Elements in the Sun. 



815 



Ionization Potential U = "96xl0 5 calories — 4*16 volts. 



Pressure 



Tern p. 

 2000 

 2500 



3000 

 4000 

 5000 

 6000 

 7000 

 7500 

 8C00 

 9000 

 10000 



4 



19 

 46 

 75 

 84 

 90 

 96 

 99 



io- 



10-*. 



io- 



10 



JO 



-5 



1 



4 



17 



39 



51 



87 



85 



98 



97 





98 









2 6 

 13 37 



80 98 ] 



1 



20 



78 



Complete 

 Ionization. 





(d) Ccesium. 



Xo Caesium lines have been identified in the Frannhofer 

 spectrum. The case is identical with that of rubidium, 

 only in a more marked degree. A table of the ionization of 

 cpesium is appended below : — 



U = 3'88 volts = -90x!0 5 calories. 



Pressure 

 Temp. 

 2000 . 

 2500 . 

 3000 . 

 4000 . 

 5000 . 

 6000 . 

 7000 . 

 7500 

 8000 

 9000 



7 



25 

 56 

 81 

 88 

 92 

 98 



io- 



1 

 20 

 62 

 90 

 975 

 99 



10" 



10 



-3 



10" 



1 



4 



53 

 92 



io- 



3 8 



4 11 34 



12 35 75 



89 98-5 in- 



complete 

 Ionization. 



Oxygen. 



The presence of oxygen in the sun was a matter of great 

 controversy until a few years ago. The well-known bands 

 A, 13, a were shown by Jansen * to be of telluric origin — 

 t. <?., caused by the absorption of the solar light by the mole- 

 cular oxygen of our own atmosphere. But Runge and 

 Paschen identified the weak Fraunhofer triplet, \ = 7772*20, 



* Pringsheim, Physih der Sonne, p. 119 et seq. 



