PELTIER, Jean Charles Athanase, was originally a watchmaker, but retired from business about the age of thirty and devoted himself to experimental and observational science. He was born at Ham (Somme) in February 1785; his death took place at Paris in October 1845....
His great experimental discovery was the heating or cooling of the junctions in a heterogeneous circuit of metals according to the direction in which an electric current is made to pass round the circuit (1834). This reversible effect is proportional directly to the strength of the current, not to its square, as is the irreversible generation of heat due to resistance in all parts of the circuit. It is found that, if a current pass from an external source through a circuit of two metals, it cools one junction and heats the other. It cools the junction if it be in the same direction as the thermo-electric current which would be caused by directly heating that junction. In other words, the passage of a current from an external source produces in the junctions of the circuit a distribution of temperature which leads to the weakening of the current by the superposition of a thermo-electric current running in the opposite direction. The true importance of this so-called “Peltier effect” in the explanation of thermoelectric currents was first clearly pointed out by Joule; and Sir W. Thomson (see vol. viii. p. 97) further extended the subject by showing, both theoretically and experimentally, that there is something closely analogous to the Peltier effect when the heterogeneity is due, not to difference of quality of matter, but to difference of temperature in contiguous portions of the same material. Shortly after Peltier’s discovery was published, Lenz effected by means of it the freezing of small quantities of water by the cold developed in a bismuth-antimony junction when a voltaic current was passed through the metals in the order named.
Peltier’s other papers, which are numerous, are devoted in great part to atmospheric electricity, waterspouts, cyanometry and polarization of sky-light, the temperature of water in the spheroidal state, and the boiling-point at great elevations. There are also a few devoted to curious points of natural history. But his name will always be associated with the thermal effects at junctions in a voltaic circuit, a discovery of importance quite comparable with those of Seebeck and Cumming.
