"Whatever the expedition may be that you are contemplating," said Tarzan, "the potential profits must be great indeed if you are willing to risk so much of your own money."

"On the contrary," replied Gridley, "there will be no financial profit for anyone concerned in so far as I now know."

"And you are an American?" asked Tarzan, smiling.

"We are not all money mad," replied Gridley.

"Then what is the incentive? Explain the whole proposition to me."

"Have you ever heard of the theory that the earth is a hollow sphere, containing a habitable world within its interior?"

"The theory that has been definitely refuted by scientific investigation," replied the ape-man.

"But has it been refuted satisfactorily?" asked Gridley.

"To the satisfaction of the scientists," replied Tarzan.

"And to my satisfaction, too," replied the American, "until I recently received a message direct from the inner world."

"You surprise me," said the ape-man.

"And I, too, was surprised, but the fact remains that I have been in radio communication with Abner Perry in the inner world of Pellucidar and I have brought a copy of that message with me and also an affidavit of its authenticity from a man with whose name you are familiar and who was with me when I received the message; in fact, he was listening in at the same time with me. Here they are."

From a portfolio he took a letter which he handed to Tarzan and a bulky manuscript bound in board covers.

"I shall not take the time to read you all of the story of Tanar of Pellucidar," said Gridley, "because there is a great deal in it that is not essential to the exposition of my plan."