“That’s the idea!” cried Carl.
Ten feet in the passage turned abruptly to the north and there the boys drew up. Ben pointed straight ahead.
“There’s a light!” he said.
Carl glanced eagerly in the direction indicated but saw nothing.
“A ghost light!” he laughed.
“No, but there is an illumination!” insisted Ben.
“Point it out, then,” chuckled Carl. “It is as dark in there as a stack of black cats!”
Ben looked amazed for an instant and then started forward.
“I did see a light!” he insisted.
Carl laughed and stood at the angle of the passage where he could see the machines, lighted by one small acetylene lamp, and also follow the progress of his chum into the interior.