"Climatic changes, geographical changes, all altered the face of our continents. There was a sea in Kansas; England was part of Europe. So, even though as many as fifty such ships were lost here, they could all have been ground to bits by the ice flow, buried miles deep in quakes, or rusted away generations before the first really intelligent man arrived to wonder at them. Certainly there couldn't be too many such wrecks to be found. What do you think this planet was, a flypaper to attract them?" "But if ships crashed here once, why didn't they later when men were better able to understand them?" Ross countered. "For several reasons--all of them possible and able to be fitted into the fabric of history as we know it on this world. Civilizations rise, exist, and fall, each taking with it into the limbo of forgotten things some of the discoveries which made it great. How did the Indian civilizations of the New World learn to harden gold into a useable point for a cutting weapon? What was the secret of building possessed by the ancient Egyptians? Today you will find plenty of men to argue these problems and half a hundred others. "The Egyptians once had a well-traveled trade route to India. Bronze Age traders opened up roads down into Africa. The Romans knew China. Then came an end to each of these empires, and those trade routes were forgotten. To our European ancestors of the Middle Ages, China was almost a legend, and the fact that the Egyptians had successfully sailed around the Cape of Good Hope was unknown. Suppose our space voyagers represented some star-born confederacy or empire which lived, rose to its highest point, and fell again into planet-bound barbarism all before the first of our species painted pictures on a cave wall? "Or take it that this world was an unlucky reef on which too many ships and cargoes were lost, so that our whole solar system was posted, and skippers of star ships thereafter avoided it? Or they might even have had some rule that when a planet developed a primitive race of its own, it was to be left strictly alone until it discovered space flight for itself." "Yes." Every one of Ashe's suppositions made good sense, and Ross was able to believe them. It was easier to think that both Furry-face and Baldy were inhabitants of another world than to think their kind existed on this planet before his own species was born. "But how did the Reds locate that ship?"