Of all the treasures accumulated by the Society in the course of its long career, in some ways the most interesting is the oil painting depicting a river scene with a balloon overhead, which hangs in the Secretary's room. In spite of this I have never seen any account of it, and all trace of the means by which it came into the Society's possession seems now to be lost–unless by chance this note may catch the eve of someone still living who has knowledge of the facts. At first sight it seems to be merely one of the many fanciful pictures of a balloon ascent so common at the end of the XVIIIth century in the period immediately following the invention of the balloon, but some years ago I stumbled, more or less by accident, on certain facts that lift it out of the ruck. When I was, in 1924, collecting the material for my book, Aeronautical Prints and Draivinys, I came across an engraved portrait of Joseph Michel, the elder Montgolfier, joint inventor of the balloon.

Physical–chemical study of light fuels and of lubricants in Aeronautics. (M. Moutte, La Technique Aeronautique, Sept.–Oct., 1926, pp. 279-281 and 305-319) (8.51/5096 France)

Systematic tests of fuels in an engine on the test bench were commenced in 1917, in conjunction with a systematic determination of physical properties, and as far as possible of chemical composition. It was found that homogeneity, volatility and high latent heat of evaporisation were the most desirable qualities. In agreement with Ricardo, the aromatic compounds of hydrogen are found to be the least amenable to propagation of explosion, then the saturated cyclic compounds, and lastly the saturated acyclic compounds. In identifying fuels use is made of characteristic curves of distillation:—

Temperature—Volume Distilled, Density;—Volume Distilled.

Temperature—Density, Temperature—Solubility.

Temperature of distillation plotted against critical temperature of solubility in aniline gives highly characteristic differences, and is considered a fundamental method. Optical methods are also used for approximate quantitative determination. The formation of clouds of condensed drops affords another method of determination. The mechanical conditions were also examined:—Variation of inlet pressure, condensation, centrifugal separation.

In Mr. Fearn's article on this subject in the February number of the Journal, in which a solution is given in the form of a Fourier series, a reference is made to the unsatisfactory results of an attempt to use double differentiation of the displacement curve. It is generally recognised that such a process is fundamentally inaccurate, and analytical methods, either exact or approximate, are usually given in books dealing with mechanisms. For mechanisms of the piston-connecting rod type, in which the higher harmonics of the motion of the driven member diminish very rapidly, two harmonics in all generally give all the necessary accuracy, both for displacement and acceleration. Mr. Fearn's solution is of this type, though he includes a fourth harmonic (see e.g.,the expression for ρ at the top of page 138).

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.

Not to go too far back in years, and to relate a few facts within the lifetime of most of you present to-night, I may commence by saying that it was in 1909 that Admiral Lord Fisher instructed Admiral Bacon to proceed with the design and construction of a rigid airship, attention having been called to the success attending Count Zeppelin's efforts and to the fact that we could not realise the dangers to which we might be exposed until we possessed airships of our own.

Admiral Bacon got into touch with Messrs. Vickers' experts, and Naval Airship No. 1, nicknamed the “ Mayfly,” was built at Barrow. Messrs. Vickers deserve all credit for their pioneer work on airship design and construction in this country, and it was only very bad luck that prevented their building the bigger ships.