VARIABLE STARS. 23" 



visible for a short lime during every year, all that c^.n be said 

 is, that both its period and its maximum brightness are sub- 

 ject to very great irregularities. 



(5) Leonis R, = 420 Mayeri ; 11. A. 144 52', Decl. 

 -{-12 7'. This star is often confounded with 18 and 19 



Leonis. which are close to it; and in consequence has been 

 very little observed ; sufficiently, however, to show that the 

 period is somewhat irregular. Its brightness at the maximum 

 seems also to fluctuate through some gradations. 



(6) ii Aquilae. called also u Antiuoi ; R. A. 296 12', Decl. 

 + 37'. The' period of this star is tolerably uniform, 

 7d. 4h. 13m. 53s.; observations, however, prove that at 

 long intervals of time trifling fluctuations occur in it, not 

 amounting to more than 20 seconds. The variation of light 

 proceeds so regularly, that up to the present time no devia- 

 tions have been discovered which could not be accounted 

 for by errors of observation. In its minimum, this star is 

 one gradation fainter than Aquila3 ; at first it increases 

 slowly, then more rapidly, and afterwards again more slowly; 

 and in 2d. 9h. from its minimum, attains to its greatest 

 brightness, in which it is nearly three gradations brighter 

 than ]8, but two fainter than J Aquilre. From the maximum 

 its brightness does not diminish quite so regularly; for when 

 the star has reached the brightness of /3 (i. e. in Id. lOh. after 

 the maximum), it changes more slowly than either before or 

 afterwards. 



(7) j8 Lyra, R. A. 281 8', Decl. + 33 11'; a star 

 remarkable from the fact of its having two maxima and two 

 minima. When it has been at its faintest light, one-third 

 of a gradation fainter than Lyrae. it rises in 3d. 5h. to its first 

 maximum, in which it remains three-fourths of a gradation 

 fainter than y Lyra?. It then sinks in 3d. 3h. to its second 

 minimum, in which its light is about five gradations greater 

 'than that of f. After 3d. 2h. more, it again reaches, in its 

 second maximum, to the brightness of the first ; and afterwards, 

 in 3d. 12h., declines once more to its greatest faintness; so 

 that, in 12d. 21h. 46m. 40s. it runs through all its variations 

 of light. This duration of the period, however, only applies 

 to the years 1840 to 1844; previously it had been shorter-- 

 in the year 1784, by about 2|h. ; in 1817 and 1818, by more 

 than an hour ; and, at present, a shortening of it is again 

 clearly perceptible. There is therefore no doubt that in tiie 



