176 COSMOS. 



again to its minimum during eight hours of tlie latter period, however, 

 it scarcely changes at all, and very inconsiderably for a whole day. 



(9) a Herculis, R. A. 256^ 57', Decl. -j-14° 34'; an extremely red 

 double star, the variation of whose light is in every respect very iiTeg- 

 ular. Frequently, its light scarcely changes for months together; at 

 other times, in the maximum, it is nearly five gradations brighter than 

 in the minimum ; consequently, the period also is still vejy uncertain. 

 Tho discoverer of the star's variation had assumed it to be sixty -three 

 days. I at first set it down at ninety-five, until a careful reduction of all 

 iny observations, made during seven years, at length gave me the peri- 

 od assigned in the text. Heis believes that he can rej)resent all the ob- 

 servations by assuming a period of 184-9 days, with two maxima and 

 two minima. 



(10) Coronae R., R. A, 235° 36', Decl. -}-28° 37'. This star is varia- 

 ble oidy at times ; the period set down has been calculated by Koch 

 from his ov,-n observations, which unfortunately have been lost. 



(11) Scuti R., R. A. 279° 52', Decl. —5° 51'. The variations of bright- 

 ness of this star are at times confined within a very few gradations, 

 whereas at others it diminishes from the fifth to the ninth magnitude. It 

 has been too little observed to determine when any fixed rule prevails 

 in these deviations. The duration of the period is also subject to con- 

 siderable fluctuations. 



_ (12) Virginis R., R. A. 187° 43', Decl. -}-7° A9'. It maintains its pe- 

 riod and its maximum brightness with tolerable regularity; some devi- 

 ations, however, do occur, w^hich appear to me too considerable to be 

 ascribed merely to errors of observation. 



(13) Aquarii R., R. A. 354° 11', Decl. — 16° 6'. 



(14) Serpentis R., R. A. 235° -57', Decl. -|-150 36'. 



(15) Seipentis S.. R. A. 228^ 40', Decl. -fl40 52'. 



(16) Cancri R., R. A. 122^ G', Decl. 4-12° 9'. 



Of these four stars, which have been but very sligljtly observed, little 

 more can be said than what is given in the table. 



(17) a Cassiopeiii:', R. A. 8^ 0'^ Decl. -f550 43'. This star is very diffi- 

 cult to obsei've. The diiFerence between its maximum and minimum 

 only amounts to a {e\\ gradations, and is, moreover, as variable as the 

 duration of the period. This circumstance explains the varying state- 

 ments on this head. That which I have given, which satisfactorily rep- 

 resents the obsei-vations from 1782 to 1849, appears to me the most prob- 

 able one. 



(18) a Orionis, R. A. 86° 46', Decl. -f7° 22'. The variation in the 

 light of this star likewise amounts to only four gradations from the min- 

 imum to the maximum. For 91^ days it increases in brightness, while 

 its diminution extends over 104^, and is imperceptible from the twen- 

 tieth to the seventieth day after the maximum. Occasionally its varia 

 bility is scarcely noticeable. It is a vers' red star. 



( 19) a Hydra?, R. A. 140° 3', Decl. —3° 1'. Of all the variable stars, 

 this is the most difficult to observe, and its period is still altogether un- 

 certain. Sir John Herschel sets it down at fi-om twenty-nine to thirty 

 days. 



(20) £ Aurigiie, R. A. 72° 48', Decl. +43° 36'. The alteraation of 

 light m this star is either extremely irregular, or else, in a period of sev- 

 eral years, there are several maxima and minima — a question which can 

 not be decided for many vears. 



(21) C Geminorum, R. A. 103° 48', Decl. -f20° 47'. This star has 

 hitherto exhibited a perfectly regular course in the variations of its iigJ^t" 



