Rollo's Experiments Part 14

"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 ma.s.s, 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 acc.u.mulation of the black particles of sand. Rollo's father then took up the bar carefully, and pa.s.sed 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 cl.u.s.ter 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.