Here then a nocturnal Depression of the Atmosphere is obvious. But this Appearance will not prove that the Air does not descend below the Level of the Clouds: for, tho’ the Clouds descend with the Air; Vapour-Air, of which they are composed, becomes _transparent_ both by Dissolution, in a warmer Stratum, and Proximity to the Earth, as before mentioned. [Sidenote: Conclusion drawn from the above, applicable to Balloons.] 268. From the Variety of Winds experienced at different Heights, not only on _Teneriffe_, but in different Places; it is plain, that if Balloons can be made durable and Air-tight; they may be wasted between the Tropics by an East or West Current at Pleasure: and also throu’out the Globe; the Occasion being made, in some Respect, subservient to the Time.[79] CHAPTER L. CORROBORATING PROOFS OF A DEPRESSION. Sect. 268. Art. 1. The Author is well informed, that, during an Engagement at Sea;—in _ten_ Minutes after the Action has commenced;—tho’ it blew a _Gale_ before; (that is, tho’ it blew _violently_;) the Agitation of the Air, arising from the Explosion of the _great Guns_, and small Arms, woud counteract the Wind, and produce a dead Calm. 268. 2. Quere: does not the _new elastic_ Air, produced from the Nitre,[80] give an instantaneous Compression and Dilatation to the _incumbent_ atmospheric Air, round the Place of Action, while the _lighter floguisticated Air_ passes throu’ it, raising, and affecting to its highest Limit, the _whole_ Atmosphere. And does not the Effect of a sudden Calm, suppose the Wind to _descend from above_ with a Kind of _saltatory_ Motion, instantly counteracted by the _new elastic_ Air?—For if the Wind be supposed to blow sideways or horizontally, _to any considerable Height above_ the Water, woud not the fresh _lateral_ Air glide away, and prevent the Continuance of the Calm? 269. When a Squall happens, or only Rain falls; Air will _rush_ from all Sides, and from _above_, to supply the Vacancy of the fallen Cloud and Vapour. The Air immediately _above_ must fall: the lateral Air gravitating towards other Places. Hence _Cold_, and a bright Sky after Rain. 270. The Theory of Accumulation may account for the frequent _warm_ Rains in Winter, and during the Night. For the preceding diurnal Accumulation over the Sea, may _circulate_ during the Night, at a great Altitude, to restore the Equilibrium and Loss of _cold_ Land Air sent by a low or Ground-Wind to Sea, during the Day-Time: particularly, as the _Accumulation_ over the Sea, during Winter, is almost _continual_.