When Rollo went out into the kitchen that evening to get his safety lamp,—the one which he usually took to go to bed,—he found Jonas sitting at the kitchen table reading; and while he was lighting his lamp, he asked Jonas if he would not get him some iron filings the next time he went near any blacksmith’s shop. Jonas asked him what he wanted of iron filings, and he said he wanted them to burn. He then repeated to him what his father had said in respect to the combustibility of iron.

“I can make iron filings enough for that experiment in five minutes,” said Jonas.

“How?” said Rollo.

“With a file,” replied Jonas.

“Well,” said Rollo; and without waiting to hear anything further, he ran back to the parlor to ask his mother to let him sit up long enough to see Jonas make a few iron filings to try the experiment.

“Won’t it do as well to-morrow morning?” asked his mother.

“The scintillations will look brighter in the evening,” said Mr. Holiday.

“Very well, then,” added his mother, “go, and, if Jonas succeeds in his experiment, ask him to send some filings in to us.”

So Rollo went out to find Jonas again. Jonas was gone. Dorothy said that he had gone after a file. In a few minutes he returned, with a file in one hand, and a large iron spike in the other.

“What is the spike for?” asked Rollo.

“Only for a piece of iron to file,” replied Jonas. So saying, he took a small piece of paper out of a drawer, and laid it upon the table. Then he rested one end of the spike upon the paper, and, holding the other end in his hand, he filed it several times in such a way, that the filings fell down upon the paper.

“What fine filings!” said Rollo.

“Yes,” said Jonas; “the file is almost worn out, and it does not cut very well.”

Rollo looked upon the paper. There were quite a number of small, black points upon it like grains of very fine sand. Jonas then took up the paper carefully by the two sides, bending the two sides upward at the same time, to keep the filings in the middle of the paper. In this way he raised the paper above the lamp, which was upon the table before him, and then holding it in an inclined position, he let the sand slide down into the flame of the lamp. To Rollo’s surprise and delight, it produced a column of sparkles rising up from the flame, which were of the greatest brilliancy and beauty.

“Yes,” said Rollo, “they burn, they burn most beautifully. File me some more, Jonas, and let me carry them in and show them to my mother.”

Jonas accordingly filed some more filings, and Rollo went in with them very eagerly, to show to his mother.

“Just look,” said Rollo; and so saying, he held the paper over the lamp in such a manner as to let the filings slide down into the flame just as Jonas had done. The experiment succeeded perfectly well, as it had done before.

“So you see that it will burn,” said Mr. Holiday, “if you heat it hot enough.”

“If you make it small enough, you mean,” said Rollo.

“I suppose the smallness of the particles is of no consequence,” replied his father, “excepting to make it easier to heat them.”

“Why, father,” said Rollo, “I might put the end of a knitting-needle in the lamp, and I don’t see why it wouldn’t become as hot as one of the iron filings.”

“Because,” said his father, “a part of the heat would be conveyed away through the knitting-needle towards your hand, and that would keep the end which was in the flame cooler.”

“Would it, sir,” asked Rollo.

“Yes,” said his father. “The heat moves off very fast in such a case. You know, if you take a pin between your fingers, and hold the head of it in the lamp, the heat will almost immediately move along the metal, so as to heat the end that you are holding, and burn you.”

“Yes, sir,” said Rollo; “I have got burned so, very often.”

“And of course much more heat would be conveyed away when the metal was as thick as a knitting-needle.”

“Well, father,” said Rollo, “suppose a piece of the knitting-needle was broken off, and made so small that it could all be in the flame; then would it burn?”

“How could you keep it there?” asked his father.

“Why—I don’t know,” said Rollo, hesitating. “Couldn’t we contrive some way to keep it there?”

“I don’t know of any way.”

“Couldn’t we put it on the end of the wick?” asked Rollo.

“Yes,” said his father, “perhaps we might; but then the end of the wick is cool, and that would cool it.”

“O, father,” said Rollo, in a tone of great surprise, “the end of the wick cool, when it is right in the middle of the blaze!”

“I mean,” replied his father, “that it is cool compared with the heat necessary for inflaming the iron. It would feel very hot to your fingers, I have no doubt, for it is filled with boiling oil. But then even the heat of boiling oil is less than that necessary to inflame iron; and so the contact of the wick with such a piece of iron as you propose, would keep it cool, or rather keep it from getting hot enough to take fire.”

“Suppose there was any way,” said Rollo’s mother, “of suspending a piece of iron as large as the end of a knitting-needle in the lamp; do you think it would take fire?”

“No,” said Mr. Holiday, “I don’t think it would be heated hot enough. For some reason or other, I don’t understand exactly what, a large piece of iron cannot be heated very hot in a small fire, even if the fire entirely covers it. I don’t think that any fragment of iron much larger than one of Jonas’s filings could be heated in a lamp so as to take fire. But it could be heated hot enough in a forge. The end of the iron which a blacksmith heats is often in a state of combustion when he takes it out of the fire.”

“There, now, father,” said Rollo, “you have not explained to me yet about combustion and burning.”

“No,” said his father; “we had almost forgotten that. I will explain it now. It will only take a few minutes. Let me see—I began to tell you didn’t I?”

“Yes, sir,” said Rollo; “but I couldn’t understand very well.”

“I was telling you that the language which we use in common conversation is not precise. It is often ambiguous.”

“What does that mean, sir?” said Rollo.

“Why, language is ambiguous when it has two meanings,” said his father. “For instance, the word burning is used in conversation to express two or three very different things. If you put your finger upon hot iron, you say you have burned it. Burn, in that case, is the name of a painful feeling. But if you say you burned a piece of paper, you mean that you put it into the fire, and allowed it to be consumed. In that case, burning, instead of being the name of a painful feeling, is the name of a peculiar process by which the paper is consumed and destroyed. Thus the word burn is used to denote two very different effects. In fact, it is used in other senses besides these.”

“What others, sir?” asked Rollo.

“Why, when we say that a little girl was out in the sun, and burned her face and neck, we do not mean that her face and neck were consumed, or that they felt a painful sensation,—but that the skin was reddened by the sun’s heat. So, when we say that the grass was all burned up in the drought, we mean that it was dried and withered. Thus burned and burning are used to denote a great variety of effects produced by heat, which effects are very different from each other in their nature. So that, you see, when we are going to speak philosophically of that peculiar process by which bodies are actually consumed by fire, it becomes necessary to have some term to denote that process alone, and not all the other kinds of burning. Now, the word the philosophers use for this purpose is combustion. The burning of a stick of wood upon the fire is combustion, but the burning of your finger against a hot iron is not combustion, and the burning of bricks in a brick kiln is not combustion.”

“Nor the burning of the grass in the drought,” said Rollo.

“No,” said his father. “Thus you see that combustion is a term of precise and definite meaning; it denotes a particular process, and that alone. But burning is a vague and ambiguous term; it has a great many meanings, or, rather, it stands for a great many different effects, very much unlike in their character. In fact, they seem to be alike in no respect, except that they are all produced by heat.”

“Yes, father,” said Rollo, “I understand.”

“Sometimes,” added his father, “the word used in common life doesn’t mean enough, instead of meaning too much. For example, there is the word freeze. What is the meaning of the word freeze?”

“Why, it means,” said Rollo,—“freeze?—it means—water turning into ice.”

“Yes,” replied his father; “when water is cooled below a certain point, it becomes solid. It is just so with lead. Melted lead, when it is cooled below a certain point, becomes solid. The hardening of the melted lead into solid lead, and the hardening of water into ice, as they cool, seem to be phenomena of precisely the same character, and yet the word freeze applies only to one. We say the water freezes, but we can’t say the lead freezes.”

“Why not, sir?” asked Rollo.

“Because it is not the customary use of the word. If we use the terms of common life, we must use them as they are customarily used, or we shall not be understood. Freezing, therefore, will not answer to express all cases of the hardening of a liquid by cold, because that is a term which is only applied to a few of the cases. Now, philosophers want a term which will apply to all the cases of the same kind.”

“And what is their word?” asked Rollo.

“Congelation,” replied his father.

“Congelation?” repeated Rollo.

“Yes,” said his father. “When water becomes ice, the philosophers say it congeals. So when lead hardens in cooling, they say it congeals. Different substances congeal at very different degrees of heat. If we had melted iron and melted lead, equally hot, and let them cool together, the iron would congeal first; and if they continued cooling, by and by the lead would congeal. Water would remain liquid long after lead would congeal; but if it was placed where it would grow colder and colder, the temperature would at last reach the point where water would congeal too. But whatever the liquid is, and whatever the point is at which it changes from a liquid to a solid form, it is called congealing.”

“And the word freezing, then, is only used in respect to water,” said Rollo’s mother.

“Why, yes,” said Mr. Holiday; “we speak of other things freezing beside water; but it is only such things as become solid under great degrees of cold. We say ink freezes, and oil, and if it were cold enough to freeze brandy, or mercury, we should say they were frozen. But substances that harden when they are not very cold, as lead or wax, are not said to freeze.”

“Thus you observe,” continued Rollo’s father, “in common language words are not used in a precise and definite manner. Their meaning is determined by the outward and visible effects that we see, and not by the real nature of the causes. Thus a great many different effects are called burning, in common language, because they are all effects produced in various ways by heat. But the terms used by philosophers are definite and precise, each one being confined to one specific process or phenomenon.”

“Father,” said Rollo, “I want to see the iron filings burn again, and I am going out to ask Jonas to file a few more.”

“Very well,” said his father.

So Rollo went out to get Jonas to make him some more filings, and Jonas did so. Presently Rollo returned bringing the paper in very carefully, with the filings upon it. He put them down upon the table, and his father contrived, by bending the paper in different directions, to gather all the filings together into the middle of it, and then, with the point of his penknife, he took up a few of the filings at a time, and let them drop upon the flame of the lamp. The burning of the filings produced, as before, the most brilliant scintillations.

“What bright sparkles!” said Rollo.

“Yes, it is very inflammable indeed,” said his mother.

Here Mr. Holiday dropped more filings upon the flame, from the point of his knife.

“Does inflammable mean,” continued his mother, “that a thing takes fire easily, or that it burns with a great flame when it does take fire?”

“I don’t know,” said Mr. Holiday; “I never thought of that distinction. Some things take fire very easily, but don’t make a great flame. There’s sulphur, for instance; it takes fire before it gets very hot, but it burns with a very small and faint flame.”

“Let us try it, father,” said Rollo.

“We can’t try it very well, because there is no fire. I suppose the fire in the kitchen is covered up. But if there was a fire, and we were to put a little sulphur upon a shovel, and a small piece of paper by the side of it, and hold them over the fire, we should find that the sulphur would take fire before the paper would even begin to be scorched; but it would make only a very small blue flame. The paper would not take fire nearly as easily; but we should find that when it did take fire, it would make a much larger and brighter flame.”

“I wish you would try it, father,” said Rollo; “you can uncover the coals in the kitchen, and find fire enough.”

“Well,” said his father, “I will.”

His father accordingly rose from his seat, and asked Rollo to go into the kitchen, and get the shovel, and bring it to the medicine closet. While Rollo was getting the shovel, his father went to the closet, and took down a little jar half filled with sulphur. When Rollo brought him the shovel, he took out a little of the sulphur upon the point of his knife, and laid it upon the shovel. He also took a small piece of paper, and laid it upon the shovel by the side of the sulphur. Rollo then led the way to the kitchen, followed by his father with the shovel, and his mother came behind.

They opened the coals a little, and placed the shovel upon them. Jonas and Dorothy looked on with great interest, wondering what they were going to do. The sulphur began to melt almost immediately after the shovel was placed upon the coals; and, in a very short time, Rollo observed a faint blue spot on the place where the sulphur had been lying.

“There,” said his father, “see what a small flame.”

“Yes,” said Rollo; “it is nothing but a little blue spot.”

“And the paper is just as whole and white as ever it was.”

“Let us wait till the paper gets hot enough to burn.”

“I don’t think it would ever get hot enough to burn,” replied his father, “over such a fire as that. I must light it in the lamp.” So he waited a few minutes until the sulphur was entirely consumed, for he said that he did not wish to have any of the fumes get into the room; and then he dropped the paper off from the shovel down upon the hearth, and Rollo picked it up. His father lighted it in the lamp, and then placed it upon the shovel to see it burn, in order that Rollo might compare the magnitude of the flame which was produced with that of the sulphur. Of course, such a small piece of paper did not make a large flame, but it was four or five times as large as that produced by the sulphur.

“Now the question is,” said Mr. Holiday, “which is most inflammable,—the sulphur, because it inflames most easily, or the paper, because it makes the greatest flame when it does take fire?”

“I should think the paper,” said Rollo.

“There is alcohol,” said Mr. Holiday, “which takes fire very easily, but it burns with a very pale and light flame. Oil must be heated much hotter before it will burn; but, when it does burn, it gives a large and bright flame; so that oil is good for lamps, it gives so much light when it burns.

“Spirits of turpentine,” continued Mr. Holiday, “inflames easily, and burns brightly too. So does phosphorus.”

“What is phosphorus?” said Rollo.

“Why, it is a substance that burns very easily. It looks like wax, but it burns very easily, and with a very bright flame indeed. It takes fire before it is as hot as boiling water.”

“I wish I had some phosphorus,” said Rollo.

“They keep it at the apothecaries, sometimes,” said his father.

“I wish you’d buy a little, father,” said Rollo, “and bring it home, and let me see it burn. Does it cost much?”

“I don’t know,” said his father, “how much it costs. Only it is troublesome to keep it. It must be kept under water.”

“Why, sir?” said Rollo.

“To keep it from taking fire. Even the sun shining upon it would heat it hot enough to set it on fire.”

“O father!” said Rollo.

“Yes,” said his father; “and so, for safety, they make it in the shape of sticks, and keep it in a phial filled with water.”

“Well, father,” said Rollo, “I wish you would get a little in a phial, and let me put a piece of it upon a paper in the sun, and let me see it catch fire.”

“I’ll think of it,” said his father, “next time I go into town. But phosphorus, you see, is certainly very inflammable, because it takes fire very easily, and burns brightly too. But I don’t know which would be said to be most inflammable, sulphur or resin; for instance, sulphur inflames the quickest, but resin will make altogether the greatest blaze.”

“I should think the resin,” said Rollo.

“We can’t tell by reasoning about it,” said his father; “it depends on the usage of the word. We will go into the other room, and look in the dictionary.”

So saying, they all went into the parlor again, and looked into the dictionary, to learn the precise meaning of the word, inflammable. The definition given was, “easily kindled into a flame.”

“Then,” said Mr. Holiday, “if this definition is correct, the sulphur and the alcohol are most inflammable, because they are most easily kindled.”

Just then the clock struck, and Rollo’s mother said,—

“Why, Rollo, it is half an hour past your bedtime.”

So Rollo bade his father and mother good night, and went out into the kitchen once more to get his safety-lamp, to go to bed. He stopped, however, a moment, as he was going out of the door, to say,—

“Now, father, be sure and not forget to buy me some phosphorus.”

QUESTIONS.

What did Jonas say when Rollo told him about burning the iron filings? How did he make the filings? Did the experiment of burning them succeed? Why will not a large piece of iron burn in the flame of a lamp? What did Mr. Holiday say to Rollo’s proposal to hold the end of a knitting-needle in the lamp? Why will not the terms that are employed in common conversation answer for philosophical use? What is the meaning of ambiguous? What are the different meanings of the word burn? What is the difference between the words freeze and congeal in respect to the extent of their meaning? What question did Rollo’s mother ask in respect to the meaning of the word inflammable? What did Mr. Holiday say? What experiment did he perform to illustrate the two meanings? How was the question at last decided?