remedies for the
eddy current difficulty, notably the stranding and twisting of the
conductor on the armatures so as to average the position of the parts
of the compound conductor.

[Illustration: Fig. 9.]

Perhaps the most extreme case of what may be called dilution of field
by projections and by closed magnetic circuits in transformers would
be that of a block of iron, B, Fig. 10, moved between poles, N and S,
and having a hole through it, into and through which a conductor is
carried. The path through the iron is so good that we can scarcely
consider that any lines cross the hole from N to S; yet as B moves
forward there is a continual snapping transfer of lines from the right
forward side of the hole to the left or backward side, cutting the
conductor as they fly across, and developing an electromotive force in
it. I have described this action more in detail because we have in it
whatever distinction in the manner of cutting the lines of the field
is to be found between wire on smooth armatures and on projection
armatures and modifications thereof; and also between flat, open coils
passing through a field and bobbins with cores of iron. The
considerations advanced also bring out the relation which exists
between closed iron circuit transformers and closed iron circuit
(projection) dynamos, as we may call them.

[Illustration: Fig. 10.]

I had intended at the outset of this paper to deal to some extent with
the propagation of lines of magnetism undergoing retardation in
reference to alternating current motor devices, transformers with
limited secondary current, or constant average current, an alternating
motor working with what I may term a translation lag, etc.; but it was
soon found that these matters must remain over for a continuation of
this paper at some future time. My endeavor has been in the present
paper to deal with the lines of force theory as though it were a
symbol of the reality, but I confess that it is done with many
misgivings that I may have carried it too far. Yet, if we are to use
the idea at all it has seemed but right to apply it wherever it may
throw any light on the subject or assist in our understanding of
phenomena.

* * * * *

ELECTRIC LIGHTING AT THE PARIS EXHIBITION--THE OERLIKON
WORKS.

Immediately on entering the Machinery Hall by the _galerie_ leading
from the central dome, and occupying a prominent position at the
commencement of the