regulator magnet is so formed as to give a uniform attraction upon
its armature in different positions. In Thomson's improved form this
is accomplished in a novel manner by making the pole of the magnet
paraboloidal in form, and making an opening in the movable armature to
encircle said pole.

[Illustration: THE CURRENT REGULATOR]

The armature is hung on pivots so as to be free to move only toward
and from the regulating magnet on changes in the current traversing
the latter, and being connected to the commutator brushes,
automatically adjusts their position. By this means the power of the
generator is adapted to run any number of lights within its limit of
capacity, or may be short circuited purposely or by accident without
difficulty arising therefrom; and a number of instances have occurred
where the injurious effects of a short circuit accidentally formed
have been entirely obviated by the presence of the regulator. In one
instance four generators, in series representing over forty lights'
capacity, were accidentally short circuited, and no injury or even
noticeable action took place except a quick movement of the regulators
in adapting themselves to the new conditions. Had this accident
occurred to generators unprovided with regulators, great injury or
possible destruction of the apparatus would have resulted. It is
important to a full understanding of the regulation, to state that its
action is independent of resistances introduced, that it saves power
and carbons in proportion to lights extinguished, and that it
compensates for speed variations above the minimum speed. The manner
of its action is to control the generation of current at the source in
the armature, and it does so by combining certain electrical actions
so as to obtain a differential effect, such that when small force of