But if it be considered that such Air, acting as a +wedge+, or more probably in the Form of an hyperbòlic Solid,[68] to fill up the Vacuity, descends with Rapidity from a _colder_ Atmosphere impregnated with aqueous Vapours _invisible from below_; and that both the Air and Vapour have reciprocal Affinities and Attractions, electric and mechanical, with the Body of Water beneath them; and are often rendered still cooler by its constant Agitation and _Evaporation_; also, that the Supply being immediate and cotemporary, with the +double tide of air+ flowing from the _middle_ over the _opposite_ Shores;—there possibly may be little or no Difference between the aggregate or _barometric_ Gravity of _such_ Columns, and those which are formed by the Sea-Breeze on either Side of them: therefore the Descent of Balloons is owing, among other Causes, to an almost perpendicular actual Depression of the superincumbent Atmosphere.[69] Following up the Idea of a Sea-Breeze, blowing, at a Medium, for 20 Miles over Land; altho’ the Stratum of the +lower current+ of Air, or Sea Breeze, may not exceed +half a mile in depth+, measuring from the Ground upwards; nearly equal to 26 Inches of the Barometer _above_, the Thermometer also _above_ being at 55, i.e. _Temperate_:—yet this Observation may prove of essential Service, while the +upper current+ of Air, i.e. the general Wind blows +towards+ the Sea, (which will be found to take Place more _frequently_ than is, at present, imagined;) or while the Balloon is influenced that Way; as was the Case with Sadler and his Companion when over the Nore: who, on his accidental and sudden Descent, fortunately found Safety in the +sea-breeze+. Which Breeze was sought for, and made Use of by the Author, when in the Balloon, near Frodsham, in Cheshire. For, as the Sea-Breeze is pretty general, Aironauts shoud not be too apprehensive: as they have it in their Power, by proper Management, to drop into the Breeze—for +either shore+: if they are provided with a Machinery to waft themselves across the intermediate _depressing_ or _accumulating_ +mediocèanal column of air+: which Space, between the two Shores, is, as before hinted, frequently +becalmed+. 258. Further: as the above Theory of a _mediocèanal_ Depression seems to receive additional Confirmation from _each_ Balloon Experiment; Lunardi _descending_ on the 5th of October last, when near the Middle of the Bay of Edinburgh or Firth of Forth;—it may be found _prudent_, to keep the Balloon continually rising, till the Aironaut is _one-third_ of the Passage _over_.