The automotive engineers have had a most important part in the conduct of the Government aircraft programme. It is well known that the development of the Liberty Engine is properly credited to engineers who are members of the Society of Automative Engineers and whose work has been greatly facilitated by the present and past activities of the society. Due credit must of course be given to the Allied Governments for data furnished to our engineers who designed the Liberty Engine, but it should not be forgotten that this engine is strictly an American product, having been designed for rapid production, standardisation and interchangeability of parts, factors not realised to the same extent in other designs. The benefit which this will have in increasing the effectiveness of our fighting contingents at the front can scarcely be over-estimated. The aviation engine is of course a high-strung piece of apparatus, one that must develop great power with minimum weight. The engine operates under full load and at high temperature practically all the time, so that its depreciation is relatively rapid.

I have been asked by your Council to address you to-night on one or more of the many points where aviation and meteorology come into contact. I cannot lay claim to much knowledge of aviation and my excuse must be the rapid increase of such knowledge during the last few years and the fact that under our present conditions much of it must be of a confidential nature; but the importance of meteorological conditions for the practical business of flying is so obvious and so great that I think it may be of use and interest to point out the effect that the more prominent meteorological phenomena have upon aviation.

The only experiments on the resistance to torsion of woods that I have been able to find are those of Benjamin Bevan, in the “ Philosophical Transactions ” of 1829, p. 127. As these may interest the members of the Aeronautical Society I give below a list of his results. I have, however, taken the liberty of substituting my own records for the average weights per cubic foot, as Bevan gives but few, and these to my mind are unsatisfactory, being the result of single trials, whereas mine are the mean of series of tests collected from all sources. I have then rearranged the list according to these weights in order to test Bevan's suggestion, that “the modulus of torsion bears a near relation to the weight of the wood.” Certainly the higher results are found amongst the heavier woods; there are, however, a few exceptions that render a blind confidence in this rule somewhat dangerous and it should be accepted as a rough guide only. I regard it more as a demonstration of the very general fact that, apart from freaks of structure, heavy woods are in all respects stronger than light woods.

The function of an aerofoil of circular arc camber is to impart motion in a circular path to a mass of air whose volume is determined by the product of span, chord, and mean sweep, the latter being a linear measure of the depth of the strata of air affected above and below the surface.