For a moment Monsieur Dalize was disconcerted, and knew not what to say in answer. Happily, Monsieur Roger came to his aid. He took the book from Miette's hands, looked at the engraving, and said, quietly,—

"Why, certainly, my dear young friend, the gentleman who made that drawing ought to know something about chemistry and physical science."

"How so?" said Miette, astonished.

"Why, if he did not know the laws of physical science and of chemistry, he has, none the less, and perhaps even without knowing it himself, availed himself of the results of chemistry and physical science."

Miette took the book back again, looked at the drawing with care, and said,—

"Still, there are not in this drawing instruments or apparatus, or machines such as I have seen in my brother's books."

"But," answered Monsieur Roger, smiling, "it is not necessary that you should see instruments and apparatus and machines, as you say, to be in the presence of physical phenomena; and I assure you, my dear child, that this drawing which is under our eyes is connected with chemistry and physical science."

Miette now looked up at Monsieur Roger to see if he was not making fun of her. Monsieur Roger translated this dumb interrogation, and said,—

"Come, now! what does this drawing represent? Tell me yourself."

"Why, it represents two peasants,—a man and a woman,—who have returned home wet in the storm, and who are warming and drying themselves before the fire."

"It is, in fact, exactly that."

"Very well, sir?" asked Miette.

And in this concise answer she meant to say, "In all that, what do you see that is connected with chemistry or physical science?"

"Very well," continued Monsieur Roger; "do you see this light mist, this vapor, which is rising from the cloak that the peasant is drying before the fire?"

"Yes."

"Well, that is physical science," said Monsieur Roger.

"How do you mean?" asked Miette.

"I will explain in a moment. Let us continue to examine the picture. Do you see that a portion of the wood is reduced to ashes?"

"Yes."

"Do you also remark the flame and the smoke which are rising up the chimney?"

"Yes."

"That is chemistry."

"Ah!" said Miss Miette, at a loss for words.

Every one was listening to Monsieur Roger, some of them interested, the others amused. Miette glanced over at her friend Paul.

"What do you think of that?" she asked.

Paul did not care to reply. Albert wished to speak, but he stopped at a gesture from his father. Monsieur Dalize knew that the real interest of this scene lay with Monsieur Roger, the scientist, who was already loved by all this little world. Miette, as nobody else answered, returned to Monsieur Roger.

"But why," she asked, "is that physical science? Why is it chemistry?"

"Because it is physical science and chemistry," said Monsieur Roger, simply.

"Oh, but you have other reasons to give us!" said Madame Dalize, who understood what Monsieur Roger was thinking of.

"Yes," added Miette.

And even Paul, with unusual curiosity, nodded his head affirmatively.

"The reasons will be very long to explain, and would bore you," said Monsieur Dalize, certain that he would in this way provoke a protest.

The protest, in fact, came.

Monsieur Roger was obliged to speak.

"Well," said he, still addressing himself to Miss Miette, "this drawing is concerned with physical science, because the peasant, in placing his cloak before the heat of the fire, causes the phenomenon of evaporation to take place. The vapor which escapes from the damp cloth is water, is nothing but water, and will always be water under a different form. It is water modified, and modified for a moment, because this vapor, coming against the cold wall or other cold objects, will condense. That is to say, it will become again liquid water,—water similar to that which it was a moment ago; and that is a physical phenomenon,—for physical science aims to study the modifications which alter the form, the color, the appearance of bodies, but only their temporary modifications, which leave intact all the properties of bodies. Our drawing is concerned with chemistry, because the piece of wood which burns disappears, leaving in its place cinders in the hearth and gases which escape through the chimney. Here there is a complete modification, an absolute change of the piece of wood. Do what you will, you would be unable, by collecting together the cinders and gases, to put together again the log of wood which has been burned; and that is a chemical phenomenon,—for the aim of chemistry is to study the durable and permanent modifications, after which bodies retain none of their original properties. Another example may make more easy this distinction between physical science and chemistry. Suppose that you put into the fire a bar of iron. That bar will expand and become red. Its color, its form, its dimensions will be modified, but it will always remain a bar of iron. That is a physical phenomenon. Instead of this bar of iron, put in the fire a bit of sulphur. It will flame up and burn in disengaging a gas of a peculiar odor, which is called sulphuric acid. This sulphuric-acid gas can be condensed and become a liquid, but it no longer contains the properties of sulphur. It is no longer a piece of sulphur, and can never again become a piece of sulphur. The modification of this body is therefore durable, and therefore permanent. Now, that is a chemical phenomenon."

Monsieur Roger stopped for a moment; then, paying no apparent attention to Paul, who, however, was listening far more attentively than one could imagine he would, he looked at Miette, and said,—

"I don't know, my child, if I have explained myself clearly enough; but you must certainly understand that in their case the artist has represented, whether he wished to or not, the physical phenomenon and the chemical phenomenon."

"Yes, sir," answered Miette, "I have understood quite well."

"Well," said Monsieur Dalize, "since you are so good a teacher, don't you think that you could, during vacation, cause a little chemistry and a little physical science to enter into that little head?" And he pointed to Paul Solange.

The latter, notwithstanding the sentiment of respectful sympathy which he felt for Monsieur Roger, and although he had listened with interest to his explanations, could not prevent a gesture of fear, so pronounced that everybody began to laugh.

Miette, who wished to console her good friend Paul and obtain his pardon for her teasing, came up to him, and said,—

"Come, console yourself, Paul; I will let you take my portrait a dozen times, as you did last year,—although it is very tiresome to pose for a portrait."