133 SOSMOS. 



tions being Algol in Caput Medusre, (3 Lyrce and e Auriga, 

 which have a. pui'e white light. Mira Ceti, in which a pe« 

 liodical change of light was first recognized, has a strong red 

 dish light ;^ but the variability observed in Algol and [i Lyrce 

 proves that this red color is not a necessary condition of a 

 c.liange of light, since many red stars are not variable. The 

 Ikintest stars in which colors can be distinguished belong, ac- 

 cording to Struve, to the ninth and tenth magnitudes. Blue 

 stars were first mentioned by Mariotte,t 1686, in his 2'railS 

 des Couleurs. The light of a L}Ta3 is bluish ; and a smaller 

 stellar mass of 3^ minutes in diameter in the southern hem- 

 isphere consists, according to Dunlop, of blue stars alone. 

 Am:)ng the double stars there are many m which the princi- 

 pal star is white, and the companion blue ; and some in which 

 both stars have a blue light| (as 6 Serp. and 59 Androm.). 

 Occasionally, as in the stellar swarm near k of the Southern 

 Cross, which was mistaken by Lacaille for a nebulous spot, 

 more than a hundred variously-colored red, green, blue, and 

 bluish-green stars are so closely thronged together that they 

 appear in a powerful telescope " like a superb piece of fancy 

 jewelry."^ 



The ancients believed they could recognize a remarkable 

 symmetry in the arrangement of certain stars of the first 

 magnitude. Thus their attention was especially directed to 

 the four so-called regal stars, which are situated at oppo- 

 site points of the sphere, Aldebaran and Antares, E-egulus 

 and Fomalhaut. We find this regular arranfjement, of 

 which I have already elsewhere treated, || specially referred 

 to in a late Roman writer, Julius Firmicus Maternus,^ who 

 belonged to the age of Constantine. The diflerences of 

 right ascension in these regal stars, stcllce regales, are llh. 

 57m. and 12h. 49m. The importance formerly attached to 

 this subject is probably owing to opinions transmitted from 

 the East, w^hich gained a footing in the Roman empire un- 

 der the Caesars, together with a strong national predilection, 

 for astrology. The leg, or north star of the Great Bear (the 

 celebrated star of the Bull's leg in the astronomical repre- 



* Cosmos, vol. ii., p. 330. t Arago, Anmtalre pour 1842, p. 318 



I Stnive, StellcB comp., p. Lxxxii. 



§ Sir John Herschel, Observations at the Cape, p. 17, 102. (" Nebula 

 and Clusters, No. 3435.") 



II HumbokU, Viies des Cordillircs el Afnnumcns des Peiipies Indigenet 

 7/e V Arn4riqve, torn, ii., p. 5.5. 



11 JuJii Firmici Materni Astrcn.,X\\)v\ viii.. Basil, 1551, lib vi., cap 

 ;., p- 150. 



