Second letter to Frederick Gerard Friedlander, regarding two papers 'The diffraction of sound pulses III. Note on an integral occurring in the theory of diffraction by a semi-infinite screen' and 'The diffraction of sound pulses IV. On a paradox in the theory of reflexion' by Frederick Gerard Friedlander Sectional Committee: Physics Encloses author's copy of the paper for confidential use only. Requests acknowledgement of receipt. [Published in the 'Proceedings of the Royal Society of London'] No received date. [1942]