You could make a dynamo that would actually work, by arranging such an apparatus so that the coil would spin between the poles of the magnet. But of course the big commercial dynamos are very much more complicated in their construction. Figure 116 shows only the general principle on which they work. The main point to note is that by spinning a coil of wire between the poles of a magnet, you can make electricity flow rapidly through the wire. And it is in this way that most of the electricity we use is made. The power spinning the coil of wire is sometimes steam, and sometimes gasoline or distillate; and water power is very often used. A large amount of our electricity comes from places where there are waterfalls. Niagara, for instance, turns great dynamos and generates an enormous amount of electricity. WHY MANY AUTOMOBILES HAVE TO BE CRANKED. In an automobile, the magneto is a little dynamo that makes the sparks which explode the gasoline. While the automobile is going the engine spins the coil of wire between the magnets, but at starting you have to spin the coil yourself; and doing that is called "cranking" the automobile. "Self-starters" have a battery and motor to spin the coil for you until the engine begins to go; then the engine turns the coil of the magneto. HOW OLD-FASHIONED TELEPHONES ARE RUNG. The old-fashioned telephones, still often used in the country, have little cranks that you turn to ring for central. The crank turns a coil of wire between the poles of the magnet and generates the electricity for ringing the bell. These little dynamos, like those in automobiles, are usually called magnetos. [Illustration: FIG. 118. The magneto in an automobile is a small dynamo.]