78. Q. What is said of the day and night of Jupiter? A. The sun is always nearly over the equator of Jupiter, and every place has nearly its five hours day and five hours night.
79. Q. How do the seasons of Earth, Mars and Saturn compare? A. They are much alike, except in length.
80. Q. How long are Saturn’s seasons? A. Each is seven and a half years long. The alternate darkness and light at the poles is fifteen years long.
81. Q. In what form are the orbits of the planets? A. Not in the form of exact circles, but a little flattened into an ellipse, with the sun always in one of the foci.
82. Q. What is that point called where a planet is nearest the sun, and what where it is farthest from it? A. The point nearest the sun is called the perihelion, and the farthest point the aphelion.
83. Q. What is the plane of the ecliptic? A. It is the plane of the earth’s orbit extended to the stars.
84. Q. What is said of the densities, sizes, and relations of the collections of matter smaller than the planets, scattered through space in the solar system? A. They are of various densities, from a cloudlet of rarest gas to solid rock; of various sizes, from a grain’s weight to little worlds; of various relations to each other, from independent individuality to related streams millions of miles long.
85. Q. By what names are they known when they become visible? A. Shooting-stars, meteors, and comets.
86. Q. How far above the surface of the earth do shooting-stars appear and disappear? A. They appear about seventy-three miles above the earth, and disappear about twenty miles nearer the surface.