A HISTORY OF SCIENCE 



ing of the astronomer of Samos did not win its way. 

 The old conservative geocentric doctrine, seemingly 

 so much more in accordance with the every-day ob- 

 servations of mankind, supported by the majority of 

 astronomers with the Peripatetic philosophers at their 

 head, held its place. It found fresh supporters pres- 

 ently among the later Alexandrians, and so fully 

 eclipsed the heliocentric view that we should scarcely 

 know that view had even found an advocate were it 

 not for here and there such a chance record as the 

 phrases we have just quoted from Archimedes. Yet, 

 as we now see, the heliocentric doctrine, which we know 

 to be true, had been thought out and advocated as the 

 correct theory of celestial mechanics by at least one 

 worker of the third century B.C. Such an idea, we 

 may be sure, did not spring into the mind of its 

 originator except as the culmination of a long series of 

 observations and inferences. The precise character 

 of the evolution we perhaps cannot trace, but its 

 broader outlines are open to our observation, and we 

 may not leave so important a topic without at least 

 briefly noting them. 



Fully to understand the theory of Aristarchus, we 

 must go back a century or two and recall that as long 

 ago as the time of that other great native of Samos, 

 Pythagoras, the conception had been reached that the 

 earth is in motion. We saw, in dealing with Pythag- 

 oras, that we could not be sure as to precisely what he 

 himself taught, but there is no question that the idea 

 of the world's motion became from an early day a so- 

 called Pythagorean doctrine. While all the other 

 philosophers, so far as we know, still believed that the 



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