The title chosen for this paper is a somewhat ambitious one, as prophecies in any sphere of engineering are always dangerous. Especially is this so in such a young and progressive branch as aeronautics, where changes are rapid, and developments considered modern and up-to-date to-day, may, in a few years, be thrown aside as being obsolete. However, when I received the honour of an invitation to read a paper before the Royal Aeronautical Society, I chose this title with “malice aforethought,” if only with the idea of inviting criticism and discussion.

I. In recent years a systematic research has been made into the methods available for determining the stresses in three dimensional braced frameworks, and in particular into frameworks of the type represented by the hull of a rigid airship. Much of the research has been of a generalised character, intended to act as a useful guide to the designer rather than to deal with any particular problem of loading with which he may be confronted; attention has therefore been largely (though not entirely) concentrated on the stresses in a fully braced parallel tubular structure such as is shown in Fig. I, in which the wire bracing or “ tension ” members are initially strained so as to be capable of carrying compression,— the slackening off of wires, which will of course take place before failure, being considered subsequently by the “ device of the separate panel.”