PREFACE 



AT THE present time the study of Electricity and Elec- 

 trical Machinery occupies a very important place in the 

 curricula of industrial schools, technical high schools and 

 engineering schools. The application of electrical power 

 is becoming so general that a knowledge of the simple 

 principles and operating characteristics of the different 

 types of electrical machinery is of great value to the man 

 engaged in technical work of any kind. 



This text was written especially for the use of students 

 in technical high schools and similar institutions, but it is 

 believed that it will be of value also for certain courses 

 in engineering schools. Many of the students in engineer- 

 ing schools do not have the time for an exhaustive study of 

 the subject of Electrical Machinery, but every engineering 

 graduate should have some knowledge of the different kinds 

 of generators and motors in every day use. To such non- 

 electrical students the text should prove helpful. 



In the preparation of this book the author has kept in 

 mind the importance of simple, non-mathematical, explana- 

 tions of the behavior of the various machines. A mathe- 

 matical treatment of the subject has been introduced only 

 when necessary; even then a rudimentary knowledge of 

 mathematics only is required for a clear understanding of 

 the subject matter. 



I wish to express my appreciation of the courtesy the 

 various electrical manufacturing companies have shown in 

 furnishing me with the cuts used in the book. 



S. H. M. 



COLUMBIA UNIVERSITY, 

 January, 1914. 



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