CD 1963048 E&MP 22.005
August 17, 1938
Corona glow, formed by an electric discharge in carbon monoxide gas inside this bell jar induction furnace provided the light used to make this photograph. The copper tubing, part of which is illuminated by corona, carries 10,000 cycles of current every second to induce a high frequency current in the charge of iron ore, causing the metal to melt itself, giving up its carbon which combines with oxygen and is drawn off through the vacuum of the bell jar. The result is iron 99.99 per cent pure.