GEOLOGICAL SKETCH OF THE EARTH.

Geological periods. — Primitive state of the globe.

— Primary period.

— Transition period.

— Secondary period.

— Tertiary period.

— Diluvian period.

— Post-diluvian, or present, period. Birth of man.

GEOLOGICAL PERIODS.

— The Earth preserves within itself the evident traces of its formation. Its phases can be followed with mathematical precision in the different terrains that constitute its framework. The body of these studies forms the science called Geology, a science born of this century (the nineteenth) which has cast light upon the much-controverted question of the origin of the terrestrial globe and of that of the living beings inhabiting it.

On this point there is no mere hypothesis; there is the rigorous result of the observation of facts, and in the face of facts no doubt is justified.

The history of the Earth's formation is written in the geological strata in a far more certain manner than in preconceived books, because it is Nature herself who speaks, who lays herself bare, and not the imagination of men creating systems.

Wherever traces of fire are noted, it can be said with certainty that there was fire there; wherever the traces of water are seen, it can be said that water was there; wherever those of animals are observed, it can be said that animals lived there.

Geology is, then, a science entirely of observation; it draws deductions only from what it sees; on doubtful points it affirms nothing; it issues no debatable opinions, because it awaits from more complete observations the solution sought.

Without the discoveries of Geology, as without those of Astronomy, the Genesis of the world would still be in the darkness of legend. Thanks to them, man today knows the history of his dwelling place, the structure of fables which surrounded his cradle having collapsed, never to rise again.

— In all terrains where there are trenches, excavations natural or made by man, one notices what is called stratifications, that is, superimposed layers. Those which present this arrangement are designated by the name of stratified terrains. These layers, of a thickness varying from a few centimeters to 100 meters and more, are distinguished from one another by their color and by the nature of the substances of which they are composed. Works of engineering, the boring of wells, the exploitation of quarries and, above all, of mines, have made it possible to observe them to great depth.

— The layers are generally homogeneous, that is, each one constituted of the same substance, or of diverse substances, but which existed together and formed a compact whole. The line of separation which isolates them from one another is always sharply furrowed, as in the courses of a building. Nowhere do they appear mingled and lost one in another, at the points of their respective limits, as happens, for example, with the colors of the prism and of the rainbow.

By these characteristics it is recognized that they were formed successively, depositing one upon another, under different conditions and from different causes. The deepest are naturally those which formed first, the most superficial having formed later. The last of all, that which is found at the surface, is the layer of vegetable earth, which owes its properties to the detritus of organic matter coming from plants and animals.

— The lower layers, placed below the vegetable layer, have received in geology the name of rocks, a word which, in this sense, does not always imply the idea of a stony substance, signifying rather a bed or bank made of any mineral substance whatever. Some are formed of sand, of clay or clayey earth, of marl, of rolled pebbles; others are formed of stones properly so called, more or less hard, such as sandstones, marbles, chalk, limestones or calcareous stones, millstones, or coals, asphalts, etc. A rock is said to be more or less powerful according as its thickness is more or less considerable.

By examining the nature of these rocks or layers, it is recognized, by certain signs, that some come from matter melted and sometimes vitrified under the action of fire; others from earthy substances deposited by the waters; some of such substances remained disaggregated, like the sands; others, at first in a pasty state, under the action of certain chemical agents or from other causes, hardened and acquired, with time, the consistency of stone. The banks of superimposed stones denote successive deposits. Fire and water participated, then, in the formation of the materials that compose the solid framework of the terrestrial globe.

— The normal position of the earthy or stony layers, coming from aqueous deposits, is the horizontal. When we see those immense plains, which at times stretch out as far as the eye can reach, of perfect horizontality, smooth as if they had been leveled with a roller, or those deep valleys, as flat as the surface of a lake, we may be certain that, at an epoch more or less remote, such places were for a long time covered with tranquil waters which, on withdrawing, left dry the lands which they had deposited while they remained there. The waters having withdrawn, those lands covered themselves with vegetation. If, instead of rich, slimy, clayey, or marly lands, fit to assimilate the nutritive principles, the waters deposited only siliceous sands, without cohesion, we have the sandy plains which constitute the heaths and the deserts, of which the deposits left by partial inundations and those which form the alluvions at the mouths of rivers can give us a small idea.

— Although the horizontal is the most generalized position and that which aqueous formations normally assume, it is not rare to see, in mountainous countries and over very great extents, hard rocks whose nature indicates that they were formed in an inclined and even sometimes vertical position. Now, since, according to the laws of equilibrium of liquids and of gravity, aqueous deposits can form only on horizontal planes, for those which form on inclined planes are carried away by the currents and by their own weight toward the lowlands, it becomes evident that such deposits were raised up by some force, after they had solidified or been transformed into stone.

From these considerations it can be concluded, with certainty, that all the stony layers which, coming from aqueous deposits, are found in a perfectly horizontal position were formed, during centuries, by tranquil waters, and that, every time they are found in an inclined position, the ground was convulsed and displaced afterward, by general or partial subversions, more or less considerable.

— A characteristic fact of the highest importance, by the irrefutable testimony it offers, consists in the existence, in enormous quantities, of fossil remains of animals and vegetables within the different layers. As these remains are found even in the hardest stones, it must be concluded that the existence of such beings is anterior to the formation of the said stones. Now, if we take into account the prodigious number of centuries that were necessary for their hardening to be produced and for them to reach the state in which they have been from time immemorial, one is forced to the conclusion that the appearance of organic beings on the Earth is lost in the night of the ages and is, consequently, much anterior to the date assigned to them by Genesis. n

— Among the remains of vegetables and animals, there are some which are shown to be penetrated at every point of their substance, without this altering their form, by siliceous or calcareous matter which transformed them into stones, some of which present the hardness of marble. These are petrifactions properly so called. Others were merely enveloped by the matter in a flaccid state; they are found intact and, some of them, whole, in the hardest stones. Others, finally, left only marks, but of perfect clarity and delicacy. In the interior of certain stones, even footprints have been found, and, by the form of the foot, of the toes and of the nails, it has been possible to recognize the animal species to which they belonged.

— Animal fossils contain absolutely nothing, and this is easy to conceive, but the solid and resistant parts, that is, the bony framework, the scales and the horns; they are not rarely complete skeletons; most often, however, they are only detached parts, but whose origin is easily recognized. By examining a jawbone, a tooth, one sees at once whether it belonged to a herbivorous or a carnivorous animal. As all the parts of the animal keep a necessary correlation, the form of the head, of a shoulder blade, of a leg bone, of a foot, suffices to determine the size, the general form, the mode of life of the animal. n Terrestrial animals have an organization which does not allow them to be confused with aquatic animals. Fossil fishes and testaceous mollusks are extremely numerous; the latter alone sometimes form entire banks of great thickness. By their nature, it is verified without difficulty whether they are marine or freshwater animals.

— The rolled pebbles, which in certain places form formidable rocks, constitute an unmistakable indication of their origin. They are rounded like the cobbles of the seashore, a sure sign of the attrition they underwent through the effect of the waters. The regions where they are found buried, in considerable masses, were incontestably occupied by the ocean, or, for a long time, by other moving or violently agitated waters.

— Besides this, the terrains of the various formations are characterized by the very nature of the fossils they enclose. The most ancient contain animal or vegetable species which have entirely disappeared from the surface of the planet. Some more recent species have also disappeared; others, however, analogous to them, have been preserved, differing from them only in size and in a few shades of form. Others, finally, whose last representatives we still see, evidently tend to disappear in a more or less near future, such as the elephants, the rhinoceroses, the hippopotamuses, etc. Thus, in proportion as the terrestrial layers approach our epoch, the animal and vegetable species also approach those which exist today.

The disturbances, the cataclysms which have occurred on the Earth, since its origin, changed its conditions of fitness for the sustenance of life and caused entire generations of living beings to disappear.

— By interrogating the nature of the geological layers, one comes to know, in a more positive manner, whether, at the epoch of their formation, the region where they appear was occupied by the sea, by lakes, or by forests and plains peopled with terrestrial animals. Consequently, if, in one and the same region, there is found a series of superimposed layers, containing alternately marine, terrestrial and freshwater fossils, often repeated, this fact constitutes irrefutable proof that this region was many times invaded by the sea, covered with lakes and laid dry.

And how many centuries of centuries, certainly, how many thousands of centuries, perhaps, were necessary for each period to be completed! What powerful force was necessary to displace and replace the ocean, to raise up mountains! Through how many physical revolutions, violent commotions, did the Earth have to pass, before becoming such as we have seen it since historical times! And to maintain that all this was a work executed in less time than it takes a plant to germinate!

— The study of the geological layers attests, as has already been said, successive formations which changed the aspect of the globe and divide its history into many epochs, which constitute the so-called geological periods, the knowledge of which is essential for the determination of the Genesis.

The principal ones are six in number, designated by the names of primary, transition, secondary, tertiary, diluvian, post-diluvian or present periods.

The terrains formed during each period are also called: primitive, transition, secondary terrains, etc. It is said, then, that such or such layer or rock, such or such fossil, is found in the terrains of such or such period.

— It should be noted that the number of these periods is not absolute, for it depends on the systems of classification. In the six principal ones mentioned above, only those marked by a notable and general change in the state of the planet are comprised; but observation proves that many successive formations took place while each of them lasted. That is why they are divided into six periods characterized by the nature of the terrains, which raise to twenty-six the number of well-marked general formations, without counting those which come from modifications due to purely local causes. PRIMITIVE STATE OF THE GLOBE.

— The flattening of the poles and other conclusive facts are certain indications that the state of the Earth, at its origin, must have been one of fluidity or of flaccidity, a state arising from the matter being either liquefied by the action of fire or diluted by that of water.

It is commonly said, proverbially: there is no smoke without fire. Rigorously true, this maxim constitutes an application of the principle: there is no effect without a cause. For the same reason, it can be said: there is no fire without a hearth. Now, by the facts which take place under our eyes, it is not merely smoke that is produced on the Earth, but a quite real fire, which must have a hearth. This fire coming from the interior of the planet and not from above, the hearth must be in the interior, and, as the fire is permanent, the hearth must be so too.

The heat, whose increase is progressive in proportion as one penetrates into the interior of the Earth and which, at a certain depth, reaches a very high temperature; the thermal springs, the hotter the deeper their source; the fires and the masses of incandescent molten matter which the volcanoes vomit, as through vast vents, or through the fissures which certain earthquakes open, leave no doubt as to the existence of an interior fire.

— Experience demonstrates that the temperature rises by one degree for every 30 meters of depth, whence it follows that, at a depth of 300 meters, the increase is 10 degrees; at 3,000 meters, 100 degrees, the temperature of boiling water; at 30,000 meters, that is, 7 or 8 leagues, 1,000 degrees; at 25 leagues, more than 3,300 degrees, a temperature at which no known matter resists fusion. From there to the center, there is still a space of more than 1,400 leagues, or 2,800 leagues in diameter, a space which would be occupied by molten matter.

Although there is here no more than a conjecture, judging the cause by the effect, it has all the characteristics of probability and leads to the conclusion that the Earth is still an incandescent mass covered with a solid crust of a thickness of 25 leagues at the most, which is only the 120th part of its diameter. Proportionally, it would be much less than the thickness of the thinnest orange peel.

Moreover, the thickness of the terrestrial crust is very variable, for there are zones, especially in volcanic terrains, where the heat and the flexibility of the ground indicate that it is not very considerable. The high temperature of the thermal waters likewise constitutes an indication of the proximity of the central hearth.

— This being so, it becomes evident that the primitive state of fluidity or of flaccidity of the Earth must have had as its cause the action of heat and not that of water. At its origin, then, the Earth was an incandescent mass. By virtue of the radiation of the heat, there occurred what occurs with all matter in fusion: it cooled little by little, the cooling beginning, as was natural, at the surface, which then hardened, while the interior remained fluid. The Earth can thus be compared to a block of coal as it comes igneous out of the furnace and whose surface goes out and cools on contact with the air, its interior keeping in a state of ignition, as will be verified by breaking it.

— At the epoch when the terrestrial globe was an incandescent mass, it contained not a single atom more, nor less, than today; only, under the influence of the high temperature, the greater part of the substances that compose it and that we see in the form of liquids or of solids, of earths, of stones, of metals and of crystals, were in a very different state. They underwent only a transformation. In consequence of the cooling, the elements formed new combinations. The air, enormously dilated, certainly extended to an immense distance; all the water, necessarily transformed into vapor, was mingled with the air; all the matter capable of volatilizing, such as the metals, sulfur, carbon, was in a state of gas. The atmosphere had, therefore, nothing comparable to what it is today; the density of all these vapors gave it an opacity which no ray of the sun could traverse. If at that epoch a living being could have existed on the surface of the planet, it would have been illuminated only by the sinister reverberations of the furnace which was beneath its feet and of the incandescent atmosphere; it would not even have suspected the existence of the Sun. PRIMARY PERIOD.

— The first effect of the cooling was the solidification of the exterior surface of the mass in fusion and the formation there of a resistant crust which, thin at first, gradually thickened. This crust constitutes the stone called granite, of extreme hardness, so named for its granular aspect. In it three principal substances are distinguished: feldspar, quartz or rock crystal, and mica. The latter has a metallic luster, although it is not a metal.

The granitic layer was, then, the first that formed on the globe; it is the one that envelops it completely, constituting in a certain manner its bony framework. It is the direct product of the consolidation of the molten matter. Upon it, and in the cavities presented by its tortured surface, were successively deposited the layers of the other terrains, formed later.

What distinguishes it from these latter is the absence of any stratification whatever; that is to say: it forms a compact and uniform mass throughout its thickness, which is not arranged in layers. The effervescence of the incandescent matter was bound to produce in it numerous and deep fissures, through which that same matter overflowed.

— The following effect of the cooling was the liquefaction of certain matter contained in the air in a state of vapor, which precipitated onto the surface of the ground. There were then rains and lakes of sulfur and of bitumen, veritable streams of iron, copper, lead and other molten metals. Infiltrating through the fissures, this matter constituted the metallic veins and lodes.

Under the influx of these various agents, the granitic surface underwent successive decompositions. There were produced mixtures, which formed the primitive terrains properly so called, distinct from the granitic rock, but in confused masses and without regular stratification.

Then came the waters which, falling upon a burning ground, vaporized anew, fell again in torrential rains, and so on successively, until the temperature permitted them to remain on the ground in a liquid state.

It is the formation of the granitic terrains that gives the beginning of the series of the geological periods, to which it would be fitting to add that of the primitive state of incandescence of the globe.

— Such was the aspect of the first period, a veritable chaos of all the elements confounded together, seeking stabilization, a period in which no living being could exist. For that very reason, one of its distinctive characteristics, in geology, is the absence of any vestige of vegetable or animal life.

It becomes impossible to assign a determined duration to this period, just as to those which followed it. But, given the time required for a ball of a certain volume, heated white-hot, to cool at the surface to the point of permitting a drop of water to remain upon it in a liquid state, it has been calculated that, if that ball were the size of the Earth, more than a million years would be necessary.

TRANSITION PERIOD.

— At the beginning of the transition period, the thickness of the solid granitic crust was still small, which therefore offered very weak resistance to the effervescence of the burning matter which it covered and compressed. There were produced, then, swellings, numerous ruptures, through which the interior lava escaped.

The ground presented inequalities of little consideration.

The waters, shallow, covered almost the whole surface of the globe, with the exception of the raised parts, which, forming low terrains, were frequently flooded.

The air had gradually purged itself of the heavier matter, temporarily in a gaseous state, which, condensing through the effect of the cooling, had precipitated onto the surface of the ground, being then carried away and dissolved by the waters.

When one speaks of cooling at that epoch, this word must be understood in a relative sense, that is, in relation to the primitive state, for the temperature must still have been burning.

The thick aqueous vapors which rose on all sides from the immense liquid surface fell again in copious and hot rains, which darkened the air. Meanwhile, the rays of the Sun began to appear through this misty atmosphere.

One of the last substances of which the air had to purge itself, its natural state being gaseous, was carbonic acid, then one of its components.

— About this epoch, the layers of sediment terrains began to form, deposited by the waters laden with slime and with diverse matter, suited to organic life.

There appear there the first living beings of the vegetable kingdom and of the animal kingdom. Vestiges of them are found, at first in reduced number, but then more and more frequent, in proportion as one passes to the more elevated layers of this formation. It is worthy of note that everywhere life manifests itself as soon as the conditions are propitious to it, each species being born as soon as the conditions proper to its existence are realized.

— The first organic beings which appeared on the Earth were the vegetables of less complicated organization, designated in botany under the names of cryptogams, acotyledons, monocotyledons, that is, lichens, mushrooms, mosses, ferns and herbaceous plants. There are absolutely no trees of woody trunk yet to be seen, but only those of the palm genus, whose spongy stalk is analogous to that of the grasses.

The animals of this period, which appeared after the first vegetables, were exclusively marine: first, polyparies, radiates, zoophytes, animals whose simple and, so to say, rudimentary organization approaches, in the highest degree, that of the vegetables. Later, there appear crustaceans and fishes of species which no longer exist.

— Under the empire of heat and humidity and by virtue of the excess of carbonic acid spread in the air, a gas improper for the respiration of terrestrial animals but necessary to plants, the exposed terrains rapidly covered themselves with an exuberant vegetation, at the same time that the aquatic plants multiplied in the bosom of the swamps. Plants which, in present days, are simple grasses of a few centimeters, attained prodigious height and thickness. Thus there were forests of arborescent ferns of 8 to 10 meters in height and of proportional thickness; lycopodia (horehound, a genus of moss), of the same size; horsetails of 4 to 5 meters, n and whose height does not today exceed one meter, and an infinity of species which no longer exist. Toward the end of the period, there began to appear some trees of the coniferous genus or pines.

— In consequence of the displacement of the waters, the terrains which produced these masses of vegetables were submerged, covered with new earthy sediments, while those which were emerged adorned themselves, in their turn, with similar vegetation. There were thus many generations of vegetables alternately annihilated and renewed. The same did not happen with the animals which, being all aquatic, were not subject to these alternations.

Accumulated during a long series of centuries, these remains formed layers of great thickness. Under the action of heat, of humidity, of the pressure exerted by the later earthy deposits and, no doubt, of various chemical agents, of the gases, of the acids and of the salts produced by the combination of the primitive elements, that vegetable matter underwent a fermentation which converted it into pit-coal or coal. The coal mines are, then, the direct product of the decomposition of the masses of vegetables accumulated during the transition period. That is why they are found in almost all regions. n

— The fossil remains of the exuberant vegetation of that epoch being found today beneath the ice of the polar lands, as well as in the torrid zone, it follows that, since the vegetation was uniform, the temperature must also have been so. The poles, therefore, were not covered with ice, as now. It is that, then, the Earth drew the heat from itself, from the central fire which heated equally the whole solid layer, still not very thick. This heat was far superior to that which could come from the solar rays, weakened, moreover, by the density of the atmosphere. Only later, when the action of the central heat became very weak or null upon the exterior surface of the globe, did that of the Sun come to preponderate, and the polar regions, which received only oblique rays, bearers of a small quantity of heat, covered themselves with ice. It is understood that at the epoch of which we speak, and for a long time afterward, ice was unknown on the Earth. This period must have been very long, to judge by the number and the thickness of the coal layers. n SECONDARY PERIOD.

— With the transition period there disappear the colossal vegetation and the animals which characterized the epoch, either because the atmospheric conditions were no longer the same, or because a series of cataclysms annihilated all that had life on the Earth. It is probable that the two causes contributed to this change, for, on the one hand, the study of the terrains which mark the end of this period proves the occurrence of great subversions arising from upheavals and eruptions which poured upon the ground great quantities of lava, and, on the other hand, because great changes took place in the three kingdoms.

— The secondary period is characterized, under the mineral aspect, by numerous and strong layers which attest a slow formation in the bosom of the waters and mark different well-characterized epochs.

The vegetation is less rapid and less colossal than in the preceding period, no doubt by virtue of the diminution of the heat and the humidity and of modifications which came upon the constitutive elements of the atmosphere. To the herbaceous and pulpy plants are joined those of woody stem and the first trees properly so called.

— The animals are still aquatic, or, at the least, amphibious; vegetable life makes little progress on dry land. There develops in the bosom of the seas a prodigious quantity of shelled animals, owing to the formation of the calcareous matter. New fishes are born, of an organization more perfected than in the preceding period. The first cetaceans appear. The most characteristic animals of that epoch are the monstrous reptiles, among which are noted:

The ichthyosaur, a sort of fish-lizard which reached 10 meters in length and whose jaws, prodigiously elongated, were armed with 180 teeth. Its general form recalls a little that of the crocodile, but without a scaly cuirass. Its eyes had the volume of a man's head; it possessed fins like the whale and, like it, expelled water through openings proper for this.

The plesiosaur, another marine reptile, as large as the ichthyosaur, and whose excessively long neck folded, like that of the swan, and gave it the appearance of an enormous serpent joined to the body of a tortoise. It had the head of the lizard and the teeth of the crocodile. Its skin must have been smooth, like that of the preceding one, for no vestige of scales or of shell was discovered on it. n

The teleosaur, which more closely approaches the present crocodiles, these seeming a diminutive of it. Like the latter, it had a scaly cuirass and lived, at the same time, in the water and on land. Its stature was about 10 meters, of which 3 or 4 were for the head alone. The mouth had an opening of 2 meters.

The megalosaur, a great lizard, a sort of crocodile, of 14 to 15 meters in length. Essentially carnivorous, it nourished itself on reptiles, on small crocodiles and on tortoises. Its formidable jaw was armed with teeth in the form of a pruning-knife blade, double-edged, curved backward, in such a way that, once buried in the prey, it became impossible for the latter to detach itself.

The iguanodon, the largest of the lizards that ever appeared on the Earth. It was from 20 to 25 meters from head to the extremity of the tail, and had upon its snout a bony horn, similar to that of the iguana of the present day, from which it seems it did not differ except in size. The latter is only 1 meter long. The form of the teeth proves that it was herbivorous, and that of the feet that it was a terrestrial animal.

The pterodactyl, a strange animal, the size of a swan, partaking, simultaneously, of the reptile by its body, of the bird by its head, and of the bat by the fleshy membrane which joined together its prodigiously long fingers. This membrane served it as a parachute when it precipitated itself upon its prey from the top of a tree or of a rock. It did not possess a horny beak, like the birds, but the bones of the jaws, of the length of half the body and furnished with teeth, terminated in a point like a beak.

— During this period, which must have been very long, as the number and the exuberance of the geological layers attest, animal life took on enormous development in the bosom of the waters, just as had happened with the vegetation in the period that had ended. More purified and more favorable to respiration, the air began to permit some animals to live on land. The sea displaced itself many times, but without violent shocks. With this period there disappear, in their turn, those races of gigantic aquatic animals, replaced later by analogous species, of less disproportionate forms and of smaller size.

— Pride led man to say that all the animals were created on his account and for the satisfaction of his needs.

But what is the number of those which serve him directly, of those which it has been possible for him to subdue, compared to the incalculable number of those with which he has never had, nor will ever have, any relations whatever? How can such a thesis be sustained, in the face of the innumerable species which exclusively peopled the Earth for thousands and thousands of centuries before he appeared there, and which finally disappeared?

Can it be affirmed that they were created for his benefit? Yet they all had their reason for being, their utility. God, certainly, did not create them from a simple caprice of his will, in order to give himself afterward the pleasure of annihilating them, since they all had life, instincts, the sensation of pain and of well-being.

For what end did he do it? For an end which must have been sovereignly wise, although we do not yet understand it. Certainly, one day it will be given to man to know it, for the confusion of his pride; but, while this does not come to pass, how his ideas are enlarged before the new horizons in which he is now permitted to plunge his gaze, in the presence of the imposing spectacle of this creation, so majestic in its slow march, so admirable in its foresight, so punctual, so precise and so invariable in its results! TERTIARY PERIOD.

— With the tertiary period a new order of things begins for the Earth. The state of its surface changes completely in aspect, the conditions of vitality are profoundly modified and approach the present state. The first times of this period are marked by an interruption of vegetable and animal production; everything reveals traces of an almost general destruction of living beings, after which there appear successively new species, whose organization, more perfect, adapts itself to the nature of the environment where they are called to live.

— During the preceding periods, the solid crust of the globe, by virtue of its small thickness, presented, as has already been said, very weak resistance to the action of the interior fire; easily broken, this envelope permitted the matter in fusion to pour freely over the surface of the ground. This no longer happened when the latter gained a certain thickness. Then, compressed on all sides, the incandescent matter, like water boiling in a closed vessel, ended by producing a kind of explosion. Violently broken at a countless number of points, the granitic mass was riddled with fissures, like a cracked vessel. Along these fissures, the solid crust, raised and depressed, formed the peaks, the chains of mountains and their ramifications. Certain parts of the envelope did not come to be broken; they were only raised up, while, at other points, depressions and excavations were produced. The surface of the ground became then very uneven; the waters which, until that moment, covered it in an almost uniform manner over the greater part of its extent, were driven toward the lower places, leaving dry vast continents, or isolated summits of mountains, forming islands.

Such is the great phenomenon which took place in the tertiary period and which transformed the aspect of the globe. It was not produced instantaneously, nor simultaneously at all points, but successively and at epochs more or less distant from one another.

— One of the first consequences of these upheavals was, as has already been said, the inclination of the layers of sediment, primitively horizontal and so preserved wherever the ground did not undergo subversions. It was, therefore, on the flanks and in the vicinity of the mountains that these inclinations were most pronounced.

— In the regions where the layers of sediment preserved their horizontality, to reach those of primary formation one has to traverse all the others, to a considerable depth, at the end of which one inevitably finds the granitic rock. When, however, they rose up into mountains, those layers were carried above their normal level, going sometimes to a great height, in such a way that, a vertical cut being made in the flank of the mountain, they are shown in all their thickness and superimposed like the courses of a building.

It is thus that at great elevations are found enormous banks of shells, primitively formed at the bottom of the seas. It is today perfectly proved that at no epoch could the sea have reached such heights, seeing that for this all the waters existing on the Earth would not suffice, even were they a hundred times greater in quantity. One would have, then, to suppose that the quantity of water diminished, and then it would be fitting to ask what became of the portion which disappeared. The upheavals, a fact today incontestable, explain in a logical and rigorous manner the marine deposits which are found on certain mountains. n

— In the places where the upheaval of the primitive rock produced a complete tearing of the ground, whether by the rapidity of the phenomenon, or by the form, height and volume of the raised mass, the granite was laid bare, like a tooth which has erupted from the gum. Raised, broken and disarranged, the layers which covered it were left exposed. It is thus that terrains belonging to the most ancient formations and which, in their primitive position, were at a great depth, today compose the soil of certain regions.

— Displaced through the effect of the upheavals, the granitic mass left in some sites fissures through which the interior fire escapes and the matter in fusion flows out; the volcanoes, which are like chimneys of the immense furnace, or, better, safety valves which, giving an outlet to the excess of the igneous matter, preserve the globe from much more terrible commotions. Hence it can be said that the volcanoes in activity are a safety for the whole of the surface of the ground.

Of the intensity of this fire one may form an idea by considering that, in the very bosom of the seas, volcanoes open, and that the mass of water which covers them and penetrates into them does not succeed in extinguishing them.

— The upheavals operated in the solid mass necessarily displaced the waters, these being driven toward the concave parts, which at the same time had become deeper by the elevation of the emerged terrains and by the depression of others. But these terrains rendered low, raised in their turn now at one point, now at another, expelled the waters, which flowed back to other places, and so on, until they had been able to take a more stable bed.

The successive displacements of this liquid mass necessarily worked and tortured the surface of the ground. The waters, flowing off, carried away with them a part of the terrains of previous formations, laid bare by the upheavals, denuded some mountains which they covered and left exposed their granitic or calcareous base. Deep valleys were hollowed out, while others were filled in.

There are, then, mountains directly formed by the central fire: principally the granitic ones; others, due to the action of the waters which, carrying away the movable earths and the soluble matter, hollowed out valleys around a resistant base, calcareous, or of another nature.

The matter carried by the currents of water formed the layers of the tertiary period, which are easily distinguished from those of the preceding ones, less by their composition, which is almost the same, than by their disposition.

The layers of the primary, transition and secondary periods, formed on a little rugged surface, are more or less uniform throughout the Earth; those of the tertiary period, formed, on the contrary, on a very uneven base and by the carrying action of the waters, present a more local character. Everywhere, on making excavations of a certain depth, one finds all the previous layers, in the order in which they were formed, whereas one does not find everywhere the tertiary terrain, nor all its layers.

— During the upheavals of the ground, which occurred at the beginning of this period, organic life, as is easy to conceive, had to remain stationary for some time, which is recognized by examining terrains devoid of fossils. As soon, however, as a calmer state supervened, the vegetables and the animals reappeared. The conditions of vitality being changed, the atmosphere more purified, new species were formed, with a more perfect organization. The plants, from the point of view of structure, differ little from those of today.

— In the course of the two preceding periods, the terrains which the waters did not cover were of little extent; they were, even so, swampy and were frequently submerged. That is the reason why there were only aquatic or amphibious animals. The tertiary period, in which several continents were formed, was characterized by the appearance of terrestrial animals.

Just as the transition period witnessed the birth of a colossal vegetation, the secondary period that of monstrous reptiles, so too the tertiary witnessed that of gigantic mammals, such as the elephant, the rhinoceros, the hippopotamus, the palaeotherium, the megatherium, the dinotherium, the mastodon, etc. These last two, varieties of the elephant, were from 5 to 6 meters in height and their tusks reached 4 meters in length. This period also witnessed the birth of the birds, as well as of the majority of the animal species that still exist today. Some of the species of that epoch survived the later cataclysms; others, generically qualified as antediluvian animals, disappeared completely, or were replaced by analogous species, of less heavy and less massive forms, whose first types were like sketches. Such were the felis spelaea, a carnivorous animal the size of a bull, with the anatomical characters of the tiger and of the lion; the cervus megaceron, a variety of the deer, whose horns, 3 meters long, were spaced 3 to 4 meters apart at the extremities. DILUVIAN PERIOD.

— This period was marked by one of the greatest cataclysms that overturned the globe, whose surface it changed once more in aspect, destroying an immensity of living species, of which only remains are left. Everywhere it left traces which attest its generality. The waters, violently hurled out of their respective beds, invaded the continents, carrying away with them the earths and the rocks, denuding the mountains, uprooting the centuries-old forests. The new deposits which they formed are designated, in Geology, by the name of diluvian terrains.

— One of the most significant vestiges of this great disaster are the boulders called erratic blocks. This denomination is given to rocks of granite which are found isolated on the plains, resting upon tertiary terrains and in the midst of diluvian terrains, sometimes at many hundreds of leagues from the mountains whence they were torn. It is clear that only the violence of the currents could have transported them over such great distances. n

— Another no less characteristic fact, and whose cause has not yet been discovered, is that only in the diluvian terrains are the first aerolites found. Since it was only at that epoch that they began to fall, it follows that previously the cause which produces them did not exist.

— It was also about this epoch that the poles began to cover themselves with ice and that the glaciers of the mountains formed, which indicates a notable change in the temperature of the Earth, a change which must have been sudden, for, had it operated gradually, the animals, like the elephants, which today live only in hot climates and which are found in such great number in the fossil state in the polar lands, would have had to withdraw little by little to the more temperate regions. Everything indicates, on the contrary, that they were probably caught by surprise by a great cold and besieged by the ice. n

— This was, then, the true universal deluge. Opinions are divided as to the causes which must have produced it. Whatever they may be, however, what is certain is that the fact took place.

The most generalized supposition is that the position of the axis and of the poles of the Earth underwent a sudden change; hence a general projection of the waters over the surface. Had the change taken place slowly, the withdrawal of the waters would have been gradual, without shocks, whereas everything indicates a violent and unexpected commotion. Ignorant of what the true cause is, we must remain in the field of hypotheses.

The sudden displacement of the waters may also have occasioned the upheaval of certain parts of the solid crust and the formation of new mountains within the seas, as was verified at the beginning of the tertiary period. But, besides the fact that, in that case, the cataclysm would not have been general, this would not explain the sudden change in the temperature of the poles.

— In the tempest determined by the displacement of the waters, many animals perished; others, in order to escape the inundation, withdrew to the high places, to the caverns and fissures, where they succumbed in masses, either from hunger, or by devouring one another, or, again, perhaps, by the irruption of the waters into the sites where they had taken refuge and whence they could not flee. Thus is explained the great quantity of bones of diverse animals, carnivorous and others, which are found mingled together in certain caverns, which for this reason were called breccias or bone caverns. They are found most often beneath the stalagmites. In some, the bones seem to have been carried there by the current of the waters. n POST-DILUVIAN, OR PRESENT, PERIOD. — BIRTH OF MAN.

— Once the equilibrium was reestablished on the surface of the planet, vegetable and animal life promptly resumed its course. Consolidated, the ground assumed a more stable position; the air, purified, had become suited to more delicate organs. The Sun, shining in all its splendor through a limpid atmosphere, diffused, with the light, a heat less suffocating and more vivifying than that of the internal furnace. The Earth peopled itself with animals less ferocious and more sociable; the vegetables, more succulent, provided a less coarse nourishment; everything, in short, was prepared on the planet for the new guest who would come to inhabit it. There appeared then man, the last being of the Creation, the one whose intelligence would, from then on, contribute to the general progress, himself progressing.

— Did man exist on the Earth only after the diluvian period, or did he appear before that epoch? This is a much-controverted question today, but whose solution, whatever it may be, will change nothing in the body of verified facts, nor make the appearance of the human species other than anterior, by many thousands of years, to the date assigned to it by the biblical Genesis.

What caused it to be supposed that the advent of men occurred subsequently to the deluge was the fact that no authentic vestige of his existence had been found in the preceding period. The bones discovered in various places, and which gave rise to the belief in the existence of a race of antediluvian giants, were recognized as those of elephants.

What is beyond doubt is that man did not exist, neither in the primary period, nor in the transition, nor in the secondary, not only because no trace of him was discovered, but also because there were no conditions of vitality for him. If his appearance took place in the tertiary, it can only have been at the end of the period, and he can then have multiplied but very little.

Moreover, since it was short, the antediluvian period did not determine notable changes in the atmospheric conditions, so much so that the animals were the same, before and after it; it is not, then, impossible that the appearance of man may have preceded that great cataclysm; the existence of the monkey at that epoch is today proved, and recent discoveries seem to confirm that of man.

However that may be, whether man appeared or not before the great universal deluge, what is certain is that his humanitarian role only began to take shape in the post-diluvian period. This period may, therefore, be considered as characterized by his presence.

[1] Fossil, from the Latin fossilia, fossilis, derived from fossa, and from fodere, to dig, to excavate the earth, is a word which in geology is employed to designate bodies or remains of bodies of organic beings which lived prior to the historical epochs. By extension, it is likewise said of the mineral substances which reveal traces of the presence of organized beings, such as the marks left by vegetables or animals.

The term petrified is employed in relation to bodies which have been transformed into stone, by the infiltration of siliceous or calcareous matter into the organic tissues. All petrifactions are necessarily fossils, but not all fossils are petrifactions.

The objects which become coated with a stony layer when immersed in certain waters laden with calcareous substances, such as those of the stream of Saint-Allyre, near Clermont, in Auvergne (France), are not petrifactions properly so called, but simple incrustations.

The monuments, inscriptions and objects produced by human fabrication, these belong to Archaeology.

[2] At the point to which Georges Cuvier brought the paleontological science, a single bone frequently suffices to determine the genus, the species, the form of an animal, its habits, and to reconstruct it entirely.

[3] A plant of the marshes, commonly called horsetail or horse's tail.

[4] Peat formed in the same manner, by the decomposition of heaps of vegetables, in swampy terrains; but with the difference that, being of a much more recent formation and no doubt under other conditions, it did not have time to become carbonized.

[5] In the Bay of Fundy (Nova Scotia), Mr. Lyell found, in a coal layer of a thickness of 400 meters, 68 different levels, presenting evident traces of many forest soils, whose trees still had their trunks furnished with their roots. (L. Figuier)

Allowing no more than a thousand years for the formation of each of these levels, we would already have 68,000 years for that coal layer alone.

[6] The first fossil of this animal was discovered, in England, in 1823. Afterward, others were found in France and in Germany.

[7] Layers of shell-bearing limestone were found in the Andes, America, at 5,000 meters above the level of the ocean.

[8] One of these blocks, evidently coming, by its composition, from the mountains of Norway, serves as a pedestal for the statue of Peter the Great, in Saint Petersburg.

[9] In 1711, the Russian naturalist Pallas found in the ice of the North the entire body of a mammoth covered with its skin and preserving part of its flesh. In 1799, another was discovered, likewise enclosed in an enormous block of ice, at the mouth of the Lena, in Siberia, and which was described by the naturalist Adams. The Yakuts of the surroundings tore its flesh to pieces to feed their dogs. The skin was covered with black hairs and the neck was furnished with a thick mane. The head, without the tusks, which measured more than 4 meters, weighed more than 200 kilograms. Its skeleton is in the museum of Saint Petersburg. On the islands and on the borders of the glacial sea is found so great a quantity of tusks that they are the object of a considerable commerce, under the name of fossil ivory or ivory of Siberia. [10] A great number of similar caverns are known, some of enormous extent. Several exist, in Mexico, of many leagues. That of Aldesberg, in Carniola (Austria), is no less than three leagues. One of the most remarkable is that of Gailenreuth, in Wurtemberg. There are many of them in France, in England, in Germany, in Italy (Sicily) and other countries of Europe.