This series contains all of Edward Appleton’s correspondence, other than that which he kept in specific folders as part of a research topic, ordered in an alphabetical sequence. Because of the disordered state in which the material was received, it does not always exactly meet this criterion. Several of the documents (letters, data, research reports, etc.) included here could have been moved to Section C, but it was felt that as so few of Appleton's files had survived they should be preserved as distinct entities. Nevertheless, the long exchanges of letters and data with W.J.G. Beynon (Coll-37/E.9 – E.16), R. Naismith (Coll-37/E.71 - E.82) W.R. Piggott (Coll-37/E.87 - E.98), and B. van der Pol (Coll-37/E.117 - E.144), to name the most obvious examples, relate closely to the research topics of Coll-37/C and should be considered as supplementary material to them. The correspondence is dated and indexed, and a brief indication is given of material of particular scientific or personal interest. Extensive correspondence with an individual appears in one or more personal folders and shorter exchanges from multiple correspondents are grouped in folders. There is very little surviving personal or family correspondence, but see Coll-37/E.60, for Appleton's letters and cards to Ada Leach.