English: Birkeland-Eyde's electric arc furnace, exhibited in a park in Rjukan, Norway. Furnace plaque information: "The furnace was invented and constructed by professor Kristian Birkeland and dr.ing. H.C. Sam Eyde for the fixation of atmospheric nitrogen. Furnaces of this type were in operation at Rjukan from 1912 to 1940. From 1928 the elctric arc process was gradually replaced by the ammonia synthesis process."