1869.] of Auf/ust S, 186S. 67 



only one violet line. Therefore all the protuberances do not appear 

 to emit identical light. 



It was remarked that the light at the corona was very faint in 

 comparison with that of the protuberances ; for whilst the light of 

 the latter gave a very vivid spectrum, the corona, in spite of the 

 rather large opening of the slit, did not give any appreciably coloured 

 spectrum. 



In the coloured lithograph which accompanied this article, the 

 artist has endeavoured to reproduce as closely as possible the various 

 spectra observed at the different stations. The upper plain one 

 gives the positions of the princij)al fixed lines in the solar spectrum, 

 the second spectrum consisting of three coloured Imes on a black 

 ground, represents the spectrum of incandescent hydrogen. Below 

 that will be seen the lines observed by M. Eayet, with the faint 

 prolongations of e, f, and a spoken of above. The one below that 

 represents the spectrum seen by Lieut, Herschel, and that observed 

 by Major Tennant follows. When this plate was prepared, no 

 detailed description of Janssen's spectrum had been received, except 

 that the lines seen were principally those of hydrogen. The two 

 lower spectra will be referred to immediately. 



We come now to a very remarkable double discovery which 

 inaugurates a field of investigation, destined to produce a rich 

 harvest of discovery in solar physics. Two years ago, Mr. Norman 

 Lockyer communicated to the Eoyal Society a paper, in which he 

 showed how the spectroscope could be employed to decide the 

 claims of two theories as to the cause of sun-spots ; and in the con- 

 cluding paragraph he remarked:* — "May not the spectroscope 

 afford us evidence of the existence of the red flames which total 

 echpses have revealed to us in the sun's atmosphere ; although they 

 escape all other methods of observation at other times ? And if so, 

 may we not learn something from this of the recent outburst of 

 the star in Corona ? " This was not a chance suggestion, for Mr. 

 Lockyer had been engaged in sweeping round the sun's edge and 

 over its disc with his spectrum apparatus, in the hopes of detecting 

 such a spectrum revelation, but owing to imperfect apparatus no 

 result was for a long time obtained. Another observer, Mr. Stone, 

 met with no better success; and Mr. Huggins, as late as May, 1868, 

 had unsuccessfully put the same idea to the test of experiment. 

 The train of reasoning is sufficiently obvious: the spectroscope 

 alters the relative brilliancy of two spectra, one of which consists 

 of a few isolated luminous rays, the other being continuous from 

 red to violet. The light of the continuous spectrum may be fanned 

 out by a system of prisms, so as to weaken the rays to any 



* ' Proceedings of the Eoyal Society,' Oct., 11, 1866, vol. xv., p. 256, 



F 2 



