Paul returned to the tower more quickly than Monsieur Roger had expected. Instead of returning to the chÂteau, he had taken the shortest cut, had reached the village, and had procured there the two things wanted. He climbed up the tower and arrived beside Monsieur Roger, holding out the ball of twine and the yard-stick.

"You are going to see, you little doubter, that I was not wrong," said Monsieur Roger.

He tied a stone to the twine, and let it down outside the tower to the ground.

"This length of twine," he said, "represents exactly the height of the tower, does it not?"

"Yes, sir," answered Paul.

Monsieur Roger made a knot in the twine at the place where it rested on the top of the tower. Then he asked Paul to take the yard-stick which he had brought, and to hold it extended between his two hands. Then, drawing up the twine which hung outside the tower, he measured it yard by yard. Paul counted. When he had reached the number sixty, he could not help bending over to see how much remained of the twine.

"Ah, sir," he cried, "I think you have won."

"Let us finish our count," said Monsieur Roger, quietly.

And Paul counted,—

"Sixty-one, sixty-two,—sixty-two feet——"

"And?"

"And six inches!" cried Paul.

"I have won, as you said, my young friend," cried Monsieur Roger, who enjoyed Paul's surprise. "Now let us cautiously descend and return to the chÂteau, where the breakfast-bell will soon ring."

The descent was made in safety, and they directed their steps towards Sainte-Gemme. Paul walked beside Monsieur Roger without saying anything. He was deep in thought.

Monsieur Roger, understanding what was going on in the brain of his friend, took care not to disturb him. He waited, hoping for an answer. His hope was soon realized. As they reached the park, Paul, who, after thinking a great deal, had failed to solve the difficulty, said, all of a sudden,—

"Monsieur Roger!"

"What, my friend?"

"How did you measure the tower?"

Monsieur Roger looked at Paul, and, affecting a serious air, he said,—

"It is impossible, entirely impossible for me to answer."

"Impossible?" cried Paul, in surprise.

"Yes, impossible."

"Why, please?"

"Because in answering I will break the promise that I have made you,—the promise to say nothing about chemistry or physical science."

"Ah!" said Paul, becoming silent again.

Monsieur Roger glanced at his companion from the corner of his eye, knowing that his curiosity would soon awake again. At the end of the narrow, shady pathway they soon saw the red bricks of the chÂteau shining in the sun; but Paul had not yet renewed his question, and Monsieur Roger began to be a little uneasy,—for, if Paul held his tongue, it would show that his curiosity had vanished, and another occasion to revive it would be difficult to find.

Luckily, Paul decided to speak at the very moment when they reached the chÂteau.

"Then," said he, expressing the idea which was uppermost,—"Then it is physical science?"

Monsieur Roger asked, in an indifferent tone,—

"What is physical science?"

"Your method of measuring the tower."

"Yes, it is physical science, as you say. Consequently, you see very well that I cannot answer you."

"Ah, Monsieur Roger," said Paul, embarrassed, "you are laughing at me."

"Not at all, my friend. I made a promise; I must hold to it. I have a great deal of liking for you, and I don't want you to dislike me."

"Oh, sir!"

Suddenly they heard the voice of Monsieur Dalize, who cried, cheerfully,—

"See, they are already quarrelling!"

For some moments Monsieur Dalize, at the door of the vestibule, surrounded by his wife and his children, had been gazing at the two companions. Monsieur Roger and Paul approached.

"What is the matter?" asked Monsieur Dalize, shaking hands with his friend.

"A very strange thing has happened," answered Monsieur Roger.

"And what is that?"

"Simply that Master Paul wants me to speak to him of physical science."

An astonished silence, soon followed by a general laugh, greeted these words. Miss Miette took a step forward, looked at Paul with an uneasy air, and said,—

"Are you sick, my little Paul?"

Paul, confused, kept silent, but he answered by a reproachful look the ironical question of his friend Miette.

"But whence could such a change have come?" asked Madame Dalize, addressing Monsieur Roger. "Explain to us what has happened."

"Here are the facts," answered Monsieur Roger. "We had climbed up the tower of Heurtebize——"

Madame Dalize started, and turned a look of uneasiness towards Paul.

"Paul was not at fault," Monsieur Roger hastened to add. "I was the guilty one. Well, we were up there, when Master Paul got the idea of estimating the height of the tower. I answered that nothing was more simple than to know it at once. I asked him to let fall a stone. I looked at my watch while the stone was falling, and I said, 'The tower is sixty-two feet and six inches high.' Master Paul seemed to be astonished. He went after a yard-stick and some twine. We measured the tower, and Master Paul has recognized that the tower is in fact sixty-two feet and six inches high. Now he wants me to tell him how I have been able so simply, with so little trouble, to learn the height. That is a portion of physical science; and, as I made Master Paul a promise this very morning not to speak to him of physical science nor of chemistry, you see it is impossible for me to answer."

Monsieur Dalize understood at once what his friend Roger had in view, and, assuming the same air, he answered,—

"Certainly, it is impossible; you are perfectly right. You promised; you must keep your promise."

"Unless," said Miss Miette, taking sides with her friend Paul,—"unless Paul releases Monsieur Roger from his promise."

"You are entirely right, my child," said Monsieur Roger; "should Paul release me sufficiently to ask me to answer him. But, as I remarked to you a moment ago, I fear that he will repent too quickly, and take a dislike to me. That I should be very sorry for."

"No, sir, I will not repent. I promise you that."

"Very well," said Miette; "there is another promise. You know that you will have to keep it."

"But," answered Monsieur Roger, turning to Paul, "it will be necessary for me to speak to you of weight, of the fall of bodies, of gravitation; and I am very much afraid that that will weary you."

"No, sir," answered Paul, very seriously, "that will not weary me. On the contrary, that will interest me, if it teaches me how you managed to calculate the height of the tower."

"It will certainly teach you that."

"Then I am content," said Paul.

"And I also," said Monsieur Roger to himself, happy to have attained his object so soon.