More than a thousand years before our era, a people living in the
extremest eastern portions of Asia had magnetic carriages, on which the
movable arm of the figure of a man continually pointed to the south,
as a guide by which to find the way across the boundless grass-plains
of Tartary; nay, even in the third century of our era, therefore at
least 700 years before the use of the mariner’s compass in European
seas, Chinese vessels navigated the Indian Ocean under the direction of
Magnetic Needles pointing to the south.
Now the Western nations, the Greeks and the Romans, knew that
magnetism could be communicated to iron, and _that that metal_
would retain it for a length of time. The great discovery of
the terrestrial directive force depended, therefore, alone
on this--that no one in the West had happened to observe an
elongated fragment of magnetic iron-stone, or a magnetic iron rod,
floating by the aid of a piece of wood in water, or suspended
in the air by a thread, in such a position as to admit of free
motion.--_Humboldt’s Cosmos_, vol. i.