172 
Proceedings of the Royal Society of Edinburgh. [Sess. 
A similar equation is found for — log p B , and subtracting, 
oO 
dO 8 p A R0 2 
• ( 2 ) 
d 
To evaluate -y-(g A — <7 b) we apply the equation 
d6 
^± +c -h=h- t 
rt6 6’ 
in which c, h are the specific heats in the first and second phases, and so 
obtain 
^ a _ 2 a , h _ c 
de—6 +k A ’ 
h referring to the external ( i.e . chamber-) electron-vapour, and 
whence 
dg-B _ dB , 7 
bi 
^ qs) =^- (CA - CB) 
■ (3) 
Our equation for the temperature-coefficient of the E.M.F. thus becomes, 
on insertion of (2) and (3), 
djfi = B log - (c A - c B ) ; 
dv p A 
and from (1), R log ^ ~ ^ B , 
Pa V v 
dK_ 
dO ~ 
E _ ff a ~ g B _ #(c A ~ g B ) 
^ M 
0 
Lastly, writing q AB for ( q A — q B ), the latent heat per unit mass for the 
passage from A to B, we see that (i) E is the purely electrical energy- 
change, per unit charge, involved in the transference from A to B ; (ii) 
2^5-is the latent heat of change per unit charge ; and (iii) ^ is the 
/A fj. 
heat absorbed or liberated per unit charge on account of the change in 
specific heat of the electronic vapour. Hence the numerator in 
E - -{g AB + 0(c A - c B )} 
r 
accounts entirely for the heat absorbed or liberated at the junction by the 
