explained now—the reason why they make diamonds in this lonely place, near the top of the mountain. They need a place where the lightning is powerful. I can understand it now—I suspected it before. They make diamonds by lightning!"
"Are you sure?" cried Mr. Jenks.
"Positive."
"I agree with you," said Tom Swift. "I was just getting on that track myself, when I saw the electric wires running to the steel box. That explains the upright rod on the top of the mountain. The man says a storm is coming—very well; we'll stay here and watch them make diamonds!"
As he spoke there came the mutter of thunder, and the mountain vibrated slightly. The men in the cave redoubled their activity. Tom and his friends felt that the secret process they had so long sought was about to be demonstrated before their eyes.
