304 MR. ALFRED BROTHERs's 



XIII. Catalogue of Binary Stars, with Introductory Re- 

 marks. By Alfred Brothers^ F.R.A.S. 



Read October i4tli, 1866. 



From the time of the publication of the first catalogue of 

 double stars by Sir William Herschel in 1782, the search 

 for such objects has been one of unabated interest to, both 

 professional and amateur astronomers ; and the result has 

 been the compilation of many other valuable catalogues. 



The number of double and triple stars discovered by Sir 

 William Herschel and other observers down to the present 

 time amounts to many thousands ; but of these, compara- 

 tively few have been proved to be binary systems, as distin- 

 guished from stars optically double. That such physical 

 connexion might exist was suggested by Michell in 1767 ; 

 but the honour of establishing the fact was reserved for 

 Sir William Herschel, who appears not only to have ascer- 

 tained the truth of the supposition beyond doubt, but also 

 to have invented the instrument by which some of his 

 measures were taken^. These early measures of Herschel, 

 and those of Struve, Sir J. Herschel, Argelander, Smyth, 

 Dawes, Secchi and others, form the foundation an which 

 all the subsequent observations are based. They are con- 

 tained, however, in works not generally accessible to the 

 observer ; and I have no doubt that there are many ama- 

 teurs who, like myself, have felt the inconvenience of 

 having to refer to several sources for information relative 

 to the positions and distances of the binary stars, and who 

 would be glad to possess a more complete list than is 

 usually found in elementary works on astronomy. I have 

 therefore been induced to extend the plan of a catalogue 



* Phil. Trans, vol. Ixxi. p, 500. 



