ILLUSTRATIONS
| PAGE | |
| The Lunar “Crater” Copernicus | Frontispiece |
| Photograph of South Polar Region of the Moon | 8 |
| The Moon near the “Crater” Tycho | 20 |
| Drawing of Jupiter | 28 |
| Drawing of Jupiter | 28 |
| Jupiter | 38 |
| Saturn | 46 |
| Saturn | 46 |
| The Milky Way about Chi Cygni | 58 |
| The Great Southern Star-Cluster in Centauri | 64 |
| Photograph of a Group of Sun-Spots | 76 |
| Polar Streamers of the Sun, Eclipse of 1889 | 89 |
| Solar Corona at the Eclipse of 1871 | 89 |
| Morehouse's Comet, October 15, 1908 | 96 |
| Morehouse's Comet, November 15, 1908 | 96 |
| Head of the Great Comet of 1861 | 105 |
| Halley's Comet, May 5, 1910 | 105 |
| The Six-Tailed Comet of 1744 | 112 |
| Spiral Nebula in Ursa Major (M 101) | 124 |
| The Whirlpool Nebula in Canes Venatici | 124 |
| Tress Nebula (N. G. C. 6992) in Cygnus | 132 |
| The Great Andromeda Nebula | 140 |
| Spiral Nebula in Cepheus (H. IV. 76) | 154 |
| Nebulous Groundwork in Taurus | 154 |
| Nebula in Sagittarius (M. 8) | 162 |
| The Great Nebula in Orion | 180 |
| Photographs of Mars | 200 |
| Schiaparrelli’s Chart of Martian “Canals” | 220 |
ILLUSTRATIONS IN THE TEXT
| The Rational and the Sensible Horizon | 12 |
| Altitude and Azimuth | 14 |
| Right Ascension and Declination | 35 |
| The Ecliptic and Celestial Latitude and Longitude | 51 |
| How the Earth Controls the Moon | 75 |
| The Tidal Force of the Moon | 79 |
| Refraction | 85 |
| Dip of the Horizon | 87 |
| Sidereal and Solar Time | 93 |
| The Change of Day | 101 |
| The Seasons | 107 |
| Parallax of the Moon | 139 |
| Parallax of the Sun from Transit of Venus | 141 |
| Spectrum Analysis | 147 |
| The Phases of the Moon | 160 |
| Orbits of Mars and the Earth | 183 |
| Ellipse, Parabola, and Hyperbola | 203 |
| The North Circumpolar Stars | 244 |
| Key to North Circumpolar Stars | 245 |
PART I.
THE CELESTIAL SPHERE.