136 sosmos. 



tions being Algol in Caput Medusae, ]3 Lyrae and e Auriga, 

 which have a pure white light. Mira Ceti, in which a pe- 

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

 dish light ; # but the variability observed in Algol and j3 Lyrse 

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

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

 faintest 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,f 1686, in his Traite 

 des Couleurs. The light of a Lyrse 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. 

 Annng the double stars there are many in 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, Regulus 

 and Fomalhaut. "We find this regular arrangement, of 

 which I have already elsewhere treated, || specially referred 

 to in a late Roman writer, Julius Firmicus Maternus,1T who 

 belonged to the age of Constantine. The differences of 

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

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

 this subject is probably owing to opinions transmitted from 

 the East, which 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, Annuaire pour 1842, p. 348. 



{ Struve, Stellce comp., p. lxxxii. 



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

 and Clusters, No. 3435.") 



II Humboldt, Vues des CordUUres et Monumens des Peuples Indiginea 

 de V Amirique, torn, ii., p. 55. 



IT Julii Firmici Materni Astron., libri viii., Basil, 1551, lib. vi., cap 

 L, p. 150. 



