Dr. Stratford (p. 133, February 1965 Journal) is to be supported in his endeavour to apply boundary layer theory to the prediction of optimum loading requirements in flow through blades in cascade. Inevitably some simplification of the general flow system in a blade passage is necessary if undue complexity is to be avoided. In the simplified flow model, however, care must be taken to avoid over-simplification, and the limitations imposed by legitimate approximations must be appreciated.