278 COSMOS. 



Ship, "the glory of the southern skies." Halley, as long 

 ago as 1677, on his return from his voyage to ISt. Helena, 

 expressed strong doubts concerning the alternation of light 

 in the stars of Argo, especially on the shield of the prow and 

 on the deck [danidloKT] and tcardorpcjfm), whose relative cr« 

 ders of magnitude had been given by Ptolemy.^ However, 

 in consequence of the little reliance that can be placed on 

 the positions of the stars as set down by the ancients, of the 

 various readings in the several MSS. of the Almagest, and 

 of the vague estimates of intensity of light, these doubts failed 

 to lead to any result. According to Halley's observation in 

 1G77, ?/ Argus was of the fourth m.agnitude ; and by 1751 

 it was already of the second, as observed by Laeaille. The 

 star must have afterward returned to its fainter light, for 

 BLirchell, during his residence in Southern Africa, from 1811 

 to 1815, found it of the fourth magnitude ; from 1822 to 1826 

 it was of the second, as seen by Fallows and Brisbane ; in 

 February, 1827, Burchell, who happened at that time to be 

 at San Paolo, in Brazil, found it of the first magnitude, per- 

 fectly equal to a Crucis. After a year the star returned to 

 the second magnitude. It was of this magnitude when Bur- 

 chell saw it on the 29th of February, 1828, in the Brazilian 

 town of Goyaz ; and it is thus set down by Johnson and Tay- 

 lor, in their catalogues for the period between 1829 and 1833. 

 Sir John Herschel also, at the Cape of Good Hope, estimated 

 it as being between the second and first magnitude, from 

 1834 to 1837. 



When, on the 16th of December, 1837, this famous astron- 

 omer was preparing to take the photometric measurements 

 of the innumerable telescopic stars, between the eleventh 

 and sixteenth magnitudes, which compose the splendid neb- 

 ula around ?/ Argus, he was astonished to find this star, which 

 had so often before been observed, increase to such intensity 

 of light that it almost equaled the brightness of a Centauri, 

 and exceeded that of all other stars of the first magnitude, 

 except Canopus and Sirius. By the 2d of January, 1838, it 

 had for that time reached the maximum of its brightness. 

 It soon became fainter than Arcturus ; but in the middle of 

 'April, 1838, it still surpassed Aldebaran. Up to March, 

 1843, it continiied to diminish, but was even then a star of 

 the first magnitude ; after that time, and especially in Aprilj 

 1843, it began to increase so much in lij^ht, that, according 



* Delambre, Hist, de VAslron. Ancienna, torn- ii., p. 280, and Hist, dt 

 VAffron. an ISt'we Siecle, p. 11!). 



