But what shall be thought of rosy flames mounting to a height of fifty or a hundred thousand miles above the edge of the sun? What shall be thought of a tongue of fire long enough to fold three or four times round our solid earth? What shall be thought of the awful rush of burning gases, sometimes seen, borne along at the rate of one or two or even three hundred miles in a single second across the sun’s surface? What shall be thought of the huge dark rents in this raging fiery ocean, rents commonly from fifty to one hundred thousand miles across, and not seldom more? Fifty thousand miles! A mere speck, scarcely visible without a telescope; yet large enough to hold seven earths like ours flung in together. The largest spot measured was so enormous that eighteen earths might have been arranged in a row across the breadth of it, like huge boulders of rock in a mountain cavern; and to have filled up the entire hole about one hundred earths would have been needed. It is well to grow familiar with certain names given by astronomers to certain parts of the sun. The round shining disk or flat surface, seen by all of us, is called the _photosphere_, or “light-sphere.” It has a tolerably well-defined edge or “limb,” and dazzles the eye with its intense brightness. Across the photosphere the spots move, sometimes many, sometimes few, in number. Besides the dark spots, there are spots of extreme brilliancy, standing out on even that dazzling surface, which causes a piece of white-hot iron to look black and cold by contrast. These extra-radiant spots which come and go, and at times change with great rapidity, are named _faculæ_--a Latin word meaning “torches.” At the edge of the photosphere astronomers see what has been already mentioned, that which is sometimes called the _chromotosphere_, which one has named “the _sierra_,” and which another has described as “a quivering fringe of fire.” The waves of the sea, on a stormy day, seen in the distance rising and breaking the horizon-line, may serve as an illustration; only in the sun the waves are of fire, not water. What must their height be, to be thus visible at a distance of ninety-three millions of miles? Outside the _sierra_ are seen, at certain seasons, bright, “rose-colored prominences” or flames of enormous height. During an eclipse, when the dark body of the moon comes between the sun and us, exactly covering the photosphere, these red tips stand out distinctly beyond the edge of sun and moon. Their changes have been watched, and their height repeatedly measured. Some are so lofty that ten little earths such as ours might be heaped up, one upon another, without reaching to their top. Whether they are in character at all like the outbursts from our own volcanoes it is hard to say. To compare the two would be rather like comparing a small kitchen fire with a mighty iron-smelting furnace. The faculæ, the sierra, and the prominences are visible only through a telescope.