“Any gold there?” asked Case.
“Yes, plenty of it.”
“So that is what they are all after! Well, why don’t they get it?”
“Do they have to dive for it?” asked Case. “The caverns must be full of water, if they are deep.”
“The water in the crater follows the surface of the river, of course,” Frank answered. “When there is high water, the current sweeps over the mouth of the crater, and when there is low water the bottoms of some of the caverns are dry—the caverns which are shallow in comparison with the others.”
“I’ve got it now!” roared Alex.
“Smarty!” Jule reproved.
“What is it you’ve got?” asked Case.
“The answer!” was the reply.
“Give it, then!”