Tom could hardly wait to fasten up his boat for the night, so
eager was he to get to his shop laboratory and try the new idea. A
gleam of hope had come to him.

It was still early evening, and Tom, when enticed out by Ned, had
left his photo telephone apparatus in readiness to go on with his
trials as soon as he should have come back.

"Now for it, Ned!" exclaimed the young inventor, as he took off
his coat. "First I'll sensitize a selenium plate, and then I'll
wet it. Water is always a good conductor of electricity, and it's
a wonder that I forgot that when I was planning this photo
telephone. But seeing the sparkle of lights, and the reflection of
ourselves in the lake to-night, brought it back to me. Now then,
you haven't anything special to do; have you?"

"Not a thing, Tom."

"That's good. Then you get in this other telephone closet--the one
in the casting shop. I'll put a prepared plate in there, and one
in the booth where I'm to sit. Then I'll switch on the current,
and we'll see if I can make you out, and you notice whether my
image appears on your plate."

It took some little time to make ready for this new test. Tom was
filled with enthusiasm, and he was sure it was going to be
successful this time. Ned watched him prepare the selenium plates
--plates that were so sensitive to illumination that, in the dark,
the metal would hardly transmit a current of electricity, but in
the light would do so readily, its conductivity depending on the