Il8 LIGHT SCIENCE FOR LEISURE HOURS. 



Thus not only has the fact been proved that the 

 light producing the [green line comes, as Young had 

 reasoned, from the inner corona, but also that this 

 corona consists in part of glowing hydrogen. And 

 when I say ' in part,' I do not mean that throughout 

 a portion of its extent- the corona consists of hydrogen ; 

 but that one of the elements of which the corona is 

 formed is the familiar gas hydrogen. It appears from 

 the sequent remarks of Professor Respighi that the 

 hydrogen extends as far, or very nearly so, as the matter, 

 whatever it may be, which produces the green light of 

 the corona. Before quoting his words, I remind my 

 readers that what.'Eespighi saw was three pictures of 

 the corona in three different places one picture 

 produced by the red part of the corona's inherent 

 luminosity, another by the green part, and another by 

 the blue part of that luminosity. The three zones he 

 speaks of are not three distinct envelopes, but three 

 pictures of one and the same element. Just as the 

 spectroscopist in the case of our imagined experiment 

 with the lamp-flame could not infer that there were 

 three small conical flames, because he saw three images 

 of the single small conical flame, so Respighi knew that 

 the three rings of light which his telescope (spectro- 

 scopically armed) presented to his view, were spectral 

 images of one and the same object, the inner ring- 

 formed solar corona. 



* The green zone surrounding the disc of the moon/ 

 he says, ' was the brightest, the most uniform, and the 

 best defined. The red zone was also very distinct and 



