Corrus turned and walked away, that his friend might not see what was in his eyes. IX FOUND! It was two weeks to a day when the four on the earth, after having seen very little of each other in the meanwhile, got together for the purpose of finishing their "revelation" to the Sanusians. "Mr. Van Emmon and I," stated Billie coolly, as they put on their bracelets, "have been trying to decide upon the best way of telling them how to obtain fire." Neither Smith nor the doctor showed that he noticed her "Mr. Van Emmon." Evidently the two were still unreconciled. "I argue," remarked the geologist, "that the simplest method will be a chemical one. There's lots of ways to produce fire spontaneously, with chemicals; and this woman Rolla could do it easily." Billie indulged in a small, superior smile. "He forgets that all these chemical methods require pure chemicals. And you don't find them pure in the natural state. You've got to have fire to reduce them with." "What's your proposition, then?" from the doctor. "Optics!" enthusiastically. She produced a large magnifying-glass from her pocket. "All we have to do is to show Dulnop--he's something of a mineralogist--how to grind and polish a piece of crystal into this shape!" Van Emmon groaned. "Marvelous! Say, if you knew how infernally hard it is to find even a small piece of crystal, you'd never propose such a thing! Why, it would take years--Mrs. Van Emmon!" Smith also shook his head. "Neither of you has the right idea. The easiest way, under the circumstances, would be an electrical one." He paused, frowning hard; then vetoed his own plan. "Thunder; I'm always speaking first and thinking afterward. I never used to do it," accusingly, "until I got in with you folks. Anyhow, electricity won't do; you've got to have practically pure elements for that, too." "Guess it's up to you, doc," said Billie. And they all looked respectfully toward their host. He laughed. "You three will never learn anything. You'll continue to think that I'm a regular wonder about these things, but you never notice that I merely stay still and let you commit yourselves first before I say anything. All I have to do is select the one idea remaining after you've disproved the rest. Nothing to it!" He paused. "I'm afraid we're reduced to the spark method. It would take too long to procure materials pure enough for any other plan. Friction is out of the question for such people; they haven't the patience. Suppose we go ahead on the flint-and-spark basis." They went at once into the familiar trance state. Nightfall was approaching on the part of Sanus in which they were interested. Smith and Van Emmon came upon Dulnop and Corrus as they were talking together. The herdsman was saying: