outer face of the inner ring, is 0.40 in. The latter is movable, and
is supported by three wooden arms, F, fixed to a boss, G, which is
traversed by a spindle supported in bearings by the columns, A and C.
A coil is rolled around the ring in exactly the same way as that on
the outer ring, the wire being of the same size, and the insulation of
the same thickness. The ends of the wire are also bared at points of
the diameter opposite each other, and the coil connected in pairs so
as to form a continuous circuit. At the two points of junction they
are connected with a hexagonal commutator placed on the central
spindle, one end corresponding to the sides 1, 3, and 5, and the other
to the sides 2, 4, and 6. Two copper rods, J, fixed on the base to two
plates of copper furnished with binding screws, are widened and
flattened at their upper ends to rest against opposite parallel sides
of the hexagon. It will be seen that if the battery is put in circuit
by means of the binding screws, the current in the interior ring will
determine six consecutive poles, the names of which will change as the
commutator plates come into contact successively with the sides of the
hexagon. Consequently, if at first the pole-pieces opposite each other
are magnetized with the same polarity, a repulsion between them will
be set up which will set the inner ring in motion, and the effect will
be increased on account of the attraction of the next pole of the
outer ring. At the moment when the pole piece thus attracted comes
into the field of the pole of opposite polarity, the action of the
commutator will change its magnetization, while that of the pole-piece
on the fixed ring always remains the same; the same phenomenon of
repulsion will be produced, and the inner ring will continue its
movement in the same direction, and so on. To the attractive and
repulsive action of the magnetic poles has to be added the reciprocal
action of the coils around the two rings, the action of which is
similar. From this brief explanation the differences between the Elias