378 Double Stars. 



will be found about 1° p 7 Oygni, a little n. I noted it 7 mag. 

 1865, Sept. 22, but subsequently ascertained that, in the 

 Larger Star Maps of the S.D.U.K., there is a 5 mag. star not 

 far from its position, though rather more n. Argelander 

 places a 6 mag. (166 Bode) much nearer my place. Is there 

 room for a suspicion of variable light ? There is also a 7 mag. 

 star, solitary as regards rivals, though with a delicate 11 mag. 

 attendant, pointed at by a line drawn from the 9^ mag. star in 

 the group of e Lyrce, through the southern of these two pairs, 

 which shows a pale but evident carmine hue. It is registered 

 as Bessel (Weisse) xviii. 1169. 



An object of more signification than these is o ' Oygni, the 

 outlying member of the group 0% described as No. 58 of our 

 list (Int. Obs., ii. 304). The second and third stars of this 

 fine combination were each described as ccerulea by Struve, 

 as far back as 1835; with the addition that all the 

 colours were insignes, remarkable. He then expressly states 

 that the blue stars maintained their tint whether the strong 

 yellow lucida was in the field or not, so as to exclude the idea 

 of contrast. In 1838 Smyth gave the same hues, and noted 

 the same proof of independent colour. But in 1850 I entered 

 the colours, with a S^-inch achromatic, deep yellow, white, 

 and blue; and in 1865 I found, with 5^ inches, the 5^ mag. 

 star, " white, or very pale yellow, with a sort of eye of blue, 

 but certainly not at all like 1\" (the closer star) "which! 

 found kept its colour when 4 was put out of the field. I had 

 not at this time identified this as o 1 Oygni, and was quite 

 ignorant of my former observation upon it." June 27, 1867, 

 my 9^ inch "With" mirror showed them as strong orange, 

 fine blue, and very pale yellow, or in Smyth's chromatic nota- 

 tion, O 2 ' 5 , B 3 , Y 4 , " the latter with a cast of blue, a strange 

 but accurate description." The slight yellow tinge associated 

 with reflection from these silver films would account for the 

 deeper hue here ascribed to the great star ; but not for the 

 yellowish cast of the one in question, as fortunately it had been 

 previously noticed with a very fine object-glass. It requires, 

 however, to be noted by the way that those who possess 

 these powerful instruments should look occasionally to the 

 condition of the mirrors, especially the plane, or " flat," in 

 such observations, as a slight degree of tarnish or cloudiness, 

 such as may be expected to form from time to time, and may 

 be readily and safely removed by gentle friction on a suitable 

 rubber, would have a material influence on stellar hues. 

 Were it not for the direct comparison with the unquestioned 

 blue star at so short a distance, this might have been more 

 lightly dismissed as a case of " chromatic personal equation ;" 

 but, under the circumstances, it seems to deserve more attt n- 



