A Project for Flying. 

In Earnest at Last!

1871

Price, TWENTY-FIVE CENTS. 

A Project for Flying. 

In Earnest At Last. 

The following appeared in one of our public journals of the dateindicated

_To the Editor of the Tribune. _

SIR:--You rightly appreciate the interest with which the popularmind regards all efforts in the direction of navigating the air. 

One man of my acquaintance was deeply interested to know theresults of the California Experiment, because he alone, as he believed, had questioned Nature and learned from her the great secret of aerialnavigation. 

To-day's _Tribune_ brings us the full account of the machine, itsperformance and _modus operandi_; and without the authority of myfriend, I can pronounce at once that the thing is simply ridiculous. It isthe same old useless effort, with the same impossible agents. But to-day, within twenty miles of Trinity steeple, lives the man who can give tothe world the secret of navigating the air, in calm or in storm, withthe wind or against it; skimming the earth, or in the highest currents, just as he wills, with all the ease, and all the swiftness, and all theexactitude of a bird. 

My friend is only waiting for an opportunity to perfect his plan, whenhe will make it known. 

Yours truly, W. H. K. 

_New York; June 14th_, 1869. 

Two years have passed and no progress has been made in aerialnavigation. 

The California Experiment failed. The great Airship "CITY OF NEWYORK, " had previously escaped the same fate, only because more prudentthan her successor she declined a trial. The promising and ambitiousenterprise of Mr. Henson has hardly been spoken of for a quarter of acentury. And notwithstanding the fact that the number of ascensions inballoons in the United States and Europe must be counted by thousands, and although the exigencies of recent wars have made them useful, yetit must be confessed that the art of navigating the air remains inmuch the same state in which the brothers Montgolfiers left it at theclose of the last century. 

The reason for this want of progress in the art referred to, is not tobe sought in any want of interest in the subject, or of enthusiasm inprosecuting experiments. Certainly not for want of interest in thesubject because _to fly_, has been the great desideratum ofthe race since Adam. And we find in the literature of every agesuggestions for means of achieving flight through the air, inimitation of birds; or for the construction of ingenious machines foraerial navigation. And if history and traditions are to be credited, it would be equally an error to suppose that our age alone hadattempted to put theory into practice in reference to navigating theair. 

Even the fables of the ancients abound with stories about flying: thatof Dedalus and his son Icarius, will occur to every reader. And therepresentations of the POETS, and the allusions in HOLY WRIT equallyprove how natural and dear to the mind of man is the idea ofpossessing "wings like a dove. "

But it is safe enough to assert, that hitherto, all attempts at_navigating_ the air have been failures. 

Floating through the atmosphere in a balloon, at the mercy not only ofevery _wind_ but of every _breath_ of air, is in no adequatesense aerial navigation. And I do not hesitate to say, that balloonsare absolutely incapable of being directed. 

All the analogies by which inventors have been encouraged in theirexpectations are false, the rudders of ships and the tails of birdsare no exceptions. They will never be able to guide balloons assailors do ships, by a rudder, because ships do not float suspendedin the water as balloons float in the air; nor do birds _float_through the air in any sense. They are not bouyant--lighter than theelement in which they move, but immensely heavier; besides they do notguide themselves wholly by their tails. We may depend upon it, if weever succeed in navigating the air, it will be by a strict adherenceto the principles upon which birds fly, and a close imitation of themeans which they employ to effect that object. 

It is true, that in respect to the means to be employed, animalsdesigned by the Creator for flight, have greatly the advantage of us, but what natural deficiencies will not human ingenuity supply, andwhat obstacles will not human skill overcome? It has already triumphedover much greater than any that Nature has interposed between man andthe pleasures of aerial communication. 

We have to a great extent, mastered the mysterious elements of nature. 

We have conquered the thunderbolt and learned to write with theburning fluid out of which it is forged. 

We have converted the boundless ocean into a vast highway, traversedfor our use and on our errands, by the swift agent, and by great shipsdriven against wind and tide by the mighty power of steam. 

And yet a single generation ago, we knew nothing of all this, Ourgrand-sires would have given these achievements a prominent place inthe list of impossible things. 

But, do you say, "the Creator never intended us tofly--_therefore_, it is impossible. "

For what did the Creator give us skill and boundless perseverance?Was it designed that we should _swim_, more than that we shouldfurnish ourselves with wings and mount up as eagles? "We sink likelead in the mighty waters, " we only fall a little faster through theair. 

Still, I grant that the problem of aerial navigation will only besolved when the principles of flight are clearly understood, and werecognize precisely what are the obstacles which prevent us fromflying by artificial means. 

Will these obstacles prove insuperable? It is at present believed bythe multitude that they will, but I entertain a different opinion, most decidedly. 

From my earliest youth this subject has occupied my thoughts. Ithas been the study of my life, and I modestly trust that I have notquestioned nature and science in vain. 

In the first place, I undertook to make myself familiar with theobstacles to be overcome. I found the greatest of these to be gravity. I found, however, that heavy fowls, who were unable to rise _fromthe earth_, and only accomplished flight by taking advantage of aneminence, sustained themselves without difficulty when once fairlyembarked. I also found that the best flyers were not equal to the featof keeping me company, when walking at my usual pace; hence I inferredthat _velocity_ was a necessary element in flight, and thatgravity, so fatal to human attempts to fly, might be made a powerfulauxiliary when rightly used. 

Acting upon this hint, I made experiments with heavy barn yard fowls, and finally constructed a light apparatus to be operated by myself, using, principally, my feet as a motive power, which I repeatedlytried with various and _constantly increasing_ degrees ofsuccess. 

Now I am satisfied that my system is right. It is my sober convictionthat the time to realize the dream and hope of ages has come. Startling as the announcement may be, I propose not only to make shortexcursions through the air myself, but to teach others to do the same. 

Yet, knowing perfectly the obstacles in the way of flight, and knowingequally well how to overcome them, I am yet well aware that I mustperfect my knowledge by practice before entire success can beachieved. 

This is only reasonable. 

How was it with the swimmer; how was it with the agile and dexterousskater; how with the acrobat, and what but practice has just enabledWESTON to walk one hundred and twelve miles in twenty-four hours, andfour hundred miles in five days?

For want of a better name, I will call the machine upon which I am topractice, the "Instructor. " It is simple, but it gives the learnerjust what he wants--an endless series of _inclined planes_. 

It will prevent accidents, and until the student has mastered themechanical movements necessary to flight, will supplement his effortsby partially balancing his weight. 

It consists of a beam fifty feet long, poised and attached by auniversal joint to the top of a form post, say twenty feet or more inheight. Upon one end of this beam the practitioner stands, arrayed inhis wings. A movable weight at the other end completes the apparatus;and yet this simple machine, will form the entering wedge to aerialnavigation. 

And now methinks I see you smile, but, my unbelieving friends, let meremind you that COPERNICUS, and GALILEO, and FRANKLIN, and FULTON, and MORSE, --all better men than your humble servant, were laughed atbefore me. 

_Their_ work is done. Their monuments stand in all lands, and yet_one_ of this band of truly great and worthy names still lives, and to him I am indebted for many kind and encouraging words. 

It is little besides this that I ask of _you_. The stock whichyou are solicited to take in this enterprise is small. But enable meby your patronage to devote myself for a time wholly to my project. See to it, that I do not fail for want of support. Buy my littlepamphlet at its insignificant cost, ask your friends to do so; andshould any of you wish to contribute anything more to this cause, which I have made my own, and which I am determined to push toa triumphant issue, he may be sure that he will receive theacknowledgments of a grateful and earnest man, who has himself devotedto it the aspirations and efforts of a long life, and who is stillwilling to take all the risks of failure upon himself. 

The undersigned would be pleased to have friends interested in thissubject, call upon him, when the matter will be more fully described. 

ROBERT HARDLEY, 17 PERRY STREET, or

114 Sixth Ave. , cor. 9th St. 

[Illustration: THE AERIAL MACHINE. ]

REMARKS ON THE ELLIPSOIDAL BALLOON, PROPELLED BY THE

_Archimedean Screw_, DESCRIBED AS THE NEW AERIAL MACHINE, NOW EXHIBITING AT THE ROYAL ADELAIDE GALLERY, LOWTHER ARCADE, STRAND. 

REMARKS, &c. 

The object proposed in the construction of the Machine which is herepresented to the public view, is simply to illustrate and establishthe fact, that, by a proper disposition of parts and the applicationof a sufficient power, it is possible to effectuate the propulsion orguidance of a Balloon through the air, and thus to prepare the way forthe more perfect accomplishment of this most interesting and desirableresult. 

In the contrivance of this design, one of the first effects aimedat was to reduce the resistance experienced by the Balloon in itsprogress, which is greater or less according to the magnitude andshape of its opposing surface. To this intent is the peculiar_form_ of the Balloon, which is an _Ellipsoid_ or _prolatespheroid_, the axis of which is twice its minor diameter; inother words, twice as long as it is broad. By this construction theopposition to the progress of the Balloon in the direction of eitherend is only one _half_ of what it would be, had it been a Balloonof the ordinary spherical form and of the same diametrical magnitude. For the exact determination of this proportion we are moreparticularly indebted to the researches of Sir George Cayley, adistinguished patron of the art, who, a few years back, instituted aseries of experiments with a view to ascertain the comparative amountsof resistance developed by bodies of different forms in passingthrough the air; the results of which he communicated to the world inan essay first published in the Mechanic's Magazine, and afterwards ina separate pamphlet. According to these experiments it appears, thatthe opposition which an ellipsoid or oval (of the nature of theBalloon, if we may so call it, in the model) is calculated toencounter in proceeding _endways_ through the atmosphere is only_one-sixth_ of what a _plane_ or _flat_ surface of equal area with itslargest vertical section, would experience at the same rate; while theresistance to the progress of a globe, such as the usual Balloon, wouldbe one third of that due to a similar circular plane of like diameter:shewing an advantage, in respect of diminished resistance, in favour ofthe former figure, to the extent we have above described; an advantage itenjoys along with an increased capacity for containing gas--the cubicalcontents of an ellipsoid of the proportions here observed, being exactlydouble of those of an ordinary Balloon of equal diameter, andconsequently competent to the support of twice the weight. 

Independent of the advantage of reduced resistance in this form, thereis another of nearly, if not quite, equal importance, in the facilityit affords of directing its course; an object scarcely, if at all, attainable with a Balloon of the usual description however powerfullyinvested with the means of motion; as any one will readily perceivewho has ever noticed or experienced the difficulty, or rather theimpossibility, of guiding a tub afloat in the water, compared with thecondition of a boat or other similarly constructed body, in the sameelement. The efficacy of this provision and its necessity will appearmore forcibly when we observe that whenever the Balloon in the machinehere described is thrown out of its direct bearing by the shifting ofthe net-work which connects it with the hoop, or by any other accidentwhereby its position is altered with respect to the propelling power, its course is immediately affected, and it ceases to progress in astraight line, following the direction of its major axis, unlesscorrected by the intervention of a sufficient rudder. 

The second object, after establishing a proper form for the floatingbody, was to contrive a disposition of striking surface that shouldbe able to realise the greatest amount of propulsive re-action, inproportion to its magnitude and the force of its operation, which itis possible to accomplish. To shew by what steps and in consequence ofwhat reasoning this point was determined as in the plan adopted, wouldoccupy considerably more space than the few pages we have to sparewould admit of our devoting to it. Suffice it to say that of all themeans of creating a resistance in the atmosphere capable of beingapplied to the propulsion of the Balloon, the Archimedean Screwwas ascertained to be undoubtedly the best. It is true that by a_direct_ impact or stroke upon the air, as for instance by theaction of a fan, or the wafting of any _flat_ surface at _rightangles_ to its own plane, the maximum effect is accomplishedwhich such a surface is capable of producing with a given power. Themechanical difficulties, however, which attend the employment of sucha mode of operation are more than sufficient to counterbalance anyadvantage in point of actual resistance which it may happen topossess; at least in any application of it which has hitherto beentried or proposed: so that here, as in the case of ships propelledby steam, the _oblique_ impact obtained by the rotation of thestriking surface is found to be the most conducive to the desiredresult; and of these, that arrangement which is termed the ArchimedeanScrew is the most effective. 

The result aimed at, being the development of the greatest amount ofre-action in the direction of the axis of revolution, it is not enoughto have determined the _general_ character of the instrumentto be employed; the proper disposition or inclination of its partsbecomes a question of the first importance. According as the_turns_ of the screw are more or less oblique with respect to theair they strike or the axis on which they revolve, more or less of theresistance they generate by their rotation becomes _resolved_, asit is technically expressed, in the direction of the intended course:in other words, converted to the purpose in view, namely, thepropulsion of the Balloon. 

Our limited space here again prevents us from entering into a detailof the experiments by means of which the true solution of thisquestion has been arrived at, and the proper angle determined at whichthe superficial spiral exercises the greatest amount of propulsiveforce of which such an engine is capable. These experiments have beenchiefly carried on by Mr. Smith, the ingenious and successful adapterof this instrument to the propulsion of steam vessels, for a series ofyears, with the greatest care, and at a very considerable expense; andthe result of his experience gives an angle of about 67° or 68° forthe outer circumference of the screw, as that productive of themaximum effect; a conclusion which is further verified by theexperiments of Sir George Cayley, of Mr. Charles Green, the mostcelebrated of our practical aeronauts, and others who have employedtheir attention upon the subject. This conclusion requires only onemodification, which ought to be noticed; namely, that in cases ofextreme velocity, the number of the angle may be still furtherincreased with advantage, until an inclination of about 73° beobtained; when it appears any further advance in that direction isattended with a loss of power. With these facts in view, the impingingsurface of the Archimedean Screw, in the model under consideration, has been so disposed as to form, at its outer circumference, an angleof 68° with the axis of revolution, gradually diminishing as itapproaches the centre, according to the essential character of such aform of structure. 

The novelty of the application of this instrument to the propulsionboth of ships and balloons, suggests the propriety of a few moreexplanatory remarks to elucidate its nature and meet certainobjections which those who are ignorant of its peculiar qualities areapt to raise in respect of it. 

Previous to the adoption of this particular instrument, variousanalogous contrivances had been resorted to in order to produce thesame effects. Of these, examples are afforded in the sails of thewindmill, the vane of the smoke jack, and of more modern introduction, the _propellers_ designed by Mr. Taylor for the equipment ofsteam-boats, and which Mr. Green has availed himself of to shewthe effect of atmospheric re-action in directing the course of theballoon. Now all these and similar expedients are merely modificationsof the same principle, more or less perfect as they more or lessresemble the perfect screw, but all falling far short of the efficacyof that instrument in its primitive character and construction. Thereason of this deficiency can be readily accounted for. All themodifications alluded to, which have hitherto been applied to thepurposes of locomotion, are adaptations of _plane_ surfaces. Now it is the character of _plane_ surfaces to present thesame angle, and consequently to impinge upon the air with the samecondition of obliquity throughout. But the _rate_ of revolution, and consequently of impact, varies according to the distance from theaxis; being greatest at the outer edge, and gradually diminishing asit approaches the centre of rotation, where it may be supposed to bealtogether evanescent. Now it is by the re-action of the air against_one_ side of the impinging plane, that the progressive motion isdetermined in the opposite direction, which re-action is proportionedto the _rate_ of impact, the angle remaining the same. If thenwe suppose a re-action corresponding to the _greatest rate_ ofrevolution, which is that due to the _outermost_ portion of theimpinging surface (that most removed from the axis of rotation) weshall have a _progressive_ motion in the whole apparatus greaterthan the rate of impact of the _innermost_ or more centralportions of the revolving plane; and accordingly the re-action will bethereabouts transferred from the back to the front of the propulsiveapparatus, and tend to retard instead of advancing the progress ofthe machine to which it is attached. This inconvenience is felt andacknowledged by all those who have employed this principle to obtain aprogressive motion, and accordingly a provision has been made againstit in the _removal_ or _reduction_ of the central portionof the revolving vanes, with a view to let the air escape or passthrough as the instrument advances; a provision which is certainlyeffectual to that end, but at the cost of the _surface_, which isthe ultimate source of the required re-action. All this is avoidedin the use of the perfect screw. There, the rate of rotation and theangle of impact mutually corresponding, may be said to play into eachother's hands; the spiral becoming more extended as the impact becomesless forcible, that is as it approaches the centre, where bothaltogether vanish or disappear; thus obviating the possibility of anyinterruption to the course of the machine from the contrarious impactof the air, however quick or however slow the motions, either of thescrew itself or of the machine which is propelled by its operation. Inattestation of this fact and as showing the immunity of the perfectscrew from the disparaging effects experienced by the other modes ofaccomplishing the same object, I will only mention a circumstancerelated to me by Mr. Smith himself, to whom I am glad to acknowledgemyself indebted for so much valuable information respecting thisinstrument, which, by the light he has thrown upon its use and theimprovements he has introduced into its construction, he may be trulysaid to have made his own. Upon a late occasion, when trying one ofthe larger class of vessels which had just been furnished by him uponthis principle, some persons not perceiving the true nature of thefigure employed, contended that some opposition must be experienced bythe central portion of the screw, which revolved so much less rapidlythan the rate of the ship itself. In order to convince them of theirerror, Mr. Smith caused a portion of the surface in question, next theaxis, to a certain distance, to be cut away, leaving an opening, bywhich, for the water to escape. The result was, immediately the lossof one mile an hour in the rate of the ship; thus shewing that eventhe most apparently feeble portion of the impinging surface of thisinstrument contributes, in its degree, to the constitution of theaggregate force of which it is productive. 

This peculiarity of construction is the main cause of the advantagewhich the Archimedean Screw possesses over all its types orimitations; but it is not the only one. The _entirety_ or_unbroken continuity_ of its surface is another, not much lessinfluential. The value of this will be the more readily appreciatedwhen we consider that air, unlike water and other non-elastic fluids, undergoes a rarefaction or impoverishment of density, and consequentlyof resisting power, accordingly as it is swept away by the rapidpassage of impinging planes; the parts immediately _behind_, andto a considerable distance, being thereby relieved from the supportthey had previously experienced, and extending (and consequentlybecoming thinner) in order to fill up the space thus partially clearedaway. Now it is evident that if other planes be brought into operationin the parts of the atmosphere thus impoverished, before they havehad time to recover their pristine or natural density, they willof necessity act with diminished vigour; the resistance being everproportioned to the density of the resisting medium. This is thecondition into which, more or less, all systems of revolving planesare necessarily brought, that consist of more than one; and is agrand cause of the little real effect they have been made capableof producing, whenever tried. The nature of this objection, and theextent to which it operates, will appear most strikingly from thefollowing fact. Mr. Henson's scheme of flight is founded upon theprinciple of an inclined plane, started from an eminence by anextrinsic force, applied and _continued_ by the revolutionof impinging vanes, in form and number resembling the sails of awindmill. In the experiments which were made in this gallery withseveral models of this proposed construction, it was found that so farfrom _aiding_ the machine in its flight, the operation of thesevanes actually _impeded_ its progress; inasmuch as it was alwaysfound to proceed to a greater distance by the mere force of acquiredvelocity (which is the only force it ever displayed), than whenthe vanes were set in motion to aid it--a simple fact, which it isunnecessary to dilate upon. It is to the agency of this cause, namely, the broken continuity of surface, that, I have no doubt, is also to beascribed the failure of the attempt of Sir George Cayley to propel aBalloon of a somewhat similar shape to the present, which he made atthe Polytechnic Institution a short while since, when he employeda series of revolving vanes, four in number, disposed at properintervals around, but which were found ineffectual to move it. Hadthese separate surfaces been thrown into _one_, of the natureand form of the Archimedean Screw, there is little doubt that theexperiment would have been attended with a different result. Inaccordance with the principles here illustrated, the ArchimedeanScrew properly consists of only _one_ turn; more than one beingproductive of no more resistance, and consequently superfluous. Asingle unbroken turn of the screw, however, when the diameter is ofany magnitude, would require a considerable length of axis, which inits adaptation to the Balloon, would be practically objectionable;accordingly _two half turns_, nearly equivalent in power to onewhole turn, has been preferred; as in most instances it has been byMr. Smith, himself, in his application of it to the navigation of theseas, Indeed, in all other respects, except the nature of its material, thescrew here represented is exactly analogous to that used by Mr. Smithin its most perfect form, having been, in fact, designed, and in partconstructed under his own supervision. [A]

The model upon which these principles have been now, for the firsttime, successfully, at least, tried in the air, is constructed uponthe following scale. The Balloon is, as before stated, an ellipsoidor solid oval; in length, 13 feet 6 inches, and in height, 6 feet 8inches. It contains, accordingly, a volume of gas equal to about 320cubic feet, which, in pure hydrogen, would enable it to support aweight of twenty-one pounds, which is about its real power whenrecently inflated, and before the gas has had time to becomedeteriorated by the process of _endosmose_. [B] The whole weightof the machine and apparatus is seventeen pounds; consequently thereis about four pounds to spare, in order to meet this contingency. 

[Footnote A: The frame was made at Mr. Smith's request, by Mr. Pilgrim, of the Archimedes; the original experimental vessel in whichthis mode of propulsion was first tried upon the large scale. Mr. Pilgrim has been long versed in all that relates to the mechanism ofthis instrument, and is indeed a most expert and ingenious artist. ]

[Footnote B: _Endosmose_ is that operation by which gases ofdifferent specific gravities are enabled, or rather forced to cometogether through the pores of any membranous or other flexiblecovering by which it is sought to restrain them. As above referred to, it is the introduction of atmospheric air into the body of the Balloonthrough the pores of the silk, however accurately varnished, by whichthe purity of the hydrogen gas is contaminated, and its buoyant powerultimately exhausted This it is impossible to prevent by any process, except the interposition of a _metallic_ covering; as forinstance, by _gilding_ the Balloon, which would be effectualcould it be contrived to endure the constant friction and bending ofthe material itself. ]

Beneath the centre of the Balloon, and about two-thirds of its length, is a frame of light wood, answering to the hoop of an ordinaryBalloon; to which are attached the cords of the net which encloses thesuspending vessel, and which serves to distribute the pressure of theappended weight equally over its whole surface, as well as to form anintermediate means of attachment for the rest of the apparatus. Thisconsists of a car or basket in the centre; at one end the rudder, andat the other the Archimedean Screw. The car is about two feet longand eighteen inches broad, and is laced to the hoop by cords, whichrunning through loops instead of being fastened individually, allow ofunlimited play, and equalize the application of the weight of the carto the hoop, as of the whole to the Balloon above. The ArchimedeanScrew consists of an axis of hollow brass tube eighteen inches inlength, through which, upon a semi-spiral of 15° of inclination, arepassed a series of radii or spokes of steel wire, two feet long, (thusprojecting a foot on either side) and which being connected at theirouter extremities by two bands of flattened wire, form the frame workof the Screw, which is completed by a covering of oiled silk cut intogores, and tightly stretched, so as to present as nearly uniform asurface as the nature of the case will permit. This Screw is supportedat either end of the axis by pillars of hollow brass tube descendingfrom the hoop, in the lower extremities of which are the holes inwhich the pivots of the axis revolve. From the end of the axis whichis next the car, proceeds a shaft of steel, which connects theArchimedean Screw with the pinion of a piece of spring machineryseated in the car; by the operation of which it is made to revolve, and a progressive motion communicated to the whole apparatus. Thisspring is of considerable power compared with its dimensions, beingcapable of raising about 45 pounds upon a barrel of four inchesdiameter after the first turn, and gradually increasing as it is woundup. It weighs altogether, eight pounds six ounces. 

The rudder is a light frame of cane covered with silk, somewhat of theform of an elongated battledoor, about three feet long, and one footwide, where it is largest. It might be made considerably larger ifrequired, being exceedingly light and yet sufficiently strong for anyforce to which it could be subjected. It weighs altogether only twoounces and a half. This instrument possesses a double character. Besides its proper purpose of guiding the horizontal course of theBalloon, it is capable of being applied in a novel manner to itselevation or depression, when driven by the propulsive power ofthe Screw. Being so contrived as to be capable of being turned_flat_, and also directed upwards or downwards as well as to theright or left, it enables the aeronaut to transfer the resistance ofthe air, which, in any inclined position, it must generate in itspassage, to any side upon which he may desire to act, and thus give adetermination to the course of the Balloon in the opposite direction. This will appear more clear as well as more certain when we consider, that the aerial vessel being in a state of perfect equipoise, asit ever must be when proceeding on the same level, the slightestalteration in its buoyancy is sufficient to send it to a considerabledistance either up or down as the case may be: the rejection of apound of ballast, or of an equivalent amount of gas, being enough toconduct the aeronaut to the extremest limits of his desires in eitherdirection, whatever may be the size of his Balloon. Now a resistanceequal to many pounds is attainable by an inclined plane of evenmoderate dimensions when propelled even with moderate velocity; andbeing readily governed by the mere inclination of the impinging planeat the will and by the hand of the aerial voyager, it will be in hispower to vary the level of his machine with very considerable nicety;enabling him to approach the surface of the earth, or in a gentlecurve to sweep away from its occasional irregularities, and proceed toa very considerable elevation without interrupting the progress of hiscourse, and, what is of more importance, without sacrificing any partof his resources in gas or ballast, upon the preservation of which theduration of his career so entirely depends. These properties of therudder it is not possible to display in the present exhibition, owingto the confined nature of the course which it is necessary to pursue;but they were sufficiently tested in the preliminary experiments atWillis's Rooms, where the space being larger, a circular motion wasconferred upon the machine by connecting it with a fixed centre roundwhich it was thus made to revolve, without the necessity of confiningit to the one level. 

The rate of motion which the Balloon thus equipped is capable ofaccomplishing varies according to the circumstances of its propulsion. When the Archimedean Screw precedes, the velocity is less than whenit is made to follow, owing to the reaction of the air in the formerinstance against the car, the under surface of the balloon, and otherobstacles, by which its progress is retarded. Again, when the cordupon which it travels is most tense and free from vibration, the rateis found to be considerably accelerated, compared with what it is whenthe contrary conditions prevail. But chiefly is its speed affectedby the proper _ballasting_ of the machine itself, upon which, depends the friction it encounters from the cord on which it travels. Under ordinary circumstances it proceeds at a rate of about four milesan hour, but when the conditions alluded to have been most favourable, it has accomplished a velocity of not less than five; and there is nodoubt that were it altogether free from restraint, as it would be inthe open air, with a hand to guide it, its progress would be upwardsof six miles an hour. 

Having now, I trust, sufficiently explained the principles exemplifiedin the model here described, it may be expected that I should add afew words regarding their reduction into practice upon a larger scaleand in the open air, with such difficulties to contend with as may beexpected to be encountered in the prosecution of such a design. In thefirst place, however, it will be necessary to disabuse the public mindof some very prevailing misconceptions with respect to the conditionsof a Balloon exposed to the action of the winds, pursuing itscourse under the exercise of an inherent propulsive power. Thesemisconceptions, which, be it observed, are more or less equallyparticipated in by the scientific as by the ignorant, when devoidof that practical experience which is the basis of all aeronauticalproficiency, are of a very vague and general character, andconsequently not very easy accurately to define. In order, therefore, to make sure of meeting all the objections and removing all the doubtsto which they are calculated to give rise, it will be advisable, evenat the risk of a little tediousness, to separate them into distinctquestions and treat them accordingly. 

One of the most specious of these misconceptions regards the effectsof the resistance of the atmosphere upon the figure of the Balloonwhen rapidly propelled through the air, whereby it is presumed itsopposing front will be driven in, and more or less incapacitated fromperforming the part assigned to it; namely, to cleave its way with thereduced resistance due to its proper form. To obviate, this imaginedresult, various remedies have been proposed--such as, to constructthat part of the machine of more solid materials than the rest, orelse (as suggested by one of the most scientific and ingenious ofthose who have devoted their attention to the theory of aerialnavigation), to subject the gaseous contents of the Balloon to such adegree of artificial condensation by compression, as shall supplyfrom within a force equal to that from without; adopting, of course, materials of a stronger texture than those at present in use, for theconstruction of the balloon. Now the contingency against which it ishere sought to provide, and which I grant is a very reasonable one toanticipate, has nevertheless no real existence in practice; at leastin such a degree as to render it necessary to have recourse to anyparticular expedient for its prevention. Taking it for granted thatthe hypothesis in which it is involved is founded upon a presumedanalogy with a Balloon exposed to the action of the wind while in astate of attachment to the earth, I would first observe that the casesin question, however apparently analogous, are in reality essentiallydissimilar. In the one case (that where the Balloon is supposed to beattached to the earth) all the _motion_, and consequently all the_momentum_, is in the air; in the other case (where the Balloonis supposed to be progressive), it is in the constituent particles ofthe machine itself and of its gaseous contents. And this momentum, which is ever proportioned to the rate of its motion, and, consequently, to the amount of resistance it experiences, is amplysufficient to secure the preservation of the form of its opposingfront, however partially distended, and whatever the velocity withwhich it might happen to be endowed. Independently, however, of thiscorrective principle, another, equally efficacious is afforded in thebuoyant power of the included gas, which, occupying all the upper partof the Balloon so long as it is in a condition to sustain itself inthe air, and generally extending to its whole capacity, presses fromwithin with a force far greater than any it could experience fromthe external impact of the atmosphere, and sufficiently resists anyimpression from that quarter which might tend to impair its form. To what extent this is effective, will appear more clearly when weobserve that in any balloon inflated, it is the _sides_ of thedistended globe that bear out the weight of the appended cargo, through the intervention of the network; a weight only limited by thesustaining power of the machine itself, and in the case of the greatVauxhall or Nassau Balloon, amounting to more than two tons, andconsequently pressing with a force far exceeding any that could arisefrom the impact of the air at any rate of motion it could ever beexpected to accomplish. And this statement, which represents thetheoretical view of the question, is fully borne out by the realcircumstances of the case as they appear in practice. So farfrom justifying the apprehensions of those who conceive that the_front_ of the Balloon would be disfigured by its compulsoryprogression through the air, the result is exactly the reverse; theonly tendency to derangement of form displaying itself in the part_behind_, where the rushing in of the atmospheric medium to fillthe place of the advancing body (in the nature of an _eddy_, as it is termed in water), might and no doubt would, to some extent(though perhaps but slightly) affect the figure of that part, in amanner, however, calculated rather to aid than to impair the generaldesign in view, Another error of more universal prevalency, because of a moresuperficial character, regards the condition of the Balloon asaffected by the currents of air, in and through which it might haveto be propelled. The arguments founded upon such a view of the case, generally assume some such form as the following--"It is true you canaccomplish such or such a rate of motion; but that is only in a room, with a calm atmosphere, or with a favourable current of wind. In theopen air, with the wind at the rate of twenty or thirty miles an hour, your feeble power would be of no avail. You could never expect todirect your course _against_ the wind, and if you were to attemptit and the wind were strong, you would inevitably be blown to piecesby the force of the current. " Now this argument is equally nought withthe preceding. The condition of the Balloon, as far as regards theexercise of its propulsive powers, is precisely the same whether thewind be strong or gentle, with it or against it. In neither case wouldthe Balloon experience any opposition or resistance to its progressbut what _itself_, by its _own_ independent motion, created;and that opposition or resistance would be exactly the same inwhatever direction it might be sought to be established. The Balloon, passively suspended in the air, without the exercise of a propulsivepower, experiences no effects whatever from the motion of theatmosphere in which it is carried, however violent; and theestablishment of such a propulsive power could never subject it tomore than the force itself, with which it was invested. The _way_which the Balloon so provided would make through the air would alwaysbe the same, in whatever direction, or with whatever violence the windmight happen to blow; and the condition of the Balloon would always bethe same that was due to its _own independent_ rate of motion, without regard to any other circumstances whatever. If it wasfurnished with the means of accomplishing a rate of motion equal toten miles an hour, it would experience a certain amount of atmosphericresistance due to that rate; and this amount of resistance withall its concomitant consequences, neither more nor less, would itexperience, whether it endeavoured to make this way _against_ awind blowing at the rate of 100 miles an hour, or _with_ the samein its favour. The result, so far as regards its distance from theplace of starting, would, I grant, be very different; but at presentwe are only considering the conditions of its motion through the_air_, and these, I repeat, would be the same whatever the rateor course of the wind; so that all speculations on this scoremust resolve themselves into questions of _quantity_, not of_quality_, in the effect sought to be accomplished: in otherwords, all consideration of the rate of the wind must be left out ofthe argument, except, in so far as it shall be taken to regulate thelimit which shall be assigned to the rate of the aerial machine, assufficient to justify its claims to the title of a successful mode ofnavigating the skies. [A]

[Footnote A: The condition of a Balloon propelled by machinery is veryanalogous to that of a boat in the water driven by oars or paddles. Suppose such a boat to be rowing or paddling up a river against thestream, if a piece of cork be thrown overboard it appears to becarried away with the current. But this is delusive; it is the boat_alone_ which really moves away from the cork. For if the boat beleft to its own course, both it and the cork will float down together;and if the use of the oars or paddles be resumed, the distancebetween the boat and the cork will proceed to develope itself exactlyaccording to the rate of the _boat_, without any regard to thatof the _stream_. If the stream be excessively rapid, the boatsmenwill appear to be exercising very great force to enable them to stemthe torrent and avoid being carried backward. Now the resistance whichthey experience and all its attendant effects are only those whichthey create for themselves, and which they would experience in exactlythe same degree were they to endeavour to move _at the same rate_in calm water or with the current in their favour. If the current beat the rate of ten miles an hour and they are just able to maintaintheir place, they are proceeding at the rate of ten miles an hour, andthey experience the opposition due to that rate of motion; preciselythe same as they would experience if they sought to accomplish thesame rate of motion under any other circumstances. And if the currentwere 100 miles an hour, they would suffer no more from endeavouring togo against it, with the force just ascribed to them, than if theywere to exercise the same force in any other direction, or in a waterperfectly tranquil. Apply this reasoning to the case of a Balloonpropelled by machinery, and much of the obscurity in which it isinvolved will disappear. ]

With these conditions established, it will now be seen that we havenothing to consider, in discussing the probable success of any schemeof aerial navigation with the aid of the Balloon (so far as its meremovements are concerned)[A] except the _actual rate of motion_which it is competent to accomplish; whether or not it be sufficientto meet the exigencies of the case as they may happen to be estimated. That its capabilities in that respect, be displayed within a room, orin a calm atmosphere, or under what may be called the most favourablecircumstances, has nothing in it to disparage or affect the generalquestion. Whatever it can do _there_, it can do the same in ahurricane; and the only real question is, "whether, what it _can_accomplish in respect of rate, is enough to answer the purpose inview. "

[Footnote A: I have said "so far as its mere movements are concerned;"because the complete success of the scheme, how far it is an availableand satisfactory mode of transport, depends upon other conditionsbesides the accomplishment of a given rate of motion--as for instance, whether it be safe, or practicable, or consistent with a duepreservation of the _buoyancy_ of the Balloon, so as to allow ofits being employed in voyages of sufficient distance and duration, or capable of being worked at moderate cost, or whether it leavesufficient allowance for cargo; with many others of less strikingimportance, which the practical aeronaut will readily suggest forhimself. ]

The model we have been just describing is capable as we have seen, ofaccomplishing a rate of about six miles an hour. Now the resistance tothe progress of a Balloon varies as the squares of the velocities orrates of motion. Accordingly, for the same Balloon to accomplishtwice the speed, or twelve miles an hour, it would be necessary to beprovided with four times the power. Thus as the spring power employedin the model is equal to a weight of 45 pounds, upon a barrel of fourinches in diameter, it would require one competent to raise 180 poundson the same sized barrel, to enable it to propel the same Balloon atdouble the present rate. 

But with regard to Balloons of different sizes and of the same shape, the power required to produce the same rate of motion, would be asthe squares of their respective diameters: for the power is as theresistance, the resistance as the surface, and the surface follows theproportion just assigned. In order, therefore to propel a Balloonof the same form and twice the diameter, at the same rate, it wouldrequire a force of four times the amount. 

Now to apply this to the consideration of a Balloon of superiormagnitude, let us assume one of 100 feet in length, and fifty feet inheight. The buoyant power of such a machine, or the weight it wouldcarry, supposing it inflated with gas of the same specific gravity, compared with that of the model, would be as the cubes of theirrespective diameters; or in, about, the ratio of 420 to one. Such aBalloon, therefore, so inflated, would carry a weight of about 8700pounds, or above three tons and three quarters. As, however, it wouldbe very expensive to inflate such a vessel with pure hydrogen gas, itwould be advisable to found our calculations upon the use of coal gas;under which circumstances the weight it would carry would be limitedto about three tons. Deducting from this, one ton for the weight ofthe Balloon itself and its necessary equipments, there would remaintwo tons, or about 4500 pounds, to be devoted to the power, whateverit might be, by which the machinery was to be moved, and the livingcargo it might have to carry. Nor let the reader be surprised atthe magnitude of the figures we are here employing, as if it weresomething extraordinary or beyond the power of man to accomplish. Thedimensions and power we have here assumed is very little greater thanthose of the great Vauxhall Balloon, [A] and considerably less thansome of _Montgolfières_, or Fire-balloons, which were firstemployed. 

[Footnote A: The height of the Vauxhall Balloon is about eighty feet, its breadth about fifty. It contains 85000 cubic feet of gas, andsupports a weight of upwards of two tons. ]

Now the resistance which such a Balloon as I have here described wouldexperience in its passage through the air, and consequently the powerit would require to establish that resistance compared with thoseof the model, we have said would be as the _squares_ of theirrespective diameters, or in, about, the ratio of only fifty-six toone; in other words, whatever force it would take to propel the modelat any given rate, it would require just fifty-six times the powerto accomplish the same result with the large Balloon we have beendescribing. 

In order to ascertain precisely what this power would be in any giveninstance, it only remains to find an expression for the spring powerwith which we have been hitherto dealing, that shall be more generallycomprehensible. 

This we shall do by a comparison with the power of steam, according tothe usual mode of estimating it; that is, reckoning a one-horse powerto be equal to the traction or draught of 32, 000 lbs. Through thespace of one foot in a minute. According to this scale, observing thecorresponding conditions of the spring--namely, the weight it balanceson the barrel, (answering to the force of traction) = 45 lbs. , thecircumference of the barrel (answering to the space traversed) = onefoot, and the time of uncoiling for each turn, (answering to the rateof the operation) say, three seconds and a half--we find the power ofthe spring employed in the propulsion of the model, to be as nearly aspossible the forty-second part of the power of one horse; from whenceit is easy to deduce the conditions of flight assignable to the same, and to different sized Balloons of the same shape, at any other degreeof speed. Assuming, for instance, a Balloon of 100 feet in length and50 feet in height, and proposing a rate of motion equal to 20 miles anhour, we have, in the first instance, the power required to propelthe model at that rate, compared with that already ascertained for avelocity of six miles an hour, in the ratio of the _squares of thetwo velocities_, as nearly ten to one; that is, ten forty-seconds, or about one-fourth of a horse power. To apply this to the largerBalloon, we must take the squares of their respective diameters; whichbeing nearly in the ratio of 56 to 1, gives an amount of 56 timesone-fourth or about 14 horses, as the sum of the power required. 

From what particular source the power to be employed in the propulsionof the Balloon should be deduced, is not indeed a question withoutsome difficulties and doubts in the determination. To all the movingpowers at present before the world some objections apply whichdisparage their application, or altogether exclude them from ourconsideration. 

The power of the coiled spring is too limited to be employed upona larger scale. The use of the steam-engine is accompanied with agradual consumption of the resources of the Balloon in ballast, andconsequently in gas, the one being exactly answerable to the other, and is therefore not calculated for voyages of long duration. Humanstrength appears to be too feeble for great results, and moreover, requires repose; which reduces the amount assignable to each man to afraction of its nominal value. Of electro-magnetism as yet we knowtoo little to enable us to pronounce upon it with certainty. Of theremaining powers known only one is worth mentioning in connexionwith this subject, namely, the elastic force of air; and this I onlymention because it has been taken up by one whose authority in thesematters is deservedly entitled to much weight, and who entertainsgreat hopes of making it ultimately subservient to the purpose inview. 

But although none of these powers, in their present state, be soperfectly adapted to the propulsion of the Balloon as to leavenothing further to desire, yet are some of them so far applicable as, undoubtedly, to enable us to accomplish, by their means, a very largeamount of success. A steam engine of the power required, namely, equalto fourteen horses, could be easily constructed, far within the limitsof weight which we have at our disposal upon that account in theBalloon under consideration, or even in one much smaller; and recentimprovements have so far reduced the amount of coal required for itsmaintenance, that perhaps as long a voyage could be made by means ofit now, as would be expected or required. Even human strength, bya certain mode of applying it, might be made effectual to theaccomplishment of a very sufficient rate of motion, say fourteen orfifteen miles an hour, for, continuously, as long a period as thenatural strength of man, moderately taxed, could endure, and which wemay reckon at twelve hours. 

It is true that neither the velocity here quoted, nor that beforeassumed is so great as to enable the aeronaut to compete with some ofthe modes of transit employed on the surface of the earth; as, forinstance, the railroads, where 25 miles an hour is not an unusualspeed. Yet is not the aerial machine which could command such arate of motion to be despised, or set aside as inferior in actualaccomplishments to what is already at our disposal; for it must notbe lost sight of, that railroads, or terrestrial roads of everydescription, must ever be limited in their extent and direction, andtravelling on them, however perfectly contrived, subject to deviationsand interruptions, particularly in passing from one country to anotherbeyond the seas, which if taken into account, would reduce theapparent estimate of their rates, considerably under the lowest ofthose assigned to the Balloon in the previous calculation; and at allevents, by sea, much less, under the most favourable circumstances isthe ordinary rate of ships. 

But, it may be observed, we are here counting upon a rate of motion asestablished, which is only effectual to that extent in the absence ofcontrary currents of wind. This is true; nevertheless it is no bar tothe use which might be made of the aerial conveyance so furnished, norany disparagement to the advantages which might be drawn from it;for not only does the aeronaut possess the means of choosing, withincertain limits, the currents to which he may please to commit himself, and of which, abundance of every variety is sure to be met with atsome elevation or other in the atmosphere, but, as in all generalarguments, where the conditions are equally applicable to both sidesof the question, they may be fairly left out as neutralising eachother, so, here it must not be forgotten, that the currents inquestion, being altogether indeterminate, and equally to be expectedfrom all quarters, an equal chance exists of advantages to be derived, as of disadvantages to be encountered from their occurrence; and that, even without the means of making a selection, the admitted laws ofreasoning would justify us in considering the chances of the latterto be fully counterbalanced by those of the former. It is enough, formoderate success at least, if, possessing the power of avoiding thebad, and of availing himself of the good, the aeronaut be furnishedwith the means of making a sufficient progress for himself when theatmosphere is such as neither to favour nor to obstruct him; and inthis condition I humbly conceive he would be placed, with even aless rate of motion than that which we have before assigned, andconfidently reckon upon being able to accomplish. 

FINIS.