A HISTORY OF SCIENCE 



pointed out, new epicycles were invented. There is 

 no limit to the number of imaginary circles that may be 

 inscribed about an imaginary centre, and if we con- 

 ceive each one of these circles to have a proper motion 

 of its own, and each one to carry the sun in the line of 

 that motion, except as it is diverted by the other mo- 

 tions if we can visualize this complex mingling of 

 wheels we shall certainly be able to imagine the heav- 

 enly body which lies at the juncture of all the rims, 

 as being carried forward in as erratic and wobbly a 

 manner as could be desired. In other words, the theory 

 of epicycles will account for all the facts of the ob- 

 served motions of all the heavenly bodies, but in so 

 doing it fills the universe with a most bewildering net- 

 work of intersecting circles. Even in the time of Ca- 

 lippus fifty-five of these spheres were computed. 



We may well believe that the clear-seeing Aristar- 

 chus would look askance at such a complex system of 

 imaginary machinery. But Hipparchus, pre-eminent- 

 ly an observer rather than a theorizer, seems to have 

 been content to accept the theory of epicycles as he 

 found it, though his studies added to its complexities; 

 and Hipparchus was the dominant scientific personality 

 of his century. What he believed became as a law 

 to his immediate successors. His tenets were accepted 

 as final by their great popularizer, Ptolemy, three cen- 

 turies later; and so the heliocentric theory of Aristar- 

 chus passed under a cloud almost at the hour of its 

 dawning, there to remain obscured and forgotten for 

 the long lapse of centuries. A thousand pities that the 

 greatest observing astronomer of antiquity could not, 

 like one of his great precursors, have approached as- 



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