146 



Royal Society :■ 



pointed out by Mr. Proctor are the stars /3, y, 5, s, £ of the Great 

 Bear, which have a community of proper motions*, while a and r\ of 

 the same constellation have a proper motion in the opposite direction. 

 Now, the spectroscopic observations show that the stars /3, y, S, s, '£ 

 have also a common motion of recession, while the star a is approach- 

 ing the earth. The star rj, indeed, appears to be moving from us, but 

 it is too far from a to be regarded as a companion to that star. 



Although it was not to be expected that a concurrence would 

 alvjays be found between the proper motions which indicate the ap- 

 parent motions at right angles to the line of sight and the radial mo- 

 tions as discovered by the spectroscope, still it is interesting to remark 

 that in the case of the stars Castor and Pollux, one of which is ap- 

 proaching and the other receding, their proper motions also are 

 different in direction and in amount — and further, that y Leonis, 

 which has an opposite radial motion to a and /3 of the same constel- 

 lation, differs from these stars in the direction of its proper motion. 



Table I.— Stars moving from Sun. 



Star. 



Compared 

 with 



Apparent 

 motion. 



Earth's 

 motion. 



Motion 

 from sun. 



Sirius 



Betelgeux », 



Kigel 



Castor , 



Eegulus , 



/3 Ursae majoris ., 



y „ » . 

 8 » 



K » v •- 



(3 Leonis 



8 Leonis 



r) Ursa? majoris . 



a Yirginis 



a Coronas borealis 



Procyon 



Capella 



Aldebaran? 



y Cassiopeiae....... 



H 



Ka 

 H 

 H 

 H 



II 

 V 



H 

 H 

 H 

 H 



H 

 H 



Mg 

 H 



28 to 36 



37 



30 



40 to 45 



30 to 35 



30 



10 to 14 



15 



15 



■17 



18 



9 to 13 



18 to 22 



22 



15 



23 to 28 



12 to 17 



17 to 21 



being collected into systems appears to be extremely well founded, and is every 

 day more confirmed by observations, though this does not take away the pro- 

 bability of many stars being still as it were solitary, or, if I may use the expression, 



intersystematical A star, or sun such as ours, may have a proper motion 



within its own system of stars, while at the same time the whole starry system 

 to which it belongs may have another proper motion totally different in quantify 

 and direction." Herschel further says, "And should there be found in any 

 particular part of the heavens a concurrence of proper motions of quite a different 

 direction, we shall then begin to form some conjectures which stars may possibly 

 belong to ours, and which to other systems." — Phil. Trans. 1783, pp. 276, 277. 

 * Mr. Proctor, speaking of these stars, says : — "Their drift is, I think, most 

 significant. If, in truth, the parallelism and equality of motion are to be re- 

 garded as accidental, the coincidence is one of most remarkable character. But 

 such an interpretation can hardly be looked upon as admissible when we remem- 

 ber that the peculiarity is only one of a series of instances, some of which are 

 scarcely less striking." — Other Worlds than Ours, p. 269. See paper in Proc. 

 Roy, Soc. vol. xviii. p. 170. 



