THE LIBRARY OF WORK AND PLAY CARPENTRY AND WOODWORK By Edwin W. Foster ELECTRICITY AND ITS EVERYDAY USES By John F. Woodhull, Ph.D. GARDENING AND FARMING By Ellen Eddy Shaw HOME DECORATION By Charles Franklin Warner, Sc.D. HOUSEKEEPING By Elizabeth Hale Gilman MECHANICS, INDOORS AND OUT By Fred T. Hodgson NEEDLECRAFT By Effie Archer Archer OUTDOOR SPORTS, AND GAMES By Claude H. Miller, Ph.B. OUTDOOR WORK By Mary Rogers Miller WORKING IN METALS By Charles Conrad Sleffel. [Illustration: Drawing by J. Hodson Redman. Harold Sending the C. Q. D. Message (_See page 355_).] _The Library of Work and Play_ ELECTRICITY AND ITS EVERYDAY USES BY JOHN F. WOODHULL, PH.D. [Illustration] McGOWEN-MAIER & CO. CHICAGO, ILL. ALL RIGHTS RESERVED, INCLUDING THAT OF TRANSLATION INTO FOREIGN LANGUAGES, INCLUDING THE SCANDINAVIAN COPYRIGHT, 1911, BY DOUBLEDAY, PAGE & COMPANY PREFACE Why do we pursue one method when instructing an individual boy out of school, and a very different method when teaching a class of boys in school? The school method of teaching the dynamo is to begin with the bar magnet and, through a series of thirty or forty lessons on fundamental principles, lead up to the dynamo, which is then presented, with considerable attention to detail, as a composite application of principles. This might be styled the synthetic method. He who teaches a boy out of school is pretty likely to reverse this order and pursue the analytic method. The class in school has very little influence in determining the order of procedure. The lone pupil with his questions almost wholly determines the order of procedure. Out of school no one has the courage to deny information to a hungry boy; in school we profess to put a ban upon information giving, and we do quite effectually deaden his sense of hunger. The school method rarely yields fruit which lasts beyond the examination period; on the other hand, a considerable number of boys have become electrical experts without the aid of a school. This book is the story of how my boy and I studied _electricity_ together. We have had no other method than to attack our problems directly, and _principles_ have come in only when they were needed.