Thermoelectric Circuit of Three Metals. G33 



The value of E is represented by the area enclosed by the 

 thickened lines. Equation (6) can be written down from 

 inspection of the diagram. 



Whatever views may be held as to the ultimate causes of 

 thermoelectric phenomena, the experimental evidence for the 

 assumptions on which equations (1) and (2) depend is too 

 strong to be called in question. On the other hand, the 

 researches of Tart*, Dewar and Fleming f, Holborn and 

 Day t, and others show that equations (4) do not hold 

 for all metals at all temperatures. In the present paper, the 

 writer confines himself to the application of equations (4), (5), 

 and (6) to the experimental results ; and it will be seen 

 that, within the limits of experimental error, these equations 

 are confirmed in the cases examined. 



The circuits to which the measurements refer are formed 

 from the metals German silver (A), copper (B). and iron (C), 

 and the limits of temperature are 0° C. and 80° C. 



§ 2. Standards. 



The ultimate standard oO electromotive force for the present 

 measurements was a Weston cell (No. 445) made by the 

 European Weston Company, Berlin ; the electromotive force 

 was taken at its certificate value, 1'018 9 volts (19°). Four 

 Weston cells were made in accordance with the instructions 

 of W. Jaeger §, except that, following the later practice of the 

 Reichsanstalt, the cadmium amalgam was composed of 

 12 parts cadmium and 88 parts mercury. Measurements 

 of the electromotive force of these cells, (a) soon after 

 construction, (6) after completion of the thermoelectric 

 experiments, gave the values shown in the following 

 table : — 



(«) (b) 



25th .b'eb. loth April. 



Cell No. 1 1-0194 1-01935 



„ 2 1-0193 1-0193 



„ 3 1-0194 1-0194 



„ 4 1-01945 1-0194 



Cells No. 1, 2, 4 were combined in series, the total electro- 

 motive force being assumed 3'0582 volts ; a temperature 

 correction was unnecessary. Cell No. 3 was used to produce 

 an occasional current through 100,019 ohms ; wires from 



* Trans. R. S. E. vol. xxvii. p. 125 (1876). 

 t Phil. Mag. vol. xl. p. 95 (1895). 

 X Berl. . Sitzungsber. vol. ii. p. 691 (1899). 

 § Elektrotechn. Zeitschr. 1897. 



Phil. Mag. S. 6. Yol, 10. No. 60. Dec. 1905, 2 X 



