Around 1900, the arc light or carbon arc began to replace the limelight, largely because the arc light was more economical. An extremely bright, even harsh, white light was produced by the electric spark that jumped between two carbon electrodes. This technology came into use for special effects (bright sun, lightning, etc.) in the 1880s. The later addition of a parabolic reflector behind the rods allowed the light to be concentrated, and the carbon arcs could then be used as follow spots.
See also lighting.
The Historical Dictionary of the American Theater. James Fisher.