The earliest arc lamps were operated such that their carbon rods pretty much burned in the "open" compared to the subsequent "enclosed" (c.1890) style. The middle photo shows one of these earliest arc lights which were principally the first used for street lighting service. The open style lights (these had open-ended clear globes around the rods) required carbon rod maintenance at least every couple days and were less efficient than the enclosed style arcs. In some cases "specially colored" insulators (blue and amber) were used as delineators so that the wires which operated arc light (and other street light) circuits could be readily identified. Many of our cobalt, peacock blue, amber and "glower" insulators of the circa 1880-1920 period in the CD 134 and 162 styles were used for street lighting applications. More photos of arc lights in service with insulators and old-time pole line construction are shown in a couple subsequent pages within this folder. Enjoy!