TWO YEARS LATER. 35 



envelope, corresponding, though not absolutely iden- 

 tical in structure, with the prominences. Mr. Lockyer 

 called this envelope the chromosphere (for chromato- 

 sphere), and it would seem no undeserved compliment 

 to the acuteness of one of the most indefatigable of 

 modern astronomers that this envelope should be known 

 in future by the name of Secchi's sierra. 1 



I have said that this envelope is not actually 

 identical in structure with the prominences. It is, 

 in factj more complicated. Only certain gaseous ele- 

 ments of the sierra seem capable of rising to the 

 enormous height attained by the prominences. In 

 these great masses the principal element is hydrogen, 

 but in the sierra many elements are commonly recog- 

 nised such as sodium, magnesium, barium, iron, &c. 

 while under favourable circumstances the bright lines 

 in the sierra are so numerous as to indicate the pre- 

 sence of quite a large proportion of the elements which 

 exist in the sun's substance. 



But then other modes of research with the spectro- 

 scope came into operation. Mr. Lockyer entered into 

 an alliance with Dr. Frankland, one of the most 

 eminent physicists of the day, and very quickly the 

 wisdom and advantage of this course were manifested. 

 It is one of the most promising characteristics of 

 spectroscopic research, that work done in the labora- 

 tory becomes available to tell us of the structure of orbs 

 many millions of miles away from us. Dr. Frankland 



1 I "write thus with perfect knowledge that other astronomers had 

 jet earlier suspected the existence of the chromosphere. 



D 2 



