These experiments were suggested by observations on the different lengths of time required, under different circumstances, for telegraph cables to assume the temperature of the water in which they were submerged. The method employed was that known as “Angström's,” which has already been described by Prof. Tait (Proc. K. S. E. 1872–73 p. 55–61); the manner of the application of the method being, however, somewhat modified in these experiments, we will give a short description of it.