While this book shows boys what they can do themselves, its scope has been enlarged by Mr. Baker’s [chapter] explaining briefly the working of electricity all about us, in light and heat, in the trolley-car, and other daily applications. In addition, Mr. Adams has prepared a Dictionary of Electrical Terms, and these brief definitions will be found peculiarly helpful in the first reading of the book. It is believed that there is no book in this particular field comparable to Harper’s Electricity Book in its comprehensiveness, practical character, and the number and usefulness of its illustrations. It follows the successful Out-door Book for Boys in Harper’s series of Practical Books for Boys, and it will be followed by How to Understand Electrical Work, a book, not of instructions in making electrical apparatus, but of explanations of the commercial uses of electricity all about us.
Part I
ELECTRICITY BOOK FOR BOYS
Chapter I
SOME GENERAL EXPLANATIONS
We are living in the age of electricity, just as our fathers lived in the age of steam. Electricity is the world-power, the most powerful and terrible of nature’s hidden forces. Yet, when man has learned how to harness its fiery energies, electricity becomes the most docile and useful of his servants. Unquestionably, electricity is to-day the most fascinating and the most profitable field for the investigator and the inventor. The best brains of the country are at work upon its problems. New discoveries are constantly being recorded, and no labor is thought too great if it but add its mite to the sum total of our knowledge. And yet, ridiculous as the statement may seem, we do not know what electricity is. We only know certain of its manifestations—what it can do. All we can say is that it does our bidding; it propels our trains, lights our houses and streets, warms us, cooks for us, and performs a thousand and one other tasks at the turn of a button or at the thrust of a switch. But what it is, we do not know. Electricity has no weight, no bulk, no color. No one has seen it; it cannot be classified, nor analyzed, nor resolved into its ultimate elements by any known process of science. We must content ourselves with describing it as one manifestation of the energy which fills the universe and appears in a variety of forms—such as heat, light, magnetism, chemical affinity, and mechanical motion. In all probability it is one of those phenomena of nature that are destined to remain forever secret. Thus it stands in line with gravitation, magnetism, the active principle of radium, and the perpetual motion of the solar system.
Electricity was known to the early Greeks; indeed, it derives its name from the Greek word for amber (electron). For many centuries amber was credited with certain special or magical powers. When it was rubbed with a flannel cloth, “the hidden spirit” came out and laid hold of small detached objects, such as bits of paper, thread, chips, or pith-balls. No one could explain this phenomenon. It was looked upon with superstitious awe and the amber itself was regarded as possessing the special attributes of divinity. But as time went on, it was discovered that in various other substances this mysterious attractive power could be excited, at will, through the agency of friction. Rubbing a piece of glass rod with silk or leather generated an “electricity” identical with that of the amber; or the same result could be obtained by exciting hard rubber with catskin. The conclusion followed that electricity was not a property of the special materials employed to generate it, but that it came from without, from that great reservoir of energy, the atmosphere. Then came Franklin with his experiment of the kite, and the invention of the Leyden-jar and the chemical production of the electric fluid by means of batteries. It was shown that the properties of the new and strange force were the same, whether it was produced by the static (frictional) process or by the galvanic (chemical) method. Electrical science as a science, had begun.