GrORE — A Catalogue of Binary StarSySfc. 
579 
12. Sirius. The faint companion to this brilliant star was dis- 
covered by Alvan Clark in 1862. The position angle was then about 
85°. This was reduced to about 0° at the end of 1889, the distance 
having diminished from about 10" to 5^". Recent measures show 
that the period of about 50 years is too small. My period of 58*47 
years is probably nearer the truth. The elements computed by 
me represent all the measures closely, the greatest difference 6o - 0^ 
being + 5°-95 at the epoch 1869*10, when the position angle was 
measured 74*76 by Eriinnow. But the angle was measured 7l°*67 by 
Engelmann, 1868*26, and this agrees much better with the other 
measures before and after that epoch. The following are some recent 
measures : — 
Observing with the 36-inch refractor of the Lick Observatory, 
Burnham says : " The companion to Sirius is a very easy object, under 
proper conditions, and is not likely to ever get beyond the reach of 
the large refractor. I have carefully looked for other stars near 
Sirius, but without finding anything worth noting." 
Assuming a parallax of 0"*40, my elements give the sum of the 
masses of Sirius and its companion = 2*886 times the sun's mass, 
with a mean distance of 21*45 times the sun's mean distance from the 
earth. 
I find that the plane of the orbit is at right angles to the plane of 
the Milky Way. 
13, Struve, 1037. The elements given by Madler seem very 
doubtful. The orbit is a hypothetical one, based on the supposition 
that one of the components is a close double — a hypothesis which has 
not yet been verified by telescopic observation. Some recent measures 
of the known pair are : — 
1886*144 
1886*22 
1887*14 
1887*195 
1887*238 
1888-97 
1890-27 
28^*67 
28 -66 
25 -36 
23 -66 
24 *14 
13 -85 
359 -7 
7"*21, Hough. 
7 -32, Washington Obs. 
7 *08, Young. 
6 -78, Hough. 
6 -508, Hall. 
5 -27, Burnham. 
4 '19, ,, {private letter). 
1880*22 : 312°*05 
1880*23 : 320 *93 
1884*18 : 310 -6 
1887*184 : 310 -9 
1 -23, Perrotin. 
1 -26, Tarrant. 
1"*33, Doberck. 
