"Set down any number, without letting me know what it is," said he to Joanna Merwin. She set down a number. "Now add twelve and multiply by two." "Well, that is done," said Joanna. "Divide by four, subtract half of the number first set down, and your answer will be six." "Oh, but how did you know that I put down sixty-four?" said Joanna. "I didn't," said Jack. "How could you tell the answer, then?" "That's for you to find out." This puzzle excited a great deal of curiosity. To add to the wonder of the scholars, Jack gave each time a different number to be added in, and sometimes he varied the multiplying and dividing. Harvey Collins, who was of a studious turn, puzzled over it a long time, and at last he found it out; but he did not tell the secret. He contented himself with giving out a number to Jack and telling his result. To the rest it was quite miraculous, and Riley turned green with jealousy when he found the girls and boys refusing to listen to his jokes, but gathering about Jack to test his ability to "guess the answer," as they phrased it. Riley said he knew how it was done, and he was even foolish enough to try to do it, by watching the slate-pencil, or by sheer guessing, but this only brought him into ridicule. "Try me once," said the little C. C. G. W. M. de L. Risdale, and Jack let Columbus set down a figure and carry it through the various processes until he told him the result. Lummy grew excited, pushed his thin hands up into his hair, looked at his slate a minute, and then squeaked out: "Oh--let me see--yes--no--yes--Oh, I see! Your answer is just half the amount added in, because you have----" But here Jack placed his hand over Columbus's mouth. "You can see through a pine door, Lummy, but you mustn't let out my secret," he said. But Jack had a boy's heart in him, and he longed for some more boy-like amusement. CHAPTER VI A BATTLE One morning, when Jack proposed to play a game of ball with the boys, Riley and Pewee came up and entered the game, and objected. "It isn't interesting to play with greenhorns," said Will. "If Jack plays, little Christopher Columbus Andsoforth will want to play, too; and then there'll be two babies to teach. I can't be always helping babies. Let Jack play two-hole cat or Anthony-over with the little fellows." To which answer Pewee assented, of course. That day at noon Riley came to Jack, with a most gentle tone and winning manner, and whiningly begged Jack to show him how to divide 770 by 14. "It isn't interesting to show greenhorns," said Jack, mimicking Riley's tone on the playground that morning. "If I show you, Pewee Rose will want me to show him; then there'll be two babies to teach. I can't be always helping babies. Go and play two-hole cat with the First-Reader boys."