When one is honoured by the invitation to deliver the Wilbur Wright Memorial Lecture one's immediate concern is to find a subject worthy of the occasion, which (in view of the wide coverage of the field of aeronautics that already has been made in these Lectures) is no easy task, at least to those of us who have no specialised knowledge wherewith to take advantage of the many new technical developments that continue to emerge.

In choosing my subject and in the attempt to draw, within a reasonable margin of error, an overall picture of the human effort that has been devoted to the cause of Aviation, I realise that I have bitten off a very large mouthful, and that some apology is due for the degree to which I may fail properly to masticate it.

On 17th December 1903 the Wright brothers started something, when by the achievement of human flight they opened the road to the tremendous developments in aviation that have taken place in this last half century. This vast and rapid progress in the technology of design, manufacture and operation of the aeroplane is today accepted as a commonplace, and its continuance taken for granted.