Ever and again in the history of aëronautical development during the last century there occurred a movement in favour of the hélicoptère or vertical screw machine, and now when flying machines have advanced to a practical stage the question again appears. Many will have doubtless followed with interest the series of letters which has been appearing in “Engineering” since early in the year, in the course of which several engineers of repute have advocated the hélicoptère in no uncertain manner.

The heaviest flying birds known scarcely reach one quarter of the weight of an average man, and it can be said that one of the most probable causes of the absence in Nature of heavier varieties is the fact that although such birds could fly easily enough, once on tlie wing, they would be unable to leave the ground, owing to’ the enormity of the power the first lift Avould require. The larger and heavier the bird, the less, in relation to its weight, is the power developed in flight, but, on the other hand, the greater is the eft'ort. needed for a. lift from the ground. I do not wish to enlarge upon this question, which has been treated by various authors, and only refer to it because it embodies a principle which we must bear in mind when considering the means of starting flight, namely, that the difference between the power required respectively for the flight and for the start becomes greater as the apparatus increases in weight.

I write promptly on this very important subject, as time with me is on the wing. I have passed fourteen years beyond the three score and ten of life allotted to man. For many years I have at times brought up the subject of flying, and if I say a few words concerning myself I may, perhaps, be exempt for incurring a charge of egotism.

My training has been that of a marine engineer. I was present at the early trials of “Archimides”—the only screw steamer then afloat. I was but a small boy then, but ever since have taken a keen interest in screw propulsion. It may, therefore, be asked why I did not apply a screw propeller to my design of a flying machine in 1866, but no motive power except steam was then known, and I could not imagine the practicability of carrying a supply of water and fuel up in the air and therefore had to consider the possibility of the strength of a man being sufficient to propel the machine. For this purpose the adaptation of a screw propeller was not feasible, as the man, having other matters requiring his attention, could not be solely occupied in turning a winch-handle. I, therefore, proposed to adapt a pair of oars to be worked by treadles.

The fact that a considerable amount of knowledge can lie gained by experiments with weighted model gliders does not at present appear to be sufficiently appreciated ; only with model gliders, for convenience sake, a less weight is used per square foot of carrying aëroplane surface. A ¼ lb. per square foot area is a convenient demonstrating weight, giving a Speed of about 8 m.p.h., with a drop of about one in six ; with man-carrying machines the usual weight varies between ½ and 1½ lbs.

If a single aëroplane be released in the air it will simply fall anyhow to the ground, but on fixing a steering plane fore or aft, let us say in front as in Fig. 1, there will be a tendency for it to glide, but sooner or later one side will dip downwards, owing to the two planes not being in the same straight line or being improperly balanced.

This paper is intended in the first place to ascertain some definite and tangible ideas as to dimensions of the vital parts of machines “ heavier than air” designed for aërial navigation. The vital parts are, of course, the engine and propeller.

In the second place it is proposed to discuss the aëroplane and its functions in an airship.

In all engineering problems the first requisite towards a solution is to reduce things to numerical values. An inventor may imagine a design for a machine, but he cannot put it into practice without calculating out the necessary dimensions, and such, calculations, when undertaken, often either confirm or condemn the design.

Much of the experimenting at present going on is evidently entered upon, and carried on, without any calculations at all, the only results being a waste of time and money.

I have been requested to write a short paper on the flight of the flying fish and the lessons which this act may afford in the steering and management of an aëroplane in flight.

As yet we are still striving to attain success in aërial flight by means of a machine heavier than air. Many remarkable flights have been recorded quite recently, and the art of aviation has advanced during the past few months by leaps and bounds. It now appears clear that under favourable conditions, still air, or with but a moderate wind and an open course, an aëroplane may be constructed, or soon will be, which can remain in the air as long as the motive power which drives the propeller is maintained, or practically as long as the supply of petrol capable of being carried holds out.

As Mr. Phillips is unable, through stress of work, to write an account of his machine, I have prepared a few notes about it, and he has kindly revised them.

The machine is of a quite unusual type, and the study of its design and general system of working will be found of great interest.

In order to understand the principles upon which it is based, it is desirable to first examine briefly the early experiments carried out by Mr. Phillips and the results obtained from them.