CHAPTERXXVIIUSEFUL CONCLUSIONS.Change in theFormof the Balloon while descending: with Conclusions drawn from the Change.Section 159.IT was remarkable that, the lower Parts of the Balloon regularly adopted asimilarForm at each Descent: not unlike aShip’s Bottom; looking up, at the Head or Prow, while on the Stocks: theNeckof the Balloon forming a beautifulcentralPillar; in Shape like that of aSpeaking Trumpetinverted.Time of Descent discovered by the Form of the Balloon.And hence may be derived a Piece ofusefulInformation: as thepreciseTime of descending is discovered by bareInspectionof the Machine.Balloon adopting the Form of an elliptic Solid.160. Another Conclusion seems likewise deducible from the above, that ifthe Balloon is so burdened, as todescendwhile it retains the Form of anelliptic solid;â [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 asnotto fill the upper Hemisphere of theBalloon; the Resistance of the atmospheric Airbelowwoud probably giveitthe Appearance of aConcaveor Umbrella, which woud greatlycheckthe 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 anequatorial hoopfor Balloons: in Preference to a Parashute, which woud be only an Incumbrance.
CHAPTERXXVII
Change in theFormof the Balloon while descending: with Conclusions drawn from the Change.
Section 159.IT was remarkable that, the lower Parts of the Balloon regularly adopted asimilarForm at each Descent: not unlike aShip’s Bottom; looking up, at the Head or Prow, while on the Stocks: theNeckof the Balloon forming a beautifulcentralPillar; in Shape like that of aSpeaking Trumpetinverted.
Time of Descent discovered by the Form of the Balloon.
And hence may be derived a Piece ofusefulInformation: as thepreciseTime of descending is discovered by bareInspectionof the Machine.
Balloon adopting the Form of an elliptic Solid.
160. Another Conclusion seems likewise deducible from the above, that ifthe Balloon is so burdened, as todescendwhile it retains the Form of anelliptic solid;â [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 asnotto fill the upper Hemisphere of theBalloon; the Resistance of the atmospheric Airbelowwoud probably giveitthe Appearance of aConcaveor Umbrella, which woud greatlycheckthe 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 anequatorial hoopfor Balloons: in Preference to a Parashute, which woud be only an Incumbrance.