66 LIGHT SCIENCE FOR LEISURE HOURS. 



rated by the attractions of larger orders of bodies than 

 the stars (as planetary velocities may be regarded as 

 generated by their parent suns), we still have the last 

 two questions to answer; and, so far as can be judged, 

 these questions are at present unanswerable. 1 



AE other striking feature in the results announced by 

 Dr. Huggins is the absence of any systematic agree- 

 ment between the stellar motions he has recognised, 

 and the motion of our sun towards Hercules. It is 

 manifest that if our sun were alone in motion, the 

 actual rates of approach and recession of all the stars 

 in the heavens would be at once determined when the 

 rate of the sun's motion was determined. If, for ex- 

 ample, he were moving at the rate of twenty miles per 

 second towards the star Lambda of Hercules, he would 

 be approaching every star lying in that direction at 



1 In passing, however, I would venture to touch on this question of 

 central suns, or of central but opaque orbs round which the stars may 

 revolve, in order to remove a very prevalent misconception. It seems 

 to be commonly supposed that we cannot imagine such orbs to lie far 

 enough away to account for their not being discernible either as orbs of 

 light or by hiding more distant stars, without depriving them of the 

 attractive influence necessary to sway the motions of the stars. This, 

 however, is not the case. An orb looking as bright as Sirius, but ten 

 times as far away, if of equal density and inherent brightness, would be 

 a thousand times more massive, while the effect of distance would only 

 be to reduce its attraction one hundred times. It would, therefore, 

 attract our sun ten times as strongly as Sirius actually does. In like 

 manner, an orb one hundred times as far away as Sirius, but so large 

 as to appear as bright, would attract our sun one hundred times as 

 strongly, and so on. So that it cannot be positively asserted that 

 among the stars visible to us there may not be the central sun of the 

 sidereal scheme inordinately large and massive compared with the 

 rest, but reduced by di. stance to the same order of brightness. 



