On the Magnet/III-5

On the Touching of pieces of Iron
of divers shapes.

Gilbert De Magnete IlloB.jpg
ars of iron, when touched by a loadstone, have one end north, the other south, and in the middle is the limit of verticity, like the æquinoctial circle on the globe of a terrella or on an iron globe. But when an iron ring is rubbed on one side on a * loadstone, then the one pole is on the place that was in contact, whilst the other is at the opposite point; and the magnetick power divides the ring into two parts by a natural distinction which, though not in shape, yet in power and effect is like an æquator. But if a thin straight rod be bent into a ring without any welding or union of the ends, and be touched in the middle by a loadstone, both ends will be of the same verticity. Let a ring be taken which is whole and continuous, and which has been * touched by a loadstone at one place, and let it be divided afterward [ 130 ] at the opposite point and straightened out, both ends will also be * of the same verticity, no otherwise than a thin rod touched in the middle or a ring not cohærent at the joint.