The effect of heat and of solvents on thin films of metal

In the Bakerian Lecture of 1857,* on “ Experimental Relations of Gold and other Metals to Light,” Faraday described a series of experiments which were designed to throw light on the structure and behaviour of metals in their most attenuated forms. Probably the most remarkable of these experiments were those in which leaves and films of gold and silver supported on glass were changed by a temperature much below the melting point of the metal from a moderate translucence to clear transparence and from high metallic reflecting power to comparative deadness. These remarkable experiments seem practically to have dropped out of sight during the past 45 years for, so far, I have found no reference to this particular phenomenon in the papers of more recent workers on the reflecting and absorbing powers of thin metal films, and many physicists to whom I have shown these Faraday films have received them as a novelty.