THE CONQUEST OF THE AIR SB ii Bg THE CONQUEST OF THE AIR AERONAUTICS AVIATION HISTORY : THEORY : PRACTICE BY ALPHONSE BERGET DOCTEUR fis SCIENCES. PROPESSEUR A I/INSTITUT OCEANOGRAPHIQUE PAST PRESIDENT LA SOCIETE FRANCHISE DE NAVIGATION AERIENNE WITH 83 EXPLANATORY DIAGRAMS AND 48 PLATES (NEW AND REVISED EDITION) NEW YORK : G. P. PUTNAM'S SONS LONDON: WILLIAM HEINEMANN 1911 PRINTED IN ENGLAND All riff Ms reserved DEDICATED TO PROFESSOR SILVANUS P. THOMPSON, D.Sc., F.R.S. PRINCIPAL OF THE CITY AND GUILDS TECHNICAL COLLEGE; PAST PRESIDENT OF THE INSTITUTION OF ELECTRICAL ENGINEERS 249480 At this moment no one can foresee the influence of Aviation upon the habits of mankind PREFACE TO THE FIRST ENGLISH EDITION THE year 1908 was one of experiment in aerial navigation; 1909 was the year of brilliant achievement. In 1908 the magnificent experiments of the Wright Brothers excited widespread admiration to a supreme degree. In October of the same year two daring aviators, Farman and Bleriot, abandoned their experimenting grounds and set out boldly into the realm of practice. On October 30 Farman accomplished the first "aerial voyage," by travelling from Chalons to Rheims, passing over villages, forests, and hills. The following day Bleriot achieved the first "cross-country" journey in a closed circle between Toury and Artenay, making two descents en route, and restarting under his own effort, with- out any launching apparatus, finally returning to his starting- point. The "Conquest of the Air," commenced in 1885 by the first dirigible, La France, built by Colonel Renard, is asserted to-day in the new development aviation. But now, in 1909, our human birds have excelled. By a remarkable flight, on July 25, Bleriot, more fortunate than his rival, Latham, who came to grief off his destination, succeeded in crossing the Channel, thus realising through the atmosphere that entente cordiale made between two nations. During August, on the plain of Bethany, near Rheims, in the first " aviation meeting " that had been held, all previous records were beaten. Paulhan, upon a biplane built by Voisin, covered 131 kilometres ; Latham, on an Antoinette monoplane, traversed 154*500 kilo- metres without a stop ; and Henri Farman, in a triumphant Vll viii PREFACE TO FIRST ENGLISH EDITION continuous flight, ultimately completed 180 kilometres in 3 hours 4 minutes 56 seconds. In addition to these mar- vellous exploits, Hubert Latham, striving to secure the victory for height, rose to 156 metres; and Curtiss, the American, won the speed trophy by travelling 30 kilometres in 21 minutes 15 seconds that is to say, flew at 75 kilometres per hour. If one recalls the fact that it was during the self-same year, 1909, that two most remarkable voyages were accomplished by dirigible balloons, which have definitely asserted the possibility of their practical application, one will understand that the highway of the atmosphere is now open, and that the " Conquest of the Air " has become an accomplished fact. Therefore the moment is opportune to explain how this conquest has been effected, to describe the principles of the construction and control of aerial vessels, dirigible balloons, and aviation apparatus. That is my reason for writing this book. I have written it as lucidly as possible, so that it can be read by all. It has no pretensions to being an " aeronautical encyclopaedia," but is rather an " introduction to the study of aeronautics," so that those who read and understand may be able to follow accordingly to advantage the whole progress of the new science as it develops and is described in the Press and the technical treatises. Thus I hope to have contributed to the diffusion of an interest in the science of the air in the same manner as I hope to have rendered a worthy appreciative tribute to the names of those who were, and are, the victors. ALPHONSE BERGET PROFESSOR A L'lNSTITUT OCilANOGRAPHIQUE DE PARIS PAST PRESIDENT OF THE SOCIETY FRANyAISE DE NAVIGATION AtRIENNE PARIS, August 31, 1909 PREFACE TO THE SECOND ENGLISH EDITION SINCE the first edition of this volume was published eighteen months ago how much has been achieved ! What triumphs have been recorded ! What striking progress has been accom- plished in aerial navigation ! During this time aeroplanes have made voyages in the fullest sense of the word. No longer are such of exceptional moment, and no longer is there necessity to select favourable days and routes. Flights can be made now over fixed courses, and on predetermined dates, as " Le Circuit de TEst " and the French Military Manoeuvres at Picardy demonstrated con- clusively. Several officers crossed France through the air from Paris to Pau; Chavez rose nearly to 3000 metres to cross the Alps over the Simplon ; Renaux journeyed from Paris to the Puy-de-D6me ; Sommer flew on his aeroplane accompanied by twelve passengers ; and the speed of 106 kilometres has been attained. If the fact is recalled that but ten years ago an attractive prize was offered for a flight over one kilometre it is possible to realise what tremendous strides have been made, and how quickly progress has been effected. And what about dirigibles? Two huge airships built in France crossed the Channel to this country, to be commis- sioned in the British military service. Wireless telegraphy is installed on these magnificent aerial craft, and this, too, is being perfected more and more every day. x PREFACE TO THE SECOND EDITION Therefore, we may be proud justly of the progress accom- plished and be full of hope for the future. The sympathetic reception accorded by English readers to the first edition of "The Conquest of the Air" has impressed me deeply, and I take this opportunity to extend them my heartfelt thanks. I trust that the second edition may meet with a success equal to that of the first edition. ALPHONSE BERGET, PROFESSOR A L'lNSTITUT OCEANOGRAPHIQUE, DELEGUE PLENIPOTENTIARE A LA CONFERENCE INTERNATIONAL DK NAVIGATION AERIENNE PARIS, March 26, 1911 CONTENTS INTRODUCTION xix PART I DIRIGIBLE BALLOONS CHAPTER I : PRINCIPLES The principle of Archimedes. How does a dirigible balloon rise ? : the ascending effort. The balloon envelope, rigging, and car. It is only possible to steer a balloon by the aid of a motor. Weight per horse-power, and per horse-power hour. Marine and aerial navigation: the dirigible, the steamship, and the submarine Pp. 19 CHAPTER II : THE RESISTANCE OF THE AIR The shape of dirigible balloons : spindle, fish, and cylinder. Result of air resistance: advantage of balloons of large capacity, strength, and speed. The " Radius of Action " of an airship. Conditions of equilibrium of dirigibles. The air ballonnet : rigid Balloons. Altitude stability: elevators. Stability of direction: longitudinal stability. Realisation of dynamic equilibrium : critical speed : the u empennage." Point of application of the propelling force : " deviation " Pp. 10-34 CHAPTER III : THE WIND AND DIRIGIBLE BALLOONS What is wind? Wind and the Aeronaut. Independent speed and wind velocity : the approachable angle. Present conditions of dirigibility in relation to the wind Pp. 6545 xii CONTENTS CHAPTER IV : CONSTRUCTION AND MANAGEMENT OF A DIRIGIBLE BALLOON The envelope and its outline. Construction of the envelope : the gas. The car, rudder, elevator, and motor. The screw, "slip," dimensions, and position. Handling the airship: starting out : en route : the descent. Voyages of the " Clement- Bayard" " Aerial Yachts." Impressions in a dirigible : dizziness: safety Pp. 4664 CHAPTER V : HISTORY AND DESCRIPTION OF THE PRINCIPAL DIRIGIBLES The pioneer: General Meusnier, inventor of the aerial pro- peller. The Jirst motor balloon: Giffard^s airship (1852). Dupuy de Lome^s dirigible (1872). Dirigible balloon of the brothers Tissandier (1883). Captains Renard and Krebs 1 balloon "La France" (1884 and 1885). The era of the explosion motor : M. Henry Deutsch : M. Santo s-Dumontf s experiments. The " Lebaudy " balloon : " La Patrie." Bal- loons with hollow stabilisators : M. DeutscJis Ville-de-Paris : M. Clement's " Bayard. ' foreign dirigibles : Count Zeppelin's airships. Progress of military aeronautics in Germany : the three " Zeppelins" the " Parseval" the " Gross " airships : the grand manoeuvres at Cologne. English, Italian, and Belgian dirigibles. Comparison of different types of dirigibles : the " co-efficient of advantage." What are the improvements to be effected in airships ? Pp. 6596 PART II AVIATION APPARATUS CHAPTER I : THE PRINCIPLES OF AVIATION What is aviation ? How birds fly. The forerunner of the aeroplane : the " kite" Scientific kites : Military kites : kite ascents. Definition and elementary equilibrium of the aero- plane. Resistance of the air: angle of attack: centre of thrust Pp. 97-110 CONTENTS xiii CHAPTER II : APPLICATION OF THE GENERAL PRINCIPLES Shape and disposition of the wings. Monoplanes and biplanes. Lateral stability : turning. Practical means of preventing lateral incline : " ailerons" partitions, warping. Steering : the rudder and elevator. Launching the aeroplane. The descent Pp. 111-126 CHAPTER III : AEROPLANE CONSTRUCTION Carrying surfaces : the "power of penetration." Motors employed in aviation. The propeller : screws. The " body " of the aeroplane. Aeroplanes and speed : aeroplanes of the future. Wind and aeroplanes. Height at which it is advis- able to Jly : safety. Other forms of aviation : helicopters and ornithopters. Composite solution : soaring balloons : Capazza's lenticular Pp. 127-150 CHAPTER IV : DESCRIPTION OF SOME AEROPLANES. 1. BIPLANES The Voisin aeroplanes. The Wright Brothers'" aeroplane Maurice Farman's aeroplane : the Breguet biplane Pp. 151-167 CHAPTER V : DESCRIPTION OF SOME AEROPLANES. 2. MONOPLANES The BUriot aeroplane. The Esnault-Pelterie aeroplane. The " Antoinette " aeroplane. Santos-Dumonfs " Demoiselle " .- the Tellier aeroplane. The two schools of aviation. Helicopters and ornithopters : the Breguet gyroplane Pp. 168190 CHAPTER VI : EARLY DAYS OF AVIATION The forerunner : Sir George Cayley. The u human birds " : Lilienthal, Chanute, Captain Ferber, the Brothers Wright. Exploits of the French aviators: Santos-Dumont, Voisin, Delagrange, fyc. The Mcecene: Henry Deutsch, E. Arch- deacon, Armengaud : the two historical aviation voyages by Farman (October 30), and Bleriot (October 31, 1908), who accomplished the two Jirst " aerial journeys " from town to xiv CONTENTS town. The latest achievements of the aviators Latham, Rougier, Count Lambert, Paulhan, Dubonnet, fyc. : Bleriofs flight across the Channel : Paulhan's flight over England : the crossing of the Alps by Chavez. The enthusiastic public movement in favour of aerial navigation : " aviation meetings." The martyrs of aerial navigation : dirigible catastrophes : aero- plane disasters Pp. 191-212 CHAPTER VII : THE FUTURE OF AERIAL NAVIGATION Dirigibles or aeroplanes. Military applications. Applications to civil life. Scientific applications : exploration of unknown countries. The industrial movement created by aerial naviga- tion. What remains to be done? Pp. 213-234 APPENDIX Pp. 235-237 GLOSSARY OF AERONAUTICAL TERMS Pp. 238-240 METRICAL MEASUREMENTS WITH ENGLISH EQUIVALENTS P. 241 INDEX Pp. 243-249 ERRATA. PLATE xiii should read The "GROSS" SEMI-FIGID AIRSHIP. xiv should read The "PARSEVAL" FLEXIBLE AIRSHIP WITH TWO COMPENSATING BALLONETS. ILLUSTRATIONS PLATES FACING PLATE PAGE I. The first circular flight by dirigible made twenty-five years ago. " La France " passing over Paris, September 25, 1885 Frontispiece II. The first round journey by a " heavier than air " machine. The flight of the " Bleriot " aeroplane from Toury to Artenay and back with intermediate descents, October 31, 1908 frontispiece III. The dirigible balloon "Republique" 10 IV. The " Ville-de-Paris in its shed 11 V. The dirigible " Bayard- Clement No. 1" 20 VI. The " Bayard-Clement " entering its shed, showing the pneumatic empennage 21 VII. Car of the " Bayard -Clement No. 1 " 30 VIII. Fore part of the car of the " Bayard-Clement No. 1 " 31 IX. The dirigible " Patrie " from below 40 X. The car of the " Republique " 41 XI, The first German dirigible " Zeppelin '* manoauvring above lake Constance 46 XII. The stern of the " Zeppelin " 47 XIII. The " ParsevaT' flexible airship with two compensating ballonets 52 XIV. The " Gross " semi-rigid airship . 53 XV. The car of the " Parseval " 62 XVI. " A German reserve 63 XVII. " Clement-Bayard No. 2 " 70 XVIII. The " Clement-Bayard No. 2 " landing 71 XIX. The first Italian military dirigible manoeuvring over Bracciano 90 xv xvi ILLUSTRATIONS FACING PLATE PAGE XX. The new Italian dirigible " I-Bis " 91 XXI. The Joanneton airship speed recorder; the Gnome light motor ; the Esnault-Pelterie light motor ; a 100 H.P. Antoinette aviation motor 98 XXII. Bridge showing steering and control mechanism of " Bayard-Clement No. 1 " 99 XXIII. A " Santos-Dumont " dirigible ; an accident ; the little " Santos-Dumont " aeroplane 106 XXIV, The " Santos-Dumont " aeroplane winning the Deutsch prize ; a " Santos-Dumont " monoplane ; Santos-Dumont's " Demoiselle " 107 XXV. A pioneer. The German experimenter, Otto Lilienthal, making a glide 120 XXVI. M. Ader's " Avion," the first aviation apparatus to rise into the air ; the " Avion " with wings folded ; Wright making an aerial glide 121 XXVII. The first attempts in aviation 130 XXVIII. " An early bird '' : the Gastambide-Mangin monoplane in full flight XXIX, Henry Farman's flight from Chalons to Rheims XXX. Henry Farman at the wheel of his first aeroplane XXXI. The Wright aeroplane emerging from its shed at Auvours camp XXXII. The Wright aeroplane at the moment of launching by the fall of a weight in the derrick ; the Wright aeroplane in full flight; Wilbur Wright at the wheel of his aeroplane, showing the two control levers XXXIII. The Cornu helicopter XXXIV. The Br6guet gyroplane ; the de la Hault ornithopter ; the propellers of the Leger helicopter ; the Leger helicopter showing the motor and controlling mechanism XXXV. Henry Farman's new biplane XXVI. The latest Voisin biplane, wit at the wheel XXXVII. The 1910 " Bleriot " monoplane from below XXXVI. The latest Voisin biplane, with the aviator Bielovucie at the wheel ILLUSTRATIONS xvii FACING PLATE PAGE XXXVIII. The 1910 " Antoinette " monoplane, mounted by Latham 183 XXXIX. Henry Farman, carrying two passengers, on his bi- plane created records for duration and distance of flight 194 XL. How passengers are accommodated on an aeroplane 195 XLI. Rougier flying over Cap Martin (Monaco 1910) ; Latham upon his " Antoinette " and Martinet upon his " Farman " 202 XLI I. Morane on a " Bleriot," Latham at the wheel of an " Antoinette," and below, Bouvier on his " Sommer" rounding the mark 203 XLIII. A start : Lindpainter leaving Issy-les-Moulineaux for the " Circuit de Test " 210 XLIV. A descent: the crowd rushing towards Latham's aeroplane upon alighting 211 XLV. French mitrailleuse, showing soldier training weapon upon aeroplane ; French gun for use against aerial craft at the Picardy manoeuvres 222 XLVI. The German military automobile gun, built by Krupp for fighting aerial craft 223 XLVII. The " Bayard-Clement No. 2 " manoeuvring above the troops at the French manoeuvres, with Latham preparing to set out on his " Antoinette " monoplane 230 XLVIII. The Arc de Triomphe de PEtoile, as seen from a height of 300 metres 231 Also many explanatory diagrams in the text INTRODUCTION AERONAUTICS is the art of sustaining and directing oneself in the atmosphere, without coming into contact with the earth or the water on its surface. The solution of this problem has been sought for ages by man, ambitious to imitate the birds. It was solved partially in 1783, when the Brothers Montgolfier, for the first time, succeeded in raising and sustaining in the air a heavy body capable of carrying passengers. This discovery, the principle of which differs from that governing the flight of birds, was of the utmost importance. It had the merit, not only of showing that the atmosphere was far from being a realm sternly forbidden to man, but also, by providing him with the means for sustentation therein, allowing him to hope that some day he might be able to steer his course wherever he desired. But Montgolfier's invention did not constitute aerial navigation. The " aerostat," appropriately christened, was passive in the midst of the atmosphere. It was to the airship of man's dreams what the buoy is to the ship, that is, a floating object, the toy of the fluid in which it floats. Three- quarters of a century passed in vain attempts to steer these craffc until the Frenchman Giffard first showed by a conclusive experiment the feasibility of deviating balloons, a possibility which was achieved triumphantly by Colonel Renard twenty- five years ago in 1884. Therefore, a balloon floating in the air by virtue of the principle formulated by Archimedes, because its weight is less XIX xx INTRODUCTION than that of the air it displaces, can now be steered success- fully. This first solution of aerial navigation had the merit of distinct novelty. Nature has nothing comparable to show us. It differs as much from the flight of birds as the move- ment of a railway train is opposed to that of the most agile of our quadrupeds. But the bird's example persistently incited the human brain to seek a further solution. The problem was to rise into the air mechanically, without the cumbersome intermediary of a volume of light gas enclosed in an impermeable envelope in a word, to navigate the air in the manner of the bird with an apparatus heavier than air. The first essays were made a long time ago, but it was not until 1895 that the solution already presaged assumed tangibility. Now at last aerial navigation without an aerostat, mechanical sustentation, aviation, in short, is an accomplished fact; its practical application is merely a question of minor improve- ments. Thus there are two quite distinct forms of aerial navigation by dirigible balloon and aviation respectively. This affords us a natural division for this book, in the first part of which we shall deal with dirigible balloons. PART I DIRIGIBLE BALLOONS CHAPTER I PRINCIPLES HOW THE AERIAL VESSEL FLOATS AND MOVES I WHY DIRIGIBILITY MUST DEPEND ON A MOTOR AND A PRO- PELLER : A COMPARISON BETWEEN MARINE AND AERIAL NAVIGATION THE PRINCIPLE OF ARCHIMEDES A DIRIGIBLE balloon is an apparatus which is supported in the air by making use of the pressure exercised by this on all bodies plunged therein. By the aid of a propeller revolved by a motor, it can and must move in this element at the will of the aeronaut. I can explain the fundamental principle of aerostatics in a very few words. It was discovered by Archimedes, and formulated as follows : Every "body plunged into a fluid is subjected ty this fluid to a " pressure " from below to above, which is equal to the weight of the fluid displaced ly that body. It is by virtue of this principle that ships float on, and fish swim in, water. When a body, the exterior volume of which is a cubic metre, is plunged into water, this body displaces a cubic metre of water, or, in other words, 1000 litres. Now 1000 litres of water weigh 1000 kilogrammes. Three possi- bilities may then arise : the weight of the body immersed may be less than 1000 kilogrammes, when it will rise and float on the surface; or it may be exactly 1000 kilogrammes, in which case it will remain in equilibrium in the water at a 2/ THE CONQUEST OF THE AIR certain level; or, finally, it may weigh more than 1000 kilogrammes, and then it will sink to the bottom. These three factors are realised by fish, which at will are able to rise to the surface, to suspend themselves in the water, and to sink to the bottom. To carry out these distinct move- ments they vary their specific gravity by the help of their natatory gland, a bag containing air which they can dilate or compress as they please. We shall see later, in dealing with dirigible balloons, a similar organ in the " air-ballonnet." HOW DOES A DIRIGIBLE BALLOON RISE? THE ASCENDING EFFORT The principle being laid down, we may make use thereof to raise an object into the atmosphere; we have only to produce a body, the total weight of which shall be less than that of the volume of air it displaces. Now the weight of the air is known : a cubic metre thereof weighs 1*293 kilogrammes, that is to say, about 1300 grammes, when the temperature is at zero and the barometer indicates 760 millimetres. On the other hand, there are " light " gases, such as coal gas and hydrogen. A cubic metre of the former at zero, weighs about 500 grammes, while a cubic metre of hydrogen, under the same conditions, weighs only 110 grammes. Let us take this latter, the most suitable for the object we have in view. Let us make a huge vessel of some flexible and impermeable material a "balloon" and let us fill this "envelope" with hydrogen gas. Let us suppose that the interior volume of this receptacle is 1000 cubic metres ; when filled with hydrogen it will weig;h 110 kilogrammes; but the 1000 cubic metres of air that it will displace will weigh 1293 kilogrammes. The difference, i.e., 1183 kilogrammes, will be the vertical upward pressure exercised on the vessel according to Archimedes' principle. The envelope by being inflated with hydrogen therefore will be capable of lifting 1183 kilogrammes; that is to say, 1 kilogramme 183 grammes per cubic metre. A balloon thus constructed is called an aerostat. The point where the pressure which supports it is exerted is called the PRINCIPLES 8 centre of pressure, and its position coincides more or less with that of the centre of gravity of the inflated envelope. If, then, the weight of the envelope itself, plus the weight of a support to carry the motor and propeller, and the weight of the aeronauts does not exceed 1180 kilogrammes, the apparatus will rise. This difference between the vessel's weight and its lifting power is called its ascensional effort. If the total weight of the envelope and of the system it supports exceeds 1180 kilogrammes, the apparatus will remain on the ground. If, instead of inflating our envelope with hydrogen, we had used coal gas, it would only have been able to raise 690 kilogrammes instead of 1180 ; obviously therefore, there is an advantage in using hydrogen. The very existence of the ascensional effort produced by the pressure of the surrounding air provides the aeronaut with simple means to make his balloon rise or sink at will. If he wishes to rise, he has only to throw out of his car a portion of the weight it contains ; ballast, in the form of bags of sand, is always carried for this purpose. If, on the other hand, he wishes to descend, he has only to diminish the ascensional effort of the aerostat. This is done by allowing a certain quantity of the light gas it contains to escape through a valve, which can be opened and closed at will. The difference between the weight of the air and the weight of the gas is then diminished ; that is to say, the pressure is reduced and the balloon descends. THE BALLOON ENVELOPE, RIGGING AND CAR The essential device for sustaining the balloon in the air is therefore the envelope, which we shall inflate with a light gas ; it must further fulfil the conditions of lightness, strength, and impermeability. It must be light, because its weight forms part of the total weight the balloon must lift, and which must be deducted from the load which the apparatus will be able to carry. It must be strong, for it will have to withstand the strain from the gas with which it is filled, and also the stresses exercised on its various parts by the weight of the objects and passengers 4 THE CONQUEST OF THE AIR on the one, and by the shocks and vibrations of the motor on the other, hand. It must be impermeable, that is to say, must not allow the gas it contains to ooze through its pores, for it is this gas which, owing to its lightness, enables the balloon to rise into the air, and if any portion thereof were to escape, the ascensional effort would be diminished at once. The material now used almost exclusively for the con- struction of dirigible balloons is a composite fabric, consisting of two layers of cotton, between which is inserted a thin layer of india-rubber, the tenth of a millimetre in thickness. This material is unvarnished. It weighs 300 grammes per square metre; can withstand a strain of 1250 grammes per metre; and has an equal power of resistance in the direction of warp and woof. The manufacture of this material is carried on in France and Germany ; it has become a regular off-shoot of the rubber industry. Light as our envelope is, it has, nevertheless, an appreciable weight, to which we must add that of the " rigging " i.e., the suspension ropes by which the aerostat supports the car, that light, yet solid, receptacle which contains the motor and the pas- sengers, and which also carries the propeller ; the mechanism which utilises the resistance of the air to drive the dirigible balloon forward. We may note in passing that an aerostat furnished with a motor is generally called an " airship." IT IS ONLY POSSIBLE TO STEER A BALLOON BY THE AID OF A MOTOR Why was it so long before it was possible to steer a balloon when, so far back as 1783, man, applying the principle formu- lated by Archimedes, had been able to lift himself into the air ? It was not, indeed, until 1884 that the first circular flight was accomplished by Colonel Renard with a balloon which after all deserved the title of dirigible. Why was this ? Because, before it is possible to " steer " a body floating in a fluid, it is absolutely essential that this body should possess an independent speed to permit it to move in this fluid of its own accord. I can illustrate this point by a very simple and familiar comparison. PRINCIPLES 5 Let us take a boat which has a rudder at the stern and is propelled by a pair of oars. A rower, manipulating these, imparts a certain speed to the boat. So long as this speed is appreciable, the rudder acts efficiently, and the steersman only has to move it to the right or to the left to alter the course of the vessel. But let the rower rest on his oars, and the boat, deprived of speed, will float "like a buoy," and it will be useless for the helmsman to work the rudder, because the latter will have no effect upon the boat, which will be the sport of the water on which it floats. Thus in order to steer the boat, we must propel it. In the same way we must "propel" an aerostat if we want to " steer " it. But to propel it we must have a motor, and any motor is necessarily heavy. Let us now inquire into the respective weights of the motors it would be possible to use. In the first place, there is the " human motor," that is to say, the muscular energy of the aeronauts in the car. It is hardly necessary to say that this was the first motor to be taken into account in the earliest days of aerostation, for there was none other known at that period. But though such a dream was then possible, it is so no longer, for to-day we have more precise data resulting from mechanical experiments which have established the weight -conditions of each class of motors. The practical unit of energy is steam horse-power, that is to say, a force capable of raising 75 kilogrammes one metre from the ground in one second. This power is very much greater than that of the animal horse. A man represents but a fraction thereof. Now mechanicians have established by experiment, independently of all theory, that the weight of the steam horse-power translated into human muscular power, is about 1000 kilogrammes; in other words, it takes 1000 kilo- grammes of men to produce an effort equal to that of the steam horse ! Therefore it was futile, obviously, to attempt to steer balloons by utilising the muscular power of the few aeronauts who controlled them . In the early days of steam power, motors were of consider- able weight. The engine of the Sphinx, the first steamship in 6 THE CONQUEST OF THE AIR the French Navy, weighed more than 1000 kilogrammes per horse-power, and even thirty years ago steam motors weighed some 100 kilogrammes per horse-power. Hence the first steam engines were no more suitable for the propulsion of aerostats than human effort, to say nothing of the danger of installing a boiler heated by coal beneath an envelope inflated with hydrogen, an eminently inflammable gas. Nevertheless, steam was the power used with the first motor for a balloon. Its application was essayed in 1852 by the engineer, Henry Giffard. Instead of using the steam motors already in existence, he had built one of three horse- power expressly for his experiment; he succeeded in re- ducing the weight per horse-power to 53 kilogrammes; this was a remarkable achievement at the time and an enterprise of extraordinary audacity, taking its dangers into account. But the steam engine was abandoned very soon, owing to the risk of fire, and aeronauts adopted the electric motor, which, from 1880, was regarded as the aeronautical motor of the future. Colonel Renard succeeded in obtaining an electric motor of 8 horse-power, weighing only 40 kilogrammes per horse-power, and capable of great endurance ; this rendered real aerial navigation a possibility, which he had the honour to accomplish first in 1885. But about 1890 a new engine made its appearance; rude and clumsy at first, it was improved and perfected very soon. Thanks to this invention, a new industry was born the automobile which has revolutionised all our habits. The engine was the " explosion motor." Power for power, the explosion motor is the lightest known prime mover. To-day mechanicians have succeeded in per- fecting motors especially designed for aviation of the almost incredible weight of 2 kilogrammes per horse-power. Moreover, its action has been perfected ; it can start in an instant without preliminary preparation. The volume has been reduced pro- portionately to the weight, so the engine is not cumbersome. It is due to this development that aeronautics have become what we see, and that aviation has been made possible in its turn. The explosion motor is the only one now used in aerial navigation. PRINCIPLES 7 WEIGHT PER HORSE-POWER, AND PER HORSE-POWER HOUR If we consider a machine able to yield 100 horse-power for a weight of 1000 kilogrammes, we say that the " weight per horse-power "is 10 kilogrammes. But such data is insufficient for the aeronaut in working out his constructional designs. We have not only to lift our vessel, but to use it, to make it travel, and for this purpose we require a combustible, which in our particular case is petrol. Then we must have water to cool the motor, oil to grease its mechanism, and other accessories necessary for its operation. In a word, if our 100 horse-power engine consumes 1 kilogramme of various materials per horse-power, it will use 100 kilogrammes of provisions per hour. If we want to make it go for ten hours, it will require 1000 kilogrammes of necessaries, the weight of which must be added to that of the machine itself. Thus, in the example we have taken, we shall have 1000 kilogrammes, the net weight of the engine, and 1000 kilo- grammes of fuel &c., to enable it to run for ten hours, making a total of 2000 kilogrammes. But for these 2000 kilo- grammes we shall get 100 horse-power for ten hours that is, 1000 horse-power hours. The weight per horse-power hour is, obtained therefore, by dividing 2000 by 1000; which represents 2 kilogrammes. It is essential that we should not confound these two terms ; the weight per horse-power hour depends on a proper use of the combustible by the engine, whereas the weight per horse- power depends solely on the construction of the engine. As Colonel Renard pointed out, it is possible to have the same number of kilogrammes for the weight per horse-power hour with a light engine that consumes a great deal, as with a heavy engine that consumes very little ; but with too heavy an engine the balloon perhaps would not rise at all; and the first duty of a balloon, even of a dirigible, is to rise into the air : primum mvere, deinde philosophari, said the philo- sophers. To conclude what we have been saying, we may lay down this principle : the motor above all things, should be as light 8 THE CONQUEST OF THE AIR as possible ; that is to say, the point of primary importance is to keep down the weight per horse-power. As to the diminution of the horse-power hour, this would merely enable us to prolong the duration of the voyage, or, to use a phrase proper to naval warfare, to extend the " radius of action " of the airship. MARINE AND AERIAL NAVIGATION : THE DIRIGIBLE, THE STEAMSHIP, AND THE SUBMARINE The airship has been compared often to the steamship ; the aerial ocean to the marine ocean. Is this a legitimate comparison ? We will examine this question briefly. First we must note the essential and absolute difference between an airship and a steamboat. The latter floats upon an element of great density, the water, in which its propellers find an appreciable fulcrum, by virtue of its great resistance : but a part of its hull is submerged, and it is upon this portion only that [the resistance which the surrounding liquid offers to the advance of the vessel is exercised. The balloon, on the other hand, is immersed completely in the liquid wherein it is sustained by the vertical thrust. The latter varies constantly owing to the weight of a gas, the thermal ex- pansion of which is very great, fluctuating in accordance with the slightest vicissitudes of temperature or of barometric pressure, whereas the " hydrostatic pressure " which causes the ship to float upon the water does not vary appreciably when the temperature changes. But no floating vehicle, be it balloon or vessel, is ever required to float in a perfectly immobile element. The ocean is agitated by marine currents such as the Gulf Stream, which circulates across the Atlantic, or the tidal currents at certain places around our coasts. On the other hand, the atmosphere is in perpetual motion under the action of the " winds," which are aerial currents. But there is a striking difference between these two kinds of currents. Whereas the most rapid of marine currents, such as the Raz de Sein on the Brittany coast and the Raz Blanchard do not exceed a speed of 9 knots (16'500 km. per hour), the aerial currents have often very PRINCIPLES 9 considerable velocities. Directly the wind "freshens," as sailors say, its speed is increased very soon from 10 to 15 metres a second, that is, from 36 to 56 kilometres an hour. A steamship driven at high speed in the most modern types 20, 25, and even 30 knots will overcome the ocean currents very soon, the speed of which need only be deducted from that of the ship ; whereas the dirigible balloons are compelled to struggle against currents of air the violence of which condemn it to immobility or to retreat. In short, the ship and the dirigible balloon are not com- parable. The only exact parallel of this kind which we could draw is that of the airship and the submarine, which also is immersed completely in its supporting fluid. Still the advantage is on the side of the submarine, which never has to overcome the rapid currents with which its aerial counterpart has to contend. A juster comparison might be made between a dirigible balloon and a submarine which has to advance, not against a current, but against a torrent. We can now see how difficult a problem is the propulsion and steering of aerostats and we can understand why it has taken a century to discover how to guide the machine which the brothers Montgolfier launched into the air for the first time in 1783. CHAPTER II THE RESISTANCE OF THE AIR OBSTACLES OPPOSED TO THE ADVANCE OF THE AIR- SHIP: THE MOST ADVANTAGEOUS CONDITIONS OF SHAPE AND DIMENSIONS FOR THE ENVELOPE: INDE- FORMABILITY: THE EQUILIBRIUM AND STABILITY OF AIRSHIPS THE RESISTANCE OF THE AIR THEREFORE we are going to take an aerostat, and provide it with a motor to give it an " independent speed " which will ensure its propulsion, and consequently, its direction. But when we thus propel our aerostat, it will experience a resistance to its forward movement from the surrounding atmosphere. Whenever we attempt to displace a body of any kind in a material fluid for instance, if we try to move a board which we hold in our hand in the water we feel a resistance to the movement we are trying to produce. This resistance does not depend upon the volume or the total mass of the body displaced, for we feel that it varies according as to whether we hold the board flat or edgewise. We also note that the resistance is greater, if, all other conditions being equal, we try to move it faster. Physicists on the one, and engineers on the other, hand, have attempted to establish the laws of this " air-resistance " both by calculation and experiment. They have arrived at the following conclusion, which is correct in the main, but merely approximate if we demand precision : " the resistance offered by the air to a surface element which is moving on a line perpendicular to its plane is proportional to the extent of this surface, to the square of the speed which animates it, and to a numerical co-efficient, the mean value of which is 10 THE RESISTANCE OF THE AIR 11 0*125. Thus if the surface of the moving element is measured in square metres, and if the speed is expressed in metres per second, the result represents the resistance in kilogrammes (Fig. I). 1 For instance, let us consider a board, having a superficies of 4 square metres moving normally to its plane at a speed of 10 metres per second; the re- sistance, in kilogrammes, will be obtained by multiplying the area, 4, by the square of the speed, that is to say by 10 X 10, or 100, and by multiplying the sum by the co-efficient 0'125 (4 x 100 x *0'125 = 50 kilo- grammes). If the speed of move- ment be doubled, the resistance of the air will be quadrupled ; it would become nine times greater if the resistance were tripled and so on. When the moving body is faced with a " prow," that is, a surface having tapering sides, which separate the molecules of FlG. 1. Resistance of the air upon a surface moving normally (Angle of cone : 25") FlG. 2. Influence of front shape The two models shown in the illustration, and travelling from left to right, are fitted with a " prow" one spherical, and the other conical, to force aside the masses of air more easily. air without striking them sharply as would a flat surface, the resistance is diminished. Thus, if we take the panel of Fig. 1, but cause it to be shaped so as to divide and thrust aside the molecules of air, as would be the case if we made use of the hemisphere or the cone (Fig. 2) with the base of the same superficies as the panel, the resistance of the air to the speed * The reader who wishes to know the formula of the resistance of the air, is referred to the Appendix to this book. 12 THE CONQUEST OF THE AIR of 10 metres per second, which, was 50 kilogrammes for the flat panel moving perpendicularly to its plane, will be but 25 kilogrammes for the hemisphere, and only 9 kilogrammes for the acute-angled cone. Experience has shown that not only is the shape of the " bow " of the moving body important, but so is that of its "stern," or "poop." The profile of the latter may permit either an easy reunion of the molecules of air separated by the prow which glide along the sides to rejoin each other, or, on the other hand, its abrupt formation may cause the molecules separated by the prow to re-unite tumultuously, clashing one with another and producing eddies behind the moving bodies. THE SHAPE OF DIRIGIBLE BALLOONS : SPINDLE, FISH, AND CYLINDER The points we have just considered determine the shape of the envelope for a dirigible balloon. There can be no question of attempting to propel a spheri- cal balloon. The surface on which the resistance of the air would be exercised during the advance would be enormous. With an equal volume of envelope, it is necessary to select lines that present as small a surface as possible to the air as it advances, while preserving the utmost lifting power. This condition is fulfilled by giving the envelope an elongated longitudinal shape. But what should be this elongated form ? Should it be that of a symmetrical spindle, an ovoid body, and in this event, should it advance with the larger or smaller end foremost? Or should it be cylindrical ? The first attempts, those of Giffard in 1852, of Dupuy de Lome in 1872, and of Tissandier in 1884, were made with " fusiform " (spindle-shaped) balloons ; in other words, their shape, equally pointed at either end, was symmetrical in re- lation to the central plan (Fig. 3). But all this was changed when that man of genius, indisputably the father of aerial navigation, appeared, Colonel Charles Renard, whose early death in 1905 was an irreparable loss to science and to France. Renard demonstrated by his calculations that the most advantageous lines are those of a dissymmetrical fish (B), with THE RESISTANCE OF THE AIR 13 the largest end at the front. So long ago as the beginning of the nineteenth century, Marey-Monge had presaged the necessity of adopting this form if an attempt should be made to propel aerostats : " They must have the head of a cod and the tail of a mackerel " was his dictum. This, indeed, is the shape of all birds and of all swiftly A Fusiform (Giffard, Santos-Dumcait) Fish -shaped (Renard, Lebaudy, Clement Bayard) Cylindrical (Zeppelin) FIG. 3. Different shapes of dirigibles moving fishes whales, cachalots, and porpoises. At present all dirigible balloons which have proved really capable of pro- gression are all con- structed on the lines worked out by Renard. We must now point out that if the conditions of progression and of the resistance of the air are to be normal, the balloon must preserve its shape during its course, either ascending or descending. We shall see later how this condition is fulfilled by the " air ballonnet." FIG. 4. Eddying action resulting from flat shape of stern The stern eddies produce a partial vacuum to which the travelling body strains to move, thus setting up a force opposed to the direction of travel, and which consequently retards for- ward movement. As to the cylindrical form (C), adopted in Ger- many by Count Zeppelin, it seems less advantageous. The molecules of air thrust apart by the point in front exercise an exaggerated friction on the sides before they re-unite, thus retarding the progress 14 THE CONQUEST OF THE AIR of the airship. The other German aeronauts therefore are returning gradually to the pisciform shape. In any case, the pointed stern is indispensable, for without it there would be an eddy of the molecules of air, and conse- quently a partial vacuum which would cause antagonistic thrust at the prow. This pressure, acting against the forward movement, would retard the speed of the airship (Fig. 4). Therefore it is necessary at all costs to avoid such by tapering the rear end of the balloon. RESULT OF AIR RESISTANCE : ADVANTAGE OF BALLOONS OF LARGE CAPACITY, STRENGTH AND SPEED The resistance of the air to the movement being propor- tionate to the square of the speed, leads us to a most im- portant conclusion. This is, that balloons of large size have an advantage over those of smaller dimensions. Let me explain. To start with a clear idea, let us consider an airship in the shape of an oblong box with a square base, the latter being, for instance, 1 metre wide and deep, by 5 metres long. Its volume will be five cubic metres, and its ascensional effort, taking this at 1 kilogramme per cubic metre, will be 5 kilo- grammes. This balloon, if inflated with hydrogen, will lift, in round numbers, a motor the power of which will be limited by this weight of 5 kilogrammes; and if we suppose that a motor weighing exactly 5 kilogrammes per horse-power has been constructed, the motor this balloon can lift will be of one horse-power. Having demonstrated this, let us construct a second airship, a replica of the first, also inflated with hydrogen, but with all the dimensions doubled ; that is to say, having a squared base of 2 metres, by a length of 10 metres instead of 5. The volume of this balloon will not be double that of the first, it will be 2x2x10 = 40 cubic metres; that is, eight times larger, while its surface of resistance to progression will be that of its base, i.e., 4 square metres. Thus, as we have doubled all the dimensions, the resistance of the air will be four times greater, whereas the volume, otherwise the lifting power, will be eight times as much. THE RESISTANCE OF THE AIR 15 Now, with an ascensional effort eight times greater, it will be possible to lift a motor eight times more powerful, and even more, because the weight per horse power diminishes in pro- portion as the power of the motor increases. Therefore, the balloon, the dimensions of which have been doubled will have a 8 horse-power motor at least to meet an air resistance bearing upon four square metres ; that is to say, two horse-power per square metre of the transverse section, whereas the balloon of half this size will have only a 1 horse-power per square metre of the section. The advantage is consequently all on the side of large balloons, and aeronauts who wish to undertake important journeys, and to carry large stores of fuel, and numerous passengers, will find it profitable to construct dirigible balloons of large dimensions, The largest dirigible balloon yet constructed for such a purpose is the Zeppelin, of 18,000 cubic metres, whilst the smallest is the Santos Dumont No. 1, which gauged but 180 cubic metres. True its only passenger, M. Santos Dumont, weighed only 52 kilogrammes, and that the whole car weighed but 10 kilogrammes! To sum up, we may say that the volume, on which the power of the motor that can be carried depends, varies according to the cubic dimensions of the airship, whereas its surface, on which the resistance offered by the air to its progress depends, varies only according to the square. Finally, it is necessary to point out that the power necessary to communicate increasing speeds to the same airship increases pro- portionately to the cube of the speed. This law has been demonstrated by calculation and verified by experience. It is of vital importance, for it leads to various conclusions of the utmost moment. Thus, to double the speed of a dirigible balloon, we must give it a motor power not twice, but eight times greater (8 is the cube of 2; 8 = 2x2x2). So if we take into consideration a modern dirigible, say the CUment Bayard, having a speed of 45 kilometres an hour from motors of 100 horse-power, in order to double that speed it would be necessary to fit the same airship with motors of 800 horse-power. It is a repetition of the naval constructor's wail speed costs money. We see therefore that great care is necessary in calculating 16 THE CONQUEST OF THE AIR the elements of a dirigible balloon, when it is destined to undertake journeys of any length. THE "RADIUS OF ACTION" OF AN AIRSHIP But a dirigible balloon must not be a mere object of scientific curiosity, or a vehicle of sport. It must have a useful application; it must be able to accomplish journeys. The longer the duration of the latter, the greater is the utility of the apparatus. Therefore it is necessary, first and foremost, to ensure long-sustained flight by the dirigible. Here the speed question plays a very important part, as does also that of the motor pojver it is necessary to apply to the airship to give it the desired speed. This power, as we have just seen, is proportional to the cube of the speed. And this must be taken into account if travelling velocity is not the sole desideratum, and if the total distance the aerial vessel can travel is also an important factor. Let us consider a balloon of 3000 cubic metres, travelling at the rate of 60 kilometres an hour, with two engines of 60 horse-power each. These motors consume a total quantity of 60 kilogrammes of petrol an hour. The balloon, carrying six passengers, can take 600 kilogrammes of petrol, which renders a ten-hour journey possible. If we take into con- sideration that it has to return to its starting-point, its pilot has only five hours' outward travel at his disposal, or, reckoning 60 kilometres to the hour, 300 kilometres. We should say under these conditions that the radius of action of this dirigible balloon is 300 kilometres. Let us now suppose that only one of the motors is working. The propelling power then will be only 6 horse-power ; the speed will be divided by the cube root of 2, that is, in round numbers, 1*25 ; it will therefore be 48 kilometres an hour. But the single motor does not consume more than 30 kilo- grammes of petrol, and there are 600 kilogrammes on board. Therefore the airship will have twenty hours of travel before it, instead of ten; that is, ten outward and ten return. Consequently it will be able to travel 10 times 48 kilometres and still have the means of returning to its starting-point. We should say therefore that under these altered conditions t the radius of action of the dirigible is 480 kilometres. THE RESISTANCE OF THE AIR 17 Thus, by demanding a speed of 48 kilometres only per hour instead of 60, we extend the radius of action of the same dirigible from 300 to 480 kilometres. Hence we have increased it very considerably. This shows us how important is the consideration of the radius of action, especially in the application of aerial naviga- tion to military or geographical operations. One thing should be clearly understood : speed is costly on an airship as it is on a transatlantic liner. To double it, the motor power must be multiplied by eight ; the balloon therefore must carry eight times more fuel; whereas, by diminishing the motor- power by one-half, the speed is only reduced by one- fifth. When, therefore, airships seek to perform long aerial voyages, the problem confronting them will be, how to reconcile the minimum speed enabling them to make way effectually against the prevailing winds, with a reduction of the motor power, which by diminishing the amount of fuel consumed, will enable the store of petrol to hold out sufficiently to reach the most distant points ! The wisest solution obviously would be to furnish the dirigible balloon with two independent motors. When a " special effort " was required, the two engines could be used ; but under favourable atmospheric con- ditions, the travellers would be content with the propulsion furnished by a single engine; Though the speed would be diminished somewhat, it would be possible to travel a good deal farther through the air. All we have said above concerning a dirigible's " radius of action " applies of course to aeroplanes, for which this con- sideration is also of the greatest importance. CONDITIONS OF EQUILIBRIUM OF DIRIGIBLES The first condition to be fulfilled by our dirigible balloon, whether stationary or in motion, is that it should always be " in equilibrium." When stationary, the airship should always maintain such a position that the geometrical axis of the solid body formed by its envelope is horizontal. Now when a dirigible balloon is suspended motionless in calm air, it is subjected to the action of two forces ; one is its weight, P (Fig. 5), which is applied to 18 THE CONQUEST OF THE AlR the centre of gravity of the system C formed by the envelope and all its supports ; the other is the thrust of the air, applied to a point B called the centre of thrust. If the envelope con- tained only its inflating gas, and had neither car nor cargo to carry, and even if the weight of this envelope were negligible, FIG. 5. Triangular suspension connection (indeformable) The car always maintains its position relative to the balloon irrespective of the tilting of the airship the centre of thrust and the centre of gravity would coincide. But the addition of the weights that the envelope has to lift into the atmosphere causes this result : these two forces are not a continuation of one another. As they must necessarily be equal if the balloon neither ascends nor descends, it follows that they will make the balloon turn until they are a continuation of one another, and our airship will then take the position indicated by Fig. 5 (No. 2). Now this inclined position would be incompatible with rapid speed, inasmuch as it would increase, in the travelling direction, the extent of the area exposed to the resistance of the air. Moreover, the air gliding over the greater surface, arising from inclination, and attacking the latter obliquely, would tend to drive the airship downwards. We shall see later how the aeroplane is based precisely upon this principle. Hence to avoid this inclined position, the weight must be distributed properly along the car from MN, in such a manner that, when the balloon is horizontal, the two forces, pressure BQ and weight CP, are upon the same vertical line. Then THE RESISTANCE OF THE AIR 19 " static equilibrium " will be ensured. We see therefore that the connections between the car and the envelope must never vary, though at the same time they must be allowed a certain flexibility, which is indispensable to aerial navigation. We shall return to this question when we deal with longitudinal stability. But this is not all ; the balloon, as it advances under the combined action of its motor, rudder and the resistance of the air, must preserve a general stability. It must remain per- ceptibly horizontal, and must not execute violent or extensive movements, either from fore to aft, or from right to left ; in other words, there must be neither " pitching " nor " rolling." Every one knows the general methods of aeronauts with spherical non-dirigible balloons. To ascend, they diminish the total weight of their balloon by throwing out ballast, that is, part of a supplementary weight, comprising bags of sand, which they carry with them. When, on the other hand, they want to descend, as they have no means of increasing their weight, they diminish the thrust of the air on the balloon by permitting some of the light gas in the envelope (the specific lightness of which constitutes the lifting power of the balloon) to escape through a valve. This ascensional effort diminishes in proportion to the amount of gas allowed to escape. The aeronaut therefore is able to ascend or descend at will by the dual means of ballast and valve. But this simple method cannot be applied to the operation of a dirigible balloon. Dynamic equilibrium, that is to say the equilibrium of the airship in motion, must take into account not only its weight and the sustaining pressure of the air, but also the resistance of the air brought to bear upon its envelope, which resistance depends on the dimensions and the shape of that envelope ; in calculations, this shape is assumed to be invariable. Now what will happen if we allow a portion of the gas enclosed in the envelope to escape ? When the balloon descends from the atmospheric stratum from which the aeronaut wishes to approach the earth, it will find itself in masses of air, the pressure of which increases as it nears the ground. This may be understood easily, since the lower strata bears the weight of the upper strata. The confined gas, now insufficient to fill the balloon as a certain portion has been 20 THE CONQUEST OF THE AIR allowed to escape, will contract ; the balloon, no longer full, will become flaccid, and will lose its original shape. Con- sequently the centre of resistance of the air will have changed, as well as the centre of thrust, and the initial conditions will no longer prevail. As these conditions were used as the basis of calculations dealing with the equilibrium of the airship, that equilibrium can be maintained no longer. THE AIR BALLONNET : RIGID BALLOONS All these inconveniences are obviated by an ingenious con- trivance, the idea of which originated with General Meusnier, who formulated it in 1784, only a year after the brilliant experiments of the Montgolfier brothers. As with all re- markable developments evolved prematurely, General Meusnier's idea was forgotten, and it was not until 1872 that the famous naval engineer, Dupuy de Lome, the inventor of the ironclad, resuscitated it in connection with his attempts to make balloons dirigible. We have seen above that it is absolutely essential to keep the balloon always perfectly inflated ; on the other hand, in order to descend, it is necessary to let out gas, which empties the envelope partially. To maintain the volume of the latter, it would be necessary therefore to carry a reserve supply of hydrogen to introduce into the envelope by means of a pump worked from the car. But when we consider that it would be requisite to carry this hydrogen compressed in very strong steel cylinders, we see, as a simple calculation conclusively testifies, that the weight of the necessary number of cylinders would be prohibitive. Consequently, the aeronaut is obliged to reject this method, which is perfect from the theoretical point of view, but impracticable in fact. He will rely, not upon a supplementary stock of hydrogen, but on air drawn from the surrounding atmosphere, to restore the original volume, and he will replace the hydrogen lost in the descent by an equal volume of air which he will introduce into the envelope by means of a pump. At the same time, the danger that would be incurred by sending this air directly into the envelope of the balloon must not be overlooked. It would mingle with the remaining THE RESISTANCE OF THE AIR 21 hydrogen, and produce a gas not only as inflammable as hydrogen, but an explosive element infinitely more dangerous. Here the ingenious artifice of the ballonnet comes into play. Instead of making the interior of the balloon a single recep- tacle, constituting the whole interior, it is divided in two by a fabric partition liable to _. deformation (Fig. 6). This partition occupies the lower part of the balloon, and there forms a space called Air Pipe. FIG. 6. The Air-ballonnet! the air -ballonnet } communi- cating with the car below by a tube through which air can be pumped. When the balloon, at the beginning of its ascent, is inflated fully with hydrogen, this fabric partition lies against the lower part of the envelope, exactly like a lining. As the balloon rises, the interior gas expands, because the outer air becomes less dense, and a portion of this gas escapes through automatic valves. The balloon therefore remains fully inflated so long as it rises. But when the descent begins, the gas, diminished by the quantity which has escaped during the ascent, no longer suffices to fill the envelope, which would then become flaccid, lose its original shape, and compromise the general equilibrium. This is when the ballonnet comes into action. By means of a pump installed in the car, the aeronauts force air into the ballonnet, until the sum of the new volume it acquires and that of the remaining hydrogen gas reconstitute the total original volume of the aerostat. In this way the initial conditions of equilibrium are maintained always, in conformity with the calculations of the constructors. The air-ballonnet, as will be seen, fulfils in aeronautics the same function as the " natatory gland " of fish, which enables these latter to maintain equilibrium in water under all conditions. There is another way of ensuring this permanence of form so essential to the dirigible balloon. That is to make the balloon rigid. This last heroic solution has been adopted by 22 THE CONQUEST OF THE AIR Count Zeppelin for his gigantic Zeppelin balloons, the largest of which attained 18,000 cubic metres. To ensure this invariability of form, the balloon is furnished with an absolutely rigid metallic " carcase," made of aluminium tubes. This skeleton is divided into several compartments, and a very strong yet light fabric is stretched over the whole. This is the outer envelope, on which the resistance of the air is exercised during the flight of the airship. In addition, there is, in the interior of each compartment, a balloon of air-tight rubber fabric, which is inflated with hydrogen. Thus the airship contains a certain number of balloons, the sum of whose lifting power constitutes the total ascensional effort. The external form is invariable, owing to the material of the envelope and the framework on which it is stretched. It may be seen at a glance what colossal difficulties such an arrangement presents ; the difficulty of constructing a trellised cylinder 120 metres long and 11 metres wide, to say nothing of its expense ; the labour in fixing the external envelope ; and, finally, the complication of inflating the elementary balloons contained in each of the compartments. Successive catas- trophes have shown the difficulty if not impossibility of managing such masses both at starting and landing. We shall discuss this question later on. But in any case it is difficult, and also very perilous, to give the body of an airship a rigid substructure. Despite these difficulties, the indomitable perseverance of Count Zeppelin, the patriotism of his countrymen, who placed the requisite financial assistance at his disposal, the friendly support of the Emperor William, and the admirable German military aeronautical organisation, have enabled several of these vessels to be constructed, which, owing to the advan- tages arising from their large dimensions, have been able to accomplish some remarkable journeys, though six or seven came to an unfortunate end. ALTITUDE STABILITY : ELEVATORS This question of " stability " is of the utmost importance, therefore. It is the basis of aerial navigation. Every one knows that the aerostat, whether dirigible or not, THE RESISTANCE OF THE AIR 23 can rise or sink at will by the action of ballast or escape-valve. The skill of the aeronaut lies in economising the expenditure of these two essential elements; the ballonnet, under these conditions, ensures the permanence of the exterior form. But this double action, expenditure of ballast and expendi- ture of gas, soon places the aerostat hors de combat. Therefore it is essential to preserve carefully a sufficient stock of ballast to guard against the always possible dangers of a difficult or unexpected landing ; sufficient gas must be preserved also to enable a quantity thereof to escape at the last moment to descend sharply. Thus it has been found necessary to invent something else for dirigible aerostats destined to undertake long voyages, and this new appliance is the " elevator." A dirigible balloon, indeed, requires motive power, which, through the intermediary of a propeller (generally a screw), provides the independent speed without which it is impossible to steer. But of this motive power, employed for horizontal propulsion, a small portion may be diverted which will serve for vertical propulsion ; that is to say, in the particular case we are considering, it may be used to make the aerostat rise or sink slightly, without any expenditure either of gas or ballast. The arrangement consists in providing the dirigible balloon with planes which can be inclined as desired, and are known as " elevators." These planes move about a horizontal axis, placed transversely to the axis of the balloon (Fig. 7), and may be disposed in the centre, or fore or aft of the apparatus. In our Figure, we have supposed that they are placed at the tail of the pisciform envelope. A glance at these two Figures will convince us of their controlling action ; they raise or depress the "nose" of the balloon at will, just as the ordinary rudder turns it to the right or left. The same thing happens if they are placed in front. Generally speaking, it is difficult to attach them to the envelope itself, and thus they are placed on the car, as in the case of the CUment-Bayard (Fig. 24), where we see this rudder, in the form of three parallel planes, placed in front of the long car, immediately behind the screw propeller. This apparatus is also called the " stabilisator." The elevators may be placed also towards the middle 24 THE CONQUEST OF THE AIR either of the envelope or of the car. In this case the action, by virtue of the resistance they offer to the air, no longer serves to raise or depress the stern or the bow, that is to say, to incline the balloon, but to lift or lower the whole body. It has been proposed to obtain the same result by means of screws with vertical axes, which would, of course, revolve Direction of Travel. .ctioto of air resistance upon the rudder Air Ekvating rudder 'resistance (ascending) Elevating rudder (descending) FIG. 7. Action of the elevator The moving balloon is caused to ascend or descend by the action of the air upon the rudder, according to its inclination horizontally. Their action, in this case, would have the effect of raising or lowering the airship by exercising pressure thereon either from above or below, according to the direction in which they were rotated. A more rational proposition is to fit the propeller shaft with a universal joint, so that it could be inclined either upwards or downwards. But neither of these expedients is as simple or efficient as the elevator, which is now in general use. STABILITY OF DIRECTION : LONGITUDINAL STABILITY "Route Stability," or "Stability of Direction," consists of the following condition which the balloon ought to fulfil its axis must always be turned in accordance with the direction of the course it is desired to follow (Fig. 8). This stability is a quality which is exercised in the horizontal plane; we must therefore suppose that in Fig. 8 the dirigible balloon is seen from above and is travelling parallel with the ground. FIG. 8. Route stability THE RESISTANCE OF THE AIR 25 How is this stability to be ensured? In the following manner : as soon as the balloon shows a disposition to deviate from the direction it ought to follow, TT, a direction which is tangent to the course set down, it must be brought back by the resistance of the air itself. For this purpose, continuous use may be made of _____ the " steering rudder," which, like the rudder of a boat, serves to direct the airship from right to left. But this method would be fatiguing to the helmsman, and not sufficiently efficient to prevent unforeseen divergences. Aero- nauts, therefore, prefer to ensure stability of direction by the design of the balloon itself, and this is the chief reason for adopting the lines of the fish, with the larger end in front. Then the centre of gravity of the balloon is brought to the front, and the " leverage " of the stabilisating elements formed by the stern of the envelope is efficiently augmented. However, the envelope of the balloon itself would not suffice, so just astern of the latter "stabilisating surfaces" have been disposed, formed of vertical planes fixed to the envelope, forming, as it were, a keel for the dirigible analogous to the keel of a ship. By this means, stability of direction is obtained naturally, without having recourse to the ordinary rudder, which is used only for steering. Still we have to consider " longitudinal stability." What is this third stability ? It is the property of remaining always horizontal or nearly so, which the balloon ought to retain, through whatever evolutions its pilot may pass it. In other words, it is the property of not " pitching." This longitudinal stability is much more important even than stability of direction. Should the latter be imperfect, the aeronaut corrects it readily by using his steering apparatus 26 THE CONQUEST OF THE AIR more frequently. But if longitudinal stability is defective, the balloon may incline in a dangerous manner, and here the necessity of an unvarying connection between the car and the envelope appears more important than ever. If, in fact, the balloon and the car are united by unvarying attachments, the suspension being triangular when in a state tKrust TKc two forces BQ et CP tending to secure r eQuilibrium of the balloon. FlG. 9. Longitudinal stability The airship must maintain the position shown at left, and if, accidentally, it tilts as shown at right it must recover its horizontal position of equilibrium, the thrust and the weight are in the extension of one another. If the balloon inclines, the car retaining its relative position, the weight is no longer in the prolongation of thrust ; but then the two forces tend to " trim " the airship. If, on the contrary, the suspension is liable to displacement (Fig. 10), we see that if the dirigible be tilted for some reason, its equilibrium would not be restored by the action of the weight of its car and cargo. Therefore, the suspension must be incapable of displacement, and for this reason the idea of making the balloon rigid, and of uniting it to its car by rigid attachments, has occurred often (Zeppelin, Pax, for instance). But absolute rigidity involves terrible drawbacks ; all rigid balloons so far have finished up with accidents. Aeronauts in general have decided in favour of triangular suspension (Fig. 9) ; these are sufficiently un- varying, as long experience has shown. One of the most serious causes of longitudinal instability is due to the gas which fills the balloon ; its tendency is to THE RESISTANCE OF THE AIR 27 augment any inclination produced accidentally. This x gas, from its very nature, is compressible, and on the other hand, the envelope of supple material is essentially deformable. A transverse section of an inflated balloon would not therefore be a circle, but an ovoid figure (Fig. 11), the larger end of which would be uppermost. There are two reasons for this : FIG. 10. Instability produced by parallel connections The suspension being articulated, the centre of gravity always rests below the centre of thrust, B, even if the airship tilts : therefore it cannot recover itself in the first place, the traction of the suspensory ropes of the car compresses the envelope laterally from A to B and from A' to B', making it almost flat ; in the second place, the interior gas, being lighter than air, tends to accumulate in the upper part, and this force acts obviously in the same manner as the former, deforming the transverse section of the balloon. At a glance, this deformation would not appear to have any injurious influence on longitudinal stability ; yet, the last cause we have put forward may be adverse to this stability. Let us suppose, for example, that the balloon tilts as in Fig. 1 2 ; the interior gas, which is lighter than air, immediately rushes to the upper part, leaving the lowered end insufficiently inflated. The centre of thrust B is displaced towards the right, and as the two forces which would tend to restore the equili- brium of the balloon, BP and CP, will be less and less distant from one another, this restoration will not take place. Such a contingency would be serious indeed if the balloon were imperfectly inflated, but with a full balloon, this accident is 28 THE CONQUEST OF THE AIR less to be dreaded. Thus the function of the ballonnet is doubly important, because it ensures permanent inflation, and consequently persistent stability, for the air of the ballonnet, imprisoned in its special envelope, cannot accumulate in the lowered part of the dirigible. Colonel Renard even subdivided the ballonnet into flexible com- partments without any inter- communication in such a man- ner that the air contained therein could in no possible case accumulate by its own weight or inclination at either end thereof (Fig. 12 B). Aeronauts have every reason to dread the inclination of air- . ships, and to avoid them by every possible device. Resist- ance of the material, the suspension, &c., is calculated on the assumption that the airship will be horizontal, or very nearly so, in which case the strain is distributed equally FiG.jll. Deformations of transverse section The pressure of the suspension ropes flattens the "cheek" of the envelope, and gives it the shape of a pear on the transverse profile, instead of the original spherical form throughout the suspension and on all the material. If, on the contrary, the airship should incline in an exaggerated and unforeseen fashion, there would be elements which carried no strain at all, while others would be overloaded ; serious accidents have resulted from such a cause. Accordingly the operation of filling the ballonnet is a most important operation in aeronautics. Many constructors now make it automatic in action. A pump is continually driving air into the ballonnet, while a valve in the latter opens as soon as the pressure of the air exceeds a given point ; the super- fluous air escapes into the atmosphere, and the pressure within resumes its normal value, ensuring the constant preservation of shape. THE RESISTANCE OF THE AIR 29 REALISATION OF DYNAMIC EQUILIBRIUM: CRITICAL SPEED : THE "EMPENNAGE" It was in 1904 that Colonel Charles Renard first formulated the exact laws concerning the dynamic equilibrium of dirigible balloons, discovered the causes which render this equilibrium Division bl of ballonnet B into 3 ballonnets bl b2 b3. to prevent accumulation of air in B Destruction of longitudinal Stability owin to displacement of fcas. FIG. 12. Action of the ballonnet precarious, and at the same time indicated by what means it might be obtained completely. Let us now summarise briefly the results achieved by this distinguished officer. We will commence by noting that if we took a symmetrical fusiform balloon, tapering equally at each end and suspended on a horizontal axis pass- ing through its centre of gravity, this balloon would be in a state of " indifferent " longitudi- nal equilibrium (Fig. 13). If the axis of the balloon is horizontal, and if a horizontal current of air bears upon it, the bal- Axis of suspension^ Axis of suspension FIG. 13. Imperfect equilibrium ne pos the latter would increase steadily loon will be in equili- brium, but an equilibrium essentially " unstable," for it is proved, that so soon as the envelope thus suspended inclines ever so slightly, this inclination will increase until the axis of the balloon is perpendicular to the current of air ; in other 30 THE CONQUEST OF THE AIR words, till it stands on end. This position is inadmissible, for it would show absolute instability. If, instead of a symmetrical fusiform balloon, we take a pisciform balloon, with the larger end in front, the instability would still persist, though it would be diminished considerably. Here we are not in the domain of theory but of experience, for it was by dint of innumerable experiments, carried out with admirable method, that Colonel Renard obtained all the results we are now discussing. In the case of a pisciform balloon the disturbing effect is due, in unequal degrees, to the diameter of the balloon, its inclination and speed, whereas the stabilisating effect depends on the inclination and diameter of the balloon, but not upon the speed. The disturbing factor in the equilibrium is attributable solely therefore to speed, and develops very swiftly as the speed is increased. It will be understood readily that there is a certain speed for which the two effects are equal, and beyond which the disturbing effect, depending on speed, will overpower the stabilisating effect. This velocity Colonel Renard called " critical speed." If this be exceeded, the equilibrium of the balloon becomes unstable. The most remarkable feature of Colonel Benard's brilliant labours in this field is, that they are not only the expression of scientific calculations, but, above all, of experiments conducted on highly skilled lines, experiments in which the gifted aeronaut submitted keels of various shapes and dimensions to the action of a current of air which he could modify at will. The question arises naturally as to whether this " critical speed " is very high. As a matter of fact it is relatively slight, as the following figures will show. Let us take, for instance, a dirigible pisciform balloon of the type La France. Its critical speed is 10 metres a second, or 36 kilometres an hour, and a 24 horse-power motor suffices for this speed. Now the lightness of modern engines is such, that a balloon of this type could lift easily a motor of from 80 to 100 horse-power. With such a motor theoretically it might have a speed of 15 metres a second, or 55 kilometres per hour, but it could not accomplish this in practice; for, its critical speed being 36 kilometres, its equilibrium would become unstable if this :? O * * i H I? * ? THE RESISTANCE OF THE AIR 81 were exceeded. In, fact long before this velocity was attained, the stability of the airship would become precarious and totally inadequate. Therefore it would be useless to essay the lightening of the motor, that is to say to increase the speed of balloons, unless we had a means of en- suring its stability, for, as Colonel Renard wittily ob- served in the case we have quoted : " If the balloon were provided with a motor of 100 horse-power, the first 24 would drive it, and the other 76 would break our necks." This means of stabilisa- tion is the empennage ; the systematic use of rigid planes, both vertical and horizontal, axis of the balloon, and placed well FIG. 14i Cruciform empennage of the Patrie and Republique -^ The empennage jurfaces we rigidjplanes : passing through the aft of the centre of Ville de Part* Buyatd-Clemertt FIG. 15. Pneumatic empennages The empennages are elongated battonnets, the hydrogen with which they are inflated counteracting their weight gravity. The resemblance of a balloon thus fitted to a feathered arrow is obvious ; hence the name of the apparatus. With a balloon of the size of La France (60 metres long and 10 metres in diameter), the surface necessary to achieve strict empennation, i.e., to annul the disturbing effect, is 40 square metres, lying 25 metres behind the centre of gravity. By 32 THE CONQUEST OF THE AIR slightly augmenting tke surface and the distance, a degree of security higher still is secured. But how is this " empennation " to be carried out ? In the Lebaudy balloon it was fulfilled by means of surfaces affixed to the framework between the balloon and the car ; in La Patrie, a still better plan was adopted, for the feathered arrow was realised literally by fitting four surfaces in the form of a cross to the stern of the envelope, as shown in Fig. 14. Colonel Kenard pointed out another method of obtaining the effect of the empennage without the use of rigid planes, difficult to fix to the envelope of the airship and tending to overload the prow. This was to affix to the stern of the envelope elongated ballonnets projecting from the body of the balloon. This method was adopted by M. Surcouf in two different forms : cylindrical ballonnets for M. Deutsch's Ville de Paris (Fig. 1 5), and conical ballonnets for M. Clement's Bayard. Being inflated with hydrogen, their weight is counteracted, and they no longer constitute a useless and unsyrnmetrical supple- mentary load to the airship. There are other means by which such instability may be overcome ; the use, for instance, of a very elongated car, which allows a considerable weight to be displaced from stem to stern. This method was adopted in the Zeppelin; but such an arrangement is difficult to work, and the empennage is at once simpler and very much safer. POINT OF APPLICATION OF THE PROPELLING FORCE : "DEVIATION" Where should the motive power which is to propel the dirigible balloon be applied ? At what point of the complex system formed by the envelope, its rigging, &c., should the propulsive force act ? We have to examine this question yet. As the essential sustaining part of the airship is the envelope, it is this which offers the maximum resistance to the air. Theoretically, therefore, the propelling effort should be applied to the axis of the balloon itself, as many inventors have maintained. Several, indeed, have sought to put this theory into practice, notably the unfortunate Brazilian Severo d' Albu- querque with his balloon Pax, which ended in a catastrophe, and the constructor Rose, who produced a twin airship, the THE RESISTANCE OF THE AIR 33 axis of the screw being between the two balloons which constituted his system. This conception would be a perfectly just one if the car and the rigging offered no resistance to the air; but their resistance is far from negligible. The car has a transverse section of several square metres, and the sum of the surfaces, presented by the suspensory ropes is enor- mous. For instance sup- pose the latter to be steel cords of three strands, each of three threads, that is, nine threads to the cord ; their diameter is about three millimetres ; their length be- tween the car and theballoon about ten metres. One of FIG. 16. Point for applying the propelling effort The resistance of the air bears partly upon the envelope at the point, B, and the car, together with its equipment, at Cj Consequently the propelling effort should be applied at A, to overcome the resultant of the two resistances these ropes would therefore offer a resisting surface of about 300 square centimetres or three square decimetres ; ten would represent a surface resistance of about one-third of a square metre, while sixty cords would equal two square metres. Add to this the sum of the sections of the knots, splices, pulleys, ropes used in the manoeuvring of the vessel, transverse members, the pipe carrying the compressed air into the ballonnet by the aid of the special pump, the surfaces of the rigging, guide-ropes, &c., and finally the surfaces of the passengers, and a sum of resisting surfaces is soon obtained, beyond the sustaining envelope, and equal to a quarter, a third, and even more of a transverse section thereof. If, therefore, we represent the resistance offered by the envelope as BE, (Fig. 16), and that offered by the car and its accessories as CR', the motive-power AF must be applied at the point A, between B and C, and nearer to B than to C, to ensure the permanently horizontal position of the system under the combined action of motive and resistance efforts. But, on the other hand, it is difficult, at least in the present state of aeronautical censtruction, to attach the shaft of the screw to the envelope itself, without using rigid envelopes such as those of the Zeppelin or the Pax. 34 THE CONQUEST OF THE AIR Perforce, therefore, the aeronaut has to be content to apply the propelling power to the car. Hence a tendency in the dirigible balloon to tip up at the nose, because the force F is not exercised directly at the point of application A, the resultant of the two forces R and R'. The constant use of the elevating rudder becomes necessary, and we find that this tilting is the more pro- nounced the farther the car B K N FIG. 17. Rational disposition of the screw is from the envelope. The term "deviation" is used to describe this tilting effect produced by the action of the pro- peller. It will be understood that this " deviation " will be modified in proportion as the car is brought closer to the balloon ; but such is limited by the danger of installing an explosion motor too closely to an envelope containing an inflammable gas. The golden mean must be observed. If the car were too far from the balloon, the tilting effect would be very great, and the balloon would incline without advancing. Cornte de la Vaulx found a very ingenious solution of this difficulty. He fixed the screw H (Fig. 17) to a shaft HK at a point between the envelope and the car. The latter contains the motor which works the shaft HK through a transmission system. This is a very rational solution, and it is possible that it may be followed widely in airship construction. As to the position of the propeller, this may vary con- siderably. Colonel Renard and M. Surcouf, the constructor of the dirigibles Bayard-CUment and Ville de Paris, place it at the prow of the car ; under these conditions it draws the balloon. Other constructors place it at the stern. This was the plan adopted by Giffard, Dupuy de Lome, and the brothers Tissandier. M. Julliot, the engineer, to whom we owe the Lebaudy and the Patrie, introduced two screws, which he fixed outside the car, on either side and almost in the centre. We see then that various arrangements are in use. But on the whole there seems to be a preference to place the propeller at the prow of the car. CHAPTER III THE WIND AND DIRIGIBLE BALLOONS THE AERONAUT'S WORST ENEMY : How WIND INTERVENES IN THE PROBLEM OF AERIAL NAVIGATION : RELATION BETWEEN WIND AND AIRSHIP SPEED : THE " APPROACH- ABLE ANGLE " : ACCESSIBLE AND INACCESSIBLE REGIONS WHAT IS WIND ? WIND is simple to define : it is the m /ement of atmospheric masses in a horizontal direction ; tne displacement of air parallel to the surface of the earth. Its study is one of the principal objects of that branch of physics called meteorology. Meteorology, or rather the study of atmospheric phenomena over continents, otherwise called " Continental meteorology," is relatively backward, as compared with nautical meteorology. The reason is that the immense and uniform surface of the ocean allows molecules of air to obey the laws of equilibrium and the movement of fluids freely, whereas the surface of the land, bristling with an infinite variety of obstacles, offers much greater difficulty to the establishment of clearly defined laws. Moreover, the waters of the sea cover nearly three-quarters of the surface of the terrestrial globe ; it is above them, there- fore, that the great laws of atmospheric movements are demonstrated. Finally, all sailors are meteorologists, whereas on land keen observers are rare. This fact has given rise to the sarcastic definition of meteorology as a science which consists in knowing what kind of weather it was yester- day. Yet it is with winds blowing over land that aeronauts will have to reckon, at least, in their early days. The moment has not yet come (though, indeed, it may not be far distant) when, launching themselves boldly over the sea, they will have to 35 36 THE CONQUEST OF THE AIR struggle with oceanic winds, and consequently to experience personally the laws of nautical meteorology. The wind is differentiated by its direction and its velocity, or its force. Its direction is indicated from the point of the horizon whence it blows ; a north-east wind is a wind which blows from the north-east, and so forth ; the so-called " com- pass-card " of the ma- riner gives all wind directions by initials (Fig. 18). The velocity of the wind is reckoned in metres per second ; we should say, for instance, a wind of 7*50 m. per second. By multiplying the speed in metres per second by the factor of 3600, the number ot seconds in an hour, we get the speed for the wind in kilometres per hour. A wind of 10 metres a second is, therefore, 36 kilometres an hour; the wind of 7*50 m. corresponds to 26 kilometres an hour. The force of the wind may be measured by the pressure it exercises upon a stationary object opposed perpendicu- larly thereto. Sailors have deduced from centuries of navi- gation in sailing-vessels that the pressure of a wind making a metre per second upon a surface of one square metre perpen- dicular to its direction is 0'125 m., or, in plain words, 125 grammes per square metre. This pressure increases in proportion to the surface of resistance, and in proportion to the square of the wind's speed. With a wind blowing 2 metres per second, it would amount therefore to 4x0*125 kg., or 500 grammes per square metre ; for a wind travelling at a speed of 4 metres, it would be 16x0-125, or 2 kilogrammes per square metre, and so on. When the velocity of the wind becomes considerable, the FIG. 18. Compass-card WIND AND DIRIGIBLE BALLOONS 37 pressure it exercises upon fixed obstacles becomes enormous ; a wind of 25 metres per second, or 90 kilometres an hour, would exercise a pressure of 25 x 25 X 0*125, or nearly 80 kilogrammes per square metre. The accident which resulted in the loss of the dirigible balloon La Patrie was due to this tremendous force. WIND AND THE AERONAUT Let us now define this idea of the wind rather more pre- cisely, for, in the special case we are studying, an inaccurate idea thereof is formed often, and it must not be forgotten that it is in the very bosom of the atmosphere that we encounter it with our dirigible balloons. Let us therefore study the wind, not in its relation to the ground, but in its relation to the airship. If we were in a spherical balloon, it would be susceptible to this pressure so long as, in process of inflation, it was held to the ground by mooring ropes ; the " force of the wind " would tend to beat it down upon the ground or to tear it from the hands of those who were holding and keeping it stationary. But so soon as its moorings are cast off, so soon as the balloon rises into the air without any propelling mechanism, the aeronaut is only conscious of absolute calm : the wind, in fact, is im- perceptible to him, because the wind is a relative movement of the molecules of air in respect of an observer stationed upon the ground. Once in the air, a spherical balloon forms part of the atmosphere. It is carried along by the wind itself, and moves with it ; it is not displaced in relation to it. So long as the balloon neither rises nor sinks, a little banderole fastened to the rigging hangs vertically, without fluttering in the wind as it would were the balloon held to the ground. Consequently so far as concerns the aeronaut who belongs, not to the earth, but to the atmosphere, wind is non-existent ; these were the words enunciated by Colonel Renard the first time he described in public his experiments in connection with the steering of balloons. If then we were to take an airship, dirigible or otherwise, everything in connection therewith would happen as if the air were still. If the balloon is dirigible, that is to say, if it is furnished with a motor and a propeller, 38 THE CONQUEST OF THE AIR and if these forms have been logically designed, the aeronaut could move in this atmosphere in any direction, as if the wind did not exist; as his balloon advanced, he would have the same sensation as if he were passing through an absolutely calm atmosphere. He would have an impression of wind, but this wind would have nothing in common with that which blows over the surface of the earth ; it would be a current of air from the stem to the stern of the balloon, created fry the aeronaut himself "by his advance ; it would be the result of the displacement of the balloon by its propeller. Stop the latter, and calm would be restored at once ; the aerial navigator would feel no longer the slightest current of air. To sum up, then, we may say with Colonel Renard that " the balloon belongs to, and has nothing to fear from, the air. If it is furnished with a propeller and a motor, in a word, if it is dirigible, the wind changes nothing, neither in the nature of the efforts it has to undergo during the voyage nor in the speed of its displacement in relation to the aerial ocean in which it floats. Everything is just as if, the air being perfectly still, the earth were flying along beneath with a speed equal and contrary to that of the wind." * In the case of the aerostat, as of the airship, the wind there- fore signifies, from the final result point of view, a relative displacement of the ground, exactly as if the aerial swimmer being stationary, the earth were carried along by the current of air. From this we shall note interesting results, which will show us the limitations of the efficient action of dirigible balloons. INDEPENDENT SPEED AND WIND VELOCITY : THE APPROACHABLE ANGLE Let us imagine (Fig. 19) hovering over Paris, an "aerial fleet," f comprising a central balloon, playing the part of a flagship, occupying the centre of a circle formed by six aerial cruisers. All the engines have been stopped, and the flotilla is for the moment motionless in relation to the air. The wind is blowing from the west at a speed of 8 metres per second, that is say, 29 kilometres an hour. * Colonel Oh. Kenard : La Navigation afrienne, a lecture delivered at a meeting of the Societe des Amis de la Science, April 8, 1886. f Ibid. WIND AND DIRIGIBLE BALLOONS 39 The admiral's balloon issues a command : the six cruisers are to effect a reconnaissance, each going off in a different direction, while the balloon in command will remain stationary to await their return. Let us imagine all these cruisers travelling at the same speed, 6*50 metres a second, for instance, or 22 kilometres an hour: this is the independent LAGNY R.Marne, FIG. 19. Example of relative wind speed of each in calm air. At the end of an hour they would all be 22 kilometres from the admiral's balloon; in other words, they would be distributed on the circumference of a circle having a radius of 22 kilometres, the geometrical centre of which would be occupied by the " flagship." This is what would be happening in the air. Now let us see how our seven balloons have been disposed above the ground, taking into account the wind, which is blowing at the rate of 8 metres a second, or 29 kilometres an hour. The earth will appear to have fled towards the west precisely at the speed of the wind, that is, 29 kilometres an hour. Thus Paris, which just now was immediately under the admiral's balloon, will be removed 29 kilometres west of the " flagship," which, having stopped its engine, has remained motionless in the air. Below this balloon will stretch a new region, that of the Marne, and Lagny is now the centre of the circle with a radius of 22 kilometres, on the circumference of which the six aerial cruisers are distributed symmetrically. 40 THE CONQUEST OF THE AIR Consequently the west wind has had no effect really but that of displacing the whole aerial fleet en bloc towards the east by a distance of 29 kilometres under the wind. Therefore it has made no change in the relative positions of the airships. Equipped with this result, we may determine now the points which the dirigible balloon could attempt to reach, taking into account its independent speed and the velocity of the wind. Let us imagine our balloon, with its motor and propeller, having an independent speed of 6*50 metres per second; this, as we have already explained, amounts to saying that in absolutely calm air it would travel 22 kilometres an hour. Let us suppose that this independent speed differs from that of the wind, which we will take to be 8 metres a second (29 kilometres an hour). The balloon sets out from the point P (Fig. 20), in the direction PA, at an independent speed represented by the length, PB : this would mean that, if there were no wind, at the end of an hour it would have arrived at B. But the wind is blowing in the direction PS with a velocity represented by PV. The balloon, therefore, will travel along the route indicated in length and in direction by the diagonal PR of the parallelogram PBYR, and at the end of an hour, under the combined action of its independent speed BP and that of the wind, PV, it will have arrived at the point R, having throughout preserved the direction represented by the silhouettes (1 ) and (2). Consequently should the velocity of the wind be greater than that of the airship, and should it be directly opposed to the latter, there would be regions in the atmosphere inaccessible to the airship, which could deviate only by the aid of its motor from the direction of the wind, as is shown in Fig. 20. Now we will look more closely into this question. But a little careful attention on the part of the reader is necessary, for it must be pointed out that the whole secret of dirigiblity in the air is explained in the following paragraphs. Three varying conditions might prevail : 1. The independent speed of the balloon is less than that of the wind. (Fig. 21.) Let P be the starting-point of the balloon, and let us take the line PA to represent its independent speed. I s 1 n 4 CO EC . of fo 1 H I I B / U) V WIND AND DIRIGIBLE BALLOONS 41 This means that if the air were calm, at the end of an hour the airship would find itself somewhere on the circumference of the circle C, the centre of which is P, and the radius of which corresponds to the speed PA. But the wind is blowing with a speed V, greater than v : accordingly, the whole circle, C, at the end of an hour is transported to C', and the balloon will be somewhere on this new circle C', which is, from this very fact, the circle of points approachable in the space of an hour, the distance, PP', being equal to the velocity of the wind. Therefore the only points of the space which the balloon can reach will le those comprised ivithin the angle formed ly the tangents leading from the point P to the circle C', i.e., comprised in the region which is shaded in the figure. All the remaining space would be inaccessible to the balloon. Con- sequently the accessible angle will be greater, the less the difference between the velocity FIG. 21. Instance where the independent speed o f the wind and the is less than wind velocity FlG. 20. Combined effects of wind and independent speed The airship sets out in the direction, P, A ; but the wind blows t P, S, consequently the airship makes diagonal path, P, R The balloon can manoeuvre only in the atmospheric space indicated by the shading independent speed of the balloon. The space would be nil if the speed of the balloon itself were nil ; this is the case with free balloons, which can only move along the line PP'. 2. The independent speed of the balloon is equal to the wind velocity (Fig. 22). The balloon is at the point P, its indepen- dent speed is PA, which is equal to the velocity of the wind. 42 THE CONQUEST OF THE AIR If there were no wind, the balloon at the end of an hour would be somewhere on the circumference of the circle C ; but the wind is blowing with the speed PP', exactly equal to that of the airship itself; the circle C is therefore transported to C' and at the end of an hour the balloon is on the circumference of C'. The shaded angle in Fig. 21, which has become more and more obtuse as the values of the two speeds approxi- mated, becomes equal to two right angles, and the accessible region com- prises the entire half of the space ; is to the right of the tangent from the point P to the circle C'. 3. The independent speed of the balloon is greater than the velocity of the wind (Fig. 23). FIG. 22. Case where independent speed equals wind velocity The airship is able to move in the whole halj of the shaded area to the right of its starting- point In this case there is no special angle to define the accessible regions ; the whole space is available to the airship, even in the direction contrary to that of the wind, and if the balloon goes dead against the current of air, it will advance in respect to the ground with a speed equal to the difference between its independent speed and the velocity of the wind : therefore all space is accessible to a dirigible balloon whose independent speed is greater than the wind velocity. The latter is the essential and sufficient condition governing perfect dirigibility. PRESENT CONDITIONS OF DIRIGIBILITY IN RELATION TO THE WIND We know now under what conditions an aeronaut can hope to reach any given point. Are these conditions compatible with the average state of the atmosphere; in other words, with the average wind velocities prevailing in our part of the WIND AND DIRIGIBLE BALLOONS 43 world ? Here we must rely on observation alone for a satis- factory answer. Our official meteorologists are silent on this point as on many others in their treatises ; so it has been requisite for our aeronauts to make the experiments necessary to obtain the results which are indis- pensable to them. Such experiments have been carried out for many years at the Chalais- Meudon military estab- lishment. These very in- teresting results are sum- marised in the Table on p. 44. The first column gives the velocity of the wind in metres per second ; the second, the corres- ponding velocity in kilo- metres per hour ; the third, the possibilities of encountering a wind of the velocity denoted in fractions of a thousand. Thus, for instance, if we take a wind of 5 metres a second, ~ s 3 .jr 5 1 -3 Se r3 i ! g O S A :i H ^ Jg H CONSTRUCTION AND MANAGEMENT 47 form, with the larger end forward, after the manner of fishes and birds, otherwise there will be a risk of low efficiency (examples of which are given in the following chapter). But the profile and the elongation still have to be considered. The envelopes constitute what is known in geometry as " surfaces of revolution," in the sense that they may be con- sidered as evolving by the rotation round their longitudinal axes, the curve which defines their profile. The constructor commences by fixing the length of the balloon, its maximum diameter, and the position of the latter in the length of the envelope. After this he calculates the profile, generally formed since Renard's time, of two parabolas united ; these parabolas are either simple or of the superior degree ; but these are mathematical details which I need indicate only. When the envelope is calculated, it is drawn, and the templates necessary for cutting out the pieces of material are made ; the latter, sewn together, constitute the body of the balloon. We will take the CUment Bayard as our type of dirigible balloon. This vessel is familiar to me since I have made several ascents and voyages therein, while the perfection of its construction and manoeuvring qualities entitle it to be cited as a typical example of French aeronautics. CONSTRUCTION OF THE ENVELOPE : THE GAS The profile of the envelope (Fig. 24) is formed by two parabolas of the third degree. The envelope is made of panels sewn together; its total volume is 3500 cubic metres. Its surface is 2250 square metres. It is 5 6 '2 5 metres in length and the maximum diameter is 10*58 metres. This envelope is inflated with pure hydrogen gas ; in spite of the high price of this gas, which costs 1 franc and sometimes more per cubic metre, it is preferable to coal gas, on account of its great lifting power, no matter how cheap the latter may be. Moreover, balloon fabric is now so perfect that it reduces the loss of gas by exudation to an insignificant degree. In the middle of the envelope is a ripping valve. This is an aperture in the upper part of the envelope covered by a band of fabric which can be torn off in an instant by the pull of a cord, should a rapid descent become necessary. This 48 THE CONQUEST OF THE AIR action is affected from the car. At the stern is the pneumatic empennage, consisting of four spherico-conical ballonnets, tan- gent to the back part of the envelope, and communicating therewith through holes. The air-ballonnet proper, divided into two parts, is 23 metres long, and has a volume of 1100 cubic metres. The balloon is furnished with four automatic valves; two for the hydrogen gas, which open automatically as soon as the internal pressure equals 40 millimetres of water, and two for the air, opening when the pressure equals 30 millimetres. These two pressures are indicated by two gauges placed on the front of the bridge under the eyes of the pilot. If a valve were not working automatically, he would be warned therefore, and could work it manually by pulling a cord. The air is forced continually into the ballonnet by a fan pumping 1800 litres per minute, and driven through transmission from the motor. When this breaks down, the fan can be worked by hand. The suspensions are thin steel cables of three strands, each of three threads. Some of them are 3, others 4 millimetres, in diameter, and they can withstand strains of 400 and 600 kilogrammes respectively. They terminate in " goose's-feet " of hemp fastened to boxwood stakes, and the latter are encased in a " girth " sewn into the fabric, which forms the envelope of the balloon. The net is thus rendered unnecessary, and this facilitates the passage of the molecules of air along the envelope, owing to the resistance offered by the obstruction from loops and knots being eliminated. Beneath the " suspension girth " is placed the lifting girth, also sewn to the fabric. The " lifts " are steel ropes, which are oblique in relation to the length of the balloon, and secure that indispensable triangular suspension that assures the solidity of the car and the envelope, both in longitudinal and lateral directions. These lifts connect together by four " knots," which also constitute the fixed points of the suspension. These knots may be seen distinctly in the diagram. CONSTRUCTION AND MANAGEMENT 49 50 THE CONQUEST OF THE AIR THE CAR, RUDDER, ELEVATOR, AND MOTOR The car is built up of a series of cubes of steel tubes of 30 and 40 millimetres diameter. The sides of the cubes measure 1*50 metres, and their contiguity forms the car. The sides of these cubes are made rigid by steel wire diagonals fitted with stretchers. The central part of the car has a height of 2 metres; its total length is 28 metres. The steering rudder is carried at the stern ; it is double, and its surface is about 15 square metres. It is composed of rubber fabric stretched upon a steel tube framework having its axis connected to the car by means of a cardan joint. The fourth knot of the lifting rope (that of the stern) and two stretchers serve to hold it. The "stabilisator," or elevator, fitted to the front of the car, is in reality a "triplane" turning about a horizontal axis, and able to be inclined from 16 to 17 degrees above or below the horizontal. Its efficiency is considerable, inasmuch as in accordance with specific calculations, when the machine is at full speed, the effect of the stabilisator is more or less equivalent to 100 kilogrammes of ballast, according to the degree of upward or downward longitudinal inclination. The elevator and the rudder are controlled through steel cables and chains, by two wheels placed upon the bridge on the right and left respectively ; these wheels, like those of motor-cars, are " irreversible." In the centre of the car is the passengers' accommodation as well as the pilot's position. The latter, by raising the floor of the car, is elevated about 50 centimetres. The pilot, standing on the left, has the steering wheel under his hand ; on his right is his assistant holding the wheel of the elevator. Forward is the motor room, and the pilot can communicate directly with the engineer. A vertical panel on the front of the bridge carries the whole of the controlling instruments. These are the balloon and air-ballonnet gauges ; the barometer to indicate continuously the altitude ; a barograph ; the dynamo- meter which permanently records the tractive effort of the propeller; and lastly, the speedometer registering the number of revolutions per minute made by the motor. In addition CONSTRUCTION AND MANAGEMENT 51 to this is a shelf carrying the chart and a compass, to indicate the course to be followed, the latter being well compensated owing to the masses of iron and steel in the balloon. Through the passengers' space extends a large suspended table carrying the road maps, indispensable to the voyage and for guidance by comparison with the country spread immediately below. Lastly under the car are the " skates " which enable the air- ship to alight without the car being injured by contact with the ground. The engine is an explosion motor, such as are used in automobiles. It is multicylindrical, works with a mixture of air and petrol gas, and is of 105 horse-power. The special materials of which it is constructed ensures, at one and the same time, great solidity and a remarkable regularity in running, without forfeiting that lightness indispensable to an aeronautical motor. It weighs 352 kilogrammes all told. The weight of the petrol tanks is 64 kilogrammes, that of the oil reservoirs 10 kilogrammes. The motor is water-cooled, 6 5 litres of water being carried in a radiator and a circulating system which weighs 8 3 kilogrammes complete. In " working order " the total weight, everything included, represents 5 kilo- grammes per horse-power. The engine runs at 1050 revolutions per minute, but by means of a reducing-system of two gear wheels, the propeller shaft does not make more than a third of this speed 350 revolutions per minute. The fuel consumption is from 38 to 40 litres per hour ; of oil about 5 litres. The whole of the motor is mounted upon a body, fixed to the car by springs in such a manner that vibration is reduced to the minimum, being no greater than in a well-built motor-car standing still with the motor running. The connection by circular segments is fitted with springs which can be easily regulated by means of a worm wheel so as to obtain a constant and absolutely certain tension. Lastly, we may add that the motor is fitted with two ignitions, magneto and accumulators, and that by means of decompression cocks it can be started up with the greatest ease. 52 THE CONQUEST OF THE AIR THE SCREW, "SLIP," DIMENSIONS, AND POSITION The screw is the propeller exclusively used to-day in aerial navigation, both upon dirigibles and aeroplanes. As a matter of fact, the screw constitutes to the fullest degree the first and most important acquisition ; simple, and when its design, dimensions, and its operation are well thought out, its per- formance is excellent. It is scarcely necessary to explain a propeller : it is a screw, or rather, there are two elements of the threads of this screw called the wings or Hades which screw into the air. If the screw were to be driven into wood or a metal nut, it would advance a certain distance with each revolution. This advance would be always the same, and is known as the " pitch," which is simply the distance separating two consecutive threads, this distance being computed parallel to the axis. But the propeller of an airship screws into the air, and the latter is an unsteady nut, so that with each revolution the aerial vessel, instead of advancing a distance equal to the " pitch," only moves forward a part thereof. The difference between the "pitch" of the screw and the advance of the airship itself for each of these revolutions, is defined as the slip of the propellers, that is the proportion of this difference and the " pitch " itself. Thus a screw may have a slip of f$ if, when it makes a revolution, the airship which it drives does not move forward more than ^ of the pitch of the propeller. This knowledge of slip enables us to consider the contro- versial question of large screws turning slowly, or of small screws revolving very rapidly, and we may understand readily that it is necessary, & priori, to reject the screws which are too small. Turning very rapidly they would drive away the immediately surrounding air without forcing the airship forward ; their enormous slip would not enable it to advance. It is as Colonel Renard expressed in a picturesque manner by saying, " We cannot propel an Atlantic liner by rowing, even very rapidly, with a penholder." Let us therefore take screws of large diameter. But then again one is limited in their dimensions by considerations of weight. As they turn power- fully but slowly, it is necessary to add to their individual 1 CONSTRUCTION AND MANAGEMENT 53 weight that of the speed-reducing gear, which transmits the always very rapid revolutions of the light motors used in aerostation. Consequently there will be an absolute limit to bear in mind, because it is necessary to choose between the efficiency of the propeller, that is to say the portion of motor effort which is transformed into useful tractive effort, and the engine-power. By augmenting the weight of the screws the efficiency of the propeller may be improved; but then it becomes necessary to increase the weight of the motor, and it must not be forgotten that in aeronautics the question of weight is always vital, and that in an airship only a total given weight is available for the whole of its mechanical equipment, motor and propeller. One other question now remains the position of the propeller. Should it be placed at the prow, at the stern, or amidships ? We have discussed this question already (p. 32) as well as that of determining the level at which it must be driven between the axes of the balloon and the car respectively. These principles being disposed of we will consider the propeller of the CUment- Bayard. Hitherto the screws of dirigibles have been made of sheets of light metal, bent and riveted upon metal frames; sometimes they were made of fabric stretched over a clumsy skeleton. The terrible disaster to the dirigible Rtpublique was attributable to one blade of the propeller so constructed being wrenched off the shaft by the centrifugal force, and, perforating the envelope, precipitated the vessel to the ground with its passengers. This accident demonstrated the urgent necessity for making the propeller absolutely solid. And experience has shown that wooden propellers, with the blades having the grain of the wood longitudinally, are the most satisfactory. The screw of the CUment-Bayard is of wood, and is a striking piece of work by Chauviere the engineer. It has only two blades ; as a matter of fact if the number of the latter were increased too greatly, each would move in air already displaced by its neighbour, and efficiency would be decreased. M. Chauviere thought it possible, by special arrangements, to balance the efforts of propulsion and the effects of centrifugal force arising from the rotary movement, 54 THE CONQUEST OF THE AIR efforts and effects which increase in a general manner pretty well in accordance with the same laws. The CUment- Bayard propeller is 5 metres in diameter. The pitch is variable and increases from the axis to the tips of the blades. It is built up of countersunk ribs assembled and superposed in the form of a fan, similar to the steps of a "winding staircase." Revolving at 350 revolutions per minute, each of the tips of the blades describes, in a circular path, 100 metres per second. This enormous "peripheral speed " is the maximum that has been attained so far with screws of this design. At this speed it produces stabilisating effects, called gyroscopic, recalling to mind those of the small device used as a toy known as the gyroscope, the stability of which, occasionally, is disconcerting. It seems to defy the laws of balance by maintaining simultaneously its rotating speed and the mass disposed around its circumference. In the case of the actual propeller its gyroscopic effects oppose strongly the pitching of the balloon, and therefore produce a stabilisating effect. This was the reason why the constructor did not strive too much after lightness in designing the propeller, which weighs 90 kilogrammes. At speeds of 350 revolutions per minute the CUment- Bayard propeller sustains with its blades a centrifugal effort exceeding 19,000 kilogrammes, and yet so perfect is its construction that it is not submitted to more than one- twentieth of its breaking strain. The independent speed of the balloon, driven by its motor and propeller, is 50 kilometres per hour; i.e., 14 metres per second. To complete our description let us add that the dirigible is always berthed in a shed which enables it to await, sheltered from heavy weather, favourable conditions for pend- ing journeys. The first shed was erected at Sartrouville, but a new shelter has been built near Meaux. HANDLING THE AIRSHIP : STARTING OUT : EN ROUTE ; THE DESCENT The handling of a dirigible balloon is not so simple as that of a spherical balloon owing to the elongated form of the envelope containing the gas, upon which depends the ascensional effort. CONSTRUCTION AND MANAGEMENT 55 First the dirigible must be brought out of its shed wherein it is held upon the ground by a considerable, imposed weight, comprising bags of ballast. A number of men draw up in two lines on either side of the balloon, in which the pilot and his assistant take their places. The men detach the ballast-bags carefully until the balloon evinces a very slight tendency to lift. Hauling with all their might, they bring it out of its dock, so holding it that it almost touches the ground. Arriving in the open air, it is hauled to as level an area as possible, and then again loaded with the bags of ballast, so that it rests naturally upon the ground. The pilot assures himself that all is in good order ; that the valves work, that the cords which control them are to hand, are not twisted or swollen; that the recording instruments work properly; that the wheels of the steering rudder and stabilisator efficiently govern those two mechanisms ; that his compass, his charts, his ballast are all to hand, as well as the cord which operates the ripping valve. Meantime the engineer has passed as minutely over his motor, seeing to the lubrication of all parts, the propeller shaft and bearings ; tests his indicators and recording instruments, and then when all is ready informs the pilot. The latter now instructs the men to swing the balloon round in such a way that it starts out " to leeward." The passengers embark, and the ballast is discharged little by little, until the balloon rises slightly ; this operation is called " weighing " the balloon. The pilot commands the engineer to start up the motor, but without coupling-in the propeller. When the engine is under way and all is ready, the navigator throws out the last bags of ballast so as to give the balloon the requisite lifting effort. " Hands off," he shouts. At this command the workmen release the sides of the car to which they have been clinging, and the balloon is now held by two ropes only, attached to the under side of the car by a "goose-foot" at front and rear respectively. These cords are then " paid out " equally, in such a manner as to keep the airship horizontal. When at last die pilot cries " Let go," the men drop these ropes and the vessel rises. The pilot orders the engineer to let in the propeller; the balloon attains its independent speed , 56 THE CONQUEST OF THE AIR and with a turn to make sure the steering mechanism is working properly, the pilot sets the course it is proposed to take. En route, if the weather is clear, the pilot always keeps his eye upon the chart, so as to assure himself that he is following the right course by comparison with the actual topography of the country unrolled beneath the feet of the travellers. If he ventures out at night, or in a fog, he will fix his attention upon the compass, while his assistant at the wheel of the stabilisator will not let his eye leave the barometer, so as to preserve by the manipulation of the elevator, the desired altitude of the balloon, without discarding ballast or letting out gas. With regard to the sensation of " wind " felt by travellers, this is only due to the independent speed of the balloon, 45 to 50 kilometres per hour. Whether it be a following, or a head, wind it will always be the same, neither more nor less intense, because the " surrounding " wind does nothing but carry the whole of the atmosphere, of which the balloon is a part, from one point of the earth to another. Travellers in the car are under the same conditions as if they, ran very quickly to and fro through the saloon of a large liner. The speed of their movement creates an impression of wind which is the same, irrespective of the direction and force of the wind, which blowing over the surface of the sea transports, in a combined movement, both them and the vessel in which they are sheltered. So far as concerns ascent and descent, this is effected within a small limit, about 100 metres, by the aid of the stabilisator. It must be pointed out that, unlike the free balloon, the ascensional effort of an airship is constantly increasing. Unballasting is continuously taking place through the con- sumption of the petrol by the motor, and in this manner it loses about 40 kilogrammes per hour. This is where the charging of the air ballonnet intervenes fortunately to secure the constancy of the external shape and consequently also the persistence of the air pressure. It is scarcely necessary to urge passengers in a dirigible to exercise the greatest prudence. Nothing must be thrown over- board, be it a bottle, an empty box, or even a chicken bone, CONSTRUCTION AND MANAGEMENT 57 without the pilot's permission : the static sensibility of these airships is extreme, and it is necessary to avoid any action which might vary it accidentally. As to the descent of an airship, at least in the majority of cases, it must take place only in the vicinity of a shed, descent carried at stem &>f ree the balloon CcCble fey which Ballast can be released. '/////w//////////////////////////////^ Fia. 25. Constructor Surcouf s method of mooring a dirigible The vessel surings itself nose to the wind, and the latter keeps the battonnet inflated automatically in open country being always hazardous. This was only too well shown in the accidents to the Patrie and the Zeppelin air- ships. Landing is made in a manner just opposite to that of ascent. But care must be observed that the men who seize the two guide-ropes to bring the balloon gently to earth at first grasp the " windward " rope so as to hold the balloon with its nose to the wind. Negligence of this precaution, and the balloon, held only by the stern rope, will rear up, owing to 58 THE CONQUEST OF THE AIR the wind driving against the prow, and thus imperil it. Once the balloon has landed the workmen seize it by the car, load it with bags of ballast, and then bear it gently into its shed. However, the airship might reach, be compelled to descend, and to " moor " by the aid of its anchors in open country. In such a case there is an arrangement conceived by M. Surcouf which appears to offer the greatest security to an airship forced to make a "halt" at a place unprovided with a special shelter. Beneath the body, and towards the front of the balloon leading to the ballonnet, is an automatic valve (Fig. 25) which opens like a purse. During the journey a spring keeps it closed, and the ballonnet works as usual by means of its charging fan. But if the vessel is compelled to stop, it is fixed to the ground by anchors, or by stakes and cable, which by means of a " goose-foot " is attached to the prow of the car, the balloon thus being held stationary, with its motor stopped, swinging in the wind. But under the influence of temperature fluctuations the gas will contract or expand, and with the motor no longer running, the ballonnet will not be able to maintain the invariable form of the envelope. Then, under the pulling action of the restraining cords, the "mooring" valve opens, always to the wind, since it is to the front of the balloon, which adapts itself like a weather vane, nose to the wind. Under these conditions the air so caught in the pocket forces the valve open, and thus keeps the ballonnet inflated to assure the permanency of its shape. One can, for greater security, attach bags of ballast to the stern rope. If the stern of the balloon should descend this ballast would strike the ground, and the envelope, released of a considerable weight, would rise again before it could come into contact with the earth and be damaged thereby. VOYAGES OF THE CLEMENT-BAYARD " The dirigible balloon which we have described in de- tail has completed more than thirty trips, with uniform success. During the Aeronautical Show held at the Grand Palais in the month of December 1908, it came and hovered CONSTRUCTION AND MANAGEMENT 59 above the Champs-Elysees repeatedly. Its evolutions over Paris have rendered it popular, familiarising every one with the appearance and travel of an airship. It has made numerous FIG. 26. Voyage of the CUment- Bayard (Nov. 1908) 250 kilometres in a complete circuit in five hours, without descent cruises around the capital, some very lengthy, but all brilliant, first under the direction of M. Kapferer, collaborator of M. Surcouf; later of M. Capazza, the eminent Corsican aeronaut, who so far has been the only man to cross the Mediterranean in a balloon. The most remarkable of these excursions was that when M. Clement resolved to set out from the airship shed to visit his seat at Pierrefonds (Fig. 26). The vessel left Sartrouville on November 1 at 11.15 A.M. in an east-south-east wind blowing 60 THE CONQUEST OF THE AIR at a velocity of 20 kilometres per hour. M. Clement, the owner of the balloon, was accompanied by a passenger ; MM. Capazza and Kapferer were on the bridge ; Sabathier the engineer, and a mechanician, were at the motor. The balloon passed successively over Maisons-Lafitte, Pierrelaye, 1'Isle- Adam, Beaumont, Creil (at 12.39), Pont Sainte-Maxence, Compiegne (at 1.28). It then wore round to the east and arrived at Pierrefonds at two o'clock ; thence it resumed its journey to Paris, by Rocquemont, Ermenonville, Chennevieres, Bourget (passed at 3.26), Pantin, described a large circular sweep overj Paris, and regained Sartrouville at eight minutes past four. The total distance was 250 kilometres, and it was covered in 4 hours 53 minutes. It was a remarkable record for a round trip accomplished by a dirigible without descent during its journey, and returning to its starting-point. The great journey of the Zeppelin described in the following chapter was not completed by return to the point of departure, inasmuch as the airship was destroyed unfortunately in the course of its homeward journey. Finally we may mention that in August 1909 the CUment- Bayard made a noteworthy journey with a commission of Russian officers aboard. The latter had been sent to France to investigate aeronautics for the purpose of facilitating the creation of a Russian aerial fleet. The airship was piloted by M. Capazza, who navigated the craft to an altitude of 1550 metres ! Such a height had never been gained previously by any dirigible. The official carrying capacity of this airship is as follows : 6 passengers, 300 litres of fuel, 20 litres of oil, 65 litres of water, 250 kilogrammes of ballast (sand in bags), and 59 kilogrammes of manoeuvring ropes. "AERIAL YACHTS" Such a dirigible as we have described is, in the realm of aerial navigation, the equivalent of a warship, or of a large mercantile steamship ; it is the " ocean liner." But its great cost (about 12,000), the absolute necessity of maintaining an immense and expensive shed, renders it a vessel of pleasure impossible to many amateurs for aerial trips. A " little CONSTRUCTION AND MANAGEMENT 61 dirigible," an " aerial yacht " at a more popular price, and more simple to control, was demanded. Such a convenient type of small balloon is now available, and is known under the generic name of the " Zodiac." This, to hazard a comparison borrowed from automobilism, is the " aerial voiturette." It is designed to enable one or two Valve. 'Envelope. Su spension attachment Elevating _ -PIIAJ*,?. - "^ Rudder. Empennage / Motor Pifot X 2. FIG. 27. A little "Zodiac" dirigible passengers to make jaunts into the air, and without the necessity of maintaining a sheltering shed. For this purpose the gas bag, of 700 cubic metres, is inflated, not with pure hydrogen, which is expensive and not always obtainable, but with coal gas, which is available at all towns and can be purchased cheaply. Inflated therewith it will lift one person, but by combining coal gas with about 100 cubic metres of hydrogen, it will lift two people. It is pisciform in shape, with stabilisating planes, and has two rudders. The car is detachable into three pieces ; each of the latter is formed of wooden trellis, light, flexible, and yet at the same time solid, the sections being fitted together by bronze sockets, nuts, and bolts. A water-cooled, four- cylinder, 16 horse-power motor drives through cardan shafting a stern propeller, which runs at about 600 revolutions per minute. The latter is of 2'30 metres diameter. The motor also actuates a fan which, through the medium of an air-ballonnet, maintains the permanent external form of the envelope. 62 THE CONQUEST OF THE AIR The whole balloon dismantled, motor, car and envelope, packed in canvas cloth, can be transported by horse and cart. The balloon is inflated at the point where the gas is obtain- able, and it can be prepared for an ascent in an hour and a half. This little airship can travel at a speed ranging from 25 to 28 kilometres per hour ; can remain aloft for three hours with 75 kilogrammes of ballast; and costs, ready for use, 1000. Truly therefore it is the aerial " auto," enabling trips to be made into the air without being compelled to return to a stationary shed, because the balloon coming to earth at the end of its journey can be deflated like a simple " spherical " and be loaded upon a cart for conveyance to the nearest railway station. This handy type of little dirigible certainly fulfils in every respect the " popular airship." On Easter Sunday, April 11, 1909, it made a remarkable journey. With MM. Henry de la Vaulx and Clerget on board, it manoeuvred above the Bois de Boulogne for three hours with the greatest ease, before the eyes of crowds of Parisians, which the beautiful weather had caused to flock upon their favourite promenade. During the summer of 1909 another vessel of this type, Zodiac III., slightly larger than the above (1400 cubic metres capacity), was utilised on a hunting trip by Comte de la Vaulx and M. Andre Schelcher. Furthermore, it carried out a number of remarkable ascents at Brescia and in Belgium, demonstrating its handiness, convenience, possibilities, and facilities, in regard to inflation and deflation. An airship of this type, but of 2000 cubic metres capacity, was presented to the French Government by the subscribers to Le Temps fund, after the disaster to the Rtpublique. This craft is now employed for the training of aerial pilots at the French Military Training College. IMPRESSIONS IN A DIRIGIBLE : DIZZINESS : SAFETY Now, questions which arise naturally in the mind of the reader, and asked of all who have travelled in a dirigible, are, What are the sensations ? Does one suffer from giddiness ? Has one sea-sickness ? Has one fear ? I will endeavour to reply to these interrogations. ! ts 2 Vi w "> g ^r 51 w "g O 5 CONSTRUCTION AND MANAGEMENT 63 On board an airship one has a feeling of complete security. Before entering the car there is time to take a walk round the balloon, for it is still berthed in its shed ; to examine with care every part ; to feel the lifting and suspension system. The whole is so solid ; is made of material of such perfect quality ; the total resistance is so well calculated and tested to twenty times what the whole will have to withstand, that in an instant every qualm of disquietude slips from the mind. The only hesitation one has is that of actually embarking. But the disasters to the Pax and the Bradsky balloons have been instructive. To-day the general utilisation of the air ballonnet secures stability ; the motor is placed well away from the balloon ; the suspension system is indeformable and distributes the weight equally over the envelope ; all parts of the motor capable of giving off either sparks or leakages of gas are boxed in or covered with metallic sheathing. Lastly, trained and experienced aeronants always conduct the ascents, for no owner of an airship would be mad enough to attempt a trip without the indispensable assistance of one of those " captains of the air," such as the Comte de la Vaulx, Capazza, or Kapferer, for example. Mal-de-mer is unknown aboard these airships, for the simple reason that the longitudinal stability being so very great there is neither pitching nor rolling. Many ladies have received the baptism of the air ; and not one has suffered from this terrible malady of which ocean vessels preserve, alas ! the unenviable monopoly. With regard to dizziness, this is unknown in a balloon when the latter is not held to the earth by a rope. Giddiness is produced when looking from the top of a tower, or the edge of a precipice, by the view of the vertical wall which drops below one's self, and which " conducting the eye " right down to the bottom, enables one to calculate the depth of the chasm. In the captive balloon the sight of the cable may sometimes produce the same effect ; but in a dirigible, there being no material connection, one cannot estimate one's altitude. One believes, and one actually is, above a magnificent plan in relief; with a feeling of beatitude which is grand ; with the impression indeed of being independent 64 THE CONQUEST OF THE AIR of all; to have broken away from one's bonds and to be the master of space. Consequently it is now possible to accomplish voyages by dirigible in the strictest sense of the word, and in absolute safety. I have made many myself, which I shall never forget, on board the CUment- Bayard. The time is not far distant when airships, in addition to their military utilisation, of which we will speak after we have described aviation apparatuses, will have applications to everyday life, without speaking of their employment in those geographical explorations which yet remain to be made. CHAPTER V HISTORY AND DESCRIPTION OF THE PRINCIPAL DIRIGIBLES EARLY DAYS OF AERONAUTICS : FROM GENERAL MEUSNIER TO COLONEL RENARD, GIFFARD, DUPUY DE LOME, TISSANDIER : M. HENRY DEUTSCH, COUNT ZEPPELIN, M. SANTOS-DUMONT AND M. LEBAUDY THE PIONEER : GENERAL MEUSNIER, INVENTOR OF THE AERIAL PROPELLER THE history of dirigible balloons, up to recent times, has been somewhat devoid of results. If the importance of what has been done is unquestionable, it can be asserted at least that the quality in this case substitutes quantity, since it was no farther back than 1852 that the first serious attempt in this direction was made by Henry Giffard. Before him there may have been some ideas more or less vague, but nothing tangible. However, it is one of these projects which it is necessary to describe, and that with some detail, because of its importance, its far-reaching value, and the date of its conception. It is that made in 1784, scarcely one year after the discovery by the brothers Montgolfier, by an engineering officer Lieutenant, subsequently, General Meusnier. Meusnier was a prodigy. He astonished his masters by his precocity, by the confidence of his reasoning, and by the perspicacity of his views. He was made a member of the Academie des Sciences at twenty-nine, on account of his work in aerostation, which however was only one of his accomplish- ments, for he was the collaborator of Lavoisier in several experiments. He was killed at the siege of Mayenc in 1793 ; he was therj General, 65 B 66 THE CONQUEST OF THE AIR Meusnier was the true inventor of aerial navigation, and was a " scientific " initiator. Through not following the lines which he laid down, aerial navigation lost a century groping about fatuously; in conducting experiments abso- lutely without method. In fact, at a time when relatively nothing was known concerning the science of the atmosphere, Meusnier had the distinction of elaborating all the laws governing the stability of an airship, and calculating the conditions of equilibrium for an elongated balloon, after having demonstrated strikingly the necessity of such elonga- tion. Meusnier's designs and calculations are preserved in the technical engineering section at the French War Office in the form of drawings and mathematical formulae. His airship designs relate to two balloons, one very large, the other much smaller, and it is in these projects that one finds described distinctly two absolutely new arrangements which are in universal use to-day : the air-ballonnet to secure stability and the screw for aerial propulsion. With regard to the motive power, owing to the absence of suitable motors in his day, he contented himself with the use of the muscular power of the men carried on board. The dimensions of his largest balloon (which, however, was never constructed) were 260 feet in length, and 130 feet in diameter; that is to say 85 and 42*50 metres respectively. The shape was that of an ellipse, and as one may see, the elongation was equal to twice the diameter. The cubical contents were to be 60,000 cubic metres. Thus the balloon (Fig. 28) would have followed the form of a perfect ellipsoid, which was the paramount development to be realised as compared with the spherical form. It was to be a double envelope, comprising two skins, each of which was to fulfil a distinct purpose. The first, the " envelope of strength," very resistant, was consolidated by bands. The second, placed within the former, was to be impermeable to* the light gas which was to sustain it. This inner balloon was never to be inflated fully, and the space between the two envelopes was to receive, in varying quantities, the ^air to be forced thereinto through pipes by two pumps carried in the car ? This was ia very truth the air-lcdlonnet, and its use HISTORY AND DESCRIPTION 67 without doubt was to maintain invariability of the external shape. The car was to be attached to the envelopes by a triangular suspension system. This was the " indeformable suspension " which to-day is considered imperative, and which is adopted universally. The lifting system was to be attached not to a ^Kope barid from which I car is suspended Prow Air pipes. Rudder. Car. Air pump. FIG. 28. The first dirigible, designed by General Meusnier (1784) net, but to a girth sewn to the fabric. Moreover, at three points where the lifting rope members met, forming " suspen- sion knots," the axes of the three propellers were fitted, which Meusnier described as " revolving oars " (rames tournantes) and which were no other than screw propellers. Consequently this remarkable system, which is now used for driving steam- ships, was invented in 1784 for aerial navigation and by a Frenchman at that. But that was not all. Meusnier not only recommended the elongated form ; not only conceived 68 THE CONQUEST OF THE AIR the girth fastening ; the triangular suspension ; the air ballonnet ; and screw propeller ; but moreover indicated the point at which the last-named should be installed. It may be observed in the diagram that the motor shaft is not connected to the car, but is placed between the latter and the balloon. In this way the illustrious and accomplished officer laid down everything requisite for aerial navigation. For this reason he deserves justly the distinction of being the fore- runner, the initiator, of aeronautics. We are indebted for this information to a remarkable memoir of the engineering lieutenant Letourne, which was presented to the Academie des Sciences by General Perrier in 1886, wherein these details are set forth in a very scientific manner. THE FIRST MOTOR BALLOON : GIFFARD'S AIRSHIP (1852) It was some sixty years later that the problem was first resolved practically, by an eminent engineer whose name is justly celebrated Henry Giffard, the inventor of the " Giffard injector," used throughout the world in connection with the boilers of locomotives. Giffard was convinced of the im- potency of the " human motor," and its excessive weight, and he conceived the bold idea of carrying a steam-engine complete with boiler and propeller under an elongated balloon. One shudders in thinking of the courage of this man who ventured to carry an incandescent fire immediately beneath his balloon inflated with hydrogen. But the many precautions which he adopted ensured him of safety. The shape of his balloon was of a symmetrical cigar, pointed at both ends (Fig. 29). Its length was 44 metres, diameter 12 metres, the elongation thus being in the propor- tion of 3*5 to 1. Its volume was 2500 cubic metres, and it was inflated with coal-gas which gave him a lifting power of 1200 kilogrammes. The steam-engine, including boiler, weighed 159 kilogrammes, and developed 3 horse-power, giving a weight of 53 kilogrammes per horse-power. It was at that time a noteworthy achievement. The engine was inverted, to reduce the risks from fire, am} was mounted on a platform HISTORY AND DESCRIPTION 69 attached by six ropes to a " strengthened beam " supported by slings connected to a net which covered the whole of the balloon except on its under side. This suspension, one can see, had the drawback of being possible of displacement. Moreover, the absence of the ballonnet did not secure Prow Stern FIG. 29. Henry Giffard's steam-driven balloon (1852) Though this vessel never accomplished a complete circuit, yet it was able to deviate from the direction of the wind, and demonstrated the "possibility " of steering balloons permanence of the envelope's exterior form. On the other hand, the use of the long pole had the advantage of dis- tributing the strain upon the whole of the aerostatic envelope in a pretty uniform manner. At the stern a triangular sail, manoeuvred from the car, formed the rudder. With this balloon Giffard carried out some experiments of the greatest value. True, the low independent speed (3 metres per second) which he obtained, in conformity with his calcula- tions, did not permit him to describe a circle in the air : but he 70 THE CONQUEST OF THE AIR was able to make some very neat evolutions, deviating at his desire from the direction of the wind, thereby testifying to the efficiency of his rudder. In a word, he succeeded in demon- strating, in an experimental and unquestionable manner, the possibility of aerial navigation by the aid of an airship furnished with a motor and a screw. Consequently, his efforts belong rightly to the history of aeronautics. DUPUY DE LOME'S DIRIGIBLE (1872) It is necessary to wait another twenty years to see a second rational effort in aerial navigation. This was made by the illustrious marine engineer, Dupuy de Lome, the inventor of the ironclad. Struck with the value of balloons during the siege of Paris, Dupuy de Lome thought that this utility could be doubled if one were able, not only to leave the besieged capital as did the free balloons, but to return again at will ! So he set to work to perfect a dirigible free from the disadvan- tages of Giffard's. Notwithstanding the excessive weight of the human motor, he decided to rely upon the muscular energy of the passengers to move his screw, so as to avoid the dangers of the steam- engine. The balloon was fusiform, symmetrical, and pointed at both ends. Its length was 3 6- 50 metres, diameter 14-84 metres, giving an elongation equivalent to 2' 5. The volume of the envelope was 3450 cubic metres. In the interior of the latter was placed an air-lallonnet ; this, in short, was the first time that Meusnier's conception was acted upon. The volume of this ballonnet was a tenth of that of the balloon. But Dupuy de Lome did not pin his faith, in the use of the ballonnet, to the lines set forth by General Meusnier. He adopted the indeformable triangular network suspension. The screw weighed 75 kilogrammes, was 9 metres in diameter, and was driven by eight men. Under these conditions the stability was perfect, and in still air the balloon was able to travel at a speed of 2*25 metres per second very nearly 8 kilometres per hour. Conceived and designed during the siege of Paris, the balloon was not built until 1872. It did no more than start at Vincennes, on February 2, 1872. Notwithstanding a violent 6 3 M fc ^ BE ^ r/i *" "9 2 ' c ri "C-a HISTORY AND DESCRIPTION 71 wind, the stability was perfect, owing to the triangular suspen- sion, and the airship was able to deviate 1 2 degrees from the wind's direction. This test had the merit of denning the essential points for the construction of dirigibles, and to show the possibility of obtaining, while travelling, an absolutely perfect stability. DIRIGIBLE BALLOON OF THE BROTHERS TISSANDIER (1883) Impressed by the qualities and regular working of the electric motor, and the absence of danger which attended its use, MM. Albert and Gaston Tissandier in 1883 built a dirigible airship driven by an electric motor, for which the energy was supplied from a bichromate of potash pile battery. The balloon was fusiform, symmetrical, with the two ends pointed, and having an elongation equal to 3 ; its length was 28 metres, greatest diameter 9*2 metres, and its volume 1060 cubic metres. The netting, the cords and the knots of which, by their projection, offered such resistance to movement, were replaced by a suspension " cover." The very light screw weighed no more than 7 kilogrammes, and was set 10 metres from the balloon. The motor (a Siemens dynamo) weighed 55 kilogrammes for a motive effort of 1 J horse-power ; electricity was furnished by four batteries, of which each comprised six compartments, each forming a pile element. The reservoirs, raised or lowered at will by a system of pulleys, connected or disconnected the liquid exciter, which was an acid solution of bichromate of potash. After a preliminary trip in October 1883, the balloon sailed for so long as two hours at an independent speed of 4 metres per second, in September 1884: it was not able to go against the wind, but was able to complete numerous evolutions to the right or left of the direction of the latter. Stability was defective, owing to the absence of the ballonnet. Be that as it may, the Tissandier balloon was the first dirigible driven by electricity ; it opened a way which could be followed, and which might lead towards the definite solution of the problem of aerial navigation. 72 THE CONQUEST OF THE AIR CAPTAINS RENARD AND KREBS' BALLOON "LA FRANCE" (1884 AND 1885) It was about this time that Captain Renard, director of the military aeronautical establishment at Chalais-Meudon, in colla- boration with his brother, Captain Paul Renard, and Captain Krebs, built a vessel which combined in its new lines all indis- pensable features, and which realised all necessary requirements as much in the aerostatical as in the mechanical parts. This balloon is indisputably the starting-point of practical aerial navigation, and it has served as a model to all who have followed. Moreover, those who have digressed from the lessons furnished thereby have counted nothing else but failure. This pisciform balloon (Fig. 30), with its larger end in front, was 51 metres long and 8-40 metres in maximum diameter, which represents an elongation equal to 6. Its volume was 1864 cubic metres. The envelope, of varnished Chinese silk, was built up of longitudinal gores converging towards the two points. The network was replaced by a " cover " formed of bands of transversal widths of silk sewn together at their edges, and so cut out as to follow the " geodesical lines " of the surface. The triangular suspension advocated by Dupuy de Lome was discarded in favour of two oblique " cross-pieces " connecting with the front and rear of the car, and with the balloon cover suspension; those in the centre were parallel with them, and directly carried the car. The vertical steering rudder was placed at the stern. It was a lath framework strengthened by two diagonals, and covered with a double sheathing of silk stretched to form its surface. At the rear of the car, moving about a horizontal axis, was an " elevating rudder " which inclined to the front or to the rear, enabling the balloon to be given an ascending or descending movement. The design of the car was new entirely ; its great length recalled the oar-propelled yawls used in regattas. It was built up of bamboo trellis, had a length of 32 metres by 1*30 metres broad, and a maximum depth of 1*80 metres. Its great length is copied to-day in the most successful diri- gibles, such as the Ville de Paris and the CUment- Bayard. A HISTORY AND DESCRIPTION 73 " cabin," containing the motor and all necessary control, was placed forward. The motor, built by M. Gramme, weighed 96 kilogrammes, and developed 9 horse-power. The energy was transmitted through a hollow shaft, the bearings of which were fixed to Prow. Envelope tf Ballonnet Stern Balloon Screw. Bamboo car. Hotor & pilot position. FIG. 30. The balloon La France, designed by Captains Renard and Krebs (1884) two flexible suspensions, to a screw placed at the proiv of the vessel. This arrangement is likewise reproduced to-day in our most modern dirigibles. The screw was 7 metres in dia- meter, with a pitch of 8*50 metres, and weighed 40 kilogrammes: it made 50 revolutions per minute. The electrical generator comprised a " chromium chloride " battery invented by Colonel Renard and was of extreme light- ness. Each element was formed of a glass tube in which was a very thin platinum-silver electrode, in the centre of which was a zinc rod. The total weight of this accumulator was 400 kilogrammes, which represented 44 kilogrammes per horse-power. The independent speed of the airship with this power system was 6*50 metres per second. The first ascent took place at Chalais on September 12, 1884. The balloon manoauvred with the greatest ease and returned under its own power to the starting-point. This was a decided triumph, echoed throughout the world. Three further ascents were made in the same year to tune up the 74 THE CONQUEST OF THE AIR apparatus. Then in September 1885 two historical ascents were held in the presence of General Campenon, Minister of War. La France left Chalais, described several evolutions over Paris, and returned to its shed under its own power : the first round "aerial voyage" there and lack was completed (Fig. 31): aerial navigation became an accomplished fact, the " highway of the air " was opened and aeronauts only had to fly. THE ERA OF THE " EXPLOSION " MOTOR : M. HENRY DEUTSCH : M. SANTOS-DUMONT'S EXPERIMENTS The Chalais-Meudon balloon was consequently the marvel of its day, and undoubtedly with electric motors it was difficult to advance farther in this direction; but anew mechanical engine had appeared creating a new industry and revolu- tionising the art of transportation. This was the "petrol motor." One man contributed as much by his efforts and his personal action as by his generous encouragements to popu- larising its exclusive use for aerial navigation. This was M. Henry Deutsch de la Meurthe. So soon as it was perfected he undertook the important task of showing the part the explosion motor was destined to fulfil. It was driven by that marvellous accumulator of energy petroleum spirit. From his youth he had been consumed by one obsession the solution of aerial navigation. When he saw what Colonel Renard had done by the use of the electrical motor, he conceived the idea of pressing the petrol engine into aeronautical service, and as far back as 1887 demonstrated to the officers of Meudon the possibilities there were in extending their efforts towards this end. At the same time he ordered the constructors Mignon and Rouart to build an explosion motor upon the new lines, and in 1889 showed President Carnot the first petrol motor-driven carriage. Always reverting to his idea of steering balloons, he accordingly undertook to furnish the financial and material means to demonstrate the possibilities of the petrol motor in connection with aerial navigation. After expending considerable sums in actual research, he unhesitatingly offered numerous prizes to encourage the efforts of aeronauts and aviators. The " Deutsch prize " of 4000 certainly contributed much to stimulate their HISTORY AND DESCRIPTION 75 enthusiasm, and it is only an act of justice and acknowledg- ment to place the name of M. Henry Deutsch at the forefront of contemporary aeronautical history, the many conquests in StCIxmd Sevres Journey made Sept: 22. 2885. Journey made Sepl.23. 1885. Clamant FIG. 31. The first two aerial voyages in a closed circuit made by La, France over Paris in 1885 which are undoubtedly due to the exclusive use of explosion motors. It was M. Santos-Dumont who, on October 19, 1901, won the Deutsch prize, the conditions of which consisted in setting out from St. Cloud, doubling the Eiffel Tower, and returning to the starting-point within half-an-hour (Fig. 32). With an indomit- able perseverance, an unheard-of audacity carried to intrepidity, the young Brazilian aeronaut built dirigible after dirigible, some large, some small, some medium, and at last, after ten times escaping death narrowly, he succeeded in carrying off the much -coveted prize. His name became deservedly well known, more especially as a little later he lifted the first " Deutsch 76 THE CONQUEST OF THE AIR prize " for aviation. The airship with which he carried off the former trophy, the Santos-Dumont No. 6, had an elliptical envelope of 33 metres length by 6 metres diameter, and a volume of 622 cubic metres ; there was an air-ballonnet of FIG. 32. Route and altitude map of Santos-Dumont's journey (Deutsch prize, October 1901) 60 cubic metres capacity, and his motor developed 16 horse- power. Once the movement in favour of aerial navigation was started, it extended rapidly ; on all sides surged inventors, not always alas ! sufficiently proficient in theory or practice ; not always prudent ; not always profiting by the lessons given by their illustrious predecessors. The Brazilian Severo d' Albuquerque met his death in 1902 through his balloon exploding owing to the lack of foresight in the installation of the motor; in the course of the same year, 1902, the engineer Bradsky was killed, together with his companion Paul Morin, through the defective character of the suspension of the dirigible, which, notwithstanding Colonel Renard's recommenda- tions, did not include the ballonnet. THE "LEBAUDY" BALLOON. LA PATRIE" These catastrophes did not damp the ardour of aeronauts. But they made them more careful, and led them to realise the necessity there was for them to be grounded thoroughly in all HISTORY AND DESCRIPTION 77 questions touching aeronautics, if they desired to venture to build and test a dirigible. So in 1902, when MM. Lebaudy Rudder. Vertical plane,. Srabilisator frame Car at Twin, screws ; Vertical keel, stabilisator FIG. 33. The dirigible balloon Lebaudy (side elevation) decided upon the construction of a huge airship, they secured the collaboration of a distinguished engineer, M. Juillot, and "Rud'dcr Frame o stabilisator Surface of Horizontal tail fin Supporting Beam. FIG. 34. The dirigible balloon Lebaudy (underside plan) entrusted its erection to one of the most skilful " builders," M. Surcouf. The Lebaudy balloon (Figs. 33 and 34), which the Parisians promptly christened the " Jaune " (yellow) owing to the colour produced by the coating upon the external surface of its envelope, measures 58 metres long by 9*80 metres master diameter: its elongation is consequently 5*6, while its total volume is 2300 cubic metres. It is dissymmetrical, the 78 THE CONQUEST OF THE AIR greatest diameter being forwards, and it is pointed at both ends. The body of the balloon is not completely " round," the lower part being truncated to form a flat plane surface resting upon a frame serving as the suspension medium for the envelope and the car. At the same time, the flat form of this framing acts as a " stabilisating plane," which is efficient in use. Under this frame is a " strengthened girder," which, covered with fabric, forms a vertical stabilisating plane extended into a veritable bird's tail, a stabilisator in itself, and which terminates in the rudder. The car is short, and the motor which is carried therein transmits its power to two screws of 2*44 metres diameter, one being three, the other two, bladed. The propelling effort is exerted therefore not at the extreme front, as in La France, or at the rear as in the Santos-Dumont , but about amidships. The short length of this car renders difficult the uniform distribution of its weight upon the envelope : also the latter has a peculiar " saddle form ; " it is hollowed towards its centre in the manner of a saddle, due to the weight of the car imposed upon the central part of the envelope. This arrangement has its disadvantage in this sense, that the general form of the balloon is altered, and in practice does not conform to the principles which have served in determining the theoretical conditions of equilibrium and of propulsion. It is just to add that the efficiency of this balloon is remarkable. The air- ballonnet is divided into three compartments, to prevent the heavier air surging towards the base in case the airship becomes tilted, and has a capacity of 5 cubic metres. The motor is of the Mercedes type, and develops 40 horse-power when running at 1 2 00 revolutions per minute. An acetylene search- light of 100,000 candle-power, mounted with a projector, facilitates landing at night. After a magnificent series of triumphant flights made in 1904, in the following year MM. Lebaudy offered this magnifi- cent dirigible to the French Minister of War, who sent it to Toul. The State then decided to order a dirigible of the same " semi-rigid " type ; this was La Patrie. Save in some details, La Patrie was identical with the lebaudy. Its volume was increased some 200 cubic metres HISTORY AND DESCRIPTION 79 by extending the length by 2 metres; the ballonnet was 650 cubic metres instead of 500, and the motor built by Panhard and Levassor developed 70 as against 40 horse-power. Lastly, instead of ending in a point the stern was rounded and fitted with a cruciform empennage for the purpose of securing still greater stability. An elevator of two projecting planes was fixed to the front of the horizontal stabilisating framework. Otherwise it was a sister airship to the Lebaudy. The life of the Pcutrie was brilliant but short. After it had demonstrated its exceptional features such as no other airship had shown up to that time, after it had travelled under its own power from Paris to Verdun in seven hours without any inci- dent on November 23, 1907, this magnificent dirigible some days later was caught in a gale which forced a descent. Despite the efforts of 200 soldiers the wind catching its enormous broadside surface tore the balloon from their hands, and bore it away in the storm. It passed over France and England, dropping pieces of its motor at different points on English territory, and disappeared into the North Sea, where it was perceived, still inflated, some days after the accident. A new balloon of the same type, the Rtpublique, was ordered by the French Government from MM. Lebaudy for national defence. The Rdpullique presented some striking features : the impermeability of its envelope permitted it to remain inflated 110 days with one charge of gas. Its first flight, made in September 1908, lasted six and a half hours, and it covered over 200 kilometres in a closed circle. After the CUment- Bayard this was the most striking record of a complete trip without descent, and with return to the starting-point. The characteristics of the Rtpublique were the same as those of La Patrie as well as the arrangement of the motor and empennage. The Rtpublique had been " militarised," and had been commis- sioned for the defence of the eastern frontier of France, when an accident supervened, to which we refer in another chapter, cutting short the career of this magnificent airship. Owing to the sudden breakage of one of the propeller blades, the latter, impelled by the centrifugal force, crashed into the envelope, piercing it through and through, and precipitating the airship to the ground with its four officers, Captain Marchal, Lieutenant 80 THE CONQUEST OF THE AIR Chaure, and Adjutants Reau and Vincenot who were killed by the awful fall. Several new military balloons, on similar lines to the Bdpublique, or the Bayard-Clement, are under construction the Liberte, Capitaine - Marchal, Lieutenant - Chaure, and General Meusnier, among others, while large "aerial cruisers" of 6000 cubic metres capacity will be put into commission shortly. BALLOONS WITH HOLLOW STABILIZATORS : M. DEUTSCH'S " VILLE DE PARIS " : M. CLEMENT'S "BAYARD" M. H. Deutsch de la Meurthe had not remained idle all this time. Not content with merely having encouraged aeronautics, he wished to become a militant himself: he therefore had an airship constructed after the designs of M. Tatin. This vessel, not giving the expected results, he ordered a second in 1906, and for this secured M. Surcouf, who had become instilled with the ideas of Colonel Renard. For the first time an empennage of inflated ballonnets, which we have already described in dis- cussing longitudinal stability, was used. The body of the balloon (Fig. 3 5) is pisciform, with the master-diameter towards the front. The stern is connected to a cylinder carrying the stabilisating ballonnets. Its length is 60-50 metres ; maximum diameter, 10*50 metres; volume, 3200 cubic metres. The car, lattice-work of metal tubing, is 30 metres long, and of the " trussed girder " form. The ballonnet, divided into three compartments, has a volume of 500 cubic metres, and two rudders are attached to the car, one for steering laterally, and the other for ascent and descent. The 70 horse-power motor drives a two-bladed propeller 6 metres in diameter, running at 900 revolutions. The screw, placed at the prow in conformity with the ideas of Colonel Renard, makes, through a reducing gear, 180 revolutions per minute. This huge airship has accomplished several successful flights, and it was on board this vessel that the Prince of Monaco, the eminent and scientific navigator, who has surveyed and sounded the ocean, received the " baptism of the air," the highest altitudes of which previously he had explored scientifically in mid-Atlantic by means of " sounding balloons." HISTORY AND DESCRIPTION 81 I .3 I 82 THE CONQUEST OF THE AIR After the catastrophe which destroyed the Patrie, M. Henry Deutsch made a patriotic, generous offer ; his balloon was ready ; he submitted it to the French Minister of War to take the place of the lost airship, and the Vilk-de-Paris set out from Paris to Verdun, under its own power, to replace the FIG. 36. Journey of the VUle-de-Paris from Sartrourille to Verdun ; J January 15,1908) wrecked dirigible. This voyage was made on January 15, 1908 (Fig. 36). During the exploits of M. Deutsch's balloon, M. Clement, one of the best-known automobile builders, ordered from M. Surcouf a dirigible of the same type, but a little larger the CUment-Bayard. We have described it in detail already. A new airship, the Ville-de-Bordeaux, has recently issued from the Surcouf works, and its features appear to be in no way inferior to those of its contemporaries. Finally must be mentioned the dirigibles of the Zodiac type, which have given such good results. To-day the Zodiac is made in three models of 1200, 1400, and 2000 cubic metres capacity respectively. FOREIGN DIRIGIBLES : COUNT ZEPPELIN'S AIRSHIPS The attention of the Germans was drawn quickly to the gigantic progress in aeronautical travel effected in France. They at once foresaw its military applications, and anxious not to be left behind, resolved to excel the French constructors in the building of a gigantic airship " colossal " as it is collo- quially called in Germany. It was Count Zeppelin who, with a dogged perseverance, an ardent patriotism, which one cannot HISTORY AND DESCRIPTION 83 84 THE CONQUEST OF THE AIR but admire, concentrated his knowledge, his life, and his fortune, to the fulfilment of this idea. Moreover, his enterprise was sustained not only by H.I.M. Emperor William II. and by H.I.M. the King of Wtirtemberg, but also by national enthu- siasm: he was advised by those admirable meteorological aeronauts who grace German science, and among whom figure Hergesell, Assmann, Berson, &c. Conceiving an immense dirigible, Zeppelin sought to secure indeformability or rigidity by construction. He designed a gigantic airship 136 metres in length by 11-70 metres in diameter, and with a capacity of about 12,000 cubic metres. Its form was of a cylinder with pointed ends, the elongation being equal to 11 (Fig. 37). Kigidity was secured by means of a metallic framework, in aluminium, which not only gave to the system the rigidity much sought after by its inventor, but enabled him to divide the huge cigar into numerous compartments : 17 in all. Each of these was 8 metres long, except those 5 and 13, which corre- sponded to the two cars, and which were not more than 4 metres in length. The rigidity of the skeleton was secured by trans- verse partitions formed of cross-bracing covered with fabric. It will be seen that this balloon was not provided with a ballonnet. Each compartment contained a balloon of india-rubber fabric partially inflated (nine-tenths only); the inflation of these 17 balloons was a lengthy and difficult operation. The whole of the skeleton was covered with stretched fabric. The two cars were attached to the balloon in a rigid manner, and connected by a bridge, along which a counterweight travelled. The two motors were of 170 horse-power, and drove four propellers of 1*30 metres diameter, running at 800 revolutions per minute. Such a mass is difficult, if not impossible, to handle upon the ground ; so its home was a floating shed, anchored upon Lake Constance. This " dock," held only at one end by a powerful hawser, swings itself round under the action of the wind, so that the entrance is always to " leeward " for the emergence of the balloon. Such is or rather such was the first aeronautical monster. The German military authorities, as a condition of its definite HISTORY AND DESCRIPTION 85 acceptance, demanded the accomplishment of a trial trip of twenty-four hours " without descent or replenishment of fuel tanks, &c." It was during the summer of 1908 that this balloon, the fourth built by its learned author, attempted this official journey. After several short flights, carrying suc- cessively the King of Wiirtemberg, the Queen, and some royal princes, the Zeppelin set out on August 4, 1908, from its shed at Friederichshafen. There were twelve passengers on board. At 6.45 in the morning it rose above the lake and set a course to the west ; it passed over Basle, where it veered round to the north ; over Mulhouse and Strasburg, where the clanging of church bells and the salvoes of artillery greeted its passage ; at 2.45 P.M. it was over Mannheim, when, before reaching Mayence, there was a slight " mishap." The fault repaired, the balloon resumed its journey, passing over Mayence during the night, and the return journey was commenced. At 6.30 A.M. it was approaching Stuttgart, but when some miles south of this town another mishap necessitated descent. Here a squall struck the balloon, and from a cause still but little explained the immense airship was completely destroyed by fire in a few moments ! This was a national loss to Germany, and in a magnificent outbreak of patriotism a public subscription raised in a few days the millions of marks necessary to replace the aerial vessel. Such is an example to be followed. During the erection of a new airship Count Zeppelin re-commissioned Zeppelin No. III. Yet Zeppelin No. IV. accomplished a magnificent perform- ance : its voyage of August 4 and 5, 1908, covered, as a matter of fact, 606 kilometres, with two descents, and represented an actually travelling sojourn in the air of twenty hours forty-five minutes. With the new Zeppelin the record for duration and distance was excelled on May 31, 1909 1100 kilometres in thirty-eight hours ! Unfortunately the difficulty of handling such a mass as this again proved disastrous, for the airship came to grief against a tree. Despite its injury it was able to return to its shed after completing this noteworthy journey. This second accident was followed by the destruction of a third Zeppelin. On June 29, 1910, the monster of this series of rigid balloons, the Deutschland, of 19,000 cubic metres, 86 THE CONQUEST OF THE AIR 148 metres long, and driven by three motors developing in the aggregate 330 horse-power, giving a speed of 55 kilometres Strasboug WURTEMBERO FlG. 38. Voyage of the Zeppelin, August 4 and 5, 1908 606 kilometres were covered when the airship was destroyed per hour, was launched. But this, like its prototypes, met with disaster. It became stranded in a forest and was totally destroyed. In the month of September 1910 a fifth balloon of this type came to grief. Such practically demonstrates the fallibility of the rigid system. HISTORY AND DESCRIPTION 87 The future of the dirigible is undoubtedly in the " supple " airship. PROGRESS OF MILITARY AERONAUTICS IN GERMANY : THE THREE ZEPPELINS, THE PARSEVAL, THE GROSS AIRSHIPS : THE GRAND MANOEUVRES AT COLOGNE But German military aeronauts were not dismayed. Through the enthusiasm of the nation, the patriotism of its representatives, the initiative and enterprise of Emperor William II., a whole aerial military fleet was constructed, not entirely after the Zeppelin lines, but also with the supple or semi-rigid types, evolved and built by two famous German officers, Majors von Gross and von Parseval, after whom the respective airships are named. The Gross airship follows closely the designs of the Patrie or the Rtpullique, the empennages and the tapering of the stern of which have been adopted. This is a remarkable vessel, and has made a trial trip of thirteen hours without descent. With regard to the Parseval, it is one of the most perfect expressions of modern aeronautics, not only on account of its design, but owing to its striking efficiency. The Parseval is a beautiful and well-thought-out piece of work ; everything is the outcome of experience. The car has a suspension combining the advantages of the parallel and the triangular systems. Two ballonnets, placed respectively fore and aft, one of which deflates while the other inflates, have their envelopes guided by internal pulleys as shown in Fig. 40. Not only do they serve to secure the permanency of shape, but the difference in weight brings into play one or the other to assist the elevating rudder to secure the inclination of the balloon in any direction. Lastly, the propeller is quite an interesting piece of work. When stationary its blades, composed of fabric stretched tightly over a flexible framework, fall limply lengthwise upon the frame supporting the propeller. But when the latter is set revolving the blades open out. Under the combined action of centrifugal force and the resistance of the air, the wings assume the best disposition from the point of efficiency. Undoubtedly the Parseval is a marvel of modern aeronautical construction. 88 THE CONQUEST OF THE AIR The German army has at its command thirteen dirigibles. Three are Zeppelins of 15,000 cubic metres each, while there are FIG. 39. Voyage of Zeppelin III. in a complete circuit (April 1909) several Gross and Parseval vessels respectively. And if the Zeppelins are not of practical use, on the other hand the Gross Stern ballonefc / (fzlled) Forward ballonefc (empt/) Steering rudder. air pipe Car FlQ. 40. The German dirigible Parseval The suspension system is both parallel and triangular, and the two battonnets, operating independently, are able to meet any ascensional inclination movements of the balloon and the Parseval are military engines of the front rank. Not only are these balloons kept ready for instant action, but, moreover, there are large sheds which can harbour several HISTORY AND DESCRIPTION 89 machines at the same time. At Cologne, where the grand manoeuvres, especially for dirigibles, were held in October 1909, one shed in particular held simultaneously a Zeppelin, two Gross, and two Parseval vessels. Similar sheds have been provided at Metz, Aix-la-Chapelle, and at other points on German territory. But that is not all : stores, large depots, have been estab- lished where are held in reserve from 15,000 to 20,000 steel cylinders charged with pure hydrogen under high compression. These cylinders are carried in special railway cars, so that upon receipt of a command for " service " they can be attached to the first express train travelling in the direction of the point where the hydrogen is required. With a train of this description it is possible to inflate a Zeppelin in a very short time. Finally a corps of more than two hundred aeronautical officers has been formed. The latter have been drawn from various branches of the service ; even from the navy. Carefully selected, highly trained, they constitute an aerial staff of first- class efficiency. In addition to these military airships, always ready for service, there is the German aerial fleet which can be mustered from among private owners. It is possible to rely upou fifteen excellent dirigibles in case of war. This secures a combined effective aerial fleet of twenty-eight vessels available to German military aeronautics in case of hostilities. Germany, despite its unique position, is not to be lulled into a false sense of security. In addition to the Zeppelin, the Gross, and Parseval, there is a fourth type. This is the Rutherriberg airship. Well designed by its authors, it is characterised by the use of a long " trussed girder " carried directly under the envelope, and which supports the car or cars, according to the dimensions of the vessel. Thus it is possible to realise the magnificent effort which Germany has made in the direction of dirigibles. If France had the honour of " discovery," Germany had the foresight to " profit." Germany certainly occupies first position in respect of airships. For France to be overtaken by its neighbours after the former had shown the way in 18 84-1 8 8 5, is a curious 90 THE CONQUEST OF THE AIR situation indeed. Happily France has the aeroplane. In this latter phase no country has yet surpassed or even equalled our neighbours across the Channel. The French aviating officers astonished the world at the Picardy manoeuvres, and the French by means of their aeroplanes and their aviators are the unrivalled " masters of the atmosphere." ENGLISH, ITALIAN, AND BELGIAN DIRIGIBLES In England military aerostation has been represented by the construction of the airship Nulli Secundus. The career of this dirigible was short, but no doubt we are following progress in the new science minutely so as to effect something striking in a single move. It led to the construction of the Morning Post vessel for the nation at the Lebaudy shops, which was driven over to London by M. Capazza. In Italy the military aeronautical service has evolved an airship which is in every way remarkable, and which, as we shall see in a moment, has one of the highest coefficients of advantage among dirigibles actually existing. This balloon, known as 1-lis, is pisciform. Its total volume is 3500 cubic metres. The envelope is divided into seven compartments. The volume of the ballonnet is 650 cubic metres; and it has a length of 60 metres, by 10*50 metres maximum diameter. The car is 8 metres long, and follows the lines of a motor-boat, which the aerial screw is able to drive like a " hydroplane " should it settle on the water. The 8 6 -horse-power Cttment-Bayard motor drives two screws of 3*40 metres diameter, running from 600 to 1200 revolu- tions per minute, which give the airship a maximum speed of 53 kilometres per hour, one of the highest speeds attained up to this time in dirigible construction. The total weight of the balloon is 2500 kilogrammes. With a capacity of 3500 cubic metres it can lift 1100 kilogrammes, made up as follows : 4 aeronauts, weighing 75 kilogrammes each, representing 300 kilogrammes; fuel, 300 kilogrammes; ballast, 3 00 kilogrammes; accessories, 200 kilogrammes. The salient feature of this vessel, a feature which renders it an absolutely new type, differing entirely from the German craft, is the happy combination of the " rigid " and the HISTORY AND DESCRIPTION 91 " flexible " systems. There is a metallic framework, but in- stead of forming an immense and indeformable cylinder, as in the case of the Zeppelin, this skeleton is articulated. It is built up, if I may risk a comparison which seems to me to be most apt, of a series of " vertebrae," comprising huge hoops of steel over which the envelope is stretched. The floor consequently is rigid in the transverse, and flexible in the longitudinal direction, in such a manner that it can follow lengthwise all the movements of the envelope, move- ments so variable especially during inflation. A detachable "keel" formed of a tubular steel framework extends under the rear half of the bottom, and in contact with the balloon. This ensures an excellent longitudinal stability. With regard to the steering mechanism the elevating and lateral steering rudders this is attached to the stern of the envelope itself, beneath the empennage. This vessel was designed and built under the expert and masterly direction of Lieutenant-Colonel Moris of the Brigata specialisti, ably assisted by the two valuable officers, Captains Kicaldoni and Crocco. A Belgian sportsman, M. Goldschmitt, has built an airship bearing the name Belgium. It carries two independent motors of 5 horse-power each , two independent propellers, and is of 2700 cubic metres capacity. Its length is 54*80 metres; master diameter 9*75 metres. It can carry four persons, remain ten hours in the air, and travel at 40 kilometres per hour. Consequently its radius of action is 200 kilometres. Stability is secured by a cruciform empennage. This vessel was built at the workshops of M. Godard. Moreover, an aeronautical construction society has been established in Belgium. Strongly supported financially, it has placed on the stocks a powerful airship, La Flandre, of 6000 cubic metres. During the Exhibition of 1910 the Ville-de- Bruxelles made several successful ascents. Lastly, let us re- member the brilliant excursions of the Swiss dirigible Ville- de-Lucerne, constructed at the Astra workshops. 02 THE CONQUEST OP THE AIR COMPARISON OF DIFFERENT TYPES OF DIRIGIBLES : THE "CO-EFFICIENT" We see many types of dirigible balloons, widely different from one another. Each corresponds, in short, to a new idea ; each, one may say, indicates a development. But what is the net result ? In short, which is the best airship ? The problem is complex, more so even than in the case of steamships where there is something upon which to go. Accordingly, I have attempted to resolve it, and I hope, even if it is not complete, at least to have introduced a new factor in aeronautics the " co-efficient of advantage " of dirigible balloons. To evolve a mathematical formula combining speed with the shape of the aerial vessel, motive power, and dimensions of the propeller, is still somewhat impossible, there being many factors to take into consideration to formulate such a calcu- lation. But, inspired by the example of Dupuy de Lome in connection with steamships, I have sought to find an " em- pirical" formula. On the basis of results of experiments spread over a period of fifty years, the clever engineer evolved a formula called the " French marine formula," which has the advantage of simplicity. By a slight modification I have applied it to aerial navigation. This is how it is worked out ; it is a simple arithmetical problem by no means difficult, only requiring a little thought, and as much within the comprehension of the pupil of the ordinary school as of the university or college student. The power of the machine, expressed in horse- power, is taken, and divided by the number of square metres contained in the maximum section of the envelope. This gives a quotient, of which the cube root is then found. Then it is only requisite to divide the independent speed of the airship, expressed in myriametres per hour, by this cube root : the result of the division is a number, always "between 3 and 5, which qualifies the airship this is its co-efficient of advantage. This number expresses the value of the airship in exactly the same manner as the mark given by the examiner, to a young man who passes an examination, expresses the position of the; candidate in relation to his HISTORY AND DESCRIPTION 93 94 THE CONQUEST OF THE AIR competitors. The value of this number takes into consideration all characteristics which theory is still powerless to calculate correctly lines of longitudinal sections, resistance of the air, efficiency of motor; as well as pitch, slip, and efficiency of propeller, &c. In working with a number of dirigibles of which I have been able to obtain definite data, I have in every case been able to obtain an individual co-efficient, which will be found in the following Table : TABLE SHOWING CO-EFFICIENT OF ADVANTAGE IN REGARD TO DIRIGIBLE BALLOONS Names of Dirigibles. 1 Section. Propor- tion of length to diameter. Horse- power. Speed. Value of coefficient C. Giffard JF.) . 113 3-66 3 0-90 3-20 Dupuy-de-Ldme (F.) *$ 173 2-45 3 0-80 3-08 Tissandier (F.) 66 3*00 1-5 108 3-80 La France (Renard et Krebs) (P.) 55-4 6-00 9 2-33 4-24 Santos-Dumont (F.) 27-9 5-50 16 2-70 3-26 Lebaudy (P.) . 84 5-60 40 3-25 4-20 Patrie (P.) . 93 5-50 60 4-00 4-60 Clement-Bayard (P.) 90 5-00 100 4-50 4-31 Republique (P.) . 93 5-50 60 4-00 4.60 Zeppelin (Cyl.) . 106 11-00 170 4-00 3-47 Parseval II. (P.) . 68 5-00 100 4-20 4-04 Militaire Italien (P.) 90 5-00 70 4-50 4-90 1&8 (P.) 86 5-7 100 5-30 5 i (F.) : fusiform; (P) : pisciform ; (Cyl.): cylindrical. Therefore, by means of this co-efficient, one has a means of {< classifying " the balloons in their order of merit absolutely the same as in an examination. The mark attributed to each candidate permits its classification in relation to its colleagues. The more the co-efficient is in the neighbourhood of 5, the more advantageous is the airship, whereas its efficiency is indifferent if the co-efficient drops below 4. This simple method shows the superiority of Colonel HISTORY AND DESCRIPTION 95 Renard's ideas. The form of all dirigibles which does not follow that of the fish (the latter he maintained to be indis- pensable) have an inferior co-efficient. The Zeppelin, notwith- standing its huge elongation, reaps but slight advantage from its motor. On the other hand, La France, built twenty- five years ago, had an excellent co-efficient. The best are the Patrie, the RepuUique, and the Italian dirigible. In particular, the co-efficient 4 to 6 of French military balloons of the Eepublique type is remarkable, inasmuch as these balloons only have 60 horse-power motors, and always carry a heavy bulk of disposable ballast from 700 to 800 kilogrammes. If it is pointed out that the co-efficients inferior to 4 affect all fusiform or cylindrical balloons, one may go further and say that in all pisciform, balloons having the greatest diameter at the prow, the coefficient of advantage will always be "between 4 and 5, WHAT ARE THE IMPROVEMENTS TO BE EFFECTED IN AIRSHIPS? An independent speed of 45 kilometres per hour, therefore, may be considered fulfilled by airships commercially con- structed to-day. This speed enables them to set out in the vicinity of Paris with the certainty of being able to cope with the wind, and to steer in all directions for, on an average, about 300 days during the year. Such is a remarkable achievement without a doubt, but it is not sufficient. A speed of 70 kilometres per hour that is, 20 metres per second must be attained to enable them to go out on an average for 350 days out of the 365 ; thus the impossible days would number only fifteen per annum, and these would be wildly tempestuous days. Will it be possible to attain these speeds, and to increase the velocity from 13 or 14 to 20 metres per second ? Such will be reached probably, but it will be difficult, since it will be necessary to employ more powerful motors. Calculations show that if 13 metres per second are obtained upon a certain airship with 100 horse-power, it will be neces- sary to use about 450 horse-power to give the same vessel a velocity of 20 metres per second; undoubtedly the motive power must be divided between two engines and two propellers. Thus a much more powerful that is to say, heavier- motor 96 THE CONQUEST OF THE AIR would have to be used, consuming four times as much fuel, and the aerial vessel's radius of action would be decreased. The balloon itself would have to be provided with a stronger and heavier envelope, to be able better to resist the greater thrusts that the increased speed would bring to bear upon its surface. Perhaps it would be necessary even to resort to compartments, which would increase the weight still more. The solution of high speed demands, consequently, that air- ships shall be far larger and carry far more powerful engines. But then another point arises that of the resistance of the air, which is proportional to the square of the speed. Again, the balloon will assume an inclination, and will lift its nose slightly the action of the air will tend to lift the envelope as it lifts a kite. One consequently reflects whether, in the case of an airship of large dimensions, the naturally rising balloon, travel- ling at a certain speed, would not be able to sustain itself in the atmosphere without aerostatic intervention by virtue of the Archimedean thrust, and solely by the effect of the velocity of the air upon its suitably inclined surface. In other words, whether it would not be possible, under these conditions, to dispense with the " aerial float." Colonel Benard calculated that, with an airship of the dimensions of La France, this result would be obtained when the speed attained 72 kilometres per hour. In that case there would be no more need for the encumbering, expensive, and dangerous hydrogen, and we could rise into the air under a purely mechanical effort by an apparatus heavier than the air. This brings us to the study of this second form of aerial navigation which has opened up so brilliantly in the form of the aeroplane. PART II AVIATION APPARATUS CHAPTER I THE PRINCIPLES OF AVIATION THE " HEAVIER THAN AIR " PROBLEM : BlRDS AND KITES : THE PROBLEM OF EQUILIBRIUM : How IT CAN BE OBTAINED : DIFFERENT FORMS OF AVIATION I THE AEROPLANE WHAT IS AVIATION? AVIATION is the art of lifting and propelling through the atmosphere a body "heavier than air," by utilising the resistance offered by the gaseous element to the movement thereof. If the first successes of man in aerial navigation were due to the invention and use of aerostats, undoubtedly his first ambition was to emulate the birds, which are " heavier than air." Centuries of thought were required to grasp the physical principles upon which the action of the aerostat is based. On the other hand Nature had placed before our eyes marvellous travellers through the air the birds. As a result it may be affirmed that it was aviation, which, from the first, haunted the minds of those ambitious to traverse the atmosphere. But now the solution has been found. Although man has not realised yet in a satisfactory manner the solution as presented by the bird, yet the problem has been resolved by three quite distinct types of flying apparatus. These are : The Ornithopter (sometimes called orthopter), which is an apparatus having " flapping wings," imitating the bird's method of propulsion and sustentation. 97 G 98 THE CONQUEST OF THE AIR The Helicopter, an apparatus which uses simply the action of screws, as much for sustaining as for moving and steering. Aeroplanes, utilising, by means of large oblique surfaces, the resistance of the air for sustentation under a horizontal speed imparted by the screw-propeller. Ornithopters have been tested but rarely. Helicopters, very fascinating at first, have been relegated now to a second position. Only aeroplanes (the study of which has been pursued really rationally only during the past two years) have developed with such rapidity, and furnished such convincing proofs of their practical value, as to enable it to be conceded that the problem of aviation is solved at last. Consequently we shall devote the following pages almost exclusively to their study. HOW BIRDS FLY Before discussing aviation, such as is practised to-day by man, it is necessary to examine flight as fulfilled by birds, those inimitable natural aviators, the Latin name of which (avis, bird) has furthermore provided the appellation for the new trans-atmospherical locomotion. Being heavier than air, birds sustain themselves therein by utilising the resistance of this element to their movement. This resistance, as we have seen when speaking of " dirigibles," is proportionate to the moving surface, and increases as the square of the speed. Birds oppose to the air very large " sustaining " surfaces, known as wings. Also they have an organ, the tail, for balancing and guiding at the same time. The complex movement of their wings, securing a fulcrum by striking the air, enables them to force their way forward. Bird flight appeared mysterious for a long time, but, as Marey's works distinctly proved, it is effected in three distinct ways. There is, first of all, the " flapping " flight, where the birds beat their wings to keep themselves up and to move about as desired. Then, there is the soaring flight, practised by the bird when, hurled on at a great speed, it ceases to beat its wings, but keeps them outspread. O^ing to the large surface of the latter, gliding on the resisting molecules of the air, the bird only has to steer PLATE X^ THE JOANNETON AIRSHIP SPEED RECORDER THE GNOME LIGHT MOTOR PJiotos, Kol THE ESNAULT-PELTERIE LIGHT MOTOR Photo, Branger A 100 H.P. ANTOINETTE AVIATION MOTOR THE PRINCIPLES OF AVIATION 99 while moving forward. It is this phase of tho bird's flight which the aeroplane imitates. Lastly, certain large birds, such as the alba.ross and the frigate-bird, practise the sail flight, in which, without muscular effort, they press into service the varying wind velocities the " gusts " which occur in the atmosphere. When the bird feels the speed of the wind to be increasing, it faces the latter, and with wings outspread allows the wind to bear it along, both in ascension and progression. When it feels that the gust has reached its maximum speed, and is about to decrease, it turns round and glides, owing to the velocity and altitude it has acquired with the wind behind. During this gliding action it can attain and maintain high velocities, therein bringing into practice the gliding plane. At the moment it feels the advance of another squall, it turns round once more, head to the wind, and the same cycle of operations is repeated. In this manner it utilises the variations in wind velocity without any muscular efforts beyond those necessary for reversing from time to time. With marvellous animal instinct, it will be able to profit advantageously from the fluctuating intensity in the successive gusts, and will manage even to " gain upon the wind." How are these gusts produced ? So long as one is near the surface of the ground, it may be admitted that they originate from the varying reflections of the horizontal wind by the projections promiscuously scattered about the terrestrial surface, without any regard to geometrical laws. But it has been proved often that such gusts exist at great atmospheric altitudes. What, then, is the cause? Are they due to fluctuations in the intensity of solar radiance, according as to whether more or less opaque clouds interrupt the passage of the sun's rays, and thus produce unequal heating of the atmospherical masses ? Until careful observations, vital to aerial navigation, are made, concerning these phenomena, by aerostatic means, one must be satisfied with the conception of the dynamical state of the atmosphere as set forth by a clever French engineer, M. R. Soreau, an old pupil of the Ecole Poly technique, President of the Aviation Committee of the Aero Club of France, and one of the 100 THE CONQUEST OF THE AIR savants whose excellent theoretical studies have contributed perhaps most to the " unravelling " of so complex a question as aviation. M. Soreau compares the state of the centre of the atmosphere with that of the surface of the ocean. Every one knows that the open sea is traversed always by " wave " systems obeying well-determined rhythmical laws, of which the " swell " is the most common and simplest manifestation. According to this clever engineer, the atmosphere is the seat of similar aerial waves, communicating to the gaseous masses vibratory movements of a perfect regularity. The progress of the latter is uniform because at an altitude they are too distant from the ground and its projections for their regular line of move- ment to be susceptible to confusion. It is from such " atmospherical waves " that the bird profits in most cases of sailing flight. Will this sailing flight ever be accessible to man? In view of the more and more powerful, and at the same time lighter and lighter, motors, which he constructs, will man ever be in a position to achieve this end ? For my part, I do not think so. But it is interesting to bear in mind this variety of flight, which we see practised by birds having a large wing surface, the " great sailers " as they are called, which cleave the air above the ocean, and the fury of which is let loose by the tempest. Even then, these birds will utilise those " ascending currents of air," caused by the reflec- tion of the prevalent wind upon the oblique slopes of the immense waves of the Atlantic and of the Southern seas, where the height of these liquid hills reaches 16 to 18 metres. This explains why, by resorting to this gliding flight, these " birds of the tempest " always keep quite close to the disturbed surface of the ocean. As to the " wheeling " flight practised by birds of prey, in reality this is gliding. Sometimes when these birds are seen rising, gaining height whilst describing their majestic circles as, does, for instance, the buzzard it is because in so doing they utilise an ascending current of air, which is often produced in summer above abnormally heated ground. Hence, when soaring, the bird moves without effort. But THE PRINCIPLES OF AVIATION 101 a deep study of its movements shows that its wings fulfil two distinct functions propelling and sustaining surfaces respectively. Moreover, it is the extremities of the wings especially which propel the animal, the central area serving principally for sustentation. Why has man not sought the solution of the problem of aviation merely in the imitation of the bird flight ? It is because human thought has conceived, and has realised, a more general and more efficacious mechanical movement than those which exist in Nature rotary motion, of which Nature does not offer us any example, except in regard to celestial bodies. But there is a powerful reason for this peculiarity. Owing to all living beings being liable to growth as time progresses, their propelling organs must enlarge freely, in proportion to this growth. Such would not be possible always in combination with rotary organs. Man has sought, therefore and success has shown that he has done so with reason to accomplish high travelling speeds on land and sea by means of revolving apparatus wheels, screws, turbines, &c. He has been able thus to attain and to exceed the speed of the fleetest of animals. Now, why should what is good on land and sea not suffice for the air ? We do not construct motor-cars with feet nor trans- atlantic boats with fins. Therefore we may seek for propulsion through the atmosphere otherwise than by flapping of wings. If we use wings for sustentation we must at least concern ourselves with machines and revolving propellers to move in the Aerial Ocean. THE FORERUNNER OF THE AEROPLANE : THE "KITE" The excessive weight of the " human motor," a weight which, as we have seen (page 7), approximates 1000 kilogrammes per horse-power, appears to forbid man the realisation of flight, by the use of his own muscular effort. All who have tried to solve the problem of aviation in this manner have failed. But from time immemorial a means of raising bodies "heavier than air" into the atmosphere has existed. This is the " kite," that toy, which has now become one of the Pressure oHheair 102 THE CONQUEST OF THE AIR most valuable instruments in scientific investigation, but which has been known in China and Japan from the most remote days. It is scarcely necessary to define the kite, which we have all handled, more or less. It is a rigid frame of wood and strings, on which is stretched a surface of fabric or paper. A string holds the apparatus to the ground, and when the wind reaches a suffi- cient velocity the con- trivance lifts itself into the air. If the surface of the kite is sufficiently large, it may even lift objects meteorological instruments or photo- graphic apparatus. Direction of the wind. Weight FIG. 42. Equilibrium of the kite The Idle is kept m equilibrium under the com- bined action of its weight, pressure of the wind, and resistance of the string by which it is held The equilibrium of the kite is due to the combination of the forces which bear upon it (Fig. 42). The surface exposed to the wind is, in fact, kept " oblique " in relation to the direction of the latter. The molecules of air, in striking against this slanting surface, exert a thrust thereon which, as is shown by calculation and proved by experiment, is perpendicular to this surface, and tends to lift it. This is one force to which the apparatus is submitted. There is a second, which tends to cause it to fall towards the earth ; this is its weight, which acts vertically from top to bottom. And finally there is another ; this is the tension of the cord, the resistance of which acts as a check against the thrust of the wind. The pressure, resulting from the action of the current of air upon the surface of the kite, divides itself into two elemen- tary actions. One is directed from bottom to top, and combats directly the thrust of the weight : the direction of the other is opposed to that of the retaining cord, and is therefore always destroyed by the latter, which one concludes to be sufficiently resistant as not to break under the effort to which it is subjected. THE PRINCIPLES OF AVIATION 103 Under these conditions, the contrivance is in equilibrium. Let one of the above forces be varied, and equilibrium is disturbed immediately. If the wind increases, its pressure becomes stronger, the vertical thrust is augmented, and the kite rises. If, on the contrary, the wind does not change, but the weight of the apparatus is enhanced unexpectedly, as, for instance, by rain, the kite falls. Lastly, if the third force is annulled, that is, if the cord breaks, the kite is carried away by " the wind." Such is a very simple example of an apparatus, which lifts itself by utilising two forces: (1) the resistance of the air; (2) the tension of a cord, which maintains the surface exposed to the wind. Of course there must be a wind to lift the kite. Now there are some days when the wind is a negligible quantity. What is to be done then ? Children, the traditional fliers of the kite, do not allow such a small trifle to stand in their way. There is no wind ? Well, " they create one," by running as quickly as their legs will carry them, for it must not be forgotten that wind is not a concrete factor ! It is the relative movement of the air in comparison with a body, and this movement may take place, either with the air in motion and the body stationary ; or with the air still and the body moving rapidly through it. This is the reason why in a motor-car one has a sensation of " wind " even when there is none. And children, by following these instinctive actions, invented and realised the aeroplane. SCIENTIFIC KITES : MILITARY KITES : KITE ASCENTS We do not intend to give in detail the technics, construction, and launching of the kite. But it is impossible to ignore two of its applications which are of the highest value, the one to science, the other to war. These are exploring and military kites respectively. When it is a question of investigating scientifically the uppermost atmosphere, " sounding balloons " carrying self- registering barometers and thermometers are sent aloft. These balloons can rise to extreme altitudes; they have attained heights between 18,000 and 20,000 metres. But 104 THE CONQUEST OF THE AIR they are liable to be lost, to fall into desert regions whence they can never be recovered. When it is desired to ascertain the temperature of the air in other than the very highest regions, when an altitude of from 4000 to 5000 metres is sufficient, one can use kites formed of several flat surfaces connected together. It will be noted that we find this arrangement in the biplane. Self-registering meteorological instruments, photographic appliances, &c., can be attached to this apparatus, which after being sent up is held, not by a cord, but by a thin steel wire seven or eight tenths of a millimetre in diameter. Such a wire can withstand a strain of nearly 50 kilogrammes without breaking. Kites so equipped, and flown by Prince Albert of Monaco over the Atlantic from the deck of his yacht Princess Alice, attained an altitude of 4500 metres, recording most valuable results concerning the temperature and humidity of the upper atmospheric strata. But it is possible to go farther. We can imagine the ambition of an observer to lift himself by the aid of a kite. As a matter of fact, in France, two distinguished officers, Captains Madiot and Sacconey, have carried out some very fine experiments in the course of which they lifted themselves with a success which was equalled only by their intrepidity. However, this idea is old ; the earliest attempts date from a long time ago. The French sailor Le Bris made the first venture in 1856 ; Maillot followed him in 1886. But it is through the efforts of the English and Russian officers that we are able to say that ascent by kites is now an accomplished fact. We may confine ourselves to the mention of the names of Hargreaves (1894), Baden-Powell (1894, 1896, 1898), Lamson (1896), Wise (1897), in England, and above all of the Russian Lieutenant Schreiber, and the English Captain Cody, two designers of military kites. In this case, several kites are used, their sustaining efforts being led to a single cable to which the " car," in which the observer desirous of being lifted takes his position. The lines on which such a " train " of kites are disposed and manoeuvred differ according to the various operators. After all is said and done these experiments are of the THE PRINCIPLES OF AVIATION 105 greatest interest to aviation, and they support that apt expression of the unfortunate Captain Ferber, " A kite is nothing more than an anchored aeroplane." DEFINITION AND ELEMENTARY EQUILIBRIUM OF THE AEROPLANE An aeroplane, in fact, is nothing but a kite which " creates its own wind." For this purpose the string is replaced by a motor, and a screw which imparts a speed equal to what the wind would have to be to support it like a kite, were it held by a cord. The pull of the string is replaced by the thrust of propulsion (Fig. 43), and the conditions of equili- brium are, at least funda- mentally, quite as simple as those of the kite. An aeroplane in principle Component for FIG. 43. Equilibrium of the theoretical aeroplane The aeroplane is kept in equilibrium under the combined forces of its weight, power of its engine, and of the resistance of the air therefore will be composed of a supporting surface divided into one or two parts, which are often called the wings, attacking the air in an oblique manner by means of a propeller and a motor. It will be connected to a skiff or car, in which will be the aviator, the motor, and the mechanism for steering, comprising at least two " rudders " one a " steering rudder," to turn to right or left, and the other an " elevator," for ascending or descending. The motive power propelling the apparatus, the surface of which cuts the air in an oblique manner, compels the gaseous molecules to glide under this surface. Therefore, they exercise a resistance upon it, the effect of which is a perpendicular thrust upon the moving plane. This thrust may be replaced by two other forces ; one vertical, which tends to lift the contrivance, by annulling the effect of its weight, which would tend to make it fall ; the other, horizontal, directed towards the stern, and tending to retard the speed of 106 THE CONQUEST OF THE AIR the apparatus. Therefore equilibrium is realised when the speed due to the motive power is sufficient for the thrust to be able to lift the weight of the apparatus. Thus this speed is called the " controlling speed," and the aerial vehicle will continue its travel in a straight line so long as the forces which act thereon retain their re- lative values. But if any one of the considered forces should change, the equilibrium Moving surfe.ce. Direction of travel FiG. 44. Resistance of the air upon a slanting surface is destroyed imme- diately. For instance, if the speed of propulsion increases, the resistance also increases, and also therefore the resultant vertical lifting component. The weight not varying, equilibrium is destroyed and the apparatus rises ; on the contrary it descends if the speed of propulsion Lifting power. Direction of -movement. FIG. 45. Influence of the angle of attack The vertical lifting thrust increases as the angle of attack is decreased decreases ; it descends also if the " supporting surface " for some reason or other is diminished, in the same manner as it rises, if the weight of the apparatus is lessened, as occurs during a journey, owing to the consumption of fuel by the motor. Therefore, the very simple conditions of equilibrium which we have examined are precarious, and the problem must be investigated a little more closely to seek the conditions answering the requirements of current practice. PLATE XXIII THE LITTLE " SANTOS-DUMONT " AEROPLANE Photos, Rafjatle PLATE XXIV THE "SANTOS-DUMONT " AEROPLANE WINNING THE DEUTSCH PRIZE A " SANTOS-DUMONT '' MONOPLANE * Photos, Raffaiile SANTOS-DUMONT'S " DEMOISELLE Photo, Branyer THE PRINCIPLES OF AVIATION 107 RESISTANCE OF THE AIR : ANGLE OF ATTACK : CENTRE OF THRUST To learn exactly what will happen when the controlling ^peed is varied, we must hearken back for a moment to the laws of the resistance of the air, which are fundamental in the question of aviation. Let us consider (Fig. 44) a moving surface, inclined in the lirection of its advance. The resistance of the air increases )roportionately to the spread of this surface, in proportion ,vith the square of the speed at which it is driven, and increases it the same time as the angle at which it is inclined to its trajectory, and which is called the angle of attack. Conse- quently, if this angle is very small, the resistance is very slight ; but on the other hand, the lifting effort is a greater proportion of the thrust (Fig. 45, No. 1), whereas the resistance to advance is a fraction less. If the angle of attack increases (Fig. 45, No. 2), the thrust becomes stronger immediately, but the pro- portion of this thrust, which constitutes the lifting effort, decreases if more inclined to the vertical, whilst resistance to advance is increased. Therefore it is necessary to seek the optima value of the angle of attack. Calculation and experience agree that it must be very small always. But a more uninterrupted study of the resistance of the air upon an inclined surface in motion, shows us something even more important. We have supposed, in the elementary explanation which we have given of the conditions of equilibrium of an aeroplane, that this was absolutely symmetrical, and that all the forces which acted upon it were applied to a common point G, which would be its centre of gravity. In practice, things are not so simple. In reality the point of the moving surface where the pressure is applied, a point which is called the " centre of thrust," does not coincide with the centre of gravity. It approaches nearer to the front edge of the moving surface, as the angle of attack is decreased. This is what experiment demonstrates : if one moves forward through the air in a horizontal direction, a per- pendicular plane which cuts the molecules squarely (Fig. 46), the phenomena are symmetrical, and the thrust will be 108 THE CONQUEST OF THE AIR exercised upon the centre of gravity itself. But if the moving plane is inclined (Fig. 47), the gaseous molecules have much greater difficulty to rise up under the cutting edge than to go downwards to gain the other side of the plane. Then the thrust is greater on the front extremity up which they are forced to travel, and the centre of thrust comes nearer the front in Such fluctuation the position of the centre of thrust alters the aeroplane's conditions of equilibrium and affords us some data concern- ing construction. Let us consider an aeroplane advancing (Fig. 48) with a very small angle of attack. The centre of thrust, as we have just seen, will be brought forward to a point near edge. FiG. 46. Flat perpendicular surface advancing horizontally through the air (the air molecules glide symmetrically round the ends) Direction of motion. Fig. 47. Flat surface advancing obliquely through the air The molecules of air glide by in a dissymmetrical manner, and the thrust of the air approaches point A the front edge. The lifting effort applied to this centre will be directly opposed to the weight no longer, the latter being always applied to the centre of gravity. Hence the disposition of the two forces will tend to cause the surface of the aeroplane Lifting force THE PRINCIPLES OF AVIATION 109 to turn in the direction indicated by the curved arrows shown in the diagram. Moreover it is necessary to observe that the position of the centre of thrust is not fixed ; it varies for each value of the inclination of the aero- plane, and advances more towards the front as the angle of attack is made sharper. Yet this is not all. Let us suppose, through an accident or some untoward mishap during travelling, that this surface is inclined ex- cessively. The air would then strike from above, Direction Weight. FlG. 48. Equilibrium of the actual aeroplane Lifting effort and this would bring about a certain rapid and fatal fall. Con- sequently a means must be found for readjusting the aero- i plane when it inclines in the direction of its length. This end is fulfilled by the empennage. The empennage com- prises a surface placed well to the rear of the sustain- ing gurface ( Fig> 49^ to which it is joined by a "connection" which, being Move rn.cn t for righting -o^- Centre oF thrust of gravity Weight. FlG. 49. Effect of the empennage It restores the balance of the inclined aero- plane owing to the wind impinging upon the tail from below light, rigid and latticed, offers only a slight resist- ance to the air. Under these conditions, when the influence of the thrust is applied forward of the centre of gravity, where the weight acts, the aeroplane, as shown in Fig. 48, tends to turn in such a manner that its stern is lowered towards the ground. But the thrust which is exercised upon the empennage, a thrust acting with the aid of the long " lever arm " represented by the rigid connection, lifts and brings the apparatus back to its normal incline, in accordance with the Straightening FIG. 50. Effect of a vertical stern " fringe" 110 THE CONQUEST OF THE AIR calculations concerning its dimensions and motive power. In the same manner a projecting "flange" (Fig. 50) not very high, towards the stern of the sustaining surface, would be " effaced " behind the front edge during the journey under a normal incline. But if the apparatus were declined at the bow, the air striking this flange, which would be ex- posed by the accidental lowering of the front n , - edge, would act there- Direcoon of rruovement n -, . on, and this pressure, bearing on the stern, would force it down, restoring the aeroplane to its normal incline. It may be seen, therefore, from these two examples that an aviation apparatus can be given an automatic longitudinal stability. Let us remark that kites have been fitted with this very simple means to secure longitudinal stabilisation for a long time past in the form of a tail. This does not serve merely as a counterweight to the stern ; a piece of lead at the bottom of the frame would answer this purpose, but without ensuring stability. The tail acts as a true stabilisator, and kites must be provided therewith. However, we shall return to this subject in the course of the next chapter. There is one other question, also vital in balancing the aeroplane ; that is transversal stability. But in this question, the shape of the wings, dimensions, even the construction of the apparatus, are inferred as being known. We will conclude this explanation of the general principles, and see how they are applied to the conception of a projected flying machine. CHAPTER II APPLICATION OF THE GENERAL PRINCIPLES FROM THEORY TO PRACTICE : THE WINGS : MONO- PLANE OR BIPLANE : STABILITY AND THE MEANS FOR ITS REALISATION SHAPE AND DISPOSITION OF THE WINGS WE have seen by what effects of the resistance of the air a flying machine may be sustained in the atmosphere. We must now ascertain in what manner we can utilise these effects most advantageously. First of all, should we use flat or concave wings ? This is the primary question. If we take as an example the wings of a bird, which are the sustaining surfaces for soaring, we notice that they are always concave underneath. Since the first attempts at aviation, constructors, therefore, have sought always to build wings distinctly concave, the concavity being turned towards the earth. Experience has shown, moreover, that a surface slightly concave towards the rear gives the aeroplane, for the same speed, much superior lifting power to that obtainable from a flat surface carried thereto. Further, M. R. Soreau, in a very fine calculation, has shown that for any concave wing a flat surface may also be determined. Such would act as if it were connected rigidly with the concave surface, while the carrying power would be just the same as that of the concave surface. But, at the same time, the concavity introduces a " counter -resistance " to advance, i.e. produces a force of reaction which increases somewhat the propelling effort in the same direction. In other words a slightly concave surface " carries " better than an equivalent flat surface. in 112 THE CONQUEST OF THE AIR Calculation and experience being in agreement in the re- commendation of concave surfaces, we shall employ such in the construction of aeroplanes. Moreover, the wings will be elongated and disposed at right angles to the length of the flying body. For this purpose imagine a wing of rectangular shape, measuring 2 metres by 4 metres, viz., 8 square metres (Fig. 51). If we cause this surface to advance longitudinally, the streams of air struck by its front edge, and driven be- neath the wing, will escape Direction tf Movement under the ed g es to which ir current-Si * FIG. 51. A long, narrow, flat surface The currents of air escaping immediately along the sides are inefficient for sustentation they are in close proxi- mity, and will contribute no longer to sustentation. If, on the contrary, this same wing be moved on its broader edge (Fig. 52) the currents of air cannot escape sideways, because they are pressed back by their neighbours, with the exception of those which are at the extreme sides. In this second arrangement, all the cur- rents thus contribute to sustentation. Our wings, which we have been induced to make slightly concave, will therefore be disposed transversely. This lateral arrangement of the sup- porting surfaces, moreover, is what we find in all birds and flying insects; in birds particularly the " spread " of the wings is always considerable (Fig. 53). In addition, irrespective of the ex- tent of this spread, the carrying surfaces may be set either horizontallly, in the form of a more or less obtuse angle, or like a very open upright, or overturned V. Direction of travel. FIG. 52. A short, wide surface The currents of air are kept beneath the surface during the movement, and are therefore able to sustain the plane The V-arrangement of the wings has been adopted, notably by Captain Ferber, while on the other hand the wings of the Wright machine are straight. THE GENERAL PRINCIPLES 113 MONOPLANES AND BIPLANES We are led, by virtue of what has been said, to take light sustaining surfaces of great superficies if we wish to raise an appreciable weight, such as, for instance, a motor, propeller and aviator. Let us suppose that calculation as a result of experimental data shows us the necessity of a carrying surface of 50 square metres. Will this surface have to be em- ployed in the form of a single transversal wing, of two, or even of three wings super- imposed ? Under these con- ditions the transversal " spread" is decreased, which, as regards the encumbrance of the apparatus and its FIG. 53. A bird's wings outspread The wmgs act as supporting surfaces and the tail serves as the empennage working efficiency, may constitute an advantage. In other words, shall the aeroplane be " monoplane " or " multiplane " ? Birds obviously are monoplanes, and they are excellent monoplanes too. Consequently everything would urge us to make our aeroplanes as monoplanes. But there are kites to recommend multiplanes, or at least biplanes ; and the indica- tions of this popular toy cannot be overlooked, for, as Captain Ferber so truly said, " the kite is an anchored aeroplane." In fact, if the ancient kite is a monoplane with the " tail " con- stituting the stabilisating empennage, the modern kite is at least a biplane. The following will show how and why this disposition has been adopted, and which experience has shown to be very advantageous. Let us consider a kite (Fig. 54 A) which we send aloft in a very steady wind. So long as we do not seek too great a height, the apparatus will behave beautifully. But if we wish to send it higher and higher we must not forget as we pay out the cord that the kite has to support a proportion of the ever-increasing weight. Therefore there will be a height limit above which the weight of the paid out cord will exceed the carrying effort, resulting from the thrust of the air upon the membrane of the kite, and the latter will fall. But 114 THE CONQUEST OF THE AIR an arrangement, as simple as it is old, can be employed now. An auxiliary kite may be introduced and attached at an inter- mediate point of the main kite cord, and will thus support a proportion of the cord's weight. Such a combination will be able to rise to a much greater height than a single kite. The two kites may be placed a short distance apart, or be brought Wind. FIG. 54. Evolution of the box, from the multiple, kite The two planes of the kites spaced apart in the system A are brought together and combined in the system B ; while in C two groups of parallel surfaces, connected together by a rigid framework, resemble the biplane in the general lines very close to, and parallel with, one another (Fig. 54 B), or they may be so made up as to form boxes covered with cloth. It is upon these lines, laid down by Hargreaves the Australian, that the modern children's kite (Fig. 54 C) is built; also those, larger and more skilfully constructed kites, which are used by meteorologists for carrying registering instruments into the upper atmosphere. The " cellular " kite (Fig. 54 C) is nothing but a biplane aero- plane, provided with an " empennage tail," to secure its stability. Therefore we can distribute our supporting surface upon two superimposed parallel planes. Such is the design of the Farman, Delagrange, Wright, and Voisin aeroplanes, whereas those of Bleriot, Esnault-Pelterie, Gastambide, Santos-Dumont, and the " Antoinette " are monoplanes. Naturally, we can make triplanes or quadriplanes, but one must not proceed too far in this direction, as there would result a " pile of planes," the stability of which would be precarious. Here, as in all THE GENERAL PRINCIPLES 115 things, the happy medium must be found. One inherent objection to multiplane construction must be pointed out ; the rigid supports which connect the planes together present a large surface of resistance to the air, and for this reason mono- planes are much to be preferred. Moreover, the Reims week of 1910 demonstrated conclusively the superiority of the monoplane, which appears to be the aviation apparatus of the future. LATERAL STABILITY : TURNING We have obtained longitudinal stability in the aeroplane by the use of the " empennage tail." But lateral stability must be secured also. In other words, the wings of the apparatus must not incline from right to left, or vice versd, during travel. At any rate, if such an incline were perchance to occur, the appa- ratus must be constructed in such a way that it rights itself under its own effort. Now, an aeroplane must be considered in two phases of movement that following a straight line and that following a curved line, otherwise called " turning." In the case of the straight line movement, the lateral stability, if not ensured, is fulfilled very adequately at least by the spread of the carrying surfaces, which counteracts sudden inclination. Moreover the centre of gravity of the contrivance is always below the carrying planes (or the single surface equivalent thereto) on account of the weight of the motor and passenger, a weight which would tend to right the apparatus if it were to incline unexpectedly. But this is no longer the case when, describing a curved line, the aeroplane turns. Then there intervenes a complex phenomenon which causes it to dip " inwards " that is to say, towards the centre of the circle which the machine describes. This phenomenon is the unequal resistance of the air upon the two extremities of the supporting wings. We must examine this a little more minutely. Let us consider an aeroplane (Fig. 55) describing a turn. To gain a clear idea of the subject, let us suppose that the spread of this aeroplane is 10 metres, and that the circle which the centre of the machine itself describes has, for instance, a radius of 15 metres. Under these conditions it will be seen that the inner extremity, A, of the wing will 116 THE CONQUEST OF THE AIR describe, during a certain time, the arc of the circle AA', in passing from position (1) to position (2), whilst the outer extremity, B, of the same wing will describe, during the same time, the arc of the circle BB', double the length of AA'. The exterior extremity, B, therefore must travel twice as far during the turn as the interior extremity; that is to say, move at twice the speed of that of the inner edge, A. Now, as the resistance of the air is proportionate to the square of the speed, the result is that the in- terior extremity, A, moving less quickly, will be subjected to a lesser resistance from the air, and therefore will be less "sustained" by the air than extremity B. Consequently, while turning, the aeroplane must incline itself more Axis on which it turns X FIG. 55. How an aeroplane turns The resistance of the air upon the inside wing being reduced, transverse equilibriumis destroyed, so that the aeroplane inclines towards the centre of the circle represented ly the turn and more towards the centre of the circle which it describes, as the radius of the turn is decreased. We can confirm this by means of figures, and in a very simple manner. If the speed of the outer wing is 20 metres per second, that of the inner wing, in the example we have taken, will be only 10 metres. The lifting efforts will there- fore be no longer equal, but will be between them in the pro- portion of the square of 20 with the square of 10 that is, in a proportion of 400 to 100. It may be seen, therefore, to what degree the equilibrium will be destroyed. It is true that an aeroplane may never have to make so " sharp " a turn, but we have selected an extreme example purposely. Such always exists, so lateral incline must be guarded against absolutely while turning. THE GENERAL PRINCIPLES 117 This natural incline, however, has its advantage ; it counter- acts centrifugal force appreciably. The latter is unavoidable in any curvilinear movement, and is of greater moment in the aeroplane inasmuch as its surface of lateral resistance is weaker. Major P. Renard actually proved that inclination of the aeroplane was essential to combat centrifugal effect. This inclination lowers the trajectory. Therefore, aviators should rise slightly before making a " turn," if subsequently they desire to maintain their altitude. PRACTICAL MEANS OF PREVENTING LATERAL INCLINE : AILERONS," PARTITIONS, WARPING At all events, it is indispensable to keep the carrying surface as horizontal as possible throughout the trajectory, whether it be rectilinear or curvilinear. Several means may be utilised to this end. First of all, there is a very simple one, which I am surprised at not having seen used experimentally, or at least tried, since it seems very feasible to me. Since " lateral inclination " is a result of unequal resistances on the two extremities, why not equalise these resistances ? We cannot prevent speeds from being unequal while turning, but we can vary the supporting surfaces inversely ; we can increase the surface at the " inner point" A (Fig. 55), and decrease it at the outer point B. For this purpose it would suffice to fit to the extremity of the wings, varying surfaces, either arranged in the form of a fan and able to fold up in the same manner as a bird's wings, or of sliding ribs, one withdrawing a certain distance beneath the extremity of the outer wing, and the other projecting to twice that distance from the extremity of the inner wing. The surface of the inner wing which dips would thus be increased, while simultaneously that of the outer wing which rises would be decreased, and it would reduce the difference from the thrusts that is, the cause of the inclination. These two movements could be produced automatically by a simultaneous movement of the steering rudder. The celebrated American aviators, Wilbur and Orville Wright, have adopted another arrangement " warping of the wings." The following explains in a few words how this is done. 118 THE CONQUEST OF THE AIR The extreme angles of their aeroplane can be turned up or down (Fig. 56) just like the "corner " of a visiting card. As the Wright aeroplane is a " biplane," wooden battens disposed one above the other lift up the corners at the same time, so that when a corner of the upper wing is lowered the corre- sponding corner of the lower wing is depressed also. The Action of the air tending To depress the left corner * -wrucK turning raises. I Action of air tending "to lift the left yf corner which I / turning lowers Without \ warpmg tke | aeroplane I would ' decline. * FIG. 56. The Wright principle of warping the wings The warped corners strike the air, the resistance of which depresses the upturned corner t and elevates the lowered corner action is controlled by a manoeuvring lever pushed or pulled by the aviator, and when the corners on the left are forced down those on the right are forced upwards, and vice versa. Under these conditions, it is easy to see how this arrangement enables lateral inclination to be overcome. A turn is made, and the aeroplane has a tendency to incline inwards ; but the aviator immediately manoeuvring his lever, lowers the corners on the inside of the turn and elevates those on the outer edge. And then, as is shown in the diagram, the effect of the air on the corners thus offered to its action rights the apparatus. M. L. Bleriot, the French aviator, evolved and adopted on his aeroplanes some time ago long before the arrangements of the Wright Brothers had become known a very reliable system, quite as ingenious and far simpler, which does not require the wings to be deformed by warping. There is THE GENERAL PRINCIPLES 119 at each extremity of the fixed wings of his aeroplane, a small subsidiary moving wing, " Aileron " (Fig. 57), capable of being inclined in relation to the surface of the wing by moving upon a horizontal axis. When turning the aileron on the inside is lowered while the outer aileron is raised. The effect is the same as warping the wings, but this arrangement has the advantage of not bring- ing about any elastic deformation of the frame which, unavoid- Ro _ 6? B1 , riot>s oorrecting ailerons able through warping, 4-1.1 J These ailerons strike the air, which lowers the upturned must inevitably end aileron, and elevates the depressed aikron in endangering the essential solidity of the structure. Many vessels of the Antoinette type are fitted with this arrangement, which is excellent from all points of view. These various arrange- ments for righting are governed by the aviator. Therefore it is necessary for him to bring about the readjustment of the apparatus ; to perform a special movement, com- pleting that which he Cells. FIG. 58. The Voisin partitioning system The vertical surfaces oppose " drift " makes in steering to right or left when manoeuvring the machine by the rudder. But search has been made for an automatic balancer indepen- dent of the helmsman, but brought into play by the aeroplane itself. This solution has been offered in a simple manner by the Voisin Brothers, the French constructors who built the aeroplanes made famous by the exploits of the aviators Farman, Delegrange, and Rougier. The arrangement employed 120 THE CONQUEST OF THE AIR by them is "partitioning" (Fig. 58) and applies to multiplane aeroplanes. It comprises the introduction of rigid vertical partitions between the two parallel carrying surfaces. These partitions, owing to the resistance they offer to the air, oppose any deviation arising from centrifugal force, so that lateral inclination is practically eliminated. The aviator, owing to this principle of construction, no longer has to trouble about his equilibrium : he only has to think of steering. Let us remark, in passing, that although it is true that the auxiliary surfaces of the partitions add a little weight to the apparatus, they do not increase, at least to any significant degree, its resistance to advance, inasmuch as they cut the air with their edges, and are set in the direction of travel. Although this system does no more than make the machine a little heavier, this is a distinct drawback to present-day aviation. Hence there is a tendency to revert more and more to the ailerons or to warping. In the latest French biplanes the partitioning is abandoned in favour of ailerons. Lastly, there is "artificial" balancing obtained by the stabilisating mechanism bringing into action forces other than the resistance of the air. This type of balancer is the gyroscope. Every one knows those toys <( gyroscopical tops " which once started at full speed maintain their balance on a point or on a thread, appearing to defy all the laws of gravity and equilibrium. These gyroscopes, discs with a heavy periphery, have the important mechanical quality of being caused to deviate only from the plane in which they are rotating with great difficulty and at the expense of a very great effort. The extent of the latter to bring about deviation becomes greater as the turning mass is increased, and its speed augmented. If, therefore, a gyroscope is mounted on an aeroplane and its rapid rotary movement is maintained by a motor, an effort is necessary to change the rotating plane forming part of the frame of the aerial vehicle, and one may hope thus to obtain lateral stability in an automatic manner. Theoretically this idea is excellent. In practice it is another matter. THE GENERAL PRINCIPLES 121 In the first place, a gyroscope when constructed on a large scale becomes a very dangerous apparatus. Let it escape from one of the bearings in which the points of its axis revolve and it becomes a destructive projectile both of men and everything else. Serious accidents have happened already from this cause. In the second place, in order to be efficient, it must be fairly weighty, and in the matter of aviation, weight is a very vital factor. Then and here is the greatest theoretical objection which can be urged against its use it might, if it worked efficiently, compromise the| solidity of the light framework constituting the aeroplane. In fact, what causes the aeroplane to incline, is the effort resulting from the action of air resistance bearing upon all parts of its long surface, whereas the gyroscope only acts at one single point of its framework. It is, therefore, supposing this means of balancing to be efficient, as if one of the points of the aeroplane were pinched in a vice and an inclining effort exercised upon the rest of the fabric. What would happen then? Twisting would occur which might jeopardise the solidity of the structure. For this reason, it seems to me that the gyroscope would be dangerous if it really acted ; and if it should be inoperative it would be a dead weight, useless to haul about in the air. But all this is only theory, because experiments alone, frequently repeated, will be able to supply us with really reliable data on this point. Let us add, that the use of a double rudder at the bow and stern, moving in opposite directions, has been suggested in order to improve balancing. So far experiments have not been sufficient to decide the practical value of this arrangement. Another means of automatic balancing, evolved and tried a short while ago, comprised automatic variation of the " angle of attack " by articulating the whole of the carrying wing around a horizontal axis. This wing is held in its normal position by a powerful spiral spring which resists the pressure of the air when the aeroplane is travelling at the required speed, but which succumbs to this thrust, if the speed increases suddenly, by diminishing the angle of attack. Experience will show 122 THE CONQUEST OF THE AIR what this ingenious conception is worth. In any case, the " natural " means of balancing are the most rational, because they act with effects similar to those of the perturbing forces of equilibrium. STEERING : THE RUDDER AND ELEVATOR As we have mentioned turning movement, the means by which it is accomplished must be indicated the steering rudder. The steering rudder is similar to that used on boats and dirigible balloons. It is a light, strong, thin plane, turning about a vertical axis, operated by a "wheel" or motor levers, at the will of the aviator, who can turn it either to the right or left. The rudder is placed as far as possible to the stern of the aero- plane, and away from the supporting surfaces (Fig. 59). When it is turned to the right or to the left, the molecules of air, strik- Action. of the air upon the inclined r udder. >\ "Rudder. DirecHon of movement FIG. 59. The steering rudder The air striking the rudder blade causes the aero- ing its surface in an ob- plarx to turn in tht opposite direction mannerj exercise a thrust which is all the more efficient in causing the body of the aeroplane to swerve, since it is placed at the end of a long lever. It is for this reason that the rudder is placed invariably at the rear end of the empennage tail. When it is desired to travel in a straight line, the steering rudder is brought back to the central position ; that is to say, to the longitudinal axis of the apparatus, and the air no longer acting upon its surface, no horizontal deviation results. The steering rudder can be efficient only if the aeroplane present a " lateral resistance to drift." An aeroplane with no opposing surface to a transverse movement, will not answer the helm. Hence, there must be a lateral surface, if repre- sented only by the " hull " of the skin". From this point of view, therefore, partitioned aeroplanes are really superior. THE GENERAL PRINCIPLES 123 The elevator is a similar device, but moving about a horizontal axis, causes the aeroplane to deviate, not to the left or right, but upwards, or downwards ; in other words, compels it to ascend or descend. Its operation is explained in the same manner as that of the steering rudder. This invention has been attributed to the Wright Brothers, but I believe erroneously, as Colonel Renard applied it to his airship La France in 1885, as is testified by the official documents published at that time, which contain a full description of the arrangement and also the explanation of its operation. The elevator may be placed either at the bow or stern of the aeroplane: each disposition has its advocates and opponents The Wright Brothers have placed it at the bow, and as people " went a trifle mad " on everything associated with their name, it was concluded to be " imperative " to carry the elevator in front. But Messrs. Esnault-Pelterie,Bleriot, and the constructors of the Antoinette aeroplane, to cite only these gentlemen, instal it at the stern. LAUNCHING THE AEROPLANE Every one knows that principle of reasoning, extensively used in geometry, which commences, " Let us suppose the problem as solved." Present industry offers us a variety of machines which, if I dare so to express myself, " can only go when they are already going." There is, for instance, the explosion motor, which must be " started up " with all one's might to set it in operation so that it may attain its normal speed. The aeroplane is a new example of this method of procedure. The conditions of equilibrium suppose its being in flight : stationary, it remains on the ground. Therefore it must receive an initial impulse, which " launches " it into the atmosphere, and imparts to it that speed which, owing to the molecules of air gliding under its oblique wings, first lift and then sustain it. There are two ways of carrying out the launch. One may seek to endow the aeroplane with self-starting means. On the contrary, it may be launched artificially with the help of a contrivance remaining at its point of departure. Such 124 THE CONQUEST OF THE AIR launching is easy, but the apparatus, if it lands, cannot restart ; it must return to a point equipped with launching apparatus, under penalty of being condemned to rise no more into the air. French constructors and aviators courageously accepted the hard conditions which an aeroplane must fulfil to be " self- starting,"and all French aviation apparatuses leave the ground under their own power. For this purpose they are mounted on a carriage fitted with bicycle wheels. This carriage must be as light and as strong as possible, since at the moment of landing it has to withstand the shock produced as it alights upon the ground, however much this may be lessened through the skill of the aviator. Then it is an additional load, varying from 50 to 80 kilogrammes, which any aviation apparatus desirous of launching itself without outside help must carry. But there is another extra weight imposed under this condi- tion. This is the increase in motor power necessary to start by a run along the ground, under the impulse of the propeller screw attacking the molecules of air. First the inertia of the motionless apparatus must be overcome, and for this the motor must give a " pull against the collar." This effort causes the aeroplane to run along the ground, with increasing speed, until the latter is suffi- cient to bring about the lifting of the apparatus by the action of the air striking on the under part of the wings. Once the appa- ratus is in the air, but little effort is needed to sustain and propel it. However, it entails the transport of a motor, heavier than is really necessary, but the extra energy of which is indispensable for starting purposes. This additional weight, in conjunction with that of the carriage, compels " self-starting " aviation apparatuses to carry an excess of weight which may vary from 100 to 150 kilogrammes. The conditions governing " artificial " launching such as is practised by the Wright Brothers are quite different. Freed from the severe foregoing handicap, the American aviators have requisitioned the fall of a weight to obtain the effort necessary to start their apparatus. To avoid any extra weight, even that represented by the wheeled carriage, they glide their aeroplane along a " rail." The launching weight idea is ingenious and effective, as it THE GENERAL PRINCIPLES 125 must impart to the aeroplane an increasing speed. Now the falling speed of a weight increases exactly in proportion with time ; this is the first law concerning the fall of bodies. Consequently, this weight, in its fall, by a rope and return pulley system, draws the aeroplane along, and consequently imparts a speed which increases steadily. Relieved of the extra weight of 100 kilogrammes at least required for " self-starting," the aero- plane thus launched can use an ordinary automobile motor, only a little heavier than the racing types, but working more steadily, instead of the extra light motors used in French aeroplanes, wherein everything being sacrificed to lightness, there may be defects sometimes, especially in regard to endurance. Thus the American aviators are placed in a better position, and have been able to accomplish feats which possibly otherwise they might not have achieved with the same facility ; such flights, however, are limited, inasmuch as they must land near their launching apparatus for fear of being rendered powerless and prevented from re-starting. THE DESCENT When the aeroplane is in steady flight, when it is travelling at its " regulating speed," everything works normally sustentation, advance, steering in the manner we have explained. But the motor may stop, either through the aviator, or accidentally. Let us see now what will occur. By virtue of its acquired speed, the aeroplane continues to advance ; but, propulsion failing, the retarding resistance of the air will be felt more and more, and its speed will be diminished. Yet it must maintain the latter, but, having a motor no longer, it can only do so by descending in an oblique manner towards the earth. Here its weight will serve as the motor ; by its aid the machine can be brought to the ground as gently as the a,viator desires. In the descent, moreover, the steering-rudder will permit the landing-point to be chosen, and the apparatus will settle quietly. Thus, theoretically at least, an aeroplane effects a " descent," but never a " fall." This descending operation is effected readily by French aviators, who have become expert therein. It is needless to say that the greatest presence of mind is necessary to conduct an aviation apparatus; 126 THE CONQUEST OF THE AIR distraction may prove fatal. With presence of mind and skill in manoeuvring, " a motor failure " is no longer dangerous to the aviator ; it merely interrupts his journey. Many persons ask aviators why they do not equip their " heavier-than-air " apparatuses with parachutes. But the foregoing statements will show that this requirement is met fully. It is useless to fit a parachute to an apparatus which in itself is a most perfect parachute. Next we will study the practical arrangements of an aeroplane destined to fulfil everyday service, possessing qualities of safety, solidity, and speed. CHAPTER III AEROPLANE CONSTRUCTION WINGS AND NERVES: MOTORS AND PROPELLERS: SAFETY : WIND AND THE AVIATOR : Is IT NECESSARY TO FLY HIGH? CARRYING SURFACES : THE POWER OF PENETRATION " SUPPOSING the aeroplane to be provided with a motor and a propeller as perfect as possible (we shall go further into the question of these two factors), its essential organ is the sustain- ing or carrying surface. This area is called sometimes the " spread of planes," and the carrying surfaces are known also as " wings." We have seen that there is an advantage in making them slightly concave on the under side. Moreover, they must be placed transverse to the line of travel, whether in a straight line or a very widely opened V. The carrying surface is formed of cloth stretched over a light and strong wooden frame. The same india-rubber fabric as serves for the construction of dirigible envelopes is used often. But all framework is formed of members which have a certain thickness. These offer to the wind a resisting surface. Accordingly, above all things the latter must be reduced to the minimum ; or, in other words, the " power of penetration " of the apparatus must be the maximum. It is preferable to have a heavy piece, representing a heavier load to be lifted and sustained, so long as its shape relative to the resistance which the air will bring to bear upon it, is well thought out. Accordingly it will be advantageous to give the sections of the parts cutting the molecules of air fish-shaped profiles, with the larger end foremost (Fig. 60). These lines are followed in sections of the wings of several existing aviation apparatuses. 127 Direction of motion. 128 THE CONQUEST OF THE AIR The wing framework is pisciform in section and the panels of cloth are stretched on either side of this skeleton. For this reason it will be essential to avoid too many stretched wires, ropes, manoeuvring cords extending to the exterior, and cross-pieces; and if it is remembered that biplanes cannot dispense with the latter, being necessary for connecting the supporting surfaces together, it will be seen how immense is the superiority of the monoplane over the biplane, at least from the air-resist- ance point of view. The latter in their various forms, in FIG. 60. Pisciform section of wings . . , f _ T . . , particular those of Voisin and Wright, offer to the air very needless resistance to advance, since only the carrying surfaces are efficient . For high speeds, which are the aim of aviation, I would be tempted therefore to believe in a much more brilliant future for monoplanes ; those of Esnault-Pelterie and Ble*riot, and the Antoinette aero- plane already represent more than promises ; their early exploits permit one to hope for still more remarkable results. Apart from the transverse sections, there are the nature and character of the sustaining surfaces to be considered. The fabric for the wings must be stretched upon the framework of the wings with the greatest care ; seams, knots, heads of nails must not project in any way. It is imperative that the surfaces should represent, so far as possible, their geometrical definition, be of absolute continuity and regularity, and the fabric, stretched to the maximum, must be varnished also in an extremely careful manner. It is these conditions, difficult to fulfil, which render the construction of varying value, according as to how it is turned out with more or less " finish." It is perfection of workmanship which is responsible for the relatively high price of the present aeroplane ; it is how the French constructors, who have carried it to the utmost limit, have acquired a repu- tation which gives them a superiority equivalent to an absolute monopoly. AEROPLANE CONSTRUCTION 129 MOTORS EMPLOYED IN AVIATION Aeroplane motors must be light, and only the explosion motor, working with the combustion of a mixture of air and petrol gas, fulfils the indispensable reduction in weight. So far back as 1884 Colonel Renard showed that if the weight of the motor, everything included, were reduced to 5 kilogrammes per horse-power, one could realise dynamical sustentation and achieve ordinary aviation. The Colonel's previsions have been fulfilled, and even surpassed to-day, as the motor with a weight of 2 kilogrammes per horse-power is a concrete fact. In regard to the mechanical equipment, we are provided for the conquest of the air. Nevertheless, too much must not be sacrificed to lightness. The motor, if one really wishes to " travel," must be strong and reliable. It must not be liable to heat up too much, since that demands elaborate cooling facilities. In short only a sufficient supply of water should be carried, which, passing through a radiator of large surface, is cooled quickly and completely : all this increases the weight to be lifted, and augments the weight per horse-power of the motor employed. ' How can this essential lightness of the motor be realised ? Two different methods may be practised to secure this end. First there is weight-reduction by the selection of materials. To-day there are steels of marvellous strength, which allow cylinders to be manufactured with walls of insignificant thick- ness ; for example, the barrels of our hunting rifles, which, with pyroxylised powders, resist enormous pressures and yet are not a millimetre thick at the muzzle. Hence, it is possible to have material both strong and light. A second means of obtaining weight-reduction is to dispense with all useless mechanism ; from this point of view the " aviation motors " of the Antoinette make, those of M. Esnault-Pelterie, M. Renault, and even others, are absolutely remarkable. In particular, the design of the Esnault-Pelterie motor, having several cranks working upon the same shaft, and actuated by piston-rods disposed in a radial manner, has secured a considerable diminution in weight. A igle cam ensures the working of the valves. The " Gnome " rotary motor has achieved great fame in its 130 THE CONQUEST OF THE AIR latest applications, purely on account of the simplicity of its mechanism and the reliability of its running. Furthermore, an engine based upon a totally new principle, dispensing com- pletely with cranks and connecting-rods, has been invented by Foddr, a Hungarian engineer. The system is simple, strong, and reliable. It secures an appreciable reduction in weight, and also an increased compactness owing to the suppression of the articulated system. It is a decided step towards the " explosion turbine " which still remains to be evolved. The latter will be invented ; its realisation is essential to the future of aviation because the shocks, inevitable vibrations arising from the oscillating movement of pistons in motors working on the cycle principle, as are used in aeroplanes and dirigibles to-day, impose strains upon the frame, and appreci- ably fatigue the joints in the structure. Moreover, these vibrations are transmitted to the suspension and stretched steel wires, reducing their strength, and in the event of a combined effect might bring about even a rupture through the same cause which has produced so many accidents to suspension bridges. The rotary motor, of which the " turbine " is the ideal, has the advantage of eliminating all these shocks. Will it be possible to design this engine to work by the explosion of a gaseous mixture as it can operate with steam ? It is impossible to say. But at any rate constructors must turn their attention henceforth to this question. If lightness is the paramount condition which the motor must fulfil, it is imperative that strength and reliability in working be not sacrificed. With the successful realisation of this last condition, it will be possible it will be advisable even to reduce the weight of the motor more and more, as absolute safety will only be secured when it is possible to instal two motors on a given aeroplane, each developing sufficient power to sustain and to propel the apparatus. Then the " break- down," the terrible motor failure, which inevitably brings about the descent, if not the fall, of the aviator, will be feared no longer. If one of the motors should fail, the other, already running, could be speeded up; and as each one would be AEROPLANE CONSTRUCTION 131 designed to ensure sustentation, a fall would no longer be dreaded. The great progress that has been made in motors for some time past permits us to believe that this hope will become a reality at no distant date. THE PROPELLER : SCREWS The only propeller used in aviation (except with ornithopter apparatus) is the screw. We have explained its general properties in speaking of dirigible balloons ; we have defined its " pitch," as well as the " slip," resulting from its working in the air. But we must revert to the subject somewhat in speaking of its application to aviation apparatuses. At present we are not very well supplied with really reliable data concerning aerial screws ; the excellent works of Colonel Renard have elucidated the question without solving many individual points. Experiment alone can furnish data as to the practical value of a screw. But in such research operations it works " at a fixed point," that is to say, moves upon an immovable dynamometer, which gauges its mechanical effort. This data is not absolutely sufficient, as in aerial operation a screw does not furnish the same useful effect as when working at a fixed point. Yet such data is necessary, and therefore, above all, tractive experiments by means of a dynamometer with each screw must be made. Once this result has been obtained, a serious question of vital importance will arise, since, according as to how it is settled in one direction or the other, there will result aviation apparatuses presenting features and qualities widely dissimilar. This question is : Should the screw be of small diameter, and revolve at high speed, or, on the contrary, should it be very large, and turn " slowly " ? These two ways of planning the propeller have given birth to " two screw-propeller schools." Both solutions have been tested. Large screws were the first to be used, especially on dirigibles, and in particular on those of Giffard, Dupuy de Lome, and Renard. This condition, moreover, was compulsory at the onset, owing to the slow speed of the motors employed. But when the explosion motor, with its very high speeds of 132 THE CONQUEST OF THE AIR revolution, entered aeronautical practice, preferences changed, and there was a rush on small screws turning very rapidly. There was a fear that the actual rotating speed of the motor would be " reduced," and it was desired to govern the screw directly by the engine by mounting it direct upon the shaft of the latter. Thus we see the Lebaudy dirigibles, the Voisin machines, the immense airship of Count Zeppelin, fitted with small screws running at a speed ranging from 1000 to 1500 revolutions per minute. The appearance of the Ville-de- Paris and Bayard-Clement airships, fitted with large screws running at from 300 to 400 revolutions only, and especially the remarkable performances of the Wright aeroplane, the two screws of which rotated at a fairly low speed, served to support those who maintain very justly that the employment of large diameter screws is more advantageous. To-day there seems a more general tendency in the direction of screws of greater diameter and revolving less rapidly. Another question, quite as important, is as to whether one or two screws should be used. In principle, two screws, one running to the right, and the other to the left, thus revolving in opposite directions, are preferable in every way. In fact, with one screw only, the aeroplane tends to swing in the direction of its rotation, and its great surface alone prevents this deviation from becoming serious. With screws of opposite pitch and direction, these two effects become neutralised, the one tending to bring the aeroplane to the right, and the other to the left. The motive effort is then quite symmetrical. But the use of two screws may in certain instances present a great danger, and for the following reason. Let us suppose an aeroplane provided with two screws (Fig. 61 A) driven by identical motors, or by equal transmission of the energy from a single motor. Each has a turning effect following its axis, and as they are placed symmetrically with regard to the centre of the supporting surface, the resulting propelling effort is steadily applied at one point of the symmetrical plane of the whole contrivance. But if one of the two screws the right, for in- AEROPLANE CONSTRUCTION 133 stance for some reason should cease to act (Fig. 61 B), either through a fracture or failure of the engine which drives it, the aeroplane is instantly subjected to the action of one propeller alone the left one. This movement is eccentric. The apparatus is subjected to a propelling effort which in itself is Pi ill < i w-f< Ri^ht hand screw net- working. (A) (B) FIG. 61. Propulsion of an aeroplane by two screws A, with the two propellers ; B, with one only eccentric, and it tends to assume an oblique direction. The machine assumes the position too quickly for the aviator to correct it in time by means of the rudders, and a fall may be the result. This was, unfortunately, what happened with one of the Wright aeroplanes. Orville Wright, having on board an officer of the American army, Lieutenant Selfridge, was a victim to this contingency. The aeroplane fell, the officer was killed, Orville Wright had an arm broken, and had to rest for two long months. From the point of view of safety, the use of a single screw is, therefore, much preferable. If it is absolutely desired to use two, it is essential that the disconnection or stoppage of one should arrest the motion of the other, and that by automatic means, as, for instance, the transmission of the power through a single chain. Under these circumstances, in the event of failure in propulsion the aeroplane would be in the plight of an 134 THE CONQUEST OF THE AIR ordinary " breakdown," and in its forced descent could make a " glide " through the air. Lastly, one more doubt might arise in the mind of the con- structor : should the screw or screws be placed at the bow or stern ? In other words, should one have screws which " draw " or screws which " drive " ? Opinions and practice are divided. In the French machines such as those of Bleriot and Latham the single screw is at the prow. In the Farman aeroplane, it is at the stern of the carrying surfaces. The Wright Brothers have adopted this arrangement for their two screws, which are '* driving propellers." All these aeroplanes have shown different qualities, but such as are incontestable. It is therefore im- possible to declare off-hand in favour of one or the other, and the position of the screw will depend upon the wing-spread, the empennage, and more or less upon the long leverage of the latter. THE "BODY" OF THE AEROPLANE There is, also, one part of the aviation apparatus which we have neglected up to now, but which is nevertheless indispens- able. This is the "body" which plays the part of the car of the dirigible, that is to say the space designed to carry the motor, the propeller, and the aviator, the " brains of the machine." The "body" represents the serviceable part of the aero- plane, since it carries the travellers ; but it has dimensions, and these cannot be avoided, however small tke design may be. Therefore it will present to the air a resisting surface, which must be taken into consideration. In the Wright Brothers' aeroplanes there is no " body." It is reduced to that of the aviator, sitting over empty space on a latticed seat, with the feet resting upon a cross-bar. This is an arrangement possible with operators as clever, as " artistic," as masters of their nerves, as Wilbur and Orville Wright, but in my opinion it is an arrangement to be condemned absolutely. Aviation is already a sufficiently daring form of aerial travel without increasing the risk, by decreasing the conditions ot safety. Practical aeroplanes of real value, such as those of Bleriot, Voisin, Farman, &c. . . . all have a " body " serving as accommodation for the aviator and the machinery. This body, being compulsory, it is necessary to utilise it to AEROPLANE CONSTRUCTION 135 the best advantage for the balance of the machine. First of all, we must give it, undoubtedly, the shape of the body of a bird or fish, with the large end to the front. Under these con- ditions, and if the framework is carefully covered with fabric tightly stretched and very smooth, its resistance to advance will be reduced to the minimum. This body, moreover, will serve a useful purpose ; it will increase the lateral resistance, that is to say, oppose " drift " and the action of centrifugal force when turning. Thus planned, the shape of an aeroplane becomes closely allied to that of a soaring bird. The action of the air upon the various parts of this " body," however, must be studied carefully as regards stability in the direction of travel, and here it is that Colonel Renard's work must be borne in mind. More than ever (as we have already said) the empennage is here indispensable to secure the safety of the apparatus. AEROPLANES AND SPEED : AEROPLANES OF THE FUTURE The real great advantage of aeroplanes in their application to aerial travel is speed. In all trials wherein somewhat pro- longed flights have been accomplished, it has been seen that the present speed of aviation apparatuses is at least 60 to 70 kilo- metres per hour. In Farman's now historical journey from Rheims to Chalons on his French-built (Voisin) aeroplane, not only did the daring aviator achieve the first " aerial journey " worthy of the name, leaving a field of experiments to pass over villages and forests, but he even made it at a speed of 78 kilo- metres per hour. Again, recently, the speed of 105 kilo- metres an hour, exceptional it is true, was attained. No dirigible, at least at present, can equal such a performance, and the speed record in the matter of aerial navigation consequently belongs to the aeroplane. Can this speed be increased ? Not only can it be increased, but it must be increased, if it is intended to make really practical use of aviation. At an important conference held at the French Society of Aerial Navigation in December 1908, the engineer, M. Soreau, a former pupil of the Ecole Polytechnique, dealt with this 136 THE CONQUEST OF THE AIR question in his highly competent manner. He selected for his purpose a " family " of aeroplanes of the type constructed by the Voisin Brothers. Supposing all to be provided with motors giving the same weight per horse-power, propellers having the same output, and wings having the same co-efficient of efficiency he showed that the maximum useful weight would be obtained with an aeroplane having dimensions only 10 per cent, heavier than the existing aeroplane. But its speed must be tripled, that is to say must reach the figure of 180 to 200 kilometres per hour. Then the " useful " weight would reach one ton. But, when our "artificial birds" shall have realised such speeds, when they can carry such weights, it will be possible no longer to be content with this construction of slender framework, a marvel of lightness, certainly, but lacking solidity. It will be necessary to make all its component parts very strong, to enable them to resist even the greatest strains to which they may be submitted. Let us cite here M. Soreau's important conclusions : " aeroplanes of large carrying capacity will have to be very stoutly built, not much larger than at present, at least for the next few years to come, but their speed will have to be double or treble that in vogue to-day. Now, for these new machines we shall be forced to employ other materials. It will be necessary in particular to attend to the reduction of their resistance to advance ; in short it will not suffice to be content with constructing aeroplanes based strictly upon existing lines. These new apparatuses, so soon as they shall have been perfected and have received the sovereign sanction of experience, thus will become the first aeroplanes of a new family," and so on. Hence aviation apparatuses will be perfected by " evolu- tion," which is the case in nearly all the great developments realised in physical science or applied mechanics. What must be remembered in these conclusions of one of the cleverest aero-mechanics of to-day is that before long, even very shortly, we shall see general speeds of 200 kilometres per hour. Truly then it will be possible to say that " distance no longer exists." Moreover, we may say that these high speeds are necessary. Painful accidents have occurred only too fre- quently owing to the aerial eddies overturning the apparatuses flying through the air. If the speed is very great, the power AEROPLANE CONSTRUCTION 137 imparted to the machine, which increases as the square of the speed, will render it insensible to the slight fluctuations in the atmospheric currents, and it will pass through the eddies as the high-speed torpedo boats of to-day steam through the waves, or as the projectile whistles through the air, indifferent to the caprices of adverse currents. WIND AND AEROPLANES What we have said regarding the action of the wind upon dirigibles applies equally well to aviation apparatus ; " Wind does not prevail for the aeroplane which moves in the atmo- sphere. It is as if this atmosphere were immovable. Wind only exists on account of the aviator changing position in relation to the ground beneath" Consequently, we shall have to consider the same values in aviation as in aeronautics. If the independent speed of the aeroplane is less than that of the wind, it will be able to approach only the points of the space contained within a certain " approachable angle." If its independent speed equals that of the wind it will be able to approach any point to leeward of the line perpendicular to the direction of the wind at its point of departure. Lastly, if its independent speed is greater than that of the wind, it will be able to go anywhere. In all cases, its speed is governed by that of the wind in regard to resulting movement. In an extreme case when it flies with a dead following wind its travelling speed, with regard to a fixed guiding- mark taken on land, is equal to the sum of the speeds of the wind and of the aeroplane. It equals their difference if the aviator navigates against a " head wind." As to-day a speed of 78 kilometres per hour is possible, it is evident that, at present, an aeroplane can set out around Paris on an average 352 days out of 365; when a speed of 150 kilometres per hour is reached, it will be possible " to start out every day." I insist most particularly upon this notion, as it is often distorted or acquired in an incorrect manner. For instance, if an aeroplane is travelling in an easterly direction in a south wind of 20 kilometres per hour at an independent speed of 60 kilometres per hour (Fig. 62) it will navigate effectively with a speed of 60 kilometres per hour; but the " section of atmo- 138 THE CONQUEST OF THE AIR sphere " in which it will have effected these 60 kilometres will be displaced 20 kilometres towards the north, owing to the Arrival Point 60 kil. FIG. 62. Combined action of wind and propulsion speeds Instead of following a straight line, the aeroplane uriU describe a diagonal route effect of the southerly wind. Thus the aeroplane will have followed an oblique trajectory, represented by the diagonal of (l) (2) FIG. 63. Wind and the aeroplane : actual and relative routes respectively The whole moves as if wind were non-existent, but as if the earth travelled beneath the aviator at a speed equal, but contrary, to that of the wind the parallelogram constructed with the help of two speed its own independent speed and that of the wind. This conception may be " materialised " even, so to speak, in the following manner. Let us imagine an enormous aerostat, formed of a perfectly impermeable envelope, and maintaining its equilibrium high in the air (Fig. 63). We will suppose that this balloon has dimensions sufficiently large for an aero- AEROPLANE CONSTRUCTION 139 plane to be able to describe evolutions in its interior atmosphere. This atmosphere will be sheltered completely from the action of the outer wind, since it is enclosed in an air-proof envelope ; the aeroplane will therefore manoeuvre in still air, and will go from A to B, but during the time it will take to accomplish this journey, the whole balloon will have been transported by the outer wind from (1) to (2). Certainly the aeroplane will arrive duly at point B, but this point B will have been transported without the aviator being aware of the fact to B 1 ; so that he will have no longer below him the part of the terrestrial surface which was below point B, but really that which is below point B 1 . Now let us imagine the envelope which isolated the interior atmo- sphere of the aerostat to be removed ; nothing is changed in the general conditions, but we can thus understand the true road, AB 1 , of the aeroplane. HEIGHT AT WHICH IT IS ADVISABLE TO FLY : SAFETY The height to which it is advisable to rise to practise aviation is connected intimately with the conditions of safety laid down by the aviator. At first sight it may be imagined that it is essential to decrease the risks of accident by navigating very closely to the ground; to sweep closely to the earth like swallows because, it may be thought that " if one fall, one will fall from a lesser height." This reasoning is admissible for risks entirely " experi- mental " ; when one is not quite sure of the stability of the apparatus in which one is to ascend. But once this apparatus has been tested, and once the efficiency of its equilibrium has been ascertained, then it is necessary to avoid too close a proximity to the ground, and to navigate at a certain height, say, at about 100 metres. As a matter of fact, let us consider what takes place in the immediate neighbourhood of the ground (Fig. 64). The moving molecules of the air, the horizontal displacement of which constitutes the wind, are forced, when brought into immediate contact with the terrestrial surface, to follow all its superficial variations and to become deflected by its 140 THE CONQUEST OF THE AIR projections. The gaseous molecules thus follow, approximately, the undulations of the ground, in at one time an ascending, and at another moment a descending path, and if their speed is of little consequence, that is to say, if the prevailing wind is not very intense, these inflections of the currents of air Area, of steady \vind. FIG. 64. Effect of inequalities of the ground surface upon the movement of the air The horizontal currents are deflected by the irregularities of the ground, which set up vertical currents cause " ascending winds '' and " descending winds," as is illustrated in Fig. 64. Now the aeroplane is so designed that the currents of air are met horizontally by its wings, and not so as to be struck in an oblique manner. These vertical winds therefore will be capable of " twisting " the aeroplane round, and so placing it that in its fall it will no longer meet the air by its extended surface, but with its side. This will bring about a sudden descent, in other words, certain death to the aviator. These atmospherical fluctuations disappear in proportion as one rises into the air, and at a certain height, as is shown in our sketch, the strata of air becomes steady and flows in a horizontal manner, being q'uickened solely by those " un- dulatory movements " so ingeniously described by M. Soreau. It will be only at these altitudes that the aviator will be sure to find the normal laws of the atmosphere ; it will be at these heights that he will have to fly if he will desire his aeroplane AEROPLANE CONSTRUCTION 141 always to be " under the best conditions " for which its various elements will have been calculated. Lastly, it will be from where, in the event of a breakdown to his motor, he will be able to make the " glide " through the air, which, with a soaring flight, will carry him safely to the ground ; whereas he will not be able to effect such if he be caught in a current of ascending air which will capsize his aeroplane and infallibly precipitate a fall. This descending glide will be effected with the greater safety inasmuch as it will commence higher above the ground, and also because the aviator will be able better to select his landing-point. In the early days of aviation, it was often asked if the highest altitudes would not be impossible to the aeroplane ; if the greatly rarefied oxygen would be insufficient to bring about the combustion of the gaseous mixture, the explosion of which supplies the requisite energy; and whether the carrying surface could be supported owing to resistance from a thinner atmosphere. Would these conditions be sufficient to assure the sustentation of an aeroplane which would possess sufficient stability no longer ? In the case of average altitudes (between 100 and 1000 metres) easily accessible to the aeroplane such objections do not exist. At a height of 100 metres, the supporting power of an aeroplane's wings is not reduced, owing to the density of the air being diminished by no more than -^ of its value at ground level. In regard to the highest altitudes, demonstration has dispelled triumphantly apprehensions on this point, for aviators have already reached extreme altitudes. The French aviator Paulhan, at Los Angeles, U.S.A., in 1910, rose to a height of 1260 metres; Latham, on July 7, 1910, mounted to 1384 metres; on July 30 Oliesloegers notched 1524 metres; and a Belgian aviator, Tyck, on August 1, 1910, gained a height of 1700 metres. But the two record-breakers in height are Morane, with 2521 metres and Chavez with 2646 metres! On September 20, 1910, the last-named succeeded in crossing the Alps, from Brigue to Domodossola, over the crest of the Simplon. The question of safety is connected closely with that of landing, and the latter is, as may be easily understood, of 142 THE CONQUEST OF THE AIR the greatest importance to the aviator undertaking an aerial journey. " It is not all skittles, I must get out of this," said La Fontaine's fox. It is not only flying : one must regain the ground, and return thereto without breaking one's bones. Now, calculation, and calculation based upon experi- mental data, shows that for a given aeroplane, there is a minimum motive power necessary to obtain the "governing speed." So soon as a motive power exceeding the minimum is brought into play, two results and, consequently, two speeds are possible. Thus, if we have a motor the power of which exceeds the mimimum speed by 4 per cent., the two speeds will in one case be 18-100ths in excess, and in the other 17-10 Oths less than the governing speed, accord- ing to the inclination of the wings. If the motive power exceeds the minimum power by 15 per cent., the two possible speeds are, the one a third in excess of the necessary speed, the other one-quarter less, according as to whether the wings are inclined more or less by the action of the elevator. Thus, since it is possible, by means of a slight excess of power, to have two speeds at disposal, it will be possible, as M. Soreau remarks, to use the greater for the " travelling speed " of the aeroplane, and the lesser one for landing, which thus will be effected without danger, for when the apparatus has approached closely to the ground, the fall caused by the excessive inclination of the wings will be deadened appreciably by the " mattress of air " interposed between the ground and the supporting surfaces. It is when alighting that the mechanical absorbers, upon which the wheels of the launching carriage are mounted, become indispensable. Undoubtedly, the landing of heavy aeroplanes will require elaborate precautions, and will demand extreme cleverness and presence of mind on the part of the aerial pilot. How do accidents happen ? From two different causes the sudden stoppage of the motor, or the breakage of one of the essential elements of the aeroplane. This last possibility scarcely can be admitted, since, if the aeroplane has been well designed and carefully constructed with first-class mate- rials, the strength of which has been thoroughly determined ; if, moreover, all parts of the apparatus have been examined g a o e 32 H 5- >. w o AEROPLANE CONSTRUCTION 143 carefully before each ascent, and the mounting, connection, and assemblage have been inspected in detail, when built, the un- expected breakage of any essential part should not develop. But, you will say, there are the road accidents ? No, not in aviation ; for on the " highway of the air " there are neither shocks, buinpings, nor collisions to be feared, at least not at present ; this road is wider than those which traverse the earth in all directions, and there is not only more room to pass one another horizontally, but it is also possible to keep clear of other machines " above or below." Moreover, our aerial roads are not overcrowded, at present. Again, the governing speeds not varying very much, the movements of the different con- trolling mechanisms are not subjected to appreciable fluctuation. There remains motor failure ; but we have pointed out, in speaking about explosion engines used in aviation, that their continuous development will bring about the desired reduction in weight. Very soon, therefore, we shall have motors at our disposal, the weight of which will be reduced sufficiently for it to be possible to carry two engines weighing no more than, and each of the power of, the single existing motor ; that is to say, either will be sufficient to sustain and to propel the aeroplane. Under these conditions, together with a device automatically setting the second motor in motion in the event of sudden stoppage of the first, engine failure will be feared no longer. In any case, should this occur, it would be dangerous only over towns, where descent would be hazardous, if not fraught with danger, or above forests, owing to the trees, which would injure passengers possibly and prove disastrous to the wings. There, is, however, one part of " the terrestrial globe " which offers danger descent on water. Undoubtedly, the large surface of the wings can prevent the apparatus foundering immediately, but the aviator, pinned under the planes and " entangled " in the wings, might not be able to disengage himself without difficulty. It will be advisable to provide aeroplanes, intended for long journeys, with special safety contrivances, in view of a descent upon water. " Accidents " will happen. Undoubtedly, daring pioneers in the air will forfeit their lives in the desire to score 144 THE CONQUEST OF THE AIR another victory over the forces of Nature. But have not all the conquests of human genius navigation, railways, the motor-car, even current industry been effected at the cost of heavy sacrifices! And are not the "accidents" of daily life as formidable as those to be feared in the new method of locomotion, which will be attended, however, with less serious results, because, reputably more dangerous, it will be practised with greater care ? OTHER FORMS OF AVIATION : HELICOPTERS AND ORNITHOPTERS At the commencement of this study of aviation, we said there were three types of apparatus " heavier than air." We have investigated in detail those which have given the most practical results so far aeroplanes. It now remains for us to speak about the other two. The first is helicopters, that is to say, apparatuses which hold themselves in the air, not through the vertical component of air thrust upon a moving surface, like kites, but by the direct sustaining effort of a screw, having horizontal blades, revolving about a vertical axis, and driven by the motor. It was the helicopter which first haunted the brains of aviators. As far back as 1852 Ponton d'Amecourt and de la Landelle, buoyed up by the enthusiasm of Nadar, the celebrated photo- grapher, by Press campaigns, conferences, &c., maintained that the future of the " heavier than air " machine would be by means of the screw the " sacred screw," as it was called by Ponton d'Amecourt. Their scientific support was Babinet, a member of the Academy of Sciences, and he it was who evolved the name " helicopter " to baptize the apparatus which he thought would realise the absolute conquest of the air. What gave weight to the assertions of these tireless apostles was the popular success of flying toys, real miniature helicop- ters. These ascend with the greatest ease, either through the effort of twisted india-rubber, or from impetus imparted by uncoiling a string, and appear to defy gravity and to point to the " highway of the air." Intellects were fired ; controversies became furious ; a study was made of the manner in which the screws should be AEROPLANE CONSTRUCTION 145 arranged. To avoid the rotary movement which a single screw imparted to the body of the apparatus, a vertical " resist- ing plane " had been introduced into certain types of this toy, which opposed itself to the rotation of the whole. The danger of this plane was soon grasped, as, remaining nearly vertical, it offered too considerable a purchase to the wind. The funda- mental point in the construction of helicopters was recognised, therefore, to be the simultaneous use of two screws turning in opposite directions about vertical axes. In this manner the effects of torsion, due to each of the two propellers, were equal and contrary. In other words, they destroyed one another, whilst their lifting efforts were combined. An automotor helicopter was constructed on this principle by Dr. Hureau de Villeneuve. There was a small steam-engine, driving two inverse screws revolving in opposite directions about the same vertical axis. All helicopters realised or planned hitherto comprised the use of an even number of screws of contrary pitch, revolving in opposite directions to one another. Experiments were made with helicopters, but with little success. Why, is known to-day. The motors used were too heavy, and the intimate scientific discussion of the problem by mathematicians discouraged investigators from embarking on these lines for a long while. Then Colonel Kenard tackled the question, which, as usual, he elucidated in his works on sustaining screws. In a communication which he made to the Academy of Sciences at the end of the year 1903, Colonel Renard gave the results of his long researches, carried out at Chalais-Meudon, with screws employed for lifting a certain weight directly from the ground that is to say, with " sustaining screws." He had demonstrated already that aerial navigation by aeroplanes would be possible when the weight of the motor was reduced to 5 kilos per horse-power. Devoting his remarks to the helicopter, the learned Colonel showed that the maximum weight which the screws of this apparatus would be able to lift would increase inversely to the sixth power of the weight per horse-power of the motor employed. This result strongly encouraged helicopter inventors, but we must reckon not with theoretical "limit" loads, which it would be impossible to 146 THE CONQUEST OF THE AIR exceed, but with the real loads compatible with the resistance itself of the screws. Under these conditions a really trans- portable load limit is obtained quickly, and these loads are lighter for the helicopter than the aeroplane. Hence the enthusiasm manifested in this apparatus is distinctly explic- able. In 1904, Colonel Kenard even suggested sustaining screws of 2 '50 metres diameter, of perfect resistance, and not liable to distortion under the effect of thrust, although their total weight was very small. He obtained this result by intro- ducing a universal joint which permitted the screw- shafu to assume the resultant direc- tion of the various efforts bearing simultaneously upon it. Amongst the various dis- positions proposed for heli- copters, there is one conceived and constructed by Engineer FIG. 65. Principle of the Leger helicopter Two screws of concentric axes revolve in opposite directions, and, their common axis may be inclined for horizontal pro- pulsion Leger, under the auspices of H.S.H. Prince Albert of Monaco. Its principle is shown in Fig. 26. The two screws of contrary pitch, turning in opposite directions, are mounted upon two concentric axes. Each axis being vertical, lifts the car ; but, if the axis is inclined, as shown in the figure, an oblique movement through the atmosphere must result. The apparatus has been tested at Monaco, and the vertical elevation of an experimenter has been effected. A composite solution, of which Colonel Renard himself had thought, has been proposed. It is an apparatus which would be a helicopter for lifting itself from the ground, and would become an aeroplane once in the air. Such a solution, if it were ever practicable, would solve an acute problem, since the great disadvantage of aeroplanes is the necessary " launching " space. So long as there is level ground, or even broad roads, ascent is quite a simple task. But in wooded or mountainous AEROPLANE CONSTRUCTION 147 country an aeroplane having landed, cannot re-start, whereas if it had a screw and vertical axis, which would lift it perpen- dicularly, departure would be easy, and once raised into the air, the apparatus would have the advantages of an aeroplane. It is to be hoped that serious investigations will be made in this direction ; success will constitute a great development, and perhaps even the future of aviation. The " gyroplane," which we describe later, is a decided step in this direction. Ornithopters, those apparatuses with " flapping " wings, seeking to imitate exactly the process of lifting and sustentation which characterises the flight of birds, have been tested less than helicopters. The difficulties of construction are so much greater, and the vibrations and shocks to which their framework is subjected cannot fail to tell on the joints. Despite these diffi- culties, a Belgian aviating engineer, M. Adhemar de la Hault, has devised an ornithopter, which we illustrate. In the latest experiments, this apparatus was able to rise slightly and to leave the ground for a moment, but an accident to one of its parts interrupted the trials, which are to be resumed later. COMPOSITE SOLUTION : SOARING BALLOONS : CAPAZZA'S LENTICULAR There remains another composite solution for us to mention. This does not consist of a combination of two systems of aviation, but a balloon and a soaring arrangement. It is an attempt recalling those sailing-vessels known as " auxiliary-engined " craft, often used in trade and pleasure navigation. Its inventor, M. Capazza, a French aeronaut with the finest " aerial " career (he was, in fact, the first aeronaut to cross the Mediterranean from Marseilles to Corsica, and in a balloon, which has not yet been repeated), designed an immense aeroplane, but with its sustaining plane lighter than air. He uses a balloon, not of the ordinary spherical or pisciform shape, but having the flat form of a lentil. This lentil, however, is not symmetrical, as regards its centre ; it is not a " surface of revolution." Its greater thickness is brought to the bow, so that, cut in the direction of its axis, its section is that of a fish (Fig. 68). A longitudinal empennage forms, above and under this envelope, a kind of aileron, a " keel " which contributes to 148 THE CONQUEST OF THE AIR stability, which is increased still more by an horizontal empen- nage at the stern. The whole of the stern of this lentil, thinned to its back edge, in reality constitutes a marvellous natural empennage. The total capacity of this envelope is 15,000 cubic metres, and it is reinforced internally by metallic circles. These Vertical fin. Front Screw left Rudder. Stern screw. Front motor left Stern motor FIG. 66. Side elevation of the Capazza lenticular balloon support a car in which are three motors of 120 horse-power each, driving three screw-propellers. The weight of the car carried below the is greatest thickness of the balloon, i.e., well forward of the centre, as shown in the diagram. The interior metallic hoops distribute the load over the whole surface of the envelope. At first sight the apparatus works like a dirigible: but, on account of the flat and non-symmetrical shape of the envelope, it possesses additional properties. Let us imagine a movement of ascent or descent being imparted to it. The apparatus will become inclined immediately, as the two areas, that of the bow and that of the stern, will be pressed unequally by the air ; the back area offers a greater resistance to ascent or descent than FIG. 67. Front view of the lenticular balloon AEROPLANE CONSTRUCTION 149 the front. If, for instance, the movement is ascending, the stern will be depressed, the bow will rise up, and the vertical ascensional movement will be transformed into an oblique displacing movement towards the bow. The screws will add their propelling action to what is thus obtained, and will help, according to the expression of artillerymen, to " flatten the Circular metal stays 'central shatt Rudder .Elevating rudder. FIG. 68. Plan of Capazza's lenticular balloon trajectory." The direction of the balloon will become the more horizonal as its independent speed will be increased. Now let us suppose that at a given moment the total weight of the apparatus, envelope, car, motors, passengers, and cargo, for some reason or another, exceeds the weight of air displaced, say either because the lenticular balloon in rising has gone beyond its zone of equilibrium on account of its acquired speed, or because physically the inner gas has contracted, and which the ballonnet will have replaced with air : the balloon will tend to descend immediately, but an inverse phenomenon will occur. The greater surface of the stern will lift, and the balloon will become inclined ; it will descend, but in gliding in an oblique manner upon the molecules of air in the manner of an aeroplane, will utilise 150 THE CONQUEST OF THE AIR this descending movement to progress horizontally. This effect will be added to the speed imparted by the screws, the propelling force of which will thus be increased by successive ascents and descents. Such is this ingenious, curious apparatus, which is so original in its conception, and which it would have been impossible to let pass without saying a few words. It would be very interesting to see it realised, for, apart from the services which it would render as an airship, it might become a veritable experimental laboratory for everything concerning aviation. CHAPTER IV DESCRIPTION OF SOME AEROPLANES I. BIPLANES FRENCH AND AMERICAN DESIGN : THE VOISIN AND WRIGHT AEROPLANES : COMPARISON OF THEIR EFFI- CIENCIES AND DISADVANTAGES THE VOISIN AEROPLANES WE will now proceed to describe, somewhat more in detail, the various types of aeroplanes; at all events, those which have accomplished brilliant flights, afad consequently have demonstrated their efficiency. And it is necessary, in all fairness, to begin with the excellent aeroplanes, swift and sure, built by the Voisin Brothers, the eminent French con- structors. Their name, as a matter of fact, is inseparable from those of the daring spirits, who, in France, opened the highway through the air by their magnificent achievements : I mean Messrs. Henri Farman, Delagrange, Rougier, &c. The details given in the preceding chapters will enable the reader to appreciate and to compare better the different machines which we will now describe in turn. We will mention first the original Voisin machines. These apparatuses, in a way, are historical, as they' were th'e first aviation appliances in Europe. The present craft do not differ from their " prototypes " except in modifications of detail, and reference to the illustrations will help to reveal these divergences. The Voisin aeroplanes of the original type belong to the " cellular " biplane class. Between the two parallel supporting surfaces which constitute the wings or planes are vertical walls, formed of fabric stretched over the cross members, designed to oppose lateral deviation and to maintain automatically the 151 152 THE CONQUEST OF THE AIR equilibrium of the aeroplane when turning. The general arrangement of this system is shown in Fig. 30. In the recent Voisin biplanes the builders have suppressed the vertical walls. The design combines strength and lightness. The wings are of india-rubber sheathing stretched upon a diagonally braced ashwood frame. The spread of the wings is 10'20 metres ; depth 2 metres ; and of the " stays," which vertically maintain the distance between the two supporting surfaces, 1*50 metres. These surfaces are slightly curved, the concave face being presented towards the earth. When the apparatus is in flight, the " chord " of the arc formed by the profile of the wings makes an angle varying from 6 to 8 degrees with the horizontal. The surface of this plane is about 40 square metres. The whole of the supporting surfaces, called the "central cell," has a balancing apparatus or " empennage," formed of a "rear box" which also follows the form of a biplane, of less spread than the central cell 3 metres long only, by the same depth of 2 metres, spaced 1-50 metres apart, and curved like those of the principal planes. This rear cell or "tail" is placed 4 metres behind the central cell, and between its two surfaces is placed a plane moving about a vertical axis which constitutes the rudder. The superficies of this rear cell is thus 12 square metres, which brings the total area of the planes to 52 square metres. The "body" of the aeroplane is a wooden framework with cut- water or wedge-shaped ends covered with carefully stretched canvas. Its greatest width is 75 centimetres; length 4 metres. The aviator's seat is so placed that when he is seated the centre of gravity is at a point which extends vertically 2 5 centimetres from the front edge of the supporting surface (edge of attack) ; in front of the seat are placed the wheel and the pedals controlling the rudders. This body carries the elevator composed of two surfaces projecting on either side of the prow and moving upon a common horizontal axis. The shape is plane-convex, the plane being turned always towards the earth, and the convex side to the sky. BIPLANES 153 The engine is an eight- cylinder "Antoinette" motor developing 40-50 horse-power; it has eight cylinders, and "Wings Rudder. Elevating rudder. Tail -- plane Screw. * Mot or. x.z. FIG. 69. The Voisin aeroplane (Delagrange type) weighs 80 kilogrammes. It is so mounted upon the body that its centre of gravity is a trifle forward of the rear edge of the carrying surfaces. The screw-propeller has two blades; it is placed astern of the central cell. It is built up mainly of steel tubes covered with sheet aluminium. Its diameter is 2 metres; it is coupled direct, without any reducing gear, upon the motor shaft, and runs at a speed of 1050 revolutions per minute. 4 154 THE CONQUEST OF THE AIR The whole is carried upon a wheeled carriage built of tubular steel having four pneumatic-tyred bicycle wheels. II G ir-- Screw Motor Tail planes A Z FiG. 70. The Voisin aeroplane (H. Farman's type) Those in front which directly support the central cell and motor are of 50 centimetres diameter; the rear are of 30 centimetres diameter. The total weight of the apparatus together with the aviator is 530 kilogrammes. Such is the simple and solid aeroplane with which Henri Farman demonstrated the prowess of which we spoke in relating the history of aviation. This aeroplane has under- gone some modifications; its pilot fitted at the front a third surface above the first two, thus converting it into a p < EH a 63 EC g Tc " "S" g I o 2 8 p - : PLATE XXXII THE WRIGHT AEROPLANE AT THE MOMENT OF LAUNCHING BY THE FALL OF A WEIGHT IN THE DERRICK THE WRIGHT AEROPLANE IN FULL I LIGHT 7 3 liotos, Branyer WILBUR WRIGHT AT THE WHEEL OF HIS AEROPLANE SHOWING THE TWO CONTROL LEVERS BIPLANES 155 " triplane " ; but the enthusiastic aviator seems to have renounced this adjunct, and to have reverted apparently to his original biplane. This machine attained a speed of 79 kilometres per hour in the journey from Chalons to Rheims, covered at an average height of 40 metres (27 kilometres in 20 minutes). The Voisin aeroplane steered by Delagrange in his early flights (Fig. 70) vividly recalls the Farman aeroplane in its broad lines, which is not surprising, seeing that it came from the workshops of the same constructor. The only difference is a space of 3 metres between the central cell and the rear balancing cell. Having given the details of the Henri Farman aeroplane, the diagram explains itself sufficiently ; otherwise further details of the Delagrange aeroplane may have been necessary. Its total surface is 60 square metres, and it has attained, with a 50 -horse-power Antoinette motor, and a screw of 2*10 metres, a speed of 70 kilometres per hour. Its total weight is 450 kilo- grammes. Since the first flights of H. Farman and Delagrange, accomplished in 1908, and which already appear so long ago the advance has been so great as to be a huge stride the Voisin Brothers no longer trouble about their achievements and victories. Their machines represent one of the most stable and most reliable " heavier than air " apparatuses in aerial naviga- tion. We will refer to their latest triumphs later on. THE WRIGHT BROTHERS' AEROPLANE We have shown a remarkable aero-biplane of French con- struction which fulfils automatic stability, be it longitudinal or lateral. Let us now give, in some detail, a description of the famous aeroplane which created widespread enthusiasm during the summer of 1908, and the prowess with which (we are apt to forget, perhaps a little too quickly, this attribute of the French aviators) would seem to show decidedly the " path through the air." In short, we will compare the American aeroplane with those which we have already described. The machine, evolved by the brothers Wilbur and Orville Wright, in its earliest form is, like the Voisin aeroplanes, a biplane, with an elevator in front and a rudder at the stern. 156 THE CONQUEST OF THE AIR Its main feature is the absence of a fixed balancer. The " foundation," that is to say the total length of the system longitudinally, is 9 metres. The two surfaces of the biplane have a spread of 12 '50 metres each, by 2 metres breadth. The fabric of which they are made is stretched to the utmost upon two wooden frames formed of two longitudinal members strengthened by a series of transverse pieces. Each of the latter is doubled, and formed of two incurved laths, which are kept taut by wedges at the stern. This latter, very fine, very thin, extends to the rear part of the wings a certain elasticity, a sufficient suppleness, to facilitate the " warping," by which means the celebrated American aviator secures the lateral stability of his aerial vehicle. Steel wires stretched diagonally assure the indeformability of the wings. The fabric is riveted to the front edge of the plane members ; at the back, to secure the finest possible finish, the edges are sewn together. The two planes are 1/80 metres (6 feet) apart, and this spacing is secured by vertical bracings, some of which are rigid and others articu- lated. Those of the centre, by means of diagonal supports, constitute indeformable parallelepipeds, in such a way that those of the extremities, fixed to the wings by screw rings, are able, through the articulation, to submit to warping which will deform the extremity slightly. The planes rest upon two skids which form a kind of sleigh, because it may be necessary to point out at once the apparatus of the Brothers Wright is not self-starting : there is no wheeled carriage to give it the impetus to rise. Launching is artificial, and requires an extraneous force. The skates constitute the part of the apparatus which is brought into contact with the earth in landing. Further- more, they are curved, like those of sleighs which travel over ice. The skids form also the " foundation " of the aeroplane. At the front they carry the elevator, and at the stern the rudder. The Brothers Wright have adopted an elevator very similar to that laid out by Colonel Kenard, which he used for the first time onZa France in 1885. They have set it in such a manner that its concavity may be varied as desired by the pilot in synchrony with the movements which he may have to give to the aero- Frame. Wing D n .- Elevating plane Propellers; Hotor , lev j/ EJ plane. Aviators skaii:es \ SOB* (Front elevation^) rudder. Supporting surface. ^ rf ^} Screw Steering rudder. Screw. n plan X. ievaco. . " " * ~ - - -Tapered tody Ailerons /brnung tKa. levaKnJ rudder. * "Steering rudder FIG. 75B. Bleriot's improved monoplane than 35 kilogrammes, can absorb a blow of several hundred kilogrammes on landing. Fig. 75 shows the side elevation of the tapered carriage with the wheeled frame under the front, and also the rear wheel. Having given the general outlines of this remarkable aero- plane, known as BUriot IX., let us conclude by saying that the MONOPLANES 173 total length from end to end is 12 metres. Its complete spread is 9 metres; carrying surface 26 square metres; weight, including aviator and supplies of fuel, 480 kilo- grammes; and its initial speed 70 kilometres per hour. BUriot XI., such as was used in the Calais-Dover flight, is of more recent design. It is a monoplane in which the ailerons of the carrying surfaces are abandoned in favour of simple warping. The ailerons are retained at the two extremities of the rear stabilisator, and form the elevator. The dimensions of this new aeroplane are much less than its predeces- sors, being over all, length, 8 metres; spread, 7'20 metres; carrying surface, re- duced to 12 square metres; angle of at- tack^ degrees ; wooden screw propeller; motor, 7-cylinder, 30 horse- power, Esnault-Pelterie (K.E.P.). Under these FlG ' 75a Map of B14riot ' s Channel flight conditions the supporting surface sustains an effort of 27 kilogrammes per square metre, but such is the perfection of construction that this end is successfully achieved. The speed of the apparatus is 80 kilometres per hour. The BUriot model 0/1910 differs from BUriot XI. in that it is shorter (6 '50 metres), and that the tapered body is covered throughout with fabric. The tail-balancer resembles a dis- tended swallow's tail, and is connected to the axis of the elevator, which consists of two large segments. The rudder is also of greater surface. 88898 174 THE CONQUEST OF THE AIR THE ESNAULT-PELTERIE AEROPLANE There is a tendency among monoplane designers to decrease the superficies of carrying surfaces to avoid increase of resistance. This tendency is manifested in one of the most remarkable aeroplanes among those which have yet been built, that of M. Robert Esnault-Pelterie, which its inventor, borrow- ing the three initials of his name, describes under the abbreviation "R.E.P." This machine was one of the first to be constructed in France. Among the already important group of French aviators, M. Esnault-Pelterie occupies quite a distinct position. Though very young he set out on the " path through the air " as far back as 1903, for rumours of the exploits of the Brothers Wright, mysteriously held in secret, roused ambitions which became resolved into persevering, continued, and rational experiments, and led him to success. The young aviator (who at that time, however, felt himself to be one of the veterans in the art) did not seek anything from anybody. Unaided, he conceived, constructed, and tested his aeroplane. Moreover, being a practical mechanician, he evolved and made every part of a new type of explosion motor. It was novel because of its compactness, exceptional lightness, and at the same time reliability of action. So in the aviating apparatus that he fashioned and brought to success everything bears the imprint of his personality the general lines, construction, motor, and even the arrangement of the wheeled launching carriage. The Esnault-Pelterie aeroplane is a monoplane, dis- tinguished by its flexible warping wings, and stern carrying surface fulfilling the function of the elevator. It is fitted with a stabilisating empennage, and its carriage is mounted upon two wheels "in tandem," while the tip of each wing carries a wheel for contact with the ground. The shape of the body of the aeroplane is fusiform. It is built up of steel tubes (bicycle tubes), autogenously welded together. Moreover, they form a triangular network similar to a latticed girder, which assures complete indeformability as well as rigidity and strength of the system. I i s h-. M h ?! 2 *s > ^ I g 5 * > c ^ i. a ^ w a ^ I 3 MONOPLANES 175 The wings have a total spread of 9*60 metres, and their design is in accordance with the results of lengthy ex- periments carried out by the inventor. Their surface is 15-75 square metres. As they support the whole weight of the apparatus, which aggregates 420 kilogrammes, this represents a proportion of 2 6 '6 kilogrammes per square metre, the same, be it noted, as in the new monoplane, BUriot XI. The wings are of wood, flexible, strong, and light. They are made in slips, strengthened lengthwise by steel and aluminium. The fabric is stretched over these wings, this being the surface offered to the resistant action of the air. Each wing is stretched underneath by two sets of ropes converging to a point beneath the carriage, and by which warping is accom- plished. Each of these sets of ropes supports one-fourth of the weight of the apparatus. When viewed from above the Esnault-Pelterie aeroplane strikingly resembles a bird with its fan-shaped tail formed by the spreading of its feathers. The surface thus shown (Fig. 76) has a variable inclination at its rear end, thereby forming the elevator, under which is placed the well-balanced rudder, turning about its vertical axis. The latter, to recall marine practice, is what is called a " compensated " rudder, because the axis of rotation passes through its centre instead of at one or other of its sides. Under the body is a " keel," which secures longitudinal stability. The pilot has his seat towards the front of the body of the aeroplane, while the screw is at the extreme prow ; therefore it "draws " the machine through the air. The pilot, owing to the tapering of the stern, has a clear view of the ground in front as he drives the aeroplane along preparatory to launching. The steering and manoeuvring control are by means of levers and pedals. The manipulation of an aeroplane com- prises two operations essentially different, corresponding to two requirements widely divergent. There is first assurance of stability at starting, and afterwards the maintenance of forward direction. For each of these two manoeuvring operations M. Esnault-Pelterie has provided a vertical lever. Stability itself also comprises two variants ; longitudinal and lateral stability respectively. The lever which controls the 176 THE CONQUEST OF THE AIR balance has two movements, one to and fro, the other from }aft to right. For this purpose it is fitted with a universal joint, and is set to the left of the aviator. When he Screw Screw. Steering rudder. FlG. 76. The Esnault-Pelterie monoplane moves it from left to right, or inversely, it warps the wings through the four sets of under-stretched ropes; when he moves it from front to back, or vice versa, it actuates the elevator, and as a result enables the aviator to recover his longitudinal balance, or, if he so desires, to ascend or to descend. The second lever is placed in front of the pilot ; controlling lateral direction, it is moved transversely, and commands the MONOPLANES 177 rudder. One can see the ingenuity and extreme simplicity in the design of these steering devices ; the aviator must push the levers in the direction in which he wishes his aeroplane to go ; therefore, the movements which he has to carry out to this end are, so to speak, reflexive, and error is impossible. Finally, two pedals allow the aviator to control his motor, one acting upon the gas inlet, the other upon the propeller clutch. So far as the motor is concerned, we have already had occasion to describe it. The Esnault-Pelterie (R.E.P.) engine is one of the most original and one of the best-conceived motors in aviation practice. When it was first completed it received the prize of La Societe des Ingenieurs Civils. It is of 3035 horse- power, and its cylinders, numbering five, seven or ten, according to the power, are disposed in two " semi-stars," but in such a manner as to be all above the horizontal diameter of the figure. In this manner lubrication is perfect. The valves are of the sliding type, and, according to their position, permit admission and exhaust ; there is one to each cylinder, and all are operated by a common cam. There is no water-circulation, the cylinders being fitted with fins, and at a speed of 45 kilometres per hour cooling is very perfect. The 30-35 horse-power motor weighs 68 kilogrammes complete. An oil reservoir of 6 litres and a fuel tank of 40 litres suffice for two hours' continuous flight under +,he propulsion of a four-bladed screw 2 metres in diameter, mounted direct on the motor shaft. In completing our description of this remarkable aeroplane, it is only necessary to say a word about the wheeled carriage used in launching and landing. The body of the apparatus is carried upon a pair of wheels arranged in " tandem." Under these circumstances it tilts to the left or right ; but the tip of each wing being fitted with a special wheel, permits the appa- ratus to run along the ground without bringing the wings into contact with the latter. Immediately the apparatus is launched, the aviator, by the aid of the warping lever, lifts the wing which is trailing, and the equilibrium of the machine is estab- lished. The front carrying-wheel is mounted upon an " oil- pneumatic brake," assisted by a spiral spring. Under ordinary circumstances the weight of the apparatus is supported flexibly 178 THE CONQUEST OF THE AIR upon this spring. Vibrations caused by the unevenness of the ground are absorbed by an air cylinder, in which moves an air- compression piston. Finally, the shock in landing is taken up by an oil brake, in which this liquid, compressed by the blow, is forced through a very small orifice : this brake, which weighs only 6 kilogrammes, can absorb 350 kilogrammes. One can see, therefore, that it is very efficient for the landing of the aeroplane. THE " ANTOINETTE " AEROPLANE Among the aeroplanes of the monoplane type, the Antoinette deserves particular mention. Every one knows that the motors of this type have furnished aviation already with an engine in which power combined with lightness has been carried to such a degree that a 1 horse-power motor can be carried by an average man. The builders of these engines have undertaken also the construction of aeroplanes, and in their choice they decided upon the monoplane. They began by building the Gastanibide-Mengin aeroplane, which served as a means of investigation and research. By improvement upon improvement, they at last produced a striking type, which is known as Antoinette V. These constructors, like so many other aviators of to-day, preferred the monoplane because of its extreme simplicity, facility of construction, and greater efficiency, requiring less power for progression through the air under the same conditions of weight and speed. One of the most remarkable features of the Antoinette aero- planes is the design and build of the carrying surfaces. These, divided into two elements constituting wings in the fullest sense of the word, are of trapezium form, the larger base being contiguous to the body of the machine. When seen from the front the apparatus has the appearance of a very open V. The section of these wings is of such form as to secure the maximum of " power of penetration." Their surfaces are covered on both sides, and the fabric is mounted upon a frame- work which is certainly a marvellous piece of work from the triple standpoint of rigidity, solidity, and lightness. This framework is composed of an assemblage of longitudinal and transversal MONOPLANES 179 ribs, intersecting one another so as to form a series of triangles, the whole being consolidated in a rigid manner by riveted aluminium "gussets." The wing surface is 25 square metres, and yet their combined weight is scarcely 30 kilogrammes. Thus, one can see that the total carrying surface is 50 square metres. The extreme spread is 12*80 metres. It is very interesting to note that the builders have designed their framing upon the lines and principle followed by the constructors of metallic bridges and the Eiffel Tower, which consists of subjecting every p&rt to tension and compression. The body is triangular in section ; it is a long girder, ending at the front in a pyramid, prismatic at the wings, and then tapering towards the tail of the apparatus. It is built upon the principle of metal bridges, but at the same time it is light and rigid. Body and wings are covered with fabric, carefully stretched and freely varnished. This imparts to the surfaces moving through the air a remarkable smoothness, reducing the friction of the molecules of air coming into contact with the force which displaces them to the minimum. The constructors of the Antoinette aeroplane have abandoned warping the wings for the following reason. With Louis Bleriot, they have adopted ailerons fitted to the tips of the carrying surfaces, though in a slightly different form. These ailerons are connected to the extremity of the wings, and when at rest form a prolongation thereof. They are connected with the latter by an articulated system which lowers one while it raises the other. This produces the same effect as warping, but with greater power and without the inconvenient danger of fatiguing the wing framework by twisting or bending a part of its construction. These ailerons assure the utmost lateral stability. Longitudinal stability is obtained by an " empennage." It extends horizontally and vertically beyond the surfaces of the empennage properly so called, and carries two rudders for elevating and steering respectively. The great length of the apparatus, which is 11-50 metres, gives a very high efficiency to this empennage, securing a remarkable stability in the direction of travel. Control is effected by three wheels. One cannot refrain Propeller 180 THE CONQUEST OF THE AIR from thinking that such is too much for an aviator who has only two hands ! Two wheels, controlling steering and the ailerons respectively, are close together, it is true, so that the hand can pass easily from one to the other. For my part, I think it would be wiser, perhaps, to have recourse to a con- trol arrangement of the B16riot aeroplane type. That is the only criticism which I can offer of this apparatus, the conception and the construction of which are remarkable from all points. In addi- tion, two handles control the ignition and the inlet throttle of the motor, while there is a foot-brake to stop the engine. The whole apparatus is Horizontal Empennage' Elevating- rudder. Horizontal Empennage ^Steering rudder. Molor Vertical Empennage I Landing skate. 'Radder carried upon a carriage composed of a " wheeled skate " placed under the front of the body, two " shores," one at the right and the other at the left centre of each wing, and FIG. 77. The Antoinette monoplane a " butt-end " under the tail. The " shores" and "butt-end" are on the longitudinal axis of the machine. The " roller-skate," comprising a bicycle wheel at the back and a roller at the front, admits of absorbing to the maximum the severe shocks which are produced at the moment of landing, owing to an ingenious and solid suspension spiral spring. The skate-wheel, almost under the centre of gravity of the apparatus, is so placed that the strain upon the tail is reduced to the minimum. Not only do the " shores " preserve the wings from all rough contact with the ground, but they serve as an anchor- ing point for the upper consolidating rope work. Moreover, a MONOPLANES 181 vertical piece serves as a straining support for the cords stretched over the upper face of the supporting surface. When it is desired to launch the apparatus, the motor is started and the propeller is coupled in. The aeroplane is sup- ported on the ground by its skate, shore, and stern butt-end. As the motor speed increases the butt-end first leaves the ground ; a little lateral oscillation and the shores rise in their turn. Then the apparatus, poised upon its roller-skate, steadily balances itself, until at last the engine power has developed sufficiently to enable it to rise. The motor is, naturally, an "Antoinette." It has eight cylinders disposed in a V, and develops 5 5 horse-power. It is placed towards the front, and drives a two-bladed propeller of 2*20 metres diameter. This screw is of metal; its shaft is a steel tube with blades of aluminium. Its pitch is 1*30 metres, and it runs at 1100 revolutions per minute. The set of the two blades, and consequently the pitch, is variable. Exceptional precautions have been observed to secure ample accommodation for the aviator. His position is well sprung, so as to preserve him as far as possible from all shocks, and at the same time allow him the greatest freedom in movement. Such is this superb monoplane, the construction of which is perfect from all points of view. Its simplicity of control is striking. One of the first models was taken to the Chalons camp, and there placed in the hands of M. Demanest, who served his apprenticeship as pilot. After five lessons only, the young aviator was able not only to "fly," but to win, on April 8, 1909, the prize of the Aero Club of France for 250 metres. M. Henry Farman, passing through the camp at Chalons, officially timed the trip, and warmly congratulated the new aerial navigator. And on June 5, 1909, the Antoinette aeroplane accomplished another performance. M. Latham, scarcely familiar with the management of this remarkable aeroplane, flew for one hour seven minutes, when darkness stopped him. Not content with having beaten the world's record in a monoplane, he set out on the following day with a passenger. The third day he per- formed an unprecedented achievement in aerial flight, by carrying two passengers, MM. Fournier and Santos-Dumont, 182 THE CONQUEST OF THE AIR and demonstrated once and for all by his marvellous skill the safety and facility of manipulation, and consequently the absolute superiority, of the French aero- monoplanes. Since then this aviator has carried off innumerable trophies. This feat, so rapid, this safety, so promptly acquired, demon- strates better than words the great security of the French aeroplanes, and how much easier they are to control than apparatuses which demand everything of the aviator. And this rapid initiation is not an isolated instance. Flying can be learned in a few lessons upon the BUriot, Esnault-Pelterie, Voisin, Farman, Tellier, and Antoinette aeroplanes. This exemption from a long, laborious, and perilous apprenticeship is quite a triumph for French aviation. M. SANTOS-DUMONT'S " DEMOISELLE " : THE TELLIER AEROPLANE Smaller still is the latest aeroplane designed by M. Santos- Dumont, the Demoiselle, as it has been christened by its author. It is 6 metres long, 5 metres spread only, and 150 kilo- grammes in total weight. Such is the remarkable machine on which the Brazilian aviator completed several successive flights at St. Cyr, early in April 1909. And during Sep- tember 1909, the intrepid Brazilian accomplished the extra- ordinary feat of covering 8 kilometres in 5 minutes. Power is furnished from a Darracq motor, and the aviator is suspended beneath the engine in a sling, operating one of the controlling devices by the movements of his shoulders. With this machine Santos-Dumont beat the record in " tearing away " from the earth by rising into the air after a launching run along the ground of only 6 5 metres. He carried out diverting flights by setting out from St. Cyr to visit the Count and Countess Galard, at their country seat, Wideville, 17 kilo- metres from Versailles: Thus is demonstrated the fact that one can fly without the use of immense surfaces, of weighty and cumbersome machines. Before long, thanks to the explosion motor, the artificial bird of less weight and bulk will be able to go anywhere. A little more progress and every one will fly. A few words must be said likewise about an entirely new MONOPLANES 183 monoplane emanating from the ateliers of the Brothers Tellier. This machine possesses some truly remarkable features. In its broad lines the apparatus recalls the BUriot mono- plane which flew across the Channel. But it differs therefrom in essential details. First and foremost the wings are articu- lated. The designer has reverted to the system of warping the wings in his first model ; but undoubtedly he will improve this otherwise successful model, by substituting the simpler and more reliable ailerons for the wing-warping arrangement. The rudder at the stern is wholly above the empennage tail and elevator. Furthermore, longitudinal stability and opposition to lateral drift are secured by means of a rigid vertical " element." The weight of the Tellier aeroplane, ready for the air, is 500 kilogrammes, which includes sufficient fuel for six hours' flight. The two-bladed propeller, also a creation of the Tellier shops, is made of wood ; the Panhard-Levassor 3 5 horse- power motor runs at 1000 revolutions per minute; and the whole mechanism is controlled by a single wheel. The apparatus is carried upon a latticed wheeled carriage. The front part of the body is covered with fabric. It is scarcely necessary to say that, in common with all French monoplanes, longitudinal stability is assured automatically by means of the empennage tail. The wing spread is 11 metres, length of machine 11 metres, and the superficies is 24 square metres. Seen from the front the machine has the form of a very widely opened V. Such is this simple and striking aeroplane, the control of which is so simple that M. Emile Dubonnet secured his aviator-pilot's certificate in a single flight with turns without detaining the governing committee more than half an hour at the aerodrome, after but four trips on the machine ! In the first flight succeeding the granting of this certificate M. Emile Dubonnet accomplished a master-stroke. The scientific journal La Nature offered a prize of 400 to the first aviator who made a cross-country journey of 100 kilometres (such conditions would have to be fulfilled to render aviation practical) within two hours or less. Emile Dubonnet won this prize easily upon his Tellier monoplane on April 3, 1910. 184 THE CONQUEST OF THE AIR Thereby he secured the record for a mechanical flight across country, of which, however, he was deprived four weeks later by Paulhan's magnificent flight from London to Manchester. THE TWO SCHOOLS OF AVIATION We see from the foregoing that we are confronted by two schools of aviating apparatus : the American school, repre- sented by the Brothers Wright, which demands everything of the aviator, and the French school, Voisin, Farman, Bleriot, Esnault-Pelterie, Antoinette, which requires, on the other hand, the minimum from the pilot. Which of the two is correct ? The best way to reply to this question is to quote the words of Paul Painlev6, Sorbonne Professor, and member of the Acad6mie des Sciences. M. Painlev6 is not an abstract mathe- matician who confines himself to differential symbols or the study of elliptic action. He has probed into aviation practice, has flown in turn with Wright at Auvours, and with Farman at the Chalons camp, and this is how, in a subsequent article, he expressed himself upon the subject : " Aviation is the most burning mechanical problem appeal- ing to mankind to-day. Its solution is achieved. To-morrow it will be commercial ; in a few years it will commence to trans- form the world. Now this solution can be indicated upon broad lines. " We have two schools, the French and the American, or if one so prefers for it is confined to the two constructors who have effected the most impressive results the Voisin and the Wright systems respectively. 1 "In the first place an aeroplane must travel quickly to be able to support itself in the air ; the speed must be such that the resistance of the air, increasing with the speed, prevents it from falling, whence the necessity of a motor, powerful, light, and regular in action. The more swiftly an aeroplane can travel the more stable and capable will be the apparatus for i At the time the eminent mathematician wrote these words (Le Matin, October 28, 1908) M. Bleriot had rot made his "historical journey" in a dosed circle or his flight across the Channel, and Latham had not accomplished his well-known brilliant triumphs on his Antoinette monoplane. MONOPLANES 185 combating the caprices of the wind. The perfection of an ideal motor is no more than a question of months. "Then it is imperative (and this is the gravest difficulty) that the apparatus should neither dip forwards nor backwards, neither to the right nor left; it must not even deviate from its direction of travel. In a word, the 4 aeroplane must not pitch or roll, or swing round suddenly, or else the pilot must be able to restore such unbalancing movements as soon as they develop. " Here are the means of obtaining this stability, which are different in the two schools. " Wright has sought simplicity and lightness above every- thing, but the equilibrium of his apparatus is entirely in the hands of the pilot. Three distinct movements combat the three possible perturbations ; warping of the wings counteracts rolling particularly. " On the contrary, the Voisin Brothers secure lateral stabi- lity by partitioning the two wings like the cells of a kite in the form of a cigar-box. Their apparatus adapts itself to the most convenient inclination in turning. Two operations instead of three are all that is necessary to control their machine of the rudder and elevator respectively. Even this last control is now simplified greatly by the addition of a long tail, which opposes pitching. "Lastly, the utilisation of motive power either by large slowly-turning screws as in the Wright machine, or the smaller and higher speed of the propeller of the Voisin system, appear comparable. " The Voisin apparatus is decidedly heavier than the Wright (650 instead of about 500 kilogrammes), due in the first instance to the tail, and secondly to the wheeled carriage (80 to 100 kilogrammes) necessary to enable the apparatus to lift itself under its own effort. " These differences, well specified here, are the results obtained by the two apparatuses. Wright holds the record for distance unaccompanied and with a passenger, 1 yet he has never raised himself ly his own effort. He will be able to do so though when he so desires, but will it be without increasing weight ? " " The Voisin apparatus, piloted by Farman, holds the record i These lines were written during October 1908. 186 THE CONQUEST OF THE AIR for speed 70 kilometres per hour at least. But it must be pointed out that it is always self-lifting by means of its wheeled carriage, weighing 80 kilogrammes. " I saw Farman fly in a violent wind (October 28, 1908) over the camp at Chalons ; he made the first long-distance flight in an aeroplane; he flew not only in public, but before some officers who attempted to overtake him at the gallop. He repeatedly described his usual circuit at great altitude, frequently exceeding 40 metres. Lastly, notwithstanding the weight of his wheeled carriage, it lifted itself and me ~by its own effort, traversed a distance of 1600 metres, and completed a turn, the apparatus showing as perfect a stability as if the pilot were unaccompanied. " ' A magnificent day's work for French genius ! ' wrote a young officer who was overcome by enthusiasm at these experiments." It would be useless to add a line of comment to this criticism from one of our most learned mathematicians, a criticism enunciated on October 28, 1908. Two days later Farman and Bleriot substantiated his statements by completing, on the 30th and 31st of the same month, the two " first aerial voyages " from town to town. That is a distinction of which none can ever attempt to deprive them; they were the two first " tourists of the air." It is possible by means of so exact a comparison to grasp intimately the fundamental difference between these two " schools " of aviation. We see that the American school demands everything of the aviator, longitudinal, as well as lateral, stability, whilst the French school assures the longitudinal stability by means of an empennage and a long leverage arm, which is an important point. The two schools may best be likened to those two machines, the monocycle and the bicycle respectively. Neither has lateral equilibrium, and the rider must secure it in the same manner upon both. But whereas he must also obtain longitudinal stability upon the monocycle, on the other hand, with the bicycle this is inherent, owing to the two points of support on the ground. Consequently, while any one can manage a bicycle, only those expert in balancing will risk themselves upon a monocycle. MONOPLANES 187 The French aeroplanes BUriot, Voisin, Farman, Antoinette are the bicycles of the air. Every one will be able to use them. The exploits of Latham at the Chalons camp, where, after only a few lessons, he was able to remain in the air on his Antoinette aeroplane for sixty-seven minutes, and to lift two passengers; of Farman, who flew for over an hour with two passengers ; of Sonmier, who made the first trip with " four up " ; and of Paulhan, who sped across England, &c., demonstrate the facility and safety of their management. On the other hand, one knows the long practice, the skill that is requisite to use a Wright. Wilbur Wright possesses this skill to an extreme degree, but its acquisition is not open to all and sundry, no more than the balancing of a monocycle. HELICOPTERS AND ORNITHOPTERS : THE BREGUET GYROPLANE A word remains to be said about aviation apparatuses based upon principles other than those of the aeroplane. There are, first of all, the helicopters, or apparatus with sustaining screws. So far these apparatuses have not given decisive results. True a fairly heavy apparatus succeeded in rising from the ground on several occasions, even with the aviator ; but what is difficult, and what is so far only promise, is the steady advance of the apparatus through the air. Hitherto the efforts of investigators have been confined almost exclusively to sustentation by screws. We have mentioned Colonel Renard's works upon this subject, and the hopes inspired by rather hasty interpretations of the formulae which summed up his calculations. A few trials of direct sustentation by screws have been carried out recently, the most important being those of Engineer Leger (Monaco), M. Paul Cornu, and M. Louis Breguet. We have already spoken (p. 146) of the first of these apparatuses. Let us now say a few words about the two others, which have furnished interesting results. We know what " screw-slip " is the propeller revolves in the air like a screw, but the mobility of the molecules of the latter causes the apparatus to advance only a fraction of its " pitch." The difference defines the slip. Until recently attempts were made to reduce the slip 188 THE CONQUEST OF THE AIR as much as possible by decreasing the pitch of the screw for sustaining propellers used with helicopters. This slip, how- ever, cannot be entirely overcome. Therefore M. Cornu sought to use the slip for the horizontal propulsion of the aviation apparatus. This is the principle of his machine. A frame carries a motor, which transmits its power through endless belts to two screws, one on the right and the other on hand propeller. Llt kaftd propeller. plane propellers. plane propellers. Motor. FlG. 78. The 'principle of the Cornu helicopter The screws secure ascent vertically, and the resistance of the air upon the oblique plane propellers produces lateral displacement the left, and turning in opposite directions to annul torsion efforts. These are the " sustaining " screws devised to lift the apparatus in the air. The effect of their slip produces a downward back-thrust of air, whereas their useful effort secures the sustentation of the apparatus. This backward drive of air is used for horizontal propulsion by means of inclined planes placed under the screws. These oblique surfaces transform the vertical effort of the descending air into a horizontal component which displaces the apparatus in a given direction. By inclining differently two series of these planes placed on both sides of the axis, turning and inclina- tion may be obtained. Such is the principle of the Cornu apparatus. Plate XXXIII. shows the general details of its construction. Results therewith have been encouraging. Once the apparatus rose with its aviator on board ; on a second occasion it ascended with two men, the total weight lifted being 328 kilos. It remained in the air for one minute. Propulsion, due to the horizontal effort exercised upon the MONOPLANES 189 oblique planes, was weak only 12 kilometres an hour. It may be seen from the foregoing that this helicopter is amongst the most interesting of its type, and such experiments must be encouraged, as, without a doubt, it is from this line of development that the perfect sustaining screw will be evolved. Perhaps it will be possible to associate such with the aeroplane some day. Special mention must be made of a very interesting aviation apparatus the gyroplane of Messrs. Breguet and Bichet. This fulfils the combination of the aeroplane and the helicopter in a happy manner, since it comprises an association of faced, with revolving, wings. The photograph enables their arrangement and operation to be understood very clearly. The total surface of the revolving wings is 11 square metres each. The surface of the fixed wings is 50 square metres, which, in the event of a vertical descent, provides a total area of approximately 72 square metres to form a parachute. The oblique disposition of the screw shafts may be observed as soon as the propellers are in motion. The reaction of the air upon the fixed surfaces gives a double effort an upholding vertical effort, and a horizontal effort serving for forward propulsion. With aviator and petrol sufficient for one hour, the apparatus weighs 600 kilos ; the " Antoinette " motor develops 40 horse-power. A balancer which can be warped, placed at the bow, and lateral small wings, ensure stability, and permit the aviator to regain such in the event of accidental inclination. A rudder at the stern of the apparatus acts as the vertical empennage. The fixed and revolving surfaces are flexible, and constructed upon very ingenious lines. They are covered partly with very thin aluminium sheets, and partly with special waterproof and non-hygrometrical paper. The apparatus has been tested successfully at Douai, on ground purposely selected as unsuitable for the launching oi ordinary aeroplanes a beetroot field. The apparatus rose straight into the air with the greatest facility. An accident interrupted the experiments, but the results are most encouraging, and of a nature to induce the designers of the apparatus to persevere in the path they have selected. 190 THE CONQUEST OF THE AIR The ornithopter has been studied and constructed upon feasible lines by Mr. Adh. de la Hault, a Belgian aviator. Without seeking to "fly " right away, this distinguished constructor first devoted his attention to the study, working, and efficiency of the "flapping" wings. He built a novel apparatus, showing distinctive mechanical ingenuity, which describes a movement in the form of the figure 8, according to the curve which mathematicians call " lemniseate." By means of this complex action, the author hopes to realise the dual propelling and sustaining function of a bird's wings. Mr. de la Hault's apparatus figured in the 1908 Brussels Exhibition, and the remarkable mechanical features were much admired by engineers. The inventor is now pursuing his researches, and undoubtedly important results will be obtained. There remains but to indicate an American ornithopter with flapping wings, provided with Venetian blind blades, which close in descent and open in ascent. We have no data regarding the practical results achieved by this apparatus. In concluding this history of the principal aviation apparatuses as designed up to now, we may say confidently that the aeroplane alone, so far, has furnished really practical results, and has shown in its various forms absolute superiority over the two other aviation systems. This justifies the enthusiasm it has provoked and which its continuous develop- ment is maintaining. What is necessary is to ascertain how either supporting screws or propelling surfaces can be added thereto. With the aeroplane in its present promising form, it is obvious that aviation, the " heavier than air " science, is far from having said its final word; it has barely said its first. CHAPTER VI EARLY DAYS OF AVIATION FORERUNNEKS AND PIONEERS : THE STRUGGLES, TRIUMPHS, AND THE VICTORS I THE MARTYRS THE FORERUNNER : SIR GEORGE CAYLEY Now, knowing the conditions an aviation apparatus must fulfil ; realising the difficulties that are encountered in seeking to evolve, raise, and control it ; glancing back to see how the traveller has arrived profitably at the end of his journey; and instructed in its handling, we shall be better able to appreciate the immense effort put forth by those who were the creators of " heavier than air " aerial locomotion. Let us at once reassure the reader that we will not hark back to Icarus or legendary history. We will take aviation only from its modern origin ; start from the time when methodical ideas were calculated sufficiently to enable in- vestigators to proceed on serious and practical lines, instead of aimlessly groping about in the dark. The first serious investigations relative to aviation date only from the commencement of the nineteenth century, and it was the aeroplane which arrested attention. By a curious coincidence, even as the first projected airship, that of General Meusnier, was " complete," and anticipated all the necessary equipment, so was the first aeroplane conceived " complete " and everything essential therefor indicated by its author. This inventor, the incontestable forerunner of aviation, was an Englishman, Sir George Cayley, and it was in 1809 that he described his project in detail in Nicholson's Journal. In the course of an excellent paper presented to the Societe des Ingenieurs Civils, M. Soreau recalled this date, when he remarked how sad it was to think that such a valuable 191 192 THE CONQUEST OF THE AIR invention as this had not been possible of application im- mediately upon its conception. Sir George Cayley's idea embodied " everything " the wings forming an oblique sail, the empennage, the spindle forms to dimmish resist- ance, the screw-propeller, the " explosion " motor, the calculation of the centre of thrust, and demonstration of the Compressed air reservoir Screw FIG. 79. Victor Tatin's aeroplane model driven by compressed air made a flight at Meudon in 1879 fact that displacement takes place towards the front. The author even described a means of securing automatic stability ! Is not all that marvellous, and does it not constitute a complete specification for everything in aviation ? Thus it is necessary to inscribe the name of Sir George Cayley, in letters of gold, on the first page of the aeroplane's history. Besides, the learned Englishman did not confine himself to " drawing-paper " : he built the first apparatus (without a motor) which gave him results highly promising. Then he built a second machine, this time with a motor, but unfortunately during the trials it was smashed to pieces. In 1842 another Englishman, Henson, attempted to build a model aeroplane upon this principle, but without success. One must pass on to the year 1856 to find the first experiment with apparatuses tnat " rose into the air " with a passenger aboard. It was nothing more than sustentation from a huge EARLY DAYS OF AVIATION 193 kite, hauled by a vehicle. This initial tentative effort was carried out by Le Bris, a French sailor. The first attempt to glide aerially by a " soaring plane " was made with what was really a triplane by Wenham in 1866. Such an apparatus was used thirty years later in the experiments of Chanute, Wright and Archdeacon. Nor must it be forgotten that towards 1860 Nadar, Ponton d'Amecourt and de la Handelle carried out their "heavier than air" campaign, and that in 1862 the first steam helicopter was built by Ponton d'Amecourt, a model, it is true, but a working model, which is preserved in the archives of the French Aerial Navigation Society. A small model of another helicopter, built by Enrico, which was driven by a small steam engine, and weighed 3 kilogrammes all told, lifted itself from the ground and remained in perfect equilibrium without any material contact with the earth in 1878. The three first aeroplanes or models of aeroplanes which truly " soared " were the small apparatuses of A. Penaud which followed the lines of a monoplane with an empennage tail (Fig. 43), and Victor Tatin's aeroplane constructed and tested at Chalais-Meudon in 1879. The latter was driven by com- pressed air and its trials were absolutely convincing. Held by a cord secured to the centre of a small circular track, the machine ran round the track, stretched the cord, and rose into the air. Subsequently, in 1896, the celebrated American physicist, Professor Langley, contrived a small steam-driven aeroplane weighing 13 kilogrammes, having two pairs of wings placed, not one above the other, but one in front of the other in " tandem." Although this aeroplane did not lift itself, it accomplished the first aerial journey by covering lj kilometres through the air. A second aeroplane was built some time after (in 1903). It rose into the air, but undoubtedly owing to the controlling aviator's inexperience it fell into the Potomac. Yet investigators continued their experiments, and two names, both well known in industry, are inscribed in the golden book of aviation. One is that of Sir Hiram Maxim, the famous inventor of quick-firing guns, who up to 1890 had expended over 40,000 in the construction of a very large 194 THE CONQUEST OF THE AIR steam-driven aeroplane. This apparatus, notwithstanding the great achievement of its inventor in regard to the lightness of the steam engine (15 kilogrammes per horse-power), only dis- played a "tendency to lift itself" ; it never actually rose. The other industrial magnate was M. Clement Ader, famous for his great developments in the construction of telephonic apparatus. In 1890 and 1896 he built two aeroplanes which he christened Avion. On both occasions the apparatuses lifted themselves from the ground, and in 1896 at Satory the apparatus completed a flight of 300 metres after leaving the ground under its own effort, before officers delegated by the Minister of War. If, therefore, the honour of having conceived the first aeroplane rests with an Englishman, the merit of having constructed the first apparatus that effectively flew, is due to a Frenchman a glorious example of the entente cordiale associated with the history of human progress. THE " HUMAN BIRDS " : LILIENTHAL, CHANUTE, CAPTAIN FERBER, THE BROTHERS WRIGHT Whilst some engineers were seeking " to break in " machines to sustain in the air, other investigators were compelled to seize the mechanism of the "soaring plane," and upon these motor- less gliders, utilising only their weight and the resistance of the air, served their " bird-apprenticeship." Foremost among these persevering and daring men, must be placed the rightly re- nowned name of the German, Otto Lilienthal, who long before the Brothers Wright (they merely followed in his footsteps in their earliest attempts), accomplished some remarkable experi- ments in this direction, in the course of which he lost his life in his devotion to aviation science. Lilienthal, a Berlin engineer, built veritable birds'-wings, by means of which, when fixed to his body, he sought to achieve the "soaring flight" of birds of which we spoke in a previous chapter. These wings, of which the photograph (Plate XXV.) gives a very good idea, were formed of an osier framework, covered with light, stretched fabric. Two horizontal rudders, forming a bifurcated bird's tail, were at the rear, surmounted by a large steering rudder of rounded form. Lilienthal, well poised in the centre of this framework, jumped from the top of EARLY DAYS OF AVIATION 195 a low tower, against the wind. The inclination of his body and legs enabled him to shift the centre of gravity of the whole system. In this manner he carried out some remarkable flights, some of which attained 300 metres in a horizontal direction. After he had made about a thousand such Lilienthal changed the form of his " flier." Abandoning the monoplane he built a biplane, and broke his neck in a fatal fall from a height of 80 metres in 1896. The experiments of the unfortunate German engineer were of incontestable value in demonstrating the efficiency of carrying surfaces and the possibility of realising equilibrium under the best conditions daring flight. The Americans followed in his footsteps, and among the first of those who, in the United States, sought for the solution of the problem by the study of the soaring plane must be mentioned a Frenchman, long resident in New York, M. Octave Chanute, born in Paris in 1831 of French parents. Chanute, although well advanced in age, continued the experiments of Lilienthal. He emphasised the biplane and happily first conceived the disposition of the balancers. In 1899 Ferber, captain of artillery, commenced in France a series of very beautiful experimental researches first in glides, afterwards in the conditions of equilibrium. He even tried an aeroplane fitted with a "manoeuvring" motor, describing a circular movement about a fixed point to which he was mechanically connected. His work and writings place him prominently among those to whom we owe so much, and it is inspiring to see a French officer occupy a distinguished position in the ranks of these " forerunners " who planned out the path so well. So, when, in 1900, the brothers Orville and Wilbur Wright, bicycle makers of Dayton, set out to tackle the problem they found the ground well prepared. Lilienthal had shown the way, Chanute had indicated the arrangements, and the Brothers Wright perfected them. They "strove for the point" with great judgment, skill, and, above all, an extraordinary deter- mination to become "human birds." They commenced by carrying out numerous aerial glides with their biplane so as to secure aerial equilibrium. These glides suggested many happy 196 THE CONQUEST OF THE AIR modifications to them, and encouraged by the doyen of aviators, Octave Chanute, in 1903 they] built their first motor-driven aeroplane, with which they performed several flights in a straight line. It was not until 1904 that they effected their first turn. Then they embarked upon long flights of many kilometres at an average speed of from 6 to 65 kilometres per hour. Their experiments were so wrapped in mystery that many would not believe them. Among the few persons in France who really credited the performances of these two transatlantic aviators, were Captain Ferber, M. Rodolphe Soreau, and M. Henri Letellier. In view of the military possibilities of their machine, M. Letellier even sent one of his collaborators, M. Fordyce, to America to negotiate with the two inventors for the cession of their appa- ratus to the French Government. These negotiations were not successful and it was not until the summer of 1908 that Wilbur Wright, at the request of a group of financiers with whom he had been in treaty, went to France. He carried out his first trials at Mans, at the camp of Auvours, upon the Hippodrome des Hunandieres, where he executed numerous flights all under " experimental " conditions, but never once set out under his own effort, and made no actual voyages. Nevertheless it must be remembered that, thanks to his aviating skill, Wilbur Wright completed some flights of very long duration. Among them he succeeded in repeating the exploit of the Frenchman, Delagrange, by carrying as a passenger M. Paul Painleve, of the Academie des Sciences, with whom he remained in the air for over an hour. These experiments, owing to the enormous publicity ex- tended, created an immense sensation. One had forgotten somewhat the French aviators when two of them established remarkable records, and created distinction by making the two first aerial voyages in an apparatus " heavier than the air" on October 30 and 31, 1908. EARLY DAYS OF AVIATION 197 EXPLOITS OF THE FRENCH AVIATORS : SANTOS- DUMONT, VOISIN, DELAGRANGE, &c. : THE 3MLECENE : HENRY DEUTSCH, E. ARCHDEACON, ARMENGAUD The flights of the Brothers Wright were very beautiful demonstration experiments, but nevertheless the aeroplane of the Americans is not perfect. Its stability demands a con- stant effort on the part of the aviator, because of the suppres- sion of the empennage tail, and for this reason the apparatus is dangerous. French aviators worked quietly towards the solution of the problem, and to its complete solution. In other words they sought the perfection of a self-starting aeroplane, able to rise from the ground under its own effort, and after having landed to restart without either rail or pylon. At the end of 1903, the ardours of the audacious French aeronauts were revived. That year Colonel Renard pointed out that, when the weight of the motor was brought below 5 kilogrammes per horse-power, flight by means of " heavier than air " machines was possible. The great authority, the sanguine views of the illustrious and learned officer were more than a hope ; they were a guarantee for the pioneers who set out towards the conquest of the atmosphere. Among the most prominent of distinguished ardent sports- men was Ernest Archdeacon, who, as far back as 1904, made some experimental glides with an aeroplane among the dunes at Berck-sur-Mer. At that time what perseverance was neces- sary to pursue, without faltering, this struggle with the uncon- trollable element ! What faith in the future, not to allow one's self to be turned away by the criticisms and the more or less witty satires of the detractors who are always more numerous than the " actors " ! But the latter were enthusiasts ; nothing would stop them. Voisin built and tested with Archdeacon, Ferber and Santos-Dumont. The last-named sought to forge the " connecting link " between the aeroplane and the kite. He constructed a biplane which could float upon the water, and had it towed along the Seine by the Rapttre, one of the fastest existing motor-boats. The apparatus rose, carrying the 198 THE CONQUEST OF THE AIR aviator, thus excelling the bold efforts of many persevering workers. The possibility of aviation was established now. Experiments in aviation also multiplied. It is necessary it is essential to point out that nothing had transpired concerning the experiments of the Brothers Wright, whose existence was scarcely known. A stronger reason for being ignorant of details concerning their mys- terious machines was that their authors jealously guarded themselves against prying eyes. Moreover, does not the merit of the French aviators stand unique ? Not only have they done as well, but they have done letter. What more can be asked ? M. Santos-Dumont was the first to succeed. The intrepid Brazilian aeronaut carried off the first prize which the generous Msecene of aviation established in 1906. With what is this date to be compared ! In 1906 not a motor-driven or self- starting aeroplane had left the ground. Thus it may be seen that he who could make a flight of 100 metres would achieve indeed an admirable exploit. Santos-Dumont carried off " the prize for 100 metres " at Bagatelle on November 12, 1906 ; some time after Delagrange and L. Bleriot won the prize for 200 metres by a flight of 220 metres. Two gentlemen then appeared on the scene who by their lavish generosity have contributed greatly towards the develop- ment of aerial sport MM. Henry Deutsch and Ernest Arch- deacon. The flights so far accomplished were in a straight line ; the aviators hesitatingly refrained from risking a turn. They saw the difficulties we have already pointed out. MM. Deutsch and Archdeacon offered a prize of 2000 to the first aviator who accomplished a circular kilometre. This prize was won by Henry Farm an, at the Issy-les-Moulineaux manoeuvring grounds, on January 13, 1908. Thereafter the triumphs of this persevering aviator con- tinued without interruption. On July 6, 1908, by remaining in the air for twenty-one minutes, he won the prize so spiritedly offered by the engineer, M. Armengaud, to the aviator who could remain aloft for a quarter of an hour. EARLY DAYS OF AVIATION 199 THE TWO HISTORICAL AVIATION VOYAGES BY FAR- MAN (OCTOBER 30) AND BLERIOT (OCTOBER 31, 1908) WHO ACCOMPLISHED THE TWO FIRST "AERIAL JOURNEYS" FROM TOWN TO TOWN However, all preceding records were completely eclipsed by the two exploits of H. Farman and L. Bleriot. Hitherto aeroplanes had simply described evolutions over race-courses or aerodromes, where the ground, purposely levelled, offered the best facilities for the ascents and descents of the French aeroplanes. These advantageous conditions were not sufficient for the American aeroplanes, because it was necessary for them to have also a pylon and launching rail. Thus the aeroplane had to demonstrate its possibilities of endurance, to show that it possessed really practical utility, and that it did not require special facilities at halting-places in its aerial passage. MM. H. Farman and L. Bleriot had the unquestioned and indisputable distinction of fulfilling this demonstration, which was anticipated by the whole world. They proposed to embark upon an actual journey from town to town and they succeeded. Henry Farman left the precincts of his shed at Bouy, near the Chalons Camp, at 3.50 on October 30, 1908, and set out for Rheims. The wind was E.S.E. The aviator immediately gained a height of about 50 metres, which was necessary, owing to the stretches of tall poplars barring his path. He flew over rivers, villages, woods, &c., and, after being twenty minutes on the journey, reached Rheims, where he landed with the utmost ease in a park between the cavalry barracks and Pommery House. During this twenty minutes he covered 27 kilometres, which gave a " start to stop " speed of 79 kilometres per hour. On the following day (October 31, 1908) Louis Bleriot completed a still more sensational and perfect "journey." Leaving Toury (Eure-et-Noir) at 2.50, he steered towards Artenay (Loiret), a point situated some 14 kilometres from the starting-point. There some captive balloons had been sent up to indicate the point where he was to turn. Flying a dozen metres above the ground, the aeroplane passed over Chateau-Gaillard and Dambrou, and the automobiles 200 THE CONQUEST OF THE AIR which were following him were speedily " scattered " along the roads. Eleven minutes after the start an ignition fault com- FiG. 80. The first " aerial voyage " made in a closed circuit from Toury to Artenay and back, by Louis Bleriot, on October 31, 1908 pelled him to alight. He landed without difficulty, repaired his magneto, and set out again under his own effort, after a descent lasting an hour and a half, to continue his journey. EARLY DAYS OF AVIATION 201 Holding more to the west, he passed Pourpry, and made a second descent of some minutes at Villiers Farm, near Santilly. He re-started a second time, passed Pointville at five o'clock, and returned in quite a matter-of-fact manner to his starting- point, having accomplished the first " cross-country " voyage with descents. During this flight his aeroplane acted mar- vellously well, attaining a velocity of 85 kilometres per hour (Fig. 81). Thus, Louis Bleriot demonstrated that the French aeroplanes mounted on wheels are complete apparatuses, truly self-starting, practical, and capable of resuming their flight when it is inter- rupted. He proved the services that aero-locomotion could render us, and illustrated that aviation from that time hence- forth could enter into everyday practice. Certes, one had been so persuaded, but a good practical demonstration is worth more than exhaustive arguments : contra factum non valet argumentum. Consequently Far man and Bleriot were absolute demonstrators, and definitely opened " the Highway of the Air." It was a fair act of the Academie des Sciences to divide the Osiris prize between Bleriot and Voisin, the creators of these marvellous aviation apparatuses. THE LATEST ACHIEVEMENTS OF THE AVIATORS LATHAM, ROUGIER, COUNT LAMBERT, PAULHAN, DUBONNET, &c. : BLERIOT'S FLIGHT ACROSS THE CHANNEL : PAULHAN'S FLIGHT OVER ENGLAND: THE CROSSING OF THE ALPS BY CHAVEZ In July 1909 a prize was offered for crossing the Channel by aeroplane. Latham, on an Antoinette monoplane, attempted to carry it off. On the first occasion he fell in mid-Channel, and was rescued by a torpedo-boat. By no means discouraged, he made another effort some time later. Leaving the French coast, he again fell into the sea when but little more than a mile (1852 metres) from the English coast. He failed, but his feat proved that the prize could be won. It was secured two days later by Bleriot, who, starting from the outskirts of Calais, alighted on the cliffs of Dover. We gave this French aviator a triumphant welcome, and his return to France assumed the character of a national event. 202 THE CONQUEST OF THE AIR In April 1910 the Daily Mail offered a prize of 10,000 to the aviator who flew from London to Manchester within twenty-four hours, and without making more than two stops during the journey. Mounted on a Henry Farman biplane, fitted with a Gnome motor and Chauviere propeller, the French aviator Paulhan snatched victory from his rival Graham White by covering the distance over 300 kilometres in 4 hours 12 minutes. It is difficult to describe the reception extended to Paulhan upon his return to London. He was received with the strains of the "Marseillaise" and of " God Save the King," while his carriage was hauled along by enthusiastic admirers. This last-named exploit never will be forgotten owing to its exceptional importance. It demonstrated conclusively that aviation was practicable, and that its entry into our daily life was no more than a matter of perfecting details. Consequently Paulhan's " journey " constitutes not only an important date in the annals of aviation, but in the history of civilisation as well. But it is unfair not to mention the magnificent flights of other aviators. In the early days they strove to show that the aeroplane could fly just as high as the dirigible. Altitudes of 300, 400, and 600 metres were attained successively. But the finest records commenced with Latham upon a monoplane and Paulhan upon a biplane. On January 7, 1910 the day of the funeral of Delagrange, a victim to his devotion to aviation Hubert Latham rose into the air as if to take a sweet revenge. He left the ground at the Chalons camp at 2.30 P.M., followed a sweeping circle by Bourg and Mourmelon, described an ascending spiral, thereby gaining a greater and greater height. In thirty-two minutes he had reached an altitude of a little more than 1000 metres ! The feat was authenticated, upon descent, by a report signed by General Journee and Lieutenant Lardet. The kilometre in altitude so coveted was achieved ! But Hubert Latham did not hold the altitude record by aeroplane for very long. On January 12 that is, five days later Louis Paulhan, at Los Angeles (California, U.S.A.), in a flight officially measured, attained the height of 1269 metres. w -4 II It o o ^ r* C ff o S a S a& SB rti ^ 5? I *ll rt ^? b B ? c S a 3 5 o S IS II EARLY DAYS OF AVIATION 203 On July 7, 1910, he reached an altitude of 1384 metres, and on July 30 the Belgian aviator Oliesloegers rose to a height of 1524 metres, which is practically the maximum altitude reached by a dirigible the CUment- Bayard, under the hand of the accomplished pilot Capazza. At Blackpool on August 2, 1910, Chavez, the Peruvian, reached 1800 metres, and at Atlantic City (U.S.A.) in July the American Brookins notched 1880 metres. But the two highest altitudes reached by aeroplane are 2521 metres by Morane, and 2562 metres by Geo. Chavez. The latter aviator had the unique distinction of being the first to cross the Alps by aeroplane, on September 24, 1910, though he paid for his victory with his life. But he demonstrated by his magnificent flight from Brigue to Domodossola that current practice in flying is possible at extreme altitudes, and that the upper atmosphere is not closed to apparatus " heavier than air." Speed and durations also have their champions, and here the name of the American Curtiss stands pre-eminent. At the same Los Angeles meeting where Paulhan set up the altitude record, Glen H. Curtiss, with a passenger aboard, travelled 88 kilometres in an hour on January 11, despite his surcharge in weight ! On April 8, 1910, a young Belgian aviator, Daniel Kinet, mounting a Henry Farman biplane, flew for 2 J hours with a passenger this is the world's record. Transport facilities increase day by day. It is scarcely three years ago since Delagrange, while in Italy, for the first time took a passenger with him. Later, at Auvours, Wilbur Wright repeated this feat. Then on August 28, 1909, Henry Farman, after making several flights with a passenger, flew for ten minutes with two passengers aboard ; and finally, on March 25, 1910, he remained in the air with two passengers (three persons in all) for sixty- two minutes. But at Mouzon, in the Ardennes, on April 20, going one better, Roger Sommer,upon his ordinary biplane, and without making any special modifications, ascended and remained aloft for five minutes with three passengers (four people in all) Mile. Dutrieu (weighing 45 kilos.), M. Colombo (60 kilos.), and Frey (58 kilos.). Let us add that Sommer himself weighs 60 kilos., and that he carried 20 kilos, of petrol. This represents, therefore, a total 204 THE CONQUEST OF THE AIR weight of 243 kilos, which was lifted into the air. This performance was of capital value, for it gave an idea of the effective " carrying capacity " of a well-constructed and capably handled aeroplane. If, in addition to the foregoing, we bear in mind that to-day the launching facilities are so improved as to enable an aeroplane to rise after a run along the ground for 50 to 70 metres, we may see what gigantic strides have been made, even in a year, by this " heavier than air " apparatus. It was only a few years ago that it was laughed to scorn as much as it is greeted enthusiastically to-day. Finally, it may be said that the aeroplane is no longer confined in its flights to aerodromes. Farman and Bleriot made the first cross-country journeys through the air. Latham, at Berlin, during the winter of 1909, flew over a city for the first time. He journeyed from Tempelhof to Johannisthal, and passed over the capital of the German Empire. Some days later, in a graceful and daring flight, one of Wright's pupils, Count Lambert, a Russian aviator, set out from Juvisy, flew over Paris, rounded the Eiffel Tower, and returned to Juvisy, where his descent was made, to the accompaniment of an indescribable ovation. On April 23 Emile Dubonnet crossed Paris on his Tellier monoplane. Nor must be overlooked the audacious flights of Rougier at Monaco, where he flew over the sea and the " Tete du Chien " ; those of Paulhan and his rival Graham White over the towns and cities of this country ; the striking performances of the French aviator-officers who accomplished, under service conditions, the voyage Paris-London and Paris-Bordeaux, with passengers. Such enable us to realise that the aeroplane is commencing to fulfil anticipations. It is permissible to fore- shadow the time of its entry into our everyday life, inasmuch as now we take no notice of journeys from town to town the exceptional of a year ago has become the commonplace of to-day. EARLY DAYS OF AVIATION 205 THE ENTHUSIASTIC PUBLIC MOVEMENT IN FAVOUR OF AERIAL NAVIGATION: "AVIATION MEETINGS" From the day when Farman won the Deutsch- Archdeacon prize, aviation created an indescribable enthusiasm among all classes of the community. For a year the shops and vendors of post-cards sold nothing but photographs of aeroplanes, portraits of aviators, and illustrations of motors. The wide- spread publicity with which the managers of the Brothers Wright surrounded the experiments of the American aviators, helped to maintain this movement, and the numerous excur- sions of the dirigibles, which continually described evolutions over Paris, prolonged the absorbing interest of the people, provoked by the success of aviation. At Auvours enormous crowds flocked from all parts to witness the Wrights' flights. At Issy-les-Moulineaux, where in the early days the heroic times the use of a manoeuvring ground had been granted very reluctantly to the French aviators, whereas such a space was placed liberally at the disposition of the foreign aviators, thousands of the curious were always present to assist a flight or a descent, notwithstanding the early hour (from 5 to 7 A.M.) that was imposed upon French investigators. Cinematographs have reproduced and popularised the most successful flights; the annual reviews have introduced the aeroplane into their pictures extensively. The latest achievements of Bleriot, Farman, Dubonnet, Paulhan, and many other champions of the air, as well as those of the French aviation officers, Leblanc, Aubrun, Legagneux, the Circuit de VEst, have infused the whole world with an inde- scribable enthusiasm. In the shops the up-to-date toy which commands the greatest sale, and which " rises " into the air, is the little monoplane or biplane aeroplane driven by an india- rubber elastic band. But it was in the imagination of the young folks that aeronautical schemes were conceived. They dreamed of nothing but aviation. At college they made paper aeroplanes under the cover of their desks, to guard them against detection by their tutor; whilst the latter, studying for his science degree, on his part was occupied in calculating the elements of 206 THE CONQUEST OF THE AIR some flying-machine that would revolutionise the field of aerial travel ! The fair sex has taken to the new method of locomotion. Already graceful " aviatrices" are popular at the aerodromes, such as, for instance, Madame Delaroche, the first lady to handle an aeroplane unaided, and to obtain the aviator-pilot certificate, Miss Dutrieu, Miss Aboukaya, &c. Aeronautical construction shops have sprung up on every side. Aeroplane constructors have their catalogues illustrated with aviation apparatuses, " payable after trial by the customer," whilst sign of the times agencies have been established to facilitate such transactions. It has become necessary to satisfy the desires of the public who wish to see "flying" beyond the limits of the cinemato- graph. Consequently meetings, " aviation weeks," have been inaugurated, which, by the offer of attractive prizes, have brought together a large number of aviators. The first and most historical meeting of this description was that held at Rheims in the autumn of 1909. It was organised by the Marquis of Polignac, and it attracted visitors from all parts of the world. It served to show Europe how aviation had developed under the impulse of French genius. Since then meetings have succeeded one another without cessation at Pau, Brescia, Heliopolis (in the early part of 1910), Nice, &c. To-day there is no city which has not had its " aviation week.'' The Circuit de VEst, the first opportunity afforded aeroplanes to race over a measured definite course on days fixed in advance, like a race-meeting, demonstrated in August 1910 that the " heavier than air " apparatus was no longer an experimental appliance, but a vehicle of practical value. The prizes offered at these various meetings were consider- able. In order to afford an idea of their character we give a selection of the winnings of some aviators at these various weeks": CHAMPAGNE WEEK RHEIMS, August 1909 Farman . . . -/.A.,; . 2400 Latham . 1946 EARLY DAYS OF AVIATION Curtiss 1520 Bleriot 500 Paulhan . 400 207 HELIOPOLIS WEEK EGYPT, February 1910 Rougier . Metrot Le Blon . Balsan Reimskyck . 3640 . 2400 . 640 . 340 100 NICE WEEK April 1910 Efimoff Latham Van den Born Duray Chavez 3102 2422 1088 782 622 To the above must be added such a trophy as the Daily Mail prize of 10,000, which Paulhan won in so brilliant a manner by flying from London to Manchester. One may have cause to envy the calling of the aviator, who, if he does incur risks, has so many advantages to excite the imaginations of the young. This movement was interpreted, some years ago in France at any rate, by the foundation of an aerial League, which had the happy inspiration to have resort to the knowledge of Professor Paul Painleve. An " Aviation Committee " has been formed in the French Senate under the presidency of M. d'Estournelles de Constant, while an Aerial Locomotion Commission acts in the Chamber of Deputies. But this enthusiastic movement is reflected especially in the redoubled efforts among societies actively concerned in the matter of aeronautics. There are the Soci6tt frangaise de navigation aerienne, under the presidency of 208 THE CONQUEST OF THE AIR M. Soreau, generally recognised as the oldest, since it was founded in 1872 ; lAe'ro Club de France, equally publicly appre- ciated, presided over by M. Cailletet, of the Academie des Sciences, the efforts of which have been so fruitful in the diffusion and development of aeronautics in all its branches ; V Aeronautique Club, I'Acadtmie Aeronautique de France, I 9 Aviation Club ; the Stella, an aero -club exclusively devoted to ladies ; while other societies have increased appreciably the number of their members. At Brussels, I'Atro Club de Belgique, ably presided over by M. Jacobs, a learned double of Msecene, has followed the example of its French brothers, and is progressing in a remarkable manner. In Germany, England, and Italy the same activity is manifested. And in turn, special newspapers and journals have been created. Let us recall, first, the two original organs of aerial locomotion, I'Atronaute, founded in 1866, and VAerophile, that remarkable paper directed by so great an authority as M. Georges Besangon. These two periodicals constitute the archives ot aerial navigation, as much for the past as for the present, and we have drawn extensively upon their files, with the requisite permission, to write this book; to their editors we extend our thanks. Around them have sprung up l'A6ro, la Revue aerienne, la Revue de V Aviation, V Avion, V Aviation illustre'e, &c. In Belgium two excellent reviews, La Conqudte de I' Air and I'Ae'romecanique, have a wide circulation ; and it is the same in London, Berlin, and Italy. And all this is the result of the triumphs achieved during the past few years. What is the outlook for to-morrow ? and how striking is the consciousness of mankind of the value of the great inventions which are perfected to modify in a far- reaching manner the conditions of existence and of social life ! THE MARTYRS OF AERIAL NAVIGATION : DIRIGIBLE CATASTROPHES : AEROPLANE DISASTERS If aerial navigation counts its victors alas ! it numbers also its victims. Every great development in civilisation has milestones of mournful significance, and the history of dis- covery is often written in blood. It seems as if Nature, jealous of the inviolability of her secrets, wreaks revenge EARLY DAYS OF AVIATION 209 upon those so audacious as to seek to reveal them, and parries the efforts of those who attempt to unravel the mystery of her laws ! The conquest of the air, like all other conquests, has its battlefields strewn with the remains of its heroes. In its two forms it has already a long martyrology, and we will recall briefly the foremost disasters which have befallen aeronautics and aviation. We will omit accidents to spherical balloons; they are legion, and in recent times, in Germany particularly, they have increased in an impressively tragic manner. The two greatest catastrophes to dirigibles were those of the German vessels the Deutschland and the Schwartz. In 1896 the aeronaut Wcelfert built a balloon 28 metres long by 8-5 metres diameter, and of 800 cubic metres capacity. Two propellers, wrought in aluminium, of 2'5 metres diameter, were driven by an 8 horse-power Daimler petrol motor. The experiments were continued without success, and on June 14, 1897, the airship exploded, owing to the gas being in too close proximity to the motor, and becoming ignited, it fell to the ground, and the two aeronauts were mutilated terribly. In 1897 an aluminium balloon, built on the rigid principle by the German aeronaut Schwartz, came to a similar end, but the aeronaut had the opportunity to save himself, though he was severely wounded in the ordeal. Coming to the year 1902, we find two terrible calamities which happened in Paris to two airships, Pax and Bradsky, the first built by the Brazilian Severo d' Albuquerque, the second by the German engineer Bradsky. The Pax was a fusiform balloon, symmetrical, with too slight an elongation, built up of a rigid frame to which were fixed the shafts of the two propellers, which revolved upon the axis of the envelope. Severo suppressed the ballonnets in the balloon, and the explosion motors were set scarcely 2*5 metres away from the envelope ! On May 12, 1902, the balloon, being released; ascended very rapidly; the stern screw refused to act; the disabled vessel tilted ; a jet of flame was observed at the top of the car, there was an explosion, and the whole apparatus tumbled 210 THE CONQUEST OF THE AIR to the ground. The body of the unfortunate Severo and his luckless mechanician were found masses of bleeding pulp. This disaster, which occurred in Paris, caused a profound sensation. Four months later, on October 13, 1902, the German aeronaut Bradsky ascended in a semi-rigid airship of cylin- drical shape, terminating in a point at the prow and in a hemisphere at the stern. Here again there was no ballonnet, and the suspension was simply of the parallel type. This was the cause of the disaster. At a certain moment the aeronauts attempted a sharp turn. This set up a torsion in the suspension. The absence of the ballonnet caused the gas, a quantity of which had escaped during ascent, to rush towards the prow. The balloon reared up, and the suspension, essentially deformable, was unable to carry the weight equally. That to the front had to carry the weight of the car, motor, and passengers. It collapsed, and the two unfortunate aeronauts were thrown to the ground, where their bodies were literally buried from the force of the fall ! French aeronauts had been spared up to this time. There was the loss of the Patrie, carried away by the gale, but that was a material loss purely. In the month of November 1909 occurred one of the most terrible catastrophes it is possible to conceive the disaster to the French military dirigible Republique, carrying Captain Marechal, Lieutenant Chaure, and Adjutants Reau and Vincenot. The Eepublique had returned from the manoeuvres, and had regained Chalais-Meudon by the aerial highway. Some automobiles followed the airship. Suddenly a kind of detona- tion was heard, and the dirigible crashed to the ground with the four officers aboard. The cause of the accident was novel. One of the blades of the propeller, torn loose by centrifugal force, struck against the envelope, tearing a large rent, through which the gas rushed. The balloon fell like a stone, and struck the ground with terrific force. This fearful calamity drew attention to the use of wood for propellers. This national disaster created widespread consternation. A subscription opened by M. Hebrard, the director of Le EARLY DAYS OF AVIATION 211 Temps, was overwhelmed with signatures. In a few days a large sum had been obtained, which permitted, owing to the patriotic sacrifices made by the Astra, Zodiac, Wright, Bleriot, Henri and Maurice Far man companies, to offer for the' national defence an aerial cruiser of 8000 cubic metres, another of 2000 cubic metres, and four two-seated military aeroplanes, as a substitute for the lost unit. In Germany accidents to dirigibles have been numerous. Five out of six Zeppelins have been destroyed by mishaps at landing, happily without a death-roll. But in the month of July last the dirigible Ersbslah, had a tragic fall and killed five people. The list of victims in aviation, too, is long. The first name inscribed upon this sad albeit glorious scroll of honour is that of the German Otto Lilienthal, who carried out most remark- able experiments in gliding. Lilienthal effected his aerial " glides " with an apparatus of supporting wings, but without a motor. He had made hundreds of these glides with complete success, when, in the course of his last flight, the apparatus was capsized by a current of air, he was thrown to the ground, and had his neck broken by the fall. Since the advent of the motor- driven aeroplane that is to say, since 1908 many aviators have paid for their aerial skill with their lives. First, in the United States, the American lieutenant Selfridge was killed by a falling aeroplane, in which he had ascended as a passenger with Orville Wright, one of the Wright Brothers. The latter escaped with an arm and leg broken. This occurred in August 1908. On September 7, 1909, at the Juvisy aerodrome, the aviator Lefevre had an unfortunate fall and met his death. On September 22, near Boulogne, Captain Ferber, of the French artillery, one of the aviation pioneers, and one w,ho, as much by his theory as his practice, accomplished a great deal in the development of the new means of locomotion, was killed in an inconceivable accident. He had not risen into the air ; his apparatus was running along the ground, which it had not yet left. It was at the moment of " launching." Suddenly the apparatus overturned, fell to the ground, break- ing the neck of the unlucky officer by its weight. 212 THE CONQUEST OF THE AIR At Nice, on December 6, 1909, the aviator Fernandez, piloting an aeroplane which he had devised and built, fell and was killed. Delagrange, one of the first champions of the aeroplane in France, who mounted the first Voisin machines, and who was the first to carry a passenger into the air, was killed at Croix d'Hins on January 4, 1910. He was on a BUriot, and find- ing the power of the motor to be inadequate, he substituted another engine of twice the power. In so doing did he alter the stability conditions of his apparatus ? At all events the unfortunate aviator had a fatal fall. At St. Sebastian, towards the end of March 1910, Le Blon fell vertically from a height of some 50 metres into the sea, and was killed instantly ! Roble was killed at Breslau on July 18, 1910. Wachter met his end at Rheims on July 13. Rolls, who made a brilliant round trip across the Channel, was thrown to the ground at Bournemouth on July 12, and was like- wise killed. Kinet, a Belgian aviator, after some magnificent triumphs, met his death at Liege on July 15, 1910, and on August 3 his cousin Daniel Kinet was killed, whilst on the same day Walden had a fatal fall at Minneola (Long Island, U.S.A.). On August 20 the Italian lieutenant Pasquo Vivaldi fell and was killed instantly ; on September 20 Poillot succumbed from serious injuries after a terrible fall at Chartres, and on September 28 George Chavez, the conqueror of the Alps, and the first to gain the glory of flying over that formid- able barrier, fell at Domodossola after having crossed the peak of the Simplon. He had gained altitudes of over 2000 metres without incident, to be killed during descent by a fall from a height of ten metres ! Such is the fatal list ! It is a long one already sixteen aeronauts and sixteen aviators ! All honour to the memory of those heroes whose lives have been the ransom of progress. CHAPTER VII THE FUTURE OF AERIAL NAVIGATION AERONAUTICS AND AVIATION : APPLICATIONS TO WAR, CIVIL LIFE, AND SCIENTIFIC INVESTIGATIONS I ECO- NOMIC IMPORTANCE OF AERO- LOCOMOTION DIRIGIBLES OR AEROPLANES? IT now only remains for us to ascertain what is the future of this aerial locomotion, which at present is so full of promise and has developed with a rapidity never before witnessed hi the evolution of any other invention. And, above all, it is necessary to examine individually the possible applications of the two forms of aerial locomotion, and the two types of atmospheric vehicles dirigible balloons and aeroplanes. To which shall we give the preference, and what is the future of each ? If one were to be guided only by public enthusiasm, a trifle " packed," and so strenuous in exaggerating the merits of an invention when it " succeeds," as it is often slow to recognise it in its infancy, then aeroplanes, the last to come into popular favour, would be the only machines capable of widespread application. Scientific writers in the Press have submitted them already to all kinds of work, and they hasten to anticipate all the services which they must fulfil in the very near future, whilst they cannot defend themselves against a shade of disdain for the large airships which we saw perfected " yesterday " in the eagerness for that of " to-day." It is necessary to allay this premature enthusiasm a trifle, as it is prone to be overdone again. It is essential to avoid, in the desire to advance too quickly, those galling experiences that occurred with motor-boats when the fanatics hailed them as the torpedo-boats of the future. The ridiculous 213 214 THE CONQUEST OF THE AIR venture upon the transmediterranean race, which a little consideration would have avoided, and in the course of which all the boats participating, except one, were lost, must serve as a lesson and give food for thought to those organisers of too premature applications. Let us say at once that the future is immense, so immense that it is impossible to set it out in detail. But progress will be by evolution, and all that one can do actually is to indicate the broad lines. In the first place there must be no exclusion of either of the two systems, balloons or aeroplanes : both have their raison d'&tre because they correspond to different requirements. When it is necessary to travel very rapidly, when, above all, progressive development has assured the perfect security of aviation apparatus, one will have recourse to the aeroplane. Without doubt we shall see "aeroplane liners" of large dimensions, carrying numerous passengers, securing sustentation with nothing but their enormous speeds. But these velocities would be attended with real dangers in case of landing, or, above all, a " mishap to the machine," because, if the apparatus sustains itself by high speed, it would not have sufficient supporting surface to keep soaring without the motor. Perhaps for this reason aeroplane liners will be reserved even for transatlantic passages, as the " hull " with which they necessarily must be equipped would render landing less dangerous upon the water. Transatlantic journeys would be made at speeds exceeding 200 kilometres per hour ; that is to say, one could travel from Europe to the United States in a single day ! But when this speed is unnecessary, it appears scarcely possible to disclaim the envelope charged with light gas, this " bladder," as it is called disdainfully by some aviators, because, if it travels at less speed, nevertheless it has the advantage of sustaining the aerial navigator in the atmosphere without the need of mechanical energy. Consequently it assures safety, and should the motor of an airship break down one would be always master of the situation, or able to continue the journey "before the wind," if the latter were in the right direction; or to land, which with a capable aeronaut would FUTURE OF AERIAL NAVIGATION 215 be possible always without very great risk, if one carefully excludes the use of rigid airships, all of which have finished their careers in disaster at landing, because of difficulty in handling and the impossibility of deflating them. Moreover, an airship can carry many more passengers. It can convey them in greater comfort. When it will have attained its independent speed of 60 or 70, instead or 40 or 45, kilometres per hour, it will be able to set out practically at any time. Lastly, it can " stop " at any determined point in the aerial ocean, which the aeroplane, tributary to an indispensable sustaining speed, cannot do. Also I do not deceive myself in stating that its career is far from ended. It has no more than begun, and its development will be contemporaneous with that of the aeroplane. Let us now examine some of its applications to aerial navigation, and we will see then which is the type of locomotion best adapted to each case. MILITARY APPLICATIONS The perpetual tendency among nations to threaten to destroy one another by the most perfected means has resulted, first and foremost, in the application of aerial navigation to warfare. We all know how completely France secured an advantage over all other countries by the possession of a military dirigible, La France, in 1885, whereas no other nation had one at its command. During the last few years the successive appearances of the Lebaudy, La Patrie, Ville de Paris, the JRfyuUique, the Bayard-CUment, and the Zodiac (I omit all but the best) have shown Europe that France has an " aerial navy " in being, available for the defence of her frontiers. We have pointed out also the progress Germany has made in regard to dirigible balloons, and what an aerial fleet she possesses with the several Grross, and especially with the Parseval vessels. On the other hand, the Zeppelins have given nothing but disappointment, whereas the French military aeroplanes have surpassed the fondest hopes they fostered at their dtibut. What type of aerial vessel will serve the needs of warfare best ? The airship or aeroplane ? As " combatants " or " scouts " ? 216 THE CONQUEST OF THE AIR I fear, after what I have heard from officers who are more competent on this subject than I, that as a combatant the airship will not be used often. Aerial battles do not appear imminent because the installation of any artillery whatever on board dirigible balloons would be extremely inconvenient ; with regard to aeroplanes, their requisite high speed, and the impossiblity of " pulling up " practically prevent the use of cannon except of small calibre. There is one good use for the airship in war : that is to drop melinite shells (or some other still more devastating explosive that may be invented) from a height into a fortified area or a besieged fort. Here we are in the realm of the possible, and this utilisation of the airship is not chimerical. It is only requisite to consider if the " result " would be very advantageous. But experience can offer testimony on this point. In the United States it was proved with striking success under par- ticularly difficult conditions, especially in connection with aeroplanes. Such, therefore, opens up a certain sphere of utility in combat. France, who, through her aviators, has resumed the lead among the nations in the conquest of the air, now has a military superiority as incontestable as the existence of her aeroplanes, and accomplished aviation officers who, at the " Circuit de 1'Est " and at the Picardy grand manoeuvres, excited admiration on all sides. Moreover it may be pointed out that aerial vessels have little cause to fear hostile projectiles airships because of the altitude at which they are able to float, and aeroplanes on account of the heights they can attain, and chiefly owing to their speed. During the siege of Paris in 1871, only one balloon was captured by the German troops ; then the pilot who controlled it was but little experienced in aerostation. Pausing to consider the possibility of an "aerial combat" between isolated units, it is certain that if two hostile aerial vessels met in the air they would seek to destroy one another. If they were two aeroplanes, and unless the fire from a mitrailleuse of one put the motor of the other out of action, or rendered the aviators hors de combat, they would be unable to withstand the collision ; then there would be no conqueror, FUTURE OF AERIAL NAVIGATION 217 no conquest; there would be only two simultaneous catas- trophes. Would dirigibles, always cumbersome and relatively slow, much dread the pursuing speedy aeroplanes ? Possibly not, because the aeronaut, when the aviator chased him in his speedy aerial skiff, would avail himself of a resource the efficiency of which is certain : he would rise by throwing out ballast. He would fly up in a vertical line, that is to say, would ascend very rapidly, whilst the aviator could rise only obliquely, and then in a slight slope, thereby executing zig- zags, in a word, "vertically tacking." We have seen that Latham required forty- two minutes to rise 1000 metres at the Chalons camp. Lastly, whilst making its vertical tack to come up with the airship, the latter, more stable and able to carry, if not guns, at least a quick-firing weapon, or in any case grenades, would have ample time to riddle its aggressor, and much more easily than it could by firing upwards, all the more so, because the artificial bird would offer to the fire of the airships the large target of its supporting wings. Meantime, however, the aspect of this question has changed, inasmuch as aeroplanes do not fly near the ground as they did a year ago, but now rise to extreme altitudes in fact, to much greater heights than dirigibles. The height record of the latter type is 1550 metres (Capazza on board the Bayard- Clement), whilst aviators have attained and exceeded 2500 metres (Morane 2521 and Chavez 2562 metres respectively). The military value of aeroplanes, consequently, is increased from the fact that they can rise very high, and thus render themselves almost invisible to the enemy's artillery. To sum up, I believe, therefore, that aerial vessels will be poor combatants between themselves. On the other hand, they will be useful scouts, and this will comprise their principal role in the time of war. Dirigibles, being able to carry instruments of precision capable of stopping to take a photograph or to make telemetric measurements, will be extremely valuable to the chief of an army who has them at his disposal ; but aeroplanes, owing to their great speed, will be the instruments par excellence for rapid reconnaissances, for " raids " carried out over great distances ; moreover, their capability of returning very speedily 218 THE CONQUEST OF THE AIR to recount what they have seen will render them still more indispensable than their " larger brothers " to the general of the future war. The Picardy manoeuvres proved the invalu- able services they can render to a commander-in-chief, and now that two officers can be stationed on board, a pilot and an observer, nothing can escape their rapid and positive investigation. For communication with besieged positions the aerial vessels will be unrivalled, and no longer will it be possible to isolate a fortress completely, what with wireless telegraphy and a fleet of airships, or a flotilla of aeroplanes. With regard to uses in naval warfare, without a doubt these will be numerous. A cruiser can always have on board one or more aeroplanes ; it has even the mechanical energy necessary to launch them. It can consequently send one into the air to sweep the horizon, and a hostile fleet could not con- ceal itself easily. Moreover, aeroplanes will be able to drop shells upon the bridges of an enemy's vessels, and it will become necessary in the construction of warships to protect this vital point from aerial attack. Undoubtedly the number of submarines will not be increased, since aeroplanes peering vertically into the waters of the ocean will perceive the torpe- does and submarines at a very great depth, whereas from the surface of the sea they could not be seen at all, owing to the obliquity of the visual rays coming from less distant points. Will battles then be decided solely under the waters ? Mys- tery and horror ! Let us hope that these events will never come to pass. APPLICATIONS TO CIVIL LIFE What will be the " civil " applications of locomotion in the air ? Evidently they will be numerous and varied, and it will be possible to travel either by " public service " or by private vehicles. Undoubtedly the latter will come first into vogue. Private airships and aeroplanes will for a long time yet be vehicles de luxe, I may even say of great luxury, and only those privileged by Fortune, or those who wish to appear so, will be able to make avail of their use. But did we not see the same develop- ment in regard to the automobile ? Will not the desire to FUTURE OF AERIAL NAVIGATION 219 appear, like " our friends," in a dizzy aeroplane, turn society upside down ? without speaking of the fascinations of the " special costume " which the enterprise of our great dress- makers will not fail to bring out at the happy moment, and to charge for accordingly ! It cannot be denied that speed has an irresistible attraction ; it produces peculiar sensations, a verit- able intoxication, and to taste these sensations combined with a decrease in the time occupied on a voyage will be one of the next forms of refined luxury. Besides, does not the reduction in the length of a journey increase the available time for other things, and therefore does it not, in an indirect manner, lengthen the span of life ? Among these vehicles de luxe aeroplanes will be the "racers" : they will travel rapidly; will be able to carry two, three, or more persons. They will displace the high-speed automobile in which fanatics hurtle along at some 80 kilo- metres per hour; only in the air it will be "some 200 kilo- metres per hour." Those who are content to travel quietly and in company, and who are possessed of the " wherewithal," will favour dirigibles. Before long these will travel at 60 or 70 kilometres per hour. Certainly it is highly enjoyable to have an extensive uninterrupted view, and without having to stop on the way. Let us point out, moreover, that if by a head wind the speed of the wind curtails that of the balloon, on the other hand, when the wind is following, the two speeds have to be combined ; and in choosing his wind that is to say, the day for his trip, which is possible to those of indepen- dent means one will make "some 100 kilometres per hour" in an airship, with the additional advantage of comfort obtain- able with this " travelling coach " of the air. Then, without doubt, numerous sheds " hostelries for balloons " will be distributed along the great highways, and one will be able to stop en route, as is now possible on motor trips. So far as " public transport by airship " is concerned, this stage has not been reached yet. The unfortunate efforts in this direction by the Deutschland, the last Zeppelin to be destroyed, whereby a series of regular journeys was inaugurated ambitiously, and in the course of which a dozen travellers almost met their deaths, shows us that this application is still premature. 220 THE CONQUEST OF THE AIR Let us remark, though, that for some time yet the greater bulk of the population will have to go on foot, by motor, boat, or railway. The high aerial speeds will be a luxury or sport. The conveyance of merchandise will be always by land or water. Such will be accelerated, but I do not think that for many, many years one will consider despatching goods over the aerial highway. And yet the public authorities of the different European nations are engrossed in this great problem. Aerial navigation in effect eliminates frontiers. If ever it assumes sufficient extension to permit of the transport of merchandise the days of the " customs " and their enormous revenues are numbered. As a matter of fact, was not the first International Diplomatic Aerial Navigation Conference, held at the French Foreign Office in Paris on May 18, 1910, called to discuss and control this question of commercial transport over the aerial highway, as much as questions of military import ? All the European Powers were represented, and the author of this volume had the honour to be one of the plenipotentiaries. The work of this conference was of such importance that it was not concluded at the time this book was published, and the international code in regard to the atmosphere is not promulgated yet. Nevertheless, there is one phase of transport which will use the highway of the air, and perhaps more so than we anticipate. This is the " Post Office " for the conveyance of correspondence. I believe that before long " mail " will be sent aerially, and for this aeroplanes will be vastly superior to balloons. Being able to set out at any time, travelling at enormous speeds, they will carry letters and valuables. It will be easy to despatch them, one after the other, in all directions. Thus we shall have " hat-bands" for " aeroplane messengers," who will go direct from city to city every hour, or even more often. The only interruptions to such service will be on days of heavy storms. Then it will be necessary to trust the messenger to express trains, which will travel at far greater speeds than now. Even then distant points will complain bitterly of intolerable delay. FUTURE OF AERIAL NAVIGATION 221 Undoubtedly the appearance upon the scene of aerial vehicles will modify profoundly the conditions of our exist- ence, but it is not necessary to count upon this change coming too quickly. It will be some time before we see " aero-taxis," and the transit in towns will be maintained for many years to come by terrestrial vehicles. But it is certain that some day architects will feel compelled to cater for the aerial vehicle with elevated inooring-stations. Roofs will disappear in favour of flat terraces suited to launching and landing. Probably, however, departure will not entail more than a short running start. Such will be made in situ, because the flying apparatus will be, without a doubt, a combination of the helicopter and the aeroplane, an association which will assure security in the descent in confined areas and at a very great speed. Perhaps upon these flat roofs of large hotels we may even see sheds for airships ! Certain it is that the "future city" will not have quite the same appearance that it possesses to-day. Wealthy residents will always turn their ambition towards the clearer, healthier, and less congested air. SCIENTIFIC APPLICATIONS : EXPLORATION OF UNKNOWN COUNTRIES One of the first applications of the new locomotion will be of a scientific nature, and more especially of a geographical character. The facility in moving above all the obstacles with which the surface of the earth bristles renders it eminently suited to the exploration of unknown continents, to traverse which no means of communication exist. One knows how difficult and dangerous is the exploration of the mysterious countries, such as those of Africa, the centre of Asia, and Central South America, whilst the torrid climate, the dense vegetation forming impenetrable obstacles, dangerous animals and hostile natives, seem to league against the explorer sufficiently bold to venture into those territories where the foot of a European has never trodden. Also, what blanks exist still upon the maps of Africa, Asia, Australia, South America, and the Polar regions, Arctic and Antarctic ? How slowly, in fact, are geographical discoveries effected when it is necessary to explore the details of our planet 222 THE CONQUEST OF THE AIR by " crawling," so to speak, over its surface ! When the explorer advances through the torrid equatorial regions, when he must toil through the bush, it is as much as he can cover from 5 to 20 kilometres per day. This is the average advance of an exploring expedition. If a passage must be cut through the dense primeval forest by hatchet and axe the advance is slower still. In exploring the glacial lands of the Poles, the "icefields" of Greenland, Spitzbergen, or of the Antarctic, it is not always in kilometres that the distance between the daily halting-points is figured. Furthermore, the privations and dangers are proportional to the road traversed each day. What is the data which the geographical traveller secures in the face of such innumerable perils ? Does he bring back the complete map of the country he has penetrated at the risk of his life ? No, unfortunately, because in order to prepare a complete survey of a region it is necessary to stay there a long time, and to travel in all directions. More often than not the explorer shows merely his itinerary, that is to say, only the country "fringing" the path which he followed. Certainly he will record what he sees to the right or left of this route, will indicate the hills and mountains which he has perceived on one side or the other, with their distances and heights, estimated according to "bearings." But they will only widen his " fringe " slightly without giving a general map. Moreover, the regions described in this manner will be rather more indicated than charted with essential geographical precision. In reflecting upon these difficulties one can understand the existence of the " white spaces " in our atlas. It is marvellous that man has been able to gain such actual knowledge of the Earth in face of the passive hostility of an unknown country. All this time, however, although we have been powerless to learn the details of the surface of our own planet, astronomers have succeeded in gathering all the details of the surface of the sky, to enumerate up to a very extended limit the brilliant stars which are sprinkled above us briefly, they have made a map of the heavens. a: O a" P FUTURE OF AERIAL NAVIGATION 223 They have evolved it, moreover, through a unanimous understanding among the civilised nations; they have pre- pared it by a surveying method which furnishes indisputable testimony photography. The photographic plate, as was said happily by Janssen, is the " retina of the savant," but a retina which retains the impressions it receives. Hitherto, certainly, it has been impossible or, at the very least, difficult to apply photographic processes to the representa- tion of terrestrial surfaces in the same manner as in the pre- paration of the map of the heavens. In short, one had no means of " seeing the earth from above." The balloon, and captive at that, was the sole method available, and it was scarcely able to provide more than " local " views of the country beneath. Then, to obtain sufficiently numerous photographs it would be necessary to tow a captive balloon across the continent to be explored, and consequently to transport it, and its accessories, by means of a caravan. Up to now this difficulty has never been overcome. Now, on the other hand, the dirigible balloon furnishes us with the solution so much desired, and I believe that it will fulfil it in a complete manner, thanks to the addition of topographical photography in the form so excellently and so precisely devised by Colonel Laussedat about 1852. Let it be pointed out at once that taking only the road traversed, and even if it were kept within certain limits, the dirigible aeronaut-explorer, by vertically photographing the earth above which he manoeuvred, would be able to obtain a route survey of a superior character to that which explorers travelling over the surface of the ground would be able to evolve. Indeed if, for example, he stood at a height of 1000 metres while photographing the earth beneath with an apparatus of which the wide-angle lens had a " field " of 90 degrees of angle, and a focal length of 20 centimetres, he would obtain a photo- graph which would be a topographical map on the scale of 50QO* But this map would be both exact and complete. It would be possible to obtain numerous photographs, and by placing them side by side one would have the detailed and correct topography of the route followed by the airship. Furthermore, as the latter would travel at 58 kilometres per 224 THE CONQUEST OF THE AIR hour, the explorer could take more maps in one hour than the ordinary explorer could make in three days, and it would be done without danger, without fatigue, safe from the attacks of natives, and protected above all from the onslaughts of poison- ous insects, from marshy miasmse, which are the greatest enemies against which explorers have to contend. An airship of to-day (as many dirigibles have demonstrated) can travel for 38 hours without descent. Therefore it would be possible to make an outward journey for 19 hours, allowing 19 hours for the return trip, anchor for the night, and in this manner explore the country within a radius of a circle of 1000 kilo- metres, which would take a traveller from 40 to 50 days to pass over. But, notwithstanding the already very marked superiority of an aerial voyage from the point of security, speed, and the data obtainable, the point arises as to whether the results would justify the despatch of a dirigible to an accessible point of the continent which it is desired to study. However, then one can and must rely more and rather upon the collaboration of the dirigible and the camera. Let us state at once that the dirigible will be improved greatly within a very short time; its present speed of 50 will be increased to 6 kilometres per hour ; its volume will be augmented, and in place of 3000 to 3500 cubic metres it will have from 6000 to 8000 cubic metres while still preserving its " elastic " construction and not falling into the drawbacks of the rigid balloon. Airships of this volume are already in course of construction in Paris. If, under these conditions, one is content with a speed of 50 kilometres per hour, which is magnificent, one will be able to carry sufficient fuel for a continuous voyage of 50 or 60 hours, which means 25 to 30 hours for the outward and the same for the return journey. But hi 25 hours a balloon travelling at 50 kilometres per hour would cover 1250 kilometres. It can descend during the night when photography is impossible, setting out again the next day and even stopping en route if necessary. The perfection of the special balloon " fabrics," and the judicious use of the air-ballonnet, enables the balloon to remain in the air without any loss of gas, and the airship Patrie, which was FUTURE OF AERIAL NAVIGATION 225 perceived floating in the North Sea ten days after the storm tore it from its anchorage, shows the strength of the modern airship. We are able to say that airships of from 6000 to 8000 cubic metres volume, and having from 1000 to 1200 kilometres " radius of action " are in course of construction. Consequently, in selecting convenient " centres " for establishing aeronautical stations, centres which will coincide with inhabited and accessible points to which one can easily convey the material and personnel, one will be able to cover a continent with a network of circles of 1000 to 1200 kilo- metres radius, each of which can be traversed by an airship carrying the explorers and their instruments in 20 or 25 hours. Fig. 81 shows how one can apply this system of exploration, which is so simple, so rapid, and so safe, to a prescribed region. The centres indicated in this example are accessible. Two are in French, two in English, and one in Belgian territory. They are Timbuctoo, the shores of Lake Tchad ; Leopold- ville, for the Belgian Congo ; Dongola and Lake Albert for the English stations. In describing about these centres circles of 1100 kilometres radius it is seen that the whole of Central Africa can be covered thereby, and the circles even " overlap." Therefore the exploring traveller in his dirigible can touch every part of the unknown country. Even the provision and the maintenance of the aeronautical stations for the immediate return journey may be dispensed with, as it can halt at a different centre to that from which it set out, which may be of great value in case of an unexpected storm. In this instance I have confined myself to Central Africa; by adding a sixth centre at Dakar the whole Mauretania would become " explorable." Would airships which accomplished these expeditions be limited to securing " route photographs " ? No, they would do much better, thanks to Colonel Laussedat's process, the principle of which I will explain in a few words, In 1852, Colonel (then Captain of Engineers) Laussedat, impressed by the advantages that photography would afford in the compilation of maps, evolved a means of preparing topographical surveys by means of Daguerre's invention. For 226 THE CONQUEST OF THE AIR this purpose he employed not one photograph, but two, taken from the extremities of a long known so-called base. If one knows the angle of the lines of vision of the two apparatuses which have their optical axes turned towards the same point, from the two extremities of this base, one has a triangle, the two photographs taken simultaneously from which enable one to build up the actual structure. It is in fact " plane table " topographical surveying, with this difference, that instead of carrying out the graphic work upon the spot, one " carries the ground with him " and completes the work in the drawing office. This excellent method is even capable of simplification. It suffices to place at the two extremities of a " base," the absolute length of which is known, two cameras, the objectives of which have their axes absolutely parallel, and to actuate their shutters at the same moment, which is a very simple matter with a battery and two electro-magnets. From these two photographs one can compile the map of the country up to the limits of the visible horizon by means of Dr. Pulfrich's remarkable instru- ment, the stereocomp&rateur, built by Zeiss, the eminent optician, one of which is retained in the museum of the Conservatoire des Arts et Metiers. A most renowned German Geodesian Professor, O. Hecker, of the Potsdam Geodesical Institute, has shown how one can make the most of this process. And this simultaneous use of the parallel two cameras at the ends of a base of known length is possible on board a dirigible of the Bayard-Cl&ment type, for example. The rigid and indeformable car, of which the length is 28 metres, will be the supposed base. The two cameras will be fitted perma- nently at its two extremities ; their distance apart is at one and the same time definitely known and invariable. On board a dirigible of the largest dimensions the same two cameras could be installed about 50 metres apart, thus having a still more effective base. The photographic data necessary for the compilation of the map by the aid of the stereocomparateur in consequence will be absolutely correct. In this manner it is not merely a route survey obtained by photographing the sub- jacent ground that the aeronauts will bring back with them. These are the component parts for a "geographical map" as FUTURE OF AERIAL NAVIGATION 227 far as the limit of the visible horizon, a map correctly " fixed " both vertically and in distance for planimetry. Thus a few aerial expeditions made in the interior of one of the circles of which we have spoken will more than suffice to furnish the map of the entire coun- try included therein. But in order to render this endeavour practic- able, the assistance of several nations is neces- sary. The map (Fig. 81) shows that for Central Africa that of France, England, and Belgium would suffice. The cost of an expedition of this nature would be infinitely less than that incidental to ordinary expeditions achieving the same re- sults. The time would be perhaps one hundred times less, the precision FIG. 81. The exploration of Central Africa by dirigible Each circle represents an area actually accessible by an airship, and as all the circles overlap, the possibility of exploring the whole interior of the continent is evident would be superior, and the dangers would be diminished very appre- ciably. So far as concerns the country adjoining the French North African possessions, no places would be missed where it would be possible to establish dirigible depots. This system of working is not only applicable to Africa. The whole of the *'Matto" of South America, the interior of Australia, as well as that of Asia, could be explored in this manner with material results through the co-operation of the interested Governments. Thus it would be possible to complete the " map of the earth," which, indeed, is the least that might be done, inasmuch as the photographic map of the heavens has been completed. 228 THE CONQUEST OF THE AIR With regard to the North and South Polar Regions, un- doubtedly it will be in this manner, and in this manner only, that we shall be able to learn their geography completely and quickly. We know how slowly explorations are able to pro- ceed after the vessel is left that is to say, in the same manner as one explores a new country. It is only by heroic effort that Polar explorers have made their perilous discoveries. Consequently it will be by dirigible that it will be possible to study the glacial regions, not only in the vain curiosity " to reach the Pole," but to learn scientifically the geography of the axial caps of our terrestrial globe. To have dreamed of this five years ago would have been madness, but in view of the achievements of the present-day airships, it is a feasible possibility. The distance from Spitzbergen, where one could establish a station, to the North Pole, is only 1300 kilometres (720 knots). Thus it is within the limits of dirigibles, when such have been perfected. Likewise, to solve the problem of the complete exploration of Greenland, a station at Uperniwick would be adequate; for the Arctic archipelago of North America a station on Hudson Bay would permit the aerial exploration of almost its entire area. Let us point out that in the Polar regions, in the time of the solar summer, the day is continuous. Therefore, the bal- loon, would not be subjected to variation in its ascensional effort, and would have no need to descend, so that photo- graphy would be possible throughout the journey. Condi- tions for safety on the voyage among these deserts of ice, destitute of all resources, would only demand the use of several airships, following one another at some distance, and capable of extending mutual assistance in case of necessity. So far as the Antarctic is concerned, its exploration would be more difficult, owing to the extent of its surface, and, above all, the remoteness of its shores from civilisation. It would be necessary to establish special stations, and the " raids " that would have to be carried out by the airships would have to exceed 2000 or 2500 kilometres outward, as well as return. Undoubtedly, therefore, this will be the last part of the terrestrial globe that will be made known in regard to geographical details. A clever Austrian officer, Captain Scheimpflug, has ventured FUTURE OF AERIAL NAVIGATION 229 into the realm of practice, and by the aid of an apparatus comprising several photographic cameras inclined towards the horizon, and grouped in the form of a star ahout a central vertical chamber, has secured some magnificent topographical maps on the scale of -35000* The aerial exploration of unknown continents is quite pos- sible by means of dirigibles. I do not overlook the practical difficulties that stand in the way of realising the theoretical. It is essential to study climatic conditions, winds, and other factors incidental to particular tropical countries. But these difficulties can be overcome, and the aero-photographic exploration of the earth will be made, because it is imperative that such should be effected. We live in a hustling century, and our geographer will not tolerate the remissness in exploring the surface of our globe much longer. So far as aeroplanes are concerned, I do not think that they will take part in geographical exploration so long as they are not provided with sustaining screws to permit them to remain stationary in the air. In their present form the impossibility of " stopping " prevents recourse to photo-topography therefrom. But they will be valuable auxiliaries in the sense that by rapid reconnaissances made at high speeds, they will be able to indicate the most interesting points of which it will be useful to have a detailed map, and upon which the dirigibles, after their indication, can be engaged. There is one other application of dirigibles and aeroplanes. This sphere in which their use will be extended, is the necessity to learn, by careful study, the laws of atmospheric circulation in the highest and middle altitudes. As a matter of fact we scarcely know anything about the laws of this movement in the immediate neighbourhood of the earth, and but for the work of the Prince of Monaco upon the ocean, and those of M. Teisserenc de Bort by means of kites, France would be very much behind other nations in this respect. If it is desired that aerial navigation should develop as it ought, the further exploration of the higher atmosphere is urgent. The increased knowledge that we can acquire in this way will be completed, if not exclusively furnished, by savants travelling in dirigibles and aeroplanes. 230 THE CONQUEST OF THE AIR THE INDUSTRIAL MOVEMENT CREATED BY AERIAL NAVIGATION Not one of the least benefits to locomotion through the air is the creation in a few months, as if by the wave of a magic wand, of a new industry, and the development of a consider- able commercial movement the significance of which it is impossible to indicate. In the first place the generous initiative of M. Henry Deutsch speedily found many imitators. There are several thousands of pounds offered as prizes for aviation in France alone. The Osiris legacy endowed French aeronautics by 4000, which the Academie des Sciences divided between the constructors, Bleriot and Voisin. Through the generous and active initiative of M. Barthou, Minister of Public Works, whose brother, M. Leon Barthou, Vice-President of L'Aero Club de France and an audacious militant aeronaut, the public purse has voted a subvention of 4000 to aerial navigation. Let us add the prizes won already and the total becomes imposing. Yet that is only for " encouragement " ! May we see a little of the amount effectively disbursed. The French have at the present time several dirigibles Lebaudy, Nancy, Ville de Pan, and Ville d* Paris ; the Patrie and the Rtpublique were destroyed by accidents, but they have been replaced. There are also the Libtrte, Colonel JRenard, the Lieutenant CJiaurt, the Captain Marshal, &c. In addition to these there are the Bayard-CUment, Ville de Bordeaux, Zodiac, Belgique, and Eussie (built in French workshops), &c. That totals in all twenty important dirigibles built in four years. When one recollects that each costs on the average 12,000, that represents 240,000 ; but it is more than 240,000 if one takes into account the sheds and the money expended upon experi- ments. I do not take into consideration the numerous efforts of MM. Santos-Dumont and Comte de la Vaulx; of the attempts of MM. Malecot, Mar^ay, and others. By adding all together one obtains for this period of infancy and experiments an aggregate well over 600,000. This is an economic aspect of the question that one must not overlook, especially if one reflects that we are yet only in the early stages. 94 K a < u h3 &4 w o B5 fc fn O g * SB :S II Is W Is cc * i 5- s 2 b * FUTURE OF AERIAL NAVIGATION 231 And aeroplanes! It is by the hundred that one counts their construction now. The money expended upon an aviation apparatus is less than for an airship, that is certain, but it is precisely for this reason that a very large number of persons are participating therein, and it is by hundreds that it is necessary to enumerate them at this moment. If one admits that each, including the trials, v represents an outlay of 800 (and we underrate the truth), we thus arrive, under this head, at many thousands of pounds. And here the development has been more rapid since the true experiments in aviation do not date back more than eighteen months. If one keeps account, moreover, of the money expended in fruitless experiments, in repairs, in expenses of all kinds, the balance-sheet of aerial navigation, both dirigibles and aeroplanes, shows a money movement of more than 2,000,000 during the past five years. That is excellent for a start. And this is only in France. The whole world knows what enormous sums Germany has expended upon its military dirigibles : it exceeds 30,000,000 marks already. In England, the United States and Italy the movement is equally important. Aerial locomotion has given birth to an industry which appears likely to undergo a tremendous expansion. This industry creates a financial reflex because in France alone numerous limited companies have been established, representing a total capital of over 800,000. There are many others, also very important, abroad. The Bourse has become entangled because, rightly or wrongly, speculations have already taken place in these new stocks. Moreover, owing to the incredibly rapid development of aerial navigation in its two forms, the civilised nations are preoccupied in a grave question "international legislation" over the air. Upon the invitation of the French Government, which sent a detailed "note" to the different Powers, an ''International Conference," as we have mentioned, was held at the Foreign Office in Paris on May 1 8, 19 10. Aerial navigation figures consequently in the "European Concert." May the heavens never be the cause of strife. 232 THE CONQUEST OF THE AIR WHAT REMAINS TO BE DONE? Now what progress remains to be accomplished in order that aerial locomotion may maintain its excellent prospects for the future and hi order that new conquests may justify the enthusiasm provoked by its glorious dbut ? In connection with dirigibles the first condition will be to obtain at once a speed of 60 kilometres per hour at least, so as to reduce to twelve or fifteen days per year the period of compulsory idleness. Then it will be necessary to increase their volume so as to increase the fuel- carrying facilities for participation on lengthy voyages ; in a word their radius of action must be extended to 1000 or 1200 kilometres. I consider this indispensable. Also it will be available for armies and exploring expeditions, as we have mentioned. But as the possibility of any accident to the motor must be prevented, it will be necessary to equip them with two independent engines and two propellers. Thereby the failure of one engine will not bring about disablement, or compel landing at some place where an accident may result. The balloon fabrics will be perfected still more, and will enable an airship to remain inflated for fifteen, twenty, or thirty days without taking another charge of gas. Certainly their construction will be improved, and one will learn the best means to avoid the cause of that '* fermentation " of the rubber which is incorporated therein, and which may render the dirigible's envelope useless. But one thing which will be requisite, in fact imperative, will be the construction of numerous sheds, landing stations and shelters. By this means, and by this means only, will the airship be able to render great service, not only in France, but in the colonies. With regard to aviation apparatus much remains to be accom- plished. At first it will be necessary to increase their security to a great extent, and to assure automatically their lateral equilibrium. We have seen that it is compulsory to increase their speed up to 150 or 200 kilometres per hour, velocities which we shall witness soon without a doubt. And at the same time it will be necessary to reduce the dangers of shocks at FUTURE OF AERIAL NAVIGATION 233 landing, dangers which will increase in proportion as the supporting surface will be diminished, because of the progressive increase of the speed of the aerial vehicle. It will be essential, more so than in balloons, to equip aeroplanes with two independent motors, each of which alone will suffice to assure sustentation and propulsion. In this manner only will it be possible to reduce to the minimum the risks of an aerial journey. The number of the devices for steering and control of the motor must be restrained to the minimum, so that the pilot has less to do. The facilities for accommodating passengers will have to be improved ; it will be necessary to increase the radius of action, which now scarcely equals two or three hours' actual travelling at 80 kilometres per hour; special safety arrangements for cases where the aeroplane will have to descend upon a lake, a river, or the sea must be provided. It may be said, generally speaking, that future progressive development is associated with the light explosion motor. It is not necessary to carry the latter to an extreme degree if durability is desired that is to say, if embarkation upon long journeys is in view. Greater lightness may be abandoned, effort devoted towards a type similar to the excellent auto- mobile engines which now are so perfect, so reliable and constant in operation. The recent exploits of Farman and Sommer flying with two and three passengers show that without abandoning the existing type of aeroplane it is possible to use heavier motors which, as a result, are stronger. Then I believe that aviation will record greater advance and become possible of making voyages of longer duration than hitherto. All serious accidents have been caused more or less by defects in the motors. It will be necessary particularly to improve carburation to the maximum degree, and to use petrol only of a known composition, exceedingly pure, and exempt from the least trace of water. It is equally vital, in order to secure the perfect running of an engine upon which their lives depend, for aviators to be extremely careful, even " fussy," like Count Lambert, for instance, and to filter their petrol themselves, not only in order to remove solid impurities, but to make sure there is not the smallest drop of water associated therewith. 234 THE CONQUEST OF THE AIR And above and before all, the necessity of launching from level ground must be suppressed, since such may be unavail- able, as, for instance, in a mountainous or forest country. If this obligation be persisted in, it will be a serious obstacle against the general application of aviation. This is the goal to. which the efforts of the investigators must be directed now. Flying machines must be able to " rise from the spot " ; then they will have an immense future, and maybe we shall see aeroplane-liners ploughing the air with numerous passengers, whereas as yet we have only aeroplane birds. Possibly this development will be the first-fruits of that " aeronautical institute," for the foundation of which M. H. Deutsch offered a million francs to the Universite de Paris, at the same time as M. Zaharoff gave 28,000 to found there a chair of aviation, Now we arrive at the last lines of this volume. In writing it I have not been able to defend myself from a feeling of " human " pride, which I am sure the reader will share. As a matter of fact, is it not magnificent to think that man, so insignificant in Nature, so feeble in comparison with the forces of the universe, even so weak in reference to many of the living species, has been able, thanks to the inspiring effort of his brain, to tame the elements, to conquer them, and to become their master ? That domain of the air, which seemed prohibited to him, he has penetrated, soon will govern it as he holds sway upon the earth, as he prevails upon and under the waters 1 Certainly the history of all his conquests is magnifi- cent, but I think that undoubtedly the most fascinating is that which we have described. It is that by which man has at last freed himself from servitude upon terrestrial soil. He has broken the fetters that the laws of balanced weight imposed upon him by the speed of his machines, and now, henceforward free of all shackles, he will be able to dash without hindrance along the " Highway of the Air." APPENDIX SOMS of our readers perhaps will be desirous to learn in a more precise form the laws concerning the resistance of the air. For such we set forth in the following lines the essential formulae for aeronautics and aviation. (A) RESISTANCE OF THE Am. In the case of a surface of which the plane stands perpendicular to the direction of displacement, the resistance of the air is given by the relation (1) R in which S is the moving surface, expressed in square metres, V the velocity of displacement in metres per second, R the resistance in kilo- grammes and a numerical co-efficient of which the value is only known with doubtful certainty (it varies according to the experimenters, between 0*08 and O16. Marine engineers for calculations concerning the propulsion of vessels by the wind take the number O125, the result of very ancient practice. Still the numbep 0-08 is the mean of more recent investigations by Le Dantec, Eenard, Eiffel, Cailletet, and Colardeau). The formula (1) corresponds to the case of Fig. 1. (B) RESISTANCE OF THE AIR UPON AN OBLIQUE SUKFACE. This is the case of the theoretical aeroplane, corresponding to Fig. 44, in which we designate by i the angle of the surface of the aeroplane with the direction of movement (angle of attack). The thrust P moving against the oblique surface is expressed (2) p-fsvyw; f(i\ being an action of the angle i. This action is simple and must be of the form f(i) = \ sin i. With regard to the value of A, it is given by formulae which differ according to the savants who have enunciated them. Here are the three which are the most used : 2 (3) X = l + sin 2 i (Colonel Duchemin) (4) X = a - (a - 1) sin 2 i (Colonel Renard) in which a is a number between 1 and 2 and more in the neighbour- hood of 2 ; 235 236 APPENDIX and lastly, l-mtgi formula in which m is the ratio, .. , if one calls 21 the spread of the surface and 2A its dimension in the direction of travel; m con- sequently depends upon the elongation of the surface as well as X. At all events X varies with the angle i. Let us call X its mean value and let us admit : we have then for expression of the normal thrust bearing upon a flat plane, in the case of an angle of attack small enough to draw it without confounding the arc with its sine : (6) P the angle i was expressed in the function of the radius. N.B. Many'authors often confound K and ^>; it is important to avoid this confusion. (C) Position of the CENTRE OF PRESSURE [or centre of thrust). In reverting to Fig. 48 which graphically expresses as the result of experiment that the centre of thrust is drawn more to the front edge of the moving surface, one has to calculate the distance d between this centre and the centre of the diagram of the moving rectangle, by the formula conceived by the engineer M. Soreau. (7) <* = 2h being the dimension of the rectangle in the direction of travel. Avanzini's formula, a little simpler, is the following : (8] d = 0'6 h(l -smi] (D) M. BERGET'S SPEED FORMULA FOR DIRIGIBLE BALLOONS. ThisJ formula is (9) iifi- Vs in which V is the speed in myriametres per hour, F the engine effort in horse-power, S the surface of the maximum transversal section in square metres, and C the co-efficient of advantage of the airship (see Table on page 94). (E) MEASURING THE SPEED OF AERIAL VEHICLES. This operation, indispensable to aeronauts, and which will be to aviators also as soon APPENDIX 237 as they can undertake voyages of some duration, is simply effected by means of the apparatus of the engineer Joanneton of which front and back views are shown in Plate XXI. The apparatus is a copper quadrant one face of which carries an engraved " table " over which moves a rule. This rule indicates by the aid of \ -ratio gearing, the part of the angle at which turns a mirror with which it is solid and which projects from the back face. The aeronaut by the aid of a small telescope sees in this mirror the image of some arbitrarily chosen point upon the ground (a tree, steeple, building or what not), and follows this object for one minute while turning the mirror in such a manner that the image always rests in the field of the telescope. There is nothing more to do than look upon the " table," to see the intersection of the rule with the line of altitude shown by the barometer; the abscissa of the corresponding point indicated upon the horizontal edge of the quadrant gives the speed in kilometres per hour. The apparatus, weighing about one kilogramme, owing to its weight hangs like a plumb-bob in the desired position : it is sufficient to hang it up by a cord and a ring to the suspension ring of the car. GLOSSARY OF FRENCH AERONAUTICAL WORDS ANGLICISED BY THE TECHNICAL WORDS COMMITTEE OF THE AERONAUTICAL SOCIETY OF GREAT BRITAIN PRELIMINARY REPORT IN view of the somewhat confused state of aeronautical terminology at present prevailing, a Technical Words Committee was appointed by the Aeronautical Society of Great Britain to draft a list of technical terms relating to aeronautics, and to define their meaning. The work of the Committee has proceeded along systematic lines, and has already resulted in the compilation of a glossary of the more general terms in use. It was decided, therefore, to issue this list forthwith, in the form of a Preliminary Report, as it covers fairly well the technical vocabulary involved in the ordinary course of aeronautical work. In due course, the Committee hope to issue a glossary covering the whole range of aeronautical terminology, but the work of selection and definition is necessarily slow when conscientiously undertaken. The Committee wish to draw attention to the fact that they have aimed at making their definitions of technical terms as simple and commonplace as possible. The definition of ordinary dictionary words that are sometimes used technically has, as far as possible, been avoided, in order to give that latitude of expression so much desired by all writers. In a few cases where certain words are used in contrary senses by different schools of writers such as "aerodrome" and " airship" the Committee have been forced to take arbitrary action ; it is particularly in respect to the use of such words that the Committee hope to meet with support. GENERAL TERMS AERONAUTICS The entire science of aerial navigation. AEROSTATICS The science of buoyancy in air by means of displacement ; this is, therefore, the term to be applied to the science of aerostation. AERODYNAMICS The science relating to the effects produced by air in motion ; this is, therefore, the term to be applied to the science of aviation. AEROSTATION That part of aerial navigation dealing with gas-borne -im^or " lighter-than-air " machines. AVIATION That part of aerial navigation dealing with dynamically- raised or " heavier-than-air " machines, 238 GLOSSARY 239 AERONAUT One who practises any branch of aerial navigation, AVIATOR One who practises aviation. PILOT An aeronaut qualified in aerial navigation. ENGINEER In charge of the power plant. HELMSMAN In charge of the steering. SHED The use of the term shed is recommended instead of hangar* HARBOUR A natural or artificial shelter. AERODROME A ground set apart for flying purposes. The Committee do not recommend this term, but, in view of its somewhat general use, suggest that it should be employed only in the above sense. This suggestion is made without prejudice either to its derivation or to its application in another sense by authors such as Langley, Lanchester, and Graham Bell. DIRIGIBLE A power-driven balloon. AIRSHIP This term having occasionally been used to denote aeroplcme, the Committee recommend its use only in the sense of dirigible in order to avoid confusion. HELICOPTER A flying-machine supported by ooe or more screw pro- pellers rotating on vertical or approximately vertical shafts. ORNITHOPTER A " flapping-wing " machine. FLYING-MACHINE A generic term denoting machines used in aviation, as distinct from those employed in aerostation. AEROPLANE A flying-machine provided with fixed planes supported dynamically by its movement through the air. This term should not be used to denote the planes them- selves, but should only apply to the whole machine. GLIDER An aeroplane unprovided with motive power. MULTIPLANE An aeroplane with two or more main planes overlapping in plan form. BIPLANE An aeroplane with two superposed main planes overlapping in plan-form, MONOPLANE An aeroplane with a single main supporting plane, which may consist of a pair of wings outstretched on either side of a central body. TANDEM, STEPPED In some cases aeroplanes have more than one pair of wingSj which may or may not be on the same level ; such planes, if they do not overlap in plan-form, must necessarily be arranged in " tandem " ; when not on the same level they are said to be " stepped." For instance, "an aeroplane having three pairs of wings stepped in tandem." PRINCIPAL DIMENSIONS AREA This term is not a technical definition unless qualified by an adjective, as, for instance, " supporting " or " effective " area, By area is meant, in the case of planes, the area of the plan-form, and is therefore measured in units of double surface. That is to say, both sides or surfaces are counted as one unit of area. Thus, by an area of 500 square feet is implied a surface of twice 500 square feet. 240 GLOSSARY SURFACE Attention is drawn to the distinction that exists between surface and area. See AREA. WEIGHT This being a general term, should only be used when qualified by an adjective, such as " net weight." NET WEIGHT The weight of the complete machine exclusive of variable quantities, such as pilot, fuel, lubricants, &c. GROSS WEIGHT The weight of the complete machine inclusive of all variable quantities, i.e., pilot, fuel, lubricants, &c. LOADING The loading of a machine is its gross weight in pounds divided by the supporting area in square feet. PRINCIPAL PARTS PLANE Any element of area used for dynamic support or control. In pure aerodynamics the term should only be used with a qualifying adjective such as "flat," "curved," or "cambered," The prefix " aero " is restricted to the complete machine defined as an " aeroplane." WING The present use of this term, by analogy with natural flight, denotes each of a pair of planes outstretched on either side of a central body, which wings, if continuous, would form a single plane. BODY In flying-machines, the central longitudinal framework to which the planes and organs of control and propulsion are attached. CARRIAGE That part of the machine beneath the body intended for its support on land or water. TAIL In flying-machines, a plane or group of subsidiary planes, which may include both horizontal and vertical planes, behind the main planes. ELEVATOR A movable plane or group of planes for directing and controlling the machine vertically. RUDDER A plane or group of planes for guiding a machine to right or left. BALANCER In aeroplanes, an organ usually a plane for maintaining lateral equilibrium. Published by kind permission of the Aeronautical Society of Great Britain. METRICAL MEASUREMENTS AND THEIR CUSTOMARY ENGLISH EQUIVALENTS LENGTH 1 millimetre = -03937 inch 1 centimetre =0*3937 1 metre = ft?* 7 . in ,. ches ^o*.o teet 1 kilometre = 0' 62 137 miles AREA 1 sq. millimetre = '00155 sq. inch 1 centimetre = '1550 1,, metre -fiS^"*** U'196 yards VOLUME 1 cubic millimetre = '000061 cubic inch 1 centimetre = '0610 1 metre /35-314 feet = \1-3079 yards CAPACITY (liquid) 1 litre - f 1 ' 05668 ~ \-26417 gallons MASS (avoirdupois) 1 gram = '03527 ounces 1 kilogram = 2-20462 pounds 241 INDEX ABOUKAYA, Miss, 206 Academie aeronautique de France, 208 Ader, 194 Aerial League, 207 "Aerial yachts, "60-62 A6ro, 1', 208 aviation, 1', 208 club de Belgique, 208 club de France, 208 -Mechanique, 1', 208 The Stella, 208 Aeronaute, F, 208 Aeronautique-club, 208 ASrophile, 1% 208 Aeroplanes, 101-3, 127-212, 213-5, 217, 218-21, 229-231, 232-4 accidents in, 133, 160, 211, 212 angle of attack, 107-110 Antoinette, 114, 123, 128, 166,178-82, 201 body of, 134-5, 156-8 Avion, 194 biplanes, 151-167 Bleriot, 114, 118, 123, 134, 162, 168- 73, 185, 198, 199, 201, 205, 212 centre of gravity, 107-110 centre of thrust, 107-10 carrying surfaces, 127-8 construction, 127-150 construction of wings, 127-8 descent of, 125-6 elevator, 122-3 equilibrium of, 105-6 fall of, 125-126 Farman, Henri, 114, 119, 134, 135, 151, 155, 165,1166, 184, 187, 198, 199, 202, 203, 205, 207, 211 Maurice, 163-4, 211 Aeroplanes, Gastamlide-mengin, 178 landing shores, 156, 180 launching, 123-5. 160-1, 181 launching-rail (Wright), 160-1 Maxim, 193 monoplanes. 113-15, 168-90 motors, 129-131 (see Motors) partitioning of, 119-20, 185 propellers, 131-34 rudder, 115-7,122-3, 147-50, 152, 158-60, 163, 165, 168-71, 173, 178-81, 189 Santos-DumonV s "Demoiselle," 182 safety, 139-44 self-starting, 152-54, 201 speed of, 135-137 stabilisation empennage, 107-110 stability, lateral, 115-122 Tellier, 182, 183, 204 turning of, 115-17 warping wings of, 117-18, 155-60, 163-4, 173, 174, 183 Wenham, 193 wind and, 137-144 wings, 111-12, 127-8 Wright Brothers, 112, 114, 117, 118, 123, 124, 132, 133, 134, 155-62, 184-7, 194, 195, 198, 203, 204, 205 Ailerons, 117-120 Antoinette, 179 Bleriot, 168-9 Air, atmospheric density of, 2 ballonnet, 20-22, 66, 69, 70, 76 co-efficient formula ^of resistance, 11, 235-6 Conquete de 1', 208 resistance of, 10-34, 107-10 ] 243 244 INDEX Air, transport, 213-5, 218-21, 223-29 vagaries of, 42-5, 137-44 weight of, 2 Airship : accidents, 53, 209-11 advantage of large capacity, 14-16 altitude stability, 22-24 applications to civil life, 218-21 ascensional effort, 2 Belgique. 91, 230 car, 3, 50-51, 72 Capazza's lenticular, 147-50 Clement-Bayard, 15, 23, 32, 34, 44, 47, 53, 58-60, 64, 72, 82, 90, 132, 164, 203, 215, 217, 226, 230 co-efficient of advantage, 92-5 Colonel Renard, 230 Comte de la Vaulx, 34, 62, 63, 230 construction, 46-54 cost of, 60, 62, 230 critical speed, 29-34 Dupuy de Lome's, 12, 20, 70-1 elevators, 23-4 envelope, 2, 3, 46-8, 232 empennage, 29-32 equilibrium conditions, 17-32 dynamic, 19-20 exploration by, 221-9 Flandre, la, 91 France, la, 30, 31, 72-4, 78, 94, 95, 123, 156, 215 gas, 2 General Meusnier's, 20, 65-8, 70 German, 4, 13, 87-90, 209, 231 Giffard's, 6, 12, 34, 68-70, 131 Gross, 87, 89, 215 handling of, 54-8 improvements to be effected in, 95-6 independent speed, 38, 45, 196, 232 industry, 230 Lebaudy, 32, 34, 76-8, 94, 132, 215, 230 Uberte, 80, 230 longitudinal stability, 24-32 military applications, 215-218 "mooring " arrangement for, 57-8 motors, 5, 50-1 Nulli Secundus, 90 Airship, Parswal, 87, 89 Patrie, la, 32, 34, 37, 57, 78, 82, 87, 94, 95, 215, 230 propellers, 32-34, 52-4, 87, 164,167, 202 "radius of action," 16-7, 224-5,232 R6publi%ue t la, 44, 53, 62, 79, 80, 94, 95, 210-211, 230 rigging, 3, 33 rudders, 4-6, 24-8, 50-1 Russie, 234 safety, 62-4 Santos-Dumont, 76, 94 scientific applications, 221-9 shape of, 12-14, 29 stability of direction, 24, 28 the envelope and outline, 46-7, 92-5 Tissandier's, 12, 34, 71 Ville-de- Bordeaux, 82, 230 Ville-de-Paris, 32, 34, 44, 72, 82, 132, 215, 230 weighing, 55 wind and, 35-45 Zeppelin, 15, 21-22, 26, 32, 57, 60, 82, 84, 85, 86, 87, 88, 89, 90, 94, 95, 209, 211, 215, 219 Zodiac, 60-2, 80, 215, 230 Albert Lake, 225 Alps, crossing of, 141, 203 Angle, approachable, 38-42 of attack, 107-110 Antoinette aeroplane, 114, 123, 128, 166, 178-182, 201 motors, 153, 171, 181 Appendix, 235-241 aeronautical and aviation air re- sistance formulae, 235-6 dirigible speedometer, 236-7 glossary of aero terms, 238-40 metric and English measurements, 241 Application of propelling force in an airship, point of, 32-34 Archdeacon, 197-8 Archimedes, principle of, 1, 4 Armengaud, 197 Ascensional effort, 2-3 Aubrun, 201 INDEX 245 Auvours camp, 161, 196, 203, 205 Aviation, 97 clubs, 208 illustre, 208 meetings, 205-8 motors, 129-31 Avion, 194 1' (journal), 208 BABINET, 144 Bagatelle, 198 Ballast, 3, 262 Ballonnet, air, 20-22 Balloon, advantage of large volume of, 14-16 dizziness in, 62-4 lenticular, 147-50 Montgolfier, 9, 20, 65 supension parallel, deformable, 47-8 triangular, indeforinable, 47-8 weighing, 55 Balsan, 207 Barthou, Leon, 230 Louis, 230 Belgique, 91, 230 Berget, A., formula of, 92-5, 235-6 Besancon, Georges, 208 Bicycle, comparison of French aero- planes with, 186-7 Birds, 97 flight, 97-101 wings, 111 Bleriot, L., 114, 118, 123, 134, 162, 168-173, 198, 199-201, 205, 212 Bradsky, de, 63, 76, 209-210 Breguet, Louis, 166-7, 189-90 Blon (le), 207, 212 Brescia meeting, 206 Bris (le), 104, 193 CAILLETET, 208, 235 Caldera, 160 Capazza, 59, 60, 63, 147-150, 203, 217 Car, 3 construction of, 50-1 Cayley, Sir George, 191-2 Centre of gravity, 17-20, 107-110 of thrust, 18-20, 107-110 Chalais-Meudon, 43, 72, 73, 145, 193' 210 Chalons Camp, 181, 184, 186, 217 Channel, flight over, 166, 173, 201 Chanute, 162, 195 Chauviere, 53, 164 propeller, 164, 167, 202 Chavez, 141, 203, 212, 217 Circuit de 1'Bst (le), 205, 216 Civil life, applications to, 218-21 Clement, M., 32, 59, 82 -Bayard, dirigible see Airship Clerget, 62 Co-efficient formula^ of air resistance, 10, 11, 235-6 of advantage, 92-95, 235-6 Colardeau, 235 Comparison of aerial with marine navigation, 89 Conditions of equilibrium, 17-82 Conference, International Diplomatic, Aerial Navigation, 220, 231 Conquete de 1'air, 208 Construction of airship, 46-54 of aeroplane, 127-35 Cornu, 187-189 Critical speed, 30, 32 Curtiss, H. Glen, 203, 207 Cylindrical shapes, 12-14 " DAILY MAIL " prize*, 166, 173, 201, 202, 207 Deformation of envelope, 24-28 Delagrange, 114, 151, 155, 198, 203, 212 Delaroche, Madame, 206 Demanest, 181 Demoiselle, Santos Dumont's, 182 Descent, airship, 54-8 aeroplane, 125-6 Deutsch de la Meurthe, Henry, 32, 74, 75, 80, 230, 234 -Archdeacon prize, 198, 230 Deutschland, the, 85-6, 209, 219 Deviation, 32-4 Dirigible speedometer, 236-7 Dizziness in airship, 62-4 Domodossola, 203 246 INDEX Dubonnet (M. E.), 183, 204 Duchemin, 235 Dupuy de Lome, 12, 20, 34, 70,71, 131 Dutrieu, Mile., 203, 206 Duray, 207 EFIMOPF, 207 Eiffel, 235 Elevators, 22-24 Empennage, 29-32, 109, 110 Enrico, 193 Envelope, 3-4 profile of, 46 Equilibrium, dynamic, of dirigibles, 29-32 Esnault-Pelterie, 114, 123, 129, 174- 178 aeroplane, 174-178 motor, 173 Explorations, aeronautical, 221-229 elevator see Airships and Aero- planes FARMAN, Henri, 114, 119, 134, 135, 151, 155, 165, 166, 184, 187, 198, 199, 202, 203, 205, 207, 211 Maurice, 163-4, 211 Ferber, Captain, 105, 112, 195, 196 211 Fernandez, 212 Fish, floating, 1-2 natatory gland, 2 Flandre, la, 91 Flight, bird, 98 flapping, 98 sailing, 99 soaring, 98 " wheeling," 100 Flying weeks, 205, 206-7 prizes won at, 206-7 Fodor, engineer, 130 Fordyce, 196 Formula, Berget's dirigible, 94, 236 Formulae, aeronautical, 235-6 , France, la, 30, 31, 72-4, 78, 94, 95, 123, 156, 215 "Fringe" correcting, 110 Fusiform shape, 12-14 92-95 GASTAMBIDE, 114 -Mengin aeroplane, 178 Geography, application to, 221-9 Germany, 4, 13, 87-90, 209, 231 aerial fleet, 88-89 Giffard, Henry, 6, 12, 34, 68-70, 131 Girth suspension, 48, 67 Glossary of aeronautical terms, 238- 240 Gnome motor, 129, 165, 202 Godard. 91 Gravity, centre of, 109 Gross military airship, 87, 89, 215 Gyroplane, Breguet, 166-167, 189-90 Gyroscope, 54, 120-121 HARGREAVES, 104, 114 Hault, la, 147, 190 Helicopters, 98, 144-147, 221: automotor, 145 Breguet, 166-167, 189-190 Cornu, 188-189 de la Landelle, 144, 193 Leger, 146, 187 Ponton d'Amecourt, 144, 193 Kenard's composite, 145-146 screws, 144 Henson, 192 Horse-power, 7-8 -hour, 7 hour, weight, per, 7 weight per, 7 Hureau de Villeneuve, 145 Hydrogen, 2, 3 specific weight, 2 German, works, 89 INDUSTRY, aeronautical, 230-231 Instruments, dirigible guiding, 55, 236-237 Italian dirigibles, 90-91 JACOBS, F., 208 Jaune le, 77 Joanneton, 236-37 Journal, Nicholson's, 191 Julliot, 34, 76 INDEX 247 KAPFEREB, 60, 63 Kinet, Daniel, 166, 203, 212 Kinet, 212 Kites, 101-5, 113-4 cellular, 114 equilibrium, 101-3 Hargreaves, 104, 114 military, 104 multiple, 113 Krebs, 72-4 LA HAULT, 147, 190 Lambert, Count, 160, 162, 204, 233 Landelle, de la, 144, 193 Langley, 193 Latham, 134, 141, 166, 181, 201, 202, 204, 206, 207, 217 Launching an aeroplane, 123-125, 234 Laussgdat, Col., 223, 225-6 League, aerial, 208 Lebaudy, 46, 75, 78, 90 airship, 32, 34, 76-78, 94, 132, 215, 230 Le Bris, 104, 193 LeCornu, M., 188-9 Leger Helicopter, 146, 187 Lenticular balloon, 147-150 LiberU, 80, 230 Lifting ropes, 48 Lilienthal, Otto, 194-5,211 London-Manchester flight, 165, 166, 202 Los Angeles, 166, 203 MALECOT, 230 Manoeuvring a dirigible, 54-58 Marcay, de, 230 Marchal, Capt., 79, 210, 230 Martyrs of aerial navigation, 208-212 Maxim, Sir Hiram, 193 Metric-English measurements, 241 Meusnier, General, airship, 20, 65-8, 70 Military applications, 215-8 Monaco, Prince of, 80, 104, 146, 229 Monocycle, comparison of Wright aeroplane with, 186-7 Monoplane, 113-5, 168-190 ailerons, 166, 167, 173, 178 Antoinette, 114, 123, 125, 166, 178- 82, 201 Bleriot, 114, 118, 123, 134, 162, 168- 73, 185, 198, 199, 201, 205, 212 Esnault-Pelterie, 174-8 Gastambide, 178 Santos- Dumont's " Demoiselle," 182-3 Tatin, 193 1 Tellier, 182, 183, 204 Montgolfier, 9, 20, 65 " Mooring" arrangement for dirigibles, 57, 58 Morane, 141, 203, 217 Morning Post airship, 90 Motors, 5, 50-1, 129-131 Antoinette, 153, 171, 181 Daimler, 209 Darracq, 182 Electrical, 71, 73 Esnault-Pelterie, 173 explosion, 6, 7, 74-5, 192 Fodor rotary, 130 Gnome, 129, 165, 202 human, 5, 67, 70, 101 Mercedes, 78 Panhard, 79 Kenault, 164, 167 steam, weight of, 7 I NADAB, 144, 193 Nature (la) Prize, 183 Nice week, 206-207 Nulli Secundus, 90 OLIESLCEGEBS, 141, 203 Ornithopters, 97, 98, 147, 190 Adh. de la Hault, 147, 190 American, 190 Osiris Prize, 201, 230 PAINLEVE, 184-&, 196, 207 Parseval, von, 87 military airship, 87, 89 Partitioning, 119-20, 185 248 INDEX Patrie, la, 32, 34, 37, 57, 78, 82, 87, 94, 95, 215, 230 Paulhan, 141, 166, 187, 202, 204, 207 Pax, 26, 32, 33, 63, 209-10 Penaud, 193 Photography from dirigible, 223, 225- 6,229 Picardy manoeuvres, 90, 216, 218 Pisciform shape, 12-14, 128 Point of application of propelling force, 32-4 Ponton d'Amecourt, 144, 193 Post, aerial, 220 Power of penetration, 127-8, 178 Progress to be effected, 232-4 Propellers, 52-54, 67, 70, 78, 79, 84, 87, 131-134, 145, 153, 160, 164, 167, 171, 173, 181, 183, 187-8, 189, 192, 210-211 Pulfrich, Dr., 226 " KADIUS of action," airships, 16-7, 224-5, 232 Kenard, Colonel, 4, 6, 7,12, 13, 28, 29, 30, 31, 37, 38, 47, 52, 72-4, 76, 80, 94, 96, 123, 129, 131, 145, 146, 156, 197, 235 Commander Paul, 72, 117 Kenault, 164, 167 Wpublique, la, 44, 53, 62, 79, 80, 94, 95, 210-1, 230 Resistance of the air, 10-12, 102, 105, 107-110 Kevue, aerienne, la, 208 de i'aviation, 208 Rheims week, 206 Ricaldoni, Captain, 91 Eiemskyck, 207 Rigging, 3-4 Rigid balloons, 28, 104-108 Rose twin airship, 32 Rougier, 119, 151, 207 Rudders, of airships, 4-6, 24-28, 50-51 of aeroplanes, 115-7, 122-3, 147-50 ? 152, 158-60, 163, 165,168-71,173,' 178-81, 189 Ruthemburg airship, 89 SAFETY, airship, 62-4 aeroplane, 139-144 Santos- DumontJM.), 15, 75, 114, 181, 197, 198, 230 aeroplane, 182 airship, 76, 94 Schleimpflug, Capt., 229 Screws (propellers), aeroplane, 131-4, 145, 153, 160, 164, 167, 171, 173, 181, 183, 187-8, 189, 192, 210-1 airship, 52-4, 67, 70, 78, 79, 84, 87 pitch, 52, 53, 131 position of, 32-34, 53-4, 78 slip, 52, 53, 131 speed, 51, 54, 73, 131, 132 sustaining, 144-7, 187-190, 221 Section, transverse of wings, 111-12, 127-8 Selfridge, Lieutenant, 133, 160, 211 Severo d' Albuquerque, 32, 76, 209 Shape, influence of front, 12-14 stern, 13, 14 Shores, landing, 180-1 Skates, landing, 156 Societe francaise de navigation aerienne, 135, 193, 203 Soreau, 99, 111, 135, 136, 191, 196, 208, 236 Speed, critical, 29-32 aeroplane, 96 independent of airships, 38-42, 92-5, 96, 232 regulating, of aeroplanes, 105-6 Stability, airships, altitude, 22-24 direction, 24-25 longitudinal, 25-8, 29 Surcouf, 32, 34, 58, 77, 80, 82 TABLE of wind speeds around Paris, 44 Tatin, 80, 193 Tellier, 182, 183, 204 Thrust, centre of, 107-110 Tissandier, 12, 34, 71 Transport, aerial, 213, 214, 215, 218- 221, 232-4 INDEX 249 UNIVERSITY of Paris, 234 VAGARIES of atmosphere, 42-5, 137- Valve, 19 Eipping, 47 Vaulx, Count de la, 34, 62, 63, 230 Ville-de-Bordeause, 82, 230 Paris, 32, 34, 44, 72, 82, 132, 215, 230 Voisin, 114, 119, 134, 135, 136, 151- 155, 182, 184, 185, 198, 230 Voyages : Bayard- Clement, 58-60 Bleriot, 162, 166, 199-201 Chavez, 203 Farman, Henri, 155, 186, 199, 206 France, la, 72-4 Lebaudy, 78 Lambert, Count, 204 Latham, 181, 187, 201, 202, 206 Patrie, la, 79 Paulhan, 165, 202, 203, 207 Republique, 79 SantoS'Dumont, 76, 182, 198 Sommer, 167, 203 Ville-de-Pari*, 82 Wright Brothers, 162, 196. 20$ Voyages, Zeppelin, 60, S5, 86 Zodiac, 62, 82 WENHAM, 193 Wind, 35-45, 99-101, 137-144 ascending, 139-42 descending, 139-42 direction, 36 pressure, 36-37 relative, 38-42 Telocity, 36-7, 42-45 Wings, birds, 98-101, 112 construction of, 111, 127-8 warping of, 117-8, 155-60, 163-4, 173, 174, 183 Wright Brothers, 112, 114, 117, 118, 123, 124, 132, 133, 134, 155-162, 184-187,194, 195,198, 203,204, 205 launching apparatus, 160-61 YACHTS, aerial, 60-2 ZAHAEOPP, 234 Zeppelin, Count, 13, 22, 82. 132 "airships, 15, 22, 26, 82, 33, 67, 0. 82, 84, 85, 86, 87, 88, 89. 90, 94. 95, 209, 211, 215, 219 Zodiac airship, 60-2. 80, 215, 230 PRINTED BY BALLANTYNE & COMPANY LTD AT THE BALLANTYNE PRESS TAVISTOCK STREET COVKNT GARDEN LONDON UNIVERSITY OF CALIFORNIA LIBRARY BERKELEY Return to desk from which borrowed. This book is DUE on the last date stamped below, REC'D L JUH t3No'53HK U0V 4. ' LD t-tB 101957 17Dec'57AI? LD 21-100m-9,'47(A5702sl6)476 .DLL, 17 i REC'D LD DEC 10 1957 ~ '80 , n ,^ OCT 2 9 1973 M.STACKS i 1 YC 19446 THE UNIVERSITY OF CALIFORNIA LIBRARY