proves that the system of Sirius certainly contains other worlds yet unseen. Our lamented friend Goldschmidt believed he saw three other planets. Thus, in conclusion, we have a solar system, outside of our own, as an object of study.
We know a great number of stars which are accompanied by smaller stars moving around them like the earth around the sun. These systems, which are now numbered by hundreds, have been so carefully observed that we have been able to calculate the orbits and periods of the planets, brilliant or opaque, which compose them.
It is, then, no longer on mere hypothesis that we can speak of solar systems other than our own, but with certainty, since we already know a great number, of every order and of every nature. Single stars should be considered as suns analogous to our own, surrounded by planetary worlds. Double stars, of which the second star is quite small, should be placed in the same class, for this second star may be an opaque planet reflecting only the light of the large one, or a planet still giving out heat and light. Double stars of which the two components give the same brightness are combinations of two suns around each of which may gravitate planets invisible from this distance; these are worlds absolutely different from those of our system, for they are lighted up by two suns, sometimes simultaneous, sometimes successive, of different magnitudes, according to the distances of these planets from each of them; and they have double years of which the winter is warmed by a supplementary sun, and double days of which the nights are illuminated, not only by moons of different colors, but also by a new sun, a sun of night!
Those brilliant points which sparkle in the midnight sky, and which have, during so many ages, remained as mysteries in the imagination of our fathers, are therefore veritable suns, immense and mighty, governing, in the parts of space lighted by their splendor, systems different from that of which we form a part. The sky is no longer a gloomy desert; its ancient solitudes have become regions peopled like those in which the earth is located; obscurity, silence, death, which reigned in these far-off distances, have given place to light, to motion, to life; thousands and millions of suns pour in vast waves into space the energy, the heat, and the diverse undulations, which emanate from their fires. All these movements follow each other, interfere, contend, or harmonize, in the maintenance and incessant development of universal life.