'Wellenausbreitung in ionisierten Gasen unter dem Einfluss eines Magnetfelds'. The material consists of a manuscript narrative and calculations by Wilhelm Altar, variously paginated. Professor C.S. Gillmor described this document as 'very important for the history of the ionosphere' and gave its date as 'late 1925 - early 1926' in a private communication on 4 December 1978. The document was registered for copyright by Dr Altar, 1978. There are brief notes by Appleton on the title sheet and 2 pages of manuscript notes by him at the end.