CHAPTERLX.HINTS FOR THE DIRECTION OF THE BALLOON.Sect. 315. Art. 1.IN the London Chronicle, from the 20th to the 22d of August, 1785, is a Letter from Bury, containing an Account of Mr. Poole’s Balloon, with the following Circumstance, viz. “It was found necessary, before the Balloon was liberated, to cut away the Wings, intended to act as Sails, which had been constructed by an ingenious Piedmontese, patronized bylord orford, and which it was supposed, woud have contributedto facilitate the Direction of theBalloon, but were foundgreatly to retard the Celerityof its Motion.”Now if any Credit can be given to Newspaper Accounts, (that of the Beccles Balloon being an entire Fable,) it is to be lamented that the Wings were cut away for the Reason assigned: as it seems the only one that could properly be offered for applying them.315. 2. Balloons already rise like a Rocket, and press forward almost with the Celerity of the Wind: it is therefore evident, that these Celeritiesmust begreatly retarded, in orderto facilitate the Direction: and consequently that the Wings bid fair to have answered the Intention of their ingenious Projector. And why precipitately cut them away, before the Balloon was left to the Pleasure of the Winds? since no regular or safe Manouvres ought to have been attempted, till that Time.There appears to have been much the same Reason for rejecting the Piedmontese Wings, that there was for condemning the use of a Parashute, to which a Dog being appended was killed in the Descent: because the Parashute was not let loose at a sufficient Height, nor was it properly distended.315. 3. It seems, that as the Wings hadgreatlyimpededthe Balloon; a certainAdditionto them might havenearlystoppedit in the Air.For the Balloon having once acquired an uniform Motion, by encreasing the Surface of the resisting Body, or Wings, the Balloon maybe retarded to a certain Point. But the Resistence encreasing woud raise the resisting[105]Body above its Power of Action, and therefore, in Fact, lessen it; by which Means the Balloon woud continue to be propelled in the Direction of the Wind, with a Force equal to that Diminution.Suppose, for Instance, that, instead of the half Mile Flag, which evidently checked the progressive Motion of the Balloon (Section 70) a larger square Surface, of varnished Silk, or a triangular Latteen Sail (like the Αρτεμων of Le Roi[106])was substituted, and kept stretched, by a hollow Cane, or Yard.[107]315. 4. Also, that by Means of a Fan or small Oar, acting as a Rudder, to be folded and taken back into the Car at Pleasure, the Balloon was compelled to move with a given Side foremost; that the Sail was let down below the Car, by strong silken Cords fastened to each Angle; and lastly, that leaden Weights, (each weighing an Ounce Averdupoise when widely perforated, and put throu’ the Ends of each Cord before it is fastened to the Car), be let down to each Angle; occasionally encreasing the Weights (or Sail) in Proportion to the Wind; which relative Weights (or Sail) will best be determined by repeated Experiments; will not such an Apparatus or Anemometer-Sail, acting as a Vis Inertiæ nearly at right Angles against the Force of the Wind, check the Balloon; till the encreasing Resistence raising the Sail upwards towards the Horizon diminishes its Power of Action? With this Sail therefore, which requires little Attention; and with the Assistance of Wings moved by Levers, pressed alternately downwards as the Bellows of an Organ, by the Feet of the Aironaut and mere Weight of his Body, standing upright near the Center of the Car; the Balloon may probably be, in some Respect, subject to Direction, and move obliquely against the Wind, or with Force in a Calm.The Balloon and Anemòmeter-Sail, like theEarth and Moon will turn on their common Center of Gravity.315. 5. It is possible to erect a light hollow Mast throu’ the Car, and throu’ the Balloon, by Means of a cylindrical Tube of varnished Silk, extending from Top to Bottom, in order to sustain the Balloon in an upright Situation, and make it keep Pace with the Car, when the latter is propelled by the Wings. The Mast shoud be covered with soft Cotton, to lessen the Roughness of the Friction. It may also contain within it, another slenderer hollow Mast, after the Manner of a Cane Fish-Rod; either to be lowered out, and placed horizontally across or below the Car, to serve as a Guard for the Bottom of the Anemòmeter-Sail; or to be let down to any Depth occasionally: and other Sails connected, by the usual wooden Rings, and kept tight by Cords running throu’ Blocks fastened to any Part ofthe equatorial Hoop, as used at first, by thegallant Admiral of the Airblanchard, and afterwards too precipitately rejected; since, in Case of a Rupture of Gass throu’ the upper Hemisphere of the Balloon; the equatorial Hoop preserves the Parashute complete: and for Want of which Hoop, young Arnold had certainly lost his Life, if the Water of the Thames had not broke his Fall.During the Descent of the Balloon, the Sails are to be taken in, and the lower Mast projected into its Socket.315. 6. Different Trials may be repeatedly made: the Effects of which, whether evidently useful orapparently otherwise, being carefully recordedand regularly publishedin Detail, may afford Data for the Prosecution of further Discoveries, and lay the Foundation for a rational Superstructure ofairostatic Navigation.On the Manner in which the Wind, Anemòmeter, and propulsive Machinery will probably operate on the Balloon.Sect. 316. Art. 1. By adding Weights, and encreasing the Surface of Anemòmeter-Sails; the Vis Inertiæ will become so powerful in the Direction of the resisting Medium of the Air; that the Wind in the opposite Direction will force the Balloon out of its Vertical, and incline it to the Horizon. The Car will be a Fulcrum Axis or Center of Motion: on an imaginary Point of which, as on a Pivot, the Balloon and Sails will turn opposite Ways, balancing each other in every Situation.316. 2. The Balloon must therefore be brought back into the Vertical by a counter Exertion of the Wings: to which the Vis Inertiæ must always be made to bear a just Proportion.The Declination of the Balloon is the only Inconvenience foreseen to result from an Anemòmeter too large, or too heavily laden: and it is instantly remedied by slacking the Sail.One Thing still remains to be mentioned.317. BalloonsdurablyAir-tight, and terminating in aHemisphereabove, (Section 307); ought to have their Dimensions such, that there shoud be no Occasion for more than their upper Hemisphere to be inflated. Under which Form, they may with Ease and Safety be pitched as Tents on the Ground; by Cords fastened at equal Distances to the equatorial Hoop; and on Occasion by the Aironaut himself, while in the Car: who may be provided withIron Ring Stakes barbed, and fastened or ready to be fastened to each Balloon-Cord: and, as soon as the Balloon is moored by the Anchor, Grapple, and snatch Block, (Section 298, 3) with a light Axe drive down the Stakes round the Car, and regulate them when he alights from it, on the Ground.
CHAPTERLX.
Sect. 315. Art. 1.IN the London Chronicle, from the 20th to the 22d of August, 1785, is a Letter from Bury, containing an Account of Mr. Poole’s Balloon, with the following Circumstance, viz. “It was found necessary, before the Balloon was liberated, to cut away the Wings, intended to act as Sails, which had been constructed by an ingenious Piedmontese, patronized bylord orford, and which it was supposed, woud have contributedto facilitate the Direction of theBalloon, but were foundgreatly to retard the Celerityof its Motion.”
Now if any Credit can be given to Newspaper Accounts, (that of the Beccles Balloon being an entire Fable,) it is to be lamented that the Wings were cut away for the Reason assigned: as it seems the only one that could properly be offered for applying them.
315. 2. Balloons already rise like a Rocket, and press forward almost with the Celerity of the Wind: it is therefore evident, that these Celeritiesmust begreatly retarded, in orderto facilitate the Direction: and consequently that the Wings bid fair to have answered the Intention of their ingenious Projector. And why precipitately cut them away, before the Balloon was left to the Pleasure of the Winds? since no regular or safe Manouvres ought to have been attempted, till that Time.
There appears to have been much the same Reason for rejecting the Piedmontese Wings, that there was for condemning the use of a Parashute, to which a Dog being appended was killed in the Descent: because the Parashute was not let loose at a sufficient Height, nor was it properly distended.
315. 3. It seems, that as the Wings hadgreatlyimpededthe Balloon; a certainAdditionto them might havenearlystoppedit in the Air.
For the Balloon having once acquired an uniform Motion, by encreasing the Surface of the resisting Body, or Wings, the Balloon maybe retarded to a certain Point. But the Resistence encreasing woud raise the resisting[105]Body above its Power of Action, and therefore, in Fact, lessen it; by which Means the Balloon woud continue to be propelled in the Direction of the Wind, with a Force equal to that Diminution.
Suppose, for Instance, that, instead of the half Mile Flag, which evidently checked the progressive Motion of the Balloon (Section 70) a larger square Surface, of varnished Silk, or a triangular Latteen Sail (like the Αρτεμων of Le Roi[106])was substituted, and kept stretched, by a hollow Cane, or Yard.[107]
315. 4. Also, that by Means of a Fan or small Oar, acting as a Rudder, to be folded and taken back into the Car at Pleasure, the Balloon was compelled to move with a given Side foremost; that the Sail was let down below the Car, by strong silken Cords fastened to each Angle; and lastly, that leaden Weights, (each weighing an Ounce Averdupoise when widely perforated, and put throu’ the Ends of each Cord before it is fastened to the Car), be let down to each Angle; occasionally encreasing the Weights (or Sail) in Proportion to the Wind; which relative Weights (or Sail) will best be determined by repeated Experiments; will not such an Apparatus or Anemometer-Sail, acting as a Vis Inertiæ nearly at right Angles against the Force of the Wind, check the Balloon; till the encreasing Resistence raising the Sail upwards towards the Horizon diminishes its Power of Action? With this Sail therefore, which requires little Attention; and with the Assistance of Wings moved by Levers, pressed alternately downwards as the Bellows of an Organ, by the Feet of the Aironaut and mere Weight of his Body, standing upright near the Center of the Car; the Balloon may probably be, in some Respect, subject to Direction, and move obliquely against the Wind, or with Force in a Calm.
The Balloon and Anemòmeter-Sail, like theEarth and Moon will turn on their common Center of Gravity.
315. 5. It is possible to erect a light hollow Mast throu’ the Car, and throu’ the Balloon, by Means of a cylindrical Tube of varnished Silk, extending from Top to Bottom, in order to sustain the Balloon in an upright Situation, and make it keep Pace with the Car, when the latter is propelled by the Wings. The Mast shoud be covered with soft Cotton, to lessen the Roughness of the Friction. It may also contain within it, another slenderer hollow Mast, after the Manner of a Cane Fish-Rod; either to be lowered out, and placed horizontally across or below the Car, to serve as a Guard for the Bottom of the Anemòmeter-Sail; or to be let down to any Depth occasionally: and other Sails connected, by the usual wooden Rings, and kept tight by Cords running throu’ Blocks fastened to any Part ofthe equatorial Hoop, as used at first, by thegallant Admiral of the Airblanchard, and afterwards too precipitately rejected; since, in Case of a Rupture of Gass throu’ the upper Hemisphere of the Balloon; the equatorial Hoop preserves the Parashute complete: and for Want of which Hoop, young Arnold had certainly lost his Life, if the Water of the Thames had not broke his Fall.
During the Descent of the Balloon, the Sails are to be taken in, and the lower Mast projected into its Socket.
315. 6. Different Trials may be repeatedly made: the Effects of which, whether evidently useful orapparently otherwise, being carefully recordedand regularly publishedin Detail, may afford Data for the Prosecution of further Discoveries, and lay the Foundation for a rational Superstructure ofairostatic Navigation.
On the Manner in which the Wind, Anemòmeter, and propulsive Machinery will probably operate on the Balloon.
Sect. 316. Art. 1. By adding Weights, and encreasing the Surface of Anemòmeter-Sails; the Vis Inertiæ will become so powerful in the Direction of the resisting Medium of the Air; that the Wind in the opposite Direction will force the Balloon out of its Vertical, and incline it to the Horizon. The Car will be a Fulcrum Axis or Center of Motion: on an imaginary Point of which, as on a Pivot, the Balloon and Sails will turn opposite Ways, balancing each other in every Situation.
316. 2. The Balloon must therefore be brought back into the Vertical by a counter Exertion of the Wings: to which the Vis Inertiæ must always be made to bear a just Proportion.
The Declination of the Balloon is the only Inconvenience foreseen to result from an Anemòmeter too large, or too heavily laden: and it is instantly remedied by slacking the Sail.
One Thing still remains to be mentioned.
317. BalloonsdurablyAir-tight, and terminating in aHemisphereabove, (Section 307); ought to have their Dimensions such, that there shoud be no Occasion for more than their upper Hemisphere to be inflated. Under which Form, they may with Ease and Safety be pitched as Tents on the Ground; by Cords fastened at equal Distances to the equatorial Hoop; and on Occasion by the Aironaut himself, while in the Car: who may be provided withIron Ring Stakes barbed, and fastened or ready to be fastened to each Balloon-Cord: and, as soon as the Balloon is moored by the Anchor, Grapple, and snatch Block, (Section 298, 3) with a light Axe drive down the Stakes round the Car, and regulate them when he alights from it, on the Ground.