of the Hall Effect and Allied Phenomena. 543 



The importance of this result is again the difference of 

 sign which may occur with the different values of s. This 

 was, I believe, first pointed out by Dr. Bohr, whose result 

 agrees with that here determined. Now it appears as a 

 matter of actual experience that it is just this effect, and the 

 one discussed in the previous paragraph (§ 6), whose signs 

 do not agree with those experimentally determined unless 

 s<4, a fact which provides important evidence for the form 

 of the law of interaction between the electrons and molecules, 

 as Bohr points out. Even for the cases in which all the 

 signs are reversed it still seems necessary to assume that 

 $<4 in order to obtain consistency in the relative signs of 

 the various phenomena. This fact is of course in full 

 accordance with the other branches of this theory where 

 similar requirements are necessitated by the facts of 

 experience. 



It seems very necessary to emphasize this important 

 point, as it appears to have been overlooked in subsequent 

 discussions bearing on the experimental work in this branch 

 of the subject *. 



8. The Righi Leduc Effect. 

 In these experiments the transverse force tending to 

 deflect the current of heat in Nernst's experiments is balanced 

 by a transverse temperature gradient. In such a case there 

 is no transverse flow of heat, so that 



_ el m ql~JR j T \i + V ( 2geE, 1 BAN r (l + l) l 5 g [ 



mc |r(2 + -V m A *y' r(2 + -) ? M' 



and there is also no flow of electricity in the'same. direction, 

 so that 



2qeE s 1 3A + / ' , 2\l-dq 



7)1 



M) 



A ~dz \ sj q ~dz 



= g/„g* ^H J r U + ~s) / 2qeE y 1 3A\ T (2 + ~sh 'dq [ 



mc [t{2 + ^ m A ^ r(! + ?) ? ^J 



* See for example J. Kcenigsberger u. C. Gottstein, Physikalische 

 Zeitschrift, xiv. (1913) p. 232, where an excellent summary of certain 

 tentative suggestions applied to this theory is given. 



