N There is no current passing, thus no chemical reaction occurring during the measurement of the potential. How- ever, there is heat flowing from the hotter to the colder electrode and this is what keeps the system from being in thermodynamic equilibrium. Secondly, when one writes the "half-reaction", one tends to forget that the electrode potential for it is understood to the with respect to the standard hydrogen electrode. Only if the potential of the standard hydrogen electrode did not change with temperature might one he able to equate the electrode potential differ- ence to the desired "thermo galvanic potential". If one wishes to apply theory to the thermo galvanic cell, one must use the thermodynamics of irreversible processes, which we do not attempt because we are not expert in this area. (See Delahay, Paul, and Tobias, Charles W., Editors, "Advances in Electro chemistry and Electrochemical Engineering", Val. 3, Interscience, 1963, pp. 31-121).