Polarization and Magnetization Electrons. 411 



§ 6. The interpretation of the first variation. 



I£ the negative charge of an electron, the elementary 

 charge, be denoted by e, the current carried by the stream of 

 the positive nuclei will have the components 



— eNw a , 



and the stream of accompanying electrons will carry a 

 current 



*Nie« + e8Nw a -f ie8 2 Nw a , 



the resultant current from the charges bound in the neutral 

 atoms amounting to 



eSSvP + te&Sui*'. 



Now let us consider the first part, originating from the 

 first variation. It contains what was formerly called the 

 contribution from the polarization-electrons. We know by 

 formula (3) that 



e8R w a = 2(6) -$- h -\ ei^Rufi — er 6 Nwj« > . 



We shall consider the tensor : 



pa& — er cq$ w b _ er b T$w a . 

 This is the same as 



= ^Sep a w b —^ephc a , 



k(7) 



where p a is the principal term in the expression (6) giving 

 the simultaneous displacements. Introducing for the prin- 

 cipal part of the polarization the three-dimensional vector 



we recognize in the (14)-, (24)-, (34)-components of the 

 tensor Y ah components of polarization, and in the (12)-, (23)-, 

 (ol)-components the components of the well-known Rontgen- 

 vector which is the three-dimensional vector-product of the 

 material velocity w into the polarization. Collecting the 

 components of T ab in the scheme 



[P.W] Z -[P.w]y Vx 



__, - -LP-w], [p.w] x p 



[p- w ] y -Lp- w 1x Pc' 



