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. Figs. 6 and 7 will explain the structure of the commutator. Here a a a are the segments or contact pieces insulated from each other, and b' b b are the collecting brushes carried on a spindle, c c'. One of these brushes, b', is connected to the spindle, c, through an electrical resistance of plumbago, arranged as shown in Fig. 7, where d e are metal cylinders, d being in contact with the brush, b', while e is in contact with the spindle, c. The space, f, between these two cylinders, d e, is filled with a mixture of plumbago and lampblack of suitable resistance, confined at the ends by ivory disks. The brush, b', is adjusted by bending till it remains in contact with any segment of the commutator for a short time after the other brushes have left contact with that segment, and thus instead of sudden break of circuit and consequent sparking, a resistance is introduced, and contact is not broken until the current has been considerably reduced. The contact segments are supported at both ends by solid insulating disks; but they are insulated from each other by the air spaces between them, where the brushes rub upon them.