He showed that the earth was a great magnet with a north pole and a south pole, by comparing it to lodestones made into spheres in which a north and south pole could be found by intersecting lines of magnetism indicated by a needle on the stone.
"Our Legal Heritage"
S. A. Reilly
"He carries lodestones of great power and divers subtle tools," Sid had explained for him.
"No Great Magic"
Fritz Reuter Leiber