“All Wind acting on the Sails of a Vessel, tends to depress or sink it. Wherefore in strong Gales, they first haul down the Yards, and take in the Topsails: afterwards all the Sails: cut away the Masts: throw the Lading overboard, the Guns, &c. to lighten the Vessel, and keep her above Water.”[73]
CHAPTER XXXXIX.
Torrents of Air on Etna, and Teneriffe.
Section 265. WITH Respect to Mountains: on reading what Travellers have written, particularly Ullòa;[74] they seem to answer the Intention of supplying cool Air to the surrounding Plains, or Continents; by Depression and Condensation: and also, if on Islands; to the Sea itself.
266. Brydone, in his Tour throu’ Sicily and Malta, in 1773;[75] giving an Account of his Ascent to the Top of Etna, says, that at the Foot of the Crater, the Snow was frozen hard and solid:[76] and that the Crater was so hot; it was impossible to descend into it.
Further: “that the Smoke rolled down from the Sides, like a Torrent: till of equal Gravity with the Air, when it shot off horizontally; forming a long Track, according to the Direction of the Wind: which there rose to a violent Degree: so that it was with Difficulty he coud settle the Barometer for an Observation.”
He also adds “that Clouds began to gather round the Mountain; but were dispelled by the Wind.”
Now from the foregoing Theory is it not probable to suppose, that a Torrent of Air rushed continually down from the etherial Regions, not only to supply the Fire of the Crater; but also the Vacuity caused by the perpetual Elevation of Vapours and heated Air from below: the Torrent likewise depressing into the Track with itself, the Volumes of Smoke which were seen to roll directly down the Sides of the Mountain: that this descending Torrent of Air, in its Progress, dispelled the Clouds forming round the Sides of the Mountain, by the Ascent of warm Vapours condensing, as they rose, on their Approach to the cold Mountain: the Smoke shooting horizontally, from that Height only, at which an horizontal Current of Air began to take Place? For it can hardly be imagined that the Air at the Top of Etna, found to be “electrical,” and which must have been replete with a Mixture of Floguiston, inflammable Air, Gasses, and other aërial Fluids highly rarefied, heated, dry, (and consequently lighter,) at the Instant of rising out of the glowing Cauldron, became so condensed as to fall like Water, without partaking of the Motion of a violent Wind, supposed to blow in an horizontal Direction.
267. Glas, in his Account of Teneriffe,[77] reports, that the Clouds are generally half as high as the Peak, above the Sea,[78] i. e. according to him, near the Height of a Mile and Half: “below which Clouds, the North Easterly Winds generally prevail: and, at the same Time, above them, we find a fresh Westerly Gale: which I believe to be the Case in every Part of the World when the trade wind blows.”