electro-magnet, by embracing a sufficiently large number of the iron
projecting pieces on the armature ring, continue to exercise an
influence upon them almost up to the point at which their
magnetization ceases when passing the neutral axis. (5) By the method
of construction adopted, sparks, while being increased in number, are
diminished in intensity, there being no powerful extra currents
produced at the breaking of the circuit, and Dr. Pacinotti points out
that when the machine is in rotation a continuous current is induced
in the circuit which is opposed to that of the battery; and this leads
to what, looked at by the light of the present state of electric
science, is by far the most interesting part of Dr. Pacinotti's paper,
published, as it was, more than seventeen years ago.

In the part to which we refer, Dr. Pacinotti states that it occurred
to him that the value of the apparatus would be greatly increased if
it could be altered from an electro-magnetic to a magneto-electric
machine, so as to produce a continuous current. Thus, if the
electro-magnet, A B (Figs. 3 and 4), be replaced by a permanent
magnet, and the annular armature were made to revolve, the apparatus
would become a magneto-electric generator, which would produce a
continuous induced current always in the same direction, and in
analyzing the action of such a machine Dr. Pacinotti observes that, as
the position of the magnetic field is fixed, and the iron armature
with its coils rotates within it, the action may be regarded as the
same as if the iron ring were made up of two fixed semicircular
horseshoe magnets with their similar poles joined, and the coils were
loose upon it and were caused to rotate over it, and this mode of
expressing the phenomenon was exactly what we adopted when describing
the Gramme machine, without having at that time seen what Dr.
Pacinotti had written fifteen years before.