Astronomical Operations at the Pulkova Observatory. 93 



observations of right ascension, and O'^-SST, according to those of 

 dechnation, with a probable error of 0''-036, This agreement, for 

 two values entirely independent of each other, is remarkable. 

 Their mean gives O'^-SSQ, with a probable error of 0''-025. 



If we admit with Struve O^'-SU for the hypothetical value 

 which may be assigned to the parallax of a star of the first mag- 

 nitude, or to the angle which the radius of the earth's orbit sub- 

 tends from this star in a direction perpendicular to the visual ray, 

 it follows that the annual motion of the centre of gravity of the 

 solar system in the same direction, would be a little more than 

 once and a half this quantity, (1"54,) or about fifty-three millions 

 of leagues of twenty-five to the degree, (147,000,000 of miles.) 

 This is the first value, I believe, which any one has dared to as- 

 sign to a motion in which we all participate ; but in order to ob- 

 tain a value at all probable, there is required an astonishing degree 

 of perfection in the astronomical determinations. 



By comparing the particular motions presented by stars of dif- 

 ferent classes, with this motion of the solar system, the author 

 finds that the former, at the mean, are 2-4 times greater than that 

 of the sun ; whence it follows that this luminary may be ranked 

 among those stars which have a comparatively slow motion in 

 space. 



Mr. O. Struve subjected the direction of the solar motion to a 

 new examination, and found that this motion is directed toward 

 a point in the heavens whose position, for the middle of the 

 year 1792, was the following : R. A. 261° 23', Dec. 37° 36' N. 

 Argelander had found for these elements respectively : R. A. 

 257° 50', and Dec. N. 28° 50'. 



The agreement in right ascensions in these two determinations 

 is tolerably satisfactory, the difference being within the limits of 

 probable errors. As to the values of declination which differ 

 considerably, Struve thinks that it might result from small con- 

 stant errors in the differences of declination deduced from the 

 catalogues of 1755 and 1830. These errors cause the stars which 

 have a smaller proper motion to give a less northerly declination 

 than those whose proper motion is greater. 



By combining these two systems of values, we arrive at the 

 following, based upon the examination of seven hundred and 

 ninety-seven different stars, viz. R. A. 259° 9'-4, and Dec. N. 

 34° 36''5, with the probable errors of 2° 57' -5, and 3° 24''5 re- 



