584 Proceedings of the Royal Irish Academy. 
24. 42 Comae Berenices = % 1728. A binary star in whicli the 
plane of the orbit passes through, or nearly through, the earth. The 
chief apparent change is therefore in the distance, the position angle 
varying but little except by 180°. 
Some recent measures are : — 
1881- 25 : 190°-89 : 0''-61, Doberck. 
1882- 93 : 192 '11 : 0 -560, Engelmann. 
1887-43 : 193 -1 : 0 -39, Schiaparelli. 
1889-085 : 9-6:0 -55, Leavenworth. 
25. Struve, 1757. Casey's period of 401 years and mine of 340-38 
years do not represent recent measures well. My second orbit (276*92 
years) represents all the position angles from 1825 to 1887 fairly well. 
Some recent measures are : — 
1887-213 : 72°-44 : 2"-62, Tarrant. 
1887-356 : 72 -75 : 2 -79, Toung. 
1887- 425 : 72 -22 : 2 -377, Schiaparelli. 
1888- 59 : 72 -0 : 2 -46, Leavenworth. 
26. 25 Canum Yenaticorum = % 1768. A close, and for some 
years (1850-1880) a very difficult pair to measure. 
Some recent measures are : — 
1885-37 : 329°- 1 : 0"-89, Perrotin. 
1885-539 : 149 -63 : 0 '77, Tarrant {A. N., 2866). 
1887-46 : 142 -7 : 0 -72, Schiaparelli. 
27. Struve, 1819. Struve thought that this star was a binary pair, 
but Berberich has shown {Ast. Nach.^ 2518) that all the measures may 
be satisfactorily represented on the assumption of uniform rectilinear 
motion. Some recent measures are : — 
1882-27 
16°-35 
l"-39, Doberck. 
1882-28 
: 13 
-58 
1 
•16, 
1882-34 
18 
•80 
)> 
1882-45 
17 
-6 
1 
-60, Schiaparelli. 
1885-41 
11 
•5 
. 1 
•39, Perrotin. 
1887-347 
194 
-92 
1 
•28, Tarrant {A. JSf., 2898). 
1887-432 
10 
•05 
1 
•327, Schiaparelli. 
As the components are nearly equal in brightness, 180° should be 
deducted from Tarrant's measure. 
