THE STAKS AND NEBULAE 257 



tudes of stars, and the like, is the sole end in view, then 

 in the name of common sense and wholesome economy 

 let the farce be stopped. There is but one way to justify 

 all this labor and expense of accumulation and to lift 

 work of the same sort in the future above the plane of 

 drudgery and mental dissipation, and that is, by finding 

 a noble and structural use for it all. 



Suppose that mankind, notwithstanding all the in- 

 vestigations with telescope and spectroscope hitherto 

 made, should have continued in the belief that the earth 

 is the center of the universe and that the firmament re- 

 volves around it daily ; what genuine value would all our 

 detailed knowledge possess? The knowledge both of the 

 earth's rotation on her axis and around the sun is abso- 

 lutely indispensable to a sane interpretation of the solar 

 system. But it is no more essential to this purpose than 

 is the knowledge of the form of the sun's path in space 

 to a sane interpretation of the stellar motions and system. 

 It constitutes all the difference between truth and error, 

 between a yes and a no, whether the sun is speeding in a 

 straight line or in a curve. Doctor W. W. Campbell, 

 Director of the Lick Observatory, to whom the world of 

 astronomy looks for leadership in this special field, in 

 his magnum opus (Stellar Motions, p. 194) thus antag- 

 onizes the hypothesis of the sun's path being else but 

 rectilinear : 



These are frequent and legitimate questions: Is the solar 

 system moving in a simple orbit, such as a conic section? Will 

 it eventually complete a circuit in this orbit and return to the 

 part of its orbit where it is now? The idea of affirmative answeVs 

 to these questions appears to be prevalent in the human miftdf. 

 It is natural to think that we must be moving on a great 

 perhaps closed like an ellipse, or open like a parabola tji 

 of mass of the universe being in the curve's principal fjous % 

 attraction which any individual star is exerting upon, iiis ^s. -cer- 

 tainly slight, owing to its enormous distance, and the\feurta3fr S$- 

 traction of all the stars may not be very much greater^ * 

 we are believed to be somewhere near the 

 system, the attractions of the stars in the vari 

 nearly neutralize one another, in accordancev :w,ith ^Jac princline 

 that a body situated within a concentrically homtSrenftoUS* sgnere 



9i r a 



is effectively acted upon only by the graV 



