A HISTORY OF SCIENCE 



scribe a dodecahedron the circle comprising it will be 

 that of Mars; around Mars describe a tetrahedron 

 the circle comprising it will be that of Jupiter ; around 

 Jupiter describe a cube the circle comprising it will 

 be that of Saturn ; now within the earth's orbit inscribe 

 an icosahedron the inscribed circle will be that of 

 Venus; in the orbit of Venus inscribe an octahedron 

 the circle inscribed will be that of Mercury." 3 



Though this arrangement was a fanciful one, which 

 no one would now recall had not the theorizer obtained 

 subsequent fame on more substantial grounds, yet it 

 evidenced a philosophical spirit on the part of the 

 astronomer which, misdirected as it was in this in- 

 stance, promised well for the future. Tycho Brahe, 

 to whom a copy of the work was sent, had the acumen 

 to recognize it as a work of genius. He summoned 

 the young astronomer to be his assistant at Prague, 

 and no doubt the association thus begun was in- 

 strumental in determining the character of Kepler's 

 future w r ork. It was precisely the training in minute 

 observation that could, avail most for a mind which, like 

 Kepler's, tended instinctively to the formulation of 

 theories. When Tycho Brahe died, in 1601, Kepler 

 became his successor. In due time he secured access 

 to all the unpublished observations of his great pred- 

 ecessor, and these were of inestimable value to him in 

 the progress of his own studies. 



Kepler was not only an ardent w r orker and an 

 enthusiastic theorizer, but he was an indefatigable 

 writer, and it pleased him to take the public fully into 

 his confidence, not merely as to his successes, but as 

 to his failures. Thus his works elaborate false theories 



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