180 SIR DAVID GILL_, ON THE SIDEREAL UNIVERSE. 



knows its own queen-bee and follows her, and that the two 

 swarms pass through each other. Then if you imagine all the 

 bees to be stars you will have an idea of Kapteyn's discovery of 

 the two great streams of stars. I will use Mr. Eddington's 

 method of showing this, because his method is more easily 

 understood than the original method employed by Kapteyn, 

 the discoverer. 



When Professor Lewis Boss published his catalogue of the 

 proper motions of 6,000 stars, Mr. Eddington set to work to make 

 figures exactly on the plan that I have shown you in fig. 2, and 

 instead of findins; nice ovals he found the kind of fioures shown 

 in fig. 5 (p. 192), which facetious astronomers call "Eddington's 

 rabbit show." And you see that they are very irregular figures ; 

 some are more irregular than others. Mr. Eddington discussed 

 all these by very beautiful mathematical processes. 



I have not got a model of a globe here, but Mr. Eddington 

 kindly got me a globe, and he painted on one hemisphere all the 

 figures as he actually found them. And in fig. 6 (p. 193) you will 

 see how beautifully the irregularities of these figures represent 

 the fact that there are two apices of two star drifts. All the 

 continuous lines converge to a point, and prove that there is one 

 apex towards which one set of stars is moving, and the next 

 (fig. 7) shows you by dotted lines the other apex. Mr. Ed- 

 dington thus shows us practically this : that there are two 

 streams of stars moving through each other, not quite, but 

 nearly, in opposite directions. This seems to be a leading 

 feature in the mechanics of our universe. 



I have shown you now in what direction the sun is going 

 through space, and with what velocity it is moving, and we 

 have seen that there are two great streams of stars passing 

 through each other, but I have told you nothing of the dimen- 

 sions of space as we know it or of the distances of the stars. 

 The nearest star we know of is a Centauri. I have measured 

 its distance by various methods, and it would take a lecture of 

 itself to tell you how that was done ; but, in short, if its position 

 is observed at two epochs six months apart, viz., when the earth 

 is at the extremes of its orbit round the sun, we find that the 

 position of the star is displaced by three-fourths of a second of 

 arc from its mean position. The total displacement amounts to 

 three-fourths of the diameter of a silver threepenny piece viewed 

 a mile off. 



A little time ago I delivered a presidential address to the 

 Institute of Marine Engineers, and I was comparing the accuracy 

 of old engineering measures with modern measures, and old 



