remarked that this brilliant star is slowly moving in space, like all the other stars, but that its proper movement is not uniform; and Bessel announced, thirty years ago, that at some time there would be discovered, without doubt, a world of its system moving around it and disturbing it in its progress. This discovery was made in 1862. The companion of Sirius was then almost exactly on the eastern side, quite small, and buried in the rays of the star. Since that year it has been constantly watched by the aid of powerful instruments, and it is seen to slowly gravitate around the Sirian sun.
But this companion certainly does not follow the theoretic orbit calculated to correspond to the perturbations noted in the proper movement of the brilliant star. Differences more and more marked are shown between the calculated ellipse and the observed ellipse. The following is the orbit calculated by the German astronomer Auwers in 1864 to correspond with recognized perturbations:
| Passage by lower apsis | 1793.890 | |
| Annual movement | 70.28475 | |
| Period | years | 49.418 |
| Eccentricity | 0.6010 |
The last orbit calculated by Auwers, placed in the form of the orbits of double stars, and given as definitive, is the following:
| Perihelion passage | 1843.275 | |
| Longitude of node | 61°.57,8 | |
| Angle between node and perihelion | 18°.54,5 | |
| Inclination | 47°.8,7 | |
| Eccentricity | 0.6148 | |
| Semi-major axis | 7".331 | |
| Period | years | 49.399 |
From these elements, the limits of distance ought to be 2.31" at 302.5° in 1841, and 11.23" at 71.7° in 1770, and the ephemeris is—
| 1862 | 85°.4 | 10".10 | 1874 | 65°.0 | 10".95 |
| 1865 | 79°.9 | 10".78 | 1876 | 62°.1 | 10".59 |
| 1868 | 75°.0 | 11".15 | 1878 | 58°.4 | 10".05 |
| 1871 | 70°.3 | 11".20 | 1880 | 54°.2 | 9".33 |
But, in making out my "Catalogue of Double Stars in Movement," I have found that all the observations on the satellite of Sirius give the following means for each year since its discovery:
| 1862 | 84°.6 | 10".08 | 1870 | 65°.0 | 12".06 |
| 1863 | 82°.2 | 9".84 | 1871 | 63°.0 | 11".79 |
| 1864 | 79°.0 | 10".33 | 1872 | 61°.3 | 11".34 |
| 1865 | 76°.7 | 10".56 | 1873 | 62°.7 | 11".33 |
| 1866 | 75°.0 | 10".61 | 1874 | 58°.5 | 11".18 |
| 1867 | 73°.9 | 10".39 | 1875 | 55°.5 | 11".30 |
| 1868 | 70°.4 | 11".18 | 1876 | 55°.2 | 11".51 |
| 1869 | 72°.3 | 10".92 | 1877 | 51°.0 | 11".40 |
