Allan Kardec

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Geological Periods

1. The Earth carries within it the evident traces of its formation. One can follow the phases of it with a mathematical precision in the different rocks which compose its framework. The whole of these studies constitute the science of geology, a science born of this century, and which has thrown light upon the much controversial question of its origin, and of that of the living beings which inhabit it. Here there is no point upon which one can hang a hypothesis. It is the rigorous result of the observation of facts, and into the presence of facts doubt is forbidden to enter. A history of the formation of the globe is written in the geological beds of the Earth in a clearer manner than in books hitherto written, because it is Nature itself who speaks and not the imagination of men that created systems. Where one sees the traces of fire, one can say with certitude that fire has existed; where those of water are seen, one says with no less certainty that water has been there; where one sees those of animals, one infers that animals have lived there.

Geology is therefore a science of observation: it draws conclusions only from that which it sees. Upon doubtful points it affirms nothing. It utters only debatable opinions concerning phenomena, of which the definite solution awaits more complete observations. Without the discoveries of geology, as well as those of astronomy, the genesis of the world would still lie in legendary shadows. Thanks to it, today man knows the history of his habitation; and the trelliswork fables which surrounded his cradle is crushed, never to rise again.

2. Everywhere where stony cavities exist, natural excavations, or apertures opened by man, one observes that which is called stratifications, or superposed beds. The rocks which present this phase are designated stratified rocks. These beds, of a very variable thickness, sometimes of only a few hundred inches, sometimes a hundred yards and more, are distinguished from one another by the color and nature of the substances of which they are composed. Works of art, the boring of wells, the exploding of quarries, and, above all, mines, have given the means of observation to a considerable depth.

3. The beds are generally homogeneous; that is to say, that each one is formed of a similar substance, or of diverse substances which have co-existed, and have formed a compact whole. The line of separation isolating them from one another is always distinctly defined as in the different parts of a ship. No part is seen mingled or lost in another, each remains within its own respective limits. Such is the case, for example, in the colors of the prism or the rainbow.

By these characters, observers decided that they had been successively formed, deposited upon one another by different causes and conditions. The deepest have naturally been formed first, and those nearest the surface subsequently. The last of all, that which is found on the surface, is the bed of vegetable which owes its properties to the destruction of organic matter which produces plants and animals.

4. The lower beds, placed under the vegetable, have received in geology the name of rocks, a word which in this acceptation implies not always the idea of a stony substance, but signifies a resting-place of some mineral substance. Some are formed of sand, of clay or loam, of chalk or pebbles; others of stones, properly speaking, of greater or lesser hardness, such as sand-stone, marbles, chalk, limestone, millstone, coals of the Earth, asphalt, etc. They say that the power of a rock depends upon its thickness.

By the inspection of the nature of these rocks or beds, one recognizes by certain signs, that they are produced by heated substances sometimes vitrified by the action of fire, others, by terrestrial substances deposited by water. Some of these substances have remained disintegrated, as sand; others at first in a pasty state, under the action of certain chemical agents or other causes, have become hardened, and have acquired in time the consistence of stone. Superposed stony beds show successive deposits. Fire and water have then played their parts in the formation of the materials composing the solid framework of the globe.

5. The normal position of terrestrial or stony beds producing aqueous deposits is horizontal. When one sees these immense plains, often extending as far as the eye can see in a perfectly horizontal line, united as if leveled by a roller, or depths of valleys as smooth as the surface of a lake, one can be certain that at some distant epoch these places have been for a long time covered by tranquil waters, which, in retiring, have left the beds dry upon which they were deposited during their sojourn. After the retreats of the waters, these beds have become covered with vegetation. If in place of fertile, muddy clay or chalky ground, which afford nourishment for soil, the waters had deposited only siliceous sand without aggregation, we should find here dry and sandy plains constituting waste lands and deserts. The deposits left by partial inundation and those which form the alluvium at the mouth of rivers, give us a faint idea of this.

6. Although the horizontal is the most normal and usual position of these aqueous formations, one sees, often to a considerable extent in mountainous districts, rocks, which indicate by their nature that they were formed by water in an inclined, and sometimes even in a vertical position. Now, as according to the laws of the equilibrium of liquids and weights, the aqueous deposits can be formed exclusively upon horizontal planes, it is therefore supposed that those which rest on inclined planes are drawn into the lower depths by currents, and by their own weight. It is evident that these deposits have been raised by some force, after their solidification and transformation into stone.

From these considerations we can conclude with certitude that all these stony beds composed of aqueous deposits, in a perfectly horizontal position, have been formed during the succession of ages by tranquil waters; and that, whenever they are found in an inclined position, the Earth has been violently agitated and subsequently broken up by general or partial earthquakes of more or less importance.

7. A characteristic fact of the highest importance for the unexceptional testimony it furnishes, consists in fossil remains of vegetables and animals encountered in innumerable varieties in the different beds; and as those remains are even found in the hardest stones, it is necessary to conclude that the existence of these beings antedates the formation of these stones. Now, if we consider how many centuries must have been spent in this hardening process, which has eventually brought them to the condition in which they have been from time immemorial, one is forced to the conclusion that the time of the advent or organized beings upon the Earth is lost in the night of unknown ages, and that it is consequently very far behind the dates assigned by Genesis. *

* Fossil, from the Latin fossilia and fossilis, derived from fossa, “ditch,” and from fodere, “to dig or plough the earth.” This word is used in geology to signify bodies, or the remains of organized bodies, belonging to creatures that lived in prehistoric times. It is equally applied to mineral substances bearing traces of the presence of organized beings, such as the imprints of vegetables or of animals. The word “fossil,” in a more general acceptation, has been substituted for that of petrifaction, which applies only to bodies transformed into stone by the infiltration of siliceous or calcareous substances in the organic tissues. All the petrifactions are necessarily fossils, but all fossils are not petrifactions. The formation with which stony beds are covered, when they are plunged into waters charged with calcareous substances, such as those of the Saint-Allyre stream, near Clermont, in Auvergne, France, are not properly speaking, petrifactions, but simple incrustations. Monuments, inscriptions and other objects produced by human effort belong to the science of archeology.

8. Among these vegetable and animal fossils are those which have been penetrated throughout by siliceous or calcareous substances, which have transformed them into stone, of which some have the hardness of marble: these, properly speaking, are petrifactions. Others have simply been enveloped by matter in a soft state, and a few of them are found in a perfect state in the hardest stones. Others have left only imprints, but of a distinct perfect delicacy. In the interior of certain stones the imprint of feet have been discovered, also the form of fingers and nails, from which it is concluded that some animal has produced them.

9. The animal fossils are but little comprehended. One finds sometimes the solid and resisting parts, such as bones, scales, and horns. Sometimes these are complete skeleton, but more frequently only detached portions of which it is easy to recognize the production. By the inspection of a jaw or a tooth, one sees immediately whether it belongs to a herbivorous or carnivorous animal. As all the parts of an animal have a necessary correlation, the form of the head, of a shoulder-blade, of a bone of the leg, or a foot, suffices to determine the size, the general form, and the mode of life of the animal. * The terrestrial animals have an organism clearly separating them from aquatic animals. Fish and shell-fish fossils are excessively numerous; shell-fish alone sometimes forming entire beds of great thickness. By their nature, one quickly determines whether they are marine or fresh-water animals.

* At the point to which George Cuvier has carried the science of paleontology, one bone alone suffices often to determine the race, species, and form of an animal, also its habits, by which it can be entirely reconstructed.

10. The masses of pebble-stone rock, which in certain places constitute important rocks, are unequivocal indication of their origin. They are rounded like the pebble-stones on the seashore, an unmistakable sign that they have been subjected to the effects of waters. The countries where they are found buried in large quantities have most certainly once been occupied by violently agitated waters.

11. Rocks of diverse formations are also characterized by the nature of the fossils they enclose. The most ancient ones contain vegetable and animal remains, which have entirely disappeared from the surface of the globe. Certain more recent species have completely disappeared, but have preserved an analogy, which differs only in size and slightly in form. Others, of which we see the last representations, are tending evidently to disappearance in a near future, such as the elephant, rhinoceros, hippopotamus, etc. Thus, as the terrestrial beds approach our epoch, the animal and vegetable species they contain approach those animals and vegetables which still exist.

The perturbations and inundations which have taken place upon the Earth since its origin have completely changed the conditions of vitality, and have made entire generations of living beings disappear.

12. By interrogating the nature of the geological beds, one knows in the most positive manner if, at the epoch of their formation, the country which encloses them was occupied by the sea, by lakes, or by forests and plains peopled with terrestrial animals. If, then, in the same country one finds a series of superposed beds containing alternately marine and fresh-water fossils many times repeated, it is an unexceptionable proof that this same country has been many times encompassed by the sea, covered by lakes, and become dry again.

And how many centuries upon centuries certainly, thousands of centuries perhaps has it required to accomplish each period of this? What a powerful force must have been required to displace and replace the ocean, to raise mountains! How many physical revolutions, violent commotions, the Earth has passed through before becoming what it has been through historic ages! And they try to make us believe that the formation of the Earth took less time than is necessary to propagate a plant!

13. The study of the geological beds attests, as has previously been stated, to successive formations, which have gradually changed the form of the globe, and divided its history into many epochs. These epochs constitute that which is called geologic periods, the knowledge of which is necessary to establish a true Genesis. Geologists count six principal periods, which they have designated as follows: first the primary, second the transition, third the secondary, fourth the tertiary, fifth the deluge, sixth the post-deluge or present period. Rocks formed during the duration of each period are called thus: primitive, transition, secondary rocks, etc. One says that such and such rocks, such and such fossils, are found in rocks of such and such periods.

14. It is essential to remark that the number of these periods is not absolute, and that it depends upon system of classification. One does not comprehend, in the six principal periods designated above, all which are marked by notable and general change in the state of the globe; but observation proves that many successive formations have been produced during the history of each. That is why they are divided into periods, characterized by the nature of the rocks, which bear twenty-six general and very characteristic formations, without counting those which are produced by modifications due to purely local causes.

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