Page:Incandescent electric lighting- A practical description of the Edison system.djvu/47

, as it has economical advantages, which are not possessed by any other method that has been in practical operation up to the present time for commercial lighting on a large scale.

In the two-wire system, the lamps are arranged between the two large conductors, in what is called multiple arc or parallel; that is they are arranged like the rounds of a ladder between the main conductors.

This arrangement leaves each lamp independent of all others, so that any one may be turned on or off without interfering with those that remain burning. In order, however, that the lamps farthest removed from the generator shall have as much current as those nearest to it, the main conductor must of necessity be so large as to present practically no resistance to the passage of the current; for this reason the two-wire system cannot well be used, under conditions requiring the current to be led a long distance to the point where the lights are to be used, as the cost of the large