The Epicycle 139 30. A Planet “retrograding” and “in opposition” 140 31. Venus, Mercury, and the Sun 142 32. The Sun’s Deferent 145 33. Apparent Variation in the size of the Sun. _Photographs taken at Kodaikanal Observatory, with the spectroheliograph, July 1, 1911, and Jan. 3, 1912. Actual size of the negative_ 146 34. The Moon’s Epicycle and Deferent 148 35. The Ptolemaic System 151 36. Method (erroneous) of estimating Planetary Distances, described by Alfraganus 188 37. Earth’s Shadow 192 PART II. FIG. PAGE A MEDIÆVAL ASTRONOMER. _From a painting by Gerard Dow_ 200 ASTRONOMY. _From a fresco in the Spanish Chapel of Santa Maria Novella, Florence_ 217 38. The Half-Moon shape of the Habitable Earth (Ristoro) 247 CLIMATE MAP OF ABOUT A.D. 1110. _Reproduced from Beazley’s Dawn of Modern Geography_ 248 39. Sun, Moon, and zenith. To illustrate _Par._ xxix 1-6 267 40. The Zodiac and the Months 276 41. The Ram on the Ecliptic. _From the Cosmi Historia of Robert Flud_, A.D. 1612. _Reproduced from Brown’s Aratos._ 279 MAP OF STARS VISIBLE BEFORE DAWN IN PURGATORY 295 42. Ursa Minor as a Horn. _Par._ xiii. 10 299 43. The Sun at the Equinox, seen from the poles and the equator. _Conv._ III. v. 327 44. Lunar and Solar Eclipses 339 MAP OF THE WORLD BY HEINRICH OF MAINZ, about A.D. 1110. _Reproduced from Beazley’s Dawn of Modern Geography_ 344 45. The Universe of Dante 355 46. The Signs of the Zodiac at sunrise from the Mountain of Purgatory 375 47. Northern Slope of the Mountain of Purgatory 377 48. Dante’s View of Earth from the stars. _Par._ xxii. 395 49. do. Six hours later. _Par._ xxvii. 396 50. An impossible interpretation of _Par._ xxvii. 399 51. The Rising Sun at the spring equinox. _Par._ i. 39 403 52. The Moon’s Epicycle and Deferent 449 53. Comparative sizes of the Sun and his satellites 490 ABBREVIATED TITLES OF BOOKS USED IN THE TEXT.