"There are an infinite number of theories for every set of facts," said the Negro. "Rule number one: assume the simplest; that includes all the known conditions to be true until more conditions arise for which your theory no longer holds. Rule number two: then, and not until, change it." "Then we go on into the jungle," Geo said. "I guess we do," said Urson. "Since we've got this job, we've got to trust ourselves and do it right. Let's see if we can put one more of those things around your neck before we're through." He pointed to the two jewels hanging at Geo's chest. Then he laughed. "One more and you'll be all the way up to me," and he rattled his own triple necklace. CHAPTER V Light lowered in the sky as they walked beside the river, keeping close to the rocky edge and brushing away vines that strung into the water from hanging limbs. Urson broke down a branch as thick as his wrist and as tall as himself and smote the water with it, playfully. "That should put a welt on anyone's head who wants to bother us." He raised the stick from the water and drops ran along the bark, moving sparks at the ends of dark lines. "We'll have to turn into the woods for food soon," said Iimmi, "unless we wait for animals who come down to drink." Urson tugged at another branch, and it twisted loose from fibrous white pulp. "Here," he handed it to Iimmi. "I'll have one for you in a moment, Geo." "And maybe we could explore a little, before it gets dark," Geo suggested. Urson handed him the third staff. "There's not much here I want to see," he muttered. "Well, we can't sleep on the bank. We've got to find a place hidden in the trees." "Can you see what that is through there?" Iimmi asked. "Where?" asked Geo. "Huh...?" Through the thick growth was a rising shadow. "A rock or a cliff?" he suggested. "Maybe," mused Urson, "but it's awfully regular." Geo started off into the underbrush, and the others followed. Their goal was further and larger than it had looked from the river. Once they passed across a section of ten or twelve stones, rectangular and side by side, like paving. Small trees had pushed up between some of them, but for thirty feet, before the edge sank beneath the soft jungle floor it was easier going. Suddenly the growth became thin again and they were at the edge of a relatively clear area. Before them loomed the ruins of a great building. Six girders cleared the highest wall, implying an original height of eighteen or twenty stories. One wall was completely sheared away and fragments of it chunked the ground. The revealed dark caves of broken rooms and cubicles suggested an injured granite hive. They approached slowly. To one side a great metal cylinder lay askew a heap of rubbish. A flat blade of metal transversed it, one side twisting into the ground where skeletal girders shown beneath ripped plating. A row of windows like dark eyes lined the body, and a door gaped in an idiotic oval halfway along its length.