Fourier’s theory of heat conduction is well known. In its original form Fourier’s theory of heat conduction, as presented by the French mathematician, is rather abstruse, but fortunately somewhat simpler treatments of it are available in English, and one of them has been used as a source for the fundamental equations given in this paper. Even in the simplified form in which the theory is presented by Ingersoll and Zobel 1 there is still some difficulty involved in using the equations. I am in‐debted to Dr. Myron Pawley, instructor of mathematics, Colorado School of Mines, for demonstrating the manipulation which makes the equations of Ingersoll and Zobel directly usable, and to C. E. Van Orstrand, of the United States Geological Survey, and Dr. L. H. Adams, of the Geophysical Laboratory, for helpful criticism of the final results. In general, the equations are thrown into a form in which they . . .