Legend and doubtful history carries up to the fifteenth century, and then came Leonardo da Vinci, first student of flight whose work endures to the present day. The world knows da Vinci as artist; his age knew him as architect, engineer, artist, and scientist16 in an age when science was a single study, comprising all knowledge from mathematics to medicine. He was, of course, in league with the devil, for in no other way could his range of knowledge and observation be explained by his contemporaries; he left a Treatise13 on the Flight of Birds in which are statements and deductions14 that had to be rediscovered when the Treatise had been forgotten—da Vinci anticipated modern knowledge as Plato anticipated modern thought, and blazed the first broad trail toward flight.
One Cuperus, who wrote a Treatise on the Excellence15 of Man, asserted that da Vinci translated his theories into practice, and actually flew, but the statement is unsupported. That he made models, especially on the helicopter principle, is past question; these were made of paper and wire, and actuated by springs of steel wire, which caused them to lift themselves in the air. It is, however, in the theories which he put forward that da Vinci’s investigations16 are of greatest interest; these prove him a patient as well as a keen student of the principles of flight, and show that his manifold activities did not prevent him from devoting some lengthy18 periods to observations of bird flight.
‘A bird,’ he says in his Treatise, ‘is an instrument working according to mathematical law, which instrument it is within the capacity of man to reproduce with all its movements, but not with a corresponding degree of strength, though it is deficient19 only in power of maintaining equilibrium20. We may say, therefore, that such an instrument constructed by man is lacking in nothing except the life of the bird, and this life must needs be supplied from that of man. The life which resides in the bird’s members will, without doubt,17 better conform to their needs than will that of a man which is separated from them, and especially in the almost imperceptible movements which produce equilibrium. But since we see that the bird is equipped for many apparent varieties of movement, we are able from this experience to deduce that the most rudimentary of these movements will be capable of being comprehended by man’s understanding, and that he will to a great extent be able to provide against the destruction of that instrument of which he himself has become the living principle and the propeller21.’
In this is the definite belief of da Vinci that man is capable of flight, together with a far more definite statement of the principles by which flight is to be achieved than any which had preceded it—and for that matter, than many that have succeeded it. Two further extracts from his work will show the exactness of his observations:—
‘When a bird which is in equilibrium throws the centre of resistance of the wings behind the centre of gravity, then such a bird will descend22 with its head downward. This bird which finds itself in equilibrium shall have the centre of resistance of the wings more forward than the bird’s centre of gravity; then such a bird will fall with its tail turned toward the earth.’
And again: ‘A man, when flying, shall be free from the waist up, that he may be able to keep himself in equilibrium as he does in a boat, so that the centre of his gravity and of the instrument may set itself in equilibrium and change when necessity requires it to the changing of the centre of its resistance.’
Here, in this last quotation23, are the first beginnings of the inherent stability which proved so great an18 advance in design, in this twentieth century. But the extracts given do not begin to exhaust the range of da Vinci’s observations and deductions. With regard to bird flight, he observed that so long as a bird keeps its wings outspread it cannot fall directly to earth, but must glide8 down at an angle to alight—a small thing, now that the principle of the plane in opposition24 to the air is generally grasped, but da Vinci had to find it out. From observation he gathered how a bird checks its own speed by opposing tail and wing surface to the direction of flight, and thus alights at the proper ‘landing speed.’ He proved the existence of upward air currents by noting how a bird takes off from level earth with wings outstretched and motionless, and, in order to get an efficient substitute for the natural wing, he recommended that there be used something similar to the membrane25 of the wing of a bat—from this to the doped fabric26 of an aeroplane wing is but a small step, for both are equally impervious27 to air. Again, da Vinci recommended that experiments in flight be conducted at a good height from the ground, since, if equilibrium be lost through any cause, the height gives time to regain28 it. This recommendation, by the way, received ample support in the training areas of war pilots.
Man’s muscles, said da Vinci, are fully29 sufficient to enable him to fly, for the larger birds, he noted30, employ but a small part of their strength in keeping themselves afloat in the air—by this theory he attempted to encourage experiment, just as, when his time came, Borelli reached the opposite conclusion and discouraged it. That Borelli was right—so far—and da Vinci wrong, detracts not at all from the repute of the earlier19 investigator31, who had but the resources of his age to support investigations conducted in the spirit of ages after.
His chief practical contributions to the science of flight—apart from numerous drawings which have still a value—are the helicopter or lifting screw, and the parachute. The former, as already noted, he made and proved effective in model form, and the principle which he demonstrated is that of the helicopter of to-day, on which sundry32 experimenters work spasmodically, in spite of the success of the plane with its driving propeller. As to the parachute, the idea was doubtless inspired by observation of the effect a bird produced by pressure of its wings against the direction of flight.
Da Vinci’s conclusions, and his experiments, were forgotten easily by most of his contemporaries; his Treatise lay forgotten for nearly four centuries, overshadowed, mayhap, by his other work. There was, however, a certain Paolo Guidotti of Lucca, who lived in the latter half of the sixteenth century, and who attempted to carry da Vinci’s theories—one of them, at least, into practice. For this Guidotti, who was by profession an artist and by inclination33 an investigator, made for himself wings, of which the framework was of whalebone; these he covered with feathers, and with them made a number of gliding flights, attaining34 considerable proficiency35. He is said in the end to have made a flight of about four hundred yards, but this attempt at solving the problem ended on a house roof, where Guidotti broke his thigh36 bone. After that, apparently37, he gave up the idea of flight, and went back to painting.
One other, a Venetian architect named Veranzio,20 studied da Vinci’s theory of the parachute, and found it correct, if contemporary records and even pictorial38 presentment are correct. Da Vinci showed his conception of a parachute as a sort of inverted39 square bag; Veranzio modified this to a ‘sort of square sail extended by four rods of equal size and having four cords attached at the corners,’ by means of which ‘a man could without danger throw himself from the top of a tower or any high place. For though at the moment there may be no wind, yet the effort of his falling will carry up the wind, which the sail will hold, by which means he does not fall suddenly but descends40 little by little. The size of the sail should be measured to the man.’ By this last, evidently, Veranzio intended to convey that the sheet must be of such content as would enclose sufficient air to support the weight of the parachutist.
Veranzio made his experiments about 1617–1618, but, naturally, they carried him no farther than the mere descent to earth, and since a descent is merely a descent, it is to be conjectured41 that he soon got tired of dropping from high roofs, and took to designing architecture instead of putting it to such a use. With the end of his experiments the work of da Vinci in relation to flying became neglected for nearly four centuries.
Apart from these two experimenters, there is little to record in the matter either of experiment or study until the seventeenth century. Francis Bacon, it is true, wrote about flying in his Sylva Sylvarum, and mentioned the subject in the New Atlantis, but, except for the insight that he showed even in superficial mention of any specific subject, he does not appear to have made attempt at serious investigation17. ‘Spreading of21 Feathers, thin and close and in great breadth will likewise bear up a great Weight,’ says Francis, ‘being even laid without Tilting42 upon the sides.’ But a lesser43 genius could have told as much, even in that age, and though the great Sir Francis is sometimes adduced as one of the early students of the problems of flight, his writings will not sustain the reputation.
The seventeenth century, however, gives us three names, those of Borelli, Lana, and Robert Hooke, all of which take definite place in the history of flight. Borelli ranks as one of the great figures in the study of aeronautical44 problems, in spite of erroneous deductions through which he arrived at a purely45 negative conclusion with regard to the possibility of human flight.
Borelli was a versatile46 genius. Born in 1608, he was practically contemporary with Francesco Lana, and there is evidence that he either knew or was in correspondence with many prominent members of the Royal Society of Great Britain, more especially with John Collins, Dr Wallis, and Henry Oldenburgh, the then Secretary of the Society. He was author of a long list of scientific essays, two of which only are responsible for his fame, viz., Theorice Medic?arum Planetarum, published in Florence, and the better known posthumous47 De Motu Animalium. The first of these two is an astronomical48 study in which Borelli gives evidence of an instinctive49 knowledge of gravitation, though no definite expression is given of this. The second work, De Motu Animalium, deals with the mechanical action of the limbs of birds and animals and with a theory of the action of the internal organs. A section of the first part of this work, called De Volatu, is a study of bird flight; it is quite independent of Da Vinci’s earlier22 work, which had been forgotten and remained unnoticed until near on the beginning of practical flight.
Marey, in his work, La Machine Animale, credits Borelli with the first correct idea of the mechanism50 of flight. He says: ‘Therefore we must be allowed to render to the genius of Borelli the justice which is due to him, and only claim for ourselves the merit of having furnished the experimental demonstration51 of a truth already suspected.’ In fact, all subsequent studies on this subject concur52 in making Borelli the first investigator who illustrated53 the purely mechanical theory of the action of a bird’s wings.
Borelli’s study is divided into a series of propositions in which he traces the principles of flight, and the mechanical actions of the wings of birds. The most interesting of these are the propositions in which he sets forth54 the method in which birds move their wings during flight and the manner in which the air offers resistance to the stroke of the wing. With regard to the first of these two points he says: ‘When birds in repose55 rest on the earth their wings are folded up close against their flanks, but when wishing to start on their flight they first bend their legs and leap into the air. Whereupon the joints56 of their wings are straightened out to form a straight line at right angles to the lateral57 surface of the breast, so that the two wings, outstretched, are placed, as it were, like the arms of a cross to the body of the bird. Next, since the wings with their feathers attached form almost a plane surface, they are raised slightly above the horizontal, and with a most quick impulse beat down in a direction almost perpendicular58 to the wing-plane, upon the underlying59 air; and to so intense a beat the air, notwithstanding it to be fluid,23 offers resistance, partly by reason of its natural inertia60, which seeks to retain it at rest, and partly because the particles of the air, compressed by the swiftness of the stroke, resist this compression by their elasticity62, just like the hard ground. Hence the whole mass of the bird rebounds63, making a fresh leap through the air; whence it follows that flight is simply a motion composed of successive leaps accomplished64 through the air. And I remark that a wing can easily beat the air in a direction almost perpendicular to its plane surface, although only a single one of the corners of the humerus bone is attached to the scapula, the whole extent of its base remaining free and loose, while the greater transverse feathers are joined to the lateral skin of the thorax. Nevertheless the wing can easily revolve65 about its base like unto a fan. Nor are there lacking tendon ligaments which restrain the feathers and prevent them from opening farther, in the same fashion that sheets hold in the sails of ships. No less admirable is nature’s cunning in unfolding and folding the wings upwards66, for she folds them not laterally67, but by moving upwards edgewise the osseous parts wherein the roots of the feathers are inserted; for thus, without encountering the air’s resistance the upward motion of the wing surface is made as with a sword, hence they can be uplifted with but small force. But thereafter when the wings are twisted by being drawn68 transversely and by the resistance of the air, they are flattened69 as has been declared and will be made manifest hereafter.’
Then with reference to the resistance to the air of the wings he explains: ‘The air when struck offers resistance by its elastic61 virtue70 through which the particles of the air compressed by the wing-beat strive to expand24 again. Through these two causes of resistance the downward beat of the wing is not only opposed, but even caused to recoil71 with a reflex movement; and these two causes of resistance ever increase the more the down stroke of the wing is maintained and accelerated. On the other hand, the impulse of the wing is continuously diminished and weakened by the growing resistance. Hereby the force of the wing and the resistance become balanced; so that, manifestly, the air is beaten by the wing with the same force as the resistance to the stroke.’
He concerns himself also with the most difficult problem that confronts the flying man of to-day, namely, landing effectively, and his remarks on this subject would be instructive even to an air pilot of these days: ‘Now the ways and means by which the speed is slackened at the end of a flight are these. The bird spreads its wings and tail so that their concave surfaces are perpendicular to the direction of motion; in this way, the spreading feathers, like a ship’s sail, strike against the still air, check the speed, and so that most of the impetus72 may be stopped, the wings are flapped quickly and strongly forward, inducing a contrary motion, so that the bird absolutely or very nearly stops.’
At the end of his study Borelli came to a conclusion which militated greatly against experiment with any heavier-than-air apparatus, until well on into the nineteenth century, for having gone thoroughly73 into the subject of bird flight he states distinctly in his last proposition on the subject that ‘It is impossible that men should be able to fly craftily74 by their own strength.’ This statement, of course, remains75 true up to the present day, for no man has yet devised the means by which25 he can raise himself in the air and maintain himself there by mere muscular effort.
From the time of Borelli up to the development of the steam engine it may be said that flight by means of any heavier-than-air apparatus was generally regarded as impossible, and apart from certain deductions which a little experiment would have shown to be doomed76 to failure, this method of flight was not followed up. It is not to be wondered at, when Borelli’s exaggerated estimate of the strength expended77 by birds in proportion to their weight is borne in mind; he alleged78 that the motive79 force in birds’ wings is 10,000 times greater than the resistance of their weight, and with regard to human flight he remarks:—
‘When, therefore, it is asked whether men may be able to fly by their own strength, it must be seen whether the motive power of the pectoral muscles (the strength of which is indicated and measured by their size) is proportionately great, as it is evident that it must exceed the resistance of the weight of the whole human body 10,000 times, together with the weight of enormous wings which should be attached to the arms. And it is clear that the motive power of the pectoral muscles in men is much less than is necessary for flight, for in birds the bulk and weight of the muscles for flapping the wings are not less than a sixth part of the entire weight of the body. Therefore, it would be necessary that the pectoral muscles of a man should weigh more than a sixth part of the entire weight of his body; so also the arms, by flapping with the wings attached, should be able to exert a power 10,000 times greater than the weight of the human body itself. But they are far below such excess, for the aforesaid pectoral26 muscles do not equal a hundredth part of the entire weight of a man. Wherefore either the strength of the muscles ought to be increased or the weight of the human body must be decreased, so that the same proportion obtains in it as exists in birds. Hence it is deducted80 that the Icarian invention is entirely81 mythical82 because impossible, for it is not possible either to increase a man’s pectoral muscles or to diminish the weight of the human body; and whatever apparatus is used, although it is possible to increase the momentum83, the velocity84 or the power employed can never equal the resistance; and therefore wing flapping by the contraction85 of muscles cannot give out enough power to carry up the heavy body of a man.’
It may be said that practically all the conclusions which Borelli reached in his study were negative. Although contemporary with Lana, he perceived the one factor which rendered Lana’s project for flight by means of vacuum globes an impossibility—he saw that no globe could be constructed sufficiently86 light for flight, and at the same time sufficiently strong to withstand the pressure of the outside atmosphere. He does not appear to have made any experiments in flying on his own account, having, as he asserts most definitely, no faith in any invention designed to lift man from the surface of the earth. But his work, from which only the foregoing short quotations87 can be given, is, nevertheless, of indisputable value, for he settled the mechanics of bird flight, and paved the way for those later investigators88 who had, first, the steam engine, and later the internal combustion89 engine—two factors in mechanical flight which would have seemed as impossible to Borelli as would wireless90 telegraphy to a student of27 Napoleonic times. On such foundations as his age afforded Borelli built solidly and well, so that he ranks as one of the greatest—if not actually the greatest—of the investigators into this subject before the age of steam.
The conclusion, that ‘the motive force in birds’ wings is apparently ten thousand times greater than the resistance of their weight,’ is erroneous, of course, but study of the translation from which the foregoing excerpt91 is taken will show that the error detracts very little from the value of the work itself. Borelli sets out very definitely the mechanism of flight, in such fashion that he who runs may read. His reference to ‘the use of a large vessel92,’ etc., concerns the suggestion made by Francesco Lana, who antedated93 Borelli’s publication of De Motu Animalium by some ten years with his suggestion for an ‘aerial ship,’ as he called it. Lana’s mind shows, as regards flight, a more imaginative twist; Borelli dived down into first causes, and reached mathematical conclusions; Lana conceived a theory and upheld it—theoretically, since the manner of his life precluded94 experiment.
Francesco Lana, son of a noble family, was born in 1631; in 1647 he was received as a novice95 into the Society of Jesus at Rome, and remained a pious96 member of the Jesuit society until the end of his life. He was greatly handicapped in his scientific investigations by the vows97 of poverty which the rules of the Order imposed on him. He was more scientist than priest all his life; for two years he held the post of Professor of Mathematics at Ferrara, and up to the time of his death, in 1687, he spent by far the greater part of his time in scientific research. He had the dubious98 advantage of living in28 an age when one man could cover the whole range of science, and this he seems to have done very thoroughly. There survives an immense work of his entitled, Magisterium Natur? et Artis, which embraces the whole field of scientific knowledge as that was developed in the period in which Lana lived. In an earlier work of his, published in Brescia in 1670, appears his famous treatise on the aerial ship, a problem which Lana worked out with thoroughness. He was unable to make practical experiments, and thus failed to perceive the one insuperable drawback to his project—of which more anon.
Only extracts from the translation of Lana’s work can be given here, but sufficient can be given to show fully the means by which he designed to achieve the conquest of the air. He begins by mention of the celebrated99 pigeon of Archytas the Philosopher, and advances one or two theories with regard to the way in which this mechanical bird was constructed, and then he recites, apparently with full belief in it, the fable100 of Regiomontanus and the eagle that he is said to have constructed to accompany Charles V. on his entry into Nuremberg. In fact, Lana starts his work with a study of the pioneers of mechanical flying up to his own time, and then outlines his own devices for the construction of mechanical birds before proceeding101 to detail the construction of the aerial ship. Concerning primary experiments for this he says:—
‘I will, first of all, presuppose that air has weight owing to the vapours and halations which ascend102 from the earth and seas to a height of many miles and surround the whole of our terraqueous globe; and this fact will not be denied by philosophers, even by those who may have but a superficial knowledge, because it can be29 proven by exhausting, if not all, at any rate the greater part of, the air contained in a glass vessel, which, if weighed before and after the air has been exhausted103, will be found materially reduced in weight. Then I found out how much the air weighed in itself in the following manner. I procured104 a large vessel of glass, whose neck could be closed or opened by means of a tap, and holding it open I warmed it over a fire, so that the air inside it becoming rarified, the major part was forced out; then quickly shutting the tap to prevent the re-entry I weighed it; which done, I plunged105 its neck in water, resting the whole of the vessel on the surface of the water, then on opening the tap the water rose in the vessel and filled the greater part of it. I lifted the neck out of the water, released the water contained in the vessel, and measured and weighed its quantity and density106, by which I inferred that a certain quantity of air had come out of the vessel equal in bulk to the quantity of water which had entered to refill the portion abandoned by the air. I again weighed the vessel, after I had first of all well dried it free of all moisture, and found it weighed one ounce more whilst it was full of air than when it was exhausted of the greater part, so that what it weighed more was a quantity of air equal in volume to the water which took its place. The water weighed 640 ounces, so I concluded that the weight of air compared with that of water was 1 to 640—that is to say, as the water which filled the vessel weighed 640 ounces, so the air which filled the same vessel weighed one ounce.’
Having thus detailed107 the method of exhausting air from a vessel, Lana goes on to assume that any large vessel can be entirely exhausted of nearly all the air30 contained therein. Then he takes Euclid’s proposition to the effect that the superficial area of globes increases in the proportion of the square of the diameter, whilst the volume increases in the proportion of the cube of the same diameter, and he considers that if one only constructs the globe of thin metal, of sufficient size, and exhausts the air in the manner that he suggests, such a globe will be so far lighter108 than the surrounding atmosphere that it will not only rise, but will be capable of lifting weights. Here is Lana’s own way of putting it:—
‘But so that it may be enabled to raise heavier weights and to lift men in the air, let us take double the quantity of copper109, 1,232 square feet, equal to 308 lbs. of copper; with this double quantity of copper we could construct a vessel of not only double the capacity, but of four times the capacity of the first, for the reason shown by my fourth supposition. Consequently the air contained in such a vessel will be 718 lbs. 4? ounces, so that if the air be drawn out of the vessel it will be 410 lbs. 4? ounces lighter than the same volume of air, and, consequently, will be enabled to lift three men, or at least two, should they weigh more than eight pesi each. It is thus manifest that the larger the ball or vessel is made, the thicker and more solid can the sheets of copper be made, because, although the weight will increase, the capacity of the vessel will increase to a greater extent and with it the weight of the air therein, so that it will always be capable to lift a heavier weight. From this it can be easily seen how it is possible to construct a machine which, fashioned like unto a ship, will float on the air.’
A suggestion for applying hydrogen gas to Lana’s ‘Aerial Ship.’ Rome, 1784.
With four globes of these dimensions Lana proposed31 to make an aerial ship of the fashion shown in his quaint110 illustration. He is careful to point out a method by which the supporting globes for the aerial ship may be entirely emptied of air; this is to be done by connecting to each globe a tube of copper which is ‘at least a length of 47 modern Roman palmi.’ A small tap is to close this tube at the end nearest the globe, and then vessel and tube are to be filled with water, after which the tube is to be immersed in water and the tap opened, allowing the water to run out of the vessel, while no air enters. The tap is then closed before the lower end of the tube is removed from the water, leaving no air at all in the globe or sphere. Propulsion of this airship was to be accomplished by means of sails, and also by oars111.
Lana antedated the modern propeller, and realised that the air would offer enough resistance to oars or paddle to impart motion to any vessel floating in it and propelled by these means, although he did not realise the amount of pressure on the air which would be necessary to accomplish propulsion. As a matter of fact, he foresaw and provided against practically all the difficulties that would be encountered in the working, as well as the making, of the aerial ship, finally coming up against what his religious training made an insuperable objection. This, again, is best told in his own words:—
‘Other difficulties I do not foresee that could prevail against this invention, save one only, which to me seems the greatest of them all, and that is that God would surely never allow such a machine to be successful, since it would create many disturbances112 in the civil and political governments of mankind.’
He ends by saying that no city would be proof32 against surprise, while the aerial ship could set fire to vessels113 at sea, and destroy houses, fortresses114, and cities by fire balls and bombs. In fact, at the end of his treatise on the subject, he furnishes a pretty complete résumé of the activities of German Zeppelins.
As already noted, Lana himself, owing to his vows of poverty, was unable to do more than put his suggestions on paper, which he did with a thoroughness that has procured him a place among the really great pioneers of flying.
It was nearly 200 years before any attempt was made to realise his project; then, in 1843, M. Marey Monge set out to make the globes and the ship as Lana detailed them. Monge’s experiments cost him the sum of 25,000 francs 75 centimes, which he expended purely from love of scientific investigation. He chose to make his globes of brass115, about .004 in thickness, and weighing 1.465 lbs. to the square yard. Having made his sphere of this metal, he lined it with two thicknesses of tissue paper, varnished116 it with oil, and set to work to empty it of air. This, however, he never achieved, for such metal is incapable117 of sustaining the pressure of the outside air, as Lana, had he had the means to carry out experiments, would have ascertained118. M. Monge’s sphere could never be emptied of air sufficiently to rise from the earth; it ended in the melting-pot, ignominiously119 enough, and all that Monge got from his experiment was the value of the scrap120 metal and the satisfaction of knowing that Lana’s theory could never be translated into practice.
Robert Hooke is less conspicuous121 than either Borelli or Lana; his work, which came into the middle of the seventeenth century, consisted of various experiments33 with regard to flight, from which emerged ‘a Module122, which by the help of Springs and Wings, raised and sustained itself in the air.’ This must be reckoned as the first model flying machine which actually flew, except for da Vinci’s helicopters; Hooke’s model appears to have been of the flapping-wing type—he attempted to copy the motion of birds, but found from study and experiment that human muscles were not sufficient to the task of lifting the human body. For that reason, he says, ‘I applied123 my mind to contrive124 a way to make artificial muscles,’ but in this he was, as he expresses it, ‘frustrated of my expectations.’ Hooke’s claim to fame rests mainly on his successful model; the rest of his work is of too scrappy a nature to rank as a serious contribution to the study of flight.
Contemporary with Hooke was one Allard, who, in France, undertook to emulate125 the Saracen of Constantinople to a certain extent. Allard was a tight-rope dancer who either did or was said to have done short gliding flights—the matter is open to question—and finally stated that he would, at St Germains, fly from the terrace in the king’s presence. He made the attempt, but merely fell, as did the Saracen some centuries before, causing himself serious injury. Allard cannot be regarded as a contributor to the development of aeronautics126 in any way, and is only mentioned as typical of the way in which, up to the time of the Wright brothers, flying was regarded. Even unto this day there are many who still believe that, with a pair of wings, man ought to be able to fly, and that the mathematical data necessary to effective construction simply do not exist. This attitude was reasonable enough in an unlearned age, and Allard was one—a little more conspicuous34 than the majority—among many who made experiment in ignorance, with more or less danger to themselves and without practical result of any kind.
Besnier’s Flying Apparatus.
The seventeenth century was not to end, however, without practical experiment of a noteworthy kind in gliding flight. Among the recruits to the ranks of pioneers was a certain Besnier, a locksmith of Sablé, who somewhere between 1675 and 1680 constructed a glider of which a crude picture has come down to modern times. The apparatus, as will be seen, consisted of two rods with hinged flaps, and the original designer of the picture seems to have had but a small space in which to draw, since obviously the flaps must have been much larger than those shown. Besnier placed the rods on his shoulders, and worked the flaps by cords attached to his hands and feet—the flaps opened as they fell, and closed as they rose, so the device as a whole must be regarded as a sort of flapping glider. Having by experiment proved his apparatus successful,35 Besnier promptly128 sold it to a travelling showman of the period, and forthwith set about constructing a second set, with which he made gliding flights of considerable height and distance. Like Lilienthal, Besnier projected himself into space from some height, and then, according to the contemporary records, he was able to cross a river of considerable size before coming to earth. It does not appear that he had any imitators, or that any advantage whatever was taken of his experiments; the age was one in which he would be regarded rather as a freak exhibitor than as a serious student, and possibly, considering his origin and the sale of his first apparatus to such a client, he regarded the matter himself as more in the nature of an amusement than as a discovery.
Borelli, coming at the end of the century, proved to his own satisfaction and that of his fellows that flapping wing flight was an impossibility; the capabilities129 of the plane were as yet undreamed, and the prime mover that should make the plane available for flight was deep in the womb of time. Da Vinci’s work was forgotten—flight was an impossibility, or at best such a useless show as Besnier was able to give.
The eighteenth century was almost barren of experiment. Emanuel Swedenborg, having invented a new religion, set about inventing a flying machine, and succeeded theoretically, publishing the result of his investigations as follows:—
‘Let a car or boat or some like object be made of light material such as cork130 or bark, with a room within it for the operator. Secondly131, in front as well as behind, or all round, set a widely-stretched sail parallel to the machine, forming within a hollow or bend, which could36 be reefed like the sails of a ship. Thirdly, place wings on the sides, to be worked up and down by a spiral spring, these wings also to be hollow below in order to increase the force and velocity, take in the air, and make the resistance as great as may be required. These, too, should be of light material and of sufficient size; they should be in the shape of birds’ wings, or the sails of a windmill, or some such shape, and should be tilted132 obliquely133 upwards, and made so as to collapse134 on the upward stroke and expand on the downward. Fourth, place a balance or beam below, hanging down perpendicularly135 for some distance with a small weight attached to its end, pendent exactly in line with the centre of gravity; the longer this beam is, the lighter must it be, for it must have the same proportion as the well-known vectis or steel-yard. This would serve to restore the balance of the machine if it should lean over to any of the four sides. Fifthly, the wings would perhaps have greater force, so as to increase the resistance and make the flight easier, if a hood136 or shield were placed over them, as is the case with certain insects. Sixthly, when the sails are expanded so as to occupy a great surface and much air, with a balance keeping them horizontal, only a small force would be needed to move the machine back and forth in a circle, and up and down. And, after it has gained momentum to move slowly upwards, a slight movement and an even bearing would keep it balanced in the air and would determine its direction at will.’
The only point in this worthy127 of any note is the first device for maintaining stability automatically—Swedenborg certainly scored a point there. For the rest, his theory was but theory, incapable of being put37 to practice—he does not appear to have made any attempt at advance beyond the mere suggestion.
Some ten years before his time the state of knowledge with regard to flying in Europe was demonstrated by an order granted by the King of Portugal to Friar Lourenzo de Guzman, who claimed to have invented a flying machine capable of actual flight. The order stated that ‘In order to encourage the suppliant137 to apply himself with zeal138 toward the improvement of the new machine, which is capable of producing the effects mentioned by him, I grant unto him the first vacant place in my College of Barcelos or Santarem, and the first professorship of mathematics in my University of Coimbra, with the annual pension of 600,000 reis during his life.—Lisbon, 17th of March, 1709.’
What happened to Guzman when the non-existence of the machine was discovered is one of the things that is well outside the province of aeronautics. He was charlatan139 pure and simple, as far as actual flight was concerned, though he had some ideas respecting the design of hot-air balloons, according to Tissandier. (La Navigation Aerienne.) His flying machine was to contain, among other devices, bellows140 to produce artificial wind when the real article failed, and also magnets in globes to draw the vessel in an upward direction and maintain its buoyancy. Some draughtsman, apparently gifted with as vivid imagination as Guzman himself, has given to the world an illustration of the hypothetical vessel; it bears some resemblance to Lana’s aerial ship, from which fact one draws obvious conclusions.
A rather amusing claim to solving the problem of flight was made in the middle of the eighteenth century38 by one Grimaldi, a ‘famous and unique Engineer’ who, as a matter of actual fact, spent twenty years in missionary141 work in India, and employed the spare time that missionary work left him in bringing his invention to a workable state. The invention is described as a ‘box which with the aid of clockwork rises in the air, and goes with such lightness and strong rapidity that it succeeds in flying a journey of seven leagues in an hour. It is made in the fashion of a bird; the wings from end to end are 25 feet in extent. The body is composed of cork, artistically142 joined together and well fastened with metal wire, covered with parchment and feathers. The wings are made of catgut and whalebone, and covered also with the same parchment and feathers, and each wing is folded in three seams. In the body of the machine are contained thirty wheels of unique work, with two brass globes and little chains which alternately wind up a counterpoise; with the aid of six brass vases, full of a certain quantity of quicksilver, which run in some pulleys, the machine is kept by the artist in due equilibrium and balance. By means, then, of the friction143 between a steel wheel adequately tempered and a very heavy and surprising piece of lodestone, the whole is kept in a regulated forward movement, given, however, a right state of the winds, since the machine cannot fly so much in totally calm weather as in stormy. This prodigious144 machine is directed and guided by a tail seven palmi long, which is attached to the knees and ankles of the inventor by leather straps145; by stretching out his legs, either to the right or to the left, he moves the machine in whichever direction he pleases.... The machine’s flight lasts only three hours, after which the wings gradually close39 themselves, when the inventor, perceiving this, goes down gently, so as to get on his own feet, and then winds up the clockwork and gets himself ready again upon the wings for the continuation of a new flight. He himself told us that if by chance one of the wheels came off or if one of the wings broke, it is certain he would inevitably146 fall rapidly to the ground, and, therefore, he does not rise more than the height of a tree or two, as also he only once put himself in the risk of crossing the sea, and that was from Calais to Dover, and the same morning he arrived in London.’
And yet there are still quite a number of people who persist in stating that Bleriot was the first man to fly across the Channel!
A study of the development of the helicopter principle was published in France in 1868, when the great French engineer Paucton produced his Théorie de la Vis d’Archiméde. For some inexplicable147 reason, Paucton was not satisfied with the term ‘helicopter,’ but preferred to call it a ‘ptérophore,’ a name which, so far as can be ascertained, has not been adopted by any other writer or investigator. Paucton stated that, since a man is capable of sufficient force to overcome the weight of his own body, it is only necessary to give him a machine which acts on the air ‘with all the force of which it is capable and at its utmost speed,’ and he will then be able to lift himself in the air, just as by the exertion148 of all his strength he is able to lift himself in water. ‘It would seem,’ says Paucton, ‘that in the ptérophore, attached vertically149 to a carriage, the whole built lightly and carefully assembled, he has found something that will give him this result in all perfection. In construction, one would be careful that the machine40 produced the least friction possible, and naturally it ought to produce little, as it would not be at all complicated. The new D?dalus, sitting comfortably in his carriage, would by means of a crank give to the ptérophore a suitable circular (or revolving) speed. This single ptérophore would lift him vertically, but in order to move horizontally he should be supplied with a tail in the shape of another ptérophore. When he wished to stop for a little time, valves fixed150 firmly across the end of the space between the blades would automatically close the openings through which the air flows, and change the ptérophore into an unbroken surface which would resist the flow of air and retard151 the fall of the machine to a considerable degree.’
The doctrine152 thus set forth might appear plausible153, but it is based on the common misconception that all the force which might be put into the helicopter or ‘ptérophore’ would be utilised for lifting or propelling the vehicle through the air, just as a propeller uses all its power to drive a ship through water. But, in applying such a propelling force to the air, most of the force is utilised in maintaining aerodynamic support—as a matter of fact, more force is needed to maintain this support than the muscle of man could possibly furnish to a lifting screw, and even if the helicopter were applied to a full-sized, engine-driven air vehicle, the rate of ascent154 would depend on the amount of surplus power that could be carried. For example, an upward lift of 1,000 pounds from a propeller 15 feet in diameter would demand an expenditure155 of 50 horse-power under the best possible conditions, and in order to lift this load vertically through such atmospheric156 pressure as exists41 at sea-level or thereabouts, an additional 20 horse-power would be required to attain4 a rate of 11 feet per second—50 horse-power must be continually provided for the mere support of the load, and the additional 20 horse-power must be continually provided in order to lift it. Although, in model form, there is nothing quite so strikingly successful as the helicopter in the range of flying machines, yet the essential weight increases so disproportionately to the effective area that it is necessary to go but very little beyond model dimensions for the helicopter to become quite ineffective.
That is not to say that the lifting screw must be totally ruled out so far as the construction of aircraft is concerned. Much is still empirical, so far as this branch of aeronautics is concerned, and consideration of the structural157 features of a propeller goes to show that the relations of essential weight and effective area do not altogether apply in practice as they stand in theory. Paucton’s dream, in some modified form, may yet become reality—it is only so short a time ago as 1896 that Lord Kelvin stated he had not the smallest molecule158 of faith in aerial navigation, and since the whole history of flight consists in proving the impossible possible, the helicopter may yet challenge the propelled plane surface for aerial supremacy159.
It does not appear that Paucton went beyond theory, nor is there in his theory any advance toward practical flight—da Vinci could have told him as much as he knew. He was followed by Meerwein, who invented an apparatus apparently something between a flapping wing machine and a glider, consisting of two wings, which were to be operated by means of a rod; the venturesome one who would fly by means of this42 apparatus had to lie in a horizontal position beneath the wings to work the rod. Meerwein deserves a place of mention, however, by reason of his investigations into the amount of surface necessary to support a given weight. Taking that weight at 200 pounds—which would allow for the weight of a man and a very light apparatus—he estimated that 126 square feet would be necessary for support. His pamphlet, published at Basle in 1784, shows him to have been a painstaking160 student of the potentialities of flight.
Jean-Pierre Blanchard, later to acquire fame in connection with balloon flight, conceived and described a curious vehicle, of which he even announced trials as impending161. His trials were postponed162 time after time, and it appears that he became convinced in the end of the futility163 of his device, being assisted to such a conclusion by Lalande, the astronomer164, who repeated Borelli’s statement that it was impossible for man ever to fly by his own strength. This was in the closing days of the French monarchy165, and the ascent of the Mongolfiers’ first hot-air balloon in 1783—which shall be told more fully in its place—put an end to all French experiments with heavier-than-air apparatus, though in England the genius of Cayley was about to bud, and even in France there were those who understood that ballooning was not true flight.
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1
legendary
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| adj.传奇（中）的，闻名遐迩的；n.传奇（文学） | |
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authenticity
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| n.真实性 | |
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remarkable
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| adj.显著的，异常的，非凡的，值得注意的 | |
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attain
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| vt.达到，获得，完成 | |
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attainments
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| 成就，造诣； 获得( attainment的名词复数 )； 达到； 造诣； 成就 | |
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mere
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| adj.纯粹的；仅仅，只不过 | |
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7
hop
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| n.单脚跳，跳跃；vi.单脚跳，跳跃；着手做某事；vt.跳跃，跃过 | |
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glide
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| n./v.溜，滑行；(时间)消逝 | |
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glider
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| n.滑翔机；滑翔导弹 | |
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gliding
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| v. 滑翔 adj. 滑动的 | |
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apparatus
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| n.装置，器械；器具，设备 | |
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dissemination
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| 传播,宣传,传染(病毒) | |
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13
treatise
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| n.专著；(专题)论文 | |
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deductions
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| 扣除( deduction的名词复数 )； 结论； 扣除的量； 推演 | |
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15
excellence
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| n.优秀，杰出，(pl.)优点，美德 | |
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16
investigations
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| （正式的）调查( investigation的名词复数 )； 侦查； 科学研究； 学术研究 | |
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investigation
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| n.调查，调查研究 | |
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18
lengthy
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| adj.漫长的，冗长的 | |
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deficient
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| adj.不足的，不充份的，有缺陷的 | |
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equilibrium
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| n.平衡，均衡，相称，均势，平静 | |
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propeller
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| n.螺旋桨，推进器 | |
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22
descend
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| vt./vi.传下来，下来，下降 | |
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23
quotation
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| n.引文，引语，语录；报价，牌价，行情 | |
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24
opposition
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| n.反对，敌对 | |
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membrane
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| n.薄膜，膜皮，羊皮纸 | |
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fabric
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| n.织物，织品，布；构造，结构，组织 | |
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27
impervious
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| adj.不能渗透的，不能穿过的，不易伤害的 | |
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28
regain
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| vt.重新获得，收复，恢复 | |
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fully
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| adv.完全地，全部地，彻底地；充分地 | |
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noted
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| adj.著名的，知名的 | |
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investigator
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| n.研究者，调查者，审查者 | |
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32
sundry
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| adj.各式各样的，种种的 | |
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33
inclination
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| n.倾斜；点头；弯腰；斜坡；倾度；倾向；爱好 | |
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attaining
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| （通常经过努力）实现( attain的现在分词 )； 达到； 获得； 达到（某年龄、水平、状况） | |
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35
proficiency
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| n.精通，熟练，精练 | |
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36
thigh
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| n.大腿；股骨 | |
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37
apparently
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| adv.显然地；表面上，似乎 | |
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pictorial
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| adj.绘画的；图片的；n．画报 | |
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inverted
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| adj.反向的，倒转的v.使倒置，使反转( invert的过去式和过去分词 ) | |
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40
descends
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| v.下来( descend的第三人称单数 )；下去；下降；下斜 | |
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41
conjectured
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| 推测，猜测，猜想( conjecture的过去式和过去分词 ) | |
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42
tilting
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| 倾斜，倾卸 | |
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43
lesser
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| adj.次要的，较小的；adv.较小地，较少地 | |
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44
aeronautical
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| adj.航空（学）的 | |
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45
purely
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| adv.纯粹地，完全地 | |
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46
versatile
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| adj.通用的，万用的；多才多艺的，多方面的 | |
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47
posthumous
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| adj.遗腹的；父亡后出生的；死后的，身后的 | |
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48
astronomical
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| adj.天文学的，（数字）极大的 | |
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49
instinctive
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| adj.(出于)本能的；直觉的；(出于)天性的 | |
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50
mechanism
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| n.机械装置；机构，结构 | |
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51
demonstration
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| n.表明，示范，论证，示威 | |
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52
concur
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| v.同意，意见一致，互助，同时发生 | |
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53
illustrated
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| adj. 有插图的，列举的 动词illustrate的过去式和过去分词 | |
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54
forth
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| adv.向前；向外，往外 | |
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55
repose
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| v.(使)休息；n.安息 | |
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56
joints
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| 接头( joint的名词复数 )； 关节； 公共场所（尤指价格低廉的饮食和娱乐场所） （非正式）； 一块烤肉 （英式英语） | |
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57
lateral
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| adj.侧面的，旁边的 | |
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58
perpendicular
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| adj.垂直的，直立的；n.垂直线，垂直的位置 | |
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59
underlying
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| adj.在下面的，含蓄的，潜在的 | |
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60
inertia
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| adj.惰性，惯性，懒惰，迟钝 | |
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61
elastic
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| n.橡皮圈，松紧带；adj.有弹性的；灵活的 | |
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62
elasticity
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| n.弹性，伸缩力 | |
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63
rebounds
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| 反弹球( rebound的名词复数 )； 回弹球； 抢断篮板球； 复兴 | |
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64
accomplished
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| adj.有才艺的；有造诣的；达到了的 | |
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65
revolve
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| vi.(使)旋转；循环出现 | |
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66
upwards
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| adv.向上，在更高处...以上 | |
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67
laterally
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| ad.横向地；侧面地；旁边地 | |
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68
drawn
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| v.拖，拉，拔出；adj.憔悴的，紧张的 | |
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69
flattened
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| [医]（水）平扁的，弄平的 | |
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70
virtue
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| n.德行，美德；贞操；优点；功效，效力 | |
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71
recoil
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| vi.退却，退缩，畏缩 | |
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72
impetus
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| n.推动，促进，刺激；推动力 | |
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73
thoroughly
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| adv.完全地，彻底地，十足地 | |
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74
craftily
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| 狡猾地，狡诈地 | |
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75
remains
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| n.剩余物，残留物；遗体，遗迹 | |
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76
doomed
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| 命定的 | |
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77
expended
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| v.花费( expend的过去式和过去分词 )；使用（钱等）做某事；用光；耗尽 | |
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alleged
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| a.被指控的，嫌疑的 | |
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79
motive
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| n.动机，目的；adv.发动的，运动的 | |
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80
deducted
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| v.扣除，减去( deduct的过去式和过去分词 ) | |
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81
entirely
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| ad.全部地，完整地；完全地，彻底地 | |
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82
mythical
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| adj.神话的；虚构的；想像的 | |
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83
momentum
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| n.动力，冲力，势头；动量 | |
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84
velocity
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| n.速度，速率 | |
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85
contraction
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| n.缩略词，缩写式，害病 | |
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86
sufficiently
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| adv.足够地，充分地 | |
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87
quotations
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| n.引用( quotation的名词复数 )；[商业]行情（报告）；（货物或股票的）市价；时价 | |
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investigators
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| n.调查者，审查者( investigator的名词复数 ) | |
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89
combustion
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| n.燃烧；氧化；骚动 | |
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90
wireless
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| adj.无线的；n.无线电 | |
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excerpt
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| n.摘录，选录，节录 | |
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92
vessel
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| n.船舶；容器，器皿；管，导管，血管 | |
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93
antedated
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| v.（在历史上）比…为早( antedate的过去式和过去分词 )；先于；早于；（在信、支票等上）填写比实际日期早的日期 | |
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94
precluded
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| v.阻止( preclude的过去式和过去分词 )；排除；妨碍；使…行不通 | |
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95
novice
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| adj.新手的，生手的 | |
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96
pious
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| adj.虔诚的；道貌岸然的 | |
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vows
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| 誓言( vow的名词复数 )； 郑重宣布，许愿 | |
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dubious
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| adj.怀疑的，无把握的；有问题的，靠不住的 | |
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celebrated
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| adj.有名的，声誉卓著的 | |
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fable
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| n.寓言；童话；神话 | |
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101
proceeding
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| n.行动，进行，(pl.)会议录，学报 | |
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102
ascend
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| vi.渐渐上升，升高；vt.攀登，登上 | |
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103
exhausted
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| adj.极其疲惫的，精疲力尽的 | |
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104
procured
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| v.（努力）取得， （设法）获得( procure的过去式和过去分词 )；拉皮条 | |
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105
plunged
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| v.颠簸( plunge的过去式和过去分词 )；暴跌；骤降；突降 | |
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density
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| n.密集，密度，浓度 | |
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detailed
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| adj.详细的，详尽的，极注意细节的，完全的 | |
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108
lighter
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| n.打火机，点火器；驳船；v.用驳船运送；light的比较级 | |
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109
copper
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| n.铜；铜币；铜器；adj.铜(制)的；(紫)铜色的 | |
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quaint
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| adj.古雅的，离奇有趣的，奇怪的 | |
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111
oars
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| n.桨，橹( oar的名词复数 )；划手v.划（行）( oar的第三人称单数 ) | |
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112
disturbances
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| n.骚乱( disturbance的名词复数 )；打扰；困扰；障碍 | |
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113
vessels
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| n.血管( vessel的名词复数 )；船；容器；（具有特殊品质或接受特殊品质的）人 | |
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fortresses
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| 堡垒，要塞( fortress的名词复数 ) | |
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brass
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| n.黄铜；黄铜器，铜管乐器 | |
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varnished
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| 浸渍过的，涂漆的 | |
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incapable
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| adj.无能力的，不能做某事的 | |
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ascertained
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| v.弄清，确定，查明( ascertain的过去式和过去分词 ) | |
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ignominiously
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| adv.耻辱地，屈辱地，丢脸地 | |
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scrap
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| n.碎片；废料；v.废弃，报废 | |
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conspicuous
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| adj.明眼的，惹人注目的；炫耀的，摆阔气的 | |
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module
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| n.组件，模块，模件；(航天器的)舱 | |
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123
applied
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| adj.应用的；v.应用，适用 | |
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contrive
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| vt.谋划，策划；设法做到；设计，想出 | |
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emulate
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| v.努力赶上或超越，与…竞争；效仿 | |
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aeronautics
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| n.航空术，航空学 | |
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worthy
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| adj.(of)值得的，配得上的；有价值的 | |
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promptly
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| adv.及时地，敏捷地 | |
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capabilities
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| n.能力( capability的名词复数 )；可能；容量；[复数]潜在能力 | |
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cork
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| n.软木，软木塞 | |
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secondly
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| adv.第二，其次 | |
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tilted
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| v. 倾斜的 | |
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obliquely
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| adv.斜； 倾斜； 间接； 不光明正大 | |
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collapse
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| vi.累倒；昏倒；倒塌；塌陷 | |
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perpendicularly
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| adv. 垂直地, 笔直地, 纵向地 | |
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hood
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| n.头巾，兜帽，覆盖；v.罩上，以头巾覆盖 | |
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suppliant
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| adj.哀恳的；n.恳求者，哀求者 | |
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zeal
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| n.热心，热情，热忱 | |
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charlatan
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| n.骗子；江湖医生；假内行 | |
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140
bellows
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| n.风箱；发出吼叫声，咆哮（尤指因痛苦）( bellow的名词复数 )；（愤怒地）说出（某事），大叫v.发出吼叫声，咆哮（尤指因痛苦）( bellow的第三人称单数 )；（愤怒地）说出（某事），大叫 | |
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141
missionary
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| adj.教会的，传教(士)的；n.传教士 | |
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142
artistically
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| adv.艺术性地 | |
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143
friction
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| n.摩擦，摩擦力 | |
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144
prodigious
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| adj.惊人的，奇妙的；异常的；巨大的；庞大的 | |
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straps
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| n.带子( strap的名词复数 )；挎带；肩带；背带v.用皮带捆扎( strap的第三人称单数 )；用皮带抽打；包扎；给…打绷带 | |
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inevitably
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| adv.不可避免地；必然发生地 | |
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inexplicable
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| adj.无法解释的，难理解的 | |
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148
exertion
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| n.尽力，努力 | |
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149
vertically
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| adv.垂直地 | |
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150
fixed
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| adj.固定的，不变的，准备好的；(计算机)固定的 | |
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151
retard
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| n.阻止，延迟；vt.妨碍，延迟，使减速 | |
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152
doctrine
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| n.教义；主义；学说 | |
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153
plausible
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| adj.似真实的，似乎有理的，似乎可信的 | |
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154
ascent
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| n.(声望或地位)提高；上升，升高；登高 | |
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expenditure
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| n.(时间、劳力、金钱等)支出；使用，消耗 | |
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atmospheric
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| adj.大气的，空气的；大气层的；大气所引起的 | |
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157
structural
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| adj.构造的，组织的，建筑（用）的 | |
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158
molecule
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| n.分子，克分子 | |
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159
supremacy
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| n.至上；至高权力 | |
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160
painstaking
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| adj.苦干的；艰苦的，费力的，刻苦的 | |
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161
impending
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| a.imminent, about to come or happen | |
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162
postponed
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| vt.& vi.延期，缓办，（使）延迟vt.把…放在次要地位；[语]把…放在后面（或句尾）vi.（疟疾等）延缓发作（或复发） | |
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163
futility
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| n.无用 | |
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164
astronomer
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| n.天文学家 | |
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165
monarchy
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| n.君主，最高统治者；君主政体，君主国 | |
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