? 



VARIABLE STARS. 241 



remarkable of this class of celestial phenomena the sudden, 

 appearance of Tycho Brahe's star so, influenced by similar 

 considerations, we shall begin our statements concerning the 

 variable stars whose periods have not yet been ascertained, 

 with the unperiodical fluctuations in the light of Argus, which 

 to the present day are still observable. This star is situated 

 the great and magnificent constellation of the hip, " the 

 glory of the southern skies." Halley, as long ago as 1677, on 

 his return from his voyage to St. 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 (do-TnSiW); 

 and Karao-rpco/xa), whose relative orders of magnitude had been 

 given by Ptolemy. 16 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 inten- 

 sity of light, these doubts failed to lead to any result. Accord- 

 ing to Halley's observation in 1677, 9 Argus was of the 4th 

 magnitude; and by 1751, it was already of the 2nd, as ob- 

 served by Lacaille. The star must have afterwards returned 

 to its fainter light, for Burchell, during his residence in 

 Southern Africa, from 1811 to 1815, found it of the 4th 

 magnitude; from 1822 to 1826, it was of the 2nd, 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 1st magnitude, perfectly equal to a, Crucis. After 

 a year, the star returned to the 2nd magnitude. It was of 

 this magnitude when Burchell saw it on the 29th of Febru- 

 ary, 1828, in the Brazilian town of Goyaz; and it is thus 

 set down by Johnson and Taylor, in their catalogues for the 

 period between 1829 and 1833. Sir John Herschel also, at 



6 Delambre, Hist, de I" Astron. 'ancienne, torn. ii. p. 280, 

 and Hist, de V Astron. au ISieme Siecle, p. 119. 



VOL. III. R 



