THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[THIRD SERIES.] 



DECEMBER 1850. 



LIV. On the alleged evidence for a Physical Connexion be- 

 tween Stars forming Binary or Multiple Groups, deduced 

 from the Doctrine of Chances*. By James D. Forbes, 

 Esq., F.R.S., Corresponding Member of the Institute of 

 France, fyc.f 



]. AN opinion has long obtained amongst astronomers that 

 -^- the great number of cases which occur in the heavens 

 of two or more stars being apparently very close to one 

 another (constituting what have been called double, triple or 

 multiple stars), constitutes of itself an argument for a more 

 than apparent connexion between the members of those 

 groups. 



2. It is evident that two stars may constitute an apparently 

 double star without any real proximity between them, merely 

 because a line passing through the eye^of the spectator and 

 the nearer star ma3 T , if prolonged into space (no matter how 

 far), pass somewhere near a second star, whose position would 

 therefore seem almost to coincide with the first, although the 

 distance which separates them might be indefinitely great. 

 Such stars are sometimes said to be " optically " double. On 

 the other hand, it may happen that the two stars are really 



* This paper was commenced and a great part of it written in the month 

 of May 1850, with the intention of its being read at the meeting of the 

 British Association in August. Circumstances prevented its completion or 

 revision ; and what I had written in Ma}' I read to the Physical Section of 

 that body on the 6th of August. The only addition then made was a sum- 

 mary of conclusions which 1 have inserted verbatim in the present paper, 

 and which form the first four of those given in § 37- Those articles which 

 have been incorporated into this paper from the original draft without any, 

 or only slight verbal alterations, are distinguished by having the current 

 numbers prefixed to them inclosed in brackets, thus [8.]. 



■f Communicated by the Author. 

 Phil. Mag. S. 3, Vol. 37. No. 252. Dec. 1850. 2 D 



