When first I was approached to lecture to the Society it was suggested that I might speak to you on “Modern Aircraft Materials.” I did not choose this subject, firstly because I felt it was much too comprehensive to be susceptible of compression within the period of any ordinary paper; and secondly, because the relevant data (in so far as it is known) is enshrined in the official specifications, in the catalogues published by the metal manufacturers, and in a large number of papers presented to this and other learned Societies.