CHAPTER XIII. THE MOON AS A WORLD: DAY AND NIGHT UPON ITS SURFACE. 155 Existence of Habitants on other Planets—Interest of the Question—Conditions of Life—Absence of these from Moon—No Air or Water and intense Heat and Cold—Possible Existence of Protogerms of Life—A Day on the Moon imagined—Instructiveness of the Realization—Length of Lunar Day—No Dawn or Twilight—Sudden Appearance of Light—Slowness of Sun in Rising—No Atmospheric Tints—Blackness of Sky and Visibility of Stars and fainter Luminosities at Noon-day—Appearance of the Earth as a Stationary Moon—Its Phases—Eclipse of Sun by Earth—Attendant Phenomena—Lunar Landscape—Height essential to secure a Point of View—Sunrise on a Crater—Desolation of Scene—No Vestige of Life—Colour of Volcanic Products—No Atmospheric Perspective—Blackness of Shadows—Impressions on other Senses than Sight—Heat of Sun untempered—Intense Cold in Shade—Dead Silence—No Medium to conduct Sound—Lunar Afternoon and Sunset—Night—The Earth a Moon—Its Size, Rotation, and Features—Shadow of Moon upon it—Lunar Night-Sky—Constellations—Comets and Planets—No Visible Meteors—Bombardment by Dark Meteoric Masses—Lunar Landscape by Night—Intensity of Cold CHAPTER XIV. THE MOON AS A SATELLITE: ITS RELATION TO THE EARTH AND MAN. 171 The Moon as a Luminary—Secondary Nature of Light-giving Function—Primary Office as a Sanitary Agent—Cleansing Effects of the Tides—Tidal Rivers and Transport thereby—The Moon a “Tug”—Available Power of Tides—Tide-Mills—Transfer of Tidal Power Inland—The Moon as a Navigator’s Guide—Longitude found by the Moon—Moon’s Motions—Discovered by Observations—Grouped into Theories—Represented by Tables—The Nautical Almanac—The Moon as a Long-Period Timekeeper—Reckoning by “Moons”—Eclipses the Starting-Points of Chronologies—Furnish indisputable Dates—Solar Surroundings revealed by Eclipses when Moon screens the Sun—Solar Corona—Moon as a Medal of Creation, a Half-formed World—Abuses of the Moon—Superstitions—Erroneous Ideas regarding Moonlight pourtrayed by Artists and Authors—The Moon and the Weather—Errors and Facts—Atmospheric Tides—Warmth from Moon—Paradoxical Effect in cooling the Earth CHAPTER XV. CONCLUDING SUMMARY 184 LIST OF PLATES.