Page:Tom Swift and His Photo Telephone.djvu/15

Rh "Somewhat, yes. Though I shall probably use a metal plate instead of glass. It will be just as if you were talking over a telephone in an open field, where you could see the other party and he could see you."

"But how are you going to do it, Tom?"

"Well, I haven't quite decided. I shall probably have to use the metal called selenium, which is very sensitive to light, and which makes a good or a poor electrical conductor according as more or less light falls on it. After all, a photograph is only lights and shadows, fixed on sensitive paper or films."

"Well, Tom, maybe you can do it, and maybe you can't. I admit you've used some good arguments," said Mr. Swift. "But then, it all comes down to this: What good will it be if you can succeed in sending a picture over a telephone wire?"

"What good, Dad? Why, lots of good. Just think how important it will be in business, if you can make sure that you are talking to the party you think you are. As it is now, unless you know the person's voice, you can't tell that the man on the other end of the wire is the person he says he is. And even a voice can be imitated.

"But if you know the person yourself, he