I WAS amazed, yet I had half-suspected this. I could not account for his sphere of gleaming light that illuminated his chambers except by the theory of radium. Yet it seemed incredible that these people, who had not even discovered the principle of the wheel, who knew nothing of iron, who had not even availed themselves of water power, and who possessed no machinery, no mechanical devices, could have mastered that powerful, elusive, terrible element--radium. Very painstakingly Nohul Voh tried to explain it to me. The harmless ore that occurred in the rocks and which, as nearly as I could determine, was a form of a uranium mineral, when placed near a rare green rock, would cause the latter to remain poised in air. He pointed to the mysterious green sphere as an example. “But,” he continued, “no power could move the green mineral either closer to or farther from the material.” But he had discovered that, by placing rods of various metals near the green mineral the latter would move towards them and upon touching them would move to the next. Moreover--and this was so astounding I could scarcely believe his words--the green stone revolved at the same time, and made one complete revolution between sunrise and sunset and another between sunset and sunrise! To him, who studied the stars and the heavens and computed the eclipses and was responsible for the keeping of the calendars, this instantly presented possibilities. He had made a sphere of the green rock, had arranged it above a polished surface on which astronomical computations and figures could be engraved, and had arranged rods at definite distances about the circumference. He had thus divided the day and night into fractions, and--by some remarkable coincidence--he had provided _twelve_ of these rods so that the sphere, rotating at twice the speed of the earth touched the twelve rods in succession during each revolution or in other words made twenty-four contacts during the complete period from sunrise to sunrise. But he had gone even farther. He had made calculations and measurements, had checked up accurately on his observations, and by patient experimenting and testing had converted his apparatus into a miniature solar system from which, at any time, he could determine the solstices, the eclipses, the positions of the planets and the constellations. All this was astonishing, almost incredible, but he demonstrated it before my eyes. Moreover, he knew that the earth was round! Reasoning backward from his model he had become convinced that the earth was a sphere, that the other celestial bodies were also spheres, and he was keen on learning from me what lay on the other surfaces of our earth.