812 C. A. Young on the Solar Corona. 



thej exist but are in some way masked so that they are not 

 easily detected. 



But if we grant that the poLariscope has demonstrated the 

 derivative character of one fraction of the coronal radiance, it 

 is far more certain that the spectroscope has proved some of the 

 matter of the corona, if not all, to be self-luminous ; for ita 

 spectrum is characterized by a bright line. This line hotli 

 in 1869 and 1870 was identified with a bright line of tlie 

 chromosphere-spectrum which coincides exactly with a dark 

 Fraunhofer line at 1474 of Kirchhoflf's scale— (wave length 

 5316 according to Angstrom). Perhaps I may be allowed to 

 step a little out of my way to add, that while it is customaiy to 

 speak of this line simply as "a bright line near E," as if its 

 exact position were somewhat doubtful, there is no occasion for 

 the slightest reserve in the matter. The coincidence of the 

 bright C line of the protuberance-spectrum with the dark C is no 

 more accurately ascertained. 



In the eclipse of last December, just before the beginning of 

 the totality, the cross wires of my spectroscope were set care- 

 fully upon this line, already plainly bright in the spectrum of 

 the chromosphere ; and as soon as the sun was covered, I traced 

 it out into the corona more than 16' from the sun's limb. With 

 the full dispersive power of 13 prisms, I have never been able 

 to find the least want of correspondence between this line as 

 seen in the chromosphere and its dark analogue, except occasion- 

 ally such as was evidently due to the motion of the luminous 

 matter, producing slight changes of refrangibility, sometimes 

 in one direction and sometimes in the other. 



So far as I can learn, this line was verified last December by 

 all the spectroscopic observers who saw anything at all, with the 

 single exception of Lieut. Brown of Lord 'Lindsay's part;^. 



Two other faint lines which I saw in 1869 between tins and 

 D, and doubtfully* reported as corona-lines (see this Journal 

 for Nov. 1869, p. 376), were not seen by any one on this occa- 

 sion, unless perhaps one of them by Father Denza in Sicily- 



In a letter from Father Secchi which appeared in the Astro- 

 nomische Nachrichten for Feb. 21, 1871, he writes, " Mem coi- 

 legue le P. P. Denza directeur de V observatoire de Mancalien, obserm 

 avec un spectroscope, quefavais convenahlement dispose, deux J'fl'i^ 

 brillantes dans le courmne, une pres de VEde Fraunhofer, <««f'J 

 au milieu entre le vert et lejaune.'' Very possibly this latter ra^^ 

 " half way between the yellow and the green" may be one o 

 the two. 



Considered as a demonstration of self-luminosity, however, 

 one bright line is just as conclusive as many. 



lines in several 



me annoyance during the past year at seei g ^ ^^ 

 put upon the same footing as 1474. 1 ^^^ 



