CHAPTER XXII. 



THE SOLAR ATMOSPHERE ON THE NEW HYPOTHESIS. 



BEFORE we attempt to apply further tests we must thoroughly 

 consider the change of front in solar research necessitated by 

 the introduction of the view of the possible dissociation of 

 elementary bodies at solar temperatures. We must first consider 

 what solar facts we may expect on the two hypotheses to com- 

 pare with the result of laboratory experiments. 



On the old hypothesis the construction of the solar atmo- 

 sphere was imaged as follows : x 



(1.) We have terrestrial elements in the sun's atmosphere. 



(2.) They thin out in the order of vapour density, all being 

 represented in the lower strata, since the temperature of the 

 solar atmosphere at the lower levels is incompetent to dissociate 

 them (see p. 168.) 



(3.) In the lower strata we have especially those of higher 

 atomic weight, all together forming a so-called "reversing 

 layer " by which chiefly the Fraunhofer spectrum is produced. 



The new hypothesis necessitates a radical change in the above 

 views. According to it the three main statements just made 

 require to be changed as follows : 



(1.) If the terrestrial elements exist at all in the sun's 

 atmosphere they are in process of ultimate formation in the 

 cooler parts of it. 2 



1 See ante, Chapter XIII. 2 See ante, p. 201 at bottom. 



