PREFACE. 



The subject comprised under the title 

 of this monograph naturally divides 

 itself into the following sub- sections : 

 1. Alternators ; 2. Transformers ; 3' Mo- 

 tors ; 4. Meters ; 5. Mains ; and G. 

 Accessory apparatus for use in central 

 stations and on the premises of the per- 

 sons supplied with current from such 

 stations. The question of lamps does 

 not properly belong to the subject under 

 consideration, because glow lamps are 

 equally suitable to be fed by alternating 

 and direct currents, and the alterations 

 required to make arc lamps work with 

 alternating currents are easily applied, 

 and present no special interest. In the 

 present volume, the author deals more 

 especially with the first three subjects, 

 namely, alternators, transformers, and 

 motors. 



