“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.