The liquid-cooled engine is generally associated with high speed aircraft, and as I have had some experience in connection with the development of racing engines, when I received the honour of an invitation to read a paper for the Royal Aeronautical Society, I chose this title because it gave me a chance to further the cause of the liquid-cooled engine and to interest you in possible developments of engines suitable for high speed and other types of aircraft.

In attempting to forecast possible developments, I am taking a grave risk, as anything connected with aeronautical engineering is doubtful owing to the rapid changes which take place in a short time, and I can only indicate where I think improvements can take place, based on present progress, and can only hope that my remarks will invite criticism and discussion.

During the paper the “ hardy annual ” ‘ frontal area ’ will be raised; a slide will be shown of a liquid-cooled engine superimposed over an air-cooled radialof the same b.h.p.