xii Contents 



PAGE 



1 6. Measurement of time : the day and its division into 



hours : the lunar month : the year : the week . 17 



17. Eclipses: the saros 19 



18. The rise of Astrology ...... 20 



CHAPTER II. 



GREEK ASTRONOMY (FROM ABOUT 600 B.C. TO ABOUT 



400A.D.), 19-54 21-75 



19-20. Astronomy up to the time of Aristotle. The 

 Greek calendar : full and empty months : 

 the octaeteris : Melon's cycle . . . .21 



21. The Roman calendar : introduction of the 



Julian Calendar 22 



22. The Gregorian Calendar 23 



23. Early Greek speculative astronomy : Thales 

 and Pythagoras : the spherical form of the 

 earth : the celestial spheres : the music of 

 the spheres 24 



24. Philolaus and other Pythagoreans : early be- 

 lievers in the motion of the earth : Arist- 

 archus and Seleucus 25 



25. Plato: uniform circular and spherical motions . 26 



26. Eudoxus : representation of the celestial 



motions by combinations of spheres : de- 

 scription of the constellations. x Callippus , 27 



2 7~3- Aristotle ^his_spheres ; the phases of the moon ; 

 proofs that~the earttt iS""spherical : his 

 arguments against tfie motion of the earth : 

 relative distances of the celestial bodies : 

 other speculations : estimate of his astro- 

 nomical work 29 



31-2. The early Alexandrine school : its rise : Arist- 

 archus: his_estimates ofthe^ distances of the 

 gun jind moon. Observations by Timochatis 

 and Anstyttus 34 



33~4- Development of spherics : the Phenomena of 

 Euclid: the horizon t the zenith, poles of a 

 great circle, verticals, declination circles, the 

 meridian, celestial latitude and longitude, 

 right ascension and declination. Sun-dials . 36 



