322 THE WORLD MACHINE 



to the solid test. Mapping, plotting, comparing the bizarre 

 and bewildering movements of translation, which with his great 

 reflector he can demonstrate to exist, Herschel comes at last 

 to perceive or imagine that in one direction of the heavens the 

 stars are slowly separating, while in the opposite direction they 

 are surely coming together. You watch a herd of sheep upon 

 a hillside, or a multitude of men at a distance ; they form a 

 kind of blot or blur. A little nearer you begin to distinguish 

 their heads ; finally you perceive that they may be all standing 

 or moving about at some distance apart. As you draw away, 

 the process of separation is reversed the single units again 

 become a blur. There was hardly any mistaking the meaning 

 of Herschel's observation. It was that we are drawing nearer 

 1 to the stars in one direction, flying farther and farther from 

 them in another. The differences were almost inscrutably 

 minute ; the detection of each single motion had been in itself 

 a long and painful task. 



Moreover, the number of firmly established proper motions 

 which he had to go on was very small. In his first paper on 

 the subject he can use only fourteen. He did not reach his 

 conclusion from the mere weight of his evidence ; the evidence 

 was slight. You review the prodigious industry of Herschel, 

 and you gain the impression that he may have been one of 

 those tireless and unflagging investigators who lay bare the 

 truth simply by grubbing. Before his journals were published 

 a great many people thought this of Darwin. We forget that 

 the number of grubbers is not small. That Herschel's deter- 

 mination of the direction of solar motion was something more 

 is evident from the fact that it was entirely distrusted by almost 

 all the astronomers of his generation. 



Curiously enough, only a few months after his results were 

 published, a French observer, Prevost, reached a similar de- 

 duction from another series of observations than those which 

 Herschel had employed. Their results were in quite striking 

 agreement ; they pointed to the idea that our system is moving, 

 rather slowly as cosmic motions go, towards the constellation 

 of Hercules. This point may readily be fixed by extending a 

 line drawn through the three stars in the handle of the Dipper 

 which lie in a straight line, to a distance about twice the extreme 

 length of the Dipper itself, that is to say, to a point about equally 

 distant from the Pole-star and from Arcturus, 



