Presently Jason removed his earphones and turned toward me. "I was getting music," he said; "strange, weird music, and then suddenly there came loud shouts and it seemed that I could hear blows struck and there were screams and the sound of shots."

"Perry, you know, was experimenting with gunpowder down there below, in Pellucidar," I reminded Jason, with…a grin; but he was inclined to be serious and did not respond in kind.

"You know, of course," he said, "that there really has been a theory of an inner world for many years."

"Yes," I replied, "I have read works expounding and defending such a theory."

"It supposes polar openings leading into the interior of the earth," said Jason.

"And it is substantiated by many seemingly irrefutable scientific facts," I reminded him—"open polar sea, warmer water farthest north, tropical vegetation floating southward from the polar regions, the northern lights, the magnetic pole, the persistent stories of the Eskimos that they are descended from a race that came from a warm country far to the north."

"I'd like to make a try for one of the polar openings," mused Jason as he replaced the earphones.

Again there was a long silence, broken at last by "a sharp exclamation from Jason. He pushed an extra headpiece toward me.

"Listen!" he exclaimed.

As I adjusted the earphones I heard that which we had never before received on the Gridley Wave—code! No wonder that Jason Gridley was excited, since there was no station on earth, other than his own, attuned to the Gridley Wave.

Code! What could it mean? I was torn by conflicting emotions—to tear off the earphones and discuss this amazing thing with Jason, and to keep them on and listen.

I am not what one might call an expert in the intricacies of code, but I had no difficulty in understanding the simple signal of two letters, repeated in groups of three, with a pause after each group: "D.I., D.I., D.I.," pause; "D.I., D.I., D.I.," pause.