NATURAL SCIENCES OF PHILADELPHIA. 55 



Both wbite. Struve, 1830. 



Yellow and blue. Sestini, 1844. 



Full white and very pale wbite. Smylh, 1850. 



White or ft little yellowish, and tawny or lilac. Webb, 1850. 



Pale reddish white and lilac. Smyth, 1855. 



White and pale olive blue. Dembowski, 1356. 



Same as in 1850, but with very little contrast. Webb, 1862. 



Flushed white and pale lilac. Webb, 1862. 



54. Sigma Corona?, 6 : 6. Creamy wbite and smalt blue. Webb, 1862. 



The 6.} has had many changes, as follows ; certainly not blue and 

 differing very little from the other. South, 1825. 



While. Struve, 1S36. 



A yellow ashy and doubtful blue. Dembowski, 1854 57. 



Sometimes blue, sometimes yellow. Secchi, 1855 57. 



" At one time ruddy, at another time bluish, apparently changing 

 white being looked at ; a versatility of hue which I have re- 

 marked in other stars similarly circumstanced." Webb, 1850 5. 



55. Mu Cygni, 5 : 6. White and pale blue. Struve, 1831. 



Yellow and more yellow. Sestini, 1844. 

 Reddish yellow and olive. Dembowski, 1853 4. 

 Clear light yellow and ashy yellow. Dembowski, 1S55. 

 " The 5 yellow, while the 6 showed the curious effect of an unde- 

 cided and changeable hue blue and tawny." Webb, 1850 1. 

 The 5 yellow. Webb, 1862. 

 "Secchi's colors are here uncertain and variable." 



56. Alpha Piscium, 5 : 6. Greenish and pale blue. " There seems to be 



something peculiar in the color of the smaller star, as to which 

 observers are strongly at variance with each other, and even 

 with themselves. Some see no contrast, some agree with Smyth, 

 some find it tawny and ruddy. The details are curious but too 

 long for insertion here. Other small stars show a similar uncer- 

 tainty-" Webb. 

 The frequent changes in some of these stars, the last three or four of this 

 Catalogue especially, are remarkable, and seem inexplicable to astronomers. I 

 presume the difficulty arises, not as is supposed from the atmosphere, or from the 

 instruments, or from personal peculiarities, but chiefly from the frequency of the 

 real changes in the stars. If, for instance, it be complained that " Secchi's 

 colors are uncertain and variable," it is because in such instances the colors 

 of the stars are uncertain aud variable. 



An addition has been made to the title of this Catalogue to obviate the ob- 

 jection that possibly some of the apparent changes of color of the stars may 

 be merely the errors of observation, or the effects of the atmosphere, and not 

 real changes in the celestial bodies. Nevertheless, an apparent change is a- 

 fact in the constitution of the world, and deserves a notice and an explana- 

 tion. From whatever causes these changes may arise, there is needed a faithful 

 collection of all the facts in this department of astronomy. They are scattered 

 about in many volumes and many various scientific depositories, and no one, 

 as far as I am aware, has brought them together or made them a special study. 

 But in making such a collection, or catalogue, no changes should be omitted. 

 Whether we regard them as apparent or real, whether they be small or great, 

 whether they may have been slow or sudden, none should be suppressed by 

 the compiler in his catalogue. To admit some and reject others because in 

 his opinion some are right and others are wrong, would be making his work a 

 confused medley of facts and opinions unworthy of reliance. If, as appears 

 undeniable, there be changes in the colors of the stars, then, from the nature 

 of things, there may be small changes as well as great ones. To reject a re- 



1864.] 



