CHAPTER II.
GREEK ASTRONOMY (FROM ABOUT 600 B.C. TO ABOUT 400 A.D.), §§ 19-54 21-75
§§ 19-20. =Astronomy up to the time of Aristotle.= The Greek calendar: _full_ and _empty_ months: the _octaeteris_: _Meton’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 believers in the motion of the earth: _Aristarchus_ and _Seleucus_ 25
§ 25. _Plato_: uniform circular and spherical motions 26
§ 26. _Eudoxus_: representation of the celestial motions by combinations of spheres: description of the constellations. _Callippus_ 27
§§ 27-30. _Aristotle_: his spheres: the phases of the moon: proofs that the earth is spherical: his arguments against the motion of the earth: relative distances of the celestial bodies: other speculations: estimate of his astronomical work 29
§§ 31-2. =The early Alexandrine school=: its rise: Aristarchus: his estimates of the distances of the sun and moon. Observations by _Timocharis_ and _Aristyllus_ 34
§§ 33-4. Development of _spherics_: the _Phenomena_ of _Euclid_: the _horizon_, the _zenith_, _poles_ of a great circle, _verticals_, _declination circles_, the _meridian_, _celestial latitude_ and _longitude_, _right ascension_ and _declination_. Sun-dials 36
§ 35. The division of the surface of the earth into zones 37
§ 36. _Eratosthenes_: his measurement of the earth: and of the obliquity of the ecliptic 39
§ 37. =Hipparchus=: his life and chief contributions to astronomy. _Apollonius’s_ representation of the celestial motions by means of circles. General account of the theory of eccentrics and epicycles 40
§§ 38-9. Hipparchus’s representation of the motion of the sun, by means of an _eccentric_: _apogee_, _perigee_, _line of apses_, _eccentricity_: _equation of the centre_: the _epicycle_ and the _deferent_ 41
§ 40. Theory of the moon: _lunation_ or _synodic month_ and _sidereal month_: motion of the moon’s _nodes_ and apses: _draconitic month_ and _anomalistic month_ 47
§ 41. Observations of planets: eclipse method of connecting the distances of the sun and moon: estimate of their distances 49
§ 42. His star catalogue. Discovery of the _precession of the equinoxes_: the _tropical year_ and the _sidereal year_ 51
§ 43. Eclipses of the sun and moon: _conjunction_ and _opposition_: _partial_, _total_, and _annular_ eclipses: _parallax_ 56
§ 44. Delambre’s estimate of Hipparchus 61
§ 45. The slow progress of astronomy after the time of Hipparchus: _Pliny’s_ proof that the earth is round: new measurements of the earth by _Posidonius_ 61
§ 46. =Ptolemy.= The _Almagest_ and the _Optics_: theory of _refraction_ 62
§ 47. Account of the _Almagest_: Ptolemy’s postulates: arguments against the motion of the earth 63
§ 48. The theory of the moon: _evection_ and _prosneusis_ 65
§ 49. The _astrolabe_. Parallax, and distances of the sun and moon 67
§ 50. The star catalogue: precession 68
§ 51. Theory of the planets: the _equant_ 69
§ 52. Estimate of Ptolemy 73
§ 53. The decay of ancient astronomy: _Theon_ and _Hypatia_ 73
§ 54. Summary and estimate of Greek astronomy 74