652 Mr. Shizuwo Sario on the Thermodynamical 



If p e denotes the electric charge per unit volume, then 



so that (6) may be written 



T= J(^I£~^^ • • • ■ (8) 



since D vanishes at P / and P". 



The phenomena of pyro-electricity teach us that E does 

 not vanish at the same time as D in crystals having polar 

 axes. It seems to me that it is quite natural to suppose 

 that at any point P within the transition layer the fluid may 

 be considered just like a crystal having a polar axis, normal 

 to the series o£ surfaces a = const., i. e. the electric force 



?)F 



^-y contains <r x and does not vanish when D = 0. If this is 



° D dF 



really the case, both o\ r ^ — and ^ e Pe contain terms depending 



upon the distribution of electricity in the layer of transition, 

 so that it is impossible to conceive that — ( yjr e p c dx would be 

 the term arising from the double sheet of electricity in the 

 layer. 



If we assume that F is independent of <r T , then (6) would 

 become 



T=- JEDda?, 



where E vanishes simultaneously with D. Since we expect 

 that E and D have the same sign at P, this value of T would 

 become negative, i. e. the mechanical equilibrium would be 

 labile. Hence if we assume that F is independent of o>, then 

 the fluid cannot exist in two phases in contact. Discussing 

 this from another point of view : — 



In the following, I assume that the temperature is given, 

 and neglect the effect of gravity altogether. Let the 

 quantities referring to the point P' be accented once, and 

 those corresponding to P" twice. 



Now, assuming that F does not contain o\ r , then from 

 (1), (3), (4) we get 



^ +«C?i'i-^- 15', [ki, ».-..«], • 0) 



Sv«mj^~0, (10) 



dpi 



- F+ v|=-J" + v| cm 



