Arcot stared in amazement, his face suddenly clouded in wonder. Morey, who had come up from the power room, stared in equal wonder. Quickly, Wade and Fuller slid into the ray control seats. Their long practice with the rays had made them dead shots, and they had been chosen long before as the ship's official ray operators. "Lord," muttered Morey as he looked at the ships, "where can they have come from?" VII Silently, the four men watched the two ships, waiting for any hostile movement. There was a long, tense moment, then something happened for which three of them were totally unprepared. Arcot burst into sudden laughter. "Don't--ho--hoh-ho--oh--don't shoot!" he cried, laughing so hard it was almost impossible to understand him. "Ohoh--space--curved!" he managed to gasp. For a moment more, Morey looked puzzled--then he was laughing as hard as Arcot. Helplessly, Wade and Fuller looked at them, then at each other. Then, suddenly, Wade caught the meaning of Arcot's remark and joined the other two in laughter. "All right," said Fuller, still mystified, "when you half-witted physicists recover, please let me in on the joke!" He knew it had something to do with the mysterious ships, so he looked closely at them in hopes that he would get the point, too. When he saw it, he blinked in amazement. "Hey! What is this? Those ships are exact duplicates of the _Ancient Mariner_!" "That--that's what I was laughing at," Arcot explained, wiping his eyes. "Four big, brave explorers, scared of their own shadows!" "The light from our own ship has come back to us, due to the intense curvature of the space which encloses us. In normal space, a light ray would take hundreds of millions of years to travel all the way around the Universe and return to its point of origin. Theoretically, it would be possible to photograph our own Galaxy as it was thousands of millennia ago by the light which left it then and has traveled all the way around the curvature of space. "But our space has such terrific curvature that it only takes a fraction of a second for light to make the trip. It has gone all the way around our little cosmos and come back again. "If we'd shot at it, we would have really done ourselves in! The ray beam would go around and hit us from behind!" "Say, that is a nice proposition!" laughed Fuller. "Then we'll be accompanied by those ghosts all the way? There goes the spirit 'nine fathoms deep' which moves the ship--the ghosts that work the sails. This will be a real _Ancient Mariner_ trip!"