The material consists of 12 files containing correspondence and notes from William Roy Piggott to Edward Appleton. Piggott had been a student at King's College, London, and later moved to Cambridge with Appleton. He subsequently worked at the Radio Research Station, Slough, and, like R. Naismith (q.v.) became one of Appleton's chief collaborators, being seconded at the latter's request to D.S.I. R. [Department of Scientific and Industrial Research] headquarters on the outbreak of World War II. He was thus particularly close to Appleton during the war years and their correspondence takes the form of notes on scraps of paper, headed (by Piggott) simply 'Secretary' and not always dated. After the war Piggott returned to work at Slough, whence the later correspondence is addressed. The material, which includes data, graphs, reports, etc., is presented as a chronological sequence as far as this is ascertainable. It deals with a variety of research topics and should be consulted in conjunction with similar material in Coll-37/C.