CHAPTER LIX.

SUPERIORITY OF THE AIR-BOTTLE TO AN INTERIOR BALLOON.

Section 314. The Air-Bottle can be attended with no Sort of Danger. For, if it burst; the only Effect is to raise the Balloon: which is made to descend, at Pleasure, by opening either the _lower_ or upper Valve.

Whereas an interior Balloon condensed with common Air, presses against the surrounding exterior Gass: and the Gass, against the +inside+ of the _great Balloon_, when the latter is in an elevated and rarefied Atmosphere; which Atmosphere, in Proportion to its Height, makes _less_ Resistance to the _Outside_ of the great Balloon: and thereby encreases its Tendency to a Rupture.

By the Application of the Air-Bottle, which will be to a Balloon, what an Air-Bladder, or _Swim_ is to a Fish; a concomitant Advantage is derivable.

For the common Balloon and Air-Bottle, which may be called +a double balloon+, will, in their _present imperfect_ State, be able to remain a Day, or perhaps a Couple of Days in the Air: there being no Loss of Gass: unless by Evaporation, throu’ the Pores of the Silk.

And this Advantage of _a double Balloon_ may be effected with little +expence+ (except that of a complete Net) to the different Proprietors, who may make alternate Voyages, with the Balloons _thus_ united: one being inflated with Gass; the other occasionally with three or more Atmospheres of common Air _condensed_.