A. At the rate of about 1,140 miles in a minute, or nineteen miles in a second. Q. What is meant by a superior, and what by an inferior planet? A. A planet whose orbit is outside, or at a greater distance from the sun than the earth's orbit, is called a superior planet; and one whose orbit is within, or at a less distance from the sun than the earth's orbit, is called an inferior planet. Q. Which are the inferior planets, and which are the superior? A. Mercury and Venus are inferior planets, and Mars, Jupiter, Saturn, Herschel, and Neptune are superior planets. Q. What are the morning and evening stars? A. Mercury and Venus, in performing their revolutions round the sun, never appear to us to be at a great distance from that luminary, and are seen sometimes to the east and sometimes to the west of the sun. When they are to the east of the sun they set after him, and are called evening stars, and when they are to the west of the sun they rise before him in the morning, and are called morning stars. Q. Are there any other planets than those before mentioned? A. Yes; there are several other planets, called asteroids, from their want of brilliancy, being more like stars than planets. Q. What is the moon? A. The heavenly orb which revolves round the earth, and whose reflected light serves to dispel the darkness of night. Q. How long is the moon in revolving round the earth? A. About 28 days. Q. What are the different appearances which the moon presents to us called? A. Its phases. Q. What is the length of the moon's diameter ? A. 2,160 miles. Q. How much larger is the earth than the moon? A. About forty-nine times larger. Q. On viewing the moon through a powerful telescope, certain bright spots are observed, accompanied by comparatively dark shadows. What are those shadows? A. They are the shadows which are cast by certain mountains in the moon. Q. Has the moon any rivers, lakes, or seas? A. No water has been seen by telescopes on its surface, but some astronomers seem to think that it has water on its surface. Q. Is the moon inhabited by living beings? A. We cannot discover with the telescope any traces of living beings. Q. At new moon, when a small portion only of the moon is illuminated, the remaining part of its disk is faintly visible. What occasions this faint illumination ? A. The part which shines the brighter of the two parts is illuminated by the sun, and the other part, which is faintly visible, is illuminated by the earth. Q. How is it that the earth illuminates the moon? A. The earth illuminates the moon by reflecting the sun's light on the moon, in the same manner as the moon reflects the sun's light on the earth; but, in consequence of the earth being much larger than the moon, the earth illuminates the moon much more powerfully than the moon illuminates the earth. Q. What causes an eclipse of the moon? A. An eclipse of the moon is caused by the earth passing between the sun and the moon, in such a manner as either totally or partially to obscure the sun from the moon. An eclipse of the moon can take place only at full moon, because then only is the earth between the sun and the moon. Q. What causes an eclipse of the sun? A. The moon passing between the sun and the earth, so as either totally or partially to obscure the sun from the earth. An eclipse of the sun can take place only at new moon, when the moon is between the sun and the earth. Q. Do the planets ever eclipse one another? A. Yes, sometimes; but not often. A. A broad, luminous belt in the heavens, which stretches every evening all across the sky, from horizon to horizon, and which, when traced, is found completely to encircle the whole sphere of the heavens. Q. What does that luminous belt consist of? A. When examined through powerful telescopes, it is found to consist of millions of stars; or to be, as Milton expresses it, "a circling zone, powdered with stars." Q. What is a comet ? A. A heavenly body, which moves round the sun, and which presents the appearance of a roundish mass of illuminated vapour, to which is often, though |