It is the purpose of this paper to point out some apparent discrepancies between the observations of geodesists on isostasy and the inferences which some radiologists have drawn as to the great age of certain specimens of minerals. It seems well to begin by reviewing the results of isostatic investigations, in order to estimate the degree of confidence to which they are entitled; and recent advances in radiology demand similar attention.
Correlation of these widely distinct researches is possible because it happens that the emission of heat by a globe whose excess temperature is due solely to radioactivity obeys Fourier’s law exactly as does that emitted by a hot but radioinactive globe. It is thus easy to plot the distribution of temperature in a globe which at the consistentior status had a high temperature due in part to radioactivity and in part to compression, the diagram being strictly analogous . . .