We know, of course, what the candle is made of and we also know why it burns and in a way how it gives off light and heat because we have examined it closely, but if we could get no nearer a candle flame than a quarter of a mile it is very doubtful if we could ever be able to learn anything about the real source of the flame—that is its greasy wick. [Illustration: FIG. 30.—A CANDLE FLAME SHOWING LAYERS OF FLAME.] It is much the same with the Sun, for we can only examine it at a great distance and know it by its action on our senses, for the flaming layers of the Sun are so bright that no one ever saw through them, so the real source of its light and heat—the core of the Sun—remains unknown. Fig. 31 shows the Sun as seen with a field glass. Since the Sun gives out light and heat it is easy to believe that it is a great ball of very hot gases and from what astronomers have learned of him with their wonderful instruments this idea seems to be pretty well founded. The Sun must be a tremendously hot body—for the iron and other metals in it are not only melted but they boil away like water and are changed into gases. Under certain conditions gigantic flames, called _prominences_, shown in Fig. 32, can be seen to leap from the edge, or _limb_, as it is called, of the Sun, and finally, great spots, called _sun spots_, are formed on the Sun that are so large a dozen worlds the size of our Earth could be dropped into any one of them and rattled around like marbles in a cigar box. These are a few of the reasons we are led to believe that the Sun is a seething ball of fire. =The Sun’s Layers of Flame.=—Just as the wick of a candle is surrounded with several kinds of flame, so the Sun has three layers of flame around a central core. The core of the Sun is believed to be formed of liquid gases which are about as thick as New Orleans molasses. Around this core, which is the real source of the Sun’s light and heat—and which has never been seen—is a dark layer of flame usually called the _Sun’s surface_; this layer, which is covered with numerous dark spots like freckles on the face of a red-headed boy, is called the _photosphere_, and it is this part of the Sun which gives out the most light. [Illustration: FIG. 31.—THE SUN AS WE SEE IT.] The second layer, which is called the _chromosphere_, is about 5,000 miles thick, and if you could imagine the whole world afire you would then have but a faint idea of what a mighty seething sea of flame this layer is. It is in this layer of luminous gases that terrific explosions take place and red tongues of flame, or _prominences_, are shot out for upwards of 300,000 miles.