of the Hall Effect and Allied Phenomena. 

 or substituting the value of E z found above, 



3 4 



541 



W, 



^ 9 s ( 



(fi-MM) 



(•♦9JJ 



The coefficient of thermal conductivity is thus altered in the 

 ratio 



A7 



y 



vH\ 



i-i 



K) 



r ( 3+ 9 

 G-5)<i 



2 ^\ 



2 + 



This effect always has a positive sign whatever the value of *. 

 It shows that the magnetic field increases the thermal con- 

 ductivity for transverse currents. There appears to be very 

 little evidence of an effect of this kind ; the only metal for 

 which the effect is known with certainty is bismuth, and 

 here the conductivity is decreased instead of increased as the 

 theory predicts : but see below, § 9. 



7. The von Ettingshausen Effect. 



In his second series of experiments von Ettingshausen 

 measures, with the same arrangement as in Hall's experi- 

 ments, the transverse difference of temperature which it is 

 necessary to create to balance the transverse flux of heat 

 which exists in the original experiments. There is in these 

 experiments no flux of heat in the direction of the r-axis if 

 the main current and magnetic force are disposed as in the 

 previous paragraphs. A definite temperature gradient is, 

 however, established in this direction. The condition for no 



