494 Dr. S. R. Milner on the Internal 



never remove the turning value, although it might dis- 

 place its incidence. Curtis found the Pitz formula 

 v = £(i — lf r (m+/jb)*% /x = 7-4xl0 -6 , to best fit his obser- 

 vations, but a simple rearrangement throws this into the 

 form 



N = 



-N-^+A), 

 m A \4t my 



whence we see that the correction is a good deal smaller 

 than the relativity one and vanishes so rapidly as not to 

 affect the terms where the difficulty occurs. The fainter 

 unresolved lines in both Helium series, as shown in Table I., 

 had to be discarded for the same reason. 



These wave-lengths being presumably between I and II 

 are too small, and we have an additional quasi-relativity 

 correction to subtract from N. Paschen estimates the 

 correction at £(II — I) ='122 em." 1 . Furthermore, the 

 bordering lines on the long-wave side shift the observations 

 that way. Paschen adds on a correction of J of the 

 " spread " of the first component I. Both corrections 

 are tabulated in our scale. The resultant values of N 

 after the three corrections are not constant. Paschen's 

 values would seem to have been over-corrected. Taking 

 J (I I — I) instead of J, we get the last N'ae columns, where 

 his first three N's have become constant. It seems safe 

 to adopt 



Nile = 109677-9. 



Paschen gave (older value for refraction) 109677*691 +0*6. 

 Curtis gives as a mean of the various formulae tried 109678'3. 



It is evident that we need interferometer measurements on 

 the earlier hydrogen lines. 



London, May 1920. 



LV. The Internal Energy of the Lorentz Electron. 

 By S. P. Milner, D.Sc* 



THE Lorentz electron, as has long been recognized, is 

 not a purely electromagnetic system. In order to 

 make it a system amenable to the laws of mechanics it is 

 necessary to ascribe to it a certain amount of energy in 

 addition to that which is accounted for by the electric and 

 magnetic forces of the field. This energy, apparently non- 

 electromagnetic in character, is assumed to be located in 



* Communicated by the Author. 



