a French pamphlet, on the subject of balloons, and an account of an exnent performed last April at Dijon. AIR BALLOON S. from a Pamphlet lately published at Paris, intitled An Effay on Aerial vigation: Containing the Art of directing the Aereftatic Machines at Pleafure, 1 of accelerating their Motion in the Air. Together with an Account of two Exments to be made, by Means of thefe Machines, in Meteorology. Read before Royal Academy of Sciences, at Paris, the 14th of January, 1784. By Monf. 6, Author of the new Principles of Phyfic. ONS. CARRA begins with an eulogium on Monf. Montgolfier Me. Charles and Robert, for the and ample field which they have red for philofophical experi, and more especially fuch as reto the atmosphere of, our earth. then proceeds to give a fuccinct at of the fpecific elafticity of the fat globes, of their afcenfion in phere, and their tranflation e place to another by the dif#currents of air that they are liameet with in the atmosphere, bas: nave. there combines, and forms different meteors. By thefe principles, the more volatile a fubftance is, the more it ftrives to efcape and rife in the atmosphere; and, in confequence, the more eafily it paffes through and penetrates the different beds, or ftrata, of the atmosphere; and, as it is from hence that the fpecific levity in the different fpecies of gaz or made airs refults, and, confequently, the comparative elafticity in the acroftatic balloons, therefore, the first principle of the aerial navigation is, to choose for the balloon the most volatile gaz, because it causes the greatest elafticity, and furnishes the best means of governing them. e fpecific levity of aëroftatic as is nothing but the effect of a at made air, more light and fubtile the real, or permanent air which pfts the total mass of the atmoft; a mass which, if I may ufe the en, is attached to the center of arth, as the spokes of a wheel are Or it may be any fubmore light than the real or perhair, and which, in confequence, rafe itself to a greater or lefs ht in it, according to the greater efs denfity of the real air, or to the rter or lefs degree of rarity, or voAty of the gaz, or made air. It is, efore, the effect of the volatility the gaz which caufes the balloon to end, and not the effect of a natural nefs of its component parts. This ath is fufficiently proved by the grofs ts, wifich are vifibly of an opaque are, and more charged with impure icies than the real air, rifes only to ertain height in the atmosphere, and The afcenfion of the balloons being only the tendence of the inclofed gaz to efcape towards the circumference of the atmosphere, it follows, Firft, That the balloons always rife on that fide towards which the air is most rare*. Secondly, If the gaz inclofed in the balloon is only one degree lighter than the ftratum of air in which it is firft fer at liberty, it will only rife to where that ftratum of air begins which is one degree more rare than that in which it rofe from. If the gaz is feven times more rare, it will rife feven times higher in the atmofphere, and fo on. The balloon being arrived where the elafticity of the gaz is equal to that of the atmospheric air, the gaz will ftrive to mix with the air that furrounds it, and the balloon will find itfelf tran flated or carried in a current of air, until the elafticity of the gaz hath caufed fuch an expanfion or dilatation of its 3 L 2 cover, They will always rife in an inclined direction; for example, tending towards a river, or a , or a cloud, becaufe it is always in the nature of light fubitances to fearch out that column the atmosphere which is leatt denfe to rife in. Thefe balloons will take another direction columa of vapours force it another way. Independent of thefe vapours or clouds, they ow the current without deviation, till they meet with other cbitacles. They will, therebe fubject to at picature. cover, as will give it power to efcape, either by the pores of the ftretched cover, or by an eruption. Thefe effects will never fail to take place, whatever the nature of the cover may be, because its constituent parts can never be homogeneous in any degree either with the furrounding air or the gaz contained in it; therefore, the fecond principle of the ar rial navigation is, not to fuffer the balloon to rife higher than where the gaz is at least two degrees more rare than that of the atmofpheric air that furrounds it*. The difference between the denfity of the factitious and atmospheric air may be found by the height of the mercury in the barometer, and by the degrees of cold or heat which a thermometer will point out when immerfed in the different kinds of airs employed in balloons: that is to fay, in combining fuch a height of the mercury with fuch a degree of heat or cold, you may difcover the different ftrata of air which the balloon paffes through. Befides, we may learn from this experiment what weight the balloon will take up with it, by calculating the elafticity of the gaz contained therein; considering, in the first place, the nature of the gaz, its comparative weight with refpect to that of the atmospheric air in the different degrees of its denfity, and the motion of the balloon in every poffible current of wind. The motion of aëroftatic balloons in the atmosphere is abfolute: for the vanes fent up with them do not point; that is to fay, the balloons, as well as all bodies attached to them, experience no refistance from the winds, however violent and tormy they may be; becaufe thefe balloons make a conflituent part not only of the column of wind, or current of air in which they are let off in, but of that alfo in which they fhall afterwards arrive, whether it be in defcending by the lofs of gaz, or in afcending by the diminution of ballaft, or in any deviation whatever. Therefore, a balloon launched in the moft rapid column of air, and fitted out with all the rigging and fails of a fhip, is no more, notwithstanding all thefe, than a boat without either oars, fails, or rudder, carried along by the tranquil current of a river. The wind ought, therefore, to be banished from the thoughts of thofe who wish to make experiments in a-rial navigation, either as means of refiftance or acceleration. It must not, however, be fuppofed that a balloon, with all its appendages, when launched into a current of air, more or lefs rapid, is carried from one place to another abfolutely in a paffive manner. If the wind goes one league in five minutes, the balloon makes the fame way in the fame time, unlefs there be fome caufe for deviation. We cannot, therefore, draw any conclufions relative to aerial navigation from the theory of the winds, as applied to navigation on the fea, either with refpect to directing the balloons, or with refpect to accelerating their motions. The third principle of aerial navi gation is, therefore, to find out fome means by which the mufcular power of the navigator may be applied, not only to direct, but alfo to impel the balloon in any direction he may think neceflary. In fhort, it is neceffary that the compound motion produced by the direction which the balloon would take of itfelf, and that produced by the force of the man who accom panies it, that is to fay, the diagonal of a parallelogram, the fides of which are in thefe directions, may be either vertical, horizontal, or oblique to thefe two directions, as that man may judge to be of convenient. I flatter myfelf it has been fhewn that thefe are the only true principles which can be applied to aerial navigations; and it is on the difcovery and application of thefe *In comparing the gaz or factitious air with the progreffive rarity of the permanent or atmos pheric air, the weigh, or levity is out of the question. We have not yet established any thing with ce ranty upon the calculations hitherto made between the gaz of Meff. Montgolfier and the atmofpheric air, or between that and the infiammable air. It remains, there.ore, for the prefent, to make experiments by means of a rial navigations. Thefe experiments will lead us, by litle and little, to a perfect knowledge of every thing which concerns the atmosphere in general; and the different kinds of gaz or factitious air, in particular. thefe principles that I have founded my theory. But, to proceed regularly. I now mean to fhow in what manner I conftruct an aero-nautic machine, with all poffible advantages, not only for the fafety of the navigator, but alfo to direct its course, and accelerate its motion. After having made the balloon of gummed taffety, filled it with a frong gaz, and fufficiently fecured it, I add another cover of the fame ftuff, made in the fame manner, which is to receive the gaz which may escape from the first, either by dilatation or eruption. In every other refpect I ufe the fame means that have been employed by Monf. Charles and Roberts, in their experiment of the 1ft of December laft: that is to fay, the fillet, the cords, the bellows, the pipe of leather, &c. to the end of which I attach a car or boat, made of wicker work, furnifhed at the bottom with a floor of cork, caulked all round, and tarred and decorated with art, elegance, and propriety. Acrofs the middle of the boat, in its wideft part, I place a cylinder of wood, which is extended each way beyond the fides of the boat, and paffes through a ring of leather, fixed in fuch a manner as will permit it to turn round without difplacing itfelf: this cylinder must reach from each fide of the car twenty-five or thirty feet (according to the dimenfions required by the fpecific lightnefs of the balloon, and its diameter) carrying at each end three wings made of gummed taffety, each twenty or twenty-five feet long, and fifteen or twenty broad, thefe three wings are to be at equal diftances one from the other, and arranged in form of a wheel, and faflened on one fide to crofs pieces of wood, and the other fide by cords, fo as to follow the motion impreffed on it by the cylinder, by means of a very fimple pat This weight, by having a cord of forty toizes fixed to it, will ferve as a log to measure the way, and by which you may judge of the velocity of the wind. If this log, for example, fhould be ten feconds in defcending and in unrolling the cord, it is clear that in this interval the aero-nautic ma chine will have advanced beyond the space it has been carried by the current of air forty toizes. We may, therefore, calculate the velocity of the machine from the time the log will take in de fcending; adding afterwards, by approximation, the way which you ought to make with the current of air or wind, in which you are carried (faving unforefeen deviations) by which may be known, within a very little, the diftance from whence you came to the place you would go to. The navi gator must be furnished with a compafs to fteer by; alfo a watch with feconds to know the time; a barometer which will show the height he thall be at, and the thermometer the degrees of cold er heat through which he will paf. put them in motion in an oppofite direction to that the wind blows in. We may conceive, from this explanation, that the aerial navigation hath an advantage over the marine one, in as much as it is neither fubject to the accidents which arife from fudden guits of the winds, or the undulation of the waves, but has fimply a current to furmount. It will happen, neverthelefs, that when it meets with a current of wind, it will prove a fenfible refiftance; but this refiflance will always be lefs than the impulfive force oppofed to it by the rotation of the wings of taffety. The vane will fhow from what point of the compafs the wind blows, and which way you are moving. If I fix two of the three wings of taffety horizontally, which I ufe as oars, I have the fame advantage as is derived from the umbrella in breaking the too fudden fall of the machine, in cafe of an eruption of the two cafes of the balloon; and as this is done only by a turn of the hand, it cannot but be very advantageous, as it wil! fecure the navigator from danger. If the fudden eruption of the two cafes of the balloon fhould be at a time when they are navigating over the fea, my boat or car, by being caulked, muft be very ufeful, and before they will have any danger to fear from the motion of the waves, they will have time to cut the cords, and the pipe of leather of the balloon, that attached it to the boat or car, and to faften one fide of the wings of taffety to a poft fixed in the middle of the boat, to ferve as a maft on fuch occafions. A thin board, that reaches about two feet below the keel of the boat, will ferve as a rudder to direct it on the water, and which may be fixed in an inftant in the place of the tail of taffety, thirty or forty feet long, extended by pieces of whalebone, and which is intended to ferve alfo as a rudder to the car or boat when in the air, as I fhall explain. I have now a boat well caulked, and the wings of taffety ferve me for four purpofes-to accelerate the courfe of the aerostatic ma chine- to direct it-to retard it fcent, in cafe of accident-and to fails for navigating the fea, if octa fhould require them. I have a rudder to feer by in an aerial jour and alfo one to be applied in a voyage: but, notwithstanding the am not yet certain of being th fteer my felf in every cafe; and abfolutely neceffary to have an aid or fupport, which I may fly f occalion, or as neceffity may ret independent of the grand balloon bears up the boat or car, and not connected with any part belei to it. To obtain this fupport, I another balloon upon the model former, with a double covering fix times less than it. I fix to the of my veffel or boat, a stick of feven or eight feet long, to I faften a cord of 140 feet, wh part of the appendage of my balloon. This fecond ballen vated in the air above the grand loon. Another cord of 140 fet to the fame part of the fecond ba and paffed through the net of the balloon, must be held by the nat in the poop of the boat, fo as to an angle (the degrees of which vary without being of confequen the effect) with that attached t pole at the prow of the beat. navigator, by pulling the cord wh in his hand, forces that which tached to the end of the pele at the of the boat, to yield, at the fare that it pufhes forward the grand ba because the elafticity of the i balloon, which is the feventh p the force of the grand balloon, wi thereby entirely taken away, ar in the mufcular motion of the gator; from whence it will follow. the effect of this motion will be t pel the machine forward; and the vigator, by letting the cord go, make the machine defcribe an zontal curve, and by that mean the two balloons an additional of power to raife themfelves ag At the fame time the rudder acting compr *It appears, at the first fight, that taking away the feventh part of the force of the gran by pulling at the fecond balloon, would have no effect on the compounded machine, be force being tranfmitted to the navigator diminishes his weight towards the poop, as much as ng the air which oppofes it, will turn, and defcribe the of a vertical parallelogram: the new direction which he take will be obtained. Moree navigator, fitting at the the boat, and turning der with his left hand, as the cord attached to balloon with his right, will he boat the double motion required to turn and direct , at the fame time, he puts wings either on one fide or he fhall fee neceffary, in mofoot, and fo communicates proper for urging it for another advantage to thofe already propofed, I would put over of tiffue on the fmall fuck full of small spikes made Fire. Thefe wires muft comat the bottom of the balloon erwire, of the fame metal, ker, twisted round the cord attached to the point of the the prow of the boat, the end muft communicate to a piece inclofed in a bag of leather, water, and fastened to the t. The electric fluid gaom the clouds that the mameet with in its way will ted to the piece of refin; and rom thence to the water in which the refin is, regains its equilibrium, and peaceably re-enters its common grand refervoir. It is to be obferved, that the navigator in the boat or car, having no communication with the brafs wire which reaches to the bag of leather, has nothing to fear from the electric matter, however frequent and abundant it may be. In fhort, by flackening the cord of the fmall balloon attached to the flick at the prow, by means of two pullies, one at each end of the stick, you have a very fimple means of defcending at pleafure, without letting out any of the gaz or inflammable air; because the fmall balloon, which is the feventh part of the force of the grand balloon, will no longer help to fultain the whole machine, and which will of courfe defcend during the time of letting out the cord. If you choofe to afcend, you have nothing to do but pull in the cord, which you had before let out, and this, by ftopping the grand bal loon, will immediately cause it to afcend, by partaking of the weight of the whole compound machine, without having occafion to renew the gaz or inflammable air. The ex Such are the means which I now make public to eftablish and bring to perfection aerial navigation. periments which I have offered to make, both on land and on the feat, of the methods which I here propofe, will but, on examining the matter nearer, it will be found that the effect of the motion avigator in drawing the cord of the fmaller balloon, is a motion almost independent of the rest of his body, and confequently, if he pulis at the rate of 25 pounds he than ten pounds of his weight; therefore, there remains 15 pounds; by the ch he impretes an ofcillatory motion on the whole aerial machine, which is the thing the direction of the boat, and to keep it in the track in which it is wanted to move. I can only fay that it is experiment only that can decide either in favour of my means ; and it appears to me that the methods that I propofe, and now make public, in a ted manner, is well worth being put to the trial. this operation fhould be too fatiguing for one perfon, it would be no difficult matter to nion, who would partake in the trouble. It is fufficient to fhow here that it is pollible to dirett the machine. event the electric matter from communicating with the inflammable air, I furnish the es along the grand balloon with a theath of wet leather, for fear the electric fluid nicate that way with the gaz that may chance to efcape from the balloon. this place to obferve, that the aeroitatique balloons, which afcend from the land, hould afterwards pafs over the fea defcend, which may, perhaps, frighten the navigator, the lookers-on, if they are not acquainted before-hand, that the currents of air or wind from the land, which pafs over the fea, lower, or contract themfeives; and thofe from the lea, over the land, afcend or expand themfeives: and, in confequence of this, every ich navigates the air will lower or fall very perceptibly, when it approaches the fea; and realon it will rife in the fame proportion when it quits the fea to navigate over the land, cafe the navigator will do wrong to alter his ballaft, as it will be throwing it away, to no I do not fee the truth of this. The TRANSLATOR, |