Aeronautics is a youthful study—a mere Cinderella of the Sciences, distinguished from her sisters by her tender years, by her guileless and impetuous disregard of the pinch of the financial shoe, and by her beauty.

That it is Applied Physics is to me the most inspiring definition of engineering; and if this be true for engineering in general, as I think it is, especially true is it of aeronautics. To illustrate the close association of these new studies with the work of physicists, I shall select a few of the more striking results of recent research.

Aviation is now entering upon a new and intensely interesting phase—one which will call for every scientific resource at our command. The materials of -construction are changing : wood is giving place to metal. The engine proves ito have most unexpected possibilities ahead of it through the increase of intake pressure; whilst the very lifting structure itself promises to change, for some purposes at least, from linear motion to rotary.

At the present stage of the development of the different means of aerial flight, we find that there is a greater use of land aircraft than of seaplanes. The most important reason for this arises from the widespread opinion that a larger output of useful transportable weight may be obtained with aeroplanes than with seaplanes. Another reason is that commercial air lines are nearly always run on land, and consequently can better be operated by means of aeroplanes.

The introduction of a new material is a very slow process and engineers are extremely critical of the claims put forward in favour of any new materials. The development of aluminium and its alloys has been exceedingly slow and it has needed the extraordinary circumstances of the war and the brilliant work recorded in the eleventh report of the Alloys Research Committee of the Institute of Mechanical Engineers to establish finally the use of aluminium and its alloys. This paper deals with one of the latest metals to be introduced to engineers.

The foundation of the modern theory of sustentation is the recognition of a cyclic or circulation component in the fluid motion surrounding the aerofoil.

But the “ circulation ” is of a somewhat abstract character. To the non-mathematical, and more generally to those who like to be positively assured that they are dealing with physical realities, the truth of the “ circulation ” is not altogether easy to demonstrate; in fact, it must be admitted that the word is used in a special sense.

Thus, when we talk of circulation we naturally expect to be able to track a particle in its path till it returns to’ some starting point or datum; such, for instance, as the underground trains on the inner circle, or as in the circulation of the blood from the heart through arteries, capillaries and veins, etc., and its return to the heart.