30. Photograph of sun, showing spots and faculae.
29. How to measure the sun's diameter. (Copyright)
28. A trip around the earth.
27. Curvature of the earth—approaching ship. (Copyright)
26. Relative masses of sun and planets.
25. Relative sizes of sun and planets.
24. Orbits of planets all in one plane.
23. How to draw an ellipse.
22. Orbits of outer planets, with their positions.
21. Orbits of inner planets, with their positions.
