THEORY OF ELECTRODYNAMICAL ACTION. 97 



The deduction of such particular cases from the 

 theory, required, as may easily be imagined, some 

 complex calculations: but the deduction being satis- 

 factory, it will be seen that Ampere's theory con- 

 formed to that description which we have repeatedly 

 had to point out as the usual character of a true 

 and stable theory ; namely, that besides accounting 

 for the class of phenomena which suggested it, it 

 supplies an unforeseen explanation of other known 

 facts. For the mutual action of magnets, which 

 was supposed to be already reduced to a satisfactory 

 theoretical form by Coulomb, was not contemplated 

 by Ampere in the formation of his hypothesis ; 

 and the mutual action of voltaic currents, though 

 tried only in consequence of the suggestion of the 

 theory, was clearly a fact distinct from electromag- 

 netic action ; yet all these facts flowed alike from 

 the theory. And thus Ampere brought into view 

 a class of forces for which the term " electromag- 

 netic" was too limited, and which he designated 1 

 by the appropriate term electrodynamic ; distin- 

 guishing them by this expression, as the forces of 

 an electric current, from the statical effects of elec- 

 tricity which we had formerly to treat of. This 

 term has passed into common use among scientific 

 writers, and remains the record and stamp of the 

 success of the Amperian induction. 



The first promulgation of Ampere's views was 

 by a communication to the French Academy of 



1 Ann. ck Chim., torn. xx. p. 60 (1822). 

 VOL. III. 11 



