of Voltaic Cooling and Heating. 267 



quantity of heat cs u will be absorbed, which is greater than that 

 produced by the current. The difference between the two, or e's ll} 

 must therefore be produced in the other electromotor, so that the 

 algebraic sum of that which is produced and of that which dis- 

 appears may be equal to zero. It therefore follows that if a 

 current traverses an electromotor in the opposite direction to the 

 current which is produced by it, heat is developed in this elec- 

 tromotor proportional to the product of the electromotive force 

 into the intensity. Hence is obtained the final result : — If a 

 voltaic current traverses an electromotor in the same direction as 

 the current which is produced by the electromotor,, absorption of 

 heat ensues ; if the current is in the opposite direction, heat is pro- 

 duced ; the quantity of heat which is absorbed in the first case and 

 produced in the latter is proportional to the intensity of the current 

 multiplied by the electromotive force at the place where the change 

 of heat ensues. 



If two heterogeneous metals are brought into contact with one 

 another, an electromotive force ensues at the point of contact. 

 If a voltaic current traverses the place of contact, there must 

 either be absorption or production of heat. Here, then, we have 

 the cause of Peltier's phenomena. The quantities of heat ab- 

 sorbed in the one and produced in the other case are propor- 

 tional to the product of the intensity into the electromotive 

 force. Hence, if with different intensities experiments are made 

 with the same two metals, the differences in temperature must 

 be proportional to the intensities, as has already been experi- 

 mentally shown. But if, retaining the same intensity of the 

 current, experiments are made with different metals, the quanti- 

 ties of heat must be proportional to the electromotive forces. 

 Hence by measuring the quantities of heat we should be in a 

 posit on to arrange the metals in the actual electromotive series. 

 But this series must be quite different from that obtained when 

 the metals are arranged according to the observed differences in 

 temperature; for these differences, besides depending on the 

 quantities of heat absorbed and produced, depend also on the 

 thermal capacities of the metals, on the greater or less degree of 

 cooling during the experiment, and so forth. All experimenters 

 who have worked at this subject have found the difference in 

 temperature to be greatest at the contact of bismuth and anti- 

 mony; but this by no means proves that the contact between these 

 metals produces the greatest electromotive force. The difference 

 in temperature must, as has been said, depend essentially on the 

 capacity for heat. Comparing the thermal capacities for equal 

 volumes of the metals with which Peltier's experiments were 

 made, it is found that bismuth has the least capacity of all me- 

 tals, and next to it antimony. Hence, when the current passes, 



T2 



