There exists a large number of varying methods of solution in radiative transfer theory. House and Avery have recendy published an exposition of the Monte-Carlo technique and the very nature of this solution makes it readily amenable, in theory, to the study of any transfer problem. Grant and Hunt have developed a method involving the invariant Sn matrix transformation and this also appears quite general in its application. Further, the Riccati transformation technique, developed by Rybicki and Hummer, has already been used in solving several different transfer problems. However, these methods have certain disadvantages. The equations are of first order and thus stability difficulties arise. Also, the finer details of the method rely, to a large extent, on the particular problem under consideration, and experience with such a method is required for the efficient computation of solutions.