The star δ of Cepheus is in the same case: it is an orb eclipsed in a period of 129 hours, and its eclipsing planet also revolves in the plane of our vision. The variable star in Ophiuchus has an analogous system, and observation has already revealed a great number of others.
Since, then, a certain number of solar systems differing from our own have been revealed, as it were in section, to terrestrial observation, this affords us sufficient evidence of the existence of an innumerable quantity of solar systems scattered through the immensities of space, and we are no longer reduced to conjecture.
On the other hand, analysis of the motions of several stars, such as Sirius, Procyon, Altaïr, proves that these distant orbs have companions,—planets not yet discovered by the telescope, and that perhaps never will be discovered, because they are obscure, and lost in the radiation of the star.
Some savants have asserted that Life can not germinate if the conditions of the environment differ too much from terrestrial conditions.
This hypothesis is purely gratuitous, and we will now discuss it.
In order to examine what is happening on the Earth, let us mount the ladder of time for a moment, to follow the evolutions of Nature.
There was an epoch when the Earth did not exist. Our planet, the future world of our habitation, slept in the bosom of the solar nebula.
At last it came to birth, this cherished Earth, a gaseous, luminous ball, poor reflection of the King of Orbs, its parent. Millions of years rolled by before the condensation and cooling of this new globe were sufficiently transformed to permit life to manifest itself in its most rudimentary aspects.