of Emission and Absorption Lives in a Gas- Spectrum. 289 



The displacement is exactly the same as that produced by 

 the same effect in the absorption spectrum (see the previous 

 section). 



I have applied the theory here developed to other cases o£ 

 emission spectra, including cases of the direct Zeeman effect. 

 The results obtained were merely an adaptation of those pre- 

 viously obtained for the absorption spectra, and I do not 

 consider it necessary to reproduce them here. 



III. Numerical. 



It might be as well to enter now into a comparison of the 

 results obtained with the experimental facts ; to show that 

 the effects here discussed have some connexion with the 

 actual ones. The comparison is, however, imperfect, as it is 

 not between results for the same substances. 



The numbers and results here quoted are derived from 

 papers by Natanson in the Cracow Bulletin, and by 

 Humphreys, Haschek and Mache in the ' Astrophysical 

 Journal.' Natanson has applied experimental results to 

 Lorentz's theory of absorption in a large number of cases 

 extending over several gases. He was thus enabled to cal- 

 culate the numerical values of the constants occurring in the 

 absorption formula for the gases considered. 



The displacement of the lines on our theory was given by 

 a change in frequency dn , where 







dn - 



ap 







and 





dn _ 



a /N* 2 \ 

 2n 2 V m )' 





Natanson 



Lises the notation 











A = 3ttc 



2 m 

 N?' 



X 



\q 



2-7TC 

 Wo 



and in this 



notation 













dn 



a 



37TC 2 \ 2 



4ttV " 



3a 



C57T 



1 



"D" 



Also 



d\ 



_dn 



n 



Sa 1 







Now Natanson has calculated D for several gases in a 

 Phil. Mag. S. 6. Vol. 24. No. 140. Aug. 1912. U 



