nearly fifteen in a year, or three hundred and sixty-five days, and the whole distance which it travels in this time is truly wonderful. It is more than five hundred millions of miles. The rate at which the earth moves in its path is hundred thousand miles a day. We, who live upon its surface, proceed along with it in its journey; and are therefore borne along at the prodigious rate of about sixty-four thousand miles an hour, or about eleven hundred miles a minute! This is truly an amazing subject for contemplation. While you are counting one hundred, you are carried through space eleven hundred miles! sun? How long does it take the earth to go completely round the What number of miles does the earth travel in completing How many miles does the earth one revolution round the sun? travel in a day? How many miles are we carried through space upon the earth in an hour? How many in a minute? CHAP. XLVII. PARLEY TELLS ABOUT THE SECONDARY PLANETS, OR SATELLITES, OR MOONS. I HAVE told you something about all the primary planets, or planets more commonly so called; but I have not yet told you about the secondary planets, or moons, or satellites, or attendants upon some of the primary planets. A satellite is any thing that follows or attends upon another. The moon is called a satellite because it follows or attends upon the earth. The earth is not the only planet that has a moon, or satellite, or secondary planet to accompany it. Jupiter has four, Uranus has six, and Saturn has seven. What about secondary planets? Satellites? Moons? Saturn? Uranus ? These satellites or secondary planets of Jupiter, Saturn, and Uranus, are called moons, only because they resemble the moon, which is the single satellite, or secondary or attendant planet, of our primary planet the earth. Why are the satellites of Jupiter, Saturn, and Uranus called CHAP. XLVIII. ABOUT ALL THE PLANETS TOGETHER, AND ABOUT THE ORBITS OF THE PLANETS. I HAVE now told you about all the planets belonging to the Solar System. As I have told you before, they all revolve round the sun, from west to east, in great circles, called their paths or orbits. Some of these planets are nearer the sun than others. The nearest is Mercury, which is thirty-seven millions of miles from the sun. The furthest off is Herschel, or Uranus, or the Georgium Sidus, which is eighteen hundred millions of miles from the sun. These planets are of various magnitudes or sizes. The smallest is Mercury, which is much smaller than the earth; the largest is Jupiter, In what direction do all the planets revolve round the sun? Which planet is the nearest to the sun? Which is the furthest from the sun? Which is the smallest planet? The largest? R |