What was the first experiment with the bellows, described in this chapter? Why could not Nathan press the two sides of the bellows together, while the nose was stopped? What was the second experiment? What was the effect produced by turning the bellows bottom upwards, as in the third experiment? What was the fourth experiment? What was the use of the smoke of the paper? How were the experiments interrupted? What evidence did Rollo and Nathan have that the air was a real substance, when in the barn chamber?
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Oneevening, just after tea, Rollo came to his father, who was sitting by the side of the fire, and said,—
"Father, I wish we could see the air, as we can the water, and then perhaps we could try experiments with it."
"O, we can try experiments with the air as it is," said his father.
"Can we?" said Rollo; "I don't see how."
"We cannot see the air, it is true; but then we can see its effects, and so we can experiment upon it."
"Well, at any rate," said Rollo, "we can't build a dam, and make it spout through a hole, like water."
"No," said his father, "not exactly. In your dam, for instance, when it was full, you had water on one side of the board, and no water on the other; and then, by opening ahole in the board, the water spouted through; but we cannot very well get air on one side of a partition, and no air on the other; if we could, it would spout through very much as the water did."
"Why can't we do that, sir?" said Rollo.
"Because," replied his father, "we are all surrounded and enveloped with air. It spreads in every direction all around us, and rises many miles above us. Whereas, in respect to water, you had one little stream before you, which you could manage just as you pleased. If you were down at the bottom of the sea, then the water would be all around you and above you; and there, even if you could live there, you could not have a dam."
"No, sir," said Rollo, "the water would be everywhere."
"Yes," replied his father, "and the air is everywhere. If, however, we could get it away from any place, as, for instance, from this room, then bore a hole through the wall, the weight of the air outside would crowd a portion of it through the hole, exactly as the weight of the water above the board in yourdam crowded a part through the hole in the board."
"I wish we could try it," said Rollo.
"Wecantry it, in substance," said his father, "in this room; or—no, the china closet will be better."
There was a china closet, which had two doors in it. One door opened into the parlor, where Rollo and his father were sitting. The other door opened into the back part of the entry. Rollo's father explained how he was going to perform the experiment, thus:—
"If we could, by any means, get all the air out of the closet for a moment, then the pressure of the air outside would force a jet of it in through the key-holes of the doors, and the crevices."
"And how can we get the air out?" said Rollo.
"We can't," said his father, "get it all out; but we can get a part of it out by shutting the door quick. The door will carry with it a part of the air that was in the closet, and then the outside air will be spouted in, through the key-hole of the other door. Only we can't see it, as we can the water."
"No," said Rollo; "but I can put my hand there, and feel it."
"A better way," said his father, "would be to hold a lamp opposite to the key-hole, and see if it blows the flame."
Rollo tried the experiment, in the way his father had described. He went into the closet with the lamp. He held the lamp opposite to the key-hole, and pretty near to it, and then he asked Nathan to shut the other door suddenly. Nathan, who was standing all ready by the other door, which was about half open, put his two hands against it, and pushed it to, with all his strength, producing a great concussion.
"O Nathan," said his father, "you need not be quite so violent as that."
"It succeeded, father, it succeeded," said Rollo.
"I'm glad it succeeded," said his father; "but Nathan need not have shut the door with so much force."
"I wanted to drive out all the air," said Nathan.
"I'll show you how to do it," said his father.
Rollo's father accordingly arose, and cameto the closet door. He opened the door wide, and then explained to the boys, that the beginning of the movement of the door, when it was wide open, did not drive out any air.
"For," said he, "there is so large a space between the edge of the door and the wall, that the air that is put in motion by the movement of the door, can pass directly round the edge, back into the closet again. It is only when the door is almost shut, when the edge of it comes close to the casing all around, that the movement of the door drives the air out."
Then he took hold of the latch of the door, and put it almost to, very gently. He turned the latch so as to prevent its snapping against the catch, and then pushed it suddenly into its place three or four times, opening the door only a very little way every time.
"Now," said he, "hold the lamp at the key-hole, and watch the flame, while I shut the door two or three times in this way."
Rollo did so, Nathan standing all the time by his side. They observed that the flame of the lamp was driven into the room every time the door was shut; proving that,every time a little of the air was driven out by the door, a little puff rushed in at the key-hole.
"Let us stop up the key-hole," said Rollo, "and then it can't get in."
"Yes," said his father, "there are a great many little crevices all around the closet, where the air can come in."
"Couldn't we stop those up too?" said Rollo.
"No," said his father, "not so as to make the closet air-tight. For, if the crevices could all be stopped exactly, the air would come in through the very wood itself."
"How?" said Rollo.
"Why, there are little pores in wood, that is, little channels that the sap flowed in when the wood was growing, and the air can pass through these."
Here Rollo's father observed that Rollo was looking very intently at the table; and he asked him what he was doing: he said he was trying to find some of the pores.
"You can't see them there," said his father. "St. Domingo mahogany is a very hard and close-grained kind of wood. If it was summer, and you could dig down andget a small piece of the root of the great elm-tree in the yard, you could see the pores and channels there."
After some more conversation on this subject, Rollo asked his father if he could not think of some other experiments for them to try. His father said that he did not just then think of any experiment, but that, if Rollo and Nathan would come and sit down by the fire, he would give them some information on the subject. Rollo's mother said that she should like to hear too. They accordingly waited until she was ready, and then, when all were seated, Mr. Holiday began thus:—
"Air is in many respects much like water."
"Yes," interrupted Rollo, "just like water, only thinner, because, you see——"
"You must not interrupt me," said his father, "unless to ask some question, which is necessary to understand what I say. It is entirely irregular for a pupil, instead of listening to his teacher, to interrupt, in order to tell something that he knows himself."
Rollo's father smiled, as he said this, but Rollo looked rather ashamed. Then his father proceeded:—
"There is one very remarkable difference between them. Water is not compressible by force; but air is."
"What is the meaning ofcompressible?" said Nathan.
"Compressible things," said his father, "are those that can be compressed, that is, pressed together, so as to take up less room than they did before. Sponge is compressible. A pillow is compressible. But iron is not compressible, and water is not compressible."
"I should think it was," said Nathan; "it is very soft."
"It is veryyielding," replied his father, "when you press it, but it is not pressed into any smaller space. It only moves away. If you have a tumbler half full of water, and press a ball down into it, you could not crowd the water into any smaller space than it occupied at first; but, as fast as the ball went down, the water would come up around the sides of the ball."
"But suppose," said Rollo, "that the ball was just big enough to fit the tumbler all around; then the water could not come up."
"And then," said his father, "you could not crowd the ball down."
"Could not averystrong man?" said Nathan.
"No," replied his father, "the water cannot be sensibly compressed. But now, if the tumbler contained only air, and if a ball were to be put in at the top, just large enough to fit the tumbler exactly, and if a strong man were to crowd it down with all his strength, he would, perhaps, compress the air into half the space which it occupied before."
"Perhaps the tumbler would break," said Nathan.
"Yes," replied his father, "and the tumbler will answer only for a supposition; but for a real experiment it would be best to have a cylinder of iron."
"What is a cylinder?" said Nathan.
"An iron vessel, shaped like a tumbler, only as large at the bottom as it is at the top, would be a cylinder. Now, if there was a cylinder of iron, with the inside turned perfectly true, and a brass piston fitted to it——"
"What is a piston?" said Nathan.
"A piston," said his father, "is a sort of stopper, exactly fitted to the inside of a cylinder, so as to slide up and down. It is made to fit perfectly, and then it is oiled, so as togo up and down without much friction, that is, hard rubbing. There is a sort of stem coming up from the middle of the piston, called the piston rod, which is to draw up the piston, and to press it down by.
"Now," continued his father, "if a strong man had a cylinder like this, with a piston fitted to it, and a strong handle across the top of the piston rod, perhaps he might press the air into one half the space which it occupied before. That is, if the cylinder was full of air when he put the piston in, perhaps he could get the piston down half way to the bottom. Then the air would be twice asdenseas it was before; that is, there would be twice as much of it in the same space as there was before. It would be twice as compact and heavy. This is calledcondensingair. The philosophers have ingenious instruments for condensing air.
"If, however, a man condenses air in this way, by crowding down a piston, he does not begin the condensation when the piston begins to descend. The air is condensed a great deal before he begins. All the air around us is condensed."
"How comes it condensed?" said Rollo.
"Why, you recollect that, when you bored a hole through the board in the bottom of your dam, the water spouted out."
"No, father," said Rollo, "we pulled the plug out; Jonas bored the hole."
"Well," said his father, "the water spouted out."
"Yes," said Rollo.
"What made it?" said his father.
"Why, the water above it was heavy, and pressed down upon it, and crowded it out through the hole."
"Yes," said his father, "and the deeper the water, the more heavily it was pressed."
"Yes, sir," said Rollo, "and the farther it spouted."
"Because it was pressed down by the load of such a high column of water."
"Yes, sir," said Rollo.
"Well," replied his father, "it is just so with the air. The air all around us is pressed down by the load of all that is above us. We are, in fact, down at the bottom of a great ocean of air, and the air here is loaded down very heavy."
"How heavy?" said Rollo.
"O, very heavy indeed," said his father.
"Why, air is pretty light," said Rollo.
"Yes," replied his father, "but then the column of it is very high."
"How high?" said Rollo.
"Why, between thirty and forty miles. But it grows thinner and thinner towards the top; so it is not as heavy, by any means, as a column of air would be, thirty miles high, and as dense all the way up as it is here."
"What makes it grow thinner and thinner towards the top?" said Rollo.
"Because," said his father, "that which is near the top, has not as much load of air above it, to press it down."
"And that which isatthe top," said Rollo, "has none above it, to press it down."
"No," replied his father.
"And how thin is it there?"
"Nobody knows," said his father.
"What, nobody at all?" said Nathan.
"No, I believe not; at least I do not; and I don't know that any body does."
"How do they know, then, how high it is?" said Rollo.
"The philosophers have calculated in some way or other, though I don't exactly know how. I believe they have ascertainedhow great the pressure of the air is here at the surface of the earth, and have calculated in some way, from that, how high the air must be to produce such a pressure."
"And how high must it be?" said Nathan.
"Why, between thirty and forty miles," said Rollo; "father told us once."
"And yet," continued his father, "water, thirty or forty feet deep, would produce as great a pressure as a column of air of thirty or forty miles. That is, the air around presses about as heavily, and would force a jet of air through a hole with about as much force, as water would, coming out at the bottom of a dam, as high as a common three-story house."
These explanations were all very interesting to Rollo and to his mother; but Nathan found it rather hard to understand them all, and he began to be somewhat restless and uneasy. At length he said,—
"And now, father, haven't you almost done telling about the air?"
"Why, yes," said his father; "I have told you enough for this time; only you must remember it all."
"I don't think I can remember it quite all," said Nathan.
"Well, then, remember the general principle, at any rate," said his father, "which is this—that we live at the bottom of a vast ocean of air, and that the lower portions of this air are pressed down by the load of all the air above; that, being so pressed, the lower air is condensed,—so that we live in the midst of air that is pressed down, and condensed, by the load of all that is above it; and that, consequently, whenever the air is taken away, even in part, from any place, as you removed some of it from the china closet, the pressure upon the air outside forces the air in through every opening it can find."
"I think that is a little too much for me to remember," said Nathan.
Nathan's father and mother laughed on hearing this, though Nathan did not know what they were laughing at. His father told him that he could not expect him to remember all; and that, to pay him for his particular attention, he would tell him a story.
So he took Nathan up in his lap, and toldhim a very curious story of a boy, who went about the yard with a little dog upon one of his shoulders, a cat upon the other, and a squirrel on his head. The squirrel was tame.
Why cannot experiments be performed upon the pressure of air, as conveniently as upon the pressure of water? How did Rollo's father contrive to remove a part of the air from the china closet? Where did they expect that the air would be forced into the closet? How were they to make this effect visible? Did the experiment succeed? Suppose the key-hole had been stopped up; where would the air have been forced in? Suppose all the crevices had been closed. Is water compressible? Is air compressible? What is the shape of a cylinder? What is a piston? How might air be compressed by means of a cylinder and piston? What was the general principle which Rollo's father stated, in conclusion?
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Thenext evening, Rollo and Nathan had another conversation with their father, respecting air. When they were all seated, he commenced as follows:—
"I told you yesterday, that air may be compressed by force, while water cannot be. It has another property, which is in some respects the reverse of this. It springs back into its original bulk, when the pressure is removed."
"How?" said Nathan; "I don't exactly understand you."
"Why, you remember what I said about the experiment with the iron cylinder and a piston to fit it."
"Yes, sir," said Rollo.
"What was the experiment?" said his father.
"Why, if a man were to press the pistondown hard, he could crowd the air all into the lower half of the cylinder."
"Yes," replied his father. "Now, the property I am going to tell you about this evening is this—that, if the man lets go of the piston rod, the air that is condensed into the bottom of the cylinder, will spring up, and force the piston up again. This property is calledelasticity. It is sometimes called theexpansive forceof the air. For it is a force tending to expand the air, that is, to swell it out into its original dimensions. This is another great difference between air and water.
"Now, as all the air around us," continued Rollo's father, "is pressed down very heavily, and is condensed a great deal, it is all the time endeavoring to expand; and it would expand, were it not that the great burden of the air above it keeps it condensed. But water is not compressed, and has no tendency to expand. The water of Rollo's dam, for instance, had all the weight of the atmosphere resting upon it, but it did not compress it at all, and so it did not tend to expand.
"And now," said his father, "I cannotperform any experiment, to show you that air tends strongly to expand or swell out into a great space, while water does not; but I can make a supposition, which will illustrate it. Suppose we had a large, but very thin, glass bottle, filled with water, and put down upon the floor in the middle of this room. Suppose, also, that we had another bottle, of the same size and shape, filled with air, and we put that down upon the floor by the side of the other; both bottles being stopped very tight. Now, if we could by any means suddenly take away all the air from the room, so that there should be nothing around the bottles, then the bottle of water would remain just as it is, for the glass would have nothing to support but the weight of the water, and it would be strong enough for that. But the bottle of air would fly all to pieces; for that would not rest quietly, like the water, satisfied with the space which it already has, and only pressing with its own weight upon the sides of the glass; but it would immediately expand with so much force as to break the thin glass all to pieces."
"Would it!" exclaimed Rollo and Nathantogether. "And would it make a loud noise?"
"Yes," replied their father, "I presume it would make a loud explosion; that is, if the air in the room around it could by any means be all at once and suddenly removed.
"And so you must remember," he continued, "that there are two very remarkable differences between air and water. Air may be condensed by pressure, and, as it exists all around us, is greatly condensed by the pressure of the air above, and it may be compressed more. And air is expansive, while water is not. Whenever the pressure upon it is removed, it suddenly expands, or spreads out in all directions."
"O dear me!" said Nathan, with a sigh.
"What is the matter?" said his father.
"Why, I can't understand it very well."
"Can't you?" said his father. "Well, I must admit that you are rather too young to study pneumatics."
"Pneumatics?" repeated Rollo.
"Yes," said his father; "that is the name of this science."
"Then it sailed slowly away."—Page 85.
"What, the science of air?" said Rollo.
"Yes," said his father, "the science which treats of air, and of all other compressible and expansive fluids. But let me think. I must try to tell you something which Nathan can understand and be interested in. If I had a very light feather, I could let him perform an experiment."
"Would a little down do?" said Rollo's mother.
"Yes," replied his father, "that would be better than a feather."
Mrs. Holiday then went and brought a little down, and handed it to Rollo's father. Now, there was a lamp upon the table, of a peculiar kind, called a study lamp. It had a glass tube, called a chimney, around the wick, and consequently around the flame itself, being round, like a ring.
Rollo's father told Nathan to hold the down over the top of this glass chimney, and then to let it go.
Nathan did so. The little tuft of down was wafted up into the air, quite high above the lamp, andthen it sailed slowly away, and fell down upon the table.
"I know what makes it rise," said Rollo. "It is the heat. The heat makes it rise."
"Do you think so?" said his father. "Then take the down, and lay it gently upon the hearth, before the fire, as near as you can."
Rollo did so. He had to take his hand away very quick, for it was quite hot there. The little tuft remained quietly upon the hearth where he placed it.
"There," said his father, "is not that a hotter place than it was over the lamp?"
"Yes, sir," said Rollo.
"Then, if it was heat that made it rise, why does not it rise now?"
Rollo could not tell.
"I will tell you how it was," said his father. "Heat makes air more expansive. When air is heated, it swells; when it is cool, it shrinks again. Now, if it swells, it becomes lighter, and so it is buoyed up by the heavier air around it; just as wood at the bottom of the sea would be buoyed up, and would rise to the surface of the water. Now, the heat of the lamp heats the air that is in the glass chimney, and swells it. Thismakes it lighter; and so the air around it, which is heavier, buoys it up, and it carries up the feather with it."
"No, the down, father," said Nathan.
"Yes, the down," said his father.
"Then it seems to me, after all," said Rollo, "that it is the heat which makes it rise."
"Yes," said his father, "it does, indirectly. It expands the air; that makes it lighter; then the heavy air around it buoys it up, and, when it goes up, it carries up the down. So that it is not strictly correct to say, that the heat carries it up. The heat sets in operation a train of causes and effects, the last of which results in carrying up the feather.
"Now," continued his father, "there is always a stream of air going up, wherever there is a lamp, or a fire, or heat, which heats the air in any way. The expanded air from a fire goes up chimney. The cool and heavy air in the room and out of doors crowds it up."
"The air out of doors?" said Rollo. "How can that crowd it up?"
"Why, it presses in through all the crevicesand openings all around the room, and crowds the light air up the chimney. All the smoke is carried up too with it, and it comes pouring out at the top of the chimney all the time."
"You can see that the air presses in at all these crevices," continued Rollo's father, "by experiment."
"What experiment is it?" said Rollo; "let us try it."
"I will let Nathan try it," said his father, "and you may go with him and see the effect. First," he continued, "you see by the smoke, that the air really goes up the chimney; and I will show you that other air really crowds into the space, from other parts of the room."
So he took a lamp from the table,—not the study lamp; it was a common lamp,—and held it at various places in the opening of the fireplace, by the jambs and near the upper part; and Rollo and Nathan saw that the flame, in all cases, was turned in towards the chimney.
"Yes," said Rollo, "I see it is drawn in."
"No," said his father; "strictly speaking, itis notdrawnin; it is pressed in, by the cool and heavy air of the room."
"I thought," said Rollo's mother, "that the chimneydrewthe air from the room into it."
"That is what is generally said," replied Mr. Holiday, "but it is not strictly true. The common idea is, that the hot air rises in the chimney, and so draws the air from the room to supply its place; but this is not so. In the first place, nothing can rise unless it is forced up. The lightest things have some weight, and would, if left to themselves, fall. The hottest and lightest air in a chimney would fall to the earth, if there was no cooler and heavier air around it, to force it to rise;—just as the lightest cork, which would rise very quick from the bottom of the sea, would fall back again very quick, if the water was not there.
"Remember, then, Nathan and Rollo, that, when a fire is built in a fireplace, so as to warm the air in the chimney, it makes this air not so heavy; and then the cool air all around it in the room and out of doors, presses in, and crowds under the light air, and makes it ascend."
"But, father," said Nathan, "you said I might perform an experiment."
"Very well, I am ready now. Take the lamp, and carry it around the room, and hold it opposite any little opening you can find."
"I can't find any little openings," said Nathan.
"O yes," said his father; "the key-hole of the door is a little opening, and there is a narrow crevice all around the door; and you will find little crevices around the windows. Now, hold the lamp opposite any of these, and you will see that the air presses in."
So Nathan went with the lamp, Rollo following him, and held the lamp opposite to the key-hole, and the crevices around the door and windows; only, when he came to the window, his father told him to be very careful not to set the curtain on fire.
Rollo wanted Nathan to let him try it once; and so Nathan gave him the lamp. He said he meant to make a crevice; and so he pushed up the window a very little way, and held the lamp opposite to the opening. The air pressed the flame in towards the room, in all cases.
"People commonly say, that it isdrawnin," said his father, "but that is not strictly correct; it is reallypressedin. There is no power of attraction, in the air that is in the room, to draw in the air that is out of doors, through the crevices; but the air that is out of doors, is so heavy, that it presses in, and crowds the warm and light air up the chimney.
"And now," said his father, "I cannot tell you anything more this evening; but, if you remember this, I will give you some further instruction another time."
"Well, sir," said Nathan, "only I wish you would tell me a little story, as you did last evening. Have not I been still?"
His father had noticed, that he had been very still and attentive, but did not think before, that it was in expectation of being rewarded with a story.
"Well," said his father, "I will tell you a story, or give you a little advice. How should you like a little advice?"
"Well, father, a little advice; just which you please."
"I advise you, then,—let me see,—what shall I advise you?—No, on the whole, Iwill tell you a story. Once there was a man, and he was a philosopher. He understood all that I have been explaining to you about the air being light when it was hot. So he got some very thin paper, and made a large paper bag. He cut the paper very curiously, and pasted it together at the edges in such a way, that the bag, when it was done, was round, like a ball; and it had a round opening at the bottom of it. In fact, it was a large paper ball."
"How large was it?" said Nathan.
"It was so large, that, when it was swelled out full, it would have been higher than your head."
"O, what a large ball!" said Nathan. "But what was it for?"
"Why, the man thought, as hot air is lighter than cool air, and floats up, that perhaps, if he could fill his paper ball with hot air, it would go up too."
"And did it?" said Nathan.
"Yes," said his father. "He filled it with hot air; and the hot air was so light, that it rose up and carried the paper ball with it."
"How did he get the hot air into it?" said Rollo.
"Why, he held it over a little fire, with the mouth down. Then the hot air from the fire went up into the ball, and swelled it out full."
"How high did it go?" said Nathan.
"O, it soared away," said his father, "away up into the air, very high; until at length it got cool, and then it came down."
"I should like to see such a ball as that," said Nathan.
"Such a ball as that is called aballoon," said his father.
"I wish I could see a balloon," said Nathan.
What is the important difference between air and water, which was explained in the last chapter, and mentioned in this? Does the air tend to expand again after it is compressed? What is this property of the air called? Is the air around us already condensed, or is it in its natural state? What causes it to be condensed? Suppose a thin glass vessel were to be filled with air, and another with water, and the air suddenly removed from the room around them; what would be the effects? What effect does heat have upon the expansibility of air? How may this effect be made to appear over a lamp? In a chimney? What was the story which Rollo's father told Nathan?
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Sometime after this, Rollo, and Nathan, and James, were playing in the shed, one pleasant morning in the spring. They were building with sticks of wood, which they piled in various ways, so as to make houses. They took care not to pile the wood, in any case, higher than their shoulders, for Jonas had told them that, if they piled the wood higher than that, there would be danger of its falling down upon them.
After some time, Rollo went into the house a few minutes, and James and Nathan went to the open part of the shed, and began to look out of doors. The sun was shining pleasantly, but the ground was wet, being covered with streams and pools of water, and melting snow-banks.
"What a pleasant day!" said James. "I wish it was dry, so that we could go out better."
"I wish we could fly," said Nathan, "for it is very pleasant up in the air."
"I wish we had a balloon," said James. "If we had a balloon, we could go up in the air, easier than to fly."
"O James," said Nathan, "you could not get into a balloon if you had one."
"Why not?" said James.
"Because," said Nathan, "it would not be big enough."
"Why, Nathan," said James, "a balloon is bigger than this house."
"O James, it is not higher than my head."
"It is," said James, "I know it is. I have read about balloons bigger than a house."
"And my father," said Nathan, putting down his foot in a very positive air, "my father told me himself, that a balloon was about as high as my head."
The boys disputed some time longer upon the subject, and finally, when Rollo came out of the house, they both appealed to him very eagerly to settle the dispute.
"Isn't a balloon higher than Nathan's head?" said James.
"Is it as high as a house?" said Nathan.
"Why, I know," said Rollo, "that a man made a balloon once about as high as Nathan's head, because my father said so; but perhaps it was a little one."
"Yes," said James, "I know it must be a little one; for balloons are big enough for men to go up in them."
"O James," said Nathan, "I don't believe it. Besides, the fire would burn 'em."
"What fire?" said James.
"The fire they burn under the balloons, to make the air hot," said Nathan.
"I don't believe they have any fire," said James.
Just then Nathan, happening to look around, saw Jonas standing behind them; he had just come out of the house, and was going out to his work. Hearing the boys engaged in this dispute, he stopped to listen. The boys both appealed to Jonas.
Jonas heard all that they had to say, and then replied,—
"I cannot tell you much about going up in a balloon, but I can tell you something about getting along pleasantly down here upon the earth, which I think may be of service to you."
"What is it?" said James.
"Why, that you will neither of you get along very pleasantly until you can bear to have any body else mistaken, without contradicting them. James, you think Nathan is mistaken about the size of a balloon, do you?"
"Yes, I know he is," said James.
"Well," said Jonas, "now why not let him remain mistaken?"
"Why,—I don't know," said James.
"He isn't willing to be convinced, is he, that a balloon is as big as a house?"
"No," said James, "he is not."
"Then why don't you let him remain unconvinced? Why should you insist on setting him right, when he don't want to be set right?"
"And you, Nathan, suppose that James is mistaken, in thinking that the balloon is so big."
"Yes," said Nathan, "and that men can get into it, and go up in the air."
"Well, now, if he wants to believe that balloons are so big, why are you not willing that he should? Why should you insistupon it that he should know that they are smaller?"
"Because Iknow," said Nathan, very positively, "that they are small; and, besides, the paper would not be strong enough to bear a man."
"I did not ask you," said Jonas, "whyyoubelieved that men could not go up in balloons, but why you were so anxious to make James believe so. Why not let him be mistaken?"
"Why—because," said Nathan.
"You see, Nathan," continued Jonas, "the world is full of people that are continually mistaken; and if you go about trying to set them all right by disputing them, you'll have a hard row to hoe."
"A hard what?" said Nathan.
"A hard row to hoe," repeated Jonas. "It's never of any service to attempt to convince people that don't want to be convinced; especially if they are wrong."
"Especially if they are wrong!" repeated Rollo, in astonishment.
"Yes," replied Jonas. "The very worst time to argue with a boy, is when he iswrong, and does not want to be set right. It is a great deal harder to get along in argument with one who is right, than with one who is wrong; for the one who is wrong, disputes; the one who is right, reasons."
"Well, Jonas," said James, "which of us was disputing?"
"Both of you," said Jonas.
"Both of us," said James; "but you said that only the one who was wrong, disputed."
"Well," replied Jonas, "you were both wrong."
"Both wrong! O Jonas!" said James.
"Yes, both wrong," replied Jonas; and so saying, he was going away to his work.
"But stop a minute longer," said James, "and tell us how it is about the balloon; we want to know."
"O no," said Jonas, "you don't want to know; you want toconquer."
"What do you mean by that?" said Nathan.
"Why, you don't really wish to learn any thing; but you want to have me decide the case, because each of you hopes that I shall decide in his favor. You want the pleasureof a victory, not the pleasure of acquiring knowledge."
"No, Jonas," said Nathan, "we do really want to know."
"Well," said Jonas, "I can't stop now to tell you; perhaps I will this evening; but I advise you always, after this, not to contradict people, and dispute with them, when they say things that you don't believe. Do as the gentleman did, when the man said the moon was a fire."
"What did he do?" said Rollo.
"Why, he let him say it as much as he wanted to."
"Tell us all about it," said James.
"Well, then," said Jonas, "once there was a man, and he saw the moon coming up behind the trees, and thought it was a large house burning up. He went along a little way, and he met a vulgar fellow, riding in a carriage."
"Riding in a carriage!" repeated Rollo, astonished.
"Yes," said Jonas, "handsomely dressed. 'Sir,' said the man, 'see that great fire!'
"'It isn't a fire, you fool,' said the vulgar fellow; 'it's nothing but the moon.'
"'The moon! no it isn't,' said the man; 'it is a monstrous great fire. Don't you see how it blazes up?'
"'It is not a fire, I tell you,' said the vulgar fellow.
"'I tell you 'tis,' said the man.
"'You don't know any thing about it,' said the vulgar fellow.
"'And you don't know the moon from a house on fire,' said the man, and so passed on.
"A minute or two after this, he met a gentleman driving a team."
"A gentleman driving a team!" said James.
"Yes," said Jonas, "with a frock on. He was tired and weary, having driven all day. The man asked him if he did not see that house on fire.
"'Ah,' said the gentleman, 'I thought it was the moon.'
"'No,' said the man, 'it is a house on fire.'
"'Well,' said the gentleman, 'I am very sorry if it is. I hope they'll be able to put it out!'
"So saying, he started his team along, and bade the man good evening."
Jonas then, having finished his story,stepped out of the shed, and went along towards the barn; Nathan called out after him to say,—
"Well, Jonas, I don't understand how the gentleman came to be driving a team all day."
Jonas did not reply to this, but only began to laugh heartily, and to walk on. Nathan turned back into the shed, saying, he did not see what Jonas was laughing at.
The boys wanted very much to have the question about the balloon settled; and, after some further conversation on the subject, they concluded to go in and ask their mother. So they all three went in. Rollo proposed this plan, and he led the way into the house. He found his mother sitting in the parlor at her work.
"Well, boys," said she, "have you got tired of your play?"
"No, mother," said Rollo, "but we want to know about balloons: how big are they?"
"O, some of them," said she, "are very large."
"Ain't they as big as this house?" said James.
"Yes, I believe they have been made as big," said she.
"But, mother," said Nathan, "father told me, his very self, that they were no higher than my head."
"O no," said his mother; "he said that a man madeonewhich was about as high as your head; but that was only a little one, for experiment. When they make large ones, for use, they are as high as this house."
"For use, mother? what use?" said Nathan.
"Men go up in them, don't they, aunt?" said James.
"Notinthem, exactly," said his aunt. "They could not live in them, but they go upby meansof them."
"How?" said Nathan.
"Why, they have a kind of basket, which hangs down below the balloon, and they get into that."
"I knew they could not get into the balloon," said Nathan.
"Then you have had a dispute about it," said his mother.
"Why,—yes," said Nathan, with hesitation, "we disputed a little."
"I am sorry to hear that," said his mother, "for disputing seldom does any good. The fact is, however, that men have often been carried up by balloons, but they never get into them. They could not live in them. They could not breathe the kind of air which balloons are filled with."
"It is hot air," said Nathan.
"No," said his mother, "the kind of balloon which your father told you of was filled with hot air; but the balloons which people generally use to go up with, are filled with another kind of air, which is very light when it is cool. They make an enormous bag of silk, and fill it with this light air, which they make in barrels; and then, when the bag is filled, it floats away above their heads, and pulls hard upon the fastening. There is a net all over it, and the ends of the net are drawn together below, and are fastened to the basket, or car, where the man is to sit. When it is all ready, the man gets into the car, and then they let go the fastenings, and away the great bag goes, and carries the man with it, away up into the air."
"And then how does he get down?" said Nathan.
"Why, he can open a hole in the bag, and let some of the light air out; and then he begins to come down slowly. If he comes down too fast, or if he finds that he is coming into the water, or down upon any dangerous place, there is a way by which he can make his balloon go up again."
"What way is it, aunt?" said James.
"Why, he has some bags of sand in his balloon," said his aunt; "and the balloon is made large enough to carry him and his sand-bags too. Then, if he finds that he is coming down too fast, he just pours out some of his sand, and that makes his car lighter; and so the balloon will carry him up again."
"That's a good plan," said Rollo.
"Yes," said his mother; "the reason why he takes sand is, because that will not hurt any body by falling upon them. If he should take stones, or any other heavy, solid things, and should drop them out of his car, they might possibly fall upon some body, and hurt them. So he takes sand in bags, and, when he wants to lighten his balloon, he just pours the sand out."
Rollo's mother then told the boys that there was a large book, which had several stories in it of men's going up in balloons, and that she would get it for them. So she left her work, and went out of the room; but in a few minutes she returned, bringing with her two very large, square books, with blue covers. One of them had pictures in it, and among the rest there were pictures of balloons. She opened the other book, and found the place where there was an account of balloons, and she showed the place to Rollo.
She told the boys that they had better go out in the kitchen, or into the shed, if it was warm enough, and read the account.
"You and James, Rollo," said she, "can read by turns, and let Nathan hear. Then, when the plates are referred to, you must look into the other book and find them."
"Yes," said Rollo, "we will; only, mother, if you would let us sit down here and read it—and then, if there is any thing which we cannot understand, you can tell us what it means."
"Very well," replied his mother, "you may sit down here upon the sofa."
So the boys sat down upon the sofa. They put Nathan between them, so that he might look over. Rollo and James took turns to read, and they continued reading about balloons for more than an hour. There was one story of a sheep, which a man carried up in his car, under a balloon, and then let him drop, from a great height, with a parachute over his head, to make him fall gently. And he did fall gently. He came down to the ground without being hurt at all.
How was the subject of balloons introduced into the conversation? What was Nathan's opinion about the possibility of being carried up by a balloon? What was the dispute about the size of balloons? What was Nathan's evidence? What was James's evidence? What did Jonas say when they appealed to him? What was the story that he related? Which of the boys did he finally say was wrong? Whom did the boys appeal to afterwards? What did Rollo's mother say about the size of balloons? How did she say that large balloons were filled? How can they make the balloon come down? How can they make it go up again, if they wish to do so?
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A fewdays after this, there commenced a long storm of rain. Rollo and Nathan were glad to see it on one account, for their mother told them it would melt away the snow, and bring on the spring. The first day, they amused themselves pretty well, during their play hours, in the shed and in the garret; but on the second day, they began to be tired. Nathan came two or three times to his mother, to ask her what he should do; and Rollo himself, though, being older, his resources might naturally be expected to be greater, seemed to be out of employment.
At last, their mother proposed that they should come and sit down by her, and she would tell them something more about the air. "How should you like that, Rollo?" said she.
"Why, pretty well," said Rollo; but he spoke in an indifferent and hesitating manner,which showed that he did not feel much interest in his mother's proposal.
"Ican't understand very well about the air," said Nathan.
Their mother, finding that the boys did not wish much to hear any conversation about the air, said nothing more about it just then, and Rollo and Nathan got some books, and began to read; but somehow or other, they did not find the books very interesting, and Rollo, after reading a little while, put down his book, and went to the window, saying that he wished it would stop raining. Nathan followed him, and they both looked out of the window with a weary and disconsolate air.
Their mother looked at them, and then said to herself, "They have not energy and decision enough to set themselves about something useful, and in fact I ought not to expect that they should have. I must supply the want, by my energy and decision."
Then she said aloud to Rollo and Nathan,—
"I want you, boys, to go up into the garret, and under the sky-light you will see a large box. Open this box, and you willfind it filled with feathers. Select from these feathers three or four which are the most downy and soft about the stem, and bring them down to me."
"What are they for?" said Rollo.
"I will tell you," replied his mother, "when you have brought them to me."
So Rollo and Nathan went up into the garret, and brought the feathers. They carried them to their mother. She said that they would answer very well, and she laid them gently down upon the table.
Then she took up her scissors, and began to cut off some of the lightest down, saying, at the same time,—
"Now, children, I am going to give you some writing to do, aboutthe air."
"Writing?" said Rollo.
"Yes," said his mother. "I am going to explain to you something about the air, and then you must write down what I tell you."
"But I can't write," said Nathan.
"No," said his mother, "but you can tell Rollo what you would wish to say, and he will write it for you."
"Why, mother," said Rollo, "I don't think that that will be very good play."
"No," replied his mother, "I don't give it to you for play. It will be quite hard work. I hope you will take hold of it energetically, and do it well.
"First," said she, "I am going to perform some experiments for you, before I tell you what I want you to write."
By this time, she had cut off the downy part of several feathers, and had laid them together in a little heap. Then she took a fine thread, and tied this little tuft of down to the end of it. Then she took up the thread by the other end, and handed it to Rollo.
"There, Rollo," said she. "Now, do you remember what your father told you, the other day, about the effect of heat upon air?"
"It makes it light," said Rollo.
"And why does it make it light?" asked his mother.
"Why, I don't exactly recollect," said Rollo.
"Because it swells it; it makes it expand; so that the same quantity of air spreads over a greater space; and this makes it lighter,But cool or cold air is heavier, because it is more condensed.
"Now, wherever there is heat," continued his mother, "the air is made lighter, and the cool and heavy air around presses in under it, and buoys it up. This produces currents of air. You recollect, don't you, that your father explained all this to you the other day?"
"Yes," said Rollo, "I remember it."
"Well," said his mother, "now you and Nathan may take this little tuft, and carry it about to various places, and hold it up by its thread, and it will show you the way the air is moving; and then you may come to me, and I will explain to you why it moves that way."
"Well," said Rollo, "come, Nathan, let us go. First we will hold it at the key-hole of the door."
Rollo held the end of the thread up opposite to the door, in such a way, that the tuft was exactly before the key-hole. The tuft was at once blown out into the room.
"O, see, Nathan, how it blows out. The air is coming in through the key-hole."
"Yes," said his mother; "when there is a fire in the room, and none in the entry,then the cold air in the entry runs down through the key-hole into the room."
"It don't run down, mother," said Rollo; "it blows right in straight."
"Perhaps I ought to have said it spouts in," said his mother, "just as the water did from the hole in your dam. And, now," she continued, "come and hold the tuft near the chimney."
Rollo did so; and he found that it was carried in, proving, as their father had showed them before, that the heavy, cold air, pressing into the room, crowded the warm, light air up the chimney.
"Now, should you think," said their mother, "that the cold air could come in through the key-hole, as fast as it goes up the chimney?"
Both Rollo and Nathan thought that it could not.
"Then go all around the room," said she, "and see if you can find any other place, where it comes in. For it is plain, you see, that the light air cannot be driven up chimney any faster than cold and heavy air comes in to drive it up and take its place."
So Rollo and Nathan went around the room, holding their tuft at all the places theycould find, where they supposed there could be openings for the cold air to press in. They found currents coming in around the windows, and by the hinges of the doors; and at length Rollo said, he meant to open the window a little way, and see if the cold air from out of doors would not press in there too. He did so, and the tuft was blown in very far, showing that the cold air from out of doors pressed in very strongly.
"Now, if all these openings were to be stopped," said their mother, "then no cold air could crowd into the room; and of course the hot air could not be buoyed up into the chimney, and a great deal of the hot air and smoke would come into the room. This very often happens when houses are first built, and the rooms are very tight.
"But now, Rollo," she continued, "suppose that the door was opened wide; then should not you think thatmorecold and heavy air would press in, than could go up the chimney?"
"Yes, mother, a great deal more," said Rollo.
"Try it," said his mother.
So Rollo opened the door, and held histuft in the passage-way; and he found that the air was pressing in very strongly through the open space. Wherever he held it, it was blown into the room a great deal, showing that the heavy air pressed in, in a torrent.
"Now, as much warm air must go out," said she, "as there is cold air coming in; but I don't believe that you and Rollo can find out where it goes out."
Rollo looked all around the room, but he could not see any opening, except the chimney and the door, and the little crevices, which he had observed about the finishing of the room. He said he could not find any place.
His mother then told him to hold his tuft down near the bottom of the door-way. He did so, and found that the current of air was there very strong. The tuft swung into the room very far.
"Now hold it up a little higher," said his mother.
Rollo obeyed, and he found that it was still pressed in, but not so hard.
"Higher," said his mother.
Rollo raised it as high as he could reach. The thread was of such a length, that thetuft hung about opposite to his shoulder. The tuft was still pressed in, but not nearly as far as before.
"So you see," said his mother, "that the air pours in the fastest at the lowest point, where the weight and pressure of the air above it are the greatest; just as, in your dam, the water from the lowest holes spouted out the farthest."
"Yes," said Rollo, "it is very much like that."
"Now," continued his mother, "you see that a great deal of air comes in, and if you look up chimney, you will see that there is scarcely room for so much to go up there;—and yet just as much must go out as comes in.
"Get the step-ladder," said his mother, "and stand up upon it, and so hold your tuft in the upper part of the door-way."
There was in the china closet a small piece of furniture, very convenient about a house, called a step-ladder. It consisted of two wooden steps, and was made and kept there to stand upon, in order to reach the high shelves. Rollo brought out the step-ladder, and placed it in the door-way, andthen ascended it. From the top he could reach nearly to the top of the door; but then, as his tuft was at the end of the thread, it hung down, of course, some little distance below his head.
"Why, mother," said Rollo, "it goesout."
"Yes," repeated Nathan, "it goes out."
In fact, Rollo found that the tuft, instead of swinging into the room, was carried out towards the entry.
"You have found out, then," said his mother, "where the hot air of the room goes to, to make room for the cold air, that comes in from the entry."
"Yes, out into the entry," said Rollo.
"Through the upper part of the door," said his mother. "Suppose the entry were full of water, and the parlor full of air, and the door was shut, and the door and the walls were water-tight. Now, if you were to open the door, you see that the water, being heavier, would flow in, through the lower part of the door-way, into the parlor, and the air from the parlor would flow out, through the upper part of the door-way, into the entry. The water would settle down in the entry, until it was level in both rooms, and then the lowerparts of both rooms would be filled with water, and the upper parts with air."
"Yes, mother," said Rollo.
"And it is just so with warm and cold air. If the parlor is filled with warm air, made so by the fire, and the entry with cold air, and you open the door, then the cold air, being heavier, will sink down, and spread over the floor of both rooms; and the warm air, being light, will spread around over the upper parts of both rooms; and this will make a current of air, in at the bottom of the door-way, and out at the top.
"Now," continued his mother, "let me recapitulate what I have taught you."
"What do you mean byrecapitulatingit?" said Nathan.
"Why, tell you the substance of it, so that you can write it down easier."
"O, I can write it now," said Rollo; "I remember it all."
"Can you remember it, Nathan?" said his mother.
"Perhaps I can remember some of it," said Nathan.
So Rollo and Nathan went out into another room, where Rollo kept his desk,and they remained there half an hour. When they returned, they brought their mother two papers.
Their mother opened the largest paper, and read as follows:—