VI 
Burnham: General Catalogue of Double Stars 
The Greenwich New Reduction of Groombridge 's Catalogue of Circumpolar Stars, received too late for 
use in Part II, contains a large number of proper motions not found in other catalogues, and the 
more important of these are given in the Appendix. 
NUMBER OF DOUBLE STARS 
The total number of real double stars now catalogued is necessarily very uncertain, and no safe 
approximation can be made, if this class is limited to physical systems, or those which are likely to 
belong to that order, judging from observations now made, the relative magnitudes and distances 
of the components, and their common proper motions where movement in space has been shown by 
meridian positions. It is certain that of the 13,655 stars contained in this Catalogue, at least several 
thousand are only optical or accidental pairs, and can have no physical relation to each other. 
This includes nearly all the pairs of Herschel II, as well as of Herschel I which are not included in 
Mensurae Micrometricae ; many of the Struve and Otto Struve stars; and more or less from all the 
modern lists. The question of drawing some kind of arbitrary line between what might be presumed 
to be physical systems, and those which it was practically certain could not belong to that class, was 
considered at an early day in the preparation of this work. It was soon apparent from a practical 
application of the principles which were supposed to govern a judicious separation of the material 
into these two classes that it could not be successfully done. A too liberal application of the rule 
would reject a comparatively small number and so accomplish but little in reducing the size of the 
catalogue; while on the other hand a rigid enforcement would necessarily exclude many stars which 
are of some interest at least, in consequence of changes already shown from proper motion. Then 
again, the names of the great astronomers attached to these stars entitle them to a place in the first 
general catalogue of double stars, independent of any consideration of the stars themselves. I have 
therefore included them all, and as far as possible re-measured the large number of neglected pairs 
of the old observers for this work. 
The distribution in the several hours of right ascension of the 13,655 stars north and south of 
the equator is shown in the following table: 
R. A. 
+ Decl. 
- Decl. 
Total 
R.A. 
+ Decl. 
- Decl. 
Total 
o" 
Si3 
132 
645 
13" 
257 
112 
369 
i 
432 
141 
573 
13 
233 
124 
357 
a 
43 
112 
S'S 
14 
3i 
126 
437 
3 
392 
123 
SiS 
IS 
277 
'45 
422 
4 
404 
143 
547 
16 
302 
II 9 
421 
5 
468 
221 
689 
'7 
316 
1 80 
496 
6 
44* 
271 
713 
18 
55 
209 
714 
7 
368 
266 
634 
9 
718 
204 
922 
8 
336 
181 
Si? 
20 
693 
196 
889 
9 
277 
127 
404 
31 
617 
191 
808 
10 
267 
104 
374 
33 
574 
132 
706 
ii 
270 
9 8 
368 
33 
479 
151 
630 
Total 
9854 
3,8n 
I 3,(>SS 
It would not be difficult, by a sorting-out and arrangement of the supposed classes of doubles 
with reference to the distribution in the heavens, to deduce various inferences based upon such 
statistics. But it seems certain at this time, with the extremely limited information furnished by all 
the discoveries and observations, that all such conclusions would be idle and useless. The time will 
doubtless come when the researches in stellar systems and stellar movements can be turned to good 
account in generalizations as to the construction and extent of the universe of stars. At present we 
know but little about less than two score of the binary systems, and practically nothing in detail of 
the hundreds and perhaps thousands of other pairs belonging to this class. The great majority of 
proper motions are more or less uncertain in direction and amount. With few exceptions, the dis- 
