Werderman electric lamp. Engraving of Werderman electric lamps illuminating the Paris Opera foyer, France, in 1881. These lamps were carbon arc lamps consisting of a pair of carbon rods. Through these rods a massive voltage was applied. The high voltage caused sparks to arc across the two rods. It also caused the carbon to vaporize, this caused a continuous glow. Werderman lamps used weights to maintain a constant gap in the carbon arc.