CHAPTER LXVI.
ON THE UTILITY OF BALLOONS.
Section 333. The Balloon opens a new and unlimited Field for Philosophical Discoveries.
334. The many curious and interesting Conjectures which Mons. de Luc (before the Invention of Balloons) throws out, in the Course of 4 large Volumes, on the Subject and Qualities of the Atmosphere; may now be determined by actual Trial.
335. The Abbée Bertholon wrote in 1784: and has particularly mentioned the following Points, as capable of ample Investigation, and. Discussion.
Sect. 336. Art. 1. _The Temperature of the Air at different Heights._
Which will determine whether the Atmosphere be _practically Navigable_, at all Times and Places.
336. 2. _The dissolvent Power of the Air by Means of an Atmometer for Evaporation._
Probably the Height may be determined, to which Clouds commonly ascend in order to find the proper horizontal Level, in which Balloons can move with the greatest Ease, Safety, and Expedition.
336. 3. _Variations of the Barometer._
This will ascertain the exact Height, without Mensuration.
336. 4. _The_ +densities+ _at different Heights_.
A principal Object in de Luc’s abstruse and scientific Researches: not only useful but necessary to determine the Laws of Refraction; without which, Astronomy, and consequently +navigation+, must remain defective.
336. 5. _The different Effects of Tastes and Odors, at different Heights_: _Experiments on Plants and Animals: also of_ +sound+.[111]
These may produce new and salutary Effects on the human Body: and determine how far a Change from hot, putrid, and impure, to cool pure Air, impregnated with the invigorating aërial Acid, may contribute, without the Aid of Drugs, to the Recovery of the Sick, and Invalid: or promote Longevity.
336. 6. _The Direction and Velocity of the Wind._
The different Currents and their different Heights, the Limitation of each Stratum of Wind, together with their different Temperatures at the same Time, will point out the proper Paths for the Balloon to move in, at all Times, and _possibly_ without the Necessity of accurate Direction: the Mode of Ascent and Descent being _already_ known, and proper Instructions given for a secure Landing.
336. 7. _Electricity of the Air_, +meteors+.
This may lead to the Birth Place of Lightening, and Methods how to avoid its Effects in the Air. Tho’ it be already known, that little Danger is to be apprehended, on Account of the mutual Repellency between the electric Fluid, inflammable Gass, and oiled Silk.
The Irides, the Coronaes, Haloes, and other Phenomena of Colours: the Generation and Solution of which may be investigated on the Spot.
336. 8. _Geography may become a new Science._
336. 9. _Use of the Balloon for Signals in the calm Air, above Molestation; above Winds still blowing below: to discover the Positions of an Army, or Navy._[112]
336. 10. _To throw principal Men into a Town: and convey others out of it._
336. 11. With the Montgolfier Balloon, to try Experiments on Light, and Fire: to transport great Weights: raise them out of the Water: draw up Piles, raise Trees, Vessels, &c.
336. 12. The Parashute to secure a Man from too precipitate a Fall, is to be 5 Yards in Diameter, when extended: the Man,—weighing 140 Pounds, and the Parashute weighing 10 Pounds, with a Surface of 150 square Feet,—woud, in that Case, feel no greater Shock than if he had fallen from the Height of six Feet.
336. 13. _Compass and its Variations: also the different Branches in Astronomy._
His Hints on the Direction of the Machine are ingenious.
337. 1. Wheels furnished with Wings.
337. 2. Imitations of the Form and Motions of Fish.[113]
337. 3. Vessels to condense Air, as the Bladders of Fish.
337. 4. Wind-Guns, Wind-Fountains.
337. 5. Elopile and Vapour Steam.
337. 6. Contrary Currents at different Heights: Proof of.
337. 7. New Hints for Balloons to be raised by Steam.
337. 8. Mons. Gouan’s Invention to go +three hundred miles a day in a calm+.
338. The general Use to which Balloons seem capable of being applied, with the Assistance of propulsive Machinery, in the Calm which exists above the Level of a +contrary+ Wind; is that of a common Vehicle, not subject to the Inconvenience of Roads and Inns, between distant Places and Countries, for Passengers, properly accommodated in a Boat-shaped covered Car, furnished with Provisions, and occasional Siberian Cloathing: the Car to be surrounded with, and resting on Bladders, one _fourth blown_, and having each a few Drops of Water within, to keep them moist and elastic;—to prevent an _accidental_ Shock in alighting on Land; and from sinking, if on Water.
Such a Conveyance (the Balloon being once made _Air-tight_, and furnished with an _Air-Bottle_ to ascend and descend _without Loss_ of Gass) is ready at all Seasons and Times: both Night and Day: for, as the Aironauts will enjoy continual Sunshine without a Cloud, from his Rising to his Setting: so, during the Night, the Light of the +stars+, always intercepted in its Passage to the Earth by Clouds or thick Vapours, will be greatly augmented, when above both: besides the probable Increase of Light _reflected_ from the upper Fields of white Clouds shone on continually by the different Planets and Constellations: all which will afford an Illumination equal, if not greater, than that of a cloudless frosty Night, when the Ground is covered with Snow.
And such Light will be sufficient to read or write by: also to examine the _Barometer_,[114] in order to know the _Height_ and Level of the Balloon above the Surface of the Earth; and the +compass+ for Direction.
If Aironauts propose to ascend by Night, and in the Moon’s Quarters; observing likewise the Precautions already given; it may be proper also to consult and take with them the Ephèmeris, in order to know the Time when the Moon rises, and also when she is at the highest, i.e. in the South, or has remained about half her Time above the Horizon.
The plainest Points, on which not only the Success of an Excursion, but the Lives of Aironauts may depend, are too frequently neglected, as unimportant and trivial.