e iron may actually require a small amount of initial
energy to dislodge them therefrom, so that after being dislodged they
may collapse and yield whatever energy they represent.

I must reserve for the future further consideration of the iron ring,
but in thinking upon this matter I am led to think that the production
of a magnetic line in an iron ring around a conductor may represent a
sort of wave of energy, an absorption of energy on the evolution of
the line from the conductor, and a slight giving out of energy on the
line reaching that position of proximity to the iron ring, that its
passage thereto may be said to be a shortening process or a lessening
of its resistance.

The magnetism in air, gases, and non-magnetic bodies, being assumed to
be that of the ether, this medium shows no such effects as those we
get with the ring. It does not become permanently polarized, as does
even soft iron under the condition of a closed ring. The iron
possesses coercive force, or magnetic rigidity, and a steel ring would
show more of it. The molecules of the iron or steel take a set. If we
were to cut the soft iron ring, or separate it in any way, this
introduction of resistance of air for ether in the magnetic circuit
would cause the lines to collapse and set up a current in the
conductor. The energy of the ring would have been restored to the
latter. The curious thing is that physically the polarized ring does
not present any different appearance or ordinary properties different
from those of a plain ring, and will not deflect a compass needle. Its
condition is discoverable, however, by the test of self-induction to
currents of different direction. As a practical consideration, we may
mention in this connection that a self-inductive coil for currents of
one direction must be constructed differently from one to be used with
alternating currents. The former must have in its magnetic circuit a
section of air or the like, or be an imperfectly closed circuit, as it
were. The latter should have as perfectly closed a magnetic circuit as
can be made. We see here also the futility of constructing a Ruhmkorff
core coil on the closed iron magnetic circuit plan, because the
currents in the primary are interrupted, not reversed.

The considerations just put forward in relation to the closed iron
ring, and its passive character under the condition of becoming
polarized, are more important than at first appears. It has been found
that the