APPROACHES GENERALIZATION. 57 



realized the equivalence of the mechanical and heating 

 powers of an electric current, but that he had already 

 realized the probable equivalence of the mechanical and 

 heat effects. Nor does his sixth observation contradict 

 this conclusion. In this, he says : — 



" Electricity may be regarded as the grand agent for 

 carrying, arranging, and converting chemical heat," and 

 illustrates this by referring to the definite amounts of heat 

 which would otherwise be developed in the cells of the 

 battery, which are, by the current, transferred by the 

 conductors and developed in a decomposing cell, or in a 

 resistance coil. 



In his seventh observation, however, he reasserted his 

 opinion that he has "put the beautiful theory of 

 chemical heat, first suggested by Davy and Berzelius,, 

 beyond all question," showing that he had not yet realized 

 the primary character of the relation between heat and 

 mechanical effect, which might be deduced from the 

 results he already had obtained, and which he was then on the 

 verge of discovering. Nor is this all. So far throughout 

 his work he has given no hint that he has ever considered 

 the character of heat, whether a "substance" or a mechanical 

 phenomenon, neither has he, in the least, described the 

 mechanical significance of "work." Of course, he might have 

 considered them all the same ; but the proof that he had 

 not done so is furnished in a note he added to this 

 paper on February 20, 1844, after his discovery was 

 complete. 



That the three fundamental quantities, work, heat, and 

 electricity, with which Joule had been occupied all this 

 time should have been accepted by him as having a natural 

 right to exist without further question as to their origin, 



