60 HEAT GENERATED OR TRANSFERRED. 



the circuit of the armature of the machine was generated 

 by the current, or merely transferred from the coils in which 

 the magneto electricity was induced, the coils themselves 

 becoming cold. Transference of heat played such an 

 important part in the attempts which had been made to 

 reconcile the dogma that caloric was a material with 

 observed phenomenon, that there would have been nothing 

 remarkable at that time in Joule, although for the moment 

 carried forward by his own experiments and physical in- 

 stincts, being brought up again by the physical casuistry of" 

 his time. This, however, does not appear to have been the 

 case, at least not altogether. It is his own discovery re- 

 capitulated, in his sixth observation, that the heat evolved 

 in the circuit of the voltaic battery is the definite chemical 

 heat due to the union of the elements in the cells transferred 

 to other parts of his circuit, which suggests, by analogy,, 

 that the heat developed in one part of the circuit of the 

 magnetic engine may be merely transferred from another. 



There is more interest in this stage of Joule's work than 

 is apt to appear on the surface. So far he has shown 

 no indication of holding any view heterodox to those 

 generally accepted at the time respecting heat. He has 

 shown that the heat developed in the voltaic circuit exactly 

 corresponds with the heat developed by the combustion 

 of the same elements, and offered this as proof that the 

 heat of combustion is developed by electricity. But in this 

 there is nothing at variance with the then accepted hypothesis 

 that the heat developed by the union of the elements,, 

 however brought about, was latent in the elements before 

 union, which hypothesis, therefore, so far explains the source 

 of the heat in the voltaic circuit. And then he had established 

 facts which " might seem to prove that arrangement only,. 



