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?

CHAPTER VII.

PHILOSOPHICAL DISCUSSION

Some time 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 insist upon it that he should know that they are smaller?"

"Because I

know

," 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, "why

you

believed 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 is wrong, 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 to

conquer

"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 pleasure of 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 made

one

which 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.

"Not

them, exactly," said his aunt. "They could not live in them, but they go up

by means

of 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.

QUESTIONS

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?

CHAPTER VIII.

TASKS

A few days 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.

can'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 will find 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, about

the 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 they could 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 that

cold 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 his tuft 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 the tuft 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 hous