+ 10° 10° Horizontal a Horizontal - 10° 10° sit y M ax In te n 30° 40° 20° im um M ax im um 20° In te 30° ns ity 40° 50° 50° 60° 60° 70° 80° 90° 80° 70° figure 3. Light distribution from the arc. (From Electric Lighting and Railways. Scranton, PA: ICS, 1901. lamps have an outer globe to protect the arc from the weather and keep the arc's high temperature and the electrode's voltage from coming in contact with workers. Notice that the light is projected down toward the street with practically none of it projected upwards. this makes it very suitable for street lighting, although the area directly under the light is darker than that a few feet out. because of the intense light from the arc, the shadows thrown by it are very prominent. the carbon vapor from the arc readily combines with oxygen in the surrounding air. this forms a deposit on the outer globe that requires frequent maintenance. more important, however, is the fact that this combined carbon vapor results in a rapid erosion of the carbons. The Grid Made Real Essential to the Real Sustainable Power Grid April 2018 IEEE PES T&D Show in Denver, CO. Booth 106 58 ieee power & energy magazine january/february 2018