Page:Incandescent electric lighting- A practical description of the Edison system.djvu/31

 these, is supposed to be the wire that carries the current to the lamps^ the location of which is shown by the dotted portion of the heavy line; the direction of the current in the same being indicated by the small arrows as proceeding from the upper to the lower brush.

The fine wire passing from the upper to the lower brush is shown as being coiled about both legs of the magnet, and terminating in the lower brush. The office of this wire is to magnetize the iron in the electro-magnet, and it is made smaller than the lamp wire, because only a small portion of the current generated in the armature is intended to flow through it, the greater portion being utilized in the lamps.

Fig. 8 gives a clear illustration of this, the lamps being shown as they are arranged in practical lighting. Here also is shown, what is termed a resistance box^ which is a box filled with a large number of coils of wire, made of material that will not readily conduct electricity, and so arranged as to be capable of being