The present decade will pass down into history notorious for many things good and bad. It will be styled a time of improvement in many ways. It will be remembered as covering the period of the world's greatest war, but it will also be remembered among all trades appertaining in any way to engineering as the age of progress in the manufacture and manipulation of steel tubing.

Independent altogether of the stimulus given to the use of tubing for structural work by the advent and advance of aeronautics, the uses to which tubing of steel and other metals is put has increased considerably during the past few years. Much, of course, has been due to the large output of cycles and motor-cycles, but in addition an immense quantity of tubing is used in the construction of motorcars, and in a thousand other productions which it is unnecessary to particularise in this paper.

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.

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.