134 THOMSON ON CARNOT'S 



that heat is generated by the friction of fluids in 

 motion, seem to overturn the opinion commonly 

 held that heat cannot be generated, but only pro- 

 duced from a source, where it has previously ex- 

 isted either in a sensible or in a latent condition. 



In the present state of science, however, no opera- 

 tion is known by which heat can be absorbed into 

 a body without either elevating its temperature or 

 becoming latent, and producing some alteration in 

 its physical condition; and the fundamental axiom 

 adopted by Carnot may be considered as still the 

 most probable basis for an investigation of the mo- 

 tive power of heat; although this, and with it 

 every other branch of the theory of heat, may 

 ultimately require to be reconstructed upon another 

 foundation, when our experimental data are more 

 complete. On this understanding, and to avoid a 



temperature, and thus compensate for the heat evolved in 

 the conductor. I am not aware that any examination with 

 reference to the truth of this conjecture has been instituted ; 

 but, in the case where the inducing body is a pure electro- 

 magnet (without any iron), the experiments actually per- 

 formed by Mr. Joule render the conclusion probable that 

 the heat evolved in the wire of the electro-magnet is not 

 affected by the inductive action, otherwise than through 

 the reflected influence which increases the strength of its 

 own current. 



