182 SPECIAL RESULTS IN THE URANOLOGICAL PORTION 



motion, are, Arcturus (1st magnitude) which has an annual 

 proper motion of 2"'25 ; a Centauri (1st m.), 3' x '58 ( 29 ) ; 

 ju Cassiopeiee (6th m.), 3"'74; the double star Sin Eridanus 

 (5-4 m.) 4"-08; the double star 61 Cygni (5'6 m.), 5"-123, 

 the motion being recognised by Bessel in 1812 by compa- 

 rison with Bradley' s observations ; a star on the borders of 

 the constellations Cam's Yenaticus ( 296 ) and Ursus Major, No. 

 1830 of Groombridge's catalogue of circum polar stars (7th 

 m.), according to Argelander 6 /7< 974 ; c Indi, 7 /x *74 accord- 

 ing to D' Arrest ( 297 ) ; 2151 Puppis N (6th m.) 7 y -871. The 

 arithmetical mean ( 298 ) of the several proper motions of fixed 

 stars, taken from all the zones into which Madler has di- 

 vided the celestial sphere, would hardly exceed 0"'102. 



An important investigation into the variability of the 

 proper motions of Procyon and Sirius, had in 1844 (a 

 short time before the commencement of his painful and 

 fatal illness), impressed the mind of the greatest astronomer 

 of our time, Bessel, with the conviction, "that stars, 

 whose variable motions become sensible when examined 

 with the most perfect instruments, are parts of systems 

 which are limited to spaces small in comparison with 

 the great distances of the fixed stars from each other." 

 This belief in the existence of double stars, of which one 

 member of the pair is supposed to be non-luminous, was so 

 strong in BesseFs mind (as his long correspondence with 

 myself testified), as to add greatly to the general interest 

 excited by whatever promises to enlarge our knowledge 

 of the physical constitution of the sidereal heavens. " The 

 attracting body," said he, "must be situated either very 

 near the star which shews the observed change of place, 



