"Better not touch anything," advised Sammy, as Bob put out his hand to examine one of the tubes with glass in the end.
"Why not?" was asked.
"Because you might get a shock."
"A shock? How do you make that out?"
"Why there's some electric batteries attached to the things," said Sammy, pointing out the dry cells in their red pasteboard boxes.
"That's right," agreed Frank. "They're the same kind of batteries Jerry Grow has in his motor-boat. And they can give you a fierce shock, too."
"What, those little things?" asked Bob, in surprise.
"Sure," spoke Sammy. "You see the batteries aren't so strong in themselves, but when you run the current through a production coil——"
"Induction coil—not production," corrected Frank.