SUPERPOSED MAGNETISM.

Knowing that by torsion we can rotate or diminish magnetism, I was
anxious to obtain by its means a complete rotation from north polarity
to neutrality, and from neutrality to south polarity, or to completely
reverse magnetic polarity by a slight right or left torsion.

I have succeeded in doing this, and in obtaining strong reversal of
polarities, by superposing one polarity given while the rod is under a
right elastic torsion, with another of the opposite polarity given under
a left elastic torsion, the neutral point then being reached when the
rod is free from torsion. The rod should be very strongly magnetized
under its first or right-hand torsion, so that its interior molecules
are rotated, or, in other words, magnetized to saturation; the second
magnetization in the contrary sense and torsion should be feebler, so
as only to magnetize the surface, or not more than one-half its depth;
these can be easily adjusted to each other so as to form a complete
polar balance of force, producing, when the rod is free from torsion,
the neutrality as shown at B, Fig. 1.

The apparatus needed is simply a good compound horseshoe permanent
magnet, 15 centimeters long, having six or more plates, giving it a
total thickness of at least 3 centimeters. We need a sufficiently
powerful magnet, as I find that I obtain a more equal distribution of
magnetism upon a rod or strip of iron by drawing it lengthwise over a
single pole in a direction from that pole, as shown in Fig. 2; we can
then obtain saturation by repeated drawings, keeping the same molecular
symmetry in each experiment.