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.