1869.J Astronomy. 91 



besides showing but faint traces of the corona, were all covered 

 with spots. 



The chief fruit of the expeditions has been the discoTery that the 

 rose-coloured prominences are gaseous. This discovery has already 

 led to one of the most interesting applications of spectroscopic 

 analysis ever yet made by astronomers. 



We must premise that two years ago, in a paper addressed to 

 the Koyal Society, Mr. J. Norman Lockyer called attention to the 

 possibility that spectroscopic analysis might avail to exhibit indi- 

 cations of the existence of the coloured prominences. He said, 

 " May not the spectroscope afford an evidence of the existence of 

 the red flames Vv'hich total eclipses have revealed to us in the sun's 

 atmosphere, although they escape all other methods of observation 

 at other times ? " Not content with pointing out this method, ]\Ir. 

 Lockyer aj^plied it to the search for prominences, making use of a 

 spectroscope with which he had abeady been able to analyze the 

 hght of the solar spots. He failed, however, in detecting any traces 

 of the prominences with this instrument ; and, indeed, he was led 

 to the conclusion that the prominences are not gaseous. " A diligent 

 spectroscopic analysis," he wrote last July, " has not revealed any 

 bright hues. This is strong negative evidence that they are not 

 masses of incandescent vapour or gas." 



So soon, however, as the news from the echpse expeditious 

 showed that he had come to this conclu3ion too hastily, he prepared 

 to renew the search with an instrument which was (at the time) 

 being constructed for him by Mr. Browning, the optician ; and on 

 the 20th of October he succeeded in detecting the bright hne spec- 

 trum of a prominence. 



But in the meantime, unfortunately for Mr. Lockyer's claim to 

 priority, M. Janssen, who had been one of the first to detect the 

 true nature of the prominences, was led to conceive the notion that 

 their spectra may possibly become visible when the sun is shining 

 with full splendour. He did not lose any time in putting his ideas 

 into practice ; for the day after the occurrence of the eclipse he suc- 

 ceeded in observing the spectrum of a prominence. Thus, two 

 months before Mr. Lockyer, he had solved the important problem of 

 " grasping and measuring by spectral analysis phenomena before 

 invisible." 



Had M. Janssen sent home intelligence of his success _ by the 

 same means asrhe had employed in the matter of his eclipse ob- 

 servations, his claim to the merit of the discovery would have been 

 indisputable. This, however, he did not do. He sent a letter con- 

 taining an account of his researches, and it happened, singularly 

 enough, that this letter reached the President of the French Academy 

 of Sciences a few minutes after Mr. De la Kue had read before 

 the Academy a detailed account of Mr. Lockyer's researches. 



