Page:Incandescent electric lighting- A practical description of the Edison system.djvu/37

 in it are located the incandescent lamps.

The field circuit takes its name from its office of furnishing the necessary current for the excitation of the field-magnets.

Having located and arranged all the parts of the generator, let us proceed to note how they act upon each other.

Attached to the shaft of the armature, is an iron^ wheel or pulley, about which passes the belt from a steam engine. When the engine is started, this belt transmits its motion to the pulley, rapidly revolving it and the armature upon the shaft with it.

As the armature revolves, the wire round about it is acted upon by the residual magnetism in the field pieces; this excites a slight current in the armature, a part of which passes out to the lamp circuit, the remainder passing through the field circuit and increasing the magnetism in the fields, which act somewhat more strongly upon the armature, increasing and strengthening the current passing from it, which in turn acts upon