“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.”