4 6 
Sidereal Astronomy. 
January, 
even the heart of a philosopher. What part does gravita- 
tion play in these solar systems, so different from ours ? 
What is the numerical importance of these systems in the 
sidereal world ? What is their mode of distribution in the 
universe ? What links have they to simple suns like 
ours ? What is the nature of their light, often so strange 
and so fantastic ? To what respective distances can the 
stars be associated and governed in common by a proper 
movement in space ? What is the condition of the planetary 
systems which can gravitate round these double suns ? 
What can be the physiology of these planets, governed, 
illuminated, heated, alternately and simultaneously, by two 
suns of different masses, of different distances, and different 
lights ? And, finally, what are the wonderful and extra- 
ordinary conditions which can be brought to life on these 
unknown worlds, lost in the depths of the fathomless 
heaven ? Those are the questions which have occupied my 
thoughts, and which I have tried to elucidate successively ; 
such is the subject of a great work which I have ventured 
to attempt, and of which the extent has been much more 
considerable than I had at first supposed. I have been 
able, happily, to have in my hands nearly all the observa- 
tions made on double stars since the commencement ; there 
have been more than a hundred and fifty thousand observa- 
tions, both of angles of position and of angular distances, — 
that is to say, more than three hundred thousand together. 
I have compared them all, and by these comparisons I hope 
to be able to determine the different species of double stars. 
The total number of multiple stars of all kinds discovered 
to this day would reach to 10,487. Of these, a very re- 
markable number already have been proved to form true 
physical systems, possessing certain orbital movement. 
Others remain fixed in the same position. Others are car- 
ried away into space by a common movement, and traverse 
immensity with a bewildering velocity. Others sparkle 
with a changing brightness, and we see their mysterious 
light sometimes diminishing and sometimes augmenting. 
Others even are completely extinguished. My earnest en- 
deavour will be to sum up here in one rapid study, and in a 
form accessible to all clear minds, the whole of the conclu- 
sions to which these researches have conducted me ; to 
explain these phenomena in a picture which will not be 
too unworthy of these wonders ; and to exhibit before the 
eye all the power and the splendour of these far distant 
suns, which govern in the depths of space unknown worlds 
and existences. 
