In order to obviate such manufacturing the generator or dynamo is used and electricity is made in this way by induction. In other words, we make it by letting a coil of wire (or several coils) be revolved by steam or water power (usually) as it cuts through the area of magnetism (field) of a giant magnet something like those we used when we were children. This coil catches the electricity and it is led off by wires wherever we want it to perform. The coil on the spindle is called the armature, where the wire is attached to lead off the electricity from the armature are contact-pieces, and the plates which make the contact with the contact pieces and to which are attached the wires of the out-going electric circuit are called the brushes. There is much more to say, but not in this article. If you are interested we refer you to Charles R. Gibson’s “Romance of Electricity” for simple electrical explanations. The motor with a few mechanical changes is the reverse of the dynamo; it works by electricity and changes it into mechanical power to work our washing machines, etc. There are on the market A. C., D. C., and Universal motors. These you will understand after the next section which takes up A. C. and D. C. electricity. “Madam, do you use A. C. or D. C.?” asks the man selling you a washing machine. Most decent folks are quite at sea at this seemingly geographic question, and yet after all it is the most complicated simple thing in the world. D. C. doesn’t mean District of Columbia; it simply means Direct Current. And A. C. means Alternating Current. And on these two kinds hang all the wires of electric profits. Direct Current or D. C. is a current that runs in one direction over the wire like water through a pipe. It is simple to visualize, even if electricity does flow 163,000 miles per second. But alternating current (A. C.) is electricity which alternates and goes back and forth, generally. Even though it goes back and forth in waves of tremendous rapidity, you can see that there must be a time in this period when the electricity is for an infinitesimal space of time at low power, and another infinitesimal space of time at high. In order to keep the supply even and steady, two and sometimes three coils of wire are used in the generator to catch the electricity so that there is scant opportunity for the electric supply to be anything but even, for when one coil is up the other is down and thus they even up the strength of the current. So when your salesman asks you when you buy a motor, “If you have A. C. or D. C. electricity” and you say A. C. he may go on and say, “How many phase?” Then you should find out the answer from your lighting company. He then may ask you how many cycles, which when translated means the electric period it takes for the alternating current to flow back and forth. Now dynamos for D. C. and A. C. electricity vary slightly, but that need not trouble _us_.