The material consists of drafts, data and correspondence. Most of the early material relates to the papers by Edward Appleton and K. Weekes published in various journals, 1938, 1939. The correspondence continues to 1949, some of it relating to the paper by Appleton and W.J.G. Beynon, ‘Lunar oscillations in the D-layer of the ionosphere', Nature, 164, 1949. Appleton's notes, drafts, and exchanges with his principal collaborator, K. Weekes, appear at Coll-37/C.182-C.186, correspondence with other colleagues follows at Coll-37/C.187-C.191.