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_.

271. The _Wind_ would more frequently be perceived to _descend_ and _rebound upwards_, (Trials of which might be made by holding an Umbrella, extended at right Angles with its Axis, upright in the Hand;) if the same Opportunity offered, of opposing as great a Surface to it in a perpendicular, as is every Day done, in an horizontal Direction: for in walking, the whole Height of the Body, and half its Surface, is opposed horizontally to the Wind: but the Head only, which is covered, is opposed to the perpendicular Pressure.

272. As every Circumstance in the Order of Nature is so admirably contrived that each apparent Inconvenience rectifies itself; in _heavy_ Winds continuing to blow from a +cold+ Point; the Construction of the Atmosphere is such, that the _warm light_ Air from the opposite Points will necessarily rise up and flow over the cold Stratum, and by their Tendency to an Equilibrium, will produce an Air _less cold_, before the _same_ Wind is exhausted.

273. On the one Hand; it is probable, that, as cold Winds are heavy; the Eknèfiai Winds are covered with frequent Waves of the Apogay, or light warm Air rolling over them, frequently from the opposite Points.

274. On the other Hand, as the _Apogay_ Winds are naturally light and warm, it is _improbable_ that they shoud be _frequently_ covered with Waves of _cold heavy Air_, rolling over them from Eknèfiai Points.

It may therefore be reasonably concluded, that the Eknèfiai Winds, when approaching or opposed to the Apogay, shoud be considered as _Ground Winds_, (i.e. Winds blowing next the Surface of the Earth, tho’ they be supposed at the same Time to descend) which receive the Apogay above them: and that the Apogay being warm light and +moist+, (which last will have the same Effect, as if they were more elastic;)[81] being also more turbulent, and endued with greater Velocity, press back the Eknèfiai from the Surface of the Earth, and upwards; and at the same Time flow above them.

By which means the Eknèfiai partake of their Qualities;—become less _cold_, less _heavy_, and less _dry_.[82]