"It is the characteristic of intelligent races manifesting itself--curiosity," pointed out Stel Felso Theu. "Are these the type of men still living in this valley, or who will be living there in fifty thousand years?" asked Zezdon Afthen. "I'd say they weren't Egyptians as we know them, but typical Neolithic men. It seems they have brains fully as large as some of the men I see on the streets of New York. I wonder if they have the ability to learn as much as the average man of--say about 1950?" The Neolithic men were warming up. There was an orator among them, and his grunts, growls, snorts and gestures were evidently affecting them. They had sent the women back (by the simple and direct process of sweeping them up in one arm and heaving them in the general direction of home). The men were brandishing polished stone knives and axes, various instruments of war and peace. One favorite seemed to be a large club. "Let's forestall trouble," suggested Arcot. He drew his ray pistol, and turned it on the ground directly in front of them, and about halfway between them and the Neoliths. A streak of the soil about two feet wide flashed into intense radiation under the impact of millions on millions of horsepower of radiant energy. Further, it was fused to a depth of twenty feet or more, and intensely hot still deeper. The Neoliths took a single look at it, then turned, and raced for home. "Didn't like our looks. Let's go back." They wandered about the world, investigating various peoples, and proved to their own satisfaction that there was no Atlantis, not at this time at any rate. But they were interested in seeing that the polar caps extended much farther toward the equator; they had not retreated at that time to the extent that they had by the opening of history. They secured some fresh game, an innovation in their larder, and a welcome one. Then the entire ship was swept out with fresh, clean air, their water tanks filled with water from the cold streams of the melting glaciers. The air apparatus was given a new stock to work over. Their supplies in a large measure restored, thousands of aerial photographic maps made, they returned once more to space to wait. Their time was taken up for the most part by actual work on the enormous mass of calculation necessary. It is inconceivable to the layman what tremendous labor is involved in the development of a single mathematical hypothesis, and a concrete illustration of it was the long time, with tremendously advanced calculating machines, that was required in their present work.