represent, in side view and plan, the armature pulley with the soft iron
rim and coils attached. There a is the pulley which is keyed to the
shaft of the machine, and is encircled with bands of sheet iron, b,
insulated from each other by ribbons of asbestos paper laid between
every two bands. When the rim has been built up in this way, radial
holes are drilled through it from the outer edge inward, and the whole
rim is bound together by bolts, d, inserted in the holes and secured by
cottars, e. Radial slots are then cut on each side of the rim all round,
and the coils of wire mounted on them.

Figs. 3 and 4 show the armature of the continuous current dynamo, with
the coils on one side of the rim, half way between the coils on the
other side, so as to give a more continuous current. In the alternating
current machine the slots on the opposite faces are face to face.

Figs. 5 and 9 illustrate the complete continuous current machine, Fig.
9 showing the internal arrangement of the field magnets, and Fig. 5 the
external frame of cast iron supporting them. In these figures a is the
armature already described, b b are the cores of the electro-magnets
with a strong cast iron backing, c c; d d are the exciting coils or
field magnets, so connected that the poles presented to the armature are
alternately north and south, thus bringing a south pole on one side of
the armature opposite a north pole on the other side.

The commutator, e, is arranged to prevent sparking when the brushes
leave a contact piece. This is done by splitting up the brushes into
several parts and inserting resistances between the part which leaves
the contact piece last and the rest of the circuit. This resistance
checks the current ere the final rupture of contact takes place.