33. With the tertiary period commences for the Earth a new order of things. The aspect of its surface is completely changed; the conditions of vitality are profoundly modified, and approach the present state of the Earth. The first part of this period is signalized by an arrest in animal and vegetable productions. Everything bears traces of an almost entire destruction of living beings, and then appeared successively new species, the better organization of which is adapted to the locality where they are called to live.
34. During preceding periods the solid crust of the globe, by reason of its thinness, presented, as has been said, a pretty feeble resistance to the action of the internal fire. This envelope, easily broken, permitted melted substances to be freely expelled to the surface of the Earth. After having acquired a certain thickness, this did not take place. Burning substances compressed on all sides, like boiling water in a closed vessel, would end in an explosion. The granite mass, violently broken at many points was riddled with crevasses, like a cracked vase. Upon the line of these crevasses the solid crust was raised and reformed, formed peaks, chains of mountains, and their ramifications. Certain parts of the envelope which were not rent where simply piled up, whilst upon other points excavations and depressions were produced.
The surface of the Earth became during the tertiary period very unequal. The waters, which until this time had covered in a nearly uniform manner the greater part of its extent, flowed down into the lowest places, leaving vast continents of dry land, or summits of isolated mountains, which formed islands.
Such is the great phenomenon which has been accomplished in the tertiary period, and which has transformed the aspect of the globe. It was not produced instantaneously or simultaneously at all points, but successively at epochs more or less remote from one another.
35. One of the first consequences of these uprisings has been, as has been said, the inclination of the primitively horizontal beds of sediment, and which have remained everywhere in this horizontal position where the soil has not been overthrown. It is in the flanks and in the vicinities of the mountains that these inclinations are steeper.
36. In countries where the beds of sediment have preserved their horizontal position, in order to reach that of the first formation, it is necessary to pass through all the others, often to a great depth, at the end of which one invariably finds the granite rock. But, when these beds have been elevated into mountains, they have been carried above their normal level, sometimes to a very great height, in such a way that, if one makes a vertical trench upon the side of the mountain, they are shown in all their thickness, superposed like the different layers of a building.
This explains why quite large beds of marine shell fossils are often found on high elevations of land. It has been generally recognized that at no epoch the sea has been able to attain such a height; for all the water on the Earth is not sufficient for it, and would not be even were it a hundred times greater in volume. Some might say that the quantity of water had diminished; but then the query would come. What had become of it? The uprisings which are now incontestably demonstrated by science explain completely and logically the marine deposits which are found upon certain mountains. *
* Beds of marine shell fossils were found five thousand meters above the sea level, in the Andes of South America.
37. In places where the uprising of the primitive rock has produced a complete rent in the soil, perhaps by its rapidity, perhaps by form, height, or volume of the raised mass, the granite has appeared bare like a tooth which pierces the gums; the beds which were covered, elevated, upheaved, and recovered have been brought to life; whilst rocks belonging to the most ancient formations, and which were found in their primitive position at a great depth, form now the soil of certain countries.
38. The granite mass, dislodged by the effect of the earthquakes, has left in some places fissures through which the melted substances have escaped: the volcanoes. The volcanoes are like chimneys to this immense furnace, or better still, like escape-valves, which, in providing an exit for the great excess of burning substances, preserve them from terrible commotions, whence one can infer that a large number of active volcanoes is a source of safety to the whole Earth.
One can form an idea of the intensity of this fire by learning how volcanoes opened in the midst of an ocean are not extinguished by the immense waters which cover and penetrate them.
39. The uprisings of the Earth in one solid mass have necessarily displaced the waters which have flowed back into hollow places, become deeper by the uprising of emerged rocks and by depressions; but these same low depths have been raised in their turn sometimes in one place, sometimes in another, and have repelled the waters, which have flowed elsewhere successively until they have found a stable resting place.
The successive displacements of this liquid mass have violently agitated the surface of the Earth. The waters, in passing away, have drawn portions of rocks of anterior formation, brought to light by the earthquakes; denuded mountains which were recovered, and brought to light their granite or calcareous base. Deep valleys have been hollowed out, and others filled in.
There are, then, mountains formed directly by the action of the central fire: they are principally granite mountains. Others are due to the action of the waters, which, in drawing mellow Earth and soluble matters after them, have hollowed out valleys around a calcareous or other resisting base.
The substances drawn by running waters have formed the beds of the tertiary period, which are easily distinguished from the preceding ones less by their composition, which is nearly the same, than by their disposition.
The beds of the primary, transition, and secondary periods, formed upon a slightly undulating surface, are nearly uniform over all the Earth. Those of the tertiary period, to the contrary, formed upon a very unequal base and by the procession of the waters, have a more local character. Everywhere, by digging to a certain depth, one finds all the anterior beds in the order of their formation; whilst the tertiary rocks are not found everywhere, nor all the beds of the latter.
40. During the earthquakes which took place at the commencement of this period, one finds that organic life has been arrested, which is proved by the absence of fossils in these rocks. But, as soon as a calmer state was restored, vegetables and animal re-appeared. The conditions of vitality being changed, the atmosphere becoming purer, new species, with more perfect organization, were formed. As regards structure, the plants differed very little from those of our time.
41. During the two preceding periods the Earth uncovered by water was of very small extent, marshy and frequently submerged: that is why the animals were all either aquatic or amphibious. The tertiary period, in which vast continents have been formed, has been characterized by the appearance of terrestrial animals.
Just as the transition period has brought forth colossal vegetables, and the secondary period monstrous reptiles; the tertiary period has produced gigantic mammal animals, such as the elephant, rhinoceros, hippopotamus, paleotherium, megatherium, dinotherium, the mastodon, mammoth, etc. The two latter elephant varieties were 5 to 6 meters tall, and their tusks would reach 4 meters long. It has produced birds as well, some of the species of which are living now. A few of the animals of this period have survived subsequent inundations. Others that have been designated by the generic term, “pre-diluvium animals,” have completely disappeared, or have been replaced by analogous species, in form lighter and smaller in which the original types have been merely outlined: such are the felisspeloea, a carnivorous animal about the size of the bull, having the anatomical characteristics of tiger and lion; the cervus megaceron, a variety of deer of which the horns, three yards in length were separated by three to four yards from their extremities.