to them—the ever active and invisible scavengers of the world-for the salubrity of our atmosphere; but they perform a still more important office, perhaps, in preventing the gradual diminution of the present amount of organized matter upon the earth. And it is not difficult to understand in what way this result is produced, for, when the organic matter is in that state of comminution and decay which immediately precedes its return from the organic to the inorganic world, these wakeful members of nature's invisible police are everywhere ready to arrest the fugitive particles, and turn them back into the ascending stream of animal life. Becoming the food of the smaller infusorial animalcules, they again supply the voracity of the larger ones, and of numerous other small animals, which in their turn are devoured by larger ones, and so, by degrees, the substance fit for the nourishment of the most highly organized classes is brought back by a short route from the extremity of the realms of organized matter.

Skeletons Traveling in the Air.

It is a remarkable and very interesting fact with regard to these animalcules, that their light skeletons, are capable of being transported by the air in the form of fine dust to the distance of many hundred miles out at sea; and the quantity so transported is often sufficient to cloud the air, and form a sensible deposit on the decks and rigging of ships. The microscope alone is capable of proving whence this dust comes, but, with its aid, they can be recognised, identified, and traced to that continent or island, which is not always the one nearest at hand, where they are indigenous. It will not be surprising, also, since we thus find the bodies of the animalcules themselves carried along by millions through the air, that their eggs may be carried yet farther, and prove a bond of union between distant lands, whose other inhabitants have no relation. Who could have imagined that the atmosphere is in this way the means of conveying to distant spots the invisible stony frame-work and the eggs of these little bodies? And yet it is impossible to doubt the importance of such a mean: of communication in the animal economy.

The first animals produced, after the infusorias and microscopic plantanimals, in the still warm, dense waters of the primeval seas, were such as sea-stars and sea-hedgehogs, whose very numerous organs present a symmetry absent in the infusorias. These beautiful flower-like zoophytes, covered the bottom of the sea where they were planted, rising, like a submarine forest, to an elevation of several yards. The various solid parts of

their bodies had already some analogy with those constituting the skeleton of the superior animals, and thus formed, around a stem or vertebral column, a complex framework destined to protect the vital organs.

Innumerable Insects Building Islands.

Animals of this low organization multiply rapidly, and are capable of making very important geological deposits. While, indeed, the vertebrated animals and the larger and more complicated molluscs live for some considerable time, and modify during that time the general conditions of organic existence, these little creatures may, by their rapid secretion of solid matter from the water, and (owing to their brief existence) equally rapid deposition of it in a solid form, lay the foundation of islands, and even of new continents. The land thus formed may, when brought above the sea level, be destined to last, with little change, throughout many successive geological epochs, during which group after group of species of the higher animals may be introduced and destroyed, some of which leave no indication of their ever having existed, while others are represented by a few bones, a tooth, a scale, or perhaps only by the faint impress of a footstep.

How important, then, it becomes that we should understand these, the common hieroglyphics, even if their meaning is less full, and when they speak an earlier and a simpler language than the others, since the sacred characters which tell of higher events are so infinitely more rare, and for that reason also more difficult to render. The most enduring monuments of man himself-his cities, his pyramids, and his lofty columns-are, in many cases, built of these far more ancient and far more lasting objects, which withstand the shock of earthquakes and the hand of time, and which scarcely yield, even at last, to the slow influence of crystalline forces, re-arranging the particles by the aid of heat and electricity.

CHAPTER II.

PRE-HISTORIC MONSTERS OF LAND AND SEA.

by

Astonishing Convulsions and Physical Revolutions-Fabulous Traditions-Histories of Reptiles Written in Stone-Gigantic Inhabitants of the Ancient GlobeSkeletons of Extinct Animals found in Rocks-A Winged Monster-Combat Between Enormous Reptiles-The Huge Megalosaurus-A Vampire of the PreHistoric Age-A Creature Curiously Constructed-The Wing-Fingered BirdThe Famous Iguanodon-A Vivid Picture of the Early Ages-Animal Life in the Oolitic Period-A Dragon on Wings-The Remarkable Dinotherium-The Strange Hand-Animal-The Glyptoden-The Primeval Armadillo-A Creature that could Swallow an Ox-Megatherium-Animals in Mortal Combat-A Bird Without Wings-Flowers and Plants in Stone-Fossil Fishes-Beautiful Shells. HE observer who glances over a rich and fertile plain, watered rivers and watercourses which have, during a long course of ages, pursued the same uniform and tranquil course; the traveller who contemplates the walls and monuments of a great city, whose foundations are lost in the night of ages, witnessing, apparently, to the unchangeableness of things and places; the naturalist who examines a mountain or other locality, and finds the hills and valleys and other ac cidents of the soil in the very spot and condition in which they are described by history and tradition;-neither of these inquirers would at first suspect that any serious subversion had ever occurred to disturb the surface. Nevertheless, the spot has not always presented the calm aspect of stability which it now exhibits; in common with every spot of earth, it has had its convulsions, its physical revolutions, whose story we are about to trace. Buried in the depths of the soil, for example, in one of those vast excavations which the intrepidity of the miner has dug, in search of coal and other minerals and metals, there are numerous phenomena which strike the mind of the inquirer, and carry their own conclusions with them. A striking increase of temperature occurring in these subterranean places is one of the most remarkable of these. It is found that the temperature of the earth rises one degree for every sixty or seventy feet of descent from its surface.

If the interior of the beds be examined minutely, if, armed with the miner's pick and shovel, the surrounding earth is dug up, it is not impossible that the very first efforts at mining may be rewarded by the discovery of some fossil form no longer found in the living state. The remains of

plants, and animals belonging to the first ages of the world, are, in fact, very common; entire mountains are formed of them, and, in some localities, the soil can scarcely be touched at a certain depth without yielding fragments of bones and shells, or the impression of fossilized animals and vegetables, the buried remains of extinct creations. These bones-these remains of animals or vegetables which the pick of the young geologist has torn from the soil-belong probably to some organic species which no longer exists anywhere: it cannot be compared to any animal or plant living in our times; but it is evident that these beings, whose remains are. now so deeply buried, have not always been so covered; they lived on the surface of the earth as plants and animals do in our days, for their organization is essentially the same. The beds in which they now repose, then, must in other times have formed the surface; and the presence of these bones and fossils proves that the earth has suffered great changes.

These remains of the primitive creation had long been examined and classed scientifically as freaks of nature, for so we find them described in the works of the ancient philosophers who wrote on natural history, and in the few treatises on natural history which the middle ages have bequeathed to us. Fossil bones, especially those of elephants, were known to the ancients, giving birth to all sorts of legends and fabulous histories: the tradition which attributed to Achilles, to Ajax, and the other heroes of the Trojan war, a height of twenty feet, was traceable no doubt to the discovery of the bones of elephants near their tombs. In the time of Pericles we are assured that in the tomb of Ajax a knee-bone of that hero was found, which was as large as a dinner-plate. This was probably only the fossilized knee-bone of an elephant.

Tracks of Reptiles in Stone.

The imprints left upon the earth or sand, which time has hardened into sandstone, furnish to the geologist a series of valuable indications. The reptiles of the ancient world, the turtles in particular, have left upon the sands, which time has transformed into blocks of stone, imprints which evidently represent the exact mould of the feet of these animals. These impressions have sometimes been sufficient for naturalists to determine to what species the animal belonged which thus left its impress on the wet soil. Some of these present traces of the steps of the great reptile known as the labyrinthodon or cheirotherium, whose foot resembles the hand of a man. Another well-known impression is supposed to have been the impress of the foot of some great turtle.

The historian and antiquarian may traverse the battle fields of the Greeks and Romans, and search in vain for traces of these conquerors, whose

armies ravaged the world. Time, which has overthrown the monuments of their victories, has also effaced the imprint of their footsteps; and of millions of men besides, whose invasions have spread desolation over Europe, there is not even a trace of their footsteps. These reptiles, on the contrary, which ranged for thousands of years on the surface of our planet when still in its infancy, have impressed on the soil indelible recollections of their existence. Hannibal and his legions, the barbarians and their savage hordes, have passed over the land without leaving a material mark of their passage, while the poor turtle which drags itself along on the silent shore of the primitive seas has bequeathed to learned posterity the image and imprint of a part of its body. These imprints may be perceived as distinctly marked on the rocks as the traces left in moist sand or in newly-fallen snow by some animal under our own eyes. What grave reflections should be awakened within us at the sight of these blocks of hardened earth, which thus carry back our thoughts to the first ages of the world, and how insignificant the discoveries of the archæologist who throws himself into ecstacies before some piece of Greek or Etruscan pottery, when compared with these veritable antiquities of the earth!

Vast Antediluvian Forests.

As already observed, the products of the first epoch of the globe were vegetable, consisting of immense forest growths, from which vast coalbeds were formed to furnish fuel for the subsequent races of men. The secondary epoch contrasted strongly with that which preceded it, for now the wonders of animal life burst upon us with their unique and fantastic shapes. The reptiles astonish us by their number, their gigantic size, and their unwonted forms; antique and incomprehensible inhabitants of the globe, reproduced in all their parts to our wondering eyes by the genius of a Cuvier and an Owen! It is to this epoch that the name of the reptilian age may be most appropriately given, so completely did these creatures then predominate on the globe; it was the age of a throng of frightful lizards, compared to which our own are mere pigmies, and which possessed a form and character of their own. At this time lived the ichthyosauri, veritable fish-lizzards, as is indicated by their name. These reptiles, which must have spread terror through the ancient seas, attained an enormous length. Their whole organization is a series of surprises. With the vertebræ of the fish they have the fins of a dolphin; and while armed with the teeth of a crocodile, they display an optic globe which is without any parallel. This eye, the bulk of which was sometimes as large as a man's head, was protected in front by a framework of bony plates, and was beyond all doubt the most powerful and perfect