﻿614 Prof. 0. W. Richardson : Some Applications 



The foregoing formulae are, naturally, consistent with the 

 results of Kelvin's theory of thermoelectric phenomena. 

 The more general theory does not make any vital change in 

 the conclusions about contact electromotive force to which 

 the simple theory led us. 



As regards the relation between thermoelectric effects and 

 electrical conductivity, the natural assumption to make would 

 be, that whereas both the electrons which execute closed, and 

 those which execute open, orbits play a part in thermoelectric 

 phenomena, conductivity is only concerned with those which 

 execute open orbits. 



§ 6. Polarization Electrons and Galvanomagnetic 

 Phenomena. 



A point which deserves mentioning is the part possibly 

 played by polarization electrons in metallic conduction. It is 

 likely enough that in the interior of the metal there are a 

 number of electrons which behave in a similar manner to those 

 in a dielectric. In that case there will be some regions in the 

 interior where the part of the electric intensity which reverses 

 icith the external electromotive force will be greater and others 

 where it will be less than the average. It is even likely 

 enough that the sign of the electric intensity will be reversed 

 in some parts. Such a state of things might make a good 

 deal of difference in the electrical conductivity and also 

 in the magnitude of galvanomagnetic effects. Whether they 

 would be important or not would depend on the strength of 

 the polarization and the ratio of the linear scale of its parts 

 to the free path of an electron. 



As an extreme illustration we may take the mean free path 

 to be small compared with the scale of the polarization. Let 

 us suppose that the structure of the medium is so simple that 

 we may divide it up into two classes of regions, A and B, in 

 one of which (A) the electric intensity is Xj and in the 

 other (B) it is X 2 = «X 1 . Let n x and n 2 be the average 

 number of free electrons per unit volume, T x and T 2 their 

 mean free times, BT ± and 6T 2 the alterations of T x and T 2 

 produced by a magnetic field, S 2 and S 2 the average areas of 

 cross-section per unit area of an intersecting plane, and a 1 

 and a 2 the average lengths per unit length cut off a line by 

 the tw r o classes of regions. In each case the suffixes refer to 

 the corresponding class of region. The simple type of 

 electron theory, which assumes all the electrons to have the 

 same velocity of agitation and all those of the same class to 



