1876.] 
Sidereal Astronomy. 
77 
or 8881 metres a second, and that these two twin suns 
travel through immensity with a speed of which the 
minimum is 246 millions of leagues a year ! And these are 
the stars which were but yesterday called fixed stars ! 
Calculations made on the other stars have led to equi- 
valent results, showing us these celestial torches as gigantic 
and heavy suns, the enormous distance which separates us 
from them reducing them to simple mathematical points. 
The star nearest to us, a Centauri, has a parallel of o'gi", 
and, in consequence, its distance from the earth is about 8 
trillions 376 millions of leagues. If we adopt 15*5" for the 
average value of the angle comprised between the two com- 
ponents, we find that their distance apart is 2520 millions of 
trilometres, or 630 millions of leagues; that is, less than the 
distance between Uranus and the sun. Its period appears to 
be about 77 years. The result is that it weighs a little less 
than our sun, and that in representing its mass by ten, that 
of the sun should be represented by twelve. But its volume 
ought to be greater (we always speak of the two stars 
united), because its intrinsic light is about three times 
superior to that of our sun. If we were to consider the 
quantity of light as a criterion of the surface of emission, we 
should find that the diameter surpasses that of the sun in 
the proportion of seventeen to ten. 
The period of Cassiopeia, which at first was estimated at 
700 years, then at 181 years, has now been fixed at 176, and 
it is probable that this number is not very far from the 
truth. In admitting the parallax to be o‘i54", which removes 
it from us 55 trillions of leagues, and the semi-major axis to 
be lO'bS", the mass of this system will be ten times that of 
the sun. 
As to the mass of 61 Cygni, which we find described 
in all astronomical works, it is wrong, and, as we have already 
seen, it is impossible to determine, considering that the two 
components do not turn round each other. 
Thus the double stars are truly suns, gigantic and powerful, 
governing in the regions of space illuminated by their 
splendour systems of worlds different from those of which 
we form a part. The sky is no longer a gloomy desert ; its 
antique solitudes have given place to regions peopled like 
that in which the earth gravitates ; the obscurity, the silence, 
the death which reigned in these heights has given place 
to light, to movement, and to life ; the thousands and 
millions of suns pour lavishly into space energy, heat, and 
the diverse undulations which emanate from them as a 
focus ; all these movements succeed each other, cross each 
