Reference was made to a previous paper by the author (Proceedings, 1867–8, p. 309), in which an attempt was made to apply to this subject the Theory of Dissipation of Energy.

Some years ago, a bar of German silver was procured, at the expense of the British Association, for the purpose of ascertaining whether its thermal, like its electric, conductivity is little altered by change of temperature. With this, Forbes' experiments have been carried out carefully through very great ranges of temperatures.