76 LIGHT SCIENCE FOR LEISURE HOURS. 



earth from the sun, and is probably far vaster. What 

 then must be the distance of the centre of motion, as 

 seen from which this enormous space is reduced to an 

 almost evanescent arc ! 



It seems not unlikely that we ought to regard the 

 family of stars here recognised as bearing the same 

 general relation to the stellar universe (or to that por- 

 tion of it to which our sun belongs) that a group of 

 meteors bears to the solar system. All the drifting 

 star-families may not indeed travel around one and the 

 same centre ; or there may be no true centre, but only 

 a central region, round which these movements take 

 place : but it is impossible to consider thoughtfully 

 any instance of community of stellar motions without 

 feeling that it implies a common influence affecting in 

 the same or nearly the same way each member of the 

 drifting star-family. If there is but one such centre, 

 whether it be a single orb, or a central region of thickly 

 clustering stars, there now seems to be at least a pos- 

 sibility that we may find where this centre lies. When 

 only a few more star-families have been recognised, 

 and their motions of approach or recession determined, 

 it will be a problem of no inordinate difficulty to 

 deduce the position in space of the regions round 

 which these motions are taking place, or else to prove 

 (which would equally be a solution of the problem now 

 before us) that no such region exists, and that the stars 

 drift around more centres than one. 



Whatever success may attend the efforts made to 

 explain the stellar motions, there can be no doubt that 



