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CARNEGIE INSTITUTION OF WASHINGTON. 



function of temperature and pressure, the proportion increasing with 

 rise of temperature and decrease of pressure. For elements whose 

 ionization potentials are known, he deduces the state of ionization in 

 the solar atmosphere for assumed values of the temperature and pres- 

 sure. He suggests that over the faculas, which are considered to be 

 regions at temperatures higher than that of the photosphere, the spec- 

 trum, owing to the increased temperature, should become similar to 

 the spectrum of a star at a temperature higher than that of the sun. 

 This would be shown by an increase in the intensity of the enhanced 

 lines, proportional to the increase in the number of ionized nuclei. 

 Some preliminary spectrograms of faculae obtained by Mr. St. 

 John show changes in the intensity of the enhanced lines in agreement 

 with these deductions, the spectral typ'e changing in the direction 

 GO to F, as indicated by the accompanying table. 



Behavior over faculae. 



It is evident that in ionization phenomena we have a new means of 

 attacking solar problems. On the other hand, solar observations will 

 supplement laboratory methods. Little is known of the ionizing poten- 

 ials of elements outside the first and second columns of the periodic 

 table. For other elements, such as iron and titanium, a promising 

 approach to the question is through their behavior in regions of widely 

 different solar temperatures and pressure as compared with that of ele- 



