174 SPECIAL RESULTS IN THE URANOLOGICAL PORTION 



and even almost equal to Sirius. ( 283 ) It has retained this 

 degree of brightness very nearly to the commencement of the 

 present year. A distinguished observer, Lieutenant Gilliss, 

 who has the command of the Astronomical Expedition which 

 the Government of the United States has sent to the coast of 

 Chili, writes from Santiago in February 1850 : "n Argus with 

 its yellowish red light, which is darker than that of Mars, now 

 comes next to Canopus in brightness, and is brighter than 

 the united light of a Centauri." ( 284 ) Since the ap- 

 pearance of the new star in Ophiuchus in 1604, no 

 fixed star has brightened to such an intensity of light, and 

 for a continuance of now already seven years. In the 173 

 years (from 1677 to 1850) during which we have ac- 

 counts of the magnitude of this fine star, it has under- 

 gone eight or nine oscillations of increase and decrease. 

 It was a fortunate circumstance, and one which has 

 stimulated the persevering attention of astronomers to 

 the phenomenon of a great but unperiodic variability in 

 this star, that it should have manifested itself in the most- 

 striking manner during the memorable five years' expedi- 

 tion of Sir John Herschel to the Cape of Good Hope. 



Similar variations of light which have not yet been re- 

 cognised as periodical have been remarked in several other 

 instances, both in isolated fixed stars and in double stars 

 observed by Struve (Stellarum compos. Mensurse microm. 

 p. Ixxi. Ixxiii.) The examples which it may suffice to 

 cite here are founded on actual photometric estimations 

 and measurements made at different times by the same as- 

 tronomers, and not at all upon the alphabetical series in 

 Bayer's Uranometry. Argelander, in the treatise " de fide 

 Uranometrise Bayerianse," 1842, in p. 15, has shown very 



