THE SUN S MOTION IN SPACE. 181 



R' denoting the annual motion at the mean distance of stars of 

 the corresponding magnitude, tt the parallax agreeing with the 

 magnitude according to Pickering, and E. the absolute annual 

 motion in terms of the mean radius of the earth's orbit about the 

 sun. The values of E are singularly small compared with other 

 estimates. 



(83) Folie, 1886.— In April 1886, Folie, referring again to his 

 previous communication to the Astronomische Nachrichten, quotes 

 Ubagh's results above given. 1 Beyond quotation and brief com- 

 ment nothing fresh is indicated. 



(84) Ludwig Struve, 1887, ? — Struve, comparing recent Pulkova 

 catalogues with Bradley's observations reduced by Auwers, 

 obtained 2,509 stars from which the constant of precession and 

 the apex of the solar motion could be determined. Putting R. A', 

 for the result determined from the P.M. in right ascension only, 

 Struve found for the year 1805 



R.A'. = 272°9; R.A. = 275-°1; D.= +36-°3 

 His final deduction was 



R.A. = 273°3, D.= + 27-°3 



(85) Folie, 1888. — In a theoretical paper, 3 discussing a question 

 raised by Battermann, 4 Folie points out, that if, as is required by 

 rigour, the aberration and systematic parallax are introduced in 

 any expression for the variation of the mean coordinates of a star's 

 positions at intervals of time widely separated, the parallax of the 

 star and the velocity of the solar system may be deduced from the 

 variations. 



(86) Kobold, 1890. — In 1890 Kobold commenced his elaborate 

 investigations on the motions obtaining among the members of the 



1 Note sur le mouvement du systeme solaire. — Astr. Nach., Bd. cxiv.* 

 pp. 355 - 356. 



2 Bestimrrmng der Constante der Praecession und der eigenen Bewegung 

 des Sonnensystems. — Mem. de T Acad. St. Petersbourg, 7me Serie, t. xxxv., 

 3, 1887. 



3 Sur la determination de la vitesse systematique et de la parallaxe des 

 toiles, etc.— Astr. Nach. Bd. cxix., pp. 343 - 346. 



4 See Astr. Nach., Bd. cxvin., pp. 369 - 372. Folie in reply, Ibid., 

 Bd. cxix., pp. 185-186 ; Battermann's rejoinder, Ibid., Bd. cxix., pp. 297 

 -300. 



