﻿on the Contact of different Metals. 



27 



23-18 



8-23 



0-90 



0-63 

 24-93 



are therefore in the 



If the foregoing observations be calculated for a difference of 

 temperature of 10° and a conductivity = 100, we obtain for 



Bismuth-copper the deflection . . 92*27 



Argentan-copper 



Platinum- copper 



Zinc-copper 



Silver-copper 



Copper-iron 



In the thermoelectric series the metals 

 following order : — bismuth, argentan, platinum, zinc, silver, cop- 

 per, and iron. We see from this that the order in the series, which 

 is determined by the heat absorbed or produced on the current 

 passing through the place of contact, is the same as that which 

 is conditioned by the thermoelectric properties of the same me- 

 tals. In the combinations zinc-copper and silver-copper the 

 quantities of heat were so small that they could not be measured ; 

 but we also find that in the thermoelectric series zinc and silver 

 are very near copper, and form with it a very inconsiderable 

 thermoelectric force. In order to compare with one another the 

 numbers obtained, they can be reduced so as to be equivalent for 

 one of these combinations — for example, for copper-iron. We 

 thus obtain the following Table of comparison : — 



Thermoelectric Electromotive 



Bismuth-copper . 



series. 

 . 92-27 



series. 

 197-6 



Argentan-copper . 



, . 23-18 



21-77 



Platinum-coper 



. 8-23 



10-30 



Zinc-copper . . 



. 0-90 





Silver-copper . . 



. . 0-63 





Copper-iron . . 



. 24-93 



24-93 



In the combinations argentan-copper and platinum-copper the 

 numbers in the two series are almost equal, from which it might be 

 assumed that the electromotive and thermoelectric forces are pro- 

 portional to one another. Yet this is most decisively refuted by 

 the combination bismuth-copper. In order to be quite convinced 

 that this latter combination did not depend upon a faulty mea- 

 surement of the thermoelectric current, the determination was re- 

 peated, by which a deflection of 88*7 divisions was obtained when 

 the difference in temperature of the two solderings was 10°, and 

 the conducting-power was 100. The result was therefore about 

 the same as before. Yet there was a reason for doubtiug that some 

 error might have crept in in the determination of the numbers for 

 bismuth-copper • for when this pair of wires was removed from the 

 air-thermometer, the bismuth broke near the place of soldering, 

 which necessitated a new soldering before this combination could 



