produced hy changes of Temperature. 



315 



Hence it appears that the intensity of the electric current 

 diminishes proportionally to the diminution of tempera- 

 ture. 



An important question here presents itself. How comes it, 

 if there really exists such intimate relations between the elec- 

 trical effects of contact and the chemical forces, that the incre- 

 ments of these effects, in consequence of the rise of tempera- 

 ture, are not more rapid than experiment shows them to be, 

 and that the electrical actions are not more intense at the mo- 

 ment when the chemical forces increase with so much rapidity ? 

 It is difficult to reply to this question. Besides, how happens 

 it that iron, in its contact with the other metals, gives electrical 

 effects which change their sign with a rise of temperature? And 

 perhaps iron is not the only metal which enjoys that property. 

 By forming circuits with different metals, so as to have in each 

 of them two different metals, and raising the temperature of 

 one of the joints of junction, we find the following electri- 

 cal series, in which each metal is negative in relation to those 

 which Jbllow it, and positive in relation to those which precede 



it. 



Bismuth, 



Platina, 



Mercury, 



Lead, 



Tin, 



Gold, 



Silver, 



Copper, 



Zinc, 



Iron, 



Antimony. 



From these experiments we conclude, that zinc and copper 

 in contact, when they make part of a circuit, give rise to an 

 electric current, tin- less intense as the temperature is elevated. 

 Other metals enjoy equally the property of producing electri- 



