On the Corona of the Sun, 



123 



as fed by the lost matter of the tails of comets. We must remember 

 that the matter which comes from the nucleus of a comet, and forms 

 its tail, and is then lost, has been shown by the spectroscope to con- 

 sist in nearly all. comets, of carbon,, hydrogen,, nitrogen, and possibly 

 oxygen.* If this matter is condensed into the discrete particles 

 which form the tail, in the same conditions of chemical combination 

 as it existed originally in the nucleus, we should expect these particles 

 to be again vaporised in their near approach to the sun ; and under 

 these conditions we should expect to find the corona to be mainly 

 gaseous, and to give a spectrum similar to that which is produced by 

 the emitted light of comets. We know that such is not the case ; 

 there is, however, a. single observation by Tacchini at Caroline Island, 

 in which in one part of the corona he suspected two of the bands which 

 are present in the ordinary cometary spectrum. His words are: — 

 " Dans le spectre du grand panache, qui etait faible et presque con- 

 tinu, et que Ton voyait seulement a fente large, j'ai observe deux 

 band es qui m'ont semble etre analogues a celles que j'ai observees 

 dans les spectres de cometes, c'est-a-dire,. la centrale et la moins 

 refrangible. "f The terms in which this unique observation is given 

 show that the lines, even if truly present, were faint and exceptional, 

 and cannot be regarded as characteristic of the coronal light. 



It may indeed be suggested that the cometary matter suffers decom- 

 position at the time when it becomes luminous near the nucleus, and 

 that carbon may be separated in a finely divided state, and go to 

 form part of the lost matter of the tail. In the case of comets- which 

 have more than one tail,, or exhibit rays driven off with a curvature 

 different from that of the principal tail, there is good reason to 

 believe, as Bredichin ha& endeavoured to show,J that each tail or 

 caudal ray consists of matter different in density, which has been 

 separated by a force of repulsion varying as the surface. It would 

 appear doubtful, even on this view, if the supply of comets' tails is 

 sufficiently regular in. amount to maintain a permanent corona about 

 the sun. 



It seems to me to be much more probable that the corona is fed 

 from the sun itself. This view is supported by the spectroscopic 

 evidence, for the coronal gas is shown to consist of substances which 

 exist also in the photosphere. The structure seen in the corona is 

 much more in harmony with the view that the matter is going up 

 from the sun, than that it. is coming down upon the sun.. 



An examination of the photographs taken at eclipses, or of Mr. 

 Wesley's admirable drawings from them, can scarcely fail to* lead an 

 unbiased student to the same conclusion as that which was forced 



* "Phil. Trans.," 1868, p: 559, and " Proc. Roy. Boo.," vol. xxxiii, p. 1. 

 f " Annuaire pour l'An 1884," p. 862. 



X " Annales de l'Observatoire de Moscou," and "Astron. Nachr.," No. 2411. 



