The fundamental concepts of the Thomson heat and the basic equations governing the heat flows associated with its generation are presented. From these considerations, two different approaches to the direct measurement of the Thomson coefficient are demonstrated. The methods include a nonequilibrium technique in which the measurements are based on the initial temperature changes associated with the application of a potential gradient to a metal specimen in a thermal gradient and a technique in which the equilibrium temperature difference associated with the reversal of current flow form the basis for the calculation of the Thomson coefficient. The latter case leads to a very simple equation relating the Thomson coefficient to the change in equilibrium temperature associated with reversal of current flow. A simple calorimeter was designed and utilized to test the validity of the analysis and to compare these results with the electric current variation technique which was reported previously. The Thomson coefficients for nickel were observed as −32 ±12% &mgr;V/deg (40.1°C); −40.0±5% &mgr;V/deg (20°C) and −58.0±2% &mgr;V/deg (10°C). Those for lead were observed as −0.36±11% (41.0°C) and −0.31±3% (20°C).