The invitation which you, Mr. President, were good enough to issue to me some months ago really amounted, I am afraid, to a request that I should come here to prophesy. My reply was that it was not possible, or at any rate, I did not propose to undertake it. All one could do was to follow the recent development of materials for aircraft purposes as well as possible in order to see the general tendencies of that development and those which seemed likely to be followed in the near future. But even with regard to that limited degree of forecasting, I must warn you that it is undertaken with every possible reservation, and for this reason, that while one may be able to foresee to a certain extent a number of feasible lines of advance, there have always been in the past history of all branches of technology unexpected developments which no man could foresee, and which I personally make no pretence of being able to visualise. Therefore I would ask you to look with more confidence on what I have to say about what has been and what is, than about what may be.

This paper aims at giving the most important results of modern German research upon the motion of incompressible fluids. Before dealing with the latest developments, I have thought it advisable to give a short account of the older researches upon which the present work is based. It is hoped that this résumé will give a fairly complete survey of the methods that have led to the present insight into the hydrodynamical mechanism.

The scope of the paper is not so wide as the title may suggest. The primary object is to put forward a graphical method of determining the shape of the cross-section of the airship, and the loads in the envelope and rigging wires, in the plane of the cross-section, for different loading conditions.

Various secondary matters, such as a brief review of other methods of dealing with the subject, and the effect of different schemes of rigging on “ breathing,” are included in the paper as points of interest.