GrORE — A Catalogue of Binary Stars, 8^c. 583 
21. 0. Struve, 234. Owing to the discordant measures of this very- 
close and difficult double star my orbit is somewhat uncertain ; but I 
think the period found is not far from the truth. 
A recent measure is 
1886-36 : 324° : 0"-20, Engelmann. 
22. 0. Struve, 235. An arc of over 100° has been described since 
its discovery in 1844. 
Some recent measures are : — 
The companion is now moving round the aphelion end of the orbit, 
and the angular motion is therefore slow. 
23. y Yirginis = % 1670. This famous binary star has been 
frequently measured and its orbit computed, but none of the orbits 
seem altogether satisfactory. Perhaps Thiele's period of 185 years is 
nearest the truth. 
Some recent measures are as follows : — 
1883-07 
155° 
•59 : 
5" 
•222, Engelmann. 
1884-38 
155 
•73 
5 
•427,Perrotin. 
1884-89 
336 
•1 
5 
•32, Engelmann. 
1885-382 
156 
•77 
: 5 
-35, Tarrant.] 
1886-00 
157 
•27 
: 5 
•73, Doberck. 
1886-36 
333 
•2 
. 5 
•34, By photography at Paris 
Observatory. 
1887-41 
: 334 
•2 
: 5 
-43, Schiaparelli. 
1888-91 
153^ 
-8 
: 5 
-50, Leavenworth (10 nights). 
1889-31 
: 153 
•4 
: 5 
-72, Burnham (36-inch 
As the companion is now moving towards the aphelion end of the 
apparent eclipse the angular motion is of course diminishing and the 
distance increasing. 
The components have been suspected of alternate variability in 
light, and the recorded position angles, occasionally differing by 180°, 
seem to confirm this suspicion. 0. Struve found a variation of about 
0*7 magnitude. 
1880- 36 
1881- 24 
1882- 27 
1882-28 
1884-10 
65°-57 
65 -39 
69 -65 
65 -20 
64 -6 
0"-97, Doberck. 
0 -97, „ 
1 -07, Engelmann. 
refractor). 
