PROBLEMS OF MODERN SCIENCE 



sun relative to one class of stars, say those brighter 

 than the seventh magnitude, to be the same as that 

 relative to fainter ones. The difference between 

 these two motions is an indication that the two classes 

 themselves are in motion relative to one another. 



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Fig. 2. DETERMINATIONS OF POSITION OF SOLAR APEX 

 (i) Eddington. (2) Boss from proper motions. (3) Campbell from radial 

 velocities. Dyson and Thackeray's determinations : (4) from B and 

 A stars ; (5) from F, G, K stars ; (6), (7), (8), (9) from 5th, 6th, yth, 

 8th magnitude stars. 



Further light has been thrown upon the prob- 

 lem by the researches of Kapteyn, published in 

 1904. His conclusions have been confirmed in 

 their main features, and further details have been 

 added by the work of British astronomers 

 Eddington and Dyson in this country, Hough 

 and Halm at the Cape. 



Let me ask you for a moment to suppose that 

 you take your stand at some central spot where 

 traffic converges from many directions, such as the 

 fountain in Piccadilly Circus. Standing there, you 



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