90 Astronomical Operations at the Pulkova Observatory. 



tains but 24 of this order, so that the number of these stars is 

 more than trebled. The increase of numbers in the other orders 

 of double stars is not so great, and refers mostly to cases where 

 the companion of the star is extremely faint, while the principal 

 star is quite brilliant. The revision of the part of the heavens 

 just mentioned was to have been completed in 1842. 



We pass now to a consideration of the most important labors 

 of calculation which have been already executed at the Pulkova 

 observatory. 



Mr. Peters has made a new determination of the 7iutation^ by 

 applying 603 right ascensions of the pole star, resulting from ob- 

 servations made at Dorpat from 1822 to 1838. For this purpose 

 he compared these observed right ascensions with the positions 

 deduced from Bessel's Tabula. Regiomontance. He then, from 

 the small numerical differences arising from these comparisons, 

 established equations of condition, of which the three principal 

 unknown quantities are, 1st, the correction for the coefficient of 

 nutation, the nutation being supposed 8''-977, according to Lin- 

 denau's determination ; 2d, that to be applied to the coefficient 

 of aberration, supposed 20^^-255 according to Delambre ; 3d, the 

 annual parallax of the pole star. 



Treating these equations of condition by the method of least 

 squares, Mr. Peters has deduced from them, for the most proba- 

 ble values of these quantities resulting from the Dorpat obser- 

 vations : 



9'''2164 for the constant of nutation. 



20''-4255 for that of aberration. 

 0"-1724 for the parallax of the pole star. 



For the determination of the same quantities, Mr. Lundahl ap- 

 plied, by an analogous process, the declinations of the pole star 

 observed at Dorpat during sixteen years with a meridian-circle 

 of Reichenbach, and found for these three numbers respectively : 

 9"-2361 ; 20"-5508 ; and 0''-1473 ; values which agree satisfac- 

 torily with the preceding. Mr. Busch had previously obtained 

 9" '232 for the constant of nutation, from the observations of 

 zenith distances of stars made by Bradley from 1727 to 1747. 

 Struve adopts the mean of these three determinations 9'''"2231, 

 as the definitive value for the present state of astronomy. The 

 probable error of this mean does not exceed 0'''0154. 



