204 PROCEEDINGS OP THE AMERICAN ACADEMY 



The results of our work can be stated as follows : — 



1. The heat developed by reversals of magnetization is probably 

 due to induction currents, and not to molecular vibrations ; for con- 

 siderable changes in the molecular structure of different specimens 

 of iron and steel fail to show differences in the amount of heat 

 developed. 



2. The heating of iron cores of electro-magnets, which are submit- 

 ted to alternating currents, is confined to the surface until conduction 

 equalizes the heat of the cores. 



3. The musical note emitted by the core is the note of the coil, due 

 to the number of reversals of the machine, and is merely strengthened 

 by the metallic core of the electro-magnet. This note should not, 

 therefore, be used as an argument in favor of molecular vibrations of 

 magnetic particles. 



4. Experiments on demagnetization confirm what has long been 

 known in regard to the effect of vibrations and shocks upon the mag- 

 netic condition of iron and steel. They do not invalidate our results 

 upon the heat produced by reversals of magnetization ; for a very 

 slight change in position of the molecules might affect the magnetism 

 of a bar, and yet be insufficient to produce the great heating observed 

 in the armatures of dynamo-electric machines. 



