Adams-Bagnall Company Regenerative Flame Arc Lamp Carbon Rod, circa 1911

Carbon rods, like these, were used in arc lamps, the first widely used form of electric light in the late 1800s. The lamp's brilliant light, created by an electric arc between precisely spaced rods, effectively illuminated city streets, factories, and other large areas--though falling sparks could prove hazardous. Eventually, improvements in other types of arc discharge lamps made carbon rods virtually obsolete.