^6 



NA TURE 



^Nov. 12, 1885 



probably been produced by the downrtish of comparatively 

 cold matter from above, a conclusion which has since been 

 abundantly verified by spectroscopic observations. 



In fine, these phenomena attest the existence o: an ex- 

 tensive and extremely active solar atmosphere, vv'hich 

 grows quickly colder as we ascend from the sun's surface, 

 and a spot with its accompanying faculae may perhaps be 



looked upon in the light of a celestial hurricane or hail- 

 storm. 



We have in the spot the downrush of a vast quantity of 

 comparatively cold matter from above, and in the 

 faculse the necessary re-action of this, or the uprush 

 of comparatively hot matter from below, the scale 

 of the operation being occasionally of such a vast 

 magnitude that thirty or forty of our earths might 

 be buried in the pit which represents a spot. 



What we have on a large scale in spots and 

 facula; we have on a small scale all over the sun's 

 disc. When viewed with a powerful telescope the 

 brightness of his disc is found to be far from uni- 

 form, the whole surface being made up of bright 

 and dark patches existing side by side. This 

 mottled appearance was first noticed by the elder 

 Herschel. who considered the pores, as he termed 

 them, to be small spots — a conclusion which has 

 since been abundantly verified by the spectroscope. 

 (Hiite recently M. Janssen, the well-known French 

 observer, has obtained admirable photographs of 

 the sun, exhibiting this mottled appearance on a 

 very large scale. In Fig. 12 we have a picture of a 

 cyclonic sun spot, while in Fig. 13 we have one of 

 faculse surrounding a spot seen near the sun's edge. 

 Fig. 14 again is a picture by Secchi exhibiting the 

 general mottled appearance round a spot, and the 

 lengthening out of the irregular masses into "straws" 

 in the penumbra. 



The phenomena which I have just described are 

 those which are seen projected upon the solar disc. 

 I now go on to describe those which take place 

 near his border. On the occasion of total solar 

 eclipses red flames, or /iroini'nences, are seen to 

 surround the darkened disc of our luminary. At 

 lust it was not known whether these belonged to 

 the sun or not, but we are now quite certain that 

 they are true solar appendages. On the same 

 occasions we have, in addition to the red flames, 

 a solar corona, or glory, extending sometimes to a 

 \ery great distance around the solar disc, perhaps 

 even a million of miles or more. Recent observa- 

 tion has proved that this corona is likewise, in part, 

 at least, an undoubted solar appendage. 



Having now described the results given us by 

 telescopic observation, let nie proceed to those 

 which the spectroscope reveals. Allusion has 

 already been made to the dark lines which occur 

 in the solar spectrum, and which form the charac- 

 teristic diflerence betwixt his spectrum and that of 

 the electric light. We have also mentioned the 

 fact that the double solar line D corresponds quite 

 exactly in spectral position with the bright lines 

 given out by incandescent sodium, and that Prof. 

 Stokes conjecturedfromthis coincidence that sodium 

 must exist in the solar atmosphere at a compara- 

 tively low temperature. 



Professors Bunsen and Kirchhoff in their spectro- 

 scopic researches greatly extended this branch of 

 inquiry, showing that many of the dark lines of the 

 solar spectrum are coincident in spectral position 

 with bright lines seen in terrestrial spectra, and 

 concluding that the gaseous substances which 

 afford these spectra must occur in a comparatively 

 cold state in the atmosphere of the sun. The fol- 

 lowing substances have thus been found to occur 

 in the atmosphere of our luminary — hydrogen, 

 magnesium, calcium, sodium, iron, nickel, man- 

 ganese, chromium, cobalt, barium, copper, zinc, 

 titanium, aluminium. 

 The spectroscope has been applied with equal success to 

 tlie border or limb of our luminary. It was a subject of 

 some surprise that the red flames seen at the time of a 

 total eclipse should be invisible on other occasions ; and 



