CHAPTER LIII.

ON THE MEANS OF SUSTAINING A BALLOON ABOVE THE SURFACE OF THE WATER, BY A TEMPORARY LOSS OF BALLAST: AND OF RECOVERING THE BALLAST.

Sect. 294. Art. 1. The two Inconveniencies arising from a _Discharge_ of Ballast, while the Balloon is under the _Pressure_ of a mediocèanal Column of Air, are,

1. First, lest the Balloon shoud rise too _high_; for by opening the Valve in order to descend; Gass escapes: which is an _actual Loss_: and the Balloon is rendered incapable of supporting its Burden at the same Height, as before.

2. The present Impossibility of resuming the Ballast, in order to _descend_, or _check the Elevation_, on approaching either Shore, or at any other Time.

294. 2. These Inconveniencies are to be remedied by the following Methods.

If _Sand_ be the Ballast fixed on; put as much of it into a Bladder by Means of a Tin Funnel, as, when _less_ than _half_ blown, it will contain, without sinking below the Surface of +fresh+ _Water_.

_Prepare_ the intended Weight of Ballast, in Bladders, after the same Manner.

Also to +each+ Bladder _with Ballast_, tye another Bladder _without Ballast_, half blown.

Tye fast each Set of Bladders, so prepared, with a _leathern_ Thong; the Ends of which may be left a few Inches to _spare_.

The Grapple may remain in the Car.

294. 3. When the Balloon _begins_ to descend over Water; lower out the Cable, by Degrees.

Tye a Pair of Bladders, one of which contains Ballast, very tight, round the End of the Cable.

Then a second Pair, at such a Distance that the intermediate Part of the Cable, will _float_.

Repeat this Process, till the proper Effect is obtained; or the whole Ballast is discharged.

294. 4. The Car and Balloon may be _hauled_ or wound _down_ to the Surface of the Water: and the Ballast resumed, as the Balloon approaches the Shore.

294. 5. If it be found necessary, the Ballast may be _discharged_ by cutting the +thongs+, _gradually_: or the +cable+, _at once_.

294. 6. If the Wind be _contrary_, and the Weather _moderate_; the Tide, or Stream may, by _Calculation_ and _Foresight_, be made to serve the Purpose of the Aironaut, in towing the Ballast which floats on its Surface: and thus checking, or gently drawing the Balloon after it.

294. 7. In such Cases, the Aironaut woud do well in applying his _propulsive_ Machinery.

A GENERAL OBSERVATION.

294. 8. To prevent the car of the _Balloon_ from being drawn out of the Perpendicular, a Circumstance not infrequent; it is necessary to have some Contrivance, by which the Cable shall run throu’ a moveable Pulley, on a Swivel, in the Center above the Car; and that the Aironaut shall be able _instantly_, by a Screw, or otherways, to fasten the Pulley and Cable so tight, that the Stress shall remain on the Center above the Car, however _forcibly_ the Cable may be stretched.