Those who desire to travel like the birds through Nature's great highway, the atmosphere, must not be discouraged by the wise ones who advise them to attempt to do only what is practicable, telling them that the problem of flight is in the same cate gory as perpetual motion, the search for the philosopher's stone and for the fabled fountain of perpetual youth.
    Practically the same thing was said regarding a proposition I made over thirty years ago to our Government to build an experimental submarine boat. The late Commodore Simpson reporting on that suggestion to the Navy Department said it would be of no use, because no one could be found to operate it, and because it could not be directed under water. The attempt to do so, he added, would be practically an aggravated case of a man trying to find his way in a fog.
    A few years before his victory over the Spanish fleet at Santiago, the late Admiral Sampson, in a spirit of courageous kindness, advised me to discontinue my efforts to persuade our Navy Department to experiment with submarine boats as my time would surely be wasted. He assured me that even though such a boat could do everything that I had proved to be practicable with my second submarine boat in 1880, yet he could see no use for them in the Navy.
    Still another high authority, Herr Bus- ley, the head of a German Imperial School for some division of that naval service, asserted that no man of experi- ence in marine design of construction, no naval architect, had ever been foolish enough to waste his time on the con- struction of submarine boats, and that only unsuccessful medical doctors, school teachers and other outsiders, ever made attempts in that direction.
    He fairly hit the mark in that observation as I happen to be an ex-school teacher. Even with this criticism of submarines they are now included in the building program of all important maritime countries and they already have had influence in the designs of their new ships. They are no longer laughed at or ridiculed. And what is still more remarkable, I am credibly informed that Herr Busley himself now favors the "only real thing" in submarines, a Ger- man invention.
    This remarkable change in the views of naval departments, of boards of ad-
miralty and other officials connected with the management of naval affairs, in this country and in Europe, was not due to any striking improvement in principle, or gain in efficiency of this type of boat, between the date of the successful experiments made with my second boat in 1881 and the exhibition of the Holland to Admiral Dewey on the Potomac, in April 1900 but simply and solely to the unbiased opinion that eminent sea captain frankly expressed, which carried universal conviction and was absolutely beyond question.
    Although it has been remarked that professional persons are generally conservative, that is, opposed to the acceptance of new ideas, and that many of them even manifest a tendency to run in a rut, and to keep running, there persistently, yet, in the particular, they are no different from the rest of humanity.
    Since the very beginning of things the simplest and most rapid mode of animal locomotion has been daily exhibited before their faces, as if to provoke them to imitate it, yet nothing worthy of notice has ever been done towards its accomplishment. It is true that men have always desired to be able to fly like the birds, and in cases of dire necessity, as in critics reduced to extremity by beleaguering armies, or travelers dying of hunger or thirst in the desert, that power was even more ardently but fruitlessly desired.
    From very ancient times men vainly attempted to fly with crude imitations of wings operated by their arms. Those who happened to survive their experi- ments might be pardoned for believing that the power of levitation was mys- terious because it proved to be beyond their reach, but the general tendency of humanity, even at the present day, to attribute obscure natural phenomena to some occult power, or to accept the decision of some "authorities" that it is mysterious, saves them the trouble of investigation, and they are satisfied. Witness the belief in the work of Plato and of Jove in the thunder and lighting, amongst the Ancient Greeks, and of the Thunder bird amongst the modern Zulus and Hottentots.
    But the most astonishing exhibition of that kind is to hear educated men, in- vestigators of natural phenomena, at the present day, talk about the mysteries of flight and soaring, or attributing super- human intelligence to birds in the art of


balancing, selecting favoring currents, etc., instead of openly confessing that there must be some simple functions of the natural apparatus for flight that they have mistaken or misunderstood, or which until now, they have failed to no- tice.
    Why do they propose explanations of bird flight that cannot possibly account for even one-half of the support re- quired in certain plain cases and yet not inform us regarding what is lacking thereto? Even though they would not wish     to     be    credited    with    belief   in   the   occult, equaling that of the ancient Greeks, or the Modern Zulus, yet they afford us no alternative explana- tion.
    It is unfortunate that the net result of the investigations of those who have studied bird flight is that it is far be- yond human reach if they are not greatly mistaken.
    Almost without exception they maintain absurd theories that cannot in the nature of things be true, that are re- futed before their faces every day by every flying thing, and that are far from being reasonable and simple as are the natural functions regarding which they dogmatize.
    We have been assured by conscientious and zealous workers in this field that air reaction due to down-beating wings must be competent to balance the bird's weight.
    This   takes   account  only of the sup- port afforded while a bird is making its down stroke. The source of support during the elevation of the wings, they generally credit to the mystery account, although Mr. O. Chanute, who is proba- bly, the most painstaking and industrious of them all, asserts that aeroplane action must be credited with giving great as- sistance.
    The utter inadequacy of air reaction from down beating as a means of support during steady flight must also be credited to the mystery account.
    Still   another   mystery is thus formu- lated by Mr. O. Chanute in his valuable and interesting work, "Progress in Fly- ing Machines," page 251. "There is good reason to believe that the output of energy appertaining to the motor mus- cles of birds in proportion to their weight, which, as we have seen there is good reason to believe develop work in ordinary flight at the rate of one horse power to 20 pounds of weight, and can for a brief period, in rising, give out energy at such a rate as to represent an engine of only 5 or 6 pounds weight de- veloping one horse power."   That is,  a
20 pound bird develops one horse power during steady flight, and a 5 pound bird develops one horse power when rising , say from the level, and also when alighting.
    Maintaining   this   proportion   a   man who is ambitious to fly by his own mus- cular energy must be able to develop 150 divided by 20, equals 7½ horsepower continuously   during   steady   flight, and 150 divided by 5, equals 30 horsepower when rising from the level   and   alight- ing.
    We need not delay any longer over the mystery account as it is quite a long one, as will be apparent later.
    With this encouragement in mind, we should act wisely in  quitting   the   study of flying for good,   in case we find that the authorities are not in error, or else follow it up to an actual demonstration, if we find that by common sense appli- cation of the laws of physics, and by comparisons with the perfect examples afforded by Nature, that they are mis- taken.
    For this purpose we may study a pro- posed design for a machine to be oper- ated by muscular energy alone. We shall then encounter the ordinary   "mysteries" of the case and see how Nature treats them,   as well as determine whether a man can operate it   himself even   though he possesses less than one one-hundred and twentieth part of the muscular power that the authorities assure us is quite essential.
    What we shall most assuredly discover from our study is the extreme denseness of human stupidity in failing through all past ages to understand the simplest and most rapid mode of animal locomotion, although man was ingenious enough to cloak over his laziness of mind and neglect and rest satisfied by assuring himself that the whole subject was an impenetrable mystery.
    No one needs to excuse himself because we are all together in the same boat and in very good company. Some very distinguished scientific gentlemen and great inventors, amongst whom may be named Thomas A. Edison, Professor Melville Bell, the late Professor Langley, O. Chanute and many others in this country, as well as very many equally distinguished scientists in Europe, have devoted much study, although vainly, to this interesting subject.
    My first design was made in 1863, shortly before I began the study of submarines, but I had no suspicion of the influence of the chief, almost the only, natural force employed by every flying animal   until   it   occurred   to   me,   not


as the result of study or industry, but purely by accident a few years ago. Therefore, this discovery is not an in- vention, and I have great pleasure in thus describing it publicly in order that some one may be stimulated to lead the way into what will be practically, a new order of existence.
  Individual Flying Machine Designed
       to be Operated Solely by Mus-
                      cular Energy

    It may consist of two transverse wing arms at the operator's back, one of them at the level of his neck, the other one being set about four or five inches below his hips.  These wing arms are fastened on short tubular shafts provided with ball bearings at each end of each shaft.  These shafts are carried by bearings on a foundation plate, or substitute for the bird's backbone, which is provided with rigid metal carriers at its sides, near the middle of its length, that extend around the operator's sides for the purpose of holding the treadle guides and a frame carrying a diaphragm on which his body rests in a nearly horizontal position, face downward, when he is in full flight.
    Carried on bearings fastened on the foundation plate are also placed two short, transverse tubular shafts opposite to one another, their approaching ends carrying mitre gears, which gear into two corresponding gears placed on the inner ends of the tubular shafts that have their outer ends fastened to the transverse wing arms. The short transverse shafts carry near their outer ends each a grooved metal arc, carrying a small wire rope, which extends backwards, or downwards, from where one end of each is fastened to each are radius to a treadle at each side, at the lower end of the apparatus.
    It   is   evident   that   when the short shafts are connected by mitre wheels and the treadles are pushed alternately, the operator's body being inclined forward, or nearly horizontal, that the two wing arms will vibrate in opposite directions.
    The wing sails are set on pieces of wood bent to the proper curvature and attached to metal rings through which the wing arms   pass.   Pins passing through the arms limit the swing of the cross pieces around them to about 45 degrees in order to provide that the sails may automatically feather,   that is,   change their inclination, when the machine is starting in a calm and before it has attained sufficient velocity to render feathering unnecessary.
    Provision is made in the wing arm bearings to permit of the arms being revolved   simultaneously   around   their
axis with the object of controlling the inclination of the sails. This is accom- plished by means of two light handles depending one on either side, from the forward wing arm and by a connection between both arms.
    By means of handles referred to, the machine can be operated by the hands, or it may be driven by the feet by means of the treadles, or, both means of op- eration may be employed together when the hard work of starting or alighting in a calm, from the level, happens to be necessary.
    The inertia of all the moving parts is cushioned by a device attached to the radial arms of the arcs carrying the wire rope on each side. The effect of cush- ioning is to reverse the direction of motion of the wings without shock and thus economize power and facilitate speed.
    It is evident that each half of each wing arm, with its sail balances the other half with its sail, and that compensation to obtain balance is therefore unnecessary.
    The wing arms in the machine, illustrated on page--, are made of No. 22, one and one-quarter inch steel tubes in the middle. tapering to three-eighths inch diameter at the ends. These tubes will be strong enough to dispense with trussing, which is inadmissible.
    The weight of the machine illustrated will be, when it is completed, 35 pounds, but with more suitable material and better workmanship that weight can be reduced to 15 pounds. This figure shall be taken as the weight of effective machine, although it may weigh more.
    It is evident that the mysteries of stability and balancing will be eliminated in this machine, because the center of gravity of apparatus and operator together will be about 15 inches under the center of support, which is unchangeable and effective at the crossing of two diagonal lines joining the centre of effort of the wings that are situated diagonally.
    The centre of resistance will be on the same plane as the centre of thrust, or propulsion, and there can, therefore, exist no tendency to tip upwards of downwards.
    The anterior edges of the wings being thick and convexed eliminates the risk to the operator of meeting the fate of Lillenthal. With the fore-and-aft section of his planes or wings nearly corre- sponding with the plane of his direction of motion and his apparatus moving at comparatively slow speed, there is little wonder that, owing to a slight move- ment   of   the   operator,   or   a   vertical


current of low speed, that their upper forward surfaces took the wind, or in nautical phraseology were taken aback.
    This apparatus is designed to imitate as closely as possible the mechanism ex- isting in Nature for the attainment of flight through the air, because the un- numbered failures of attempts that aimed at employing only crude substitutes for natural means and methods,   prove that its plans are the best and that the de- gree of success of devices for these purposes will depend on the exactness with which its perfect examples are fol- lowed.
    It will be shown herein that the mech- anism of natural flight has never here- tofore been properly understood. Until within the last decade, it was generally believed that the necessary aerial sup- port of flying animals was afforded sole- ly by the reaction of air against the de- scending wings,  and that during its flight a bird produces a reaction at the centre of effort of each wing competent to support at least one-half of the bird's weight.
    A bird's wing during beating, or rowing flight, is a lever of the third order, having the fulcrum at one end, the weight or, working point, towards the other end, and the power applied at some point between them. The inner joint, at which the wing is attached to the body, is the fulcrum. The power is applied at the point of attachment of the pectoral muscles to the wing arm.
    The working point at which the power is utilized being taken as the centre of effort of each wing, the distance from the fulcrum to the centre of effort is from four to nine times greater than the distance from the fulcrum to the point of attachment of the pectoral muscles, depending on the species of bird. This ratio generally increases with the size of the species, being greatest with soarers, and about nine in the case of the great wandering albatross, the information regarding which is sufficiently definite for purposes of comparison.
    If the reaction equal-to-weight theory is correct then the pectoral muscles must contract, at each wing stroke, with a force equal to nine time the bird's weight in order that the reaction equal to the weight may exists at the centre of effort, leaving the question of support during the intermission, while the wings are rising. entirely out of consideration or rather crediting it to the mystery account.
    The same bird make wing beats at the rate of 110 per minute, through about 90 degrees of arc, when rising from the water. Therefore, if the pressure at the
centres of effort must be equal to the weight, twenty pounds, it must be exerted at the rate of 110 beats per minute, the vertical speed of the centres of effort being 21.5985 feet per second, 21.5985, divided by 550, equals 0.78 horsepower.
    The force actually required for support by air reaction alone during the down beat is equal to the bird's weight divided by the ratio of the levers in the wings 9: 20 divided by 9 equals 2.29 pounds at the centres of effort. Reaction 2.29x21.59, divided by 550, equals 0.087 horse power, equals 43.95 foot pounds per second and this force is exerted only when the bird begins to rise from smooth water or when alighting.
    The source of support during the elevation of the wings will be pointed out later.
    Another reference to Nature will reveal the source of the supporting power during flight. An albatross flying in calm weather, beating its wings and not soaring, supports its 20 pound weight with very little apparent effort. The wing spread is 10.5 feet, the radius of the centre of effort of each wing is about 3.75 feet, total wing surface 5.5 square feet, and the vertical speed of the centre of effort of each wing is at the leisurely rate of 5.5 feet per second. The wing reaction to direct down beating is, in this case, 0.0703 pounds per square foot, and the total direct reaction is 5.5x0.0703, equals 0.385 pounds.
    Thus it falls short of adequate support, and it is in action only while the wings are descending. Nor can aeroplane action of the wings, as it is at present believed to be employed in steady flight, afford any satisfactory explanation of the bird's means of support.
    Suppose that, as is commonly believed the wings do work as aeroplanes during the elevation. The speed in this kind of flight is from 30 to 35 miles per hour. The pressure on a flat surface of a wind blowing 35 miles per hour is 6.125 pounds per square foot. The inclination of the wings when acting as aeroplanes during flight is generally calculated to be about 6 degrees. The normal pressure of the wing surface due to this inclination is 0.207 of the pressure at no inclination, the vertical, or lifting component is 0.206, and the horizontal component is 0.0217 of the same. The lifting force due to aeroplane action under these conditions should therefore be 5.5x6.1258x0.206, equals 6.939 pounds.
    Mr. O. Chanute believes that 30 percent, should be added to this amount because of the greater efficiency of con- caved surfaces than of the flat plane sur-


faces: 6.939x1.3, equals 9.02 pounds.
    These results are surprising in view of the consensus of opinion of the authorities cited by Mr. Chanute. Instead of the 7.5 horse power that the albatross should develop in order to be in agreement with their theories, we find only 0,386x5.5 feet per second, divided by 550 equals 0.00396 horse power, equals 2.178 foot pounds per second, developed as the result of direct reaction in steady flight.
    Because the wings act, in this case, as a vibrating propeller, 60 per cent of this power is expended as propulsive force and there remains as direct lift, during down beating, only 0.1544 pounds, and no help whatever from this source while the wings are rising.
    On the supposition that aeroplane action is effective during the elevation of the wings, we find that the resulting lift can be nor more than 9.02 pounds, less than one-half of the bird's weight, and this help cannot exist during the descent of the wings.
    It is evident, therefore, that if the bird's support is to depend on direct reaction during the down beating, and to aeroplane action during wing elevation, there must be 60 times more elevating power developed during the rise of the wings than during their descent. But the maximum lifting power exerted, during one-half the time is less than one-half of what is required and of what most certainly exists.
    This is all that existing theories sug- gest or permit in explanation of the con- undrum of how the 20 pounds albatross supports its weight during beating or row- ing flight,  but it is very much less than is actually provided and employed in Nature even though the source of the remainder has thus far escaped obser- vation.
    It is certain that there can be nothing occult in the performance of the alba- tross described above, and it is probable that the failure  thus far  to explain   it, and to solve the mystery of soaring,   is owing mainly to the influence of incor- rect theories and to omissions and over- sights in observing the results of experi- ments  and  the natural function referred to above.   Yet the bird moves through the air like a thing without weight   and not merely as a floating object that rests on something else.   It is remarkable also that it moves in circles, curves and re- verse curves, and that it descends to the surface of the water   and  rises again as if  there were no such thing as gravita- tion to hinder it.   As  soon as it acquires a  certain  horizontal speed  it is  imme-
diately endowed with the hitherto incomprehensible power of levitation. Its weight is certainly no matter whether the wings are beating downward, rising, or extended in soaring.
    The bird's support cannot be due to aeroplane action, that is, compression of air under the advancing wings, which it is calculated, must carry their anterior edges about six degrees higher than the posterior edges in order to produce sufficient effect as aeroplanes. We have seen that with six degrees inclination, the support afforded is less than one-half of what is required even during one-half the time it is flying. But we have also have incontestable evidence that the albatross soars horizontally with the under surfaces of the wings quite flat in the fore-and-aft direction. We have equally good evidence that the turkey buzzard generally soars horizontally with its wings similarly held flat. In neither of these cases can what in commonly known as aeroplane action exist.
    Neither can the concaving of the under wing surfaces afford any help although so much has been attributed to is efficiency. It will be apparent to any person that examines the wing of an albatross preserved in any museum of natural history that the surface under the primary feathers is quite flat, and that if a flat card or board is held, fore and aft, under the secondary and tertiary wing feathers, that a pressure representing what actually exists there during flight, viz., one-fortieth of one pound per square inch of surface supported that that part will be perfectly flat, thus establishing the correctness of the observations quoted above and compelling us to reject all explanations of bird flight thus far proposed.
    Very costly and careful experiments were made with inclined planes by the late professor Langley, Sir Hiram S. Maxim, Mr. O. Chanute, and others, in this field, as it appeared to be the most promising of affording light on the mys- teries of flight and soaring. They de- termined the varying degrees of  reac- tion from pressure of air on surfaces of various sizes and of varying degrees of inclination, and they found how many pounds   weight could be   lifted per square foot of inclined plane, and per horse power applied to moving it horizontally. But the vitally important mat- ter, the agent that every flying thing employs to sustain its weight, defective, or minus pressure of air rarefaction over the wings and tail, - remained almost en- tirely unnoticed, and certainly was never defined as the important factor  in  pro-


ducing levitation.     A study of the transverse, vertical section of a bird's wing when it is extended in flight will render it clear that defective pressure must exist, during flight, over the greater part of its upper surface when a certain speed is attained. The wing, in this case, moves approximately edgewise through the air at good speed, and the air may either impinge on the under surface or move parallel with it. The air stream is divided by the wings anterior edge, the body of the stream represented by the wings thickness at each transverse section being deflected upward and over the upper surface by the wing's curved forward section, the extreme forward edge of which is nearly on the same plane as the under surface of the wing. The air thrown upward by the wing's curved edge cannot recurve instantly and get into close contact with the upper surface on account of its inertia. The air pressure, therefore, drops below atmosphere between the passing current of air and the wing's upper surface, the space between the them being probably filled by eddying currents at a pressure below that existing in the free air depending on the relative speeds of the air current and the wing and on the degree of their inclination to each other.
    How very small may be the proportion, or degree, of defective pressure over the wings required for support in the case of the flying albatross considered above may be easily ascertained. The total wing surface is 5.5 square feet = 792 square inches, to which add 8 square inches for the tail, total 800 square inches. It was shown above that the vertical component of the direct reaction due to the down beat of the wings was only 0.2344 pounds, and this is so small, considering the bird's weight, that it may be neglected.
    The bird's 20 pounds' weight will therefore be supposed to be entirely supported by the defective pressure over the wings. Bird's weight, 20 pounds. Divided by supporting surface, 800 square inches. Equals 1/40 pound.
    The effect of negative, or defective pressure on one side of a plane exposed to the wind being equivalent to just as much positive pressure on its other or exposed side, the one-fortieth pound defective, or negative, pressure per square inch on the wing's upper surface is equivalent to one-fortieth pound positive pressure on each square inch of their under surface.
    The surface being 800 square inches, 800x1/40 equals 20 pounds, the total weight.
    This helps to explain the increased lifting efficiency of inclined planes with increasing inclination. The solution of the problem of flight was near, when, in 1880, it was pressed that a ship's propeller, in most cases, moved the ship as much by pumping water from ahead as by pushing it directly backward.
    It was still nearer when Hargreaves invented the box kite, but his apparently satisfactory explanation of reasons for its efficiency prevented a search for the true one. Any person can readily satisfy himself of the usefulness of defective pressure by taking an ordinary box kite, measuring its lifting power and weight against an ordinary kite have the same lifting surface, then continuing the sides of the box kite vertically over the upper lifting planes until they project above them a few inches in front, at the edges of the sides, and have the upper edges of the lengthened sides made horizontal when the kite is flying.
    The gain over the original box kite will be clearly apparent.
    The lower plane in the box kite fully employs defective pressure because the vertical side planes joined to its edges prevent the outer air from flowing inward over the upper surface of the lower plane to destroy the defective pressure existing there and thus mar its efficiency. Now if a rectangular portion of each of the side vertical planes and of nearly the full fore-and-aft length of the lower plane be removed from their lower ends so as to permit the outer air to be drawn in by the rarefaction existing over the lower planes, and if the side projections over the vertical planes be removed, it will be found that the efficiency of the box kite will be destroyed and that it will require a much stronger wind to cause it to rise while it is in this condition, although its steadiness will not be noticeably impaired.
    If convexed planes be substituted for the flat planes in the kite the mystery of bird levitation will be quickly solved to the experimenter's satisfaction.
    There are good reasons for believing that the still deeper mystery of soaring flight is capable of an equally simple explanation. In the case cited above, of an albatross flying in calm weather, it was shown that the propelling, or drift, force was only 0.2316 pounds; that is,


about one-eighty-sixth part of the bird's weight applied as propelling force suffices to overcome the frictional resistance of the air, which must be very little indeed against the exceedingly smooth surface of the bird's body and wings, and it maintains speed enough to preserve a suitable degree of defective pressure over the wings and tail to afford necessary support.
    A study of Mr. O. Chanute's table of lift and drift force for aeroplanes propelled through air while inclined to the horizon indicates that the inclination of the albatross's wings should be about 43 minutes of arc if they were flat planes. But as they are thick edged, convex surfaces, their action may differ considerably from the performance of planes.
    The chief difference is that the angle of inclination may vary a good deal from zero, or even minutes, to a considerable positive angle without notably affecting the degree of minus pressure above them. To employ nautical phraseology, the bird may sail even into the wind's eye and still have support and steerage way.
    It is also very doubtful whether the inner halves of the wings that are chiefly effective as supports have, during flight, any inclinations to the air streams they encounter. If they have no inclination air resistance must be reduced to a minimum and the proportion of power expended in propulsion, already shown to be very small indeed, must be still further reduced.
    Propulsion is done by the outer halves, or rather about two-fifths, of the wings, which are much less rigid than the inner parts that are held stiff enough to support the weight steadily while flying.
    The outer parts indeed do their proportion of supporting, but being more flexible, they yield to the extra pressure during the down beat.
    The posterior edge is forced upward and the wing thus forms half of a vibrating screw propeller that wastes no power in indirect action, such as happens with the best propeller designed by man.
    Referring again to the case of the albatross employing beating flight in calm weather. The speed of the centres of effort was 5.5 feet per second, and the radius of the centres of effort was 3.75 feet. When the wing stroke was made through 90 degrees, the down beat therefore occupied more than one second, and when the stroke was through 120 degrees nearly 1.5 seconds were required to complete it, and just as much more time to raise them. This is leisurely work indeed. It is plainly perceptible that during steady
flight no variation of the supporting power is visible, although if it varied much the bird should certainly drop by gravity through a considerable distance during the 1.5 seconds required to elevate the wings if support depended on the reaction due to the previous stroke. Again, because their under surfaces are held that in the fore-and-aft direction, there can be no air compression under the wings and therefore no support from that source. It has been shown above that considerable air rarefaction must exist over the wings while the bird is moving at good speed, and it has also been shown that the degree of rarefaction required for complete support is that required to produce a compensating pressure under the wings of only one-fortieth pound per square inch, equal to only sixty-nine one-hundredths of one inch water pressure.
    This evidence clearly leads to the conviction that the chief and almost the only source of support during steady flight is air rarefaction over the bird's wings and tail.
    This support is constant during flight whether the wings are rising, descending, or extended in soaring.
    There is very little less lift from rarefaction of air when the wings are rising than while they are descending, because the bird's horizontal speed is about 9 times greater than the vertical speed of the centres of effort.
    It has been observed that in windy weather the bird seldom beats its wings, but swings in curves and circles, the plane of the wings, or rather the transverse axis through the body and wing tips, constantly changing its inclination to the horizon in every direction, chiefly sidewise. It is evident that the descending wind can always exert propelling force when the tail and rising wing are employed to throw the bird's momentum on the descending wing, which will probably be found to be the outer wing in the curve around which the bird is circling.
    Some observers notice that in a wind requiring close reefed topsails, that is, in a gale, the albatross does not soar continuously, but makes an occasional wing beat, evidently to maintain the speed necessary to hold the minus pressure or rarefaction that affords support.
    A captured albatross liberated in mid ocean from the stern of a steamer extended its wings in its descent and, not touching the water soared away without making a single wing beat while it remained visible. The available energy for this performance was obtained from the bird's weight of say 20 pounds, falling possibly 30 feet, 20 x 30 equals 600 foot pounds..


    It may be noted that the angle of inclination of the wings during beating flight must not be considered in reference to the horizon, but to the resultant direction of air streams intercepted at any point in the wing in connection with the wing's motion.
    All soaring birds are admirably fitted for the development and maintenance of minus pressure over their wings. They have to do little else during flight than to keep the air pumped out that happens to leak upward through their wings, or endwise from their inner ends, into the places where defective pressure must be maintained
    The work of propulsion is, on account of their practically perfect shape and surface, reduced to the work of overcoming air friction against their bodies and wings, and that is almost below calculation.
    Humbolt, Darwin and other naturalists noticed that the large vultures generally began their flight by launching themselves from an elevated position, extending their wings during a short descent evidently made to acquire the velocity necessary to establish defective pressure, and then soar in circles, curves and reverse curves until they disappeared beyond some neighboring elevation, or by gradually rising until they passed beyond the range of vision.
    The reverse method was adopted when alighting. The bird approached its resting place at a lower level. When it came near enough it turned upward and arose until its energy of motion was nearly absorbed. If any remained when alighting it was checked by a few vigorous wing beats against the direction of motion.
    An interesting observation of sparrows trying to rise vertically in a fence corner will help support the views set forth above regarding the forces utilized in bird flight.
    The bird's body was vertical in each case and the wings vibrated almost horizontally, but at much higher speed than in ordinary flight.
    It was very plain in the shape of the blurred stroke made by the rapidly moving wings that the tips of the primary feathers reached nearly two inches higher at the ends of the strokes than they did at half-way when moving forward and backward.
    Fanning the air they were for certain and fanning it hard, with the fronts and backs of the wings alternately, having positive pressure on one side and defective pressure or rarefaction on the
other, and the secondary feathers appeared to be doing most of the work.
    The higher speed of beating, when rising vertically, is rendered possible by the shortening of the radius of inertia due to moving the ends of the primaries forward. By raising the wings in this way nearly double power is exerted in equal time, because there is no intermission and on account of the increased speed of beating.
    It is interesting to notice that the sparrow when thus rising vertically moves upward very slowly, certainly not faster than one foot per second, and it is very clear that he is exerting his utmost strength. Yet he often gives up the attempt, especially if the fence happens to be much over 5 feet in height, and he takes risks by attempting to escape in some other direction rather than face the work that he knows is beyond his strength.
    Now if a vertical rise of say 8 feet is beyond the sparrow's strength when he is producing an air reaction on one side of his wings, which, plus the rarefaction on their other sides is only a trifle more than can lift his weight, how very much less must be his work when he is flying horizontally?
    Very clearly the lift due to compression of air under his wings can never come anywhere near equaling his weight. It does not do so when he is making a supreme effort to get over a fence, and in his horizontal flight it can amount to only a small fraction of the equivalent of his weight.
    It will be perceived that in the machine illustrated there can be no intermission in the development of direct reaction, even though that is a matter of little importance, excepting at the times of starting and stopping, when owing to the want of horizontal speed, the intensity of air rarefaction over the wings is much reduced.
                        OF THE MACHINE
Suppose the machine weighs        15 lbs
and that the operator weighs        140 lbs
                                                            155 lbs
    If we take the albatross as our model, the great wing spread of the corresponding machine, more than 20 feet, would render it too unwieldy to be conveniently handled by an individual.
    As we are free to take any other soarer than the albatross for a model, suppose we take the 20 pound California vulture of 8 feet 10 inches wing spread.


    The cube root of 155 divided by 30 equals about 1.72, and this is the dimension ratio. 8.83 x 1.72 equals 15.1876, say 15 feet 2 inches wing spread.
    Proportionate speed for our machine would be as the square root of the dimension ratio, 1.72 equals 1.31.
    Suppose the speed of the vulture is 30 miles. 30 x 1.3 equals would be 39 miles per hour. But because the friction of our machine will be much greater in proportion than the vultures, we must be content with much lower speed, say 30 miles per hour.
    Its wing surface will be in proportion of the square of the dimension ratio, 1.72 D. R. 1,72 squared equals 2.9584 x 7 square feet surface of the vultures wings 20l7088 square feet for the wing sail area.
    The spread of our wings being 15 feet 2 inches, we shall make them 1.25 feet wide, narrower in proportion than the vulture’s, which will give about 18 square feet surface per pair and 36 square feet surface in two sets of wings.
    The radius of the centre of effort of each wing will be 5.687 feet.
    The weight divided by the radius of the centre of effort, 155 divided by 5.687 feet equals 27.25 lbs. at the two centres of effort of the two descending wings, and say 13.6 lbs. at the centre effort of each wing.
                THE TOTAL WEIGHT

    Weight 155, divided by radius of centre of effort, 5.687, equals 27.25 lbs. pressure to be exerted at both centres of effort together, and 13.6 lbs. on each sail.
    The area of each sail is 9 square feet.
    13.5 divided by 9 equals 1.51 pounds per square foot. Square root of 1.51 x 200 equals wind speed to give this pressure, xxxx equals 17.38 miles per hour, equals nearly 25.5 feet per second. This 25.5 feet per second is the speed of the centre of effort during the initial strokes when the machine is starting.
    The length of the circular arc described be each centre of effort during the first down beats is 11.9 feet. 11.9 divided by 25.5 equals 0.45 seconds per down beat. That is, the first down beat should be made in a trifle less than one-half second.
    This is the same as the work that a man would perform in running up a short stairway at the rate of 4.48 feet per second and carrying a weight of 15 pounds on his back. This is nearly equal to running up eight steps per
second, taking two steps at a time. But this hard work would continue for only a very few seconds because air rarefaction over the wings due to speed of translation begins immediately and increases very rapidly until only propelling force is required, the weight of the machine and operator being taken by the positive pressure due to air rarefaction, as in the case of the albatross cited above.
    This also represents the work to be done in starting from the level, the most difficult condition. Should the start be made from an elevation so that a descent for the purpose of acquiring speed would be possible, the initial work would be greatly reduced.
    Starting in a 20 mile head wind would take 72 pounds off the total weight to begin with. In a very few seconds the speed would increase to 29.3 miles, when rarefaction would support the total weight.
    It was shown above that in the case of the albatross travelling 35 miles per hour, equals 51.33 feet per second, that the total energy exerted by the bird in order to support its weight and to maintain its speed was represented by a total air reaction of 0.386 foot pounds per second.
    It is reasonable to assume that the vulture, being as clever a soarer as the albatross, will require, to develop energy at the same rate power only in proportion to its weight. Its weight being 50 percent greater than that of the albatross by that proportion.
    0.386 x 1.5 equals 0.552 feet pounds per second. This represents the work of the vulture during ordinary flight.
    Our machine being 1.72 times larger lineally, will require 1.72 cubed times more power for steady flight. 1.72 cubed equals 5.166.
    But even though we may be able to construct the wings of our machine so those of the vulture, yet it does not appear to be possible to provide that both the operator and the body of the machine can be so arranged and covered by smoooth surfaces that their friction can be reduced to anything near what would compare with that of the bird, bearing in mind that if they were equally frictionless the proportion would be as the square of the lineal dimensions, that is, 2.9 times, say 3 times greater.
    It will be reasonable and safe therefore to provide that the operator must develop say 10 times more work per second than the preceeding calculations call for 2.85 feet pounds per second x 10 equals 28.5 feet pounds per second.


    Let us compare this with the ordinary work of a laborer working 10 hours per day. He exerts continuously, while working, one-eighth to one-tenth horse power. One-eighth horse power equals 550 divided by 8 equals 68.7 foot pounds per second, and one-tenth horse power equals 55 foot pounds per second.
    But our machine should require only 28.5 foot pounds per second, that is, about one-half the work of a laborer.
    A man walking at a moderate rate of speed, say 3 miles per hour, does work equal to lifting his weight through one-twentieth of the distance he travels in any given time. At 3 miles per hour he travels 4.5 feet per second.
    4.5 divided by 20 equals 0.225 feet per second. 0.225x155 pounds equals 34.875 foot pounds per second.
    But the work of propelling our machine through the air at a speed of 30 miles per hour cannot exceed 28.5 foot pounds per second, which is much less than the work a 155 pound man does in walking 3 miles per hour.
    It appears to be clear that both the weight of our machine as well as its speed may be greatly increased before we reach the limit of work done for 10 hours daily by an ordinary day laborer.
    Of the two kinds of apparatus which thus far have been proposed for mechanical flight, viz., individual flying machines, operated by muscular energy, and aeroplane machines operated by some kind of engine, or motor, the individual flying machine has been considered worthy of consideration before the other kind because even though it will be much inferior to engine driven aeroplane machine in speed, radius and carrying power, yet it will be incomparably more important because neither machinery nor fuel will be required, thus eliminating the risks of disabled engines and failure of fuel supply. It will also be safe and simple in construction and operation, smaller and lighter, always available because it will require no supplies and always ready for instant use.
    After the first necessarily crude and imperfect machine has demonstrated its practically, we may look for their rapid development in simplicity and efficiency, as well as reduction of cost that will place them at everybody’s service. It is evident that a machine constructed of Krupp steel in suitable forms can be built of equal strength and of much less than one-half of the weight of an effective machine of the materials now available.
    For example, the 36 pound machine referred to above employs heavy cast iron gears, steel parts that in places are much too heavy, and aluminum in unsuitable sizes in many cases.
    As practicable machines of both kinds would be invaluable in warfare, it is only simple justice to humanity to prevent any military power from “cornering,” or monopolizing their use by thus placing it in every one’s power to construct and develop them unhindered.
    Having practically emptied the bag of mysteries that for ages have hindered the development of winged flying machines we shall now consider the much simpler problem of engine operated aeroplanes.
    This is a simple matter in comparison with winged flight, because there are practically no mysteries to be encountered, nothing in fact in the shape of a serious difficulty, not even excepting the “serious problems of stability and balancing.” of which we are warned by some investigators, especially in the case of our machine encountering vertical air currents.
    Regarding the difficulties of stability and balancing, there is no difference in these things between aerial machines and submarine boats. Both cases are exactly similar in the essential requirements that the centre of gravity must be maintained unchangeably in one position and that it must be held unalterably under the centre of support, or buoyancy.
    The centre of resistance must also be approximately opposite the point at which the propulsive power is applied, although when rudders are employed, this matter is mot of much importance. That it is essential that the relative positions of the centres have no tendency to change unexpectedly.
    Regarding the dangers of vertical currents. They exist in water as well as in air, yet in the hundreds of dives I made in my first four submarine boats in the Passaic River, and at many points in New York harbor between Hoboken and Sandy Hook, in all kinds of weather and in all stages of the tides, I never noticed any disturbance of movement, or other perceptible effect, from them. In fact while closed up in the moving boat there was no evidence of their existence.
    The reason is clear. The horizontal speed of the moving boat is so much greater than the vertical speed of the current that the latter makes the impression on the trim, or on the direction of motion.


    Why should there be any difference in the case of machines floating and moving in air?
    This objection cannot be dignified by calling it a mystery. It is merely one of the “ghosts” conjured up by some people by way of excuse for failing to understand the case.
    This will be rendered clearer by considering the cases of instability cited by those who believe that both aerial machines and submarines are equally liable to dive uncontrollably.
    The case of Lillienthal has already been explained.
    The case of the aeronaut who was killed last summer in San Francisco by falling with his broken aeroplane some 2,000 feet was in no way similar to Lillienthal’s case. The San Franciscan aeronaut caused his aeroplane to dive downward edgewise, at a very steep angle in order to acquire the velocity necessary for maneuvering.
    After having acquired high velocity in his descent of some hindreds of feet he steered his machine to move horizontally. The great moving inertia due to the velocity of his descent was thus suddenly thrown on his wing arms, and because they were very far from being strong enough to endure the excessive sudden strain, they gave way, and the aeronaut with his broken machine was precipitated to the earth.
    The submarine catastrophes cited are those of the English A8 [June 1905] and the French Farfadet.
    It is remarkable that the eminent gentlemen who discoursed before the English Society of Naval Architects, last summer, on the cause of the loss of these vessels attributed it to the untimely and improper use of the diving rudder instead of noticing what was clear to almost everyone else. These same gentlemen alluded to the fact that in the case of A8, the main water ballast tank, of 15 tons capacity was practically filled at that time by 9 tons of water, leaving 6 tons of empty space.
    The captain of the trawler - to avoid ramming, which at high speed the A8 turned rapidly to pass under the trawler’s stern - testified that as the submarine moved around the curve she laid down on her side forcing her conning tower under water, through the open hatch, on the top of which the water poured, causing the boat to go down by the head and disappear. The centrifugal force due to the boat’s rapid motion in a circular curve caused the water in the tank to move to the opposite of the curve and upset the boat.
    Farfadet was practically similar, excepting that in her case there occurred a change of speed or inclination that caused the water in her partially filled tank to move to her forward end, thus causing the common centre of gravity of the boat, and the water in its tanks, to move far enough forward to force the forward to force the forward part of the boat under water. This unexpected manoeuvre, combined with her speed, forced the top of her turret under and she took enough water on board to send her to the bottom.
    Evidently, it is an important, yet a very simple matter, that the centre of gravity of both aerial machines and submarines should be held immovably in one place, and that these centres should be at a sufficient distance beneath, exactly beneath, the centre of support or buoyancy.
    It will surprise most people interested in aeronautics to learn that the practicability of flight with engine-driven aeroplanes was demonstrated beyond question over 13 years ago by Mr. Phillips, a distinguished English military officer, although for some reason he did not sppear to appreciate his own work nor follow the plain course which his success clearly indicated.
    As far as my knowledge extends he was the first, or one of the first, to attach importance to sir rarefaction over a bird’s wings, and to direct attention to the fact that the albatross’s wings are held flat in the fore-and-aft direction when it soars horizontally. See Engineering, London. August 14, 1885, and March 10 and May 5, 1903.
    Mr. H. C. Vogt explained the function of air rarefaction on the lee side of ship’s sails, and the forward faces of the blades of air propellers, in Engineering, London, August 14, 1885, and September 22 1888, but no one, so far as I am aware, even suspected that air rarefaction over a bird’s wings, instead of merely being a help or even a considerable help, as Philips believed, was the main factor, in fact almost the only source of support for all flying animals, when they are in full flight.
    Thirteen years have passed since Mr. Philips proved the practicability of aeroplane flight, not by causing his apparatus to lift itself with a man to direct it, but by proving that a certain area of aeroplane surface, even though unsuitably arranged, did actually lift about 39 per cent more total weight than anybody up to that time, including all the authorities would admit to be within the range of possibility.


    His machine was not quite parge enough and the power was inadequate. Nor is it probable that he expected that it would lift himself, but that same machine would have given much better results had there not existed certain defects in the design that prevented the presence of the degree of rarefaction, and consequent, lifting power that wold have been attainable had these defects been eliminated. The vertical supports for his aeroplanes were nicely arranged to conduct air from above into the palces where, with proper precautions, a much more intense degree of rarefaction would have existed.
    The important point that his experiment developed was that, with suitable conditions, some other force besides those recognized by the authorities was in action, and in effective action, although he failed to fully appreciate it.
    Had his machine been a little larger, with about double the power provided, even of the same unsuitable, heavy kind, he could certainly have flown in the air, and he would not have been compelled to wait as long as I did, 20 years, after providing the first successful submarine boat, before the value of his invention was even partially recognized.
    Mr. Philips’s machine is described in Engineering, London, March 10 and May 8 1893.
    It consists of a Venetian blind shaped frame containing 50 slats or “sustainers” 1½ inches wide and 22 feet long, fitted 2 inches apart in a frame 22 feet broad and 9 feet 5 inches high. The sustainers had a combined area of 136 square feet: they were convex on the upper surface, and concave below, the hollow being about one-sixteenth inch deep.
    The frame holding the sustainers is set up in a light canoe-shaped carriage, composed principally of two bent planks like the two top streaks of a whale boat, and being 25 feet long and 18 inches wide, mounted on three wheels 1 foot in diameter, one in front and two at the rear.
    This vehicle carries a small boiler with a compound engine, which works a two-bladed aerial screw propeller revolving about 400 times per minute.
    The fuel is Welsh coal. There is said to be no attempt to provide exceptionally light machinery. The weights of the various parts of the machine are, approximately, carriage and wheels, 60 pounds. Machinery with water in boiler and fire in grate, 200 pounds; sustainers, 70 pounds; total weight, 330 pounds.
    The machine was run on a circular path of wood with a circumference of 628 inches (200 inches diameter), and to keep it in position (preventing erratic flight) wires were carried from various parts of the machine to a central pole.
    Still further to control the flight, which there is no means of guiding, the machine is not of sufficient size to carry a man, the forward wheel is so balanced that it never leaves the track, and therefore serves as a guide, carrying some 17 pounds of the weight, the remainder being on the hind wheels.
    On the first run 7.2 pounds dead weight were added, making the total lift 402 pounds. As soon as speed was gotten up and when the machine faved the wind the hind wheels rose some two or three feet clear of the track, thus showing that the weight was carried by the air upon the Venetian blind sustainers. A second trial was made with the dead weight reduced to 16 pounds, and the circuit was made a 28 miles per hour(2.464 feet per minute), with the wheels clear of the ground for about three-fourths of the distance. That the machine can not only sustain itself, but an added weight, was demonstrated beyond all doubt, even under the disadvantage of proceeding in a circle, with the wind blowing pretty stiffly.
    It is possible that Mr. Philips was discouraged by the opinions of of those persons who “proved” that for successful flight an engine was required which, with its supply of coal and water for even a brief performance, should weigh no more than 5 pounds per horse power, whereas available engines weighed many times more than 5 pounds per horse power and more probably 60 pounds, but apparently he was not aware of the existence, at the time he made his experiment of the internal combustion, hydrocarbon engine that need not have weighed more than one-fifth of the weight of his motor, with its supplies. A specially designed Brayton engine would have suited the work fairly well. At the present day we can avail ourselves of the wonderful development of automobile engines, due chiefly to the genius of French men, and of the comparably better material for both machine and motor that is now available. We have also discovered that the threatened dangers and difficulties of aerial navigation are choefly imaginary and that actual flight whether of bird like machine or aeroplane, instead of being a complex problem to be approached cautiously and carefully, is, in fact, simplicity itself.


    Having already described and illustrated an apparatus for birdlike flight, we may now consider designs for an aeroplane machine to be operated by an automobile engine, not a specifically built engine, but one of the ordinary kind, weighing say 9 pounds per horse power. Successful engines have been built less than one-third of this weight, but we shall act wisely in considering nothing that is special and expensive, but only the kind that is already well tried and in every day use. We shall design our machine and examine it carrying power and endurance and radius of action. The necessary lifting power is the first point of consideration and it may be noted that opinions differ a good deal regarding what one horse power can lift with the aid of a suitable air propeller. The estimates vary between 35 pounds and 85 pounds, depending on the perfection of the apparatus and whether the experimenters took the vertical movement of their apparatus into account, but it is generally recognized that one horse power can balance 60 pounds weight when there is no vertical movement of the machine.
    Messrs. Dahlstrom and Lehman, engineers, Copenhagen, in September, October and November 1887, experimented with propellers working in air and operated by the engines of a launch which was also fitted with a propeller in the ordinary position, working in the water, when a comparison of the relative efficiency of the propellers was required. They concluded that when the air and the water propellers were similar in the proportion of pitch to diameter, with proportionate surface, that the air propeller should have about five times the diameter of the propeller working in the water in order to obtain the best results. They found further that when each propeller was driven at exactly the same speed of revolution of the other, and by the same engine, that the thrust exerted by the air propeller slightly exceeded the thrust delivered by the propeller working in the water. The air propeller was of light material. The water propeller was of ordinary metal construction.
    Therefore our air propellers may be expected to afford 60 pounds lift without ascensional speed and that the weight lifted will be decreased as the vertical speed increases.
    We shall design our machine practically on the same model as the one described in Cassier’s magazine, New York, February 19, 1893, provide it with a 25 horse power automobile engine, which will afford a total lifting power, at 40 pounds per horse power, of 1,000 pounds, leaving a margin of 20 pounds per horse power, equals 500 pounds for ascensional power.
    In the design for an aeroplane machine as illustrated, the aeroplanes are set in a frame so as to resemble a great Venetian blind, which is pivoted at the middle of its vertical length in order that it may be set vertically or horizontally. When the machine is at rest, the aeroplane frame lies horizontally, having the axis of the two propeller wheels shown standing vertically. The propeller wheel bearings are carried at the ends of a trussed frame that forms part of the aeroplane frame structure, this trussed beam being carried on bearings at the tops of two connected A frames that rise from the body or car of the machine.
    The body, or car, rests on three wheels, two forward and one aft, under the floor of the car. The after wheel is adjusted on a vertical spindle so that is may serve to steer the machine when it moves on a roadway.
    When the machine starts on its aerial trips, the aeroplane frame lies horizontally and both propeller shafts stand vertically.
    When they are revolved rapidly, with the full power of the engine, the machine rises slowly in the air, and it must be permitted to rise until it has attained an elevation sufficient to be clear of all obstructions.
    The aeroplane frame is then slowly revovlved on its horizontal axis, thus inclining the axis of the propeller wheels towards the horizontal, and reducing their lifting power. When the inclination reaches about 45 degrees the lifting power of the propellers will be sufficient to balance the dead weight of the machine, and the aeroplanes then coming into action, will develop a lift depending on the speed of the machine.
    Mr O. Chanute’s tables indicate that at an inclination of 45 degrees of the aeroplanes the lift and drift force are each two-thirds of the total pressure. Therefore at this inclination the drift force applied will develop a considerable lifting force, by meanis of the aeroplanes . But two-thirds of the total lifting power of the engines and the propellers are competent to balance the total weight with out the aid of the aeroplanes. At the same time they develop a lift depending on the speed with which they are moved horizontally.
    It follows that the machine would continue to rise if held under these conditions, but when a great elevation is not required the operator will continue to raise the aeroplane frame until it stands vertically and all the weight is carried by the planes. The propellers and engines will not then be required to do any lifting, but only to exert what power as may be required for propulsion.


    When the operator desires to alight, he will simply reverse this operation, and because the speed of the engines will be under control he can hold his machine still in space, whether in a calm or in a storm, and also alight without shock.
    It therefore appears reasonable to expect that, possessing the power to obtain horizontal motion as soon as obstructions are cleared, and to face the wind, that the course of the machine in rising would be vertical, should there be any wind blowing and then quickly changing to horizontal motion in the direction the operator desires, and that the trace of his course when alighting, if exhibited on a chart, would be exactly similar, but in the reverse direction, facing the wind if any exist, during his descent.
    The speed of the machine required when the planes afford full support, at say 6 degrees elevation, may be determined thus:
    Total weight,  1,000 pounds.
    Total plane surface,  500 square feet.

    1,000 pounds divided by 500 equals 2 pounds lift per square foot. Proportion of lift at 6 degrees elevation equals 0.206, proportion of drift at 6 degrees elevation equals 0.0217; 1,000 pounds weight divided by 500 square feet equals 2 pounds per square foot lift wanted: 2 divided by 0.206 equals 9.7 pounds wind pressure. And this pressure is exerted by wind at 44 miles per hour. The drift force required for 500 square feet of aeroplane at 6 degrees inclination, equals 500 x 0,0217, equals 10.85 pounds. Add 50 per cent of this for friction of frame and body of car, 10.85 x 1.5 equals 16.275 pounds total drift force.
    Speed required to afford 2 pounds per square foot lift equals 44 miles per hour, equals 64.53 feet per second. 64.53 x 16.275 equals 1.050 foot pounds per second? 1.050 divided by 550 equals 1.727 horse power.
    This calculation shows that when the machine is travelling through the air at a speed of 44 miles per hour, having the aeroplanes inclined 6 degrees to the horizon that the actual propulsive power employed will amount to only 1.724 effective horse power. But engines of 25 horse power are provided, that is, 14 times more power than will be required at 44 miles speed.
    The speed being in the proportion of the cube root of the power employed, cube root of 14.21.1 x 44 miles equal xx miles speed if the friction of the car and frame increases only in the same proportion as the drift force. But as it is probable that it will increase more rapidly the speed with 6 degrees inclination of the aeroplanes will be reduced from 105 miles possibly to 100 or even to 95 miles per hour.
    But it was shown above, when considering the bird like machine, that 17 inclination of the albatross’s wings xx they are inclined could not have been greater than 45 minutes of arc. Therefore, it follows that 100 miles per hour is by no means the speed limit of the aeroplane.
    We may now consider its radius of action when carrying only the weight of oil fuel, mentioned above, 150 pounds.
    For the work of direct lifting 15 horse power is required, but for horizontal motion at a speed of 44 miles per hour it has been shown that only 1.7 horse power will be exerted continually.
    When the engines are developing their full power, 15 horse power, they are working under the most economical conditions and they require only one-tenth gallon of oil fuel per horse power, per hour, but when they are eveloping only 1.7 horse power they do not work nearly so economically, requiring under those conditions about one-fourth gallon per horse power per hour.
    The quantity of oil provided was 150 pounds weight, equals 20 gallons.
    1.7 horse power x 0.25 equals 0.425 gallons per hour; oil carried, 20 gallons divided by 0.425 gallons equals 47 hours supply of oil fuel.
    47 hours x 44 miles speed equals 2,058 miles radius at 44 miles speed that is our machine could start from one of the explorer’s stations in Northern Greenland, pass over the North Pole and return, photographing everything on the way, or it could in one trip cross the Atlantic Ocean between St. John’s New Foundland, and Ireland.
    When the machine starts from a level road along which it can run at good speed much more elevating power will be developed than when operated as described above, but the aeroplanes must be inclined at a greater angle than 6 degrees.
    Suppose they are inclined at starting say 20 degrees from the horizontal position by inclining the plane frame 20 degrees from the vertical position.
    The proportion of drift force for 20 degrees inclination is 0.228. Add one-third to this for resistance of car and frame.


    0.228 plus 0.076 equals 0.304 lbs. drift per square foot.
    0.304 x 500 square feet of aeroplane surface equals 152 pounds total drift force.
    The engines are of 25 horse power, equals 13,750 foot pounds per second.
    13,750 divided by 152 equals 90.46 feet per second, equals 61.67 miles per hour. This speed affords a wind pressure of 19 pounds per square foot.
    The proportion of lift for 20 degrees inclination is 0.515, 19 x 0.515 equals 9.785 lift per square foot.
    9.785 x 500 equals 4.8925 pounds total lifting power. If 2,000 pounds of this force be applied to direct lifting, the remainder will be ascensional force.
    By adopting this method of rising it is also evident that a much greater weight can be lifted and carried than by employing the method of direct lifting. Travel over a long distance will reduce the weight of oil fuel. Some things such as mail bags, may be dropped without infuring them, or by employing small parachutes, but unless the operator is favored by a strong wind against his direction of motion, when alighting, or by a convenient smooth surface of water, or an asphalted road, it will be difficult to come to rest without shock if the total weight be not reduced to about what the engines and propellers can hold suspended in the air, probably 24 x 60 pounds equals 1,500 pounds.
    The purpose of this paper being to present reasons for believing in the posibility of mechanical flight and to illusrate them with designd for two setsof apparatus which appear to be practicable, even though like most new things, they will almost surely, in time prove to have been only crude attempts, it will not be necessary to give more detail than is required to suggest means detail than is required to suggest means and methods to the engineers, who will soon accomplish their complete development and place at our service Nature’s great highway, the atmosphere.

Holland, John P.,"How to Fly Like a Bird," Newark, NJ: Gasser Print Shop, n.d. [ca. 1906].