A method is described by which metallic wires can be subjected to easily measurable but very pronounced asymmetrical temperature gradients without straining the wire The electromotive forces developed by the application of symmetrical and asymmetrical gradients to annealed `thermopure' platinum wire and specially prepared cables of copper wire, at both high and low temperatures, have been measured at many points along considerable lengths of wire Precautions to minimize or eliminate spurious effects enabled measurements significant to 0 01 μv to be takenThe results provide no justification for the supposition that an asymmetrical temperature gradient thermoelectric effect exists, under the conditions of investigation, which cannot be explained in terms of inhomogeneity effects The nature of these effects is discussed and some evidence is provided which indicates that the variation in the Thomson thermoelectric potential with strain and impurity is significant