Rollo's Experiments Part 16

"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 pus.h.i.+ng 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.