These catastrophes are with reason admissible, because we observe their analogues, and because we know that they often happen.

He then gives examples of localities along the coast of France, as at Manche, where there are ranges of high hills made up of limestones containing Gryphaeae, ammonites, and other deep-water shells.
In the conclusion of the chapter, after stating that the ocean has repeatedly covered the greater part of the earth, he then claims that "the displacement of the sea, producing a constantly variable inequality in the mass of the terrestrial radii, has necessarily caused the earth's centre of gravity to vary, as also its two poles.[79] Moreover, since it appears that this variation, very irregular as it is, not being subjected to any limits, it is very probable that each point of the surface of the planet we inhabit is really in the case of successively finding itself subjected to different climates." He then exclaims in eloquent, profound, and impassioned language: "How curious it is to see that such suppositions receive their confirmation from the consideration of the state of the earth's surface and of its external crust, from that of the nature of certain fossils found in abundance in the northern regions of the earth, and whose analogues now live in warm climates; finally, in that of the ancient astronomical observations of the Egyptians.
"Oh, how great is the antiquity of the terrestrial globe, and how small are the ideas of those who attribute to the existence of this globe a duration of six thousand and some hundred years since its origin down to our time! "The physico-naturalist and the geologist in this respect see things very differently; for if they have given the matter the slightest consideration--the one, the nature of fossils spread in such great numbers in all the exposed parts of the globe, both in elevated situations and at considerable depths in the earth; the other, the number and disposition of the beds, as also the nature and order of the materials which compose the external crust of this globe studied throughout a great part of its thickness and in the mountain masses--have they not had opportunities to convince themselves that the antiquity of this same globe is so great that it is absolutely beyond the power of man to appreciate it in an adequate way! "Assuredly our chronologies do not extend back very far, and they could only have been made by propping them up by fables.

Traditions, both oral and written, become necessarily lost, and it is in the nature of things that this should be so.
"Even if the invention of printing had been more ancient than it is, what would have resulted at the end of ten thousand years?
Everything changes, everything becomes modified, everything becomes lost or destroyed.

Every living language insensibly changes its idiom; at the end of a thousand years the writings made in any language can only be read with difficulty; after two thousand years none of these writings will be understood.

Besides wars, vandalism, the greediness of tyrants and of those who guide religious opinions, who always rely on the ignorance of the human race and are supported by it, how many are the causes, as proved by history and the sciences, of epochs after epochs of revolutions, which have more or less completely destroyed them.
"How many are the causes by which man loses all trace of that which has existed, and cannot believe nor even conceive of the immense antiquity of the earth he inhabits! "How great will yet seem this antiquity of the terrestrial globe in the eyes of man when he shall form a just idea of the origin of living bodies, as also of the causes of the development and of the gradual process of perfection of the organization of these bodies, and especially when it will be conceived that, time and favorable circumstances having been necessary to give existence to all the living species such as we actually see, he is himself the last result and the actual maximum of this process of perfecting, the limit (_terme_) of which, if it exists, cannot be known." In the fourth chapter of the book there is less to interest the reader, since the author mainly devotes it to a reiteration of the ideas of his earlier works on physics and chemistry.