Method of ascending to a fixed barometric Height: there to remain suspended in Equilibrio.
302. The Aironaut, may, at any Height, marked by looking at the Barometer, when at 24 Inches for Example, or as soon as he finds his Balloon sufficiently expanded, pull up the Rope over a Pulley; or, wind it upon a Reel of two Feet Diameter, within the Car; and continue to do so; till he finds that the Barometer begins to rise, (which is a Sign that the Balloon descends), by the additional Weight of the Balancer just brought into the Car: on which, by preconcerted Agreement, he may throw out a white Flag, prepared to hang a Yard below the Car.
On Sight of the Flag, the Person at the Reel below is to cut the Rope: which Rope, or a Part of it, is to be drawn into the Car.
The Balloon will rise no higher; but remain in Equilibrio in the Air, at that Height.
CHAPTER LVII.
ON BAL LOONS. THEIR DEFECTS AND FARTHER IMPROVEMENTS.
Section 303. These Defects are best known from the History: a Detail of which is given to the World in an entertaining, elegant, and scientific Manner, by a celebrated Writer on other Subjects, Mons. Faujas de Saint Fond, in two Volumes, 12mo. for the two last Years, illustrated with Engravings by the best Masters.
And he promises a Continuation, or annual Register of Experiments and Improvements.
The Title of the Book is, “Description des Experiences de la Machine aërostatique, &c. &c.”