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.
"Now then, turn on your switch—the one I showed you—and look right at the sensitized plate. Then turn out your light, and slowly turn it on. It's a new kind, and the light comes up
