Contents xv 



PAGE 



68. Purbach and Regiomontanus: influence of the 



original Greek authors : the Niirnberg school : 

 Walther : employment of printing : conflict 

 between the views of Aristotle and of 

 Ptolemy : the celestial spheres of the Middle 

 Ages : t\\e firmament and theprimttm mobile 86 



69. Lionardo da Vinci: tarthshine. Fracas for and 



Apian : observations of comets. Nonius. 

 FerneCs measurement of the earth . . 90 



CHAPTER IV. 



COPPERNICUS (FROM 1473 A.D. TO 1543 A.D.), 70-92 . 92-124 



70. The Revival of Learning 92 



71-4. Life of Coppernicus : growth of his ideas: publi- 

 cation of the Commenlariolus : Rheticus and the 

 Prima Narratio : publication of the De Revo- 



lutionibus 93 



75. The central idea in the work of Coppernicus : 



relation to earlier writers 99 



76-9. Tne De Bevolutionibus. The first book : the 

 postulates : the principle of relative motion, 

 with applications to the apparent annual 

 motion of the sun, and to the daily motion 



of the celestial sphere 100 



80. The two motions of the earth : answers to 



objections ....... 105 



81. The motion of the planets 106 



82. The seasons 108 



83. * End of first book. The second book : decrease 

 in the obliquity of the ecliptic : the star 



catalogue no 



84. The third book : precession . . . . .no 



85. The third book : the annual motion of the earth : 



aphelion and perihelion. The fourth book : 

 theory of the moon : distances of the sun 



and moon : eclipses Ill 



86-7. The fifth and sixth books : theory of the planets : 



synodic and sidereal periods . . . .112 

 88. Explanation of the stationary points . . . 118 



