The material consists of 'The existence of more than one ionized layer in the upper atmosphere'. A published version of Appleton's paper presented at U.R.S.I. [Union Radio-Scientifique Internationale] General Assembly, October 1927, announcing his discovery of the F layer; 'Some Observations on International Research on Atmospherics'. A typescript of Appleton's paper presented at Copenhagen meeting, 1931; and U.R.S.I Program of meeting, Washington D.C., 1938.