1876.] 
Sidereal Astronomy . 
57 
example, the couple of stars of the northern crown are two 
golden suns, of which the cycle is forty years. In some 
systems the period approaches a century, as in that of 
70 Ophiuchi, which is composed of a clear yellow sun and a 
rose sun, which gravitate round each other in a cycle 
of 92 years. The brilliant couple of 7 Virginis is composed 
of two equal suns, which revolve slowly round themselves, 
and which together turn round their common centre of 
gravity in a period of 175 years. The tertiary system of f 
of Cancer is composed of three suns : the second turns 
round the first in a cycle of fifty-eight years, and the third 
round the two others in six hundred years, describing epi- 
cycloidal curves which I discovered at the beginning of the 
year 1874, and which much perplexed me, as also the astro- 
nomers to whom I communicated them at the time. We 
know, finally, orbital systems, such as those of 7 Leonis , 
€ Lyrce , and of the polar star, of which the cycle surpasses 
a thousand — and even many thousands — of years. Others 
move more slowly still. Thus the double stars are so many 
stellar dials suspended in the heavens, marking, without rest 
in their majestic silence, the inexorable march of time, 
which passes there as here, and showing to the earth, from 
the depths of their unfathomable distances, the years and 
the centuries of other universes 1 Eternal clocks in space ! 
Your movement does not stop ; your finger, like that of 
Destiny, points out for other beings the ever-turning wheel, 
now rising to the height of life, and now plunging into 
the abyss of death ! And we, in our lower sojourn, must read 
on your perpetual movement the sentence of our terrestrial 
lot, which will carry alodg our generation like a grain of 
dust flying over the paths of heaven, whilst you continue to 
turn in silence in the mysterious depths of infinity ! 
IV. The Number of the Double Stars . 
Double stars are not an exception in Nature; their num- 
ber, as compared with that of simple stars, is, on the 
contrary, well worthy of attention ; and I only speak here 
of true multiple stars, not of merely perspective groups. 
To arrive at an approximate knowledge of this comparative 
number, I at first examined separately all the stars of the 
first, second, and third magnitude, and then arranged them 
in the order of their decreasing brightness, and in each case 
I noted its sidereal nature . The result has been that, of the 
300 most brilliant stars of heaven, there are — 
VOL. vi. (n.s.) 
1 
