During the last fifty years a considerable amount of attention has been bestowed on the question of the variations of the thermal and electrical conductivities of metals with the temperature, hut the results obtained by different observers, especially of thermal conductivities, differed so widely from each other that the answer to the thermal part of the question long remained doubtful. In recent years, however, there has been an accumulation of evidence in favour of a slight decrease of thermal conductivity with increase of temperature from 0°C. to 100°C. in the case of most of the metals. The experiments of Lorenz, and more especially the careful work of Jager and Diesselhorst have contributed greatly to this result. In both these cases the experiments were limited to the range of temperature between 0°C. and 100°C., and it seemed advisable, in view of the importance of both questions in the electronic theories of conduction of heat and electricity in metals, to extend the range over which the theories could be tested, particularly in the direction of low temperatures, where the experiments of Dewar and Fleming had already furnished information as to the electrical conductivities. The present paper contains an account of the measurements of the thermal and electrical conductivities carried out for this purpose, and the results obtained. The first section deals with measurements of the thermal, the second with measurements of the electrical, conductivities of certain metals and alloys, and the third section compares the results with the electronic theories.
XI. Bakerian lecture.―The effect of temperature and pressure on the thermal conductivities of solids.—Part II. The effects of low temperatures on the thermal and electrical conductivities of certain approximately pure metals and alloys