[Illustration: FIRST DIRECT-CONNECTED ELECTRIC GENERATOR UNIT OF LARGE CAPACITY EVER CONSTRUCTED UP TO THE TIME IT WAS MADE BY THOMAS A. EDISON IN JUNE, 1881. CAPACITY, 1200 INCANDESCENT LAMPS OF 16 CANDLE-POWER EACH] A-B-C OF ELECTRICITY BY WILLIAM H. MEADOWCROFT HARPER & BROTHERS PUBLISHERS NEW YORK & LONDON A-B-C of Electricity COPYRIGHT, 1888, 1909, BY WILLIAM H. MEADOWCROFT COPYRIGHT, 1915, BY HARPER & BROTHERS PRINTED IN THE UNITED STATES OF AMERICA PUBLISHED MAY, 1915 FROM THE LABORATORY OF THOMAS A. EDISON ORANGE, N. J. MR. W. H. MEADOWCROFT, _New York City_. _DEAR SIR_: _I have read the MS. of your "A-B-C of Electricity," and find that the statements you have made therein are correct. Your treatment of the subject, and arrangement of the matter, have impressed me favorably. _Yours truly_, _THOS. A. EDISON_ CONTENTS CHAP. PAGE INTRODUCTION TO NEW EDITION viii PREFACE x I. 1 II. DEFINITIONS 3 III. MAGNETISM 16 IV. THE TELEGRAPH 23 V. WIRELESS TELEGRAPHY 33 VI. THE TELEPHONE 40 VII. ELECTRIC LIGHT 54 VIII. ELECTRIC POWER 87 IX. BATTERIES 95 X. CONCLUSION 127 INTRODUCTION TO NEW EDITION The favor with which this book has been received has brought about the preparation of this new edition. The present volume has been enlarged by the addition of certain new material and it has been entirely reset. Some new illustrations have been made, and in its new dress the book, it is hoped, will be found to afford an even larger measure of usefulness. The principles of the science remain the same, but the author is glad of the opportunity to note certain developments in their application. W. H. M. EDISON LABORATORY, _April, 1915_. PREFACE While there is no lack of most excellent text-books for the study of those branches of Electricity which are above the elementary stage, there is a decided need of text-books which shall explain, in simple language, to young people of, say, fourteen years and upward, a general outline of the science, as well as the ground-work of those electrical inventions which are to-day of such vast commercial importance.