This paper is primarily intended to stimulate discussion on a subject of increasing interest to aeronautical students and of rapidly growing interest to commercial aeronautics. It must not by any means, therefore, be looked upon as a complete analysis of the subject, but rather as an introduction to the most important questions arising in recent development.

In considering this question we must first define the particular requirements of the large rigid airship. The airship must be looked upon with regard to the aeroplane rather as the ocean liner is looked upon with regard to the express train and not in any sense as a rival of the aeroplane. They each have their own distinctive duty.

Any commercial system depends upon safety and reliability. The airship designer has, therefore, the problem of making a structure safe under any conditions of flight and having a minimum ratio of structural weight to useful weight per horse-power.