"Does it?" said Rollo, turning around, and looking up to the part of the heavens where he had seen the star the evening before.

"Yes," said Jonas; "and the reason why we cannot see it now, is the bright daylight. It is up there now, just where it was last night."

"And the Dipper, too?" said Rollo.

"Yes, and the Dipper, too; only that has moved half round, I suppose, and is now away up above the North Star."

"I wish I could see it," said Rollo. And he looked as steadily and intently into the clear blue sky, as he could; but he could not possibly see the least sign of a star.

* * * * *

However, the sun shone bright, and it cast a strong shadow from the stakes which they had driven into the ground. Jonas soon went away to his work, and left Rollo to mark the hours by means of the clock.

So Rollo had to go into the house very often to see what time it was; and at last his father, who was sitting there at his writing, asked him what made him want to see the clock so much. Rollo told him the reason. So his father put down his pen, and came out to see the dial.

When he saw the two stakes, with their lower ends driven into the ground, and the upper ends nailed firmly together, he looked at them with a smile, but did not say any thing.

"Will that do?" said Rollo, looking up very eagerly into his father's face.

His father did not answer, but continued to examine the work on all sides, with a countenance expressive of curiosity and pleasure.

"It points to the North Star, exactly," added Rollo. "Jonas sighted it."

"Yes," said his father; "I think that will do; you have got quite a respectable gnomon."

"Gnomon?" said Rollo.

"Yes," said his father; "we call such a thing a gnomon. In common dials, they are made of brass; but I don't see why this won't do very well. It is rather a large gnomon."

"Is it?" said Rollo.

"Yes," said his father, "I think it is the biggest gnomon I ever saw.

"But how are you going to mark the hour lines, Rollo?" asked his father.

"Why, we are going to drive little stakes down into the ground."

"'Seems to me that you can contrive some better plan than that," said his father.

"Why?" said Rollo. "Is not that a good plan?"

"Not very good," he replied; "because you cannot be exact in driving down stakes. The beauty of a dial is its exactness. I should think that you would do better to put a board down upon the ground, and mark your lines upon that."

"O, the board would get knocked about," said Rollo.

"I dare say that Jonas would contrive some way to keep it steady."

"But he says he can't do any thing more about the dial to-day, for he must attend to his work."

"Let me see—he is putting the harnesses in order, I believe."

"Yes, sir," said Rollo.

"Well, you may tell him that after he has done the harness that he is at work upon now, he may finish his dial."

Then Rollo's father went into the house, and away went Rollo in pursuit of Jonas.

Jonas liked the plan of putting a board down very much, and in a short time he went to work to do it. He planed out a board of the right length, and then put it down upon the ground, under and between the two stakes, but nearest to the upright one. They placed it across at right angles to the line between the stakes, and of course, as the stakes were in a north and south line, the board was in an east and west line, and so the shadows were cast exactly across it.

The board being planed smooth, the edge of the shadow could be seen much more distinctly upon it, than upon the ground; so Jonas was satisfied that it would be a great deal better to draw the hour lines upon the board. After having determined upon the place where it was to go, he took it up again, and then drove down two strong but short stakes, sawed off square at the top, into the ground, one on each side; so that they should come under the two ends of the board. Then he laid the board down again upon the stakes, and nailed the ends of the board to them. The stakes had been driven in until they were just level with the surface of the ground, and so the board seemed to be lying along upon the ground too, though it was, in fact, fastened securely to the short stakes. Then the boys marked the hour lines upon the board with some black paint; and thus they had a very respectable dial. When the sun shone, Rollo could tell what o'clock it was near enough for all his purposes.



THE BEE-HIVE.

One of the drollest of all of Rollo's experiments was his plan for getting a bee-hive.

One day, he was in the garden with a playmate of his, named Henry, who lived not very far from his father's house.

In the back part of the garden were some tall hollyhocks growing. They were in full flower. Hollyhocks are very tall. They grow up in a straight stem, as high as a man's head, with leaves and flowers from top to bottom.

The flowers are large, and shaped somewhat like a cup, or rather a wine-glass, and bees often go into them to get honey.

Now it happened that as Rollo and Henry were sauntering about, near these hollyhocks, Rollo happened to see a bee in one of the flowers, loading himself up with wax or honey. The flower, that the bee was in, was just about as high as Rollo's head.

"O, there's a bee!" said Rollo; "let's catch him."

"Catch him!" said Henry. "If you do, you'll catch a sting, I rather think."

"No," said Rollo, "I can catch him without getting stung."

"How?" said Henry.

"I will show you," said Rollo.

So saying, Rollo approached the hollyhocks, and put both his hands up slowly to the flower which the bee was in. He then very carefully gathered together the edges of the flower, so as to enclose and imprison the bee. He then gently broke off the stem of the flower, and held it up to Henry's ear, to let him hear the bee buzz within.

"Now," said Rollo, "I wish I had a little bee-hive. I would put him in, and perhaps he would make some honey in there."

"Do you think he would?" said Henry.

"Yes," replied Rollo, "I have no doubt he would; bees always make honey in bee-hives."

"Haven't you got some box that will do?" said Henry.

"I don't know," said Rollo; "let us go along towards the barn, and see if we can't find one. I suppose it is no matter what the shape of it is," he added, "if it is only a box, with a small hole for the bees to go in and out."

"But you haven't got but one bee," said Henry, as they walked along towards the barn.

Rollo held the flower, with the bee imprisoned in it, safely in his fingers.

"O, I can catch plenty more. I could catch a whole hive of them, in time."

"But I don't believe they will stay and work in your hive," said Henry. "They will all fly off and go home to where they belong."

"No," said Rollo, "I will plug up the hole, and keep them shut in until they get used to it. When they get wonted to the new hive, they will stay there, after that, I know. That's the way they do with doves."

"But you won't have any queen bee," said Henry. "Bees won't work without a queen bee. I read it in a book."

"Well, perhaps I can catch a queen bee, some day," said Rollo, rather doubtfully.

Rollo was so much interested in his plan, that he was determined not to see any difficulties in the way of it; and yet he could not help feeling that there was some uncertainty about his succeeding in entrapping a queen bee.

However, just at this point in the conversation, he suddenly stopped, and pointed down to a flower-pot, which stood bottom upwards, upon a seat, near where they were walking.

"There," said he, "that will do for a bee-hive."

"Ho!" said Henry, "that is not a box."

"No matter," said Rollo; "it is just as good, and there is a little hole for the bees to go out and in at."

There is always a little hole in the bottom of a flower-pot.

"So there is," said Henry; "but do you think that the bees will make honey in an earthen pot?"

"O, yes," said Rollo, "just as well as in any thing. The bees don't care what they make the honey in. Sometimes they make it in old logs."

"Well," said Henry, "and we'll call it a honey-pot. And where shall we put it?"

"We can keep it on this seat: it is as good a place as any; the bees will be right in the garden as soon as they come out of their hive."

So saying, Rollo asked Henry to hold his bee a minute, while he got the honey-pot ready. Henry took the flower very carefully, so as not to let the bee escape, and then Rollo lifted up the flower-pot, and looked inside. It was pretty clean; but as Rollo knew that bees were very nice in their habits, he thought he would just take it to the pump, and wash it out a little.

In a few minutes, he brought it back, and replaced it, bottom upwards, upon the seat, and then prepared to put the bee in. He took the flower again from Henry's hand, and then very carefully inserted the edges of it, which had been gathered together with his fingers, into the hole. He then began to knock and push the bottom of the flower, to make the bee go in. The bee, not knowing what to make of this treatment, kept up a great buzzing, but soon went in.

"There," said Rollo. "Now, Henry, you be ready to clap your thumb over the hole, as soon as I take the flower away, or else he'll come out."

"O, no," said Henry; "he'll fly up and sting me."

"No, he won't," said Rollo. "I only want you to keep him in a minute, while I go and get a plug."

Henry then, with much hesitation and fear, put his thumb over the hole, as Rollo withdrew the flower. He stood there while Rollo went for a plug; but he seemed to feel very uneasy, and continually called Rollo to be quick.

Rollo could not find a plug, but he picked up a small, flat stone, and concluded that that would do just as well. So he released Henry from his dangerous position, and put the stone over the hole.

"There," said Rollo, with a tone of great satisfaction, when he had done this, "now he is safe. We'll let him stay, while we go and catch another bee."

So they went back to the hollyhocks, and there, quite fortunately, they found another bee just going into one of the flowers. Rollo secured him in the same way, and carried him along, and pushed him into the flower-pot. Henry stood ready to clap the stone on, as soon as he was in, and then they came back to the hollyhocks again. They had then to wait a little while, watching for bees; at length, however, one came, and, by and by, another; and so, in the course of an hour or two, they got seven bees, all safe in the honey-pot, and Rollo said he thought seven were about enough to go to work, at least, to begin. They had not yet found any one, however, that seemed to Rollo to be a queen bee.

At last, it was time for Henry to go home, and Rollo concluded to leave his bee-hive until the next morning. He thought he would leave the hole stopped up, so that the bees might get used to their new accommodations; but he intended to open it the next day, in order to let them begin their work.

The next morning, Henry came over soon after breakfast to see how affairs stood in respect to the bee-hive. He and Rollo went out into the garden to look at the establishment, and found every thing as they had left it the night before. Rollo felt quite confident of the success of his experiment. The only thing that gave him any uneasiness was the want of a queen bee. He and Henry were just speculating upon the expediency of sending in a bumble-bee instead, for a king, when their attention was arrested by hearing Jonas calling Rollo. They looked up, and saw him standing at the garden gate.

"Rollo," said Jonas, "do you want to go out with me to the pasture, and catch the horse?"

"Why,—yes," said Rollo. But yet he did not go. He seemed to feel in doubt. "Must you go this minute?" said he.

"Yes," said Jonas. "Come; and Henry may go, too."

"Well, wait a minute, just till I go and open the door in my bee-hive."

"Your bee-hive!" said Jonas; "what do you mean by that?"

But Rollo did not hear what Jonas said; for he had run off along the alley, Henry after him, towards the place where they had established their hive.

"What does he mean by his bee-hive?" said Jonas to himself. "I mean to go and see."

So Jonas opened the garden gate, and came in. When he came up near the seat where Henry and Rollo stood, he found the boys standing a step or two back from the flower-pot, both watching the hole with the utmost intentness.

"What are you looking at, there, boys?" said Jonas, with great surprise.

"O, we are looking to see the bees come out."

"The bees come out!" said Jonas.

"Yes," said Rollo; "that is our bee-hive,—honey-pot we call it. We have put some bees in it."

Here Jonas burst into a loud, and long, and apparently incontrollable fit of laughter. Henry and Rollo looked upon him with an expression of ludicrous gravity and perplexity.

"What are you laughing at?" said Rollo.

Jonas could hardly control himself sufficiently to speak; but presently he succeeded in asking Rollo if he supposed that bees would make honey there.

"Certainly I do," said Rollo, with a positive air. "Why should they not? They don't care what shape their hive is, or what it is made of, and this flower-pot is as good as any thing else. There! there! see, Henry," he exclaimed, interrupting himself, and pointing down to the flower-pot, "one is coming out."

Henry and Jonas both looked, and they saw a poor, forlorn-looking bee cautiously putting forth his head at the hole, and then slowly crawling out. He came on until he was fairly out of the hole, and then, extending his wings, rose and flew away through the air.

Here Jonas burst out again in a fit of laughter.

"You needn't laugh, Jonas," said Rollo; "he'll come back again; I know he will. That's the way they always do."

"And you suppose that the bees will fill up the flower-pot with honey?" said Jonas.

"Yes," said Rollo; "and then I shall take it away without killing any of the bees. I read how to do it in a book."

"How shall you do it?" said Jonas.

"Why, when this honey-pot is full of honey, I shall get another, and put on the top of it, bottom upwards. Then the bees will work up into that, and come out at the upper hole. When they get fairly at work in the upper hive, then I shall get Henry to hold it, while I slip the lower one out, and put the upper one down in its place."



As Rollo was speaking these words, in order to show Jonas more exactly how he meant to perform the operation, he took hold of the flower-pot with both his hands, and slid it suddenly off of the seat. Now it happened that the poor bees that were inside, chilled with the dampness and cold, were nearly all crawling about upon the seat; and when Rollo suddenly moved the flower-pot along, forgetting for a moment what there was inside, the rough edges of the flower-pot bruised and ground them to death, and they dropped down upon the walk, some dead, some buzzing a little, and one trying to crawl.

"There now, Rollo," said Henry, in a tone of great disappointment and sorrow, "now you have killed all our bees!"

Rollo looked astonished enough. He had no idea of such a catastrophe; and he and Henry both at the same instant took up the honey-pot to see if any of the bees had escaped destruction. Their eyes fell, at the same moment, upon one solitary bee that was standing upon the inside of the flower-pot. His attention had been arrested by the sudden glare of light, and so, just as Rollo and Henry first observed him, and before they had time to put the flower-pot down again, he spread his wings and flew out towards them.

Down dropped the flower-pot. The boys started. "Run!" exclaimed Jonas, following them with shouts of laughter, "run, run, boys, for dear life!" and away they all went towards the garden gate.

The bee, however, was not following them. His only object was to get away. He flew in another direction; but Rollo, Henry, and Jonas did not stop to look behind them. They kept on running, until Jonas was well on his way towards the pasture, and Rollo and Henry were safe in the shed. And this was the last time that Rollo ever attempted to make up a hive of bees.



JONAS'S MAGNET.

One evening, after tea, Rollo was seated upon his cricket, before the fire, reading. His mother was upon the sofa, also reading, and so the room was very still.

By and by, Rollo finished his book. It was quite a small story-book, and he had been reading it some time, and so he had got to the end. He laid the book down, therefore, upon the table, and began to consider what he should do next.

"Mother," said Rollo, "what shall I do?"

"I don't know," said his mother; "you must contrive some way to amuse yourself, for I am busy reading, now."

Rollo sat still, looking at the fire a few minutes, and then he thought he would go out into the kitchen, and see what Nathan was about. Accordingly, he went into the kitchen. Dorothy was at work, making some bread for the next day. Jonas was bringing in wood. Nathan was sitting upon the floor before the fire, very much interested in looking at something which he held in his hand.

"What have you got, Nathan?" said Rollo.

"I am seeing this nail stick on," said Nathan.

"Stick on!" said Rollo; "what does the child mean?" He accordingly came up to Nathan, and found that he had a smooth, flat bar of steel, not very regular in its shape, in one hand, and a nail in the other; and he was amusing himself with applying the nail to the bar of steel, and seeing it adhere.

"It is a magnet," said Rollo. "What a big magnet! Where did you get it, Nathan?"

"Jonas gave it to me," said Nathan.

"Let me try it," said Rollo. And he stooped down by the side of Nathan, and offered to take away the magnet.

But Nathan held it off upon one side, and said, "No, no; I must have it. Jonas gave it to me."

"Well, Thanny," said Rollo, "I won't take it away; only you let me sit here and see you play with it."

So Rollo sat still, and did not molest Nathan, but only looked on and saw him touch the little nail to the bar, and leave it hanging there. Rollo knew it was a magnet, for he had heard of magnets, though he had never before had an opportunity of seeing one. As Nathan found that Rollo was not going to take the magnet away from him, he soon ceased to appear afraid of him, and presently he let Rollo have the magnet in his hands. Rollo said he only wanted to look at it a moment, to see what made the nail stick on.

He examined the steel bar carefully. It was not quite a foot long, and was shaped like a common flat ruler; only, instead of being straight from end to end, it was swelled out a little along in the middle. On looking at the bar very attentively, Rollo observed some very fine, hair-like lines, crossing each other, so as to produce the appearance of fine net-work. Rollo supposed that this was what caused the magnet to take up the nail. He observed that there was one place, near the middle of the bar, where this net-work was more distinct and strong than in the other parts of the bar, and so he put the nail there, expecting that it would be attracted very strongly. But he was surprised at observing that it was not attracted there at all. He then tried it at different places, all along the bar, and he found that it was not attracted any where in the middle, but only at the two ends.

While he was wondering what could be the cause of this, he heard the front door open, and he knew that his father had come home. So he jumped up and ran off into the entry, Nathan following him, to show his father the magnet. His father was busy putting away his coat and hat, and told the boys to go into the parlor, and he would come in, in a moment, and see it. When he came in, he sat down before the fire, and took the magnet, Rollo and Nathan standing by his side, and looking on with eager curiosity.

Rollo's father examined the magnet from end to end, very carefully, for some time, without speaking. At length, he said,

"It is an old file."

"An old file!" said Rollo.

"Yes," said his father. "Some of Jonas's work, I suppose."

"Yes, sir," replied Rollo; "at least it is Jonas's magnet."

"There you see the marks," continued his father, pointing to the net-work, "of the old file teeth. Jonas ground them nearly out."

"Are those the marks of the file teeth?" said Rollo. "I thought it was the magnetism."

"No," said his father, smiling, "those are the traces of the file teeth, undoubtedly. You may go and ask Jonas how he got his magnet."

So away went Rollo and Nathan in pursuit of Jonas. They found him in the kitchen, just arranging his wood for the morning fires. They asked him where he got his magnet, and Jonas replied as follows:—

"Why, the other day, I went into town with your father's watch, to get a new crystal put in; and when I was at the watchmaker's, I saw a curious-shaped piece of iron hanging up. I asked the man what it was. He said it was a magnet, that he kept to touch needles. Then he gave me a nail, and let me see how the magnet would attract it. He told me, too, that if I had a knife, and would rub my knife on the magnet, the knife would attract, too; and so I did rub it, and I found that my knife would attract the nail, though not very strong. Then I asked him if any piece of iron would attract, after it was rubbed upon the magnet; and he said that iron would not, but that any piece of steel would. He told me that if I would bring a larger piece of steel, when I came after the watch, he would rub it for me, and then I should have a larger magnet. I told him I had not any steel. But he said any old file would do, and that I might grind the sides and edges a little, and make it smooth.

"So, when I came home, I found some old files in the barn. Some were three-cornered, and some were flat. I thought the flat would be the best shape, and I asked your father if he would give me one of them. He said he would; and so I ground the ends square, and the sides smooth, upon the grindstone. Then, when I went after the watch, the man rubbed it for me, and it makes a very good magnet."

Then Rollo and Nathan went back, and repeated this story to their father.

"Very well," said their father; "that was a very good way to get a magnet. I remember giving Jonas the file; but I did not know what he wanted it for."

"I think a magnet is a very curious thing," said Rollo. "See how the nail sticks to it!"

"There are a great many other things curious about it," said his father, "besides that."

"What?" said Rollo.

"I should want some other apparatus to show you," replied his father.

"And can't you get the other apparatus?"

"I don't know. Perhaps mother might get it. Yes, I'll tell you what we will do. I will name some things which mother may prepare, and you may get them together upon the table in the kitchen, when they have got the kitchen all in order. Then I will come out, and give you all, out there, a lecture upon magnetism."

Rollo and Nathan were exceedingly pleased with this plan; and even Rollo's mother looked somewhat gratified. She said she did not know much about magnetism, and she meant to go out into the kitchen herself, and hear the lecture.

"And what things shall we get?" said Rollo.

"Two or three needles," replied his father, "some fine, and some coarse; some thread, a saucer nearly full of water, a cork, the sand-box off of my table, and a sheet of white paper. Put them all in good order upon the table, and set the chairs around it. Then, when all is ready, come and tell me."

So Rollo's mother put down her book and went to help Rollo collect the articles which his father had said he should require. She began to look into her needle book for the needles and thread, while Rollo went for the sand-box. When Rollo came back with the sand-box and the sheet of paper in his hand, he found Nathan with his high chair, at the kitchen door, trying to get in.

"What are you doing here, Nathan?" said Rollo.

"I want to get my high chair in," he replied.

The truth was, that Nathan, having learned from the conversation what was going on, was eager to secure a good seat for himself, and so he was attempting to drag out the high chair which was kept in the parlor for him to sit up to the table in.

Rollo, as he happened to feel rather good-natured than otherwise, just then, after putting down his things, helped Nathan get his chair through the door, and placed it up at the kitchen table, which stood out in the middle of the floor. He then went into a closet, and opened a little drawer, where he knew corks were kept, and brought out one or two, selecting the cleanest and softest that he could find. When he came back, he found Nathan, pouring out some black sand, from the sand-box, upon the sheet of paper.

"Now, Nathan," exclaimed Rollo, running up to him, and seizing the sand-box, "you are a very naughty boy." And he attempted to take away the sand-box violently.

But Nathan, though he knew very well that he was doing wrong, did not seem fully disposed to admit Rollo's authority to set him right by violence. He resisted; and, in the struggle, the table was pushed away, and the water in the saucer spilled over. The water ran along under the sheet of paper. Nathan, seeing the mischief that had been done, was a little frightened, and released his hold. Rollo then took up the paper, which had sand upon the upper side, and water dripping off from the under side, saying,

"There, Nathan, now see what you have done!"

"I didn't do it," said Nathan.

"You did," said Rollo.

"I didn't," said Nathan.

Hereupon, Jonas came up to the table to see what was the matter. Each of the boys told his story.

"Now we are in pretty trouble," said Jonas; "we thought we were going to have a fine lecture; instead of that, there are two boys to be punished, and wet paper to be dried."

"Punished?" said Rollo.

"Yes," said Jonas, "Nathan for touching the sand-box, and you for touching him."

"Why, he was pouring out all the sand," said Rollo, "and I was only trying to stop him."

"Yes, but you know," said Jonas, "that you had no right to stop him by violence. That always makes the difficulty worse."

Here Rollo began to look pretty sober. He knew that he had done what he had very often been forbidden to do.

"Now," said Jonas, "we can wait and tell your mother about it, when she comes out, or we can just settle it all among ourselves."

"How?" said Rollo, with an anxious look.

"Why, I can dry the paper and the sand," said Jonas, "if you and Nathan will only punish the boys."

"How shall we do it?" asked Rollo, looking up with a faint and doubtful smile.

"I think a pretty good punishment," said Jonas, "would be for you and Nathan to go and sit in two corners of the room, with your faces to the wall, until I get the paper and sand dry—if you think that would be punishment enough."

"Well," said Rollo,—his eye brightening at the idea of winding up so unpleasant a business so easily,—"well, Nathan, let's go."

Nathan was ready, and so he climbed down from his high chair, and as Rollo went to one corner of the room, he went to the other, and they took their places, as Jonas had directed; only Nathan could not resist the temptation of looking round, now and then, to see how Jonas got on with the drying of the paper. They, however, bore their self-inflicted punishment very patiently; and when Jonas had got the paper dried, and the table wiped down, and every thing replaced as it was before, he told them that it was time for them to get up again. The punishment was not very severe, it is true; but then, it was probably a pretty efficacious one, in respect to its effect in impressing it upon Nathan's mind that he must not touch things without leave, and upon Rollo's, that, when Nathan is doing wrong, he must not set him right by violence.

In a short time after this, the things were all ready upon the table, the chairs were placed around it, and Rollo went to call his father. He found him writing a letter. As soon as he reached the end of a sentence, he came out, and took his place at the table. Rollo's mother sat next to him at the same side of the table, and Jonas and Dorothy in two chairs, on the opposite side. Rollo then was placed at one end of the table, and Nathan, in his high chair, at the other.

Just then, however, Rollo's mother observed that the table was wet a little.

"Why, Rollo," said she, "how came the table wet?"

"Why, Nathan and I did it," said he.

"How?" said his mother.

"Why, we did it—eh—pulling. But Jonas has settled it all, mother."

"Ah! Jonas has settled it, has he? very well. Then we will all now attend to the lecture."



MAGNETISM.

Rollo's father looked over the things which had been arranged upon the table, for a moment, in silence, and then took up Jonas's magnet.

"This bar is what they call a magnet," said he; "but all the magnetism is in the two ends."

"It is?" said Rollo; "and what is the reason of that?"

"You can see that it is so," said his father, without answering Rollo's question, "in this way."

So he laid a small nail down upon the table, and then touched the middle of the magnet to the nail. It was not attracted at all. Then he moved it along a little, towards one end, and touched it again. Still it was not attracted. Then he moved it along farther and farther; but the nail was not attracted until he got to the end of the bar, and then the nail hopped up and adhered to it quite strongly.

"How curious!" said Rollo.

His father then repeated the same experiment with the other half of the bar, and found the result the same. The nail did not appear to be at all attracted until he reached the end, and then it was lifted and held by this end, just as it was by the other.

"So that, you see," said Rollo's father, "that the attractive power of the magnet resides in the ends."

"Well, father, what is the reason?"

"I don't know," said his father.

"Don't you know, father?" said Rollo. "I thought you were going to tell us all about it."

"No," said his father. "I only know a very little about it, myself. I am going to explain to you some of the facts,—such as I happen to know. So you must all remember this fact, that in the magnet, the attractive power is not distributed over the whole mass, but resides only in the opposite ends. These ends are called poles."

"Yes, sir," said Rollo, "we will remember."

"Now I can make this apparent in another way," said his father. Then he asked Rollo's mother to thread a needle; and when it was threaded, he asked Jonas to stand up and hold the thread in such a manner as to let the needle hang over the middle of the table.

Then, when the needle was still, he brought up the middle of the magnet very near to the needle; but it did not move towards it at all. Then he drew the magnet along towards himself, keeping it at the same distance from the needle, and when the end of the bar came opposite to the needle, it immediately leaped out of its place, and adhered strongly to it.

"There is another way still," continued the lecturer, "better than either of these."

So saying, he took off the needle, which had adhered to the magnet, and drawing out the thread, he laid the needle itself carefully away upon a distant corner of the table. Rollo took it up, and was going to place it back with the others. But his father told him to put it down again, by itself, where he had placed it, and not to touch any of the things without his direction.

"I am going to show you another way," he added, "of making it evident that the attractive power of the magnet resides at or near the poles."

So saying, he opened the sheet of paper, and spread it out upon the table. Then he laid the magnet down upon it.

"Now, Jonas," said he, "sprinkle some sand upon it from my sand-box, carefully, and see where the sand will adhere."

So Jonas took the sand-box, and held it over the bar, not very high, and moved it slowly along, from one end to the other, and thus sanded the magnet all over. The sand fell off of it, however, freely, at every part except the ends; and Jonas, observing that it seemed to adhere there, held the sand-box a little longer over those places; and thus there was formed a sort of a black bur at the extremities, consisting of an accumulation of the black particles of sand. Rollo's father then took up the bar carefully, and passed it around, so that all who were seated at the table could examine it closely.

"It is thickest on all the edges and corners," said Rollo.

"Yes," said his mother; "and the sand forms little black bristles, pointing off in every direction."

They all examined it attentively, and observed the little black bristles pointing out every way from the edges and corners at the ends.

"This shows you," said Rollo's father, "exactly how the magnetic power, so far as its attractive force on other bodies is concerned, is distributed. You see it resides in the two ends, and the two ends seem to be exactly alike."

"Yes, sir," said Rollo, "exactly."

"They seem to be so," continued his father; "but the fact is, the magnetism of one end is very different from that of the other."

"I see that the cluster of sand is a little bigger at one end, than it is at the other," said Rollo's mother. She was more observing than the others, and had noticed a little difference, which had escaped the rest.

"That indicates only a difference in degree," said Rollo's father; "but there is a difference in kind."

"What do you mean by that, father?" asked Rollo.

"Why, if the attractive powers at the two ends were both alike in their nature, only one was stronger than the other, then the difference would be in degree; but there is a difference in the nature of the magnetism itself. In fact, the magnetisms of the two ends are of opposite natures in some respects."

"Why, both ends attract the sand," said Rollo, "just alike."

"True," said his father; "they seem to attract the sand in precisely the same way; and, looking at the bar, as I now hold it up," he added, "with the sand adhering in the same way at the two ends, one would suppose that they were both magnetic alike. But, in fact, there is a great difference between them."

All the company looked upon the two ends of the bar, as Rollo's father held it up, wondering how he would show that there was any difference between them.

"Now, in the first place," he continued, "we must get the sand off of the ends. Do you think you can get it off for me, Rollo?" said he.

Rollo took the bar very eagerly, and attempted to brush the sand back upon the paper. He succeeded in brushing off a little of it; but the greater portion remained. When he rubbed upon one side, it moved round to the other; and he could not get it off.

"Hand it to me," said his father, "and I will show you how it can be done."

He also asked Jonas to hand him the tongs, which were standing by the side of the fire. He then held the tongs over the sheet of paper, in a horizontal position, and gently rapped the end of the magnet against them, letting the end project a little over the tongs. This knocked all the sand off, and left the bar clean as it was before.

"Now let me see," said he, "what was it that I was going to tell you next?"

"You were going to show us," said Rollo's mother, "that there are two different kinds of magnetisms in the two ends of the bar."

"O, yes," said he. "In order to do this, I must poise a needle in a new way."

He then took up one of the corks which Rollo had put upon the table. From one end of this cork, he cut off, with his penknife, a round, flat piece. It was about as large around as a wafer, but somewhat thicker. He cut a little groove along the upper side of this, and laid the same needle which he had before used, and which he had put away upon the corner of the table, into this groove. Then he put the whole carefully into the saucer of water, which he had previously drawn up towards him.

"There," said he, "we call a cork like that, a float; because it is intended to float a needle upon. Now, you see, the needle being supported by the cork, and the cork floating freely in the water, the needle is at liberty to move in any way."

Nathan thought it was a very curious experiment to poise a needle so, upon a piece of cork,—even without the magnetism. And he watched it as it slowly moved about, with a face full of interest and curiosity.

The needle swung round a little one way and the other, and finally came to a state of rest. Then Rollo's father held the magnet in his hands, in such a manner as to point it towards the needle, and then gradually brought it down near the water, just by the side of the point of the needle. The point immediately began to move slowly towards the bar; but Rollo's father lifted it up suddenly, before the needle had time to touch it. Then he brought the same end of the magnet down upon the other side of the point of the needle, and that drew it back again.

"There," said he, "you all see that the point of the needle is attracted by the bar, whichever side I put it."

They all said they saw it very plainly.

"Now," said he, "I am going to turn the magnet, and bring the other end of it down to the point of the needle; and if the magnetism at this end is the same with that in the other, the point of the needle will of course be attracted by this end too."

"Certainly," said Rollo's mother.

Then he brought down the other end of the bar towards the needle. This other end was a little bigger than the one which he had tried first, because the file had been a little bigger at that end. But the needle, instead of being drawn towards it, as it had been towards the other end, began to move slowly away from it.

"Why, it is going away," said Rollo.

His father did not answer, but immediately raised the bar and put it down upon the other side of the point, and then the point began to move away back again; being evidently driven away from the large end of the magnet, on whichever side it was presented.

Then Rollo's father reversed the magnet again; that is, he brought the smaller end towards the needle as at first. The point of the needle was now attracted, that is, drawn towards the magnet; and then when he changed it again, and brought the large end to the needle, it was always repelled; that is, driven away again.

"Now you see," he said, "that the small end of the magnet attracts the point of the needle, and the large end drives it away. That shows that the magnetism in the two ends is of two different kinds.

"And now," he continued, "there is one thing more which is remarkable about it; and I want you to observe it very carefully. You see," he says, "that the small end of the magnet attracts the point of the needle. But if I try it now upon the other end of the needle, where the eye is, it will repel that, just as the large end of the magnet repels the point."

He tried it, and the result was just as he had said. And he repeated the experiment in a great many ways, and they always found that the large end of the magnet would draw the eye of the needle towards it, and drive the point away; and the small end of the magnet would draw the point of the needle, and drive the eye away. This proved, as Rollo's father said, some great difference between the magnetisms of the two ends. "And you see," he added, "that it is a difference in kind, not merely a difference in degree."

"But one thing seems strange to me," said Rollo's mother, "and that is, that both ends of the magnet don't attract the point of the needle, just as both of them attracted the nail."

"And the sand," said Rollo.

"Yes," added his mother. "When you brought both ends of the magnet, one after the other, to the nail, they both attracted it."

"And so they did the needle which hung down by the thread," said Jonas.

"Yes," said Rollo's mother; "but now this needle, that is floating upon the water, is half attracted, and half repelled."

"The reason is," said Rollo's father, "that the needle, that is floating upon the water, is a magnet itself, and has two magnetic poles; but the sand, and the nail and the needle that Jonas held up by the thread, were not magnets. They were only common pieces of iron and steel."

"Why, father," said Rollo, "that was the very same needle; you laid it away upon the corner of the table."

"Yes," said his father; "but it was not a magnet then."

"When?" asked Rollo.

"Why, when Jonas held it up by the thread."

"And is it a magnet now?"

"Yes," said his father. "We will see if it is not."

So he took the needle off from the float, and put it upon the paper. He then sprinkled a little sand over it, from the sand-box, and, upon taking it up, they all saw that there was a little tuft of black sand both upon the point and at the eye, showing that it was magnetic at both ends.

"It became magnetic," said Rollo's father, "only by being touched by the bar magnet; and that was the reason why I put it away by itself as soon as it had touched the bar. I did not want to have it mixed with the other needles, which had not been touched, and which, of course, were not magnetic. Now, if I take one of the needles which has not been touched, and put it upon the float, you will see that both ends of it will be attracted by both ends of the bar."

So he placed away the magnetized needle upon the corner of the table again, and took another one, and placed it very carefully upon the float. Then he brought down one end of Jonas's magnet very near the point of the needle. It attracted it. Then he brought it down very near the eye of the needle. It attracted the eye too. Then he turned the magnet, and tried the other end, and he found that that end also would attract both the eye and the point of the needle.

"Try the magnetized needle, and see if that will attract it too," said Rollo's mother.

Then Rollo's father took the magnetized needle from the corner again, and brought the two ends of that, one after another, near to the ends of the needle upon the float. It attracted them just as Jonas's magnet had done, only a great deal more feebly.

"So, you see that this needle is really a little magnet, just like Jonas's great one."

"Only there is no proof that it has the two different kinds of magnetism in the two ends," said Rollo's mother.

"We can easily show that," said his father. He asked Dorothy to get another saucer full of water, while he prepared another float. Then he put the magnetized needle upon the new float, leaving the unmagnetized one upon the old float. They both looked almost precisely alike, each upon its own little disc of cork in its saucer of water.

"There," said he, "you cannot see any difference between them; but there is a great deal of difference between them; for one is only a common needle of steel, but the other has its two extremities magnetic in opposite ways."

To prove this, Rollo's father brought one end of the bar to the point of the magnetized needle, and the point was repelled. He brought it then to the eye of the same needle, and it attracted it. Then he brought the same end of the bar, first to the point, and then to the eye of the unmagnetic needle, and it attracted them both; so it was evident that there was a considerable difference, in reality, between the condition of the two, though there was no difference in external appearance.

"Now you see, from all this," added Rollo's father, "that when a magnet touches a piece of steel, like a needle, it immediately makes it a magnet itself; that is, it makes the two ends magnetic, one having one kind of magnetism, and the other the other kind; and then, if you take two magnets, and bring those two poles which have the same magnetism together, they repel one another; and if you bring those together which have different magnetisms, they attract each other."

"How do you know that they are the same magnetisms that repel, and different that attract?" said Rollo's mother.

"I will show you," said his father.

Then he took the needles that he had used off from their floats, and laid them away. He took next two new needles, exactly of a size, and he held them together between his thumb and finger, with the eyes projecting together. Then he rubbed them once or twice upon the end of Jonas's magnet, saying,

"There, you see I use both of these needles alike. Of course the eyes have both the same magnetisms. Now you will find that when I put one of them upon the float, and then bring the eyes together, they will repel each other; but an eye and a point will attract. So two points will repel."

"But you have not magnetized the points," said Rollo's mother.

"Yes," said his father. "When we magnetize one end, the other end becomes magnetized, itself, in the contrary way."

So he put one of the needles upon the float, and then brought the eye of the other down very near to its eye. It was repelled, as he had said it would be. He then brought the two points together, and they were repelled. But if he brought an eye towards a point, or a point towards an eye, they were attracted.

"This is the end of my lecture," said he, "for to-night."

"O, father," said Rollo, "a little more."

"No more to-night, only to recapitulate," said he.

"Recapitulate? what is that?"

"Why, tell you, briefly, the substance of what I have explained, so that you may remember it."

"Well, father," said Rollo.

"In the first place, a magnet has a peculiar and mysterious attractive power for iron, residing in its two extremities, which are called its poles; and the power which resides in one extremity is, in some way or other, opposite in its nature to that of the other extremity. Each of these poles repels a pole like itself, and attracts one different from itself, in any other magnet."

Poor Nathan could not understand this grave, philosophical disquisition very well, and he began to get pretty sleepy. He had, however, been somewhat amused, during the greater part of the time, in seeing the corks float about upon the water, with the needles upon them. So his father took the needles off, and let him have the two floats in one of the saucers to play with, a few minutes, while Dorothy put the other things away. He asked her to put all the things away together, so that they could get them ready the next evening, and then he said that perhaps he would give them another lecture.



INTELLECTUAL PHILOSOPHY

Rollo's father gave one or two other lectures upon magnetism, in the course of which Rollo found out a good deal about the subject; and, having learned from his father's explanations that any magnet, when balanced freely, would point to the north and south, that is, one end to the north and the other to the south, he determined to try the experiment. He accordingly poised a needle carefully upon a cork, as his father had done in his lecture, and put it in a basin of water upon the platform. But he did not succeed very well. The needle would always swing round, and turn its point towards the garden gate; but Rollo knew very well that the garden gate was not north from the platform. He remembered that the North Star was over the barn, for he and Jonas had noticed it particularly when they had made the dial. The needle, therefore, ought to have pointed towards the barn, according to his father's lecture; but it would not. Rollo took up a straw, and pushed the point of the needle round, and said, "Point there! point there, I tell you!" But all in vain. The needle would not heed either his pushing or his commands; but, as soon as he let it go, it would immediately swing back into its old position, where it pointed towards the garden gate.

Rollo was just about giving up in despair, when he saw his sister Mary coming in from the garden gate, with a book under her arm.

"O Mary," said he, "what shall I do? My needle won't point right."

"Why, what is the matter with it?" said Mary.

"It will point over towards the garden," said Rollo; "look."

So Mary came up, and looked at his needle. She saw that it was pointing towards the garden gate.

"Now I'll push it away," said Rollo, "and you will see that it comes directly back again."

So he took up his straw, and pushed the point of the needle away. The cork moved, turning round rapidly, until at length it swung away towards one side of the basin, and then suddenly drifted up against the side, and stuck there.

"That's another plague," said Rollo. "It will run up to the side of the basin, and stick there."

"What makes it?" said Mary.

"I don't know," said Rollo.

Mary sat down upon the platform, and examined the needle and the surface of the water very carefully. She observed that the water was heaped up a little against the side of the basin, all around. She asked Rollo to observe it.

"Yes," said he, "and the needle and cork run right up that ridge of water."

"And the bubbles too," said Mary.

Mary pointed, when she said this, to several little bubbles which were adhering closely to the side of the basin, in another place.

She took up a little straw, and pushed away some of the bubbles from the side of the basin, and then gently moved them back again until they were pretty near, and observed that they would immediately rush up against the side again. She did not understand this phenomenon, especially as the water was raised a little along the edge by the side of the basin, so that the bubbles and the needle actually appeared to rush up hill.

After examining this for some time, Mary moved the cork float, with the needle upon it, back into the middle of the basin, and then left it to itself. It slowly moved around until it pointed to the garden gate, as it had done before.

"Now what is the reason?" said Rollo; "that isn't north."

Mary looked upon it very attentively for a few minutes in silence, and then said, suddenly,

"O, I see."

"What?" said Rollo.

She did not answer, but pointed down to the platform by the side of the basin.

Rollo looked where she pointed, and saw the hammer lying there. He had had it to play with a short time before, and, when he brought the basin of water, he had laid it down by his side.

"What?" said Rollo.

"The hammer attracts the needle," replied Mary.

"The hammer?" said Rollo.

"Yes," replied Mary. "Don't you know that iron attracts the needle, and it will not point to the north if there is any iron near to draw it away?"

Rollo was just going to take the hammer up, but Mary stopped him, saying,

"Wait a moment. Let me take it away slowly, and see the effect."

So Mary told Rollo to watch the needle, while she carefully drew the hammer away.

Rollo did so. He and Mary both watched the needle. It was pointing pretty nearly toward the hammer, and when Mary gently moved the hammer away, the needle, released from the influence which the iron exerted upon it, slowly moved back towards the direction of the barn, that is, the direction of a north and south line, which is called the meridian.

"It's going back! it's going back!" said Rollo.

Mary said nothing, but watched it carefully. The needle swung beyond the direction of the meridian a little way, and then came slowly back again. So it continued vibrating from one side to the other, though to a less and less distance every time. Finally, it came to a state of rest; but it was not then, however, exactly in the meridian.

"What makes it swing so, back and forth?" said Rollo.

"I don't know exactly," said Mary. "I suppose the force that it moves with, carries it a little beyond, and then it is drawn back again, and that makes the oscillations."

"Oscillations?" said Rollo, inquiringly.

"Yes. They call this swinging back and forth, oscillating; and each movement is an oscillation."

"Is that the name of it?" said Rollo.

"Yes," said Mary. "When you tie a little stone to a string, and hold the upper end of the string still, and let the stone swing back and forth, it makes oscillations."

"I mean to try it," said Rollo.

"Yes," said Mary; "and I will help you by and by, after I have studied my philosophy lesson."

"Your philosophy lesson?" asked Rollo. "Have you got a philosophy lesson to get?"

"Yes," said Mary, "in that great book."

So Rollo took up Mary's book, which she had laid down upon the platform near Rollo's apparatus. He found that the title of it was "Intellectual Philosophy."

"Intellectual Philosophy?" said Rollo; "and what sort of philosophy is intellectual philosophy?"

"It is the philosophy of the mind," replied Mary. "It explains to us about the thoughts and feelings of our minds."

"Are there any experiments in intellectual philosophy?" asked Rollo.

"Yes," said Mary, "we can try experiments in intellectual philosophy."

"What experiments?" said Rollo.

"Why, there is a question whether we always dream when we are asleep."

"I do," said Rollo, "every night."

"Yes, but perhaps not all night long."

"Yes, I do," said Rollo. "I have good long dreams."

"But," replied Mary, "you may dream several hours in the night, so as to remember good long dreams in the morning, and yet perhaps you might have been, for some time, perfectly sound asleep, so as not to have any dreams in your mind at all. Some persons think we dream all the time when we are asleep, and others think we don't dream all the time. Now we might contrive some experiments to decide the question."

"How?" said Rollo.

"Why, you and I might agree to wake each other up several times, from a sound sleep, and then, if we were dreaming at that time, we should probably remember it."

"Well," said Rollo, "let us try it."

"That would be an experiment in intellectual philosophy," said Mary.

Rollo determined to try the experiment; and then he took Mary's book, and asked her where her lesson was that day. She found the place, and Rollo read a little. He could not understand it very well, and so he concluded that he would rather have Mary go and study her lesson, and then come down and help him make the experiments of oscillation.

Mary accordingly took her book and went in, and left Rollo at his play.



OSCILLATIONS.

In about an hour, Mary came down into the yard in pursuit of Rollo, in order to try the experiments which she had proposed.

When Rollo saw her coming, he left his play, and ran to meet her.

"Well, Mary," said he, "have you come to make the oscillations?"

"Yes," said Mary. "I have brought some thread for strings, and I want you to get some pebble stones—some large, and some small ones."

Rollo went for the pebble stones, while Mary looked about for a suitable place for making the experiments. In a corner of the yard there was a bench under a tree, and the branches came down pretty low. Mary thought that this would be a good place, for she could tie her strings to these branches with the pebbles hanging down below; and she and Rollo could watch the oscillations, while seated upon the bench.

Mary took her station here, and Rollo presently appeared, with the crown of his cap half filled with pebble stones. Mary said they would do finely. She poured them out upon the bench by her side, and Rollo put his cap upon his head again.

"Now, Rollo," said she, "we will study the art of experimenting."

"No," said Rollo, "we are going to study oscillation."

"Yes," replied Mary; "the experiments are to be on oscillations; but what I want principally to teach you, is, the proper way to make experiments."

"Well," said Rollo.

Mary said no more, but she proceeded to tie a small pebble to the end of one of the long threads which she had brought out with her. Then she tied the other end of the thread to the branch of the tree, which was over her head. The pebble then hung down before them, so that both Rollo and herself could plainly see all its motions.

"The first thing," said Mary, "is to get a clear idea of the nature of the oscillation, for we must know what we are experimenting about."

So saying, Mary carefully took hold of the suspended pebble stone, and began to draw it off towards one side. She showed Rollo that, as it was confined by its string above, it must move in a curved line when she drew it away from its place, rising higher and higher the farther it was drawn away. And when she had drawn it out to a considerable distance, to one side, it was at a much higher level, than when it hung down freely in its natural position.

"Now," said Mary, "you see that if I let it go, it will descend of course as much as it can, for the earth draws it downwards."

"The earth draws it?" said Rollo.

"Yes," said Mary. "The reason why things fall is that they are attracted, or drawn down, by the earth. Now the earth draws the pebble. It would go straight towards it, if it could; but the string confines it, and so it can only go down in the same way that it came up; that is, by the curved line."

Mary then held one of her hands open at the place where the pebble had hung when it had been at liberty, and let go the pebble, which she had been holding with the other. It fell down in the curved line, or arc, as Mary had said it would, until it struck her hand, and there it stopped and remained at rest.

"What did you stop it for?" said Rollo.

"So that we could see and attend to one part of the phenomenon at a time," said Mary; "that is, the descent of the pebble. You see the attraction of the earth causes the pebble to go down if it can, and the confinement of the string prevents its going down in any other way than in that curve or arc. For the string keeps it always just its own length from the branch, and so that makes the curved line the arc of a circle."

"Yes," said Rollo, "I understand."

Then Mary drew up the pebble once or twice more, and let Rollo see it fall against her hand. Rollo observed that it was a very regular arc.

"Now we see," continued Mary, "that I hold my hand so as to stop the pebble stone at the lowest point to which it can go; for I hold it exactly under the point where the upper end of the string is fastened to the tree. Now I will take my hand away, and then let the pebble fall, and we will see what takes place."

So Mary took her hand away, and let the pebble fall freely. It descended as before through the arc, and then, by the force which it acquired in moving so far, it was propelled beyond the lowest point, and ascended in another curve, upon the other side, similar to the first. When the force was expended, it came back again; and thus it swung to and fro, several times, and at length came almost to a state of rest.

"There," said Mary, "those are the oscillations we are going to experiment upon."

"Yes," said Rollo.

"And first," said Mary, "we notice that they are regular."

So she swung the pebble again; and as it moved to and fro, she counted the oscillations aloud, beating time with her hand, down and up, thus,—

"One,—two,—three,—four," &c. Rollo perceived that they were very regular.

"Now, first we will endeavor to ascertain by our experiments," said Mary, "what the time of the vibrations depends upon."

"Well," said Rollo.

"You see," continued Mary, "it swings back and forth with a certain degree of rapidity. Now we want to know what this rapidity depends upon, and then we could make a pendulum so that it would oscillate faster or slower, just as we pleased."

"A pendulum?" asked Rollo.

"Yes," said Mary, "we call it a pendulum. Any heavy body hung in this manner, so as to swing back and forth by its weight, is called a pendulum. So that we are experimenting upon the oscillations of a pendulum."

"Yes," said Rollo, "I understand."

"Now the question which we are going to examine," said Mary, "is, what the rapidity of the vibrations depends upon."

"O, it depends upon the bigness of the pebble," said Rollo.

"How do you know?" said Mary.

"Why, of course, a bigger pebble will be heavier, and will fall quicker, and that will make it vibrate faster."

"That is reasoning about it," said Mary, "and what we want to do, now, is to experiment. Now, in order to decide it by experiment, we must try two pendulums, one with a small pebble, and the other with a large one."

"Very well," said Rollo, "we will; and then we shall see that the big one will vibrate the quickest."

"Let us think, first, what other circumstances there are, that it may depend upon."

"I can't think of any thing else," said Rollo.

"Why, there is the nature of the body which we suspend. A piece of cork may oscillate differently from a piece of stone."

"Yes," said Rollo, "it will oscillate slower."

"We must not decide," said Mary, "in our own minds, before we try the experiment. We must leave our minds free to observe the facts, and wait until we make the experiment, before we come to any conclusion, or else we shall not be good experimenters."

"Why not?" said Rollo.

"Because," said Mary, "when persons make up their minds beforehand what the facts will be, they are very apt not to observe fairly. So good observers or experimenters always take care to keep their minds free and unbiassed."

"Well," said Rollo, "and what else is there that the oscillations may depend upon?"

"The length of the string," replied Mary.

"O yes," said Rollo, "it may depend upon that."

"Let us see," continued Mary. "There are three experiments we have already proposed; a large and a small pebble; a pebble and a cork; a long and a short string; and now there is one more,—a long and short arc."

"How?" said Rollo.

"Why, if I draw up the weight, which forms the pendulum, pretty high, it will swing back and forth through a long arc. But if I move it only a little way, it will swing through only a short arc, and that may make a difference in the length of the vibrations."

"Well," said Rollo, "and now let us try."

"First, let us see whether we have got all the apparatus we want. Here are strings and pebbles,—only we want a cork."

"I'll go and get one," said Rollo.

So Rollo went off towards the house to get the cork. In a few minutes he came back, saying,

"I have got the cork. Now how shall we begin?"

"First," replied Mary, "we will try what effect the weight of the pebble will have upon the oscillations."

"Very well," said Rollo.

"Now, in order to test that," added Mary, "we must take two pebble stones, of different sizes, and hang them together, by strings of the same kind, and of the same length; and then we must set them a-going exactly together, and then watch the oscillations. You see that as they will be alike in every respect, excepting the size of the pebble stones, whatever difference there is in the mode of vibration will probably be caused by the difference in the size of the stones."

"Is that the way they do it?" said Rollo.

"Yes," replied Mary. "Whenever we want to know what effect any one circumstance produces, in such a case, we always arrange two experiments, making them very different in respect to the circumstance which we wish to examine, and as nearly alike as possible in all other respects."

"I think that is a very good way," said Rollo.

"Yes," replied Mary, "I think it is an excellent way."

While Mary was thus explaining her plan to Rollo, she was going on steadily with preparations, Rollo standing all the time by her side, looking on with great interest. Mary selected two pebbles. One was as big as a walnut, and the other about as big as an egg. She tied two of her threads to these stones, one to each, and then tied the other ends of these threads to a small branch of the tree which extended horizontally over their heads. They hung down about two feet. She took care so to adjust the strings, as to have the centres of the stones as nearly as possible on a level.

"The big one is twice as large, and so it will go twice as fast," said Rollo.

"We shall see," said Mary.

She then drew them both carefully out a little way on one side, and holding them there steadily a moment, she let them go. They immediately began to swing back and forth, together.

After a few oscillations, however, the large stone began to gain a little upon the other, and seemed to be moving faster. Presently it had gained half an oscillation, i. e. when the large one was moving forward, the small one would be coming back.

"The big one moves the fastest," said Rollo.

"Not much," said Mary.

"No," said Rollo, "not much."

"And I don't think it is owing to the difference in the bigness of the stones."

"What else can it be?" said Rollo. "They are exactly alike in all other respects."

"Not exactly," said Mary. "We have made them as nearly alike as we could, but not exactly. There may be a good many little differences that we do not observe. But if the size of the stone would cause any difference in the vibrations, I should think it would make a much greater difference, for one is twice as big as the other."

"Let us try a very big stone," said Rollo.

"Well," said Mary.

So Rollo got a stone as large as an orange, which was as heavy a one as Mary thought the thread would hold; and Mary suspended that from the branch of the tree, and then swung it in company with the two others. They all went very nearly together at first, though there was evidently a slight difference, which, in a short time, separated the oscillations, so that the stones did not keep together; while yet they each swung back and forth, in nearly the same time. Rollo and Mary both concluded, from the result of this experiment, that the size of the vibrating body did not perceptibly affect the rapidity of the vibrations.

"Now," said Mary, "we will try different lengths of string."

So she began to look over Rollo's pebbles, to find two as nearly as possible alike.

"The pebble stones must be of the same size, this time, for we want the two pendulums to be alike in all respects, except the length of the string, for that is the circumstance which we are now going to consider. We will have one string twice as long as the other."

Mary found two pebbles very nearly equal in size, and similar in shape. She tied them to two strings, making one string twice as long as the other. She suspended them as before, and then, taking hold of one with one hand, and the other with the other, she drew them out to the same distance on one side, and let them go. The short one began at once to swing back and forth very quick, while the other followed quite slowly.

"That makes a difference," said Rollo, clapping his hands.

"It goes twice as fast," said Mary.

"More than twice as fast," said Rollo, "I think."

"Let us see," said Mary.

They set them vibrating again; but they did not succeed in ascertaining whether the short one went more or less than twice as fast as the other. The two motions, so rapid and so near together, confused them. At length, Mary proposed that Rollo should count the vibrations of the long pendulum, while she counted those of the short one, and when she had got up to twenty, she said they would both stop, and then Rollo could tell how many he had got in the same time. But this plan, though apparently a very simple one, they found it somewhat difficult to put into practice. Mary's pendulum puzzled Rollo's counting, and Rollo, who could not count very well without at least whispering the numbers, puzzled Mary, and so pretty soon they gave it up.

Rollo then said that he meant to try a very short pendulum indeed, and he asked Mary to tie one up for him, not more than an inch in length. She, however, said that it would not be necessary to tie it to the branch; but, instead of that, she took hold of the string of one of the pebbles which was already hanging before them, about an inch above the pebble itself, and then set the pebble in motion; and they were both very much interested in observing how quick it vibrated to and fro.

Rollo then wanted to try a very long one, and proposed that he should climb up into the tree, and tie the end of the string to a high branch. But Mary was afraid that he would fall; and besides, she said that the pendulum would not swing clear of the branches below. She, however, immediately thought of the chamber window, and said that she would try it there. She accordingly went up into her chamber, taking a large pebble stone with her, and Rollo remained below to set the pendulum in motion, when it should be ready. Mary soon appeared at the window, and Rollo watched her while she tied her pebble to the end of a thread.

"Have you got your thread long enough?" said Rollo. "It will take a good long thread to reach away down here."

"It is a whole spool of cotton," said Mary. And, so saying, she held up in her hand the spool, to the thread of which she was tying her pebble stone.

When it was secured, she slowly let it down, until it reached Rollo's hand, which was held up from below, ready to receive it. Mary then held the thread steady above, at a little distance out from the window, while Rollo took the stone along the side of the house, three or four feet from the place where it would naturally hang. He then let it go, and it swung back very slowly.

"O, how slow!" said Rollo.

"Yes," said Mary, "it is very slow, indeed."

"I wish you had gone up to the garret window," said Rollo.

"O, this will do very well," said Mary.

Rollo determined to see how many he could count while the stone made one oscillation to and fro. He counted sixteen.

Mary then said she was tired of experimenting, and so she should not come down again. She, however, asked Rollo to set the pendulum swinging, and that then she would draw the thread in, and he could see that it would go faster and faster, the farther she drew it up, for that would make the string grow shorter and shorter.

Rollo did so; and this was the end of the experiments on oscillations.



TRANSCRIBER'S NOTES

The following corrections have been made to the text:

Page 14: She looked on with a good deal{original omitted this word} of interest

Page 32: "What is satiety, father?"{original had a single quotation mark instead of the double one}

Page 88: Then he stirred{original had stirrred} it about with his hand

Page 122: he took hold of the flower-pot with both his hands, and slid it suddenly off of the seat.{the original had a footnote here, See Frontispiece. The frontispiece however relates to a different chapter (Pruning) and so the footnote has been removed}

Page 149: and the small end{original had and} of the magnet would draw the point of the needle

THE END