In this lecture it is proposed to deal with the general aerostatical principles governing the flight of lighter-than-air craft, and also to describe briefly the various types of airships, with special reference to the rigid airship.

The future of lighter-than-air craft is undoubtedly dependent upon the development of the rigid airship, in which type of ship efficiency and performance increase at a greater rate than the gross lifting capacity.

To understand the working of a large airship it is essential to have a thorough grasp of the elementary aerostatic principles governing the flight of an ordinary free balloon, so it is proposed, first, to outline these principles and then to pass on to the non-rigid, semi-rigid and rigid types of airships, all of which are virtually balloons of varying type, rendered dirigible by the fitting of means of propulsion, and navigable by the introduction of controlling surfaces.

It has been suggested that strut fittings could be made neater, on a staggered aeroplane, if the spar web were given the same stagger. Then the principal axes of the section are not in the direction of either the loading or the supports. The result may be an increase of both bending and shear stress; not more than it is possible to provide for, but involving an increase of weight likely to be more than the gain in the fitting.

Major-General Sir Sefton Brancker said he knew Squadron-Leader Hill as one of our most daring, cool-headed and really scientific pilots. He had also realised that evening that he had a brilliant fund of imagination as well. His (Sir Sefton Brancker's) chief qualification for talking about getting off and landing was that he was once more notorious for making bad landings without hurting himself or anyone else than anyone in the Air Force. He was all for eliminating the human factor in control as time went on. He thought the devices which Major Hill had explained were absolutely on the right lines of progress. Pilots did not like the idea, but he was all for developing the stabilisers, height indicators, and all the gadgets that the Author had described. But there were limits to this policy. Some time ago there was an official objection from the French at Le Bourget that the British pilots were stunting.

When your Secretary, shortly before Easter, wrote to ask me to give the Wilbur Wright Lecture he made me give him a title before writing the lecture. I therefore had to think of one which would fit any lecture I might conceivably want to give, so that when I came back after Easter I should be able to pick out one of those subjects connected with aeronautics with which I have been specially concerned, and discuss the results arrived at. When, however, I came to sit down to write the lecture itself it struck me that it might be more interesting to a general audience if I followed the line which is perhaps most obviously indicated by my title, and directed my remarks towards tracing and comparing some of the principal lines of argument which have been used in aeronautical research, without going particularly deeply into the results.