The material consists of drafts, notes, data and correspondence. Much of it was originally crammed into a folder inscribed 'Abnormal E Paper’, with a manuscript note added later by Appleton ‘Mr. Lyon to see. These are approx. 20 year-old notes’ The bulk of the material refers to work in the 1930s, including Appleton's collaborative papers with R. Naismith and L. J. Ingram (Coll-37/C.36-C.45). The later folders (Coll-37/C.46-C.50) refer to his work in the 1950s with A. J. Lyon and A. G. Pritchard and to his last article on the subject, which was unfinished at his death (Coll-37/C. 50). Additional data, notes, etc. dealing with various research projects on the 1E Layer1 but not included with this specific material, can be found in 'General Ionospheric Topics' in Section F. Correspondence on E-layer research appears at Coll-37/C.51-C.55. Notes and drafts for Appleton's last paper on the E-layer, unfinished at his death, are at Coll-37/D.62-D.64.