187y.] Basic Lines common to Spots and Prominences. 249 



If they be basic, then we should expect a considerable development 

 of these lines in the spectrum of the sun's reversing layer, which spots 

 and storms enable us to study apart from the absorption going on at 

 higher levels. 



These tables enable us to settle this question, and they settle it in 

 the most conclusive way. The only constant thing about the tables 

 is, that these basic lines are always widened in the spots . However 

 badly the brighter lines of a chemical substance may be represented 

 amongst the spot lines, the basic line, which is often of the second or 

 third order of intensity and sometimes even of the fourth, is never 

 absent. 



The same fact holds almost equally true with regard to the storms. 

 The following table gives a comparison of these coincident lines of 

 Thalen's with Young's tables. 



Comparison of Thalen's coincident lines with those seen by Young 

 in solar spots and storms. 



Thalen. 



Young. 



Wave- 

 length. 



1 



Common 

 to 



Intensity. 



Spots. 



Storms. 



Widening. 



Frequency. 



Brightness. 



5207-6 



Fe Cr 



3 1 



4 



10 



6 



5203 -7 



Fe Cr 



3 1 



4 



10 



6 



5340 -2 



Fe Mn 



2 3 



2 



1 



2 



6064 -5 



Fe Ti 



2 2 



3 



5 



2 



5661-5 



Fe Ti 



3 1 



4 



15 



2 



5403-1 



Fe Ti 



2 3 



4 



5 



3 



5396-1 



Fe Ti 



2 2 



7 



4 



2 



5352-4 



Fe Co 



4 3 



2 



4 



2 



5265 -8 



Fe Co 



2 3 



2 



10 



4- 



5168 -3 



Fe m 



3 5 



4 



40 



30 



5166 -7 



Fe Mg 



2 1 



2 



30 



20 



5681 -4 



Fe Na 



3 3 



3 



2 



1 



6121-2 



Co Ca 



1 3 



4 



5 



3 



5601 -7 



Ca Fe 



4 1 



2 







5597-2 



Ca Fe 



3 1 



2 







5856-5 



Ca M 



3 4 



2 







5425 -0 



Ba Ti 



3 3 



4 







6449 -0 



Ca Ba 



2 3 



2 







So far as my own knowledge of these matters goes, I can imagine 

 no severer test to apply to the hypothesis which I have lately advanced, 

 and to my mind the proof is conclusive that at the temperature of the 

 sun's reversing layer, we Lave a mixed mass of vapours in which the 

 base is more predominant than the chemical substances to which that 

 base is common. 



