Since I was asked in September last to read this lecture conditions ha\c •so chang-ed that it has, been necessary totally to re-cast and re-write what I then proposed to say. A large amount of information as to the lactual achiexe- ments of airships has been published and also perhaps an even larger amount of speculation as to their future possibilities. What will, therefore, probably Tdc of interest to a technical society such as this is a general outline of tlie ships as they exist at the stage to which they have been developed during the war.

In order to make clear the various matters which inlluence the lift and behaviour of an airship, I have introduced a small amount of aerostatics which will appear obvious and unnecessary to many, but may help others to the understanding of the more interesting points treated later.

The extent of the detail which I have been allowed to include in the lecture, although such matters have not been published before, leaves the Society with .a very deep debt of gratitude to the Admiralty.