VARIABLE STARS. 245 - 



set down as of the same magnitude with ft and y, is by 

 more than a magnitude fainter than these ; i is decidedly 

 variable. Although in general this star is brighter, I have 

 nevertheless in three years observed it on five occasions 

 to be undoubtedly fainter than a. I also consider ft Ursse 

 majoris to be variable, though I am unable to give any fixed 

 periods. In the years 1840 and 1841, Sir John Herschel 

 found ft TJrsse minoris much brighter than the Polar star; 

 whereas still earlier, in May, 1846, the contrary was ob- 

 served by him. He also conjectures ft to be variable. 20 

 Since 1843, I have, as a rule, found Polaris fainter than ft 

 Ursa? minoris; but from October, 1843, to July, 1849, Polaris 

 was, according to my registers, 14 times brighter than ft. 

 I have had frequent opportunities of convincing myself that 

 the colour of the last-named star is not always equally red ; 

 it is at times more or less yellow, at others most decidedly 

 red." 21 All the pains and labour spent in determining the 

 relative brightness of the stars will never attain any certain 

 result until the arrangement of their magnitudes from mere 

 estimation shall have given place to methods of measurement 

 founded on the progress of modern optical science. 22 The 

 possibility of attaining such an object need not be despaired 

 of by astronomers and physicists. 



The probably great physical similarity in the process of 



20 Observations at the Gape, 259, note 260. 

 1 Heis. in his Manuscript Notices of May, 1850 ; also 

 Observations at the Cape, p. 325; and P. von Boguslawski, 

 Uranus for 1848, p. 186. The asserted variation of *. a, and ^ 

 Ursee maj. is also confirmed in Outlines, p. 559. See Madler, 

 Astr., p. 432. On the succession of the stars which, from 

 their proximity, will in time mark the north pole, until, after 

 the lapse of 12000 years, Vega, the brightest of all possible 

 polar stars, will take their place. 



53 Cosmos, vide supra, p. 128. 



