Page:Incandescent electric lighting- A practical description of the Edison system.djvu/51

 consequently the electro-motive force to overcome that resistance must also be doubled; and we must now have 180 volts at the lamps, but not so with the current. The lamps being now arranged two on the same wire, the current which passes through one will pass through both; and now instead of having one ampere to each lamp, we have one ampere to each two lamps, or live amperes for the ten lamps.

This is just one half of the current used in the first case, as illustrated at A, we have therefore, by the removal of the two conductors, reduced our wires one half, and by the change in the arrangement of the lamps, have reduced our current one half. Since this arrangement, while an excellent one, has the disadvantage that the two lamps coupled together are dependent upon each other, and neither can be extinguished, without cutting off the supply of current from the other; to obviate this defect we have a third wire extending from the junction of the two dynamos, and