How lorenz might have viewed the computation of the angular functions occurring in his theory.
Philip J. Wyatt Science Spectrum, Inc., Santa Barbara, California 93105. Received 15 July 1974. The recent letter by Evans discussing approaches to the generation of the angular functions appearing in the Lorenz series caused me to recheck my own codes and also to reread Lorenz on this subject. These angular func­ tions, π1 and τ1, have only to be generated once (and then stored) during any calculations involved with the scattering of light from spherically symmetric objects, and thus Ev­ ans's concern about the economies of conserving time in their calculation may be somewhat academic. The accura­ cy problem, on the other hand, I had never noted before; and perhaps this is due to the particular form that I have found most useful. Referring to Lorenz's paper, one can see why the accu­ rate generation of the π1's and τ1's is a relatively simple matter—remembering that the Legendre polynomial recur­ rence formulas can be used without fear of any computa­ tional loss of accuracy, even at the specific angles of con­ cern to Evans. Specifically, Lorenz only made reference to the two functions,