Attraction, the attraction of the sun over the planets, and the planets for each other, has been several times mentioned. What is this attraction? Attraction is a “drawing to.” If a magnet be held near steel filings it attracts the particles of steel, and they adhere to the magnet; this attractive power is magnetic attraction. The attraction or pulling power which bodies have for each other, is called the attraction of gravity or of gravitation. All bodies have this attraction for each other, but in small bodies we do not observe it. Its force is due to the weight or mass of the bodies, and diminishes as their distance from each other increases. It is by this force, or attraction of gravitation, that whatever is thrown into the air falls towards the earth. If you throw up a ball it moves upward, obeying the force you put into your throw, but soon that force is used up, and the earth pulls the ball back. You jump, and you rise from the earth by the force expended by your legs in the act of jumping, but that force is used up soon, and the earth pulls you down. You jump from a tree or roof, and down you come to the earth, pulled by the force or attraction of gravitation. This force or attraction, exerted by the great strong sun over our earth and all other planets, keeps them travelling in nearly round paths about the sun. This attraction, exerted by the earth over the moon, keeps the moon travelling in a nearly circular path about the earth. And does not the moon then attract the earth? Oh, yes, all bodies attract each other; but the moon is of much less weight or mass than the earth, and her pull is weak in comparison; she cannot pull the earth out of her orbit. She does pull something however, and what do you suppose she pulls? She pulls the water that is on the earth, heaping it up in the tides! The tide is simply the ocean obeying the attraction of the moon. It seems a pity that in a few simple lessons on the solar system, we should use any terms that are hard to be understood. But some few such terms we have been obliged to use. “Attraction of gravitation” is one of these which we have tried to make a little plainer. “Inclination of plane to orbit” is another. What does that mean? Can we make it clear? Let us set a lamp on the table, and call it the sun. Now take an orange and call it the world. Call the stem-place, and the spot opposite, the poles of this world. Next run a knitting-needle through the orange, from pole to pole, to represent the axis on which the earth turns. As we spin our earth-orange around on its axis, let us move our needle around the lamp, in a lemon-shaped path. This shape is called an ellipse. Thus we represent the earth turning around on its axis, or over and over, and at the same time travelling around the sun.