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will be found sufficient for the purpose of 

 designing alternators, or for the deter- 

 mination of the behavior of any given 

 machine of this class, except in one par- 

 ticular, viz., its greater or lesser liability 

 to heating. In any dynamo machine 

 there are two causes for heating, in 

 addition to purely mechanical friction. 

 These are the resistance of the conduct- 

 ors, and the change of magnetization of 

 the iron parts of the machine. As re- 

 gards the first cause, the result of which 

 may be comprised under the term "cop- 

 per heat," it is so well understood that 

 it need not in this place be specially con- 

 sidered. One circumstance in connec- 

 tion with this subject should, however, 

 be mentioned. The liability to the gen- 

 erations of eddy currents in the armature 

 conductor is much greater with alter- 

 nators than with continuous-current dyna- 

 mos, and in alternators it varies with 

 the construction of the armature to a 

 greater degree. When the armature 

 contains no iron, the heating from 

 eddy currents is much greater than 



