"This surface is the outside of the Oroid world, for so they call their earth. At this point the shell between the outer and inner surface is only a few miles in thickness. The two surfaces do not parallel each other here, so that in descending these tunnels we turned hardly more than an eighth of a complete circle.
"At the city of Arite, where Lylda first took me, and where I had my first view of the inner surface, the curvature is slightly greater than that of our own earth, although, as I have said, in the opposite direction."
"And the space within this curvature—the heavens you have mentioned—how great do you estimate it to be?" asked the Doctor.
"Based on the curvature at Arite it would be about six thousand miles in diameter."
"Has this entire inner surface been explored?" asked the Big Business Man.
"No, only a small portion. The Oroids are not an adventurous people. There are only two nations, less than twelve million people all together, on a surface nearly as extensive as our own."
"How about those stars?" suggested the Very Young Man.
"I believe they comprise a complete universe similar to our own solar system. There is a central sun-star, around which many of the others revolve. You must understand, though, that these other worlds are infinitely tiny compared to the Oroids, and, if inhabited, support beings nearly as much smaller than the Oroids, as they are smaller than you."
"Great Caesar!" ejaculated the Banker. "Don't let's go into that any deeper!"
"Tell us more about Lylda," prompted the Very Young Man.