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figure, is that need in the Edison system of incandescent electric lighting.
The pole pieces rest upon blocks of zinc, which do not interfere with their magnetized condition; and this zinc is in turn supported upon an iron base, the whole being secured together so as to form a neat and compact machine as shown in Fig. 9.
Before proceeding to discuss the means and devices for utilizing the electric current, let us be quite sure that we fully understand the several parts of the generator, or Dynamo, as it is commonly called, their individual purpose, action upon, and relation to each other. First are the electro-magnets known as "field-magnets" with their ends or "poles" enlarged by the "field-pieces" between which is the space known as the "field Of force" or "magnetic-field," in which revolves the "armature" having its several "coils" of wire connected to the strips of the "commutator," these strips having intimate contact with the "brushes" resting upon them, which
