In 1916 (Proc. Phys. Soc., Vol. XXIX., p. 59) the author outlined a steady state null method for measuring the Thomson effect in short lengths of wire. The present Paper describes a convenient form of apparatus for carrying out measurements with rapidity and under good theoretical conditions. The short wire under test (S.W.G. 18) passes through electrical heaters which may quickly be brought to and maintained at steady temperatures differing by some 50°C. over the range 20°C. to 250°C. A short coil of the finest double silk-covered copper wire (S.W.G. 44) acts as the Thomson-Joule heat detector. Test experiments were performed with iron and constantan wires, yielding values of the Thomson effect at various temperatures over the range indicated. Many improvements in the method are described, chief among which is a greatly improved sensibility.
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H Redmayne Nettleton (1921) studied this question.