THE theory of the turbulent transfer of heat in the atmosphere, based on the concept of the mixing length, was introduced by G. I. Taylor1 in 1915. Modified by D. Brunt2 to be applicable to a compressible atmosphere, the theory requires that the flow of heat is in the direction of the gradient of potential temperature, and thus is normally downward. From these treatments a close analogy can be drawn between molecular transfer and the larger scale of eddy transfer.