586 
Proceedings of the Royal Irish Academy. 
does not change much, except by 180°. Some recent measures 
are : — 
1880-48 
239°-35 
4" 
•79, Doberck. 
1880-65 
239 
•65 
4 
•89, 
1883-35 
240 
-9 : 
5 
•02, Engelmann. 
1885-51 
. 239 
•4 
4 
•86, By photography at Paris. 
1885-62 
: 241 
•1 
: 5 
•00, Jedrzejewicz. 
1887-402 
. 241 
•55 
5 
•00, Tarrant {A. 2898). 
I find that the plane of Doberck' s orbit is at right angles to the 
plane of the Milky Way. 
31. 7] Coronse Borealis = 5 1937. Some forty years ago it seemed 
uncertain whether the period of this binary was 43 or 66 years ; but 
now that one revolution has been completed, the question has been 
decided in favour of the shorter period. Dr. Doberck's orbit is perhaps 
the best. Some recent measures are : — 
1881-26 
121°-27 
> 
Doberck. 
1882-30 
134 
•81 
0" 
•56, 
1882-50 : 
135 
•4 : 
0 
•59, 
Schiaparelli. 
1882-61 
153 
•17 
0 
•558, 
Engelmann. 
1883-51 
153 
•16 : 
0 
•510, 
>> 
1884-52 
163 
•15 : 
0 
•642, Perrotin. 
1884-64 
165 
-64 
: 0 
•578, 
Engelmann. 
1885-58 
170 
-0 
. 0 
•61, 
1886-508 
• 178 
•56 
: 0 
•63, 
Tarrant {A. iV., 2866). 
1886-64 
: 179 
•5 
0 
•57, 
Engelmann. 
1887-51 
: 185 
•6 
0 
•60, 
Schiaparelli. 
1887-630 
: 185 
•98 
0 
•72, 
Tarrant {A. iV., 2898). 
32. /x^ Bootis = 21 1938. This is the small star near the 4^ magni- 
tude fji Bootis. The duplicity of fx^ was discovered by Sir W. Herschel 
in 1781. The change in position angle since 1782 amounts to about 
250°. The following are some recent measures : — 
1882-27 : 123°-77 : 0"-75, Doberck. 
1882-52 : 120 -4 : 0 '80, Schiaparelli. 
1885-492 : 110 ^07 : 0 -79, Tarrant {A. iV., 2866). 
1885- 63 : 116 -9 : 0 ^85, Engelmann. 
1886- 78 : 106 -2 . 0 ^70, Jedrzejewicz. 
There seems to be a physical connection between fx' and fjJ^, as all 
3 stars have a common proper motion. 
