ASTRONOMY. 3G9 



system, and a systematic rotation of the fixed stars supposed to take 

 place in a direction parallel to the plane of the Milky Way are given. 

 In the present paper the author endeavors by using Professor Schon- 

 feld's formulae to determine the amount of the constant of precession, 

 and to find whether this hypothetical rotation exists or not. He uses 

 the declinations of the stars common to Lalande and Schjellerup, having 

 first reduced Lalande's declinations anew by von Asten's tables. The 

 comparison showed not only a number of deviations arising- from proper 

 motion, but, in a number of cases, a reference to other star catalogues 

 showed that Lalande had erred either 10".0 or 15".0. A complete list 

 is given of all these errors, as also of the proper motion detected. The 

 remainder of the investigation is carried on in three different ways, first, 

 making use of all stars which showed large differences (Schj.-Lal.) 

 which could not be clearly explained; next, excluding all these, 

 and finally leaving out all stars possessing a proper motion of 0". 2 

 or more in a great circle, while in the two first calculations only stars 

 with a proper motion in declination larger than 0".33 were excluded. The 

 stars were furthermore divided into three groups, the first containing 

 stars fainter than 8.3 mag.; the second, stars from 7.5 to 8.2 mag.; 

 the third, from 5.5 to 7.4 mag.; all the magnitudes being taken from 

 Argelauder's and Schonfeld's Durchmustcrungen. For every hour the 

 mean value of dd was taken for each group of magnitudes, and 24 equa- 

 tions of condition were formed of the form x jeos a-\- y sin a -f z = d&, 

 where <r, y, and z represent the coefficients in Schonfeld's formula for 

 dS, the third and fourth term being = 0, on account of the stars being 

 grouped round the Equator. The three groups did not show any sys- 

 tematic difference in the values of x, y, z, depending on magnitude. 

 They all give the same sign for the change of galactocentric longitude 

 (d J) of the star, but the numerical values of this change are so small 

 that the agreement of the signs probably only arises from some constant 

 error. The three calculations give corrections to the lunisolar preces- 

 sion (d if), and adopting Peters's values of the planetary precessiou, etc., 

 the general precession for the year 1800 is found equal to 50".2197, 

 50".21S3, and 50".2234. The author next makes use of the 24 values of 

 A a given in Copernicus, vol. II, pp. 152-153, first having reduced 

 rheni to Xewcomb's system. They furnish 24 equations of condition, 

 a a = u -{- v sin a + w cos a, where u, v, and w likewise represent the 

 coefficients in Schonfeld's formula for d a. The combination of u with 

 x and y gives, however, values of (7 >/• equal to about + 0".G, while the 

 declinations alone gave about — 0".8. This discrepancy may either 

 arise from the general uncertainty of the problem, or from the supposi- 

 tion that the plane of rotation of the fixed stars is parallel to that of 

 the Milky "Way, but in the latter case we have not data enough to 

 separate the precession from the rotation as long as not either the node 

 or the inclination of the plane of rotation is known through other means. 

 H. Mis. G9 24 



