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PREFACE TO THIRD EDITION.
THE revision of this popular work had just been commenced, when it was sadly interrupted by the death of Mr. Davis, and has been completed by other hands.
Much that was alien to the purpose of the book has been discarded, and new material so extensively introduced as to render this a practically new work.
The wiring tables have all been recalculated on a uniform basis and arranged in a more convenient manner for practical uSe.
The object has been to produce a book for wiremen thoroughly reliable and practical in its data, and free from verbiage and padding.
PREFACE TO FOURTH EDITION.
THE new insurance rules of the Underwriters' International Electric Association, which have been generally adopted throughout the United States, and will, it is thought, finally supersede all others, have been substituted in the present edition.
An important section has been expressly prepared for this edition on the calculation of alternating current wiring, which, for the first time, brings this subject within the reach of practical men.