An occasional duty of aircraft may fitly be mentioned here. It is sometimes desirable that a missionary should be deposited at a quiet spot behind the enemy lines, and when he wishes to communicate with those who sent him out it sometimes becomes necessary to supply him with a basket of pigeons. When communication is interrupted on the troubled surface of the earth, it can often be renewed in the air.
As the uses of aircraft multiplied, so did their designs, and where many various tasks were performed, in the beginning of the war, by a single type of machine, good in its day, there are now many types of machine, each with special fitness for its own purpose. How far these developments may yet go, no man can tell, and prophecy is idle; what is certain is that many operations of war and peace which have never yet been performed are within the reach of the aircraft that are now at our disposal. A beleaguered city could be victualled. A force of a thousand men, with rations and ammunition, could be landed, in a few hours, to operate in the rear of an invading army. But the world is tired of war, and the advances of the immediate future will rather be made in the direction of peaceful traffic and peaceful communication.
The history of the war in the air is the history of the rapid progress of an art and the great achievements of a service. In the nature of things the progress of the art must claim a share in the record. If the battle of Trafalgar had been fought only some ten short years after the first adventurer trusted himself to the sea on a crazy raft, the ships, rather than the men, would be the heroes of that battle, and Nelson himself would be overshadowed by the Victory. The men who fought the war in the air have overcome more than their enemies; they, and those who worked for them on the ground, have successfully grappled with problem after problem in the perfecting of the art of flight. A whole world of scientific devices, from the Pitot tube, which indicates the speed of the machine through the air, to the Dreyer automatic oxygen apparatus, which enables the pilot to breathe in the rarefied upper reaches of the atmosphere and to travel far above the summit of high mountain ranges, has become a part of daily usage. A machine is the embodiment of human thought, and if it sometimes seems to be almost alive, that is because it springs of live parents. The men of science, who worked for humanity, must have an honour only less than the honour paid to the men of action, who died for their country. These last, the pilots and observers who are dead and gone, would not ask to be exalted above other branches of the fighting services. Their pride was to serve the army on the land and the navy on the sea. The men who march often admire and extol the courage of the men who fly, and they are right; but the men who fly, unless they are very thoughtless, know that the heaviest burden of war, its squalor and its tediousness, is borne on the devoted shoulders of the infantryman. All other arms, even ships of war themselves, in many of their uses, are subservient to the infantry. Man must live, and walk, and sleep on the surface of the earth, and there, in the few feet of soil that have been fertilized by contact with the air, he must grow his food. These are the permanent conditions, and they give the infantry its supremacy in war. A country that is conquered must be controlled and administered; a city that surrenders must be occupied. Battles can be won in the air or on the sea, and the mark of victory is this, that the patient infantry, military and civil, can then advance, to organize peace. An immense sympathy for the sufferings of the infantry, an immense admiration for their dogged perseverance in their never-ending task, is felt by all those whose business it is to assist them from the air. It would be an ill service to the men of the air force, and a foolish ambition, to try to raise them in consideration above the heads of the men whose servants and helpers they are.
There is one glory of the sun, and another glory of the moon. The air service has its own advantages, its own trials, and its own marks of distinction. Life in the service was lived at high pressure, and was commonly short. Throughout the war our machines were continually at work over enemy territory, but the pilots of the beginning of the war were not crossing the lines at its close. A few were acting in administrative posts; some had returned, disabled, to civil life; the rest have passed, and their work has been carried on by generation after generation of their successors. The air service still flourishes; its health depends on a secret elixir of immortality, which enables a body to repair its severest losses. The name of this elixir is tradition, and the greatest of all the achievements of the air service is that in a very few years, under the hammer of war, it has fashioned and welded its tradition, and has made it sure. Critics who speak of what they have not felt and do not know have sometimes blamed the air service because, being young, it has not the decorum of age. The Latin poet said that it is decorous to die for one's country; in that decorum the service is perfectly instructed. But those who meet the members of a squadron in their hours of ease, among gramophones and pictorial works of art suggestive of luxury, forget that an actor in a tragedy, though he play his part nobly on the stage, is not commonly tragic in the green-room. If they desire intensity and gravity, let them follow the pilot out on to the aerodrome, and watch his face in its hood, when the chocks are pulled away, and he opens the throttle of the engine. No Greek sculpture is finer in its rendering of life and purpose. To see him at his best they would have to accompany him, through the storm of the anti-aircraft guns, into those fields of air where every moment brings some new trial of the quickness of his brain and the steadiness of his nerve. He is now in the workshop where tradition is made, to be handed down as an heirloom to the coming generations. It will not fail to reach them. The Royal Air Force is strong in the kind of virtue that propagates itself and attains to a life beyond a life. The tradition is safe.
CHAPTER I
THE CONQUEST OF THE AIR
We know next to nothing of man's greatest achievements. His written history is the history of yesterday, and leaves him very much the same being as it finds him, with the same habits, the same prejudices, and only slightly enhanced powers. The greatest and most significant advances were prehistoric. What invention, of which any record remains, can compare in importance with the invention of speech; and what day in the world's history is more worthy of celebration than that day, the birthday of thought and truth, when a sound, uttered by the breath, from being the expression of a feeling became the mark of a thing? The man who first embarked on the sea has been praised for the triple armour of his courage; but he must be content with praise; his biography will never be written. The North American Indians are reckoned a primitive people, but when first they come under the notice of history they bring with them one of the most perfect of human inventions—the birch-bark canoe. What centuries of dreams and struggles and rash adventures went to the inventing and perfecting of that frail boat? What forgotten names deserve honour for the invention of the paddle and the sail? The whole story is beyond recovery in the rapidly closing backward perspective of time. Man's eyes are set in his head so that he may go forward, and while he is healthy and alert he does not trouble to look behind him. If the beginnings of European civilization are rightly traced to certain tribes of amphibious dwellers on the coast of the Mediterranean, who reared the piles of their houses in the water, and so escaped the greater perils of the land, then some sort of rudimentary navigation was the first condition of human progress, and sea-power, which defies the devastators of continents, had earlier prophets than Admiral Mahan. But the memory of these thousands of years has passed like a watch in the night.
The conquest of the sea can never be recorded in history; even the conquest of the air, which was achieved within the lifetime of all but the very youngest of those who are now alive, admits of no sure or perfect record. The men who bore a part in it, and still survive, are preoccupied with the future, and are most of them impatient of their own past. Where knowledge begins, there begin also conflicting testimonies and competing claims. It is no part of the business of this history of the war in the air to compare these testimonies or to resolve these claims. To narrate how man learned to fly would demand a whole treatise, and the part of the history which ends in December 1903 is the most difficult and uncertain part of all. Yet the broad outlines of the process can be sketched and determined. It is a long story of legends and dreams, theories and fancies, all suddenly transformed into facts; a tale of the hopes of madmen suddenly recognized as reasonable ambitions. When in the light of the present we look back on the past our eyes are opened, and we see many things that were invisible to contemporaries. We are able, for the first time, to pay homage to the pioneers, who saw the promised kingdom, but did not enter it. No place has hitherto been found for their names in serious history. The Dictionary of National Biography, with its supplement, includes the lives of all the famous men of this nation who died before King George the Fifth was king. Yet it contains no mention of Sir George Cayley, the Father of British Aeronautics; nor of John Stringfellow, who, in 1848, constructed the first engine-driven aeroplane that ever flew through the air; nor of Francis Herbert Wenham, whose classic treatise on Aerial Locomotion, read at the first meeting of the Aeronautical Society, in 1866, expounds almost every principle on which modern aviation is founded; nor of James Glaisher, who, in 1862; made the highest recorded balloon ascent; nor of Percy Sinclair Pilcher, who lost his life in experimenting with one of his own gliders in 1899. These men attracted little enough notice in their own day, and were regarded as amiable eccentrics; but they all thought long and hard on aerial navigation, and step by step, at their own costs, they brought it nearer to accomplishment.
Now that the thing has been done, it seems strange that it was not done earlier. At no time was it possible for man to forget his disabilities; the birds were always above him, in easy possession. If he attributed their special powers wholly to the lightness of their structure and the strength of their muscles, the variety of flying creatures might have taught him better. The fact is that there is no unique design for flight; given the power and its right use, almost anything can fly. If the sea-gull can fly, so can the duck, with a much heavier body and a much less proportion of wing. The moth can fly; but so can the beetle. The flying-fish can fly, or rather, can leap into the air and glide for a distance of many yards. With the requisite engine-power a portmanteau or a tea-tray could support itself in the air. The muscular power of man, it is now generally accepted, is not sufficient to support his weight in level flight on still air, but if the principles of flight had been understood, there was no need to wait for the invention of the powerful internal-combustion engine; a steam-engine in a well-designed aeroplane might have performed very useful flights. It was knowledge that lingered. Newton, when he saw an apple fall in his garden at Woolsthorpe, 'began to think of gravity extending to the orb of the moon'. If he had been in the habit of skimming flat stones on calm water, he might have bent his mind to the problem of flight, and might even have anticipated some of the discoveries in aerodynamics which were reserved for the last century—in particular, the relations of speed and angle of incidence to the reactions of air resistance on a moving plane. The fact which is the basis of all aeroplane flight is that a perfectly horizontal plane, free to fall through the air, has its time of falling much retarded if it is in rapid horizontal motion. This is what makes gliding possible. Now let the plane which is being propelled in a horizontal direction be slightly tilted up, so that its front, or leading edge, is higher than its back, or trailing edge. The reaction of the air can then be resolved into two components, technically called 'lift' and 'drag'; lift, which tends to raise the plane, and drag, which retards it in its forward motion. When the angle of incidence of the plane is small, that is, when it is only slightly tilted from its direction of motion, the greater part of the air reaction is converted into lift. This is what makes flying possible. A moderate speed through the air will enable the plane to lift much more than its own weight.
This is not a technical treatise, but some further facts of signal importance in the theory and practice of flight are better explained at once, in so far as the beautiful exactitude of mathematical demonstration can be expressed in the crudities of popular speech. The lift produced by the reaction of the air acts on the whole plane, but not equally on all parts of it. At a flying angle, that is, when the angle of incidence of the plane is small, the upward force is greatest on those parts of the plane which are immediately behind the leading edge. The wings of any soaring bird are long and narrow, and thus are perfectly designed for their work. A square-winged bird would be a poor soarer; a bird the breadth of whose wings should be greater than their length could hardly fly at all. The wings of a flying machine are called planes, or aerofoils; the length of the wing is called the span of the plane; the breadth of the wing is called the chord of the plane. The proportion of the span to the chord, that is, the proportion of the length of the wing to its breadth, is called the 'aspect ratio' of the plane; and a plane, or wing, that is long and narrow is said to have a high aspect ratio. A higher aspect ratio than is found in any bird or any flying machine would theoretically improve its powers of flight, but the practicable span of the plane, or length of the wing, is limited by the need for rigidity and strength. The albatross, nevertheless, the king of soaring birds, has enormously long and narrow wings; and the planes of some flying machines have an aspect ratio almost as high as the slats of a Venetian blind.