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.