So, you see, power can be carried in the form of electricity through two wires over very great distances and made to do work at a long way from the engine which is turning the dynamo to make the electricity. Thus, you may have brought into your house wires which will give lights and, at the same time, power to run a sewing-machine, a lathe, or any other piece of machinery. Having learned so far that a dynamo will make a continuous current of electricity, and that two wires will carry this current to any place where it is wanted, let us now see what takes place in the electromotor to transform the electricity into power. An electromotor (which we will now call by its short name, motor) is simply a machine made like a dynamo. Curious as it may seem to you, it is a fact that if you take two dynamo-machines exactly alike, and run one with the steam-engine so as to produce electricity, and then take the two main wires and attach them to the brushes of the other dynamo, the electricity will drive this other dynamo so as to produce a great deal of power which could be used for driving other machines. Thus, the second dynamo would become a motor. In the chapter on dynamos we explained something about the way they were made and how the electricity was produced. THE MOTOR You will remember that the armature consists of a spool wound with wire. This spool is made of iron plates fastened together so as to form one solid piece. The armature of a motor may be made in the same way; in fact, the whole motor is practically a dynamo-machine. There is something more about magnetism which we will tell you of here, because you will more easily understand it in its relation to an electromotor. If we take an ordinary piece of iron and bring one end of it near to (but not touching) one pole of a magnet, this piece of iron will itself become a weaker magnet as long as it remains in this position. This is said to be magnetism by "induction." The end of the piece of iron nearest to the magnet will be of the opposite polarity. For instance, if the pole of the magnet were north, the end of the iron which was nearest to this north pole would be south, and, of course, the other end would be north. To make this more plain we show it in the following sketch. (Fig. 27.) This would be the same whether the magnet were a permanent or an electromagnet. You will remember also that the north pole of one magnet will _attract the south pole_ of another magnet, but will _repel a north pole_. These are the principles made use of in an electromotor, and we will now try to show you how this is carried into practice. [Illustration: STEEL PERMANENT MAGNET IRON Fig. 27] Although a motor is made like a dynamo, we will show a different form of machine from the dynamo already illustrated, because it will help you to understand more easily. (Fig. 28.)