The prime instinct of almost any boy at play is to _make_ and to _create_. He will _make_ things of such materials as he has at hand, and use the whole force of dream and fancy to create something out of nothing. The five-year-old will lay half a dozen wooden blocks together with a spool on one end and tell you it is a steam train. And it is. He has both made and created an engine, which he sees but which you don’t, for the blocks and spool are only a symbol of his creation. Give his older brother a telephone receiver, some wire and bits of brass, and he will make a wireless telegraph outfit and listen to a steamship hundreds of miles away spell out its message to the shore. The wireless outfit is not a symbol, but something that you can both hear and see in operation even though you may not understand the whispering of the dots and dashes. And as soon as the mystery of this modern wonder more firmly grips your imagination, you perhaps may come to realize that we are living more and more in the age of electricity and mechanism. Electricity propels our trains, lights our houses and streets, makes our clothes, cures our ills, warms us, cooks for us and performs an innumerable number of other tasks at the turning of a little switch. A mere list is impossible. Almost every boy experiments at one time or another with electricity and electrical apparatus. It is my purpose in writing this book to open this wonderland of science and present it in a manner which can be readily understood, and wherein a boy may "do something." Of course there are other books with the same purport, but they do not accomplish their end. They are not practical. I can say this because as a boy I have read and studied them and they have fallen far short of teaching me or my companions the things that we were seeking to learn. If they have failed in this respect, they have done so perhaps not through any inability of the author, but from the fact that they have not been written from the _boy’s standpoint_. They tell what the author _thought_ a boy ought to know but not what he really does want to know. The apparatus described therein is for the most part imaginary. The author thought it might be possible for a boy to build motors, telegraph instruments, etc., out of old bolts and tin cans, but _he never tried to do so himself_. The apparatus and experiments that I have described have been constructed and carried out by _boys_. Their problems and their questions have been studied and remedied. I have tried to present practical matter considered wholly from a boy’s standpoint, and to show the young experimenter just what he can do with the tools and materials in his possession or not hard to obtain.