Thermoelectric Circuit of Three Metals. 



639 



§ 4. Results. 



The resnlts of the experiments are given in the following 

 tables. Tables I A. and I B. give the results of final experi- 

 ments made with the thicker (soft) wires of the three metals; 

 the results of preliminary trials with these wires are omitted. 

 Tables II A. and II b. give the results of all the experiments 

 made with the thinner (hard) wires. In view of the possibility 

 of an alteration in the thermoelectric force of a given 

 junction*, it may be well to state that the observations 

 recorded in Table II B. were made before those recorded in 

 Table II A. Owing to the removal of the Physical Institute 

 to a new building the writer was unfortunately unable to 

 carry out his intention of making further experiments with a 

 view to the elucidation of this point. He is however 

 distinctly of opinion that the thermoelectric " constants " are 

 (within the range 0° C. to 100° C.) really constant, and that 

 anomalies such as those recorded by Steele (loc. cit.) are due 

 to difficulties of observation. The agreement between ob- 

 served and calculated results is much better in Table II A. 

 than in Table IIb. This is probably due, not to any alter- 

 ation in the junctions, but chiefly to the better avoidance of 

 the error (previously spoken of) due to the mercury key. 



Table I a.— Soft Wires. 

 Electromotive force in microvolts of pairs of metals. 





E.M.F. observed. 



E.M.F. 

 calculated *. 



Exp. 1. 



Exp. 2. 



Mean. 



Copper-Iron, 6-20 



0-60 



0-80 



Iron-G.S., 0-20 



0-60 



0-80 



G.S.-Copper, 0-20 



0-60 



0-80 



231-5 



665-5 

 864 



- 456 

 -1384 

 -1851 



223 



712 

 986 



234 



670-3 

 865 



226 

 718 

 985 



233 



668 

 864-5 



224-5 

 715 



985-5 



234-2 

 666-4 

 864-5 



- 457-2 

 -1382-8 

 - 1851-0 



223-6 

 716-3 



985-4 



Copper-Iron a= + 12'01, /;=--Q301. 



Iron-G.S a= -22-77, b= -"0092. 



G.S.-Copper «= + 10-80, 5= 4- -03795. 



* Method of least squares. 



* See for instance Wiedemann, Elektricitat, ed. 2, art. 337 j also 

 W. H. Steele, Phil. Mag. vol. xxxvii. p. 221 (1894). 



