FIG. 47.—ERUPTIVE PROMINENCES. (“THE SUN,” BY YOUNG.)
This fantastic cloud-shape, “if shape it might be called that shape had none,” looking like some nightmare vision, was about fifty thousand miles long and sixty thousand high above the surface. The reader will notice also the fiery rain, like the drops from a falling rocket, and may add to it all, in imagination, the actual color, which is of a deep scarlet.
It may add to the-interest such things excite, to know that they have some mysterious connection with a terrestrial phenomenon,—the aurora,—for the northern lights have been again and again noticed to dance in company with these solar displays.
The eruptive prominences are very different in appearance, as will be seen by the next illustration, for which we are indebted to Professor Young.
In [Fig. 47] we have a group of most interesting views by him (drawn here on the common scale of seventy-five thousand miles to an inch), illustrating the more eruptive types, of which we will let him speak directly. The first shows a case of the vertical filaments, like those rocket-drops we saw just, now in Tacchini’s drawing, but here more marked; while the second (on the left side) is a cyclone-form, where the twisted stems suggest what we have seen before in the “bridges” of sun-spots, and below this is another example of filamentary forms.
The upper one, on the right, is the view of a cloud prominence as it appeared at half-past twelve o’clock, on Sept. 7, 1871. Below it is the same prominence at one o’clock (half an hour later), when it has been shattered by some inconceivable explosion, blowing it into fragments, and driving the hydrogen to a height of two hundred thousand miles. The lowest figure on the right shows another case where inclined jets (of hydrogen) were seen to rise to a height of fifty thousand miles.
Professor Young says of these:—
“Their form and appearance change with great rapidity, so that the motion can almost be seen with the eye. Sometimes they consist of pointed rays, diverging in all directions, like hedgehog-spines. Sometimes they look like flames; sometimes like sheaves of grain; sometimes like whirling water-spouts, capped with a great cloud; occasionally they present most exactly the appearance of jets of liquid fire, rising and falling in graceful parabolas; frequently they carry on their edges spirals like the volutes of an Ionic column; and continually they detach filaments which rise to a great elevation, gradually expanding and growing fainter as they ascend, until the eye loses them. There is no end to the number of curious and interesting appearances which they exhibit under varying circumstances. The velocity of the motions often exceeds a hundred miles a second, and sometimes, though very rarely, reaches two hundred miles.”
In the case of the particular phenomenon recorded by Professor Young in the last illustration, Mr. Proctor, however, has calculated that the initial velocity probably exceeded five hundred miles a second, which, except for the resistance experienced by the sun’s own atmosphere, would have hurled the ejected matter into space entirely clear of the sun’s power to recall it, so that it would never return.
It adds to our interest in these flames to know that they at least are connected with that up-rush of heated matter from the sun’s interior, forming a part of the circulation which maintains both the temperature of its surface and that radiation on which all terrestrial life depends. The flames, indeed, add of themselves little to the heat the sun sends us, but they are in this way the outward and visible signs of a constant process within, by which we live; and so far they seem to have a more immediate interest to us, though invisible, than the corona which surrounds them. But we must remember when we lift our eyes to the sun that this latter wonder is really there, whether man sees it or not, and that the cause of its existence is still unknown.