THE SUN'S MOTION IN SPACE. 161 



(32) Wolfers, 184-1- — Wolfers contribution on the proper motion 

 of our system appeared in the monthly notices of the Geographical 

 Society of Germany for 1841. 1 



(33) Richter, Ed., 18^- 2 — In the following year the proceedings 

 of the Dessau Natural History Society contained Richter's paper 

 upon the same subject, and on the velocity of the motion. 



(34) Struve, 0., 184-2. — The determination of the solar motion 

 was next undertaken in 1841 by Otto von Struve, his researches 

 being published in 1842 at St. Petersburg. 3 It was jjpased upon 

 the proper motion of 392 stars, whose mean places according to 

 Bessel's catalogue were compared with their positions in 1825 

 deduced from observations made at the Dorpat Observatory. Of 

 these only about 134 had been iucluded in Argelander's series; 

 about 260 were new. Struve's fundamental hypothesis was that 

 the distances of the stars were in the inverse order of their 

 magnitudes; and dividing stars from the first to the seventh 

 magnitude into twelve classes, he assigned unity as the distance 

 of the first and 1 1 -34 as that of the twelfth class, following the 

 indication of the elder Struve 4 in the introduction to his catalogue 

 of double stars. 5 Otto Struve's result reduced to 1792*5 was 



R.A. = 261-°4, D,= +37-°6 

 and combining these values with the three determinations by 

 Argelander and one by Lundahl, he obtained for the same epoch, 



R.A. = 259-°2, D.= +34-°6. 



(35) Bravais, 184-S. 6 — In 1843 Bravais communicated to the 

 French Academy of Sciences, two notes on the solar- motion deter- 



1 Ueber die eigene Bewegung unseres Sonnensystems. — Monatsber. 

 Gesell. Erdkunde h., 1841, pp. 37, 38. 



2 Ueber die eigene Bewegung der Sonne und deren Geschwindigkeit. — 

 Dessau Verhandl. des Naturh. Vereins r., 1842, pp. 14-17. 



3 Mem. 1' Academie, t. v., 1842, pp. 17 - 124. — Bestimmung der Con- 

 stanten der Prsecession, mit Beriicksichtigung der eigenen Bewegung des 

 Sonnensystems. See also Astr. Nach., Bd. xxi., 1844, pp. 65 - 74. 



4 Friedrich Georg Wilhelm von Struve — Eecueil Petersb. Acad., 1832. 

 Introd. in Oat. nov. Stell dup. 



5 See Dunkin, 1863, hereinafter. 



6 Memoire sur le mouvement propre du systeme solaire dans l'espace. 

 — Journ. de Math, pur et appliq., t. viii., 1843, p. 435. Comptes rendus, 

 t. xvi., 1843,pp. 494-498; t. xvn., 1843, pp. 888-889. 



K— Nov. 7, 1900 



