that of the primary current
when the latter current was changing from zero to maximum positive or
negative current, so producing repulsion; and would be induced in the
same direction when changing from maximum positive or negative value to
zero, so producing attraction.

This condition can be illustrated by a diagram, Fig. 12. Here the lines
of zero current are the horizontal straight lines. The wavy lines
represent the variations of current strength in each conductor, the
current in one direction being indicated by that portion of the curve
above the zero line, and in the other direction by that portion below
it. The vertical dotted lines simply mark off corresponding portions of
phase or succession of times.

[Illustration: FIG. 15]

Here it will be seen that in the positive primary current descending
from m, its maximum, to the zero line, the secondary current has risen
from its zero to m, its maximum. Attraction will therefore ensue, for
the currents are in the same direction in the two conductors. When the
primary current increases from zero to its negative maximum, n, the
positive current in the secondary closed circuit will be decreasing from
m, its positive maximum, to zero; but, as the currents are in opposite
directions, repulsion will occur. These actions of attraction and
repulsion will be reproduced continually, there being a repulsion, then
an attraction, then a repulsion, and again an attraction, during one
complete wave of the primary current. The letters, r, a, at the foot of
the diagram, Fig. 12, indicate this succession.

In reality, however, the effects of self-induction in causing a lag,
shift, or retardation of phase in the secondary current will
considerably modify the results, and especially so when the secondary
conductor is constructed so as to give to such self-induction a large
value. In other words, the maxima of the primary or inducing current
will no longer be found coincident with the zero points of the secondary
currents. The effect will be the same as if the line representing the
wave of the secondary current in Fig. 12 had been shifted forward to a
greater or less extent. This is indicated in diagram, Fig. 13. It gives
doubtless an exaggerated view of the action, though from the effects of
repulsion which I have produced, I should say it is by no means an
unrealizable condition.

[Illustration: Fig. 16.]

It will be noticed that the period during which the currents are
opposite