Light alloys now play a most important part in aircraft construction. It is probable that they will keep their present superiority over other materials which have been in use, because manufacturers are continually adapting light alloys to the need of the day.

Light alloys have, however, formidable rivals. There are many arguments for the use of wood, and we must recognise that in certain aspects (such as resistance to vibration and ease of working) the use of wood has definite advantages, particularly in the case of plywood.

The Presidential Address to the Engineering Section of the British Association provides each year an opportunity for a survey of some aspect of engineering science which happens to be of especial importance at the time it is given, and often one which the experience of the President of the hour may chance to render especially appropriate. My subject to-day is “The Future of Flying.” Of its importance at the present time there can assuredly be no doubt. Aviation is surveyed by the public with a tempered pride—Pride, it is true, in man's achievement, but Apprehension, it is equally true, as to the use which is being made of it.

The aspiration towards winged flight was expressed, I submit, with great wisdom when, more than two thousand years ago, the Psalmist avowed his longing for “wings like a dove!” How wise a discrimination is revealed by the poet's asking not merely for the power of flight but that his wings shall be “dove-like.” For the space of a generation mankind has possessed the power of flight—a marvellous scientific and technical triumph but, alas, incomplete. Brilliant as was the work of the brothers Wright, the crown of achievement will not be truly won until a grateful mankind sees that the wings gained are the wings of a dove and not those of a bird of prey.

After some general remarks upon the constant flight characteristics of birds belonging to any given species, the author describes his method of obtaining, approximately, a cinematographic reproduction of three geometrical projections of the wing-beat. Dealing with one particular case he determines the trajectory in space of a pigeon's wing tip during an entire beat, and, also, the speed and acceleration reached by it.

Investigations have been carried out in connection with the testing of a definite aeroplane type in order to ascertain the extent to which the safe take-off can be sufficiently ensured by prescribing certain practical requirements.

This led to inquiries into the question as to whether the qualities of the aeroplane in the take-off could be determined from individual tests, in such a way that it would be possible, from the results, to determine the take-off path when climbing in conformity with a definite previously established policy.

The present report consists of an analytical consideration of the safety in the take-off, which may be used as a practical guide for the predetermination of a safe take-off policy, and a means whereby the dimensions of an aerodrome, such as shall meet the rational requirements for a safe take-off (of a definite aeroplane type), can be determined.

The problem under discussion is one which concerns both aircraft and engine constructors to an equal degree. Yet although their interest in it is a common one, inevitably their viewpoints will be different. This is not to say, however, that their conclusions will clash, and I want to make it clear that in setting out my views, as those of an engine designer, I intend them to be complementary to those of Mr. Chaplin, with the hope that taken together, they will in so me measure help in leading towards a complete solution of the problem.

As a guest of the Royal Aeronautical Society, I wish first to express my sincere appreciation of the opportunity to join those others who have appeared before you in years past to present the Wilbur Wright Memorial Lectures. To those of us who are primarily concerned with the scientific aspects of aviation this continuing series of lectures, now nearly as old as the art of human flight itself, is the finest tribute that could be offered in honour of the accomplishments of the Wright brothers. It is on this account that I feel most sincerely the honour and privilege that has been granted me through your invitation to present the Twenty-seventh Wilbur Wright Memorial Lecture.

The title—“ Some Modern Methods of Research in the Problems of Flight ”— is, I confess, somewhat ambiguous. At the time it was selected, some months ago, several investigations then in progress gave promise of results sufficientlyinteresting to be included.

Reciprocal theorems are valuable devices in the attack on strength, stiffness and vibration problems in structures, often leading to elegant and simple solutions. Reciprocity is a fairly common property in various coefficients which arise in mathematical physics, as for example coefficients of mutual potential, capacity, induction, and so on. It is inevitably encountered both in theory and practice in almost any branch of physical science. So far as the stiffness of structures is concerned it seems that while Hooke is the mainspring of the theory of elasticity Rayleigh is the regulator of reciprocal relations in elastic systems.