11. The great commotions of the Earth have taken place when the crust, by reason of its thinness, offered only a feeble resistance to the effervescence of the incandescent substances in the interior. They diminished in intensity and generality as the crust consolidated. Numerous volcanoes are now extinguished; others have been recovered with rocks of a posterior formation.
There will still be local perturbations, in consequence of volcanic eruptions; also new volcanoes will open with the sudden inundations of certain countries. Some islands will spring out of the sea, and others will be engulfed by it; but the time of the general inundations, like those which have marked great geological periods is past. The Earth, henceforth, will take a position which, without being absolutely unchangeable, place human beings in shelter from general perturbation unless by unknown causes, strange to our globe, something should happen which cannot be foreseen.
12. As to comets, it has been decided that their influence is salutary, rather than hurtful; that they appear destined to refurnish with provisions (if such an expression be allowable) worlds by carrying to them the vital principles which they have accreted during their journey through space in the neighborhood of suns. They would thus be sources of prosperity, rather than messengers of evil.
On account of their gaseous nature, which is now well understood (chap. VI, from item n° 28 on), a violent shock is not to be feared from them; for, in case they should collide with the Earth, the latter would pass through the comet as through a fog.
Their tails are not formidable, as they are formed only by the reflection of the solar light in the immense atmosphere surrounding them, and are constantly directed from the side opposed to the sun, and change their direction according to the sun’s position. This gaseous matter would thus be able, in consequence of the rapidity of the comet’s movement, to form a sort of coma like the foamy track which follow a ship, or the smoke of a locomotive. Besides, many comets have already approached the Earth without causing any damage; and, by reason of their respective density, the Earth will exercise a greater attraction upon the comet than the comet upon the Earth. The remains of an old prejudice can alone inspire fear of their presence. *
* The comet of 1861 has traversed the same route as the earth twenty hours before the latter, without any accident resulting there from.
13. It is necessary to banish from chimerical hypothesis the possibility of the encounter of the Earth with another planet. The regularity and unchangeableness of the laws which preside over the movements of celestial bodies take away all probability of a collision between them.
The Earth, however will have an end; but how? This is something upon which it is impossible to decide; but, as it is far from the perfection to which it will attain, and from the decay which will be a sign of its decline, its present inhabitants may well be assured that it will not be in their time (chap. VI, from item n° 48 on).
14. Physically the Earth has had convulsions from its infancy. It has, however, entered upon a career of relative stability, of peaceable progress, which is accomplished by the regular return of the same physical phenomena, and the intelligent concurrence of man. But it is yet quite in the infancy of its work of moral progress: there will be the cause of its greatest commotions. Until humanity be sufficiently advanced toward perfection by intelligence and the practice of the divine laws, greater perturbations will be caused by man rather than by nature; that is to say, there will occur social and moral, rather than physical changes.