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] 246. 3. Air absorbs Water, and Water absorbs Air:[63] and the Absorption of Air by Water is promoted by Agitation: it also absorbs twice as much _defloguisticated_ Air, as common Air:[64] the whole Bulk of the Air absorbed being equal to one-twelfth of the Bulk of the Water: yet the Bulk of the Water seems but _little_ encreased: the Air being contained within the Interstices of the Water. 247. The following is a pretty and an easy Experiment, to shew how the +absorption of water by air+ takes Place, under the immediate Inspection of the Observer. Admitting the Sun’s Light into a Room, throu’ one Window only; pour a Pint of _boiling_ Water into a large Bason: hold the Bason, which will not be half full, next the Light, in such a Manner, that the Sun may shine on the Water and Bason; yet the Eyes be shaded by the Top of the Window Frame. Incline the Side of the Bason towards the Light, so that the Water may rise even with the Top. The Eye being placed just above the upper Side of the Bason, farthest from the Light; look on the Water.