THERMOELECTRICITY, electricity produced at the junction of two metals, or at a point where a molecular change occurs in a bar of the same metal, when the junction or point is heated above or cooled below the general temperature of the conductor. Thus when wires or bars of metal or different kinds, as bismuth and antimony, are placed in close con tact, end to end, and disposed so as to form a periphery or continuous circuit, and heat then applied to the ends or junctions of the bars, electric currents are produced. The thermoelectric battery, or pile, an apparatus much used in delicate experiments with radiant heat, consists of a series of little bars of antimony and bismuth (or any other two metals of different heat-conducting power), having their ends soldered together and arranged in a compact form; the oppo site end of the pile being connected with a galvanometer, which is very sensibly affected by the electric current induced in the system of bars when exposed to the slightest variations of temperature.
To the combined arrangement of pile and galvanometer, the name of thermo multiplier is given. Two metal bars of different heat conducting power having their ends soldered together, and the combined bar then usually bent into a more or less horseshoe or magnet form for the purpose of bringing their free ends within a conveniently short dis tance, designated a thermoelectric pair, are much used in thermoelectric experi meats. But as the electric current de veloped in a single pair is very weak, a considerable number are usually com bined to form a thermoelectric pile or battery. Bismuth and antimony are the metals usually employed, the difference in electromotive forces being greater be tween them than between any other two metals conveniently obtainable.