62 DETECTS THE EVOLUTION OF HEAT. 



provided effectually against its interference with the sub- 

 sequent results by alternating the experiments with others 

 made under the same circumstances, except as regards the 

 communication of the battery with the stationary magnets 

 which was in these instances broken." 



The result of these alternate experiments, was that with 

 the magnets excited, the temperature of the water surround- 

 ing the moving electro-magnet rose one-twentieth of a 

 degree Fahrenheit in 15 minutes, while with the contact 

 broken, it fell by the same amount, giving him one-tenth of 

 a degree Fahrenheit rise in temperature, as the heating 

 effect induced in the revolving magnet and circuit by the 

 stationary magnets. 



" Having thus detected the evolution of heat from the 

 coil of the magneto-electrical apparatus, my next business 

 was to confirm the fact by exposing the revolving electro- 

 magnet to more powerful magnetic influences." 



This he does, using stationary electro-magnets of 

 different power, also stationary steel magnets ; he thus 

 obtains results ranging from one-tenth degree Fahrenheit 

 to two degrees and a half. Having thus proved that heat 

 is generated by the magneto-electric current, he puts a finish 

 to this research, first by determining the heat evolved in the 

 iron core when revolving without its coil between the 

 poles of the electro -magnet ; and substracting this obtains 

 the relation between the heat generated in the coil of his 

 revolving magnet and the product of the square of the 

 current, multiplied by the resistance of the coil, so as to see 

 how far it corresponds with the heat that would be 

 generated by a voltaic current. Whence he finds, 

 making allowance for the intermittent character of the 

 magneto-electric current, " That the heat evolved by the coil 



