observation. In such cases the motion is cyclonic in the majority of cases, and generally very rapid, and—another feature of a solar storm-the photospheric vapours are torn up with the intensely bright hydrogen, the number of bright lines visible determining the depth from which the vapours are torn, and varying almost directly with the amount of motion indicated. SIXTH PAPER. of promi nences with facule. Here, then, we have, I think, the chain that connects the prominences with the brighter points of the faculæ.1 These lozenge-shaped appearances, which were observed Connection close to the spot on the 16th, were accompanied by the "throbs" of the eruption, to which I have before referred. While Mr. Holiday was with me-a space of two hoursthere were two outbursts, separated by a state of almost rest, and each outburst consisting of a series of discharges, as I have shown. I subsequently witnessed a third outburst. The phenomena observed in all three were the same in kind. On this day I was so anxious to watch the various motion-forms of the hydrogen-lines, that I did not use the tangential slit. This I did the next day (the 17th of April) in the same region, when similar eruptions were visible, though the spot was no longer visible. the Fraun hofer lines at the base of the chro mosphere. Judge of my surprise and delight, when upon sweeping Reversal of along the spectrum, I found HUNDREDS of the Fraunhofer lines beautifully bright at the base of the prominence !!! The complication of the chromosphere spectrum was greatest in the regions more refrangible than C, from E to long past and near F, and high-pressure iron vapour was one of the chief causes of the phenomenon. b I have before stated to the Royal Society that I have seen the chromosphere full of lines; but the fulness then was as emptiness compared with the observation to which I now refer. A more convincing proof of the theory of the solar constitution, put forward by Dr. Frankland and myself, could See Note M. SIXTH PAPER. Appear ance of F. 7 descopic of the spots. scarcely have been furnished. This observation not only endorses all my former work in this direction, but it tends to show the shallowness of the region in which many of the more important solar phenomena take place, as well as its exact locality. The appearance of the F line, with a tangential slit at the base of the prominence, included two of the lozengeshaped, brilliant spots to which I have before referred: they were more elongated than usual-an effect of pressure, I hold; greater pressure and therefore greater complication of the chromosphere spectrum: this complication is almost impossible of observation on the disc. It is noteworthy that, in another prominence, on the same side of the sun, although the action was great, the erupted materials were simple, i.e. only sodium and magnesium, and that a moderate alteration of wave-length in these vapours was obvious. Besides these observations on the 17th, I also availed appearance myself of the pureness of the air to telescopically examine the two spots on the disc, which the spectroscope reported tranquil as to up and down rushes. I saw every clouddome in their neighbourhood perfectly, and I saw these domes drawn out, by horizontal currents doubtless, in the penumbræ, while on the floors of the spots, here and there, were similar single cloud-masses, the distribution of which varied from time to time, the spectrum of these masses resembling that of their fellows on the general surface of Spots are apparently shallowing. the sun. I have before stated that the region of a spot comprised by the penumbra appears to be shallower in the spots I have observed lately (we are now near the maximum period of sun-spots): I have further to remark that I have evidence that the chromosphere is also shallower than it was in 1868. I am now making special observations on these two points, as I consider that many important conclusions may be drawn from them. DESCRIPTION OF FIG. 149. 1. Prominence much bent. 2. Prominence encroaching over limb-bright line crossing black line. 3. Black line (F) curved downwards, sometimes nearly touching iron line below. Prominence nearly divided. 6. Intensely brilliant flashes above and below centres (of F lines); the interruptions very complete. 7 & 8. Curves in prominence very marked. 9, 10, 12, 14, 15. My own drawings, made during first and second outbursts. II. A lozenge on the limb as seen with a tangential slit. 13. A lozenge as seen on the sun itself. II.—LABORATORY WORK. FIRST PAPER. Preliminary note of Researches on Gascous Spectra in rela- I. FOR Some time past we have been engaged in a careful Although the investigations are by no means yet completed, we consider it desirable to lay at once before the Royal Society several broad conclusions at which we have already arrived. It will be recollected that one of us, in a recent communication to the Royal Society, pointed out the following facts: 1. That there is a continuous envelope round the sun, and that in the spectrum of this envelope, which has been named for accuracy of description the "chromosphere," the hydrogen line in the green corresponding with Fraunhofer's line F, takes the form of an arrowhead, and widens from the upper to the lower surface of the chromosphere. 2. That ordinarily in a prominence the F line is nearly of the same thickness as the C line. 1 FIRST PAPER. Our start points. |