The use of the rare metals and the metallic earths is another characteristic advance of this phase: tantalum, tungsten, thorium, and cerium in lamps, iridium and platinum in mechanical contact points -the tips of fountain pens or the attachments in removable dentures-and of nickel, vanadium, tungsten, manganese and chromium in steel. Selenium, whose electrical resistance varies inversely with the intensity of light, was another metal which sprang into wide use with electricity: automatic counting devices and electric door-openers are both possible by reason of this physical property. (Mumford 1934:231)
MUMFORD, Lewis. 1934. Technique and civilization. New York: Harcourt, Brace and Company.