Place the candle in the center of a table and call it the Sun; draw a circle a foot in diameter on the table top and around the candle with a bit of chalk. Mark one side September 22; at the next quarter of the circle mark December 21; directly opposite the September mark chalk in March 21, and finally between March and September mark June 21, all of which is shown in Fig. 78. Push the knitting needle through the center of the apple, call the apple the Earth and call one end of the knitting needle the north pole and the other end the south pole. Fasten the safety-pin through the skin of the apple and tie the string to the pin so that when the string is tied to a tack in the ceiling or some one is holding it directly over the candle the knitting needle of the apple will be tilted to the perpendicular, as shown in Fig. 79. [Illustration: FIG. 79.—APPLE TO REPRESENT EARTH SUSPENDED IN AIR.] [Illustration: FIG. 80.—POSITION OF THE EARTH AND SUN IN AUTUMN.] [Illustration: FIG. 81.—POSITION OF THE EARTH AND SUN IN WINTER.] [Illustration: FIG. 82.—POSITION OF THE EARTH AND SUN IN SPRING.] [Illustration: FIG. 83.—POSITION OF THE EARTH AND SUN IN SUMMER.] Now grasp the top of the needle, which is the north pole, with the left hand and hold the apple away from the candle, as shown in Fig. 80. This is the position of the earth to the Sun on September 22, when the Sun passes directly over the Earth’s equator, and for us autumn is at hand. Now pull the apple by its north pole toward you and around one quarter of the circle chalked on the table, as shown in Fig. 81, which is the position of the Earth to the Sun on December 21. You will see that the north pole is away from the light and heat and hence it is dark and winter there; but the south pole on the other end is getting plenty of light and heat and it is both day and summer there. This marks the beginning of our winter. [Illustration: FIG. 84.—CYCLE OF SEASONS.] Push the apple by its north pole—always being careful to keep the knitting needle tilted in the same position—around another quarter of a circle and this is where the Earth is in its orbit, and its position to the Sun on about March 21. Once again the Sun is over the Earth’s equator and all parts or our world are then lighted and heated twelve hours out of the twenty-four, and we have the beginning of spring. See Fig. 82. Again push the apple around another quarter circle and June 21 is reached. This time you will find the north pole is turned toward the Sun and this time it gets the light and heat for six months, while the south pole is away from the Sun and takes its turn of six months of night and winter. To us, however, it is the beginning of summer. Fig. 83 shows the position of the Earth to the Sun at this time. Pull the apple one more quarter of the circle round the candle and you will have completed its orbit just as the Earth swings round the Sun in 365 days. The seasons are more clearly shown in Fig. 84.