Abstract
The application of Williams' method to underground star production by μ-mesons is discussed. It is shown that the virtual photon spectrum derived by Williams is not applicable to this process and the appropriate virtual photon spectrum is deduced. The results on star production are then re-examined and it is shown that photo-nuclear effects are unable to explain the observed cross sections. The relationship of this result to the observations on the anomalous scattering of μ-mesons is also discussed.