626 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



by the magnetic action through a small angle in the direction of flow 

 of the Amperian magnetizing current. 



The letter commonly used for the Hall effect coefficient is ^ ; we 

 shall use also ^T^ in the same sense, T indicating transverse, the 

 initial e indicating that the longitudinal flow is electrical, the final e 

 indicating that the transverse flow is electrical. If we let 



Figure 1. 



Figure 2. 



C = the longitudinal current, in absolute units, 

 H= '' intensity of the field " 

 AP' = " diff". of pot. set up between the arms, 

 w = " width of the plate in cm., 

 t = " thickness of the plate in cm., 



■we have by definition 



',Te (or R) = 



AP' 



w 



wt^ CH' 



(1) 



Ettingshausen Effect. — In Figure 2, with the longitudinal electrical 

 current EE and the magnetic field just as in Figure 1, we take note 

 of a transverse difference of temperature, A^', established by magnetic 

 action. This is the Ettingshausen effect. A^', as here represented, is 

 in such a direction that a transverse current of heat would flow in the 

 same direction as the transverse electrical current of Figure 1. In 

 this case the Ettingshausen effect, like the Hall effect of Figure 1, is 

 said to be positive. 



Zahn uses P for the Ettingshausen coefficient. We shall use also, 

 in the same sense, gT^, the T, as before, standing for transverse, the e 

 for electrical, longitudinal, the h for thermal, transverse. We have by 

 definition 



,Ti, (or P) = —H— -^.pfj. 



^ w wt Cn 



(2) 



