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.