No calorimetric observations are required, but the results are obtained in terms of the thermal capacity of unit volume c, and the measurements give the diffusivity klc, instead of the calorimetric conductivity k.
Angstrom's Method consists in observing the propagation of heat waves in a bar, and is probably the most accurate method for 4 4 thehi 's ' 'so ' d 60 measuring the diffusivity of a metal, since the conditions may be widely varied and the correction for external loss of heat can be made comparatively small.
On some occasions, owing to the sudden melting of a surface layer of ice and snow, a large quantity of cold water, percolating rapidly, gave for a short time values of the diffusivity as high as.
Excluding these exceptional cases, however, the variations of the diffusivity appeared to follow the variations of the seasons with considerable regularity in successive years.
For the particular soil in question it was found that the diffusivity varied enormously with the degree of moisture, falling as low as ooio C.G.S.