53 



continued ever since, getting an experiment on copper nearly every 

 week with more and more sensitive arrangements, and at last, in 

 two experiments, I have made out with certainty, that vitreous elec- 

 tricity carries heat with it in an unequally heated copper conductor. 



The third hypothesis is thus established : a most unexpected con- 

 clusion I am willing to confess. 



I intend to continue the research, and I hope not only to ascer- 

 tain the nature of the thermal effects in other metals, but to deter- 

 mine its amount in absolute measure in the most important cases, 

 and to find how it varies, if at all, with the temperature ; that is, to 

 determine the character (positive or negative) and the value of the 

 specific heat, varying or not with the temperature, of the unit of 

 current electricity in various metals. 



II. On the Law of Thermo-electric Force in an unequally heated 

 circuit of two Metals. 



A general relation between the specific heats of electricity in two 

 different metals, and the law of thermo-electric force, in a circuit 

 composed of them according to the temperatures of their junctions, 

 was established in the communication to the Royal Society of Edin- 

 burgh referred to above, and was expressed by an equation* which 

 may now be simplified by the thermometric assumption 



t =i; 

 V- 



(jti denoting Carnot's function, J Joule's equivalent, and t the tempe- 

 rature measured from an absolute zero, about 273 Cent, below the 

 freezing-point,) since this assumption defines a system of thermometry 

 in absolute measure, which the experimental researches recently made 

 by Mr. Joule and myself establish as not differing sensibly from the 

 scale of the air-thermometer between ordinary limits. The equa- 

 tion, when so modified, takes the following form : 



where & denotes the excess of the specific heat of electricity in the 

 metal through which the current goes from cold to hot above the 

 specific heat of the same electricity in the other metal, at the tem- 



* See Proceedings R.S.E. Dec. 1851, or Philosophical Magazine 1852. 



