OF ARTS AND SCIENCES. 41 



The second law of thermodynamics gives : — 



Differentiate (8) 



, o-j — 0-2 d /7r\ 



•'• 6 ~'~ dd\e) 



performing the differentiation 



from (rj). 



If, as Tait supposes, a- is proijortional to the first power of the abso- 

 lute temperature, a = k6 equation (iv) becomes : — 



e = — [k6' + k'e + Z:"] 



.*. the thermo-electric curve is a parabola. 



The basis of all the preceding is taken from the British Encyclopa?dia. 

 Maxwell's demonstration is essentially the same. (§§ 249-251, Vol. T., 

 Maxwell's Electricity and Magnetism.) 



When no current was passing from an external battery eq. (2) 

 became 



Let 



TT 7^=6 .•. I = ^ 



K 



