Agatha studied him as he wrote fresh symbols. He was plainly dressed and about sixty years of age. There was nothing else worth noting, but he obviously knew his subject and she liked his face. She saw that the girls could follow his explanation, but while suited to their understanding, it was, in one respect, not quite accurate. "I don't know if I've made it much plainer," he said deprecatingly when he stopped. Agatha indicated a group of letters. "It is plainer, thank you! But does the combination of the two elements take place exactly as you have shown? At a normal temperature, the metal's affinity for oxygen--" "Ah," he said, "you know that? It looks as if you had studied the new Austrian theory. But perhaps one may make a small concession, for the sake of clearness." "Science is exact," Agatha replied. "It's a bold claim for us to make," he rejoined, smiling. "Our symbols are guess measures; our elements split up into two or three. But I gather that you refuse to compromise about what, in the meantime, we think is the truth?" "I think one must adhere to it, as far as one knows." "Well, no doubt, that is the proper line. But I've stopped your lecture and perhaps bored your pupils." "No," said Agatha. "You have helped me over awkward ground, and I expect they would sooner listen to a stranger." He went away with the principal, and Agatha wondered about him as she resumed her task. It was plain that he knew something about science, but this was not strange, since geologists and chemists sometimes visited the school. After she dismissed her class the principal sent for her. "I suppose you don't know who that man is?" she asked. Agatha admitted that she did not know and colored when the other told her. The man was a famous scientist who had recently simplified the smelting of some refractory British Columbian ores, and was now understood to be occupied with the problem of utilizing certain barren alkali belts in the West. "Oh!" she said, "I talked to him as if he were one of the girls. In fact, I believe I was gently patronizing." "I don't think he was much hurt." "Then he must have been amused and that is nearly as bad. After he had gone I imagined I'd seen his portrait somewhere." "He hasn't gone yet," the principal answered with a twinkle. "He's waiting to see you in the managers' room, and I must confess to something of a plot when I brought him in quietly to hear your lecture." "But what does he want?" Agatha asked with excited curiosity. "I imagine he wants to offer you a post, but he will tell you about this. You have half an hour before the next class."