THE SYSTEM OF SIRIUS. 49 



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 Au- 

 wers 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 



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 

 1863 

 1864 

 1865 

 1866 

 1867 

 1868 

 1869 



10".08 

 9 ".84 

 10" 33 

 1D".56 

 10".61 

 10".39 

 11".18 

 10".92 



1870. 

 1871. 

 1872, 

 1873. 

 1874 

 In 75. 

 1876. 

 1877. 



65.0 

 63.0 

 61.3 



62.7 

 58.5 

 55.5 

 55.2 

 51.0 



12".06 

 11". 79 

 11 ".34 

 11 ".33 

 11".18 

 11".30 

 11".51 

 11 ".40 



VOL. XII. 4 



