﻿of the Electron Theory of Matter. 611 



as before, maintained at V 2 . This will reduce the pressure 

 of the electrons from p x to pi and will change their potential 

 energy from eY x to eV 2 but will not affect their temperature 0. 

 The cycle consists in evaporating N electrons through the 

 potential screen. The work done is NR# and the heat 

 absorbed is, by virtue of (14), N[(<w - J) x + <V 2 - Y{) + R0]. 

 Next expand at 6 from p^° to p 2 . The work done and heat 

 absorbed are each equal to NR0 log {pi°/p 2 ) • Next condense 

 at V 2 and p 2 in the second body. The work done is — NR0 

 and the heat absorbed is — N[(g> — J) 2 + R0]. During the 

 flow along the wire connecting the conductors there is no 

 work done, but there is an absorption of heat NP# at the 

 junction, where P is the Peltier effect. The total amount of 

 work in this isothermal reversible cycle is NR0 log pi°/p 2 ; 

 so that p 1 °=p 2 . The total absorption of heat is 



L P2 J 



a,nd since (o i — co 02 -=e(Y 1 — Y 2 ) 



we have P<? = J 1 — J 2 , (39) 



The expression for the Thomson effect (specific heat of 

 •electricity) may be obtained by considering a cycle which 

 differs from the foregoing in that there is now only 

 one conductor but its ends are maintained at different 



temperatures. By applying the equation I -~ = to the 



same set of processes as were considered in the elementary 

 theory, we arrive at the equation 



c 6 ° 



*ijfl, Oo-J)i Oo-JV , ei V'-Yi ) 



1 dU+ ~~T W~ + e^ 



The dashed quantities refer to the temperature & and the 

 undashed to <9 , the notation being in fact the same as before. 

 From the conditions of equilibrium among the electrons in 

 the parts of the system which are at the same temperature 

 we have 



log/?! = lOg , log - ] g-(«-»o)/B*',J T L 



, , ?iiR6 , i r 



log^i = log — — -—log I e-(«-«o) R*o^ Tj 



'2 8 2 



