, Tom?" called Ned, over the telephone.

"I sure do! Now see if you can get me."

Tom made other connections, and then looked at the sending plate
of his instrument, there being both a sending and receiving plate
in each booth, just as there was a receiver and a transmitter to
the telephone.

"Hurray! I see you, Tom!" cried Ned, over the wire. "Say, this is
great!"

"It isn't as good as I want it," went on Tom. "But it proves that
I'm right. The photo telephone is a fact, and now persons using
the wire can be sure of the other person they are conversing with.
I must tell dad. He wouldn't believe I could do it!"

And indeed Mr. Swift was surprised when Tom proved, by actual
demonstration, that a picture could be sent over the wire.

"Tom, I congratulate you!" declared the aged inventor. "It is good
news!"

"Yes, but we have bad news of Mr. Damon," said Tom, and he told
his father of the disappearance of the eccentric man. Mr. Swift at
once telephoned his sympathy to Mrs. Damon, and offered to do
anything he could for her.

"But Tom can help you more than I can," he said. "You can depend
on Tom."

"I know that," replied Mrs. Damon, over the wire.

And certainly Tom Swift had many things to do now. He hardly knew
at what to begin first, but now, since he was on the right road in
regard to his photo telephone, he would work at improving it.

And to this end he devoted himself, after he had sent out a
general alarm to the police of nearby towns, in regard to the
disappearance of Mr. Damon. The airship clue, he believed, as did
the police, would be a good one to work on.

For several days after this nothing of moment occurred. Mr. Damon
could not be located, and Tom's airship might still be sailing
above the clouds as far as getting any trace of it was concerned.

Meanwhile the young inventor, with the help of Ned, who was given
a leave of absence from the bank, worked hard to improve the photo
telephone.

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