A. MATHEMATICS AND ASTRONOMY. 7 



at Dunsink show that the distinguished astronomer is attain- 

 in^ results of the highest accuracy, which must be classed 

 among the most trustworthy of all the data possessed in this, 

 the most difficult field of astronomical investigation. One 

 of the most interesting stars in the heavens is that generally 

 known as No. 1830 of Groombridge's Catalogue, whose large 

 proper motion was discovered by Argelander in the year 

 1842. This star has since that time been the object of sev- 

 eral series of observations made for the purpose of determin- 

 ing its parallax. The results obtained by Peters, Wichman, 

 and Otto Struve have all established beyond reasonable 

 doubt that the parallax of this star is much smaller than 

 might be expected from its large proper motion ; and the 

 new series of observations made by Dr. Briinnow, while con- 

 firming: this general conclusion, has conduced to fix the exact 

 value of the parallax within very narrow limits. As is well 

 known, the determination of relative parallax is obtained 

 either by measuring the angular distance between the star 

 under investigation and other very faint stars in its immedi- 

 ate neighborhood, or else by observing the position angles of 

 the lines joining such stars. Dr. Briinnow has adopted the 

 former of these methods of observation, having selected his 

 comparison stars in such positions, with reference to the cen- 

 tral star, that the systematic errors committed in making ob- 

 servations should have opposite influences upon the resulting 

 parallax. He concludes that the observations indicate a 

 parallax of nine hundredths of a second for the star in ques- 

 tion. A similar series of measurements was made upon the 

 star Sigma Draconis, for which body a parallax of about 

 one fourth of a second seems to be well established. For the 

 double star No. 85 Pegasi he deduces the interesting result 

 that there is possibly a difference in the value of the constant 

 of aberration for the two components of the star, with which 

 assumption there follows a parallax of five hundredths of a 

 second, a result, however, which demands further investiga- 

 tion. For the double star No. 3077, of Bradley, he deduces 

 a parallax of seven hundredths of a second. An investiga- 

 tion of the parallax of Alpha J^/rce, or Vega, leads to a value 

 not materially different from those found before by other ob- 

 servers, but which has intrinsically less weight than the other 

 determinations attained by him, inasmuch as the observations 



