"Is that the reason it is stated that likes repel and unlikes attract?"
"Yes."
In order to take advantage of this knowledge, knowing that the earth is a great permanent magnet, it was necessary to make a small magnet, and so suspend it that it would turn freely, and the magnetic north and south could then be determined.
To do this the battery which had been previously made was brought into play. George took a hand in the work, and while they were preparing the metal for the little bar, said: "You spoke about a permanent magnet. What other kinds of magnets are there?"
"Magnets are permanent or temporary. A permanent magnet is one in which the electricity resides, or remains, as it does in the earth. A temporary magnet is one which has magnetism imparted to it only while a current of electricity is passing around it."
"How is the current made to pass around it?"
"By wrapping an insulated wire around it, and sending a current through the wire. When that is done the same thing is done to the bar as the bar of the permanent magnet exhibits. As soon, however, as the current through the wire ceases, the bar is again demagnetized. That is, it ceases to be a magnet."
"We have the small bars ready, Professor. What is the next step?"
"It must be hardened so as to make it a flinty steel. The harder the better, so that it will preserve the magnetism imparted to it."
"Is that the better way to make the temporary magnet?"