Dreyer — On Astronomical Transit Observations. 



615 



and = + 0^-11. As it therefore seemed probable that the different 

 observers would find different values for the R. A. of the polar star, 

 M. Wagner, justly thinking it of interest to ascertain this, extracted 

 from the volumes of "Greenwich Observations," published before 

 1869, the E,. A. of a Ursaeminoris separately from the observations of 

 every single assistant. In order to be independent of the uncertainty 

 in the azimuth, only such results were used, for which two consecu- 

 tive culminations were observed by the same person. The following 

 H. A.s for 1865-0 of a TJrsae minoris Avcre found in this way : 



Dunkin, 



1'^ 9™ 39^-19 



from 58 observations 



ElHs, 



38 -54 



„ 48 „ 



J. Carpenter, 



38 -43 



„ 30 „ 



Criswick, 



38 -12 



„ 44 



Xerschner, 



37 -82 



„ 18 



Stone, 



36-47 



„ 8 „ 



This has again confirmed the possibility of a difterent estimation 

 of transits of polar and equatorial stars. 



The observations of artificial stars in Pulkowa began in 1870. 

 The apparatus used was the modified time-collimator of Kaiser, 

 manufactured by Tiede in Berlin, and, as already mentioned, placed 

 so that the circumstances under which the transits were observed 

 were as much as possible like those under which the natural transits 

 were taken. The following tables give the results of M. Wagner's 

 observations. When the star was made to go more slowly, a less 

 number of wire-transits were taken than when the star was going 

 with the velocity of an equatorial star. The column 8 indicates the 

 apparent velocity of the artificial star. 



1870. Motion Direct. 



log.sec.S. 



6. 



Error by 

 Eye and Ear. 



Error by 

 Chronogr. 



Number 

 ^of Obser- 

 vations.; 



Chr.-EE. 



EE + Chr. 



2 



02 

 0-12 

 0-46 

 0-67 

 1-11 

 1-21 

 1-55 

 1-76 



17"15' 

 40 40 

 69 43 

 77 39 

 86 33 

 86 28 



88 23 



89 



- 0^-018 

 -0-001 

 + -028 

 -0-039 

 + 0-05 

 + 0-02 

 + 0-22 

 + 0-31 



- 0«-089 

 -0-063 

 -0-088 

 -0-165 

 -0-12 

 -0-31 

 -0-30 



- 0-24 



^1 

 ^2 



7-6 

 8 

 7 

 3 

 6 

 7 

 7 



- Os-070 



- -062 

 -0-116 



- 0-126 



- 0-17 

 -0-29 

 -0-52 



- -55 



- 0^-053 



-0-032 



-0-030 



-0-102 



-0-035 



-0-17 



-0-04 



+ 0-03 



