You may gain some clear notions as to the daily rising and setting of our sun, with the help of an orange. Pass a slender knitting-needle through the orange, from end to end, and hold it about a yard distant from a single candle in a room otherwise darkened. Let the needle or axis slant somewhat, and turn the orange slowly upon it. The candle does not move; but as the orange turns, the candle-light falls in succession upon each portion of the yellow rind. Half of the orange is always in shade, and half is always in light; while at either side, if a small fly were standing there, he would be passing round out of shade into candle-light, or out of candle-light into shade. Each spot on our earth moves round in turn into half-light, full-light, half-light, and darkness; or, in other words, has morning-dawn, midday-light, evening twilight, and night. Each spot on our earth would undergo regularly these changes every twenty-four hours throughout the year, were it not for another arrangement which so far affects this that the North and South Poles are, by turns, cut off from the light during many months together. Thus the sun is in the center of the Solar System, turning slowly on his axis; and the earth and the planets travel round him, each spinning like a teetotum, so as to make the most of his bright warm rays. But for this spinning movement of the earth, our day and night, instead of being each a few hours long, would each last six months. You may notice that, as you turn the orange steadily round, the outside surface of the skin has to move much more slowly in those parts close to the knitting-needle, than in those parts which bulge out farthest from it. Near the North and South Poles the surface of our earth travels slowly round a very small circle in the course of twenty-four hours. But at the equator every piece of ground has to travel about twenty-five thousand miles in the same time; so that it rushes along at the rate of more than one thousand miles an hour. A man standing on the earth at the equator is being carried along at this great speed, not _through_ the air, for the whole atmosphere partakes of the same rapid motion, but _with_ the air, round and round the earth’s axis. Now about the other movement of the earth--her yearly journey round the sun. While she moves, the sun, as seen from the earth, seems to change his place. First he is observed against a background of one group of stars, then against a second, then against a third. Not that the stars are visible in the daytime when the sun is shining, but their places are well known in the heavens; and also they can be noted very soon after he sets, or before he rises, so that the constellations nearest to him may each day be easily found out.