"Yes," said Miette, speaking both for Paul and for herself; "yes, we have understood,—except when you speak of oxygen, of carbon, and of combustion."
"Oh, I was wrong to speak of them," answered Monsieur Roger, pretending to be vexed.
"That may be," answered Miss Miette, very calmly; "but as you did speak of them, you must tell us what they are."
"Yes, you must, my friend," remarked Monsieur Dalize, taking sides with his little girl.
"Mustn't he, papa? mustn't Monsieur Roger explain?" asked Miette.
"Come, now," said Monsieur Roger, in a resigned tone. "You must know, then, that air is composed of two gases,—oxygen and nitrogen; therefore, when we breathe, we send into our lungs oxygen and nitrogen. You might think, when we throw out this air, when we exhale,—you might think, I say, that this air coming out of our lungs is still composed of oxygen and of nitrogen in the same proportions. Now, it is not so at all. The quantity of nitrogen has not varied, but, in the first place, there is less oxygen, and there is another gas,—carbonic acid gas; where, then, is the oxygen which we have not exhaled, and whence comes this carbonic acid which we did not inhale? Then, besides, in the air exhaled there is vapor. Where does that come from? These phenomena result from the combustion of which I speak; but, in order that you should understand how this combustion occurs, I must explain to you what is oxygen and what is nitrogen. And as it is a long story, you must let me put it off till this evening; then I will talk until you are weary, my dear little Miette."
Miette looked at Albert and Paul, and answered for them with remarkable frankness:
"It will be only right if you do weary us. It is we who asked you, and, besides, we have so often wearied you that it is only right you should have your revenge on us. Still——"
"Still, what?"
"Still, we can trust you," added Miette, laughing, and throwing her arms around Roger's neck.