THE SUN'S TRUE ATMOSPHERE. 95 



THE SUN'S TRUE ATMOSPHERE. 



So much attention was directed to the solar corona 

 during the discussions which preceded and followed 

 the late eclipse, that a discovery of extreme import- 

 ance but not at all associated with the corona has 

 received far less attention than it deserves. The dis- 

 covery I refer to is, in fact, more important in its bear- 

 ing on problems of solar physics than any which has 

 been made since Kirchhoff first told us how to inter- 

 pret the solar spectrum. It is also intimately con- 

 nected with the labours of that eminent physicist. I 

 propose briefly to describe the nature of the discovery, 

 and then to discuss some of the results to which it 

 seems to point. 



Astronomers have long seen reason to believe that 

 the sun has an atmosphere. And by the word atmo- 

 sphere I mean something more than mere vaporous or 

 gaseous masses, such as the prominences have been 

 shown to be. A solar envelope, complete and con- 

 tinuous as our own atmosphere, seems undoubtedly 

 suggested by the appearance which the sun's image 

 presents when thrown on a suitably prepared screen in 

 a darkened room; for then the disc is seen to be 

 shaded off continuously towards the edge, where its 

 brilliancy is scarcely half as great as at the centre. 

 The phenomenon is so readily seen, and so unmistake- 



