He was carrying a small wooden box which he placed on the desk and opened. If Ned, as he leaned over eagerly, expected to see anything astonishing he was disappointed. Resting on the velvet lining was simply a round disk of a greenish substance perhaps six inches in diameter. This was mounted in a gleaming metal ring from the edges of which there projected five electric binding posts.
He Was Carrying a Wooden Box
"Funny kind of an eye," observed Ned. "You can't even see through it."
"You'll soon see through it, all right," retorted Tom, laying the disk on his desk and connecting four dry cells to the binding posts. He placed a small rheostat in the circuit so that the strength of the current might be regulated.
The Disk Was Mounted in a Metal Ring
Slowly he moved the little handle over the graduated dial. A minute passed during which, so far as Ned could see, nothing happened. Without warning the green crystal suddenly glowed brightly for a fraction of a second, then could not be seen at all. The polished ring of metal in which it had been mounted alone remained.
"It's gone!" cried Ned in bewilderment. "I can see your desk top right through where it was!"
"No," smiled the inventor, "it's still there as you'll find if you try to poke your finger through the metal ring."