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
amount of light it received.
"There, I guess we're all ready, Ned," announced Tom, at last.
"Now you go to your little coop, and I'll shut myself up in mine.
We can talk over the telephone."
Seated in the little booth in one of the smaller of Tom's shops,
Ned proceeded with his part in the new experiment. A small shelf
had been fitted up in the booth, or closet, and on this was the
apparatus, consisting of a portable telephone set, and a small
box, in which was set a selenium plate. This plate had been wet by
a spray of water in order to test Tom's new theory.
In a similar booth, several hundred feet away, and in another
building, Tom took his place. The two booths were connected by
wires, and in each one was an electric light.
"All ready, Ned?" asked Tom, through the telephone.
"All ready," came the answer.
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