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. CHAPTER LIIII. ANOTHER METHOD OF SUSTAINING A BALLOON OVER WATER, WITHOUT LOSS OF GASS, OR OF BALLAST. Section 295. Let the Ballast consist of that Kind of Rope (wound on a Reel) that is either by Nature or Art, _specifically_ lighter than fresh Water: as a _hollow cylindrical_ Rope of Silk, in which Corks are thrust: the Silk to be dipped into elastic Varnish, to prevent the Absorption of Water into the Pores: or a common Rope well varnished; or covered over with a cylindric Case of varnished Silk, might answer the same Intention, if Corks or Bladders were tyed at proper Distances: in which Case, the Rope might, at the first Ascent of the Balloon, hang from the Center above the Car, at its full Extent, suppose a Mile or a Mile and half in Length, without the Encumbrance of a Reel. If Bladders are used; those that hang near the Car shoud not be more than _half blown_. By the above Expedient; as soon as the Balloon began to decline, from Evaporation of Gass, or Depression of the Atmosphere, and the lowest Part of the Rope touched the Water; the Balloon woud continue to levitate, in Proportion to the Quantity of Rope sustained on the Surface of the Water. The Aironaut woud move less _swift_ indeed, but more conveniently; as he woud not be obliged to rise _above_ the Wind: but be able to _lower_, and _raise_ himself at Pleasure: _first_, by pulling up a Part of the Rope into the Car; and having there _made it fast_; _Secondly_, by cutting away, as he saw Occasion, the loose End, and Folds of the Rope so drawn into the Car with him. CHAPTER LV. ON THE NECESSITY OF ASCERTAINING THE PROPER MODES OF DIRECTION, BY DIFFERENT AND FREQUENT EXPERIMENTS. [Sidenote: On the Necessity of frequent Experiments, in different Modes of Direction.]