448 



NOTICE OF THE ORBIT OF THE 



the last or the beginning of the present century ; and that about twenty years 

 hence the stars will probably be seen very near each other, or in apparent con- 

 tact, but the data are at present insufficient to give even an approximation to the 

 major axis of the orbit and time of revolution." 



The next authority on the subject is Sir John Herschel, who specially applied 

 himself to the subject of the Southern double stars when at the Cape, and had 

 far superior instruments for such a purpose to any of his predecessors ; he thus 

 describes and sums up all that was known to him of this star, in his recently 

 published work. 



" This superb double star, beyond all comparison the most striking object of 

 the kind in the heavens, and to which the discovery of its parallax by tlie late 

 Professor Henderson has given a degree of astronomical importance no less con- 

 spicuous, — consists of two individuals, both of a high ruddy or orange colour, 

 though that of the smaller is of a somewhat more sombre and brownish cast. 

 They constitute together a star wliich to the naked eye is equal or somewhat 

 superior to Arcturus in lustre." After describing the magnitude which he con- 

 sidered should be assigned to each, and which agrees more nearly with what I 

 have already stated as being my own opinion, and after giving some optical and 

 physiological reasons which may tend to explain the imder-estimation of former 

 obsei-vers, — Sir John then cites the fact of the remarkable amount of proper mo- 

 tion of the stars, and says, " This consideration alone suffices to decide us in ad- 

 mitting a binary connection between them, and it will therefore be interesting to 

 see what evidence observation furnishes of orbitual motion round their centre of 

 gravity. For this, however, the data are somewhat precarious, as we have, until 

 recently, only catalogued differences of A.R. and Polar distances, from which to 

 calculate the angle of position and distance at the epochs of observation. This 

 done, and the results tabulated, together with my own positions and distances, 

 obtained by direct measurement with the equatorial, we have as follows :" — 



I 



