CHAPTERLVII.ON BAL LOONS. THEIR DEFECTS AND FARTHER IMPROVEMENTS.Section 303.These Defects are best known from the History: a Detail of which is given to the World in an entertaining, elegant, and scientific Manner, by a celebrated Writer on other Subjects,Mons. Faujas de Saint Fond, in two Volumes, 12mo. for the two last Years, illustrated with Engravings by the best Masters.And he promises a Continuation, or annual Register of Experiments and Improvements.The Title of the Book is,“Description des Experiences de la Machine aërostatique, &c. &c.”304. Mr. Cavallo has favoured the British Nation with a cursory tho’ clear Account of thesame, in his “History of Airostation:” a Continuation of which it were to be wished he woud likewise publish annually.305. It might contribute greatly to the Improvement of the Art; if Mr. Faujas woud give Engravings on a large Scale, of the different Machinery, already used or invented to direct the Balloon, with their Proportions: particularly themoulinetofBlanchard: as well as that lately tried by Messrs. Auban and Vallet; whose Machinery is stillmore distinguishedandeffectual.306. The Titles and Sizes of all useful Books written on the Subject, also the Places where they are to be had, might likewise be inserted, at the End of eachannualVolume.307. The principal Defects of the British Balloons are, in1. The Construction.2. Production of Gass.3. Mode of Direction, and4. Security of landing.First, Defects of the Construction are both in the Form, and Composition.The Form ought to be that of aright[101]Cylinder,[102]by which theCapacityis doubled without encreasing the Resistance: ending above and below, each in a Hemisphere. A cylindrical Trunk, 2 Feet in Diameter, being added to convey the Gassintothe Balloon; and suffer itto escape, when too much expanded in the etherial Regions.It shoud also be furnished with a Valve, at the Bottom, of equal Diameter with the Trunk: keeping itself Air-tight; and opening outwards by agivenResistance, (as that of ten Pounds Troy,) from the inside Gass.There must be an upper Valve as usual: occasionally to promote aswiftDescent.308. The Form will likewise continue to be defective, till an interior Balloon for common Air is adopted, according to the Plan laid down by the ingenious Mons. Meunier, lately appointed by the French Academy of Sciences at Paris, one of the Commissioners for the Improvement of Airostation.The Use of which interior Balloon by Compression of the surrounding Gass in the external Balloon, prevents, it is said, the Loss of Ballast and of Gass: two very considerable Advantages.For the actual Sum total of Gass not being diminished; the Balloon will continue longer in the Air, before an Escape of Gass, throu’ the Pores of the Silk, makes it descend.There will, on the same Account, be less Occasion to take inmeerBallast, for the Purpose of throwing itoverboard, to prevent the Descent.Therefore an equal Weight of Articles necessary to remain in the Car, may be substituted in Place of the Ballast.309. Art. 1. And, since it is nextto impossible, the Atmosphere shoud continue for 24 Hours together, of thesame Density, Weight, and Temperature; or, in short, without Motion;—the Aironautwill have a Power of seeking, atdifferentHeights, for that Current of Air, orWind, which suits him best: or, in a very few Minutes, to rise above all Currents; become stationary, andlie toin theserene, waiting for aWind: which, as before mentioned, he may readily find, by lowering out a Mile of Twine, and hiswhiteFlag: attending to it, with a small perspective Glass, or Magnifier.309. 2. Another mostmaterialAdvantage is to be able, in ahigh Wind, to chuse the Spot on which he proposes to alight: or wait for a favourable Opportunity to descend.To ascertain the Height of the Balloon by a Quadrant.310. To compute the Height and Distance of the Balloon, by Means of awhiteFlag, or othervisibleObject, suspended from the Car, at a certain Distance below it.Let the Observer take the Altitude of the Car with a Quadrant: and also the Altitude of the Object or Flag.Then by a Case in plain Trigonometry; if the Altitude of the Car be by the Quadrant 59° = HAC, the Altitude of the Object 55° = HAO, and the Length of the Line veered out be 200 Yards, or otherwise = CO.Then the Complement of HAO = AOH = 35°; and the Complement of the Angle HAC = ACH = 31°; and the Supplement of OAC + ACO = AOC = 145°.Then, CAO 4° : CO 200 :: AOC 145° : AC; and Radius : AC :: CAH 59° : CH 1409Yards, the Height of the Balloon taken at the Time.Next, Radius : AC :: ACH 31° : AH 846 Yards, which is the horizontal Distance of the Place on the Earth from the Observer, over which the Balloon was then suspended.This Method finds the Height truer than the Barometer, and with fewer Circumstances of Confusion.And if the Balloon Art coud be perfected, so as to make them stationary at any Height; this Circumstance woud afford excellent Opportunities of proving the Heights by the Barometer: besides which, the Distance also has been obtained: a Point not before attempted.[103]
CHAPTERLVII.
Section 303.These Defects are best known from the History: a Detail of which is given to the World in an entertaining, elegant, and scientific Manner, by a celebrated Writer on other Subjects,Mons. Faujas de Saint Fond, in two Volumes, 12mo. for the two last Years, illustrated with Engravings by the best Masters.
And he promises a Continuation, or annual Register of Experiments and Improvements.
The Title of the Book is,“Description des Experiences de la Machine aërostatique, &c. &c.”
304. Mr. Cavallo has favoured the British Nation with a cursory tho’ clear Account of thesame, in his “History of Airostation:” a Continuation of which it were to be wished he woud likewise publish annually.
305. It might contribute greatly to the Improvement of the Art; if Mr. Faujas woud give Engravings on a large Scale, of the different Machinery, already used or invented to direct the Balloon, with their Proportions: particularly themoulinetofBlanchard: as well as that lately tried by Messrs. Auban and Vallet; whose Machinery is stillmore distinguishedandeffectual.
306. The Titles and Sizes of all useful Books written on the Subject, also the Places where they are to be had, might likewise be inserted, at the End of eachannualVolume.
307. The principal Defects of the British Balloons are, in
1. The Construction.
2. Production of Gass.
3. Mode of Direction, and
4. Security of landing.
First, Defects of the Construction are both in the Form, and Composition.
The Form ought to be that of aright[101]Cylinder,[102]by which theCapacityis doubled without encreasing the Resistance: ending above and below, each in a Hemisphere. A cylindrical Trunk, 2 Feet in Diameter, being added to convey the Gassintothe Balloon; and suffer itto escape, when too much expanded in the etherial Regions.
It shoud also be furnished with a Valve, at the Bottom, of equal Diameter with the Trunk: keeping itself Air-tight; and opening outwards by agivenResistance, (as that of ten Pounds Troy,) from the inside Gass.
There must be an upper Valve as usual: occasionally to promote aswiftDescent.
308. The Form will likewise continue to be defective, till an interior Balloon for common Air is adopted, according to the Plan laid down by the ingenious Mons. Meunier, lately appointed by the French Academy of Sciences at Paris, one of the Commissioners for the Improvement of Airostation.
The Use of which interior Balloon by Compression of the surrounding Gass in the external Balloon, prevents, it is said, the Loss of Ballast and of Gass: two very considerable Advantages.
For the actual Sum total of Gass not being diminished; the Balloon will continue longer in the Air, before an Escape of Gass, throu’ the Pores of the Silk, makes it descend.
There will, on the same Account, be less Occasion to take inmeerBallast, for the Purpose of throwing itoverboard, to prevent the Descent.
Therefore an equal Weight of Articles necessary to remain in the Car, may be substituted in Place of the Ballast.
309. Art. 1. And, since it is nextto impossible, the Atmosphere shoud continue for 24 Hours together, of thesame Density, Weight, and Temperature; or, in short, without Motion;—the Aironautwill have a Power of seeking, atdifferentHeights, for that Current of Air, orWind, which suits him best: or, in a very few Minutes, to rise above all Currents; become stationary, andlie toin theserene, waiting for aWind: which, as before mentioned, he may readily find, by lowering out a Mile of Twine, and hiswhiteFlag: attending to it, with a small perspective Glass, or Magnifier.
309. 2. Another mostmaterialAdvantage is to be able, in ahigh Wind, to chuse the Spot on which he proposes to alight: or wait for a favourable Opportunity to descend.
To ascertain the Height of the Balloon by a Quadrant.
310. To compute the Height and Distance of the Balloon, by Means of awhiteFlag, or othervisibleObject, suspended from the Car, at a certain Distance below it.
Let the Observer take the Altitude of the Car with a Quadrant: and also the Altitude of the Object or Flag.
Then by a Case in plain Trigonometry; if the Altitude of the Car be by the Quadrant 59° = HAC, the Altitude of the Object 55° = HAO, and the Length of the Line veered out be 200 Yards, or otherwise = CO.
Then the Complement of HAO = AOH = 35°; and the Complement of the Angle HAC = ACH = 31°; and the Supplement of OAC + ACO = AOC = 145°.
Then, CAO 4° : CO 200 :: AOC 145° : AC; and Radius : AC :: CAH 59° : CH 1409Yards, the Height of the Balloon taken at the Time.
Next, Radius : AC :: ACH 31° : AH 846 Yards, which is the horizontal Distance of the Place on the Earth from the Observer, over which the Balloon was then suspended.
This Method finds the Height truer than the Barometer, and with fewer Circumstances of Confusion.
And if the Balloon Art coud be perfected, so as to make them stationary at any Height; this Circumstance woud afford excellent Opportunities of proving the Heights by the Barometer: besides which, the Distance also has been obtained: a Point not before attempted.[103]