Since this paper is prepared at the request of the Council of the Royal Aeronautical Society–a body which represents in the main the scientific aspect of aviation–I have endeavoured in preparing it to remember that I must infuse into its composition something of worth to the technician as well as to the pilot. If I manage to convey to the former some of the problems which confront the latter and which are not quite the same as those with which he is himself faced, I may have rendered some small service in response to the honour which the Council of the Society has done me in asking me to undertake this duty.

Six years ago the present authors read a paper on “Aviation Spirit, Past, Present and Future.”

At that time the subject of special interest was the possibility of finding substitutes for petroleum spirit and a variety of alternative volatile combustibles was described.

Six years ago there happened one of the periodical scares regarding a possible world-famine in petroleum and naturally the chemist at that time was anxious, to find substitute fuels.

Air Photography and its serious application to map-making may be traced to the Great War. It was at this period that grave consideration had to be given to Air Photography as a method of producing maps.

In all the theatres of war, which included France, Palestine, Salonica, and Mesopotamia (or Iraq as this country is now known), extensive operations were carried out in Air Photography, and the photographs used for the amplification of existing maps, and in many cases to the compilation of new maps.