302 Double Stars. — Occultations. 



obvious ; two others, between the principal pairs, 45" apart, 

 the "debilissima" couple of Sir J. Herschel, though both rated 

 13 mag. are considerably unequal, and form an admirable test 

 for light. With 3^ inches I had pretty certain glimpses of 

 the one and occasional suspicions of the other ; with 5^ both 

 are easily seen. 



Just to the left of Wega we shall observe two small stars 

 almost in a line with it. The nearest of these is — 



48. £ Lyrce. 43""8. 149°*6. 5 and 5|. Topaz and greenish. 

 This is a noble though wide object ; but merely optical. 1850*77 

 and 1855*68, with Scinches, I thought the smaller star 7 and 

 6 mag. It now appears as in Smyth. 



The further of the two is — 



49. B 1 and B 2 Lyrce. Bluish and fine orange, with many 

 companions. This pair is not in the Bedford Catalogue, but 

 forms a very noble object under a low power. 



A little below these two small stars, but somewhat more to 

 the left, we find two more similarly arranged on a parallel line, 

 but brighter, being of 3 mag. We must turn the telescope on 

 the one to the right, which is — 



50. /3 Lyrce, a quadruple group. 45"*8. 60". 71". 150°*1. 

 319°*5. 25°. 3, 8, 8^, and 9. Yery white and splendid, pale 

 grey, faint yellow, and light lilac ; with a minute pair s. The 

 large star is a marvellous object, from its variation of light. 

 This, according to Argelander, takes place in 12d. 21h. 53m. 

 10s., but with two maxima and minima during that period, 

 each maximum reaching the same point between 3 and 4 mag., 

 the minima being unequal, alternately above and below 4 mag. 

 The duration of these singular changes has also been found 

 variable, increasing from the year 1 784, when it was discovered 

 by Goodricke, to 1840, and subsequently slowly decreasing; a 

 wonderful but by no means exceptional instance, which pro- 

 bably indicates the existence of some unknown general law. 

 A question may perhaps be entertained, as to a possible vari- 

 ation in the colour of this curiously mutable star. Smyth, who 

 gives it as above for the epoch 1834*73, states the hue of 7, 

 the 3 mag. star to the left of it, to be "bright yellow" 

 (1834*59). I found with 8f inches 7 always (1849*77, 

 1850*47, 1850*51, 1850*7) much less yellow than & if not 

 white. 1862*77, with 5| inches, I found 7 the paler in tint, 

 though the difference was not considerable. Schmidt thought 

 the colours always nearly the same, yellowish- white, from 1844 

 to 1855. Herschel and South made /3 white. The possibility 

 of a variation in the brightness of 7 also has been mentioned 

 by Smyth; and there seems nothing unlikely in the idea, which 

 at any rate deserves consideration, that change of magnitude 

 may be, in some cases, attended by change of hue. 



