252 COSMOS. 



7th magnitudes. 5 Seven stars have revealed an unusually 

 great motion, namely: Arcturus, 1st magnitude (2"-25) ; 

 a Centauri, 1st magnitude (3"-58); 6 /./, Cassiopeia?, 6th mag- 

 nitude (3-" 74); the double star, ^Eridani, 5 '4 magnitude 

 (4"-08) ; the double star 61 Cygni, 5*6 magnitude, (5"-123), 

 discovered by Bessel in 1812, by means of a comparison with 

 Bradley's observations; a star in the confines of the Canes 

 Venatici, 7 and the Great Bear, No. 1830 of the catalogue of 

 the circumpolar stars by Groombridge, 7th magnitude (ac- 

 cording to Argelander, 6"-9/4); i Indi (7"'74, according to 

 D'Arrest); 8 2151 Puppis, 6th magnitude (7"'871). The 

 arithmetical 9 mean of the several proper motions of the fixed 

 stars in all the zones into which the sidereal sphere has been 

 divided by Madler, would scarcely exceed 0"*102. 



An important inquiry into the " Variability of the proper 

 motions of Procyon and Sirius," in the year 1844, a short 



5 Bessel, in the Jahrbuch von Schumacher fur 1839, s. 38. 

 Arago, Annuaire pour 1842, p. 389. 



6 ot. Centauri, see Henderson and Maclear, in the Memoirs 

 of the Astron. Soc., vol. xi. p. 61 ; and Piazzi Smyth, in the 

 Edinburgh Transact., vol. xvi. p. 447. The proper motion 

 of Arcturus, 2"'25 (Baily,inthe same Memoirs, vol. v. p. 165), 

 considered as that of a very bright star, may be called very 

 large in comparison with Aldebaran, 0"-185 (Madler, Central- 

 ^onne, s. 11), and a Lyra3, 0"*400. Among the stars of the 

 1st magnitude, a, Centauri, with its great proper motion of 

 3"- 5 8, forms a very remarkable exception. The proper motion 

 of the binary system of Cygnus amounts, according to Bessel 

 (Schum. Astr. Nachr., bd. xvi. s. 93), to 5"- 123. 



7 Schumacher's Astr. Nachr., no. 455. 



8 Op. cit., no. 618, s. 276. D'Arest founds this result on 

 comparisons of Lacaille (1750) with Brisbane (1825), and of 

 Brisbane with Taylor (1835). The star 2151, Puppis, has a 

 proper motion of !" 8 71, and is of the 6th magnitude. 

 (Maclear, in Madler's Unters. uber die Fixstern-Systeme, th. 

 ii. s. 5.) 



9 Schum. Astr. Nachr., no. 661, s. 201. 



