392 VARIABLE STARS. SECT. XXXVI. 



when it is past its maximum lustre it assumes a yellow tint, and 

 while on its decrease it becomes ruddy with flashes of bright 

 red light. These changes are very marked in a small star near 

 the star 77, at the extremity of the south wing of Virgo. 



Sir John Herschel, after having described the glory of the 

 starry heavens, asks, " For what purpose are we to suppose such 

 magnificent bodies scattered through the abyss of space ? Surely 

 not to illuminate our nights, which an additional moon of the 

 thousandth part the size of our own would do much better, nor 

 to sparkle as a pageant void of meaning and reality, and bewilder 

 us with vain conjectures. Useful, it is true, they are to man 

 as points of exact and permanent reference ; but he must have 

 studied astronomy to little purpose who can suppose man to be 

 the only object of his Creator's eare, or who does not see in the 

 vast and wonderful apparatus around us provision for other races 

 of animated beings. The planets, we have seen, derive their 

 light from the sun, but that cannot be the case with the stars. 

 These doubtless then are themselves suns, and may perhaps, 

 each in its sphere, be the presiding centre round which other 

 planets or bodies, of which we can form no conception from any 

 analogy offered by our own system, may be circulating." 



Another circumstance shows how probable it is that dark 

 bodies are revolving among the stars. The proper motion of 

 Sirius is very irregular sometimes it is rapid, and at other times 

 slow ; the cause is ascribed by MM. Bessel and Peters to a dark 

 companion which revolves with Sirius about their common centre 

 of gravity, and by its attraction disturbs the equable motion of 

 the star. 



Sometimes stars have all at once appeared, shone with a bright 

 light, and vanished. Several instances of these temporary stars 

 are on record. A remarkable one occurred in the year 125, 

 which is said to have induced Hipparchus to form the first cata- 

 logue of stars. Another star appeared suddenly near a Aquilse 

 in the year 389, which vanished after remaining for three weeks 

 as bright as Venus. On the 10th of October, 1604, a brilliant 

 star burst forth in the constellation of Serpentarius, which con- 

 tinued visible for a year ; and on the llth of November, 1572, a 

 star all at once shone forth in Cassiopeia, which rapidly in- 

 creased in brightness till it surpassed that of Jupiter so much as 

 to be visible at midday. It began to decrease in December of 



