"I should think so, too," agreed Dora. "That seems to me as hard as singing two notes at once."
"But it can be done, nevertheless; and Edison was so pleased with that invention that he put his factory at Newark into the hands of a capable superintendent and established a laboratory at Menlo Park, where he is now, about twenty-five miles from Newark. Then he began to think about the telephone. Do you know what that is, Dora?"
"I've heard about it, of course, but I never saw one. There are some telephones in Portland, though."
"Yes, and there's going to be one here. I'm going to connect the hotel with the telegraph office at the station this summer, and sometime I'll give you a chance to talk over the wire. It's easier to use the telephone now than it was at first, for in the beginning there was a continual buzzing that was very annoying; but Edison has stopped all that by improving what we call the transmitter."
Dora's idea of a telephone was indistinct; but she was satisfied with the explanation to come, and she wanted to hear more of Mr. Edison. "Has he made anything else?" she asked.
"Oh, yes," replied Uncle John. "What I think is the most wonderful thing Edison has done is the phonograph. Next to the telephone, that to me is the biggest marvel in the world of science. Think, Dora, of speaking into a machine that makes a picture of the sound waves produced by your voice, and then, a day or a year or a century later, letting the instrument work backward and hearing your own voice exactly as it sounded at first. Such a mechanism almost frightens me. It makes me sure that if a man like Edison can keep the idle words men speak through centuries, the Master Mind of this universe can keep them for us forever."
[Illustration: EDISON'S FIRST PHONOGRAPH.]
Dora must have caught a little of her uncle's thought, for she said, slowly, "Do you mean that everything I say I shall hear again sometime?"
"I don't know exactly, Dora. But I am sure that God, who gave you power to speak, knows how to keep your words forever; and I am sure you will never cease to be glad for all the kind words you may speak for human ears to hear.
"But I'd almost forgotten about the electric light, Dora. Let me tell you what Edison said about that the last time I saw him. He told me of seeing in Philadelphia what is called an arc lamp--two pieces of carbon that electricity has heated white hot and that give off a powerful light, much more powerful than any gas lamp you ever saw could give. But a lamp like that, though it makes a fine street lamp, is not suitable for lighting a house. It's too bright and too big. Edison says it needs to be subdivided so that it can be distributed to houses just as gas is now.