28 THE EVOLUTION OF SCIENCE. 



further than the facts, never exercising upon them any 

 intellectual power beyond that which was called into ac- 

 tion by the simple effort to see and record them. The 

 Greeks, on the other hand, early transcended this effort 

 by trying to construct a distinct mental picture of the 

 mechanism of celestial motions. To what patient and 

 persistent watching- of the stars, to what toilsome calcu- 

 lations, and to what repeated resort to mental invention, 

 were they impelled by their steady purpose to discover 

 the invisible methods of the complex motions of the 

 heavenly bodies ! — how ingenious, and. as far as the facts 

 then known were concerned, how complete was the con- 

 ception of the theory of epycycles and excentrics which 

 was established by Hipparchns ! 



The body of science is made up of the facts of nature ; 

 but the life of it consists in clear and appropriate ideas. 

 The Greeks imparted to astronomy this vital element. 

 They observed in order that they might know, and they 

 sought knowledge for the sake of truth itself. 



That the admiration of truth, and the desire to possess 

 it for its own sake, is the principle of life in science, is 

 shown not only by the superiority of the Greek over the 

 more ancient astronomy, but also by the invariably 

 growthless and degraded existence of science in the ab- 

 sence of it. The history of science shows, for example, 

 that astronomy when deprived of it was astrology ; that 

 alchemy when animated by it became chemistry ; and 

 that magic, by the entrance of this breath of life, was 

 transformed into natural philosophy. I will trace one 

 or two of these illustrations in detail. 



Astronomy and astrology existed together in Chaldea 

 and Egypt long before the beginning of Greek history, 

 and both alike were founded upon the observations of 

 the skies. So far ns these observations were employed 

 to detect facts, even if for no higher purpose than to con- 

 struct a calendar to regulate the recurrence of feasts and 



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