But the strongest, and, at the same Time, an irrefragable Proof, is by Appeal to Men of Science in the Navy, or to skilful Pilots, who are conversant with Winds and Waves; who have weathered Storms off Cape Hatteras in Latitude 36; (where probably the Wind is perpetual;) or have made an East-India Voyage:—whether, if a Gale blew in an horizontal Direction only; the Ocean coud produce such an Inequality of Surface: or whether when the Sea runs mountains high; the tremendous Surges must not arise from the violent Action of Winds repeated at Intervals, sometimes descending perpendicularly; but oftener in forcible elastic Torrents of oblique depression, and instant Resilition?
CHAPTER XXXXV.
A gentle Depression of Air over moist Places in fair Weather.
Section 243.INtimations of depressing Columns in moderate Weather, are the sluggish Clouds, which often make their first Appearance, and remain longest, nay almost continually, over and along great Rivers, and Chains of Mountains, both during a Calm, or from whatever Point the Wind blows.
And hence the greater Quantity, Violence, and Continuance of Wind and Rain, which then descend:[60] also of the greater Purity of the Air during such Descent.
244. As, therefore, it is plain that atmospheric Air descends frequently, both in bad and fine Weather; if a Cause can be assigned so general, as to make it probable, that such depression does almost continually take Place:—tho’ at present the Effect is only evident to the Senses, by actual Experiment in the Passage of Balloons throu’ such Columns;—it will be sufficient to put Balloonists on their Guard against the Effects of such Depression.
245. In order to investigate the Theory of Depression; it may not be unacceptable, particularly to those who have not had Leisure to peruse the Experiments on Air, by Dr. Priestley, or the Collection on the same Subject by Cavallo;—just to extract a few short Quotations, on the chemical Affinities of Air and Water.
246. Article 1. “Water, as Rain, imbibes only the pure Air of the upper Regions, leaving the lighter and floguisticated Air to ascend.”[61]
246. 2. Felìcè Fontana says, “Common Air receives an Encrease of Bulk and Elasticity from being shaken in Water.”[62]