52 THE POPULAR SCIENCE MONTHLY. 



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 com- 

 ponents 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 imagi- 

 nation 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. 



