S52 Mr. Joule on the Calorific Effects 



are not so much inferior to the experimental results of column 

 5 as they were in Table I. The principal reason of this 

 arises from the mixture of the constant effect of the battery 

 with the variable magneto-electrical current, as will be readily 

 seen on inspecting figs. 6 and 7» the former of which repre- 

 sents the currents in series No. 9 ; the latter, those in series 

 No. 10. The dotted rectangles abed, &c, represent the 

 constant effect of the battery of two cells, which is in one 

 instance diminished, in the other increased by the magneto- 

 electricity. 



; 1 Fig. 6. j ] 



^Ni 



Fig. 7. 



On comparing columns 6 and 8 with column 5, it is ma- 

 nifest that the law of the square of the electric current still 

 obtains, and is not affected either by the assistance or resist- 

 ance which the magneto-electricity presents to the voltaic 

 current. Now the increase or diminution of the chemical 

 effects occurring in the battery during a given time is propor- 

 tional to the magneto-electrical effect, and the heat evolved is 

 always proportional to the square of the current ; therefore 

 the heat due to a given chemical action is subject to an in- 

 crease or to a diminution directly proportional to the intensity 

 of the magneto- electricity assisting or opposing the voltaic 

 current. 



We have therefore in magneto-electricity an agent capable by 

 simple mechanical means of destroying or generating heat. In 

 a subsequent part of this paper I shall make an attempt to 

 connect heat with mechanical power in absolute numerical 

 relations. At present we shall turn to a question intimately 

 connected with the previous investigations ; and which indeed 

 has already been partly developed. 



