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The Daily Telegraph
WAR BOOKS

AIRCRAFT IN WAR

[Topical Press.

A FARMAN ARMED SCOUTING BIPLANE,

showing gun mounted in position, Gnome motor, ailerons on upper plane, rudders at rear (see [Chapter VII].).

AIRCRAFT in WAR

By
ERIC STUART BRUCE, M.A. Oxon.
Fellow of the Royal Meteorological Society; late Honorary Secretary
and Member of Council Aëronautical Society of Great Britain;
Vice-President of the Aërial League of the British Empire;
Membre d’Honneur of the Aëro Club of France

Illustrated

HODDER AND STOUGHTON
LONDON NEW YORK TORONTO
MCMXIV

TO MY WIFE,

who during the eight years of my Honorary Secretaryship of the Aëronautical Society of Great Britain incessantly and most materially aided me in my efforts to secure the united interest of the British nation in the mastery of the air, I dedicate this little volume.

CONTENTS

INTRODUCTION

When years ago we read in Tennyson’s “Locksley Hall” the following lines:—

Heard the heavens fill with shouting, and there rained a ghastly dew

From the nations’ airy navies grappling in the central blue—

we little dreamt that not very far from the beginning of the twentieth century the fancy of the poet would become the fact of reality; that in the great European war in which the nation is so strenuously engaged, “the wonder that would be” would come to pass.

Though happily, at present, in these isles the din of war is unheard, yet a semi-darkened London and bright searchlights playing on the skies tell the tale of prudent foresight against the advent of the enemy’s airfleet. From the battlefields there daily come the reports of actual battles in the air, sometimes betwixt aëroplane and aëroplane, sometimes between the lighter and heavier than air craft. Often such encounters are death-grip duels. Such conflicts of the air are the direct consequence of the great and important use of both airship and aëroplane as aërial scouts. These are the eyes of encountering armies. To destroy as far as possible this penetrating vision of the enemy and restore to him the fog of war is the untiring aim of either side.

During those first anxious days of the present war the public anxiously awaited news of the doings of the Royal Flying Corps, as well as those of the aviators of our Allies. Expectation was satisfied in the reading of Sir John French’s report to Lord Kitchener, dated September 7th, 1914. Speaking of the use of the aëroplane in the war he says:—

I wish particularly to bring to your Lordship’s notice the admirable work done by the Royal Flying Corps under Sir David Henderson. Their skill, energy, and perseverance have been beyond all praise. They have furnished me with the most complete and accurate information, which has been of inestimable value in the conduct of the operations. Fired at constantly both by friend and foe, and not hesitating to fly in every kind of weather, they have remained undaunted throughout.

Further, by actually fighting in the air, they have succeeded in destroying five of the enemy’s machines.

For those brave heroes of the air our hearts beat with fervid admiration. In accomplishing their all-important tasks they have not only to fear disaster from shot and shell of the enemy, but from the mistaken fire of their comrades and the very forces of nature. These latter, owing to the imperfections of the flying machines, do not entirely spare them; the Royal Flying Corps, in order to become competent to perform the work it is now doing for King and country, has had in manœuvres at home to pay a high price in the sacrifice of human life.

It may, indeed, be reasonably thought that the knowledge of the vast utility of aircraft in the present conflict will dispel the last remnant of prejudice in this country against the development of aërial navigation, and the grudging of a liberal national expenditure on the service of the air. It was, perhaps, this ignoring of practical utility, so vigorously combated by the pioneers in this country, that caused Great Britain to be the last of the Great Powers to seriously take up aircraft for military and naval use. Our delay had been a wonder to many, since theoretically in the past this nation had been to the fore. Nearly half a century ago it led the way of the air by being the first country in the world to found a society for the encouragement of aërial navigation—the Aëronautical Society of Great Britain. It is no exaggeration to say that many of the great principles of human flight were formulated and discussed at the earlier meetings of that society. The late Mr. Wilbur Wright, when he came to this country to receive the gold medal of the society, in his speech testified to the substantial help he had received from the study of the transactions of the oldest aëronautical society in the world. As the pioneer in laying the foundations of aërial science, this country is not without honour amongst the nations.

CHAPTER I
THE EARLIER AËRIAL SCOUTS

Patriotism has been the most powerful factor in developing aërial navigation. Montgolfier experimented with his paper balloons filled with heated air in the desire that his invention might be of use to France in her wars, and throughout the history of both balloons and flying machines we find that it has been the desire to employ them as instruments of war that has most fostered their progress.

Very soon after Charles invented the gas balloon the latter was pressed into military service for the very same purpose of reconnaissance for which airships and aëroplanes are now being used. At the time of the French revolutionary war an aëronautical school was founded at Meudon under the control of Guyton de Morveau, Coutelle, and Conté, and a company was formed called Aërostiers.

Captive balloons were used by the armies of the Sambre and Meuse, of the Rhine and Moselle. Just before the battle of Fleurus, 1794, two ascents were made, and the victory of the French was attributed to observations made by Coutelle. At that time several ascents were made from Liége with a spherical balloon and one of cylindrical shape. This latter appears to have anticipated the well-known German kite-balloon.

There is a tradition that in those early days of the balloon the French were possessed of a varnish which satisfactorily held the hydrogen gas, but that the secret was lost—a grave loss indeed, if the tradition has truth in it. The secret was never refound. A really gas-proof varnish is unknown.

In the course of the American Civil War of 1861 captive balloons were again employed with important results.

During the Franco-Prussian War of 1870 three captive balloons were installed in Paris, the “Nadar” on the Place St. Pierre; the “Neptune,” manned by Wilfred de Fonvielle, at the gasworks at Vaugirard; and the “Celeste” on the Boulevard des Italiens.

Thus long before the advent of airships and flying machines the use of altitude for military reconnaissance was realised. A great disadvantage of the captive balloon was its stationary nature. It was not prudent to ascend in it very close to the enemy, as there was not the same chance of escape as when the aërial observer is in mobile aircraft.

Though rifle fire has over and over again failed to bring down a captive balloon owing to the upward pressure of the hydrogen gas, still, artillery fire has been known to have very destructive effect.

Undoubtedly, the best use that has been made of the captive balloon was in the Boer War. The British observation balloon equipment, which under the unceasing labours of Colonel Templer had reached a state of considerable perfection, then proved to be highly efficient. But in the light of modern aëronautical progress its doings were merely the foreshadowings of the achievements the aviators in the present war are daily carrying out.

Perhaps the most important feature of the balloons in the South African War was the material of which they were made—gold-beaters’ skin. We are all more or less familiar with this substance, for we use it as a plaster when we cut our fingers. We should scarcely think that so apparently fragile a substance was strong enough to form the envelope of a balloon. It is, however, an admirable substance for the purpose on account of its lightness and capacity of holding the gas, and the desideratum of strength can be obtained by combining layer and layer of the substance to any desired thickness. By the use of gold-beaters’ skin it became possible to have much smaller balloons for a given lifting power than when varnished cambric or silk was employed. If made of the latter materials a captive observation balloon had to be at least 18,000 cubic feet to be of any service. Gold-beaters’ skin reduced the volume to 10,000 cubic feet, or even less.

The only disadvantage of gold-beaters’ skin for the envelope of balloons and airships appears to be its very great expense. This, in the case of a large airship, is formidable. It should be mentioned, however, that it has sometimes been used for the separate gas compartments which, as will be seen, are a feature of the Zeppelin airship.

As regards the actual achievements of the balloon in South Africa, one section did excellent work at Ladysmith. In the words of Colonel Templer, “it not only located all the Boer guns and their positions, but it also withdrew all the Boer fire on to the balloon. Several balloons were absolutely destroyed by shell fire.”

One of the balloons was burst at a height of 1,600 feet, and came down with a very quick run, but the staff officer in the car was unhurt. At Ladysmith, by means of the balloon, the British artillery fire was made decisive and accurate.

With General Buller at Colenso, and up the Tugela River, Captain Philips’ balloon section was very useful. Splendid work was done at Spion Kop. There the whole position was located and made out to be impregnable. It has been said that the British Army was then saved from falling into a death trap by the aërial reconnaissance. Captain Jones’ section went up with Lord Methuen on Modder River. His observations continued every day. It was considered there was not a single day that they were not of the utmost importance.

Again, Lord Kitchener and Lord Roberts used balloons. From the information they obtained from them they were enabled to march on to Paardeburg. At the latter place itself they were able to locate the whole position. Another section went to Kimberley and on to Mafeking. A very important observation was made at Fourteen Streams. There a balloon was used continuously for thirteen days without the gas being replenished. By its means the Boers were prevented from relieving Fourteen Streams.

It has been pointed out by Colonel Templer that one of the great difficulties connected with the use of the comparatively small balloons in the South African War was the heights the armies went over.

On the march to Pretoria there were hills 6,000 feet above the sea, and to make an observation from these hills it was necessary to go up 1,500 or 2,000 feet, so that the barometrical height was hard work on the buoyancy of the balloon, because the barometrical height then became 8,000 feet—the 6,000 feet altitude above the sea-level, and the 2,000 feet it was necessary to go over the hills—that was about all our balloons would do.

That was a disadvantage of the captive balloons which would not have been felt if the observers had been on aëroplanes!

Certainly, the excellent gas retaining power of gold-beaters’ skin was well put to the test in the South African War. The thirteen days’ work with one charge of gas mentioned above was a fair trial for a balloon of such comparatively small size; but Captain H. B. Jones gave a still more striking experience of the value of gold-beaters’ skin as a gas-holder. Speaking of the Bristol war balloon of 11,500 cubic feet capacity, he says:—

It was used at the engagements at Vet River and Land River, and arrived at Kroonstad on May 12th. The balloon was kept in a sheltered place near the river till we marched again, on May 22nd, and was not emptied till after we had crossed into the Transvaal at Vereeniging on May 27th. To keep a balloon going for thirteen days at one station is a good test; but in our case the Bristol was filled for twenty-two days, and did a march of 165 miles with the division.

The system of filling the balloons from steel cylinders in which the hydrogen gas had been compressed, so well exemplified in the Boer War, was a great improvement on the older methods of manufacturing the gas on the spot. Speed in filling balloons is a desideratum for their use in war. By the cylinder method, owing to the great pressure under which the gas escapes from the cylinder, the inflation of the observation balloons became a question of minutes instead of hours. The necessity of speed applies to the inflation of airships also.

Although the present volume is designed rather to speak of the aëronautical appliances of the present than those of the past, the above-mentioned facts concerning aërial reconnaissance in the Boer War have been included, as the value of the air scouts at the time was hardly known and appreciated by the general public, whose mind in those days was not constantly being directed to aërial matters as it is at the present time. The knowledge of what just a few well-contrived and well-utilised balloons could then do in the way of aërial scouting must lead to the thought how the Boer War might have been shortened had we then possessed the squadrons of fast-flying aëroplanes that are taking part in the present war. To know, indeed, what a very few aërial observers could do may enhance our estimation of the possibilities of the squadrons of the flying machines of the British and allied armies in the present war as they dart in search of information over the lines of the enemy.

In the course of some articles on the subject of the new arm of war, which contain many apt statements, Mr. F. W. Lanchester gives the opinion that the number of aërial machines engaged in the war is a negligible quantity. We might, indeed, well say the more the better, provided they are on the Allies’ side; but no aëronaut or aviator will allow the number is negligible. The writer compares the supposed number of aëroplanes the Germans possess with the cost equivalent of scouting cavalry. The comparison is not a happy one, on account of the tremendous advantage of altitude and, consequently, long range of vision possessed by the aërial scout. We have seen that in the Boer War one observer at Spion Kop from his height and super-sight saved the situation, and rescued our army from possible crushing disaster.

What might not even one shrewd British observer in a swift-moving modern aërial craft accomplish at a critical moment in the present conflict?

CHAPTER II
THE DEVELOPMENT OF THE AIRSHIP

Before free balloons were successfully motor driven and steered, stern necessity had pressed them into the service of war. During the siege of Paris, in 1870, when the Parisians were cut off from all means of escape, there were only a few balloons in Paris; but the successful escape of some aëronauts in them was considered encouraging enough to establish an aërial highway involving a more wholesale manufacture of balloons than had been accomplished before. The disused railway stations were converted into balloon factories and training schools for aëronauts. In four months sixty-six balloons left Paris, fifty-four being adapted to the administration of post and telegraph; 160 persons were carried over the Prussian lines; three million letters reached their destination; 360 pigeons were taken up, of which only fifty-seven came back, but these brought 100,000 messages, by means of microphotographical despatches. In these a film 38 by 50 mm. contained 2,500 messages. The pigeons usually carried eighteen films, with 40,000 messages.

At this time the French Government attempted to produce a navigable balloon, and employed Dupuy de Lôme on the task of designing and building it. This was to be driven by hand power, the screw being driven by eight labourers. The balloon was actually made and tested. Considering the h.p. was 0.8, it is needless to say it was not successful.

It was during the siege of Paris that Krupp constructed the first special gun for attacking balloons, a relict which has been preserved at Berlin.

If such was the utility of balloons that merely drifted at the mercy of the aërial currents they encountered, it was not to be wondered at that, soon after the Franco-Prussian War, new attempts were made to make them navigable. Though the term airship might reasonably be applied to all the forms of navigable aircraft still in this country, it has been applied in a less wide sense to those machines that are lighter than air. In these pages the term will be used in this connection.

The effort to navigate balloons almost dates back to the invention of the balloon itself. It was, indeed, early realised that the spherical shape of the ordinary balloons that drift with the winds would be unsuitable for a craft that would have to travel against the wind. In 1784 Meusnier designed an elongated airship, in which the brothers Robert actually ascended. It is noticeable that in this early design of Meusnier was the now well-known ballonet, or inner balloon, which forms an essential feature of modern non-rigid and semi-rigid airships for preserving the rigidity of the outer envelope and facilitating ascent or descent.

If we except the effort of Dupuy de Lôme, the next remarkable attempt at airship construction was in 1852, when the Parisian Giffard made his steam-driven elongated balloon, with which he made two experiments. These merely proved that successful navigation against a wind would require much larger motive power than his Lilliputian steam-engine of 3 h.p. Giffard, however, was the pioneer of the airship driven by other than hand power. The following are the dimensions, etc., of what will ever be an historic balloon:—

The experiments of Krebs and Renard in 1885 were noteworthy. They were the first in which direct return journeys were made to the place whence the balloon started.

These experiments showed the importance of the military factor in the development of aërial navigation. Krebs and Renard were the officers in charge of the French Military Aëronautical Department at Meudon, and they applied national funds to the construction of an airship. It was the development of the electrical industry and the production of electric motors at that time which stimulated the experiments. The brothers Tissandier had, in 1883, propelled an elongated balloon against a wind of some three metres a second by means of an electric bichromate battery which supplied the power to an electric motor. It was thought that those experiments had been sufficiently successful for further trial of the powers of electricity.

Renard made profound and exhaustive researches into the science of the navigable balloon. To him we are, indeed, indebted for the elucidation of the underlying principles that have made military airships possible.

The navigable balloon “La France” was dissymmetrical, being made very much in the shape of a fish or bird. Its master diameter was near the front, and the diameters diminished gradually to a point at the back.

The following were the dimensions of the envelope:—

The airship was remarkably steady on account of the minute precautions taken to counteract the instability produced by a somewhat excessive length. Any device which modifies pitching at the same time lessens the loss of speed resulting from the resistance of the air when the ship is moving at an angle. A direct means of reducing pitching is the dissymmetrical form given to the envelope by placing the master diameter near the front. The resistance of the air falls on the front surface, which in this dissymmetric form of envelope is much shortened, while the compensating surface at the back is augmented. Many experts are of opinion that in this form of envelope Krebs and Renard came nearer perfection than any other navigable balloon constructor.

Like the brothers Tissandier, they used an electric battery and motor to drive their screw, their motive power being 9 h.p.

It was claimed that out of seven journeys, the airship returned five times to the place whence it started. As an example of these journeys, on September 22nd, 1885, a journey was made from Meudon to Paris and back again. On this day the wind was blowing at a velocity of about 3.50 metres a second—what we should call a calm. Few, perhaps, who saw the small naval airship, the “Beta,” manœuvring over London this autumn realised that a navigable balloon, not so very much unlike it in form, was speeding its way over Paris as long ago as 1885. The advent of the first at all practical military airship was forgotten because the experiments, comparatively successful as they were, suddenly ceased. They came to an end because it was found that though electricity as a motive power could afford an airship demonstration, it was unfitted for serious and prolonged use.

One industry has often to wait for another—the world had to wait for the missing link in aërial navigation. That was the light petroleum motor. With its coming came the era of airships and aëroplanes.

CHAPTER III
TYPES OF MODERN AIRSHIPS

With the new century came the modern military airship—to stay, at any rate, until the heavier-than-air principle of aërial navigation has so developed as to absorb those features of utility the airship has and the aëroplane has not.

During the fourteen years which have seen the construction of practical airships, three distinct types have been evolved—(i.) rigid, (ii.) non-rigid, (iii.) semi-rigid. In considering the airships of Great Britain, France, and Germany, I propose to class them together as to types rather than under nationalities.

Each type has its own peculiar advantages. The choice of type must depend upon the circumstances under which it is proposed to be employed.

Top: SNAPSHOT OF ZEPPELIN IN MID-AIR.

Centre: MILITARY LEBAUDY AIRSHIP, showing fixed vertical and horizontal fins at the rear of gas-bag, vertical rudder, and car suspended from rigid steel floor underneath gas-bag.

Bottom: CAR OF A LEBAUDY AIRSHIP, showing one of the propellers.

I. Rigid Type.

(i.) Zeppelin (German).—There are not many examples of the rigid type. The most important is undoubtedly the Zeppelin. This form of airship before the present war had elicited the interest of the aëronautical world for the long-distance records it had established. Indeed, no little sympathy had been extended to Count Zeppelin for his perseverance in the face of the gravest difficulties. Now the Zeppelin has accumulated notoriety instead of fame as having been the means of carrying on a form of warfare repugnant to the British nation, and condemned by the Hague Convention. Imagine some seventeen huge bicycle wheels made of aluminium, with their aluminium spokes complete, and these gigantic wheels to be united by longitudinal pieces of aluminium, and in this way seventeen sections to be formed, each of which contains a separate balloon, and it is easy to grasp the construction of the Zeppelin airship. It consists of a number of drum-shaped gas-bags, all in a row, held together by a framework of aluminium. They form a number of safety compartments. The bursting of one does not materially matter—the great airship should still remain in the air. The dimensions of individual Zeppelins have varied to some extent. The largest that has been built (“Sachsen,” 1913) had a cubic capacity of 21,000 cubic metres (742,000 cubic feet), and a length of 150 metres (492 feet). The aluminium framework containing the balloons has an outer covering of cloth. On each side of the frame of the airship are placed two pairs of propellers. In the original airship of 1900 these were four-bladed, and made of aluminium. They were small, being only 44 inches in diameter, but they revolved at a very high speed. In the later airships the screws have been considerably modified in detail, size, and shape. For instance, in the Zeppelin which descended accidentally at Lunéville, in France, it was found that the back pair of the propellers on each side were four-bladed, the front pair two-bladed. The screws are driven by motors placed in the two aluminium cars beneath the airship. These cars are connected by a covered gangway, which also serves as a track for a movable balance weight, by means of which a considerable change of balance can be effected. The motive power in the first Zeppelin was only two Daimler motors of 16 horse power each. With this low power little success was attained, but gradually the motive power has been increased. We find that in the naval Zeppelin, L 3, 1914. The motive power is three Maybach motors, giving total h.p. 650, whereas in the types building the total h.p. is 800.

The stability of these aërial monsters is attained by the use of large projecting fins. Horizontal steering is effected by a large central rudder and pairs of double vertical planes riveted between the fixed horizontal stability planes. For vertical steering there are sixteen planes provided in sets of four on each side of the front and rear ends of the balloons. These can be independently inclined upwards or downwards. When the forward ones are inclined upwards and the after planes downwards, the reaction of the air on the planes as the airship is driven forwards causes the front part to rise and the rear part to sink, and the airship is propelled in an inclined direction to a higher level. The favourite housing place for the Zeppelin airships has in the past been on Lake Constance, near Friedrichshafen, so that they could be taken out under protection from the direction of the wind. It is also much safer for large airships to make their descent over the surface of water. It has been estimated that the most powerful Zeppelins have a speed of some fifty miles an hour.

When on April 3rd, 1913, Z 16, in the course of a journey from Friedrichshafen, was forced to descend on French soil at Lunéville, excellent opportunity was afforded the French of a close inspection of its details.

The following were the exact dimensions, etc.:—

On the top of the ship was a platform, on which a mitrailleuse could be mounted.

It was only a few weeks before the present war that the new Zeppelin, L Z 24, attained a new world’s record of altitude and duration of flight. The height attained was 3,125 metres. The voyage without a break lasted thirty-four hours fifty-nine minutes. On May 22nd, 1914, it left Friedrichshafen at 7.16 a.m. Bâle was reached at 10 a.m. At 6 p.m. it passed Frankfort, at 9 Metz, at 10.30 Bingen, at 2 a.m. Brême. At 4 a.m. it arrived above Heligoland, from whence it made for Potsdam, where it was hailed 9.20 a.m. At 5.15 p.m. it landed at Johannisthal.

That journey certainly showed the long-range powers of the latest Zeppelins. If, as will be seen, it is comparatively easy for a few well-directed aëroplanes to wreck them in mid-air, still they have ceased to be military or naval playthings.

(ii.) Schutte-Lanz (German).—The Schutte-Lanz rigid airship is an attempt to secure the advantages of the rigid type without the fragilities of the Zeppelin. The framework, which contains the separate gas compartments, is made of fir wood. The gas-bags are claimed to be very strong. These are filled, excepting two, which remain empty when there is only sea-level pressure; when, however, the gas expands, it flows into the latter. These become full when an altitude of some 2,000 metres is reached. A centrifugal pump is employed for distributing the gas.

The volume of this airship is 26,000 cubic metres (918,000 cubic feet). It will be seen, therefore, that this mammoth airship in size surpasses even the largest Zeppelins.

II. Semi-rigid.

(i.) Lebaudy (French).—This airship is a crossbreed between the rigid and non-rigid systems. By this method of construction a considerable amount of support can be imparted to the gas-bag, though it does not dispense with the services of the ballonet, as does the entirely rigid type. To the genius of M. Julliot, Messrs. Lebaudy Brothers’ engineer, we are indebted for the introduction of this excellent type. It no doubt forms an exceedingly serviceable military airship. In the Lebaudy original airship the underside of the balloon consisted of a flat, rigid, oval floor made of steel tubes; to these the stability planes were attached, and the car with its engine and propellers was suspended. This secured a more even distribution of weight over the balloon. The gas-bag was dissymmetrical in form. Though not exactly resembling that excellent pattern, “La France,” it partook of the important quality of having the master diameter near the front. The car was a steel frame, covered with canvas, and in the form of a boat. The screw propellers were placed on either side of the car.

In 1909, as the British Government at that time possessed only very small airships, the nation raised a sum of money by subscription to present the Government with one of efficient size. The military authorities compiled a list of somewhat severe tests which, in their opinion, they thought an airship should be able to perform before acceptance. At the request of the Advisory Committee, of which Lord Roberts was chairman, the writer went to France in an honorary capacity to select the type of airship to be adopted. There was at that time only one firm of airship makers in France who were willing to undertake the formidable task of making an airship that would come up to the requirements of the British Government—the brothers Lebaudy, whose engineer and airship designer was M. Julliot.

The semi-rigid airship which M. Julliot designed and executed was without doubt a chef d’œuvre of its kind. The rigid tests it had to undergo necessitated a modification of some of the details that were conspicuous in the airships the constructor had previously built.

In this airship the girder-built underframe was not directly attached to the balloon, but suspended a little way beneath it.

The gas envelope had a cubic capacity of 353,165.8 cubic feet; the length was 337¾ feet. There were two Panhard-Levasseur motors of 135 h.p. each.

On October 26th, 1910, this airship made an historic and record flight over the Channel from Moisson to Aldershot in five hours twenty-eight minutes, at a speed of some thirty-eight miles an hour, sometimes against a wind of twenty-five miles an hour. Unfortunately, owing to a miscalculation by those responsible, the shed which had to receive the new airship on its arrival was made too small to house it safely. While the airship was being brought into the shed its envelope was torn and placed hors de combat.

Since this airship was made the Lebaudy brothers have ventured to still further increase the size of their semi-rigid airships.

(ii.) Gross (German).—This airship may be described as being more or less a German reproduction of the Lebaudy type. It forms part of the German airfleet. A considerable number have been made of various sizes (for dimensions, etc., see table, German Airships, Chapter IV., [page 38]).

III. Non-rigid.

This type is dependent for its maintenance of form on the pressure of the gas inside the envelope. It is all-important that the envelope of a navigable balloon should not lose its shape—that it should be kept distended with sufficient tautness, so that it may be driven through the air with considerable velocity. On this account the non-rigid type depends entirely on the ballonet system, which consists of having one or more small balloons inside the outer envelope, into which air can be pumped by means of a mechanically driven fan or ventilator to compensate for the loss of gas from any cause. The ballonets occupy about a quarter of the whole volume of the envelope. Such a type is exceedingly well suited for the smaller-sized airships, destined rather for field use than long-range offensive service. Such airships are quickly inflated and deflated. They are also easily transported. Even the Lebaudy or Gross semi-rigid types, though not so clumsy or difficult of transport as the Zeppelins, require more wagon service than the absolutely non-rigid.

PARSIFAL AIRSHIP LEAVING ITS HANGAR.

PARSIFAL AIRSHIP,
showing one of the fixed horizontal planes, steering rudder, and car.

The British Government have evolved several non-rigid airships of moderate dimensions which have been exceedingly useful as ballons d’instruction. For obvious reasons it is not desirable that particulars concerning them should be published at the present crisis.

(i.) Parsifal (German).—Very numerous examples of non-rigid airships could be cited, but it will suffice now to mention two, the German Parsifal and the French Clement-Bayard. The Parsifal is the only type that the German nation has allowed to be supplied to foreign countries. For instance, our Navy possesses one. It has also been supplied to Austria, Italy, Russia, and Japan. On account of its portability it is perhaps the most generally useful type of airship that has been designed, if we exclude long-range service. It has been exceptionally free from accidents on account of its subtleness. The originator of the Parsifal seems to have thoroughly grasped the sound idea that to attain success in navigating a subtle medium like air the machine should be correspondingly subtle—as, indeed, are the animal exponents of flight.

In the Parsifal the exclusion of the element of rigidity has been carefully studied. All that is rigid about it is the car and motor, and this can be conveyed in one cart.

The size of the Parsifals has been advisedly limited. The majority of them are not more than a third of the cubic capacity of the Zeppelins. A distinctive feature is the distance of the car from the gas-bag. This in the first types constructed was nine metres, though in more modern forms the figure is less. Owing to the distance of the car from the main body the attaching cords are distributed with equal tension over the whole length of the envelope. In the Parsifal airships there are two ballonets, one at the front and one at the back of the gas-bag. They are not only used for keeping the envelope rigidly expanded, but also to facilitate rising and falling, air being admitted into the one and expelled from the other, as the case may be. Another distinctive feature is the four-bladed propellers. These have fabric surfaces, and are weighted with lead. When at rest the blades are limp, but in revolving, owing to centrifugal force, they become endowed with the necessary rigidity. The dimensions of the Parsifals vary considerably, the smallest made had a capacity of 3,200 cubic metres (1908), the largest more recent ones have a capacity of 11,000 cubic metres. A very useful size is the P L 8 (1913), station Cologne, of which the dimensions are:—

(ii.) Clement-Bayard.—It is a question whether it is advisable to extend the non-rigid system to the amount that has been latterly done in the case of such a construction as the Clement-Bayard. This type of French airship is familiar to many in this country, as it was the first airship to cross the Channel from France to England.

The cubic capacity of this airship was 6,300 cubic metres. A feature was the comparatively large size of the ballonet used. To realise how the Clement-Bayards have grown since this type of airship came to this country, see table, French Military Airships, [page 34].

Astra-Torres Type.—The Astra-Torres airships may be said to form a rather special subdivision of the non-rigid class, for, though there is no rigid metal in its construction, an unbendableness of keel is assured by panels of cloth so placed horizontally as to be kept rigid by the pressure of the air in a ballonet. Thus the virtue of rigidity is attained without the extra weight generally appertaining thereto, and a greater speed with economy of weight and size. The British naval authorities possess one of these airships. For dimensions, etc., of the latest Astra-Torres airships, see table, French Military Airships, [page 34].

It will have been seen from the above short descriptions of distinctive types of airships Germany is the only nation which makes a very marked feature of retaining the rigid form. It is true France has evolved one form of rigid, the Spiess, in which the framework is made of wood, but she undoubtedly has a preference for the semi-rigid and non-rigid types. The rigid type has not found much favour in Great Britain.

Reckoning from the year 1911, France appears to have nineteen military dirigibles, and she may have one or two older ones in repair. Some of these are building; and as in France there are many eminent aëronautical factories, there are always also a number of private airships built, or in building, of various sizes and various types. These firms have enormous private airship hangars, and every convenience for making, filling, and storing. The number of military hangars in France is seven, at the following towns: Epinal, Maubeuge, Belfort, Rheims, Toul, and Verdun, where there are two.

In the spring of 1913 the Italian military dirigible fleet consisted of two units of Series M—M1 and M2—dirigibles of 12,000 cubic metres, and three units building of Series M—M3, M4, and M5.

These dirigibles of the M series were found in practice to be the most successful; they attained a speed of 70 kilometres per hour, and a height of 2,000 metres; they are all semi-rigid. The Italian Government is ambitious of rivalling in its aëronautical fleet that of Germany, and decided in that year, 1913, on a new series—Series G. These were to be of 24,000 cubic metres, and to travel at a speed of 100 kilometres the hour.

Airships.

[A] These two carry each one gun.

At the present moment Italy is building some very large airships, some even bigger than the Zeppelin, and she practises ascents diligently with those she has. One of the new airships building for the Italian navy is a Parsifal of 18,000 cubic metres.

Great attention is paid in Russia to aëronautics. The Russians have no national types of dirigibles or aëroplanes yet developed; but they manufacture in their own country.

They have thirteen dirigibles (one is rumoured to be destroyed), semi-rigid and non-rigid, amongst them a Lebaudy made in 1910, Parsifals of 1911 and 1913, an Astra of 1913. The Parsifal of 1913 has a speed of 43–68 m.p.h. (km.).

Formerly Austria-Hungary led the way in aëronautics amongst the nations of the Triple Alliance. Germany particularly looked to her for flying machines, and the first Etrichs were hers; but military aëronautics in Austria-Hungary are now at a low ebb.

The decline is ascribed to monopoly and centralisation. At the present moment Austria has one dirigible, in a feeble condition, and about ten aëroplanes of foreign make. Two German houses, the Albatross and D.F.W., have quite lately opened branches in Austria.

The dual monarchy began well; in 1909 she had a small Parsifal, in 1910 a Lebaudy, in 1911 the Körting. These three perished in accidents. Her own system, the Boemches, presented to her by a national subscription, failed in speed; but though she has no dirigibles to inhabit them she has three good hangars!

Belgium has three airships, all non-rigid—two Godards and one Astra. Although not of very late construction, all three have innovations and interesting features. The Astra is private property.

[Topical Press.

ZEPPELIN AIRSHIP AT COLOGNE,

showing at the rear large vertical rudder, and two pairs of vertical rudders for horizontal steering, the horizontal planes at the sides for vertical steering, two of the four propellers at side of airship, car beneath airship.

CHAPTER IV
THE GERMAN AIRSHIP FLEET

Many reports have been current concerning the exact dimensions of the airship fleet that Germany can put into action. It has been said that she has been extremely active since the beginning of the present war in adding fresh units to the forces she had available when the war broke out. It has also been rumoured that she is making a new type of Zeppelin—one much smaller, and which will have greater speed than the larger type.

German Airships in the Spring of 1913.

(1) and (2) as in 1911; since then they have been renovated, and no doubt their speed and volume are much greater.

We must accept with some reserve the reports that are current in this respect, and it may be pointed out that in accounts of the doings of Zeppelin airships in the papers it can be reasonably doubted whether all the Zeppelins mentioned are in reality Zeppelins. Probably some are the smaller types, such as the Gross or Parsifal. The word Zeppelin seems to have become synonymous with a German airship, and the wounded soldiers or prisoners who are responsible for many of the stories told would not be likely to have complete knowledge of the distinctions between classes of airships.

Though what Germany is exactly doing in way of new manufacture must remain in much fog, still we can form some opinion as to her preparedness with aircraft on the lighter-than-air principle from our knowledge of what she possessed last year.

The table on the opposite page will show that her fleet of airships, including those under construction, was then by no means negligible.

A nation possessing such a fleet of large airships as Germany does must be provided with sheds (hangars) for their reception in all parts of the country, and by the table that is appended it will be seen that in this way last year Germany was very amply provided.

I am indebted to the Aérophile for the following list of German hangars for dirigibles, with dates of construction and names of owners:—

Such monster airships as the Zeppelin call for a large proportion of pure hydrogen. This is, indeed, manufactured on a large scale in Germany. It is produced in quantities by the electro-chemical works at Bitterfeld, Griesheim, and at Friedrichshafen, specially for the needs of the Zeppelins at the latter place. There are also works for the production of very pure hydrogen by electrolysis at Bitterfeld, Griesheim, Gersthofen, and Dresden.

In the particular way Germany means to use her lighter-than-air fleet in the present war time will show. If, however, there have not yet been attempts at any combination of action, individual Zeppelins have already played the rôle of dreadnoughts of the air. Though their powers have been no doubt exaggerated, they have been the terror of some Belgian cities.

Early in the morning of August 25th a Zeppelin airship visited Antwerp, and drifting silently with the wind steered over the temporary Royal palace. There it discharged six highly explosive bombs. Not one found its intended mark, though all fell near the palace. One appears to have been very near hitting the tower of the cathedral. Though the bombs failed to attain the object sought, no less than six or seven persons were victims to the outrage. One struck a private house, killed a woman, and injured two girls, killed two civic guards, and wounded another. One bomb fell in the courtyard of the hospital of St. Elizabeth, tore a hole in the ground, smashed the windows, and riddled the walls.

The Zeppelin repeated its visit early in the morning of September 2nd, but this time with less deadly result. The bombs only wounded the victims. The experiences of the first visit had given effective warning against a repetition of aërial invasion. The city had been darkened, and the airship was attacked from the forts and the high points of the city as soon as it made its appearance. The crew of the airship seem to have been struck with panic when it failed to find its bearings over the darkened city.

It appears they suddenly dropped all their bombs as ballast and rose quickly out of harm’s way. The bombs used on this occasion were not of the same type as those used on the previous attempt on the city. The latter were of high explosive power designed to destroy buildings. The former were covered by thin envelopes, and held together by mushroom-shaped rivets. They were filled with iron bolts and nuts, and were evidently designed for the destruction of human life. It is stated that this is a type of bomb which has never been used by artillery, being made on the same model as that used by the notorious French robber, Bonnet.

In reference to airship raids over cities, it has been suggested in America that the air in their immediate neighbourhood should be mined. This could be done by having a number of captive balloons or kites, the mines on which could be discharged electrically from the ground. For future wars there will no doubt be devised some form of travelling aërial torpedoes for destroying the intruding airships. Such torpedoes would, however, have to be capable of guidance. As has been pointed out by Mr. W. F. Reid, in 1884, at the siege of Venice, the Austrians used free balloons for the purpose of dropping bombs upon the town. The bombs were attached to the balloons in such a way that after the burning of a certain length of safety fuse, the connection was severed, and the bomb fell. The length of fuse was calculated according to the speed of the wind; but, unfortunately, when the balloons rose, they entered an upper air-current travelling in a different direction from that below, and many of the bombs burst in the Austrian lines, whence they had started. Thus it would not be expedient to let loose ordinary unmanned balloons loaded with timed explosives, even if the direction of the wind seemed favourable, for their meeting an approaching airship fleet, as an upper current might bring them back over the city, where they might do mischief.

It is, however, quite conceivable that in the future aërial torpedoes may be devised in the shape of unmanned balloons or aëroplanes controlled by wireless waves of electricity. Those who saw the striking experiment of steering a small navigable balloon in a large hall entirely by wireless electric waves must have realised the possibilities which may thus be opened out in the future.

* * * * *

While writing, the news has come that another Zeppelin has dropped three bombs on Ostend, the casualty list being one dog. Two unexploded projectiles were found on a field near Waeragheim. These were probably thrown from the same airship. They show how constantly missile throwing from a moving airship may fail to come near the mark. There is no doubt that to hit particular objects aimed at from airships is by no means an easy matter. Success would seem to require considerable training in this particular method of warfare. The late Colonel Moedebeck, in his well-known pocket-book of aëronautics, makes the following remarks on the throwing of balloon missiles:—

We may assume that, if handled skilfully, the object aimed at will be hit very exactly. We must distinguish between the throw when the airship is at rest and that when it is in motion. In throwing out while at rest, which is only possible when the airship can travel against the wind, the following points must be considered:—

(a) The height of the object.—This may be accurately determined from the contour lines on the map, or from a determination of its normal barometric height. Both must be done before starting.

(b) The height of the airship above the object.—The barometric height is read and reduced to normal conditions. The difference in heights as found from (b) and (a) gives the height above the object.

(c) The velocity of the wind.—May be read on an anemometer in the airship, or determined beforehand by captive balloons.

(d) The time of fall.—Given by the law of gravitation from the determination under (b).

The height of fall = h = gt²/2.
Whence the time of fall t = √(2h/g).

(e) The resistance of the air. R = (γ/g)Fv².

(f) The leeway.—The longer the fall, and the lighter and larger the falling body, the stronger is the drift. For known missiles, the drift for different heights and wind velocities may be determined practically.

(g) Unsteadiness of the airship.—The irregularity of the pressure of the wind, and its constant variation in direction, renders it impossible for the airship to remain perfectly steady.

The elements stated under (b) and (f) must be rapidly determined, and suitable tables have been prepared for this purpose. The irregularity of the wind and the peculiarities of the airship mentioned under (g) render a preliminary trial necessary. The drift also is determined by this method, before the large air-torpedo is cast out.

The air-torpedo must be brought by sight vertically over the object by steering the airship, the value of the mean drift previously determined being allowed for.

In throwing out a missile while actually travelling, the velocity of the airship must be taken into account, as well as the elements (a) to (g) given above, since this velocity is also possessed by the body thrown out.

The determination of the proper point is now greatly increased in difficulty. Its position is a function of the relative height of the airship above the object, of the velocity, and of the drift, and allowance must be made for all these factors. For this purpose, motion, either with or against the wind, is the simplest. On account of the point on the earth over which the missile must be thrown out not being in general well marked, it is necessary to use also angles of sight.

The problem before the aëronaut is, then, as follows:—For a given height, velocity, and drift to find the necessary angle of depression at which the missile must be thrown out in order that it may fall on to the object.

The casting out of the missile against the object while travelling is governed, therefore, by the same rules as those governing the discharge of a torpedo from a torpedo-boat.

CHAPTER V
ADVANTAGES AND DISADVANTAGES OF AIRSHIPS

The chief advantages of aircraft that are lighter than air over those that are heavier than air in warfare are:—

1. Their speed can be variable.

2. They can hover over a particular point.

3. They can be noiseless by cutting off motive power and drifting for a while with the wind.

4. They can from their possible size have long range of action.

5. They can carry considerable weights.

6. They are endowed with sustaining power and stability.

1. Their speed can be variable.

This advantage becomes apparent in cases where they are used both for scouting and offensive purposes.

In a later chapter it will be pointed out that though the aëroplane scout has often to make dashes over the enemy, and it would be thought that from his swift movements his impressions might be vague, still, in practice, most satisfactory work has been undoubtedly accomplished. Many, however, will maintain that there are circumstances when it may be advisable for observers to proceed at variable speeds. When at a safe height it may be an advantage for the observers to take their time and leisurely survey the country, observe, and take photographs. The airship can stealthily travel over camp and fortress and steal secret after secret of the enemy.

2. They can hover over a particular point.

The fact that the maintenance of the airship in the air does not depend upon a certain speed being maintained, as is the case with the heavier-than-air machine, endows it with the property of being able to hover in fairly calm weather. The hovering power is certainly an advantage for such offensive operations as dropping bombs.

3. They can be noiseless.

At night it may often be possible to approach over a fortress, camp or city quite noiselessly at a low altitude by shutting off the motive power and navigating by means of the natural forces alone.

4. They can from their possible size have long range of action.

From their size and the amount of fuel they can carry it is possible for them to travel for long distances.

This quality renders them specially fitted for naval purposes, though possibly in the not very distant future more highly developed hydroplanes will run them very close.

5. They can carry considerable weights.

The weights large airships can carry is an advantage in offensive operations. It enables larger stores of bombs to be carried than is at present possible with aëroplanes. Then several persons can be carried long distances in the larger airships.

6. They are endowed with sustaining power and stability.

As the envelopes of airships are filled with a gas which lifts and sustains, the great disadvantage of instability which is the bugbear of aëroplanists is absent. If engines break down or stop, it does not necessarily mean that the airship must immediately descend. It can often remain in the air while the machinery is being repaired.

But in spite of these advantages airships have very numerous counterbalancing disadvantages, so marked, indeed, that it seems a question whether, if the world decided to entirely use aëroplanes in their place, it would be much the loser.

The principal disadvantages would seem to be:

1. The resistance of the gas-bag.

2. Danger of fire from close combination of petroleum motor and gas-containing envelope.

3. Danger of fire from self-electrification of surface.

4. Difficulties in the way of applying the propulsive screws in the most effective position.

5. Difficulties of making gas envelope gas-proof.

6. Great cost of airships.

7. The great amount of personnel needed for the manipulation of large airships.

8. Great liability of being destroyed by aëroplanes in war.

9. Insufficient power of quickly rising.

1. The resistance of the gas-bag.

From a mechanical point of view it is in opposition to science to attempt aërial navigation by pushing such a large resisting surface as the envelope of an airship against the air. In navigating an airship against the wind, as the latter increases speed is diminished, until a limit is reached when the motive power will be unavailing. Thus there are weather limitations to the airship. Not that the aëroplane is unaffected by the weather. That also has its limits; but recent practice has shown that the proportion of days when aëroplanes can fly is considerably larger than those on which airships can venture forth from their sheds.

This disadvantage of the resistance of surface was very manifest in the earlier experiments with navigable balloons, when only feeble motive power was available. For instance, in Count Zeppelin’s experiments in 1900, his two motors of 16 h.p. could not combat a greater wind force than about three metres a second. Then airships could indeed only be called toys. It has only been possible to make them partially successful concerns by enormously increasing motive power. At the h.p. figures with which the latest made large airships have been endowed, the wind limit is much lower than in the case of the heavier-than-air constructions. Though now airships can encounter moderate winds, they are still fair-weather instruments. For the great records of distance established by Count Zeppelin favourable meteorological conditions have been wisely selected. It was M. Santos Dumont who first led the way in making airships something beyond toys. He, in his picturesque and world-alluring experiments, first dared to encounter winds which in force exceeded what would be called calm weather. It is exceedingly difficult to ascertain what are the exact wind forces overcome by a body moving in air. The measurements have to be taken from a point independent of the moving body. We generally find this one important figure omitted in accounts of airship voyages. M. Santos Dumont’s experiments gave especially favourable opportunity for ascertaining correct records of the wind forces overcome. Since M. Santos Dumont so frequently rounded the Eiffel Tower close to the storey where the meteorological instruments were placed, the writer obtained from the authorities of the Eiffel Tower a record of the wind forces registered on all the days of his experiments. A comparison of those records with those of M. Santos Dumont’s journeys made it possible to approximately ascertain the highest wind forces he combated on his journeys round the tower; these were about five metres a second. M. Santos Dumont, however, appears to have claimed six metres a second for his highest wind record.

The brothers Lebaudy in their earlier experiments about doubled the record of Santos Dumont in this respect. As time has gone on greater advance has been made, though the limit is still represented by moderate wind.

There is, perhaps, some consolation in this thought for those who fear raids of an inimical airship fleet. The proverbial windy nature of our favoured islands is perhaps even more protection than darkened cities and artillery shot, though it is well indeed not to neglect the two latter precautions.

Meteorologically speaking, to make a raid with bulky airships from a distance over these islands would be a very risky undertaking, fraught with the greatest danger to the occupants of the airships. It must be remembered that, chiefly owing to the weather, the history of the Zeppelin may well be called the history of disaster. For the very reason of its fragility over and over again it has been the victim of tempest and flame.

The use of aluminium for the framework of the Zeppelins has been largely responsible for Count Zeppelin’s repeated weather misfortunes. There has been a fascination about this brittle metal aluminium for aëronautical work on account of its lightness. Its employment for aircraft construction, except for trivial purposes, is, however, a fallacy. That most practical aëronautical engineer, M. Julliot, in working out his semi-rigid constructions, has never fallen into the snare of aluminium allurement, wisely using steel instead. Considering the aluminium framework of the first Zeppelin constructed was fairly wrecked by the trifling accident of its falling down from the ceiling of the shed to the floor, it is a wonder that this species of metal has been retained, to be crumpled up almost like paper in the many accidents that have occurred.

2. Danger of fire from close combination of petroleum motor and gas-containing envelope.

In airships of all three types—rigid, semi-rigid, and non-rigid—this danger is constantly present. There have been examples of airship conflagrations in mid-air, but the greatest danger of conflagrations is in descending when the airships have been overtaken by strong and gusty winds. As has before been stated, fire has been the great destroyer of the Zeppelins.

The nearer the car containing the motors is placed to the gas envelope, the greater the fire risk becomes. The Parsifal airship, in which the car is suspended a considerable distance from the gas-bag, should in this respect be the safest of all the types of airships yet constructed.

3. Danger of fire from self-electrification of surface.

This appears to be a great danger in the case of airships whose gas-bags are made with india-rubber surfaces. No less than two Zeppelins have been destroyed from this cause. In the case of the explosion of the gas in a Zeppelin of 1908, when it burst from its anchorage at Echterdingen, the destruction of the airship appears to have been caused by electric sparks produced by the friction of the material of which the gas-bag compartments were made. Colonel Moedebeck, in the Aëronautical Journal of October, 1908, gave an expert opinion as to the cause of this accident:—

The balloon material, which is india-rubber coated, has the peculiar property of becoming electrified in dry air. When rolled up or creased in any way it rustles, and gives out electric sparks, the latter being (as shown by the experiments undertaken by Professor Bonsteim and Captain Dele for the Berlin Aëronautical Society) clearly visible in the dark.

Now, the lower parts of the material of which the gas-cells are composed would, owing to the height to which the airship had ascended (1,100 m.) and the release of gas from the valves, become creased or folded upon each other, and the rubbing thus produced would be quite sufficient to generate the electric sparks above referred to. Under ordinary circumstances, when the space between the gas-cells and the outer envelope of the airship is full of atmospheric air, continually renewed, as when it is in full flight, these sparks would be harmless enough, but when the ship is at anchor, as at Echterdingen, this is not necessarily the case.

We know that the carefully made tissue of the Continental Caoutchouc Company resists the penetration of hydrogen very strongly, but some may have leaked through into the space between the cells and the outer envelope, while it seems very probable that when the mechanics opened the valves, and the long axis of the balloon became inclined, more hydrogen entered this space and an explosive mixture was formed.

According to the description given by eye-witnesses, the explosion took place after the forepart of the vessel (dragging its anchor) struck the ground. The shock thus caused would have been transmitted to the creased and wrinkled gas-cells, and the tearing of the material, already in an electrified condition, might easily have generated sufficient sparks to detonate the explosive mixture.

Again, in 1912, there was a repetition of this kind of disaster in the case of the destruction of another Zeppelin, the “Schwaben.” In this case the framework of the airship had got broken, being battered about in landing in an adverse wind. The india-rubber-coated bags were rubbed against each other, with the production of electric sparks. These either set fire to the gas issuing from one of the gas-bags or exploded the mixture of air and gas contained in the space between the gas-bags and outer covering of the airship. Perhaps it was on account of this accident that gold-beaters’ skin has sometimes been used for the gas containers of the Zeppelin airships.

4. Difficulties in the way of applying the propulsive screws in the most effective position.

Most airships are exceedingly defective in this respect, the screws being applied to the propulsion of the car and not to the whole system. The result is that the cumbersome gas-bag lags behind. Certainly, one of the best points in a Zeppelin was the attachment of the screws to the airship framework above the cars, thus securing more advantageous position. This, however, only amounted to something like half measures. In the case of the ill-fated airship “La Paix,” the Brazilian aëronaut Severo undoubtedly aimed at the ideal, though the experiment cost him his life. He devised the ingenious system of combining balloon and car in one symmetrical melon-shaped body, through the centre of which passed longitudinally the shaft which revolved the propelling screws at either end. The screws were therefore in the position in which to propel the whole system and not the car only. This, however, necessitated the introduction of a very small space between the car and balloon proper. By reason of this very small space the presence of the petroleum motor in the car could not fail to be dangerous, and was the cause of the fiery end of Severo’s balloon and the death of the inventor and engineer. On the morning of the ill-fated May 11th, 1902, Severo and Sachet ascended in “La Paix.” A few moments after the ascent the balloon exploded, in the words of an eye-witness, like a crash of thunder, and the occupants were precipitated to the ground.

In spite of the engineering advantages of Severo’s system no one has dared to revive the plan.

It has, however, been pointed out by the writer—and the suggestion elicited the keen interest of the late Professor Langley—that if electricity could be used as the motive power in an airship the Severo system could be reasonably revived. Then the electric motors could be inside the gas-bag. There, electric sparks and electric heating could do no harm. For it is only the borderland that is the place of danger, where there are oxygen atoms to combine with the hydrogen atoms. In the case of a balloon filled with gas it is surprising to what short distance the danger zone extends. In the case of the writer’s electric signalling balloons, on one occasion the ladder framework which supported the incandescent lamps was being hauled up into the balloon. Through some fault in the connections there was sparking at the framework just as it had passed over the dangerous borderland. The sparks went on with safety. An inch or two lower and there would have been an explosion!

But on account of the weight of the battery the practical application of electricity for propelling navigable balloons seems to be as far off as it was in the days of “La France,” and in airships we have to continue placing the screws in the wrong place.

5. Difficulties of making gas envelope gas-proof.

The absence of the knowledge how to obtain a really gas-proof envelope is, no doubt, one of the greatest difficulties of airship construction. As has already been pointed out, the gas-holding quality of gold-beaters’ skin is remarkable. Its cost, however, is fairly prohibitive in the case of large airships. A material which is a combination of india-rubber and cotton surfaces is now generally used for large airships, but this has undoubted disadvantages. India-rubber is a substance which time, low temperature, and certain climatic conditions deteriorate. All those who have worked with india-rubber experimental ballon-sondes (sounding balloons) can testify to its perishing qualities. Very much can be accomplished with a brand-new airship. Turned out of a factory it will retain its gas-holding qualities for a short time excellently. The lapse of time reveals deterioration and leakiness.

Considering the extreme importance of a varnish that will retain pure hydrogen for a reasonable time, it is a matter of surprise that chemists should have almost entirely neglected its production. Mr. W. F. Reid alone of British chemists seems to have given any serious thought to the question. In a paper which Mr. Reid read before the Aëronautical Society of Great Britain, he made some exceedingly important suggestions in the way of obtaining balloon and airship varnishes. In case this little volume should fall into the hands of any chemists who may like to devote their powers of original research to the production of one missing link in airship construction, the following quotation from Mr. Reid’s remarks are appended below.

Varnishes may be divided into two classes—those in which the film solidifies or “dries” by absorption of oxygen from the air, and those in which the varnish “sets” by the evaporation of a volatile solvent in which the solid ingredients have been dissolved. To the first class belong the drying oils, chiefly linseed oil, for, although there are a number of “drying” oils, but two or three of them are used commercially in the manufacture of varnishes. When exposed to the air, especially in warm weather, linseed oil absorbs oxygen and forms an elastic translucent mass termed by Mulder “linoxyn.” This linoxyn has completely lost its oily nature, does not soil the fingers, and is, next to india-rubber, one of the most elastic substances known. It possesses but little tensile strength, however, and can be crumbled between the fingers. It forms the basis of all linseed oil paint films, and is largely used in the manufacture of linoleum. Linoxyn, however, is not, as Mulder supposed, the final product of the oxidation of linseed oil. When exposed to the air it is still further oxidised, and then forms a sticky, viscid mass, of the consistency of treacle and of an acid reaction. This latter property is of importance because it is due to it that fabrics impregnated with linseed oil so soon become rotten. In order to hasten the oxidation of linseed oil it is usually heated with a small quantity of a lead or manganese compound, and is then ready for use. No method of preparation can prevent the super-oxidation of linseed oil, but experience has indicated two ways of diminishing the evil effects so far as paints and varnishes are concerned. The first is to mix the oil with substances of a basic character or with which the acid product of oxidation can combine. In the case of paints, white lead or zinc oxide are chiefly used for this purpose. The other method consists in mixing with the oil a gum resin which renders the film harder and prevents liquefaction. Such a mixture of linseed oil and Kauri gum forms an elastic, tough mass, which is much more durable than the linoxyn alone, and also possesses greater tensile strength. During oxidation the linseed oil absorbs about 12 per cent. of its weight of oxygen, and when the area exposed is very large in proportion to the weight of the oil the temperature may rise until the mass catches fire. At a high temperature the super-oxidation of the oil takes place more rapidly than in the winter, and I have seen fabrics that had only been impregnated with an oil varnish for a month cemented together in one sticky mass, and, of course, completely ruined. When the linseed oil is thickened by the addition of a gum resin, it is too thick for direct application, and is thinned down with a solvent, usually turpentine or a mixture of this with light petroleum. Many resins and gum resins are used in the manufacture of varnishes in conjunction with linseed oil, but none of them can deprive the oil of the defect referred to, and if used in too large a proportion they become too brittle for balloon purposes. Both scientific investigation and practical experience show that any varnish containing linseed oil must be looked upon with suspicion by the aëronaut, in spite of the glowing testimonials some manufacturers are always ready to give their own goods.

When we consider those varnishes which are solutions and which do not depend upon oxidation for their drying properties we enter upon a very wide field.

Practically any substance that is soluble in a neutral solvent and leaves an impermeable film on drying is included in this class. One of the simplest examples is gelatine in its various forms, with water as a solvent. Until recently glue or gelatine would have been useless for our purpose on account of its ready solubility in water, but now that we are able to render it insoluble by means of chromic acid or formaldehyde it comes within the limits of practical applicability. A fabric may be rendered almost impermeable to gas when coated on the inside with insoluble gelatine, and on the outside with a waterproof varnish. Animal membranes are far less permeable to gases than fabrics coated with varnishes of the usual kinds. A balloon of gold-beaters’ skin, if carefully constructed, will retain hydrogen gas for a long time, and if treated with gelatine that is afterwards rendered insoluble it becomes practically impermeable. Fabrics treated with linseed oil varnish, on the other hand, allow gas to pass with comparative ease. This is not a question of porosity or “pinholes,” as is sometimes imagined, but a property inherent to the material. Hydrogen or coal gas is absorbed on the one side of the film and given off on the other in the same way as carbonic oxide will pass through cast iron. An inert gas, such as nitrogen, does not appear to diffuse in this way, even when there is a considerable difference in pressure between the two sides of the film. Such a varnished fabric transmits hydrogen readily, but retains nitrogen, and is perfectly watertight. In filling up the interstices of a fabric composed of cellulose the most obvious substance to use would be cellulose itself, but until recently solutions of this kind were difficult to obtain. Toy balloons have long been made of collodion, and are fairly satisfactory, but a cotton fabric impregnated with pure collodion becomes hard and even brittle. Celluloid solution, which is collodion with camphor and a small quantity of castor oil, is more flexible, but, probably on account of the camphor, is more permeable to hydrogen than collodion. A variety of collodion known as flexile collodion is a solution of collodion cotton with a slight addition of castor oil, and is much to be preferred to any of the preceding forms. In using it great care must be taken to exclude moisture, as the presence of this renders the film opaque, in which case it is always more or less porous. A substance allied to collodion is velvril material, composed of collodion cotton and nitrated castor oil. It is tough and flexible, even in thick films, and gives a good coating to paper or cotton fabric. Unless very carefully prepared, however, acid products may be generated from the decomposition of the nitro-compounds present, in which case the strength of the fabric would suffer. Another form of cellulose in solution is viscous, which forms a good coating when applied in a very thin layer, but makes the fabric harsh and brittle if used in excess. The solutions of this substance do not keep well and are liable to spontaneous decomposition.

The difference in flexibility between thin and thick films of the same materials is very considerable.

Given an elastic, supple cement, such as is afforded by concentrated solutions of some of the above-mentioned substances, it is quite possible to cement a tough, close-grained paper to a cotton fabric of open mesh, and the compound material thus produced is much more easily rendered impermeable than the fine cotton fabric now used. An extremely tough paper made from silk, a recent invention of T. Oishi, a Japanese manufacturer, would be specially useful for such a purpose....

It will be noticed that the texture is very compact and free from pores, as might, indeed, be expected on account of the fineness of the silk fibres of which it is composed. It must not be forgotten that cotton fibres are tubes, and gas may pass through them even when they are embedded in an impermeable film. Silk fibres, on the other hand, are solid, as well as stronger than cotton.

Another way in which a tough, flexible cement may be utilised is to cement a metal foil to a textile fabric. Aluminium foil, for instance, cemented to cotton by means of flexile collodion, gives a completely impermeable fabric of much greater suppleness than the sheet aluminium hitherto used for balloons.

Fine aluminium flakes dusted upon the freshly varnished surface adds greatly to the impermeability of the fabric, and the same may be said of coarsely powdered mica.

It may be noted in this connection that an impermeable varnish does not only apply to balloon and airship construction, but will also have its use for impregnating the planes of the heavier-than-air machines.

6. Great cost of airships.

The cost of airships compared with that of aëroplanes certainly favours the extended use of the latter in war. It is easy to spend £50,000 on a very large airship. Supposing the cost of an aëroplane seating two persons is £1,000, it is a question from an economic point of view whether the possession of fifty aëroplanes is not far better military value for the money expended on the solitary airship. But in the case of the latter it is not only initial expense that has to be considered, but cost of housing, maintenance, and hydrogen gas. These items are very considerable. The upkeep of one large airship very much exceeds that incurred with fifty aëroplanes.

7. The great amount of personnel needed for the manipulation of large airships.

It is no exaggeration to say that the ground manipulation of large airships necessitates the attendance of quite an army. In the case of a Zeppelin the exigencies of wind may call for the assistance of 300 trained sappers on landing. This is the reason why it is so advisable to have the resting-places of large airships on water. In the case of rigid airships a slight bump on the earth may do considerable damage. Colonel Moedebeck has laid especial stress on the advisability of water landing.

In practice it is never possible, even by working the motor against the wind, to avoid a certain amount of bumping, since the aërostatical equilibrium is not easily judged and allowed for, especially in strong winds. On this account the safer water landing is always preferable.

An airship can be anchored more easily with the point against the wind on water. It is quite impossible to anchor on land when assistance is not forthcoming to hold down the airship. On water, also, the airship will give a little to side winds and to alterations in the direction of the wind, without overturning. On land this danger is not excluded, even with rigid airships. Of course, a watertight and seaworthy car is a necessary condition for landing on water.

The landing requires great attention, and rapid, decisive handling and management on the part of the aëronaut.

In the opinion of the same expert airship travelling on a large scale would not be possible without the publication of special charts, which would furnish information concerning natural airship harbours, and their relation to various winds, and also of the various airship sheds which may be erected. He states it would be highly dangerous to undertake airship voyages without the existence of suitable stations against storms, and where gas supplies, driving material, and ballast could be renewed.

8. Great liability of being destroyed by aëroplanes in war.

This is no doubt one of the greatest dangers the airship has to face in war. The aëroplane is the airship’s deadliest enemy. So terrible to the airship is this hornet of the air that the former has no chance of making an attack. It must ever remain on the defensive. The speed and quickly rising power of modern aëroplanes settles this question. When the aëroplane is advancing the airship cannot escape. Nor can it now any longer rise to safe altitude, for the nimbler heavier-than-air machines can easily outdo it.

The only salvation of the attacked airship is its mitrailleuse gun fixed on the platform at its topmost part, but the chance of hitting the swiftly advancing aëroplane is fairly remote.

There are more ways than one in which the fatal attack of aëroplane v. airship can be made. The airman can, indeed, ram the gas-bags by hurling himself and machine against it. Then destruction would be swift and sure, with the probable loss of the airman’s own life. Better tactics would be to fly above, and drop suitable weapons on the fragile gas-bag; a few sharp and jagged stones would probably suffice. Sharp darts of steel would be all-effective. So easy, indeed, would it be for one aëroplane skilfully handled to end the existence of the largest airship that one cannot refrain from asking the question whether on this account alone it can survive as the instrument of war?

9. Insufficient power of quickly rising.

This is a point which wants the attention of the aëronautical engineer. The old-fashioned spherical balloons were made to rise and fall by the alternate sacrifice of gas and ballast. Thus the very life-blood of the balloon became quickly exhausted. It was obvious that when airships supplanted balloons the former must be supplied with a less exhausting process of vertical movement.

As has already been mentioned, when treating of the Zeppelin airship, for the purpose of rising horizontal planes are now fitted to airships. Some engineers have thought these should be supplemented by a mechanical device, so that the speed of rising might be augmented. The late Baron de Bradsky provided his airship with a horizontal screw placed beneath the car. But one horizontal screw beneath an airship tends to twist it round—to convert it into an aërial top. To avoid this effect it would be necessary to have two horizontal screws rotating in opposite directions. This precaution was absent in de Bradsky’s construction, and it kept on twisting round, with the disastrous effect that the steel wires which held the car to the balloon snapped, with tragic results. But the idea of the horizontal screw is worth reviving. It has been a cherished plan of M. Julliot to include the principle in his designs, but on account of extra weight he has, I believe, hitherto not tried the interesting experiment.

The colour of most of the airships is a disadvantage, though this is a matter so easy of alteration that it has not been included in the list of disadvantages.

In military airships, and, it may be added, aëroplanes also, the colour should be a neutral tint that is as invisible as possible against the sky. Most of the airships have been made a glaring yellow, so that the india-rubber in the envelopes may be better preserved from the action of light. This protection may have to be sacrificed to the overpowering advantages of invisibility in the case of naval and military airships.

CHAPTER VI
THE ADVENT OF THE AËROPLANE

The year of 1908 will be memorable in aëronautical science for its demonstration of the possibility of mechanical flight. Day after day in France and America was then seen the spectacle of men flying in the air, with a grace equal to that of the soaring bird. This was done with a machine not raised by the buoyancy of a gas, but with one that was heavier than the medium in which it travels, and whose sustentation and direction was accomplished by dexterity and skill. The experiments of the brothers Wright were new triumphs of man, new examples of the old truths that a difficulty is a thing to be overcome, and that the impossibility of to-day may be the achievement of to-morrow. This progress in human flight was not the result of any new discovery; it was the sequence of a long series of experiments; nor was it one nation only that forged the links that connected past researches to the successful issues of the present century.

It is, however, not without honour to the British nation that one of the fundamental principles of the biplane was proposed and elucidated by a Briton in 1866. I refer to the important principle of superposed surfaces advanced in that year by the late F. H. Wenham. He pointed out that the lifting power of such a surface can be most economically obtained by placing a number of small surfaces above each other. Wenham built flying machines on this principle with appliances for the use of his own muscular power. He obtained valuable results as to the driving power of his superposed surfaces, but he did not accomplish flight.

In 1872, H. von Helmholtz emphasised the improbability that man would ever be able to drive a flying machine by his own muscular exertion. After his statements there came a period of stagnation in the attempts to navigate the air by bodies heavier than air.

It is difficult to say how much aëronautical science owes to two illustrious names—Sir Hiram Maxim and the late Professor Langley. The two eminent men took up the subject of flight about the same time in the last decade of the last century, and applied to it all the scientific knowledge of the time. The flying machine had come to be associated in the public mind with foolhardiness and failure. In the discussion following Sir Hiram Maxim’s paper, “Experiments in Aëronautics,” read before the Society of Arts on November 28th, 1894, he said, “At the time I took up this subject it was almost considered a disgrace for anyone to think of it; it was quite out of the question practically.” But these two scientific men stepped into the breach, rescued aëronautics from a fallen position, and fired in its cause the enthusiasm of men of light and leading.

Sir Hiram Maxim built the largest flying machine that had been constructed. It spread 4,000 square feet of supporting surface, and weighed 8,000 lb. The screw propellers were no less than 17 feet 11 inches in diameter, the width of the blade at the tip being 5 feet. The boiler was of 363 h.p. The machine ran on wheels on a railway line, and was restrained from premature flight by two wooden rails placed on each side above the wheels. On one occasion, however, the machine burst through the wooden rails and flew for 300 feet.

In 1896 Langley’s tandem-surfaced model aërodrome had luck with the aërial currents, and flew for more than three-quarters of a mile over the Potomac River. This machine had 70 square feet supporting surface, weighed 72 lb., and had an engine of 1 h.p., weighing 7 lb. It is well known how, in later years, Langley exaggerated his model into a machine which carried a man, and how twice, when it was put to the test over water, at the very moment of being launched, it caught in the launching ways and was pulled into the water. It is interesting to note that the American aviator, Mr. Curtiss, has lately unearthed the Langley flying machine, and flown on it. Thus to Langley has come a posthumous aëronautical honour.

Lilienthal, in Germany, in considering equilibrium, experimented with what are called gliding machines—aëroplanes which are launched from some hillside against the wind, and depend upon gravity for their motive power. In this way the art of balancing could be practised on motorless gliders. With Lilienthal commenced the age of systematic experimental flight; he made the discovery of the driving forward of arched surfaces against the wind; he made some 2,000 glides, and sometimes from a height of 30 metres he glided 300 metres. The underlying principle of maintaining equilibrium in the air has been recognised to be that the centre of pressure should at all times be on the same vertical line as the centre of gravity due to the weight of the apparatus. Lilienthal sought to keep his balance by altering the position of his centre of gravity by movements of his body. One day he was upset by a side gust and was killed. Pilcher, in England, took up his work. With his soaring machines he made some hundred glides, but he also made one too many. One day, in 1899, in attempting to soar from level ground by being towed by horses, his machine broke, and he fell to the ground. He died shortly afterwards, a British martyr of the air.

Mr. Octave Chanute’s experiments in 1896–1902 formed important links in flight development. He first introduced the vital principle of making the surfaces movable instead of the aviator, and he made use of superposed surfaces. Though his work was a stage in the development of the flying machine, it was reserved to two other geniuses, the brothers Wright, to bring flight to a point of progress where prejudiced critics would be for ever silenced.

The brothers Wright first carried out laboratory experiments; they then, in 1900, first began to experiment with gliding machines at Kitty Hawk, North Carolina. With the comparatively small surfaces (15.3 square metres) they used in that year, they endeavoured to raise the machine by the wind like a kite; but finding that it often blew too strongly for such a system to be practical, in 1901 they abandoned the idea and resorted to gliding flight.

These machines of 1901 had two superposed surfaces, 1.73 metres apart, each being 6.7 metres from tip to tip, 2.13 metres wide, and arched 1-19th. The total supporting surface was 27 square metres. They dispensed with the tail which previous experimenters had considered necessary. Instead, they introduced into their machine two vital principles, upon which not only the success of their preliminary gliding experiments depended, but also their later ones with their motor-driven aëroplanes—(1) the hinged horizontal rudder in front for controlling the vertical movements of the machine; (2) the warping or flexing of one wing or the other for steering to right or left.

Later, a vertical rudder was also added for horizontal steering. The combined movements of these devices maintained equilibrium. The importance of the system of torsion of the main carrying surfaces cannot be overestimated. We have only to look to nature for its raison d’être, and observe a flight of seagulls over the sea: how varied are the flexings of nature’s aëroplanes in their wondrous manœuvrings to maintain and recover equilibrium! Since the appearance of the Wright motor-driven aëroplane, the principle of moving either the main surface or attachments to the main surface has been very generally adopted in other types of flying machines. A feature of these early experiments was the placing of the operator prone upon the gliding machine, instead of in an upright position, to secure greater safety in alighting, and to diminish the resistance. This, however, was only a temporary expedient while the Wrights were feeling their way. In the motor-driven aëroplanes the navigator and his companion were comfortably seated. After the experiments of 1901, the Wrights carried on laboratory researches to determine the amount and direction of the pressures produced by the wind upon planes and arched surfaces exposed at various angles of incidence. They discovered that the tables of the air pressures which had been in use were incorrect. Upon the results of these experiments they produced, in 1902, a new and larger machine. This had 28.44 square metres of sustaining surfaces—about twice the area that previous experimenters had dared to handle. The machine was first flown as a kite, so that it might be ascertained whether it would soar in a wind having an upward trend of a trifle over seven degrees; and this trend was found on the slope of a hill over which the current was flowing. Experiment showed that the machine soared under these circumstances whenever the wind was of sufficient force to keep the angle of incidence between four and eight degrees. Hundreds of successful glides were made along the full length of this slope, the longest being 22½ feet, and the time 26 seconds. A motor and screw propellers were then applied in place of gravity, in 1903, and four flights made, the first lasting 12 seconds, and the last 59 seconds, when 260 metres were covered at a height of two metres.

In 1904, several hundred flights were made, some being circular. All this work was carried on in a secluded spot and unpublished. In December, 1905, the world was startled by the news that the brothers Wright had flown for 24¼ miles in half an hour, at a speed of 38 miles an hour. More than this at the time the brothers would not say, and for three years the world thirsted for the fuller knowledge only revealed in 1908. In the interval some went so far as to distrust the statements of the brothers Wright; but those who, like myself, had had the privilege of correspondence with them from their first experiments felt the fullest confidence that every statement they had made was fact.

I have somewhat dwelt on the preliminary experiments of the brothers Wright with their gliding structures as indicating the rapidity of progress attained when sound scientific method is combined with practical experiment. Too often in the past there has been a tendency amongst the workers in science to keep theory and practice apart. They are, however, interdependent. Each has a corrective influence on the other.

To the labours of the Wright brothers we certainly owe the advent of the mobile and truly efficient military air scout. It is their efforts that have revolutionised warfare. In the present war we see only the beginnings of what will one day be; but they are none the less truly prophetic.

It was the enthusiastic Captain Ferber, who later became a victim to his ardour for aërial achievement, who realised what the brothers Wright had accomplished for military aëronautics. The latter having entered into communications with the French Government respecting the sale of their machines, Captain Ferber was deputed by the French Government to go to America and report on their claims. As the brothers Wright at that time so carefully guarded the secrecy of their details, he was not allowed to see the machine when he arrived, and had to be content with the mere hearsay of certain persons at Ohio, who had witnessed their flights. But he had sufficient faith in the brothers Wright to recommend the French Government to buy their invention.

The negotiations, however, fell through at the time, but in 1908 Wilbur Wright came to France to carry on experiments at Le Mans, while his brother, Mr. Orville Wright, went to Fort Myers in America.

In Wilbur Wright’s machine at Le Mans, the two superposed slightly concave surfaces were about 12.50 metres long and 2 metres wide. They were separated by a distance of 1.80 metres. At a distance of 3 metres from the main supporting surfaces was the horizontal rudder for controlling the vertical motions; this was composed of two oval superposed planes. At 2.50 metres in front of the main supporting surfaces was the vertical rudder, composed of two vertical planes.

The 25 h.p. motor was placed on the lower aëro-surface; this weighed ninety kilogrammes. At the left of the motor were the two seats, side by side, for the aëronaut and his companion. The two wooden propellers at the back of the machine were 2.50 metres in diameter. They revolved at the rate of 450 revolutions per minute.

The area of the sustaining surfaces was fifty square metres. The weight of the whole machine (with aviator) was about 450 kilogrammes. Levers under the control of the aviator regulated the various functions of the machine, the flexing of the carrying surfaces, the movements of the horizontal rudders, the vertical rudder, etc.

Soon after the experiments at Le Mans had commenced there came the news of the accident to Mr. Orville Wright’s machine in America, in which the latter’s leg was broken and Lieutenant Selfridge was killed. This was a critical moment for aëronautical science. I can myself bear witness to its depressing effect on an illustrious aëronautical assemblage, for I was myself present at Wilbur Wright’s aëroplane shed when the telegram came bearing the sad news. The sacrifice of one life at that moment seemed to counterbalance the advantages gained by the triumph of the brothers Wright. Even Wilbur Wright himself seemed to half repent he had conquered the air! He exclaimed, “It seems all my fault.” It was, indeed, then little thought what the future toll of the air would have to be.

Fortunately for aëronautical progress, two days afterwards Wilbur Wright recovered his nerve, and made the convincing flight of 1 hour 31 minutes 25 4-5th seconds.

From that day onwards there has been an increasing flow of progress in the mastery of the air.

CHAPTER VII
TYPES OF AËROPLANES

France has indeed been the breeding-place for types of aëroplanes. From France have the nations of late been largely gathering them—save Germany. She has preferred to evolve her own distinctive types. Even before Wilbur Wright appeared with his machine at Le Mans and the details were known, hearsay of his doings had fired the French imagination to do what he had done. In ignorance of the vital principle of movable surfaces that the Wrights had evolved, there came into existence the unbending, rigid type that was not destined to survive.

The first of these was the bird of prey of M. Santos Dumont. Rudely simple was it in its construction. Two box kites formed the supporting surface. In the centre was the motor, with the screw behind. To attain flight the machine was run upon wheels along the ground until a certain speed was reached, when the machine rose into the air. With this the inventor did not do much more than make aërial jumps; but rude as it was it contained one feature which has since been retained in all aëroplanes. In this one respect it was an advance—and a very necessary one—upon the Wright machine. That feature was the attachment of wheels to the machine that has been mentioned above. This was, indeed, an important step in the evolution of the aërial scout. Had it been necessary to continue using the external starting catapults that were a feature of the early experiments of the Wrights, the application of the aëroplane to warfare would have been somewhat limited.

The well-known Voisin machine was another outcome of this period, but, imperfect as it was, it brought Mr. Henry Farman into fame, for on it he was the first man in Europe to fly any distance worthy of mention.

The Farman Biplane.

Discontented with the Voisin machine, Mr. Henry Farman constructed one of his own design. Though it appeared at an early stage of aëroplane development, it still remains one of the most efficient types of biplanes. It has been used enormously in France, and armoured Farmans play an important part in the great war that is proceeding.

Mr. Farman quickly realised that for maintaining lateral stability the vertical planes fitted between the main planes of the Voisin type were a very poor substitute for the wing-warping method of the brothers Wright. He, however, produced the movement of the main surfaces in an original manner. He hinged small flaps to the rear extremities of the main planes. These he called “ailerons.” They produce much the same effect as the wing-warping method of the brothers Wright. When the biplane tilted sideways, the flaps were drawn down on the side that was depressed. The pressure of the air on the flaps forced the aëroplane back on an even keel. In the normal condition the flaps flew out straight in the wind on a level with the main planes. Another noticeable feature of Mr. Farman’s machine was the production of the first light and efficient landing chassis. This was a combination of wooden skids and bicycle wheels. Below the biplane, on wooden uprights, he fitted two long wooden skids. On either side of each skid he placed two little pneumatic tyred bicycle wheels, connected by a short axle. These were held in position on the skid by stout rubber bands passing over the axle.

In a general way the wheels raised the skids from the ground, but if the ascent was abrupt the wheels were forced against the rubber bands and the skids came in contact with the ground. With the abatement of the force of the shock the wheels came again into play.

Simplification of the chassis is becoming evident in the latest forms of all military aëroplanes, the reduction of weight in this portion of the apparatus being important.

To Mr. Farman belongs the credit of having first applied to his aëroplane the now famous Gnome motor, in which seven or more cylinders revolve. It can truly be said that the influence of this motor on facilitating flight generally, and very particularly military aviation, has been nothing short of prodigious. The aëroplane, like the airship, had to wait for the light petroleum motor. Its advent made flight possible, but achievement in flight would have been comparatively small had it not been for the welcome appearance of a motor specially adapted to the purpose.

The early forms of aëroplane engines in which the cylinders were fixed had proved to be quite unreliable owing to the high speeds at which the engines had to work. Overheating, loss of power, and stopping were frequent occurrences. The water-cooling and air-cooling systems introduced were equally inefficient. The very fact that the cylinders of the Gnome motor revolved effected the desideratum of automatic cooling, and also gave a smooth, even thrust to the propeller.

If the aëroplanes in the present war were flying over the enemy’s lines with old-fashioned engines, they would be dropping down into hostile hands as quickly as dying flies from the ceiling on the first winter days.

After the introduction of the Gnome motor, it was quickly realised that the speeds secured by its use gave the aëroplane a stability that was absent in the more slowly moving machines. Winds that were the bugbear of the aëroplanists could then be combated, and the aëroplane ceased to be the fine-weather machine. Heights could then be climbed that a little while before were undreamt of. It is said that there are some disadvantages in the case of revolving cylinders—that they have been known to produce a gyroscopic effect that has upset the machine. This, however, is a somewhat doubtful point. It may be urged that the greater silence of motors with fixed cylinders is an advantage in war. This may sometimes be so, and it is quite possible that for offensive aëroplanes a special type of motor may be in the future evolved.

To return to the other features of the Farman machine. The plan he adopted in his racing machines of making the upper plane larger than the lower one was a valuable step in speed-producing machines.

The records won by Mr. Farman with his machines alone testify to its efficiency. Often he has held the world’s records of distance, duration, and height, wrestling, indeed, for these with the Blériot monoplane.

In 1911 Mr. Farman began to make types of biplanes specially designed for military use, and in which he studied how he could best give the observing officer an unobstructed view of the ground beneath him. He placed both pilot and observer in seats projecting in front of the main planes. He also made a new departure in placing his upper plane in advance of the lower one. He claimed that this facilitates climbing and descent. He has, however, quite lately evolved a newer type of scouting machine.

In this the lower plane is only one-third the span of the upper one. The nacelle is not mounted on the lower plane, as in the ordinary types of his machine, but, instead, strung from the main spars of the top one. The usual chassis is absent. There is a single running wheel mounted at each end of the lower plane, which is brought very close to the ground. The upper and lower planes are separated by four pairs of struts. The tail is similar to that used on the ordinary type.

The following are the dimensions of one of the latest 1914 types of one-seated Farman machines:—

The following are the details of one of his high-power hydroplanes (1914):—

[Topical Press.

A BLÉRIOT MONOPLANE IN FLIGHT,

showing one of the two wings attached to the tubular body of machine, chassis, stabilising plane, and rudder at rear.

The Blériot Monoplane.