"Because it proves that the process of condensation and concentration, which produces planets out of the original gases, can take place at uneven speeds! Instead of concentrating to the globular form, Sanus cooled too quickly; she concentrated while she was still a ring!" Smith was struck with another phase of the matter. "Must have a queer sort of gravitation," he pointed out. "Seems to be the same, inside the ring or outside. Surely, doc it can't be as powerful as it is here on the earth?" "No; not likely." "Then, why hasn't it made a difference in the inhabitants? Seems to me the humans would have different structure." "Not necessarily. Look at it the other way around; consider what an enormous variety of animal forms we have here, all developed under the same conditions. The humming-bird and the python, for instance. Gravitation needn't have anything to do with it." Billie was thinking mainly of the question of day and night. "The ring must be inclined at an angle with the sun's rays," she observed. "That being the case, Sanus has two periods each year when there is continuous darkness on the inner face; might last a week or two. Do you suppose the people all hibernate during those seasons?" But no one had an answer to that. Van Emmon said he would give all he was worth to explore the Sanusian mountains long enough to learn their geology. He said that the rocks ought to produce some new mineral forms, due to the peculiar condition of strain they would be subjected to. "I'm not sure," said he thoughtfully, "but I shouldn't be surprised if there's an enormous amount of carbon there. Maybe diamonds are as plentiful as coal is here." At the word "diamonds" Smith glanced covertly at Billie's left hand. But she had hidden it in the folds of her skirt. Next moment the doctor warned them to be quiet; Somat and Rolla were talking again. He was telling her about his world. She learned that his people, who had never concerned themselves with her side of the planet, had progressed enormously beyond the Sanusians. Rolla did not understand all that he told her; but the people on the earth gathered, in one way or another, that civilization had proceeded about as far as that of the year 1915 in Europe. All this, while fellow humans only a few thousand miles away, not only failed to make any progress at all, but lived on, century after century, the absolute slave of a race of bees! But it was a fact. The ancient city in which Rolla found herself had been, only a generation before, a flourishing metropolis, the capital of a powerful nation. There had been two such nations on that side of the planet, and the most violent rivalry had existed between them. "However," Somat told Rolla, "'twas not this rivalry which wrought their downfall, except indirectly. The last great war between them was terrible, but not disastrous. Either could have survived that.