Lecture on 'X-ray study of crystal dynamics' at two Physical Society meetings, Imperial College, London, 16 January 1942 and Cavendish Laboratory, Cambridge, 21 January 1942. Includes agenda for Physical Society meetings, 1942; 4pp manuscript lecture notes and 2pp manuscript of slides; 3pp typescript remarks on the published lecture by LL Van Reijen, 1945. 1942-1945