VARIABLE STARS. 24T 



of the new stars in Ophiuchus in 1604, no fixed star ha. 

 attained to such an intensity of light, and for so long a 

 period now nearly seven years. In the 173 years (from 

 1677 to 1850) during which we have reports of the magnitude 

 of this beautiful star in Argo, it has undergone from eight to 

 nine oscillations in the augmentation and diminution of its 

 light. As an incitement to astronomers to continue their 

 observations on the phenomenon of a great but unperiodical 

 variability in rj Argus, it was fortunate that its appearance 

 was coincident with the famous five years' expedition of Sir 

 John Herschel to the Cape. 



In the case of several other stars, both isolated and double, 

 observed by Struve (Stellarum compos. Mensurce Microm., 

 pp. Ixxi.-lxxiii.) similar variations of light have been no- 

 ticed, which have not as yet been ascertained to be periodical. 

 The instances which we shall content ourselves with adducing, 

 are founded on actual photometrical estimations and calcu- 

 lations made by the same astronomer at different times, and 

 not on the alphabetical series of Bayer's Uranonietry. In 

 his treatise De fide Uranometrice Bayerianae, 1842, (p. 15,) 

 Argelander has satisfactorily shown that Bayer did not by 

 any means follow the plan of designating the brightest stars 

 by the first letters of the alphabet ; but that, on the contrary, 

 he arranged the letters by which he designated stars of equal 

 magnitude according to the positions of the stars in a con- 

 stellation, beginning usually at the head, and proceeding, in 

 regular order, down to the feet. The order of letters in 



cloudless purity and transparency of the atmosphere, which 

 last for eight months, at Santiago, in Chili, are so great, that 

 Lieutenant Gilliss, (with the first great telescope ever con- 

 structed in America, having a diameter of 7 inches, con- 

 structed by Henry Fitz of New York, and William Young of 

 Philadelphia), was able clearly to recognize the sixth star in 

 the trapezium of Orion. 



