But what caused this sudden change? Just before the professor was interrupted, he had noticed a curious little brilliant lump--a sort of suspicious thunder-cloud appearance--below the quiet, bright cloud. And after this tremendous shattering, the little bright lump rose upwards into a huge mass of rolling flame, reaching like a pyramid to a height of fifty thousand miles. In the course of a few minutes these enormous flames could be seen to move and bend, and to curl over their gigantic tips. But they did not last long. At half-past twelve the professor had been called away; by half-past two the rolling flames completely vanished. Now, whatever may be the full explanation of this sight, there is no doubt that on that day was observed from earth a tremendous outburst, compared with which our mightiest volcanoes are like the sputtering of a farthing dip beside a roaring furnace. The awful force and greatness of such a solar eruption are more than we can possibly picture to ourselves. At our distance we may catch a faint glimpse of what is going on, and calculate speed of movement. But vividly to realize the actual terrific grandeur of what took place is past our power. Possibly this was much the same kind of outburst as that seen by the two English astronomers; only theirs was a bird’s-eye view, as it were, looking down on the top of the sight, while the professor had a side-view, certainly much the best for observation. It does not follow from what he saw that the eruption must have taken place exactly at the “edge” of the sun. Probably it happened near the edge. All he could say, was that the flames rose fifty thousand miles, and the pieces of cloud were carried two hundred thousand miles, away from the edge. The eruption may have begun on the other side of the sun, at any distance from the horizon-edge where it first became visible to earthly eyes. Also, while the professor found that the shattered cloudlets moved at a rate of about one hundred and sixty-seven miles each second, it is calculated that the first fearful outburst must have caused movement, near the surface of the sun, at a rate of at least three hundred miles each second. Probably the hydrogen cloud was borne upwards along with a vast mass of fragments flung out from the sun. We are here upon doubtful ground; but this tremendous power of eruption in the sun, and of driving matter out of and away from his surface, should not be forgotten. Though such a sun-storm as that just described is not often to be seen, yet there are at all times certain strange red prominences, or glowing flames, rising up here and there from the sun’s “limb.” Doubtless they rise also from other parts of the photosphere, though they are only visible to us when near enough to the edge to stand out beyond it.