Chapter XV. The Airship Clue

"Now Ned, we'll try again. I'm going to use a still stronger current, and this is the most sensitive selenium plate I've turned out yet. We'll see if we can't get a better likeness of you--one that will be plainer."

It was Tom Swift who was speaking, and he and his chum had just completed some hard work on the new photo telephone. Though the apparatus did what Tom had claimed for it, still he was far from satisfied. He could transmit over the wire the picture of a person talking at the telephone, but the likeness was too faint to make the apparatus commercially profitable.

"It's like the first moving pictures," said Tom. "They moved, but that was about all they did."

"I say," remarked Ned, as he was about to take his place in the booth where the telephone and apparatus were located, "this double-strength electrical current you're speaking of won't shock me; will it? I don't want what happened to Eradicate to happen to me, Tom."

"Don't worry. Nothing will happen. The trouble with Rad was that he didn't have the wires insulated when he turned that arc current switch by mistake--or, rather, to play his joke. But he's all right now."

"Yes, but I'm not going to take any chances," insisted Ned. "I want to be insulated myself."

"I'll see to that," promised Tom. "Now get to your booth."

For the purpose of experiments Tom had strung a new line between two of his shops, They were both within sight, and the line was not very long; but, as I have said, Tom knew that if his apparatus would work over a short distance, it would also be successful over a long one, provided he could maintain the proper force of current, which he was sure could be accomplished.

"And if they can send pictures from Monte Carlo to Paris I can do the same," declared Tom, though his system of photo telephony was different from sending by a telegraph system--a reproduction of a picture on a copper plate. Tom's apparatus transmitted the likeness of the living person.

It took some little time for the young inventor, and Ned working with him, to fix up the new wires and switch on the current. But at last it was complete, and Ned took his place at one telephone, with the two sensitive plates before him. Tom did the same, and they proceeded to talk over the wire, first making sure that the vocal connection was perfect.

"All ready now, Ned! We'll try it," called Tom to his chum, over the wire. "Look straight at the plate. I want to get your image first, and then I'll send mine, if it's a success,"

Ned did as requested, and in a few minutes he could hear Tom exclaim, joyfully:

"It's better, Ned! It's coming out real clear. I can see you almost as plainly as if you were right in the booth with me. But turn on your light a little