Excerpt from Principles of Dynamo-Electric Machines: And Practical Directions for Designing and Constructing Dynamos With an Appendix Containing Several Articles on Allied Subjects and a Table of Equivalents of Units of Measurement Engineers and machinists practically engaged in design ing, constructing and repairing dynamos, as well as amateurs, students of electrical engineering and electrical artisans, frequently find it difficult either to understand the true principles of the dynamo or to deduce the proper proportions, from the information contained in existing text-books. This arises chiefly from the fact that much of the valuable in formation given by physicists unfortunately is not always in the form in which it may be practically applied by the engi neer. N o doubt also many lack that knowledge which is not usually found in text-books, and which is obtained only from actual experience with dynamos. To meet these needs, the author has endeavored to give in a concise and simple form the information most required by those using, building or repairing dynamos. In doing so it has not been thought necessary to preface the book with an elementary treatise on electricity in general, as this is already contained in numerous text books; the author pre-supposes, on the part of the reader, a general knowledge of the subject of electricity and its applications, that which Is contained in this book being limited chiefly to details of the practical appli cation of these principles to the designing, construction and care of dynamos. The book is therefore intended more par ticularly for builders and attendants of dynamos, amateurs and students. It is needless to say that it is not intended for experts, physicists or theorists, nor for those who have the facilities and time to search for such information in the more advanced publications. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.