The best method of proving this is to take a magnet or a piece of steel
rendered magnetic, and to place it on a piece of cork by laying it in
a groove cut to receive it. If the cork be placed in the center of a
basin of water, and allowed to swim freely on its surface, so that it
is not attracted by the sides of the basin, it will be found to turn
its north pole to the north, and its south pole to the south, the same
as the mariner’s compass. If you fix two magnets in two pieces of cork,
and place them also in a basin of water, and they are in a parallel
position with the same poles together, that is, north to north, and
south to south, they will mutually repel each other; but if the
contrary poles point to one another, as north to south, they will be
attracted.