THE SUN'S TRUE ATMOSPHERE. 113 



the same way we may conceive that there exists at all 

 times a solar atmospheric region beneath as well as 

 above the cloud-layer which forms the sun's visible 

 surface, and beneath and between the other cloud- 

 layers revealed by telescopic observations. 



But passing from the very difficult question sug- 

 gested by the consideration of regions below the sun's 

 visible surface, let us discuss briefly the bearing of 

 Professor Young's discovery upon our views respecting 

 those outer regions the coloured prominences and 

 sierra, the corona itself, and, in fine, all the portions 

 of space which lie above the true atmosphere. 



In the first place, it seems to me that the observa- 

 tions made during the late eclipse dispose finally of 

 the theory that the coloured sierra is an atmospheric 

 envelope, properly so-called. I had long since been 

 led to question whether the sierra could be so regarded. 



Let me remind the reader that the sierra is nothing 

 more nor less than the region which Lockyer redis- 

 covered in 1868. It had, in fact, been recognised by 



1 telescopists since 1806, the name sierra having been 

 given to it by the observers of the eclipse of 1842. It 

 is a red region, having (as its name implies) a serrated 

 upper surface, as seen in the telescope, and seemingly 

 extending all round the sun's disc. The red pro- 

 minences appear to spring from its upper surface. 

 Strangely enough, when Lockyer made his ingenious 

 observations of the coloured prominences, he had not 



, heard of this discovery, or had forgotten it. Accord- 

 ingly, finding traces of prominence-matter all round the 



I 



