On page 19 is a separate view of the plume ([Fig. 18]), a fac-simile of the original sketch, which was made with the eye at the telescope. The pointed or flame-like tips are not a very common form, the terminals being more commonly clubbed, like those in Father Secchi’s “branch of cactus” type given on page 12. It must be borne in mind, too, if the drawing does not seem to contain all that the text implies, that there were but a few minutes in which to attempt to draw, where even a skilled draughtsman might have spent hours on the details momentarily visible, and that much must be left to memory. The writer’s note-book at the time contains an expression of despair at his utter inability to render most of what he saw.
Let us now look at another and even more wonderful example. [Fig. 19] shows part of a great spot which the writer drew in December, 1873, when the rare coincidence happened of a fine spot and fine terrestrial weather to observe it in. In this, as well as in the preceding drawing, the pores which cover the sun’s surface by millions may be noted. The luminous dots which divide them are what Nasmyth imperfectly saw, but we are hardly more able than he to say what they really are. Each of these countless “dots” is larger than England, Scotland, and Ireland together! The wonderful “crystalline” structure in the centre cannot be a real crystal, for it is ten times the area of Europe, and changed slowly while I drew it; but the reader may be sure that its resemblance to some crystallizations has not been in the least exaggerated. I have sought to study various actual crystals for comparison, but found none quite satisfactory. That of sal-ammoniac in some remote way resembles it, as Secchi says; but perhaps the frost crystals on a window-pane are better. [Fig. 20] shows one selected among several windows I had photographed in a preceding winter, which has some suggestions of the so-called crystalline spot-forms in it, but which lacks the filamentary thread-like components presently described. Of course the reader will understand that it is given as a suggestion of the appearance merely, and that no similarity of nature is meant to be indicated.
FIG. 22.—SPOT OF MARCH 31, 1875. (FROM AN ORIGINAL DRAWING BY S. P. LANGLEY.)
There were wonderful fern-like forms in this spot, too, and an appearance like that of pine-boughs covered with snow; for, strangely enough, the intense whiteness of the solar surface in the best telescopes constantly suggests cold. I have had the same impression vividly in looking at the immense masses of molten-white iron in a great puddling-furnace. The salient feature here is one very difficult to see, even in good telescopes, but one which is of great interest. It has been shown in the previous drawings, but we have not enlarged on it. Everywhere in the spot are long white threads, or filaments, lying upon one another, tending in a general sense toward the centre, and each of which grows brighter toward its inner extremity. These make up, in fact, as we now see, the penumbra, or outer shade, and the so-called “crystal” is really affiliated to them. Besides this, on closer looking we see that the inner shade, or umbra, and the very deepest shades, or nuclei, are really made of them too. We can look into the dark centre, as into a funnel, to the depth of probably over five thousand miles; but as far as we may go down we come to no liquid or solid floor, and see only volumes of whirling vapor, disposed not vaguely like our clouds, but in the singularly definite, fern-like, flower-like forms which are themselves made of these “filaments,” each of which is from three to five thousand miles long, and from fifty to two hundred miles thick, and each of which (as we saw in the first spot) appears to be made up like a rope of still finer and finer strands, looking in the rare instants when irradiation makes an isolated one visible, like a thread of gossamer or the finest of cobweb. These suggest the fine threads of spun glass; and here there is something more than a mere resemblance of form, for both appear to have one causal feature in common, due to a viscous or “sticky” fluid; for there is much reason to believe that the solar atmosphere, even where thinner than our own air, is rendered viscous by the enormous heat, and owes to this its tendency to pull out in strings in common with such otherwise dissimilar things as honey, or melted sugar, or melted glass.
We may compare those mysterious things, the filaments, to long grasses growing in the bed of a stream, which show us the direction and the eddies of the current. The likeness holds in more ways than one. They are not lying, as it were, flat upon the surface of the water, but within the medium; and they do not stretch along in any one plane, but they bend down and up. Moreover, they are, as we see, apparently rooted at one end, and their tips rise above the turbid fluid and grow brighter as they are lifted out of it. But perhaps the most significant use of the comparison is made if we ask whether the stream is moving in an eddy like a whirlpool or boiling up from the ground. The question in other words is, “Are these spots themselves the sign of a mere chaotic disturbance, or do they show us by the disposition of these filaments that each is a great solar maelstrom, carrying the surface matter of the sun down into its body? or, finally, are they just the opposite,—something comparable to fiery fountains or volcanoes on the earth, throwing up to the surface the contents of the unknown solar interior?”
FIG. 23.—CIRROUS CLOUD. (FROM A PHOTOGRAPH.)
Before we try to answer this question, let us remember that the astonishing rapidity with which these forms change, and still more the fact that they do not by any means always change by a bodily removal of one part from another, but by a dissolving away and a fading out into invisibility, like the melting of a cloud into thin air,—let us remember that all this assimilates them to something cloud-like and vaporous, rather than crystalline, and that, as we have here seen, we can ourselves pronounce from such results of recent observation that these are not lumps of scoriæ floating on the solar furnace (as some have thought them), and still less, literal crystals. We can see for ourselves, I believe, that so far there is no evidence here of any solid, or even liquid, but that the surface of the sun is purely vaporous. [Fig. 23] shows a cirrous cloud in our own atmosphere, caught for us by photography, and which the reader will find it interesting to compare with the apparently analogous solar cloud-forms.
