﻿28 On the Electromotive Force on the Contact of different Metals. 



be again investigated. This circumstance might possibly give 

 rise to an error ; and hence the experiments with bismuth-copper 

 were repeated. 



Experiment 19. — A new bismuth-bar, somewhat thicker than 

 the last, but from the same piece of bismuth, was soldered to the 

 copper, on which the observations were made in the usual 

 manner. 



There were thus obtained : — 



Deflections. 

 81-0 

 730 

 77-0 

 78-5 



Mean . . 77*4 

 Intensity of the current = tg. 29°. 



If from this the deflection be calculated for an angle of 45°, 

 it is found to be = 139*6, thus almost equal to the number pre- 

 viously obtained (141*3). 



The magnitude of the thermoelectric current with the new bis- 

 muth-copper combination was next determined, as well as, for 

 comparison, those with three of the combinations previously 

 mentioned. So great a resistance from the rheostat was now 

 interposed in the circuit, that the resistance could in all the 

 experiments be regarded as quite equal. It is only necessary to 

 adduce the mean numbers suitably reduced in order to facilitate 

 inspection and comparison with the preceding. In this manner 

 it was found that the thermoelectric currents for these combina- 

 tions were as follows : — 



Bismuth-copper \, . . 78*47 



Argentan-copper . • . 24*17 



Platinum-copper . . ♦ 8*30 



Copper-iron . . # . 24*93 



These numbers, within the limits of errors of observation, are 

 equal to those previously obtained, except that for bismuth-cop- 

 per, with which combination the deflection was smaller than be- 

 fore. This is doubtless due to the new bismuth-bar being some- 

 what different from the first. Yet it is seen that the exception 

 which the combination bismuth-copper makes does not depend 

 upon a faulty determination. 



According to Seebeck, the various metals have the following 

 order in the electric-tension series : — silver, platinum, copper, 

 iron, bismuth, and zinc, in which each preceding in contact with 

 the succeeding is electronegative. Although different observers 

 have found the order different, partly in consequence of the 



