110 LIGHT SCIENCE FOR LEISURE HOURS. 



sphere. One or two observers failed to do so ; but it 

 need hardly be said that these failures prove nothing 

 except the extreme delicacy of the observation. The 

 positive results, which need alone be considered, prove 

 decisively that next above the sun's light surface there 

 lies an exceedingly complex, but relatively very shallow, 

 atmosphere, loaded with the glowing vapours of all 

 those elements metallic or otherwise to which the 

 dark lines of the solar spectrum are known to be due. 



Next in order comes the sierra, or red envelope, 

 sometimes called the chromosphere (or more correctly 

 the chromatosphere ! ). 



The sierra is a far more extensive atmospheric 

 region than the complex atmosphere of Young and 

 Secchi. Its average depth is probably about five 

 thousand miles. Its chief constituent is glowing 

 hydrogen, but it contains other elements, and is indeed 

 far less simple in constitution than was supposed a 

 year or two since. That this is so is proved by the 

 fact that Professor Young has counted no less than one 

 hundred and twenty lines in the spectrum of this red 

 atmosphere. 



Above the red sierra, and reaching even beyond 

 the loftiest prominences, lies yet another atmospheric 

 envelope the inner corona, as it has been called. 



The consideration of this important solar envelope 

 leads us to one of the most important of the dis- 



1 Strictly speaking, the word ' chromosphere ' is as incorrect as 

 4 phography ' would be for photography, ' chromic ' for chromatic, or 

 4 chronatic ' for chronic. 



