Now, if you will read patiently and carefully, we will try and explain how both these lights are made.
Fig. 16
You have seen that the telegraph, telephone, electric bells, etc., are worked by batteries. Electric lights, however, require such a large amount of current that it is too expensive to produce them in large quantities by batteries. A small number of lamps could be lighted by batteries, but if we were to attempt to use them to light 500 or 1,000 lamps together, the expense would be so enormous as to make it entirely out of the question.
There are many millions of incandescent lamps in use in the United States, but you will easily see that there could not be that number used if we had to depend on batteries to light them. You will understand this more thoroughly when you have finished reading this little book.
Well, you will ask, if we cannot use batteries, what is used to produce these electric lights?
Machines called "dynamo-electric machines," or "generators," which are driven by steam-engines or water-power, are used to produce the electricity which makes these lamps give us light.
You will remember that in the chapter on Magnetism we explained to you how electricity makes magnetism, and now we will explain how, in the dynamo, magnetism makes electricity.
