USEFUL CONCLUSIONS.
Change in the Form of the Balloon while descending: with Conclusions drawn from the Change.
Section 159. IT was remarkable that, the lower Parts of the Balloon regularly adopted a similar Form at each Descent: not unlike a Ship’s Bottom; looking up, at the Head or Prow, while on the Stocks: the Neck of the Balloon forming a beautiful central Pillar; in Shape like that of a Speaking Trumpet inverted.
Time of Descent discovered by the Form of the Balloon.
And hence may be derived a Piece of useful Information: as the precise Time of descending is discovered by bare Inspection of the Machine.
Balloon adopting the Form of an elliptic Solid.
160. Another Conclusion seems likewise deducible from the above, that if the Balloon is so burdened, as to descend while it retains the Form of an elliptic solid;[44] it will descend more rapidly, than if it contained less Gass: the Force of Descent in both Cases being supposed the same.
For if the Diminution of Gass be so great as not to fill the upper Hemisphere of the Balloon; the Resistance of the atmospheric Air below woud probably give it the Appearance of a Concave or Umbrella, which woud greatly check the Descent: viz. in Proportion to the Square of the Number of Feet of which the Surface was composed.
An equatorial Hoop prefered to a Parashute.
161. Hence also the evident Utility of an equatorial hoop for Balloons: in Preference to a Parashute, which woud be only an Incumbrance.
