LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



JUNE 1896. 



LII. Thermo-Electric Interpolation Formula. 

 By StLAs W. Holm an.* 



IN this paper are collected the several well-known types of 

 formulae for expressing the thermal electromotive force 

 of a couple as a function of the temperature of its junctions. 

 Two new formulae are also proposed. All then are tested 

 against the most reliable experimental data upon the subject, 

 and their relative merits discussed. 



The Existing Formula, 



Consider a simple closed electric circuit composed of two 

 different metals, each homogeneous in matter and temper, 

 the metals being in contact at two points. For simplicity, 

 assume the metals to be in the form of wires joined at their 

 ends. Let one junction be at a temperature of h°, the other 

 of c°, on the ordinary Centigrade scale. Let 2* £ be employed 

 as a suggestive symbol to denote the resultant electromotive 

 force in the circuit, induction being excluded from considera- 

 tion. Then % c e is a function of h and c which involves 

 constants dependent upon the nature of the metals, and which 

 may be represented by 



t)e=f{h,c). 

 The discovery of the natural expression for / (A, c) is not only 



* Fro ai an advance proof of the 'Proceeding of tho American 

 Academy/ vol. xxxr. (n. s. xxiii.) p. 193. Communicated by the Author. 

 Phil. Mag. S. 5. Vol. 41. No. 253. Jane 1896. 2 K 



