Ixxvi NOTES. 



1'Acad. Imp. des Sciences de St. Petersbourg, le 29 dec. 1832, p. 48 50; 

 Madler, Astr. S. 478. 



C 337 ) p. 203. Phil. Trans, for the year 1782 p. 40126; for 1783, 

 p. 112124, for 1804, p. 87. On the observational basis of the 846 double 

 stars of Sir William Herschel, compare Madler in Schumacher's Jahrbuch fiir 

 1839, S. 59, and the same author's Untersuchungen iiber die Fisstern-Sys- 

 teme, Th. i. 1847, S. 7. 



f 338 ) p. 205. Madler in the last-named work, Th. i. S. 255. We have for 

 Castor, two old observations of Bradley's, 1719 and 1759, the first taken con- 

 jointly with Pond's, the second with Maskelyne's, and two of William Her- 

 schel's, of 1799 and 1803. For the time of revolution of \ Virginis, see 

 Madler, Fixstern-Syst., Th. ii. 1848, S. 234240. 



( 339 ) p. 205. Strave, Mensurse microrn., p. xl. and p. 234248. There 

 are, in all, 2641 + 146; therefore, 2787 observed multiple stars. (Madler, 

 i'\ Schom. Jahrb. 1839, S. 64). 



C" ) p. 205. Sir John Herschel, Astron. Observ. at the Cape of Good 

 Hope, p. 165303. 



( 3U ) p. 206. Idem, p. 167 and 242. 



( 342 ) p. 206. Argelander, in examining a large number of fixed stars for a 

 most careful investigation of their proper motion. See his memoirs, DLX 

 Stellarum fixaruni positiones mediae ineunte anno 1830, ex observ. Abose 

 habitis (Helsingforsise, 1825). Madler (Astr. S. 625), estimates at 600 

 the number of multiple stars discovered in the northern celestial hemisphere 

 at Pulkova since 1837. 



( 343 ) p. 247- The number of fixed stars in which proper motion has been 

 perceived (while we may conjecture its existence in all), is a little greater than 

 *he number of multiple stars in which a difference of relative position has been 

 observed. Madler, Astr. S. 394, 490, and 520540. Struve, in his Mens. 

 microm., p. xciv., gives the results of the application of the calculus of proba- 

 bilities to these relations, according as the distances apart of the double or 

 multiple stars are between 0' and 1', 2* and 8*, or 16* and 32.' Distances 

 less than C*'3 have been appreciated, and experiments with very closely placed 

 artificial double stars have confirmed the observer's hopes of such estimations 

 being for the most part secure, as far as 0*.l. Struve iiber Doppelsterne 

 nach Dorpater Beob. S. 29. 



( 344 ) p. 208. John Herschel, Cape Observations, p. 166. 



( 345 ) p. 208. Struve Mensurse microm., p. Ixxvii. to Ixxxiv. 

 (***) p. 208. John Herschel, Outlines of Astr., p. 579. 



