PROPER iMOTION OF THE STARS. If 5 



tlieir distances, have, by leading to the improvement and 

 perfection of arc-graduation and optical instruments in con- 

 nection with micrometric appliances, contributed more than 

 any thing else to raise the science of observation to the 

 height which, by the ingenious employment of great merid- 

 ian-circles, refractors, and heliometers, it has attained, espe- 

 cially since the year 1830. 



Th3 quantity of the measured proper motions of the stars 

 varieS; as we intimated at the commencement of the present 

 section, from the twentieth part of a second almost to eight 

 eo3onds. The more luminous stars have in general a Blower 

 motion than stars from the fifth to the sixth and seventh mag- 

 nitudes.-^ Seven stars have revealed an unusually great 

 motion, namely : Arcturus, first magnitude (2"- 25) ; a Cen- 

 tauri, first magnitude (3"-o8) ;t (i Cassiopeia3, sixth magni- 

 tude (3"'74) ; the double star, 6 Eridani, 5-4 magnitude 

 (4"-08); the double star 61 Cygni, 5-G 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,^ and the Great Bear, No. 1830 of the catalogue of 

 the circumpolar stars by Groombridge, seventh magnitude 

 (according to Argelander, G"-974) ; £ Indi (7"-74, according 

 to D'Arrest) ;^ 2151 Puppis, sixth magnitude (7"-S71). The- 

 arithmetical!! mean of the several proper motions of the fixed 

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

 divided by Madler would scarcely exceed 0"-l02. 



An important inquiry into the "Variability of the proper 

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



* Bessel, in the Jakrhnck von Schumacher fi'ir 1839, s. 38. Arago 

 Annuaire pour 1842, p. 389. 



t a Centauri, see HeuJerson and Maclear, in the Memoirs of the 

 Astron. Soc, vol. xi., p. Gl ; and Piazzi Smyth, in the Edlnbnrgk 

 Transact., vol. xvi., p. 447. The proper motion of Arcturus, 2"-25 

 (Baily, in the same Memoirs, vol. v., p. 165), considered as that of a 

 very bright star, may be called very large in comparison with Aldeba 

 ran, 0''-185 (Madler, Centralsonne, s. 11), and a Lyrte, 0"-400. Among 

 the stars of the hrst magnitude, a Centauri, with its great proper motion 

 of 3''-58, ft rms a very remarkable exception. The proper motion of 

 the binary system of Cygnus amounts, according to Bessel (Schuni 

 Astr. Nachr., bd. xvi., s. 93), to 5"'123. 



X Schum.icher's Astr. Nachr., No. 455. 



(1835). . _ . . 



of the sixth magnitude. (Maclear, in Madler's Untcrs. uber die Fix- 



ttern-Systeme, th. ii., s. 5.) 



U Schum., Aslr Nachr., No. GGl, s. 201 



