IV. _Celestial Measurements._-Place and time by stars. Degrees, minutes, seconds. Mapping stars. Mural circle. Slow watch. Hoosac Tunnel. Fine measurements. Sidereal time. Spider-lines. Personal equation. Measure distance--height. Ten-inch base line. Parallax of sun, stars. Longitude at sea. Distance of Polaris, a Centauri, 61 Cygni. Orbits of asteroids. V. _The Sun._--World on fire. Apparent size from planets. Zodiacal light. Corona. Hydrogen--how high? Size. How many earths? Spots: 1. Motion; 2. Edges; 3. Variable; 4. Periodic; 5. Cyclonic; 6. Size; 7. Velocities. What the sun does. Experiments. VI. _The Planets from Space._--North Pole. Speed. Sizes. Axial revolution. Man's weight on. Seasons. Parallelism of axis. Earth near [Page 277] sun in winter. Plane of ecliptic. Orbits inclined to. Earth rotates. Proof. Sun's path among stars. Position of planets. Motion--direct, retrograde. Experiments. VII. _Meteors._--Size; number; cause of; above earth; velocity; colors; number in space; telescopic view of. Aerolites: Systems of; how many known. Comets: Orbits; number of comets; Halley's; Biela's lost; Encke's. Resisting medium. Whence come comets? Composed of what? Amount of matter in. [Symbol]. VIII. _The Planets._--How many? Uranus discovered? Neptune? Asteroids? Vulcan? Distance from sun. Periodic time. Mercury: Elements; shapes, as seen from earth; transits. Venus: Elements; seen by day; how near earth? how far from? phases; Galileo. Earth: Elements; in space; Aurora; balance of forces. Tides: Main and subsidiary causes; eastern shores; Mediterranean Sea. Moon: Elements; hoax; moves east; see one side; three causes help to see more than half. Revolution: Why twenty-nine and a half days: heat--cold; how much light? Craters and peaks lighted; measured. Eclipses--Why not every new and full moon? Periodicity. Mars: Elements; how near earth? How far from? Apparent size; ice-fields; which end most? Satellites--Asteroids: How found? When? By whom? How many? Jupiter: Elements; trade-winds; how much light received? Own heat. Satellites: How many? Colors. Saturn: Elements; habitability; rings; flux; satellites. Uranus: Elements; discoverer; seen by; moon's motion. Neptune: Elements; discovered by; how? Review system. IX. _The Nebular Hypothesis._--State it; facts confirmatory. Objections--1. Heat; 2. Rotation; 3. Retrograde; 4. Martial moons; 5. Star of 1876. Evolution: Gaps in; conclusion.