OF ARTS AND SCIENCES. 235 



No. XXII. — ILLUSTRATION OF THE CONSERVATION 

 OF ENERGY. 



By Jonx Trowbridge. 



Presented Dec. 10, 1879. 



In the Proceedings of the American Academy, Dec. 11, 1878, can 

 he found a preliminary paper by Mr. TV. N. Hill and myself upon the 

 heat developed by the rapid magnetization and demagnetization of 

 iron. The research is still in progress, and we hope to determine how 

 much of the work employed in driving dynamo-electric machines is 

 consumed in heating the iron cores of the generator of electrical cur- 

 rents, and whether this loss of work should turn our attention to forms 

 of generators in which this loss is obviated. It may well be that this 

 loss is not sufficient to counterbalance decided advantages in the pres- 

 ent form of such machines. 



From my work in this research, I draw the following illustration of 

 the conservation of energy. 



Let an induction coil be set in action. In the circuit of the second- 

 ary coil place another coil of fine wire. Adjust the terminals of the 

 induction coil so that the spark just passes : then place a core of iron 

 or a bundle of iron wire in the coil which has been included in the 

 secondary circuit. The spark instantly ceases to jump. A portion of 

 the energy of the current in the secondary circuit has been consumed 

 in magnetizing and demagnetizing the iron introduced into the addi- 

 tional coil. The work done in this way is capable of being measured. 



It is also evident, that, when a number of telephones are in the sjune 

 circuit, a part of the energy of the human voice is consumed at 

 each telephone in heating the magnetic cores. 



