“The Mahars say it is round, like the inside of a tola shell,” he answered, “but that is ridiculous, since, were it true, we should fall back were we to travel far in any direction, and all the waters of Pellucidar would run to one spot and drown us.  No, Pellucidar is quite flat and extends no man knows how far in all directions.  At the edges, so my ancestors have reported and handed down to me, is a great wall that prevents the earth and waters from escaping over into the burning sea whereon Pellucidar floats; but I never have been so far from Anoroc as to have seen this wall with my own eyes.  However, it is quite reasonable to believe that this is true, whereas there is no reason at all in the foolish belief of the Mahars.  According to them Pellucidarians who live upon the opposite side walk always with their heads pointed downward!” and Ja laughed uproariously at the very thought.

It was plain to see that the human folk of this inner world had not advanced far in learning, and the thought that the ugly Mahars had so outstripped them was a very pathetic one indeed.  I wondered how many ages it would take to lift these people out of their ignorance even were it given to Perry and me to attempt it.  Possibly we would be killed for our pains as were those men of the outer world who dared challenge the dense ignorance and superstitions of the earth’s younger days.  But it was worth the effort if the opportunity ever presented itself.

And then it occurred to me that here was an opportunity—­that I might make a small beginning upon Ja, who was my friend, and thus note the effect of my teaching upon a Pellucidarian.

“Ja,” I said, “what would you say were I to tell you that in so far as the Mahars’ theory of the shape of Pellucidar is concerned it is correct?”

“I would say,” he replied, “that either you are a fool, or took me for one.”

“But, Ja,” I insisted, “if their theory is incorrect how do you account for the fact that I was able to pass through the earth from the outer crust to Pellucidar.  If your theory is correct all is a sea of flame beneath us, where in no peoples could exist, and yet I come from a great world that is covered with human beings, and beasts, and birds, and fishes in mighty oceans.”

“You live upon the under side of Pellucidar, and walk always with your head pointed downward?” he scoffed.  “And were I to believe that, my friend, I should indeed be mad.”

I attempted to explain the force of gravity to him, and by the means of the dropped fruit to illustrate how impossible it would be for a body to fall off the earth under any circumstances.  He listened so intently that I thought I had made an impression, and started the train of thought that would lead him to a partial understanding of the truth.  But I was mistaken.

“Your own illustration,” he said finally, “proves the falsity of your theory.”  He dropped a fruit from his hand to the ground.  “See,” he said, “without support even this tiny fruit falls until it strikes something that stops it.  If Pellucidar were not supported upon the flaming sea it too would fall as the fruit falls—­you have proven it yourself!” He had me, that time—­you could see it in his eye.