OP ARTS AND SCIENCES : MARCH 8, 1864. 243 



tial body, except, perhaps, the sun, the moon, and the principal exterior 

 phmets. 



The reason is, that all observers of the northern hemisphere must 

 depend upon it in a great degree to assure themselves of the position 

 of their instruments. 



Not only has this star been much observed, but many of the obser- 

 vations have been made serviceable for the determination of its posi- 

 tion ; whatever accuracy is possible in the place of a star should char- 

 acterize the place of this. Nevertheless, there does not seem to be 

 perfect security about its right-ascension ; the different predictions of it 

 given in different places do not harmonize so well with each other, or 

 with observation, as might, perhaps, be expected. Thus, for example, 

 the fifty-two consecutive transits which I have observed at the Harvard 

 College Observatory (with the Simms meridian circle), in pursuance of 

 the definitive plan mentioned in the Report of Professor Bond for 

 1862 (pp. 24-26), give the star's mean right ascension for 1863.0, 



1^ Q'" 0^34, 



or gi-eater by O'.Bl than Wolfers's prediction in the Berliner Astro- 

 nomisches Jahrbuch for that year, and greater by 1'.22 than that given 

 in Dr. Gould's pamphlet, " Standard Places of Fundamental Stars, U. 

 S. Coast Survey." 



Reducing this back to 1860.0 by the proper motion now employed 

 in the Jahrbuch, we have 



Cambridge Observations, 1860.0 I'' S" 3^464 



Wolfers " " 2.654 Obs. — W. =-f0'.81 



Bessel- Zech (Jahrbuch for 1860) 2.799 Obs. — B. Z. = -i-0.66 



Gould (for 1860) 2 .32 Obs. — G. =4-1-14 



2. So far, then, as my own observations go, the earlier prediction of 

 Bessel, the elements of which were determined in 1826, is more accu- 

 rate than either of the later ones. It remains now to examine other 

 observations made lately, to see if they concur in the same conclusion. 

 One observer's work may be, and probably is, afiected by a personal 

 equation. We will compare Dr. Gould's tables of A. R. of Polaris, which 

 extend from 1851 to 1863, with the observations made at Greenwich, 

 Paris, and Cambridge, England, so far as the volumes containing them 

 have reached us. To this will be added a comparison with Bessel's 

 Tabula Regiomontanse, as continued from the same elements by Pro- 

 fessor Zech. 



