"You're improving, Carnes. This is Dr. Lassen. This is a little out of your line. Doctor, but you may see something familiar. What does it look like to you?"
"Not like an earthquake, Bird, at all events. Offhand I would say that a huge cavern had been washed in the earth and the ground had caved in."
"It looks that way. If you are right, we should find running water if we dig deep enough. Have you been down in the hole, Carnes?"
"No, Doctor."
"Then that's the first thing to do. You have ropes, of course?"
arnes called to the waiting gang of negroes and a dozen of these hurried up with ropes. Dr. Bird slung a rope around his body under his arms and was lowered into the hole. The rope slackened as he reached bottom. Carnes lay on his stomach and looked over the edge. Dr. Bird was gingerly picking his way across the ground. He turned and called up.
"Carnes, you and Lassen can come down if you care to."
In a few minutes the detective and the volcanologist joined him in the cavern. The top surface of the ground was rolled up into waves like the sea. The sides of the hole were almost sheer. The naked rock was exposed for thirty feet. Above the rock could be seen the subsoil, and then the layer of top soil and vegetation. Dr. Bird was carefully examining the rock wall.